man-page

The

policy plugin determines a user's

privileges. It is the default

policy plugin. The policy is driven by the

file or, optionally, in LDAP. The policy format is described in detail in the

section. For information on storing

policy information in LDAP, please see

consults the

file to determine which plugins to load. If no

file is present, or if it contains no

lines,

will be used for auditing, policy decisions and I/O logging. To explicitly configure

to use the

plugin, the following configuration can be used.

Plugin sudoers_audit sudoers.so Plugin sudoers_policy sudoers.so Plugin sudoers_io sudoers.so

Starting with

1.8.5, it is possible to specify optional arguments to the

plugin in the

file. Plugin arguments, if any, should be listed after the path to the plugin (i.e., after

The arguments are only effective for the plugin that opens (and parses) the

file.

For

version 1.9.1 and higher, this is the

plugin. For older versions, it is the

plugin. Multiple arguments may be specified, separated by white space. For example:

Plugin sudoers_audit sudoers.so sudoers_mode=0400 error_recovery=false

The following plugin arguments are supported:

The

argument can be used to control whether

should attempt to recover from syntax errors in the

file. If set to

(the default),

will try to recover from a syntax error by discarding the portion of the line that contains the error until the end of the line. A value of

will disable error recovery. Prior to version 1.9.3, no error recovery was performed.

The

argument can be used to override the default path to the

file.

The

argument can be used to override the default path to the

file.

The

argument can be used to override the default path to the

file.

The

argument can be used to override the default owner of the sudoers file. It should be specified as a numeric user-ID.

The

argument can be used to override the default group of the sudoers file. It must be specified as a numeric group-ID (not a group name).

The

argument can be used to override the default file mode for the sudoers file. It should be specified as an octal value.

For more information on configuring

please refer to its manual.

The

security policy requires that most users authenticate themselves before they can use

A password is not required if the invoking user is root, if the target user is the same as the invoking user, or if the policy has disabled authentication for the user or command. Unlike

when

requires authentication, it validates the invoking user's credentials, not the target user's (or root's) credentials. This can be changed via the

and

flags, described later.

If a user who is not listed in the policy tries to run a command via

mail is sent to the proper authorities. The address used for such mail is configurable via the

Defaults entry (described later) and defaults to

Note that no mail will be sent if an unauthorized user tries to run

with the

option unless there is an authentication error and either the

flags are enabled. This allows users to determine for themselves whether or not they are allowed to use

By default, all attempts to run

(successful or not) are logged, regardless of whether or not mail is sent.

is run by root and the

environment variable is set, the

policy will use this value to determine who the actual user is. This can be used by a user to log commands through sudo even when a root shell has been invoked. It also allows the

option to remain useful even when invoked via a sudo-run script or program. Note, however, that the

file lookup is still done for root, not the user specified by

uses per-user time stamp files for credential caching. Once a user has been authenticated, a record is written containing the user-ID that was used to authenticate, the terminal session ID, the start time of the session leader (or parent process) and a time stamp (using a monotonic clock if one is available). The user may then use

without a password for a short period of time

minutes unless overridden by the

option

By default,

uses a separate record for each terminal, which means that a user's login sessions are authenticated separately. The

option can be used to select the type of time stamp record

will use.

By default,

logs both successful and unsuccessful attempts (as well as errors). The

and

flags can be used to control this behavior. Messages can be logged to

a log file, or both. The default is to log to

but this is configurable via the

and

settings. See

for a description of the log file format.

is also capable of running a command in a pseudo-terminal and logging all input and/or output. The standard input, standard output, and standard error can be logged even when not associated with a terminal. I/O logging is not on by default but can be enabled using the

and

options as well as the

and

command tags. See

for details on how I/O log files are stored.

Starting with version 1.9, the

setting may be used to send event and I/O log data to a remote server running

or another service that implements the protocol described by

Since environment variables can influence program behavior,

provides a means to restrict which variables from the user's environment are inherited by the command to be run. There are two distinct ways

can deal with environment variables.

By default, the

flag is enabled. This causes commands to be executed with a new, minimal environment. On AIX (and Linux systems without PAM), the environment is initialized with the contents of the

file.

The

and

environment variables are initialized based on the target user and the

variables are set based on the invoking user. Additional variables, such as

and

are preserved from the invoking user's environment if permitted by the

options. A few environment variables are treated specially. If the

and

variables are not preserved from the user's environment, they will be set to default values. The

and

are handled as a single entity. If one of them is preserved (or removed) from the user's environment, the other will be as well. If

and

are to be preserved but only one of them is present in the user's environment, the other will be set to the same value. This avoids an inconsistent environment where one of the variables describing the user name is set to the invoking user and one is set to the target user. Environment variables with a value beginning with

are removed unless both the name and value parts are matched by

as they may be interpreted as functions by the

shell. Prior to version 1.8.11, such variables were always removed.

If, however, the

flag is disabled, any variables not explicitly denied by the

and

options are allowed and their values are inherited from the invoking process. Prior to version 1.8.21, environment variables with a value beginning with

were always removed. Beginning with version 1.8.21, a pattern in

is used to match

shell functions instead. Since it is not possible to block all potentially dangerous environment variables, use of the default

behavior is encouraged.

Environment variables specified by

may include one or more

characters which will match zero or more characters. No other wildcard characters are supported.

By default, environment variables are matched by name. However, if the pattern includes an equal sign

both the variables name and value must match. For example, a

shell function could be matched as follows:

env_keep += "BASH_FUNC_my_func%%=()*"

Without the

suffix, this would not match, as

shell functions are not preserved by default.

The complete list of environment variables that are preserved or removed, as modified by global Defaults parameters in

is displayed when

is run by root with the

option. Please note that the list of environment variables to remove varies based on the operating system

is running on.

Other

options may influence the command environment, such as

and

On systems that support PAM where the

module is enabled for

variables in the PAM environment may be merged in to the environment. If a variable in the PAM environment is already present in the user's environment, the value will only be overridden if the variable was not preserved by

When

is enabled, variables preserved from the invoking user's environment by the

list take precedence over those in the PAM environment. When

is disabled, variables present the invoking user's environment take precedence over those in the PAM environment unless they match a pattern in the

list.

Note that the dynamic linker on most operating systems will remove variables that can control dynamic linking from the environment of set-user-ID executables, including

Depending on the operating system this may include

and others. These type of variables are removed from the environment before

even begins execution and, as such, it is not possible for

to preserve them.

As a special case, if the

option (initial login) is specified,

will initialize the environment regardless of the value of

The

and

variables remain unchanged;

and

are set based on the target user. On AIX (and Linux systems without PAM), the contents of

are also included.

All other environment variables are removed unless permitted by

described above.

Finally, the

and

files are applied, if present. The variables in

are applied first and are subject to the same restrictions as the invoking user's environment, as detailed above. The variables in

are applied last and are not subject to these restrictions. In both cases, variables present in the files will only be set to their specified values if they would not conflict with an existing environment variable.

The

file is composed of two types of entries: aliases (basically variables) and user specifications (which specify who may run what).

When multiple entries match for a user, they are applied in order. Where there are multiple matches, the last match is used (which is not necessarily the most specific match).

The

file grammar will be described below in Extended Backus-Naur Form (EBNF). Don't despair if you are unfamiliar with EBNF; it is fairly simple, and the definitions below are annotated.

By default,

uses the operating system's native method of setting resource limits for the target user. On Linux systems, resource limits are usually set by the

PAM module. On some BSD systems, the

file specifies resource limits for the user. On AIX systems, resource limits are configured in the

file. If there is no system mechanism to set per-user resource limits, the command will run with the same limits as the invoking user. The one exception to this is the core dump file size, which is set by

to 0 by default. Disabling core dumps by default makes it possible to avoid potential security problems where the core file is treated as trusted input.

Resource limits may also be set in the

file itself, in which case they override those set by the system. See the

options described below. Resource limits in

may be specified in one of the following formats:

Both the soft and hard resource limits are set to the same value. The special value

can be used to indicate that the value is unlimited.

Two comma-separated values. The soft limit is set to the first value and the hard limit is set to the second. Both values must either be enclosed in a set of double quotes, or the comma must be escaped with a backslash

The special value

may be used in place of either value.

The default resource limit for the user will be used. This may be a user-specific value (see above) or the value of the resource limit when

was invoked for systems that don't support per-user limits.

The invoking user's resource limits will be preserved when running the command.

For example, to restore the historic core dump file size behavior, a line like the following may be used.

Resource limits in

are only supported by version 1.8.7 or higher.

EBNF is a concise and exact way of describing the grammar of a language. Each EBNF definition is made up of

E.g.,

Each

references others and thus makes up a grammar for the language. EBNF also contains the following operators, which many readers will recognize from regular expressions. Do not, however, confuse them with

characters, which have different meanings.

Means that the preceding symbol (or group of symbols) is optional. That is, it may appear once or not at all.

Means that the preceding symbol (or group of symbols) may appear zero or more times.

Means that the preceding symbol (or group of symbols) may appear one or more times.

Parentheses may be used to group symbols together. For clarity, we will use single quotes

to designate what is a verbatim character string (as opposed to a symbol name).

There are four kinds of aliases:

and

Beginning with

1.9.0,

may be used in place of

if desired.

Alias ::= 'User_Alias' User_Alias_Spec (':' User_Alias_Spec)* | 'Runas_Alias' Runas_Alias_Spec (':' Runas_Alias_Spec)* | 'Host_Alias' Host_Alias_Spec (':' Host_Alias_Spec)* | 'Cmnd_Alias' Cmnd_Alias_Spec (':' Cmnd_Alias_Spec)* | 'Cmd_Alias' Cmnd_Alias_Spec (':' Cmnd_Alias_Spec)*

User_Alias ::= NAME

User_Alias_Spec ::= User_Alias '=' User_List

Runas_Alias ::= NAME

Runas_Alias_Spec ::= Runas_Alias '=' Runas_List

Host_Alias ::= NAME

Host_Alias_Spec ::= Host_Alias '=' Host_List

Cmnd_Alias ::= NAME

Cmnd_Alias_Spec ::= Cmnd_Alias '=' Cmnd_List

NAME ::= [A-Z]([A-Z][0-9]_)*

Each

definition is of the form

Alias_Type NAME = item1, item2, ...

where

is one of

is a string of uppercase letters, numbers, and underscore characters

start with an uppercase letter. It is possible to put several alias definitions of the same type on a single line, joined by a colon

E.g.,

Alias_Type NAME = item1, item2, item3 : NAME = item4, item5

It is a syntax error to redefine an existing

It is possible to use the same name for

of different types, but this is not recommended.

The definitions of what constitutes a valid

member follow.

User_List ::= User | User ',' User_List

is made up of one or more user names, user-IDs (prefixed with

system group names and IDs (prefixed with

and

respectively), netgroups (prefixed with

non-Unix group names and IDs (prefixed with

and

respectively), and

Each list item may be prefixed with zero or more

operators. An odd number of

operators negate the value of the item; an even number just cancel each other out. User netgroups are matched using the user and domain members only; the host member is not used when matching.

may be enclosed in double quotes to avoid the need for escaping special characters. Alternately, special characters may be specified in escaped hex mode, e.g., \x20 for space. When using double quotes, any prefix characters must be included inside the quotes.

The actual

and

syntax depends on the underlying group provider plugin. For instance, the QAS AD plugin supports the following formats:

Group in the same domain: "%:Group Name"

Group in any domain: "%:Group Name@FULLY.QUALIFIED.DOMAIN"

Group SID: "%:S-1-2-34-5678901234-5678901234-5678901234-567"

See

for more information.

Note that quotes around group names are optional. Unquoted strings must use a backslash

to escape spaces and special characters. See

for a list of characters that need to be escaped.

Runas_List ::= Runas_Member | Runas_Member ',' Runas_List

is similar to a

except that instead of

it can contain

Note that user names and groups are matched as strings. In other words, two users (groups) with the same user (group) ID are considered to be distinct. If you wish to match all user names with the same user-ID (e.g., root and toor), you can use a user-ID instead of a name (#0 in the example given). Note that the user-ID or group-ID specified in a

need not be listed in the password or group database.

Host_List ::= Host | Host ',' Host_List

Host ::= '!'* host name | '!'* ip_addr | '!'* network(/netmask)? | '!'* +netgroup | '!'* Host_Alias

is made up of one or more host names, IP addresses, network numbers, netgroups (prefixed with

and other aliases. Again, the value of an item may be negated with the

operator. Host netgroups are matched using the host (both qualified and unqualified) and domain members only; the user member is not used when matching. If you specify a network number without a netmask,

will query each of the local host's network interfaces and, if the network number corresponds to one of the hosts's network interfaces, will use the netmask of that interface. The netmask may be specified either in standard IP address notation (e.g., 255.255.255.0 or ffff:ffff:ffff:ffff::), or CIDR notation (number of bits, e.g., 24 or 64). A host name may include shell-style wildcards (see the

section below), but unless the

command on your machine returns the fully qualified host name, you'll need to use the

flag for wildcards to be useful. Note that

only inspects actual network interfaces; this means that IP address 127.0.0.1 (localhost) will never match. Also, the host name

will only match if that is the actual host name, which is usually only the case for non-networked systems.

digest ::= [A-Fa-f0-9]+ | [A-Za-z0-9\+/=]+

Digest_Spec ::= "sha224" ':' digest | "sha256" ':' digest | "sha384" ':' digest | "sha512" ':' digest

Digest_List ::= Digest_Spec | Digest_Spec ',' Digest_List

Cmnd_List ::= Cmnd | Cmnd ',' Cmnd_List

command name ::= file name | file name args | file name '""'

Edit_Spec ::= "sudoedit" file name+

Cmnd ::= Digest_List? '!'* command name | '!'* directory | '!'* Edit_Spec | '!'* Cmnd_Alias

is a list of one or more command names, directories, and other aliases. A command name is a fully qualified file name which may include shell-style wildcards (see the

section below). A simple file name allows the user to run the command with any arguments they wish. However, you may also specify command line arguments (including wildcards). Alternately, you can specify

to indicate that the command may only be run

command line arguments. A directory is a fully qualified path name ending in a

When you specify a directory in a

the user will be able to run any file within that directory (but not in any sub-directories therein).

If a

has associated command line arguments, then the arguments in the

must match exactly those given by the user on the command line (or match the wildcards if there are any). Note that the following characters must be escaped with a

if they are used in command arguments:

The built-in command

is used to permit a user to run

with the

option (or as

It may take command line arguments just as a normal command does. Note that

is a command built into

itself and must be specified in the

file

a leading path. If a leading path is present, for example

the path name will be silently converted to

A fully-qualified path for

is treated as an error by

may be preceded by a

a comma-separated list of one or more

entries. If a

is present, the command will only match successfully if it can be verified using one of the SHA-2 digests in the list. Starting with version 1.9.0, the

reserved word can be used in conjunction with a

The following digest formats are supported: sha224, sha256, sha384, and sha512. The string may be specified in either hex or base64 format (base64 is more compact). There are several utilities capable of generating SHA-2 digests in hex format such as openssl, shasum, sha224sum, sha256sum, sha384sum, sha512sum.

For example, using openssl:

$ openssl dgst -sha224 /bin/ls SHA224(/bin/ls)= 118187da8364d490b4a7debbf483004e8f3e053ec954309de2c41a25

It is also possible to use openssl to generate base64 output:

$ openssl dgst -binary -sha224 /bin/ls | openssl base64 EYGH2oNk1JC0p9679IMATo8+BT7JVDCd4sQaJQ==

Warning, if the user has write access to the command itself (directly or via a

command), it may be possible for the user to replace the command after the digest check has been performed but before the command is executed. A similar race condition exists on systems that lack the

system call when the directory in which the command is located is writable by the user. See the description of the

setting for more information on how

executes commands that have an associated digest.

Command digests are only supported by version 1.8.7 or higher.

Certain configuration options may be changed from their default values at run-time via one or more

lines. These may affect all users on any host, all users on a specific host, a specific user, a specific command, or commands being run as a specific user. Note that per-command entries may not include command line arguments. If you need to specify arguments, define a

and reference that instead.

Default_Type ::= 'Defaults' | 'Defaults' '@' Host_List | 'Defaults' ':' User_List | 'Defaults' '!' Cmnd_List | 'Defaults' '>' Runas_List

Default_Entry ::= Default_Type Parameter_List

Parameter_List ::= Parameter | Parameter ',' Parameter_List

Parameter ::= Parameter '=' Value | Parameter '+=' Value | Parameter '-=' Value | '!'* Parameter

Parameters may be

values,

Flags are implicitly boolean and can be turned off via the

operator. Some integer, string and list parameters may also be used in a boolean context to disable them. Values may be enclosed in double quotes

when they contain multiple words. Special characters may be escaped with a backslash

To include a literal backslash character in a command line argument you must escape the backslash twice. For example, to match

as part of a command line argument, you must use

in the

file. This is due to there being two levels of escaping, one in the

parser itself and another when command line arguments are matched by the

function.

Lists have two additional assignment operators,

and

These operators are used to add to and delete from a list respectively. It is not an error to use the

operator to remove an element that does not exist in a list.

Defaults entries are parsed in the following order: generic, host, user, and runas Defaults first, then command defaults. If there are multiple Defaults settings of the same type, the last matching setting is used. The following Defaults settings are parsed before all others since they may affect subsequent entries:

See

for a list of supported Defaults parameters.

User_Spec ::= User_List Host_List '=' Cmnd_Spec_List \ (':' Host_List '=' Cmnd_Spec_List)*

Cmnd_Spec_List ::= Cmnd_Spec | Cmnd_Spec ',' Cmnd_Spec_List

Cmnd_Spec ::= Runas_Spec? Option_Spec* Tag_Spec* Cmnd

Runas_Spec ::= '(' Runas_List? (':' Runas_List)? ')'

Date_Spec ::= ('NOTBEFORE=timestamp' | 'NOTAFTER=timestamp')

Timeout_Spec ::= 'TIMEOUT=timeout'

Chdir_Spec ::= 'CWD=directory'

Chroot_Spec ::= 'CHROOT=directory'

determines which commands a user may run (and as what user) on specified hosts. By default, commands are run as

but this can be changed on a per-command basis.

The basic structure of a user specification is

Let's break that down into its constituent parts:

determines the user and/or the group that a command may be run as. A fully-specified

consists of two

(as defined above) separated by a colon

and enclosed in a set of parentheses. The first

indicates which users the command may be run as via the

option. The second defines a list of groups that may be specified via the

option (in addition to any of the target user's groups). If both

are specified, the command may be run with any combination of users and groups listed in their respective

If only the first is specified, the command may be run as any user in the list and, optionally, with any group the target user belongs to. If the first

is empty but the second is specified, the command may be run as the invoking user with the group set to any listed in the

If both

are empty, the command may only be run as the invoking user and the group, if specified, must be one that the invoking user is a member of. If no

is specified, the command may only be run as

and the group, if specified, must be one that

is a member of.

sets the default for the commands that follow it. What this means is that for the entry:

dgb boulder = (operator) /bin/ls, /bin/kill, /usr/bin/lprm

The user

may run

and

on the host

only as

E.g.,

$ sudo -u operator /bin/ls

It is also possible to override a

later on in an entry. If we modify the entry like so:

dgb boulder = (operator) /bin/ls, (root) /bin/kill, /usr/bin/lprm

Then user

is now allowed to run

but

and

We can extend this to allow

to run

with either the user or group set to

dgb boulder = (operator : operator) /bin/ls, (root) /bin/kill,\ /usr/bin/lprm

Note that while the group portion of the

permits the user to run as command with that group, it does not force the user to do so. If no group is specified on the command line, the command will run with the group listed in the target user's password database entry. The following would all be permitted by the sudoers entry above:

$ sudo -u operator /bin/ls $ sudo -u operator -g operator /bin/ls $ sudo -g operator /bin/ls

In the following example, user

may run commands that access a modem device file with the dialer group.

tcm boulder = (:dialer) /usr/bin/tip, /usr/bin/cu,\ /usr/local/bin/minicom

Note that in this example only the group will be set, the command still runs as user

E.g.

$ sudo -g dialer /usr/bin/cu

Multiple users and groups may be present in a

in which case the user may select any combination of users and groups via the

and

options. In this example:

alan ALL = (root, bin : operator, system) ALL

user

may run any command as either user root or bin, optionally setting the group to operator or system.

may have zero or more options associated with it. Options may consist of

start and/or end dates and command timeouts. Once an option is set for a

subsequent

in the

inherit that option unless it is overridden by another option. Note that the option names are reserved words in

This means that none of the valid option names (see below) can be used when declaring an alias.

rules can be specified with a start and end date via the

and

settings. The time stamp must be specified in

as defined by RFC 4517. The format is effectively

where the minutes and seconds are optional. The

suffix indicates that the time stamp is in Coordinated Universal Time (UTC). It is also possible to specify a timezone offset from UTC in hours and minutes instead of a

For example,

would correspond to Eastern Standard time in the US. As an extension, if no

or timezone offset is specified, local time will be used.

The following are all valid time stamps:

20170214083000Z 2017021408Z 20160315220000-0500 20151201235900

A command may have a timeout associated with it. If the timeout expires before the command has exited, the command will be terminated. The timeout may be specified in combinations of days, hours, minutes, and seconds with a single-letter case-insensitive suffix that indicates the unit of time. For example, a timeout of 7 days, 8 hours, 30 minutes, and 10 seconds would be written as

If a number is specified without a unit, seconds are assumed. Any of the days, minutes, hours, or seconds may be omitted. The order must be from largest to smallest unit and a unit may not be specified more than once.

The following are all

timeout values:

The following are

timeout values:

This setting is only supported by version 1.8.20 or higher.

The working directory that the command will be run in can be specified using the

setting. The

must be a fully-qualified path name beginning with a

character, or the special value

A value of

indicates that the user may specify the working directory by running

with the

option. By default, commands are run from the invoking user's current working directory, unless the

option is given. Path names of the form

are interpreted as being relative to the named user's home directory. If the user name is omitted, the path will be relative to the runas user's home directory.

This setting is only supported by version 1.9.3 or higher.

The root directory that the command will be run in can be specified using the

setting. The

must be a fully-qualified path name beginning with a

character, or the special value

A value of

indicates that the user may specify the root directory by running

with the

option. This setting can be used to run the command in a

similar to the

utility. Path names of the form

are interpreted as being relative to the named user's home directory. If the user name is omitted, the path will be relative to the runas user's home directory.

This setting is only supported by version 1.9.3 or higher.

A command may have zero or more tags associated with it. The following tag values are supported:

and

Once a tag is set on a

subsequent

in the

inherit the tag unless it is overridden by the opposite tag (in other words,

overrides

and

overrides

has been compiled with

support and the underlying operating system supports it, the

tag can be used to prevent a dynamically-linked executable from running further commands itself.

In the following example, user

may run

and

but shell escapes will be disabled.

aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi

See the

section below for more details on how

works and whether or not it will work on your system.

Starting with version 1.8.15,

will not open a file that is a symbolic link unless the

flag is enabled. The

and

tags override the value of

and can be used to permit (or deny) the editing of symbolic links on a per-command basis. These tags are only effective for the

command and are ignored for all other commands.

These tags override the value of the

flag on a per-command basis. For more information, see the description of

in the

section below.

These tags override the value of the

flag on a per-command basis. For more information, see the description of

in the

section below.

These tags provide fine-grained control over whether mail will be sent when a user runs a command by overriding the value of the

flag on a per-command basis. They have no effect when

is run with the

options. A

tag will also override the

and

options. For more information, see the descriptions of

and

in the

section below.

By default,

requires that a user authenticate before running a command. This behavior can be modified via the

tag. Like a

the

tag sets a default for the commands that follow it in the

Conversely, the

tag can be used to reverse things. For example:

ray rushmore = NOPASSWD: /bin/kill, /bin/ls, /usr/bin/lprm

would allow the user

to run

and

on the machine

without authenticating himself. If we only want

to be able to run

without a password the entry would be:

ray rushmore = NOPASSWD: /bin/kill, PASSWD: /bin/ls, /usr/bin/lprm

Note, however, that the

tag has no effect on users who are in the group specified by the

setting.

By default, if the

tag is applied to any of a user's entries for the current host, the user will be able to run

without a password. Additionally, a user may only run

without a password if all of the user's entries for the current host have the

tag. This behavior may be overridden via the

and

options.

These tags override the value of the

flag on a per-command basis. Note that if

has been set for a command, the user may disable the

flag from the command line via the

option. Additionally, environment variables set on the command line are not subject to the restrictions imposed by

As such, only trusted users should be allowed to set variables in this manner. If the command matched is

the

tag is implied for that command; this default may be overridden by use of the

tag.

has been compiled with

support and the underlying operating system supports it, the

tag can be used to cause programs spawned by a command to be validated against

and logged just like they would be if run through

directly. This is useful in conjunction with commands that allow shell escapes such as editors, shells, and paginators.

In the following example, user

may run any command on the machine

in intercept mode.

chuck research = INTERCEPT: ALL

See the

section below for more details on how

works and whether or not it will work on your system.

allows shell-style

(aka meta or glob characters) to be used in host names, path names, and command line arguments in the

file. Wildcard matching is done via the

and

functions as specified by

Matches any set of zero or more characters (including white space).

Matches any single character (including white space).

Matches any character in the specified range.

Matches any character

in the specified range.

For any character

evaluates to

This is used to escape special characters such as:

and

Note that these are not regular expressions.

Unlike a regular expression there is no way to match one or more characters within a range.

Character classes may be used if your system's

and

functions support them. However, because the

character has special meaning in

it must be escaped. For example:

/bin/ls [[\:alpha\:]]*

Would match any file name beginning with a letter.

Note that a forward slash

will

be matched by wildcards used in the file name portion of the command. This is to make a path like:

/usr/bin/*

match

but not

When matching the command line arguments, however, a slash

get matched by wildcards since command line arguments may contain arbitrary strings and not just path names.

Wildcards in command line arguments should be used with care.

Command line arguments are matched as a single, concatenated string. This mean a wildcard character such as

will match across word boundaries, which may be unexpected. For example, while a sudoers entry like:

%operator ALL = /bin/cat /var/log/messages*

will allow command like:

$ sudo cat /var/log/messages.1

It will also allow:

$ sudo cat /var/log/messages /etc/shadow

which is probably not what was intended. In most cases it is better to do command line processing outside of the

file in a scripting language.

The following exceptions apply to the above rules:

If the empty string

is the only command line argument in the

file entry it means that command is not allowed to be run with

arguments.

Command line arguments to the

built-in command should always be path names, so a forward slash

will not be matched by a wildcard.

It is possible to include other

files from within the

file currently being parsed using the

and

directives. For compatibility with sudo versions prior to 1.9.1,

and

are also accepted.

An include file can be used, for example, to keep a site-wide

file in addition to a local, per-machine file. For the sake of this example the site-wide

file will be

and the per-machine one will be

To include

from within

one would use the following line in

@include /etc/sudoers.local

When

reaches this line it will suspend processing of the current file

and switch to

Upon reaching the end of

the rest of

will be processed. Files that are included may themselves include other files. A hard limit of 128 nested include files is enforced to prevent include file loops.

Starting with version 1.9.1, the path to the include file may contain white space if it is escaped with a backslash

Alternately, the entire path may be enclosed in double quotes

in which case no escaping is necessary. To include a literal backslash in the path,

should be used.

If the path to the include file is not fully-qualified (does not begin with a

it must be located in the same directory as the sudoers file it was included from. For example, if

contains the line:

the file that will be included is

The file name may also include the

escape, signifying the short form of the host name. In other words, if the machine's host name is

then

@include /etc/sudoers.%h

will cause

to include the file

The

directive can be used to create a

directory that the system package manager can drop

file rules into as part of package installation. For example, given:

@includedir /etc/sudoers.d

will suspend processing of the current file and read each file in

skipping file names that end in

or contain a

character to avoid causing problems with package manager or editor temporary/backup files. Files are parsed in sorted lexical order. That is,

will be parsed before

Be aware that because the sorting is lexical, not numeric,

would be loaded

Using a consistent number of leading zeroes in the file names can be used to avoid such problems. After parsing the files in the directory, control returns to the file that contained the

directive.

Note that unlike files included via

will not edit the files in a

directory unless one of them contains a syntax error. It is still possible to run

with the

flag to edit the files directly, but this will not catch the redefinition of an

that is also present in a different file.

The pound sign

is used to indicate a comment (unless it is part of a #include directive or unless it occurs in the context of a user name and is followed by one or more digits, in which case it is treated as a user-ID). Both the comment character and any text after it, up to the end of the line, are ignored.

The reserved word

is a built-in

that always causes a match to succeed. It can be used wherever one might otherwise use a

Attempting to define an

named

will result in a syntax error. Please note that using

can be dangerous since in a command context, it allows the user to run

command on the system.

The following option names permitted in an

are also considered reserved words:

and

Attempting to define an

with the same name as one of the options will result in a syntax error.

An exclamation point

can be used as a logical

operator in a list or

as well as in front of a

This allows one to exclude certain values. For the

operator to be effective, there must be something for it to exclude. For example, to match all users except for root one would use:

ALL,!root

If the

is omitted, as in:

!root

it would explicitly deny root but not match any other users. This is different from a true

operator.

Note, however, that using a

in conjunction with the built-in

alias to allow a user to run

commands rarely works as intended (see

below).

Long lines can be continued with a backslash

as the last character on the line.

White space between elements in a list as well as special syntactic characters in a

is optional.

The following characters must be escaped with a backslash

when used as part of a word (e.g., a user name or host name):

behavior can be modified by

lines, as explained earlier. A list of all supported Defaults parameters, grouped by type, are listed below.

If a

is configured, use it to resolve groups of the form %group as long as there is not also a system group of the same name. Normally, only groups of the form %:group are passed to the

This flag is

by default.

If enabled,

will set the

environment variable to the home directory of the target user (which is the root user unless the

option is used). This flag is largely obsolete and has no effect unless the

flag has been disabled or

is present in the

list, both of which are strongly discouraged. This flag is

by default.

If set, users must authenticate themselves via a password (or other means of authentication) before they may run commands. This default may be overridden via the

and

tags. This flag is

by default.

If enabled, group names in

will be matched in a case insensitive manner. This may be necessary when users are stored in LDAP or AD. This flag is

by default.

If enabled, user names in

will be matched in a case insensitive manner. This may be necessary when groups are stored in LDAP or AD. This flag is

by default.

If set, the user may use the

option which overrides the default starting point at which

begins closing open file descriptors. This flag is

by default.

If set, and

is configured to log a command's input or output, the I/O logs will be compressed using

This flag is

by default when

is compiled with

support.

By default,

runs a command as the foreground process as long as

itself is running in the foreground. When the

flag is enabled and the command is being run in a pseudo-terminal (due to I/O logging or the

flag), the command will be run as a background process. Attempts to read from the controlling terminal (or to change terminal settings) will result in the command being suspended with the

signal (or

in the case of terminal settings). If this happens when

is a foreground process, the command will be granted the controlling terminal and resumed in the foreground with no user intervention required. The advantage of initially running the command in the background is that

need not read from the terminal unless the command explicitly requests it. Otherwise, any terminal input must be passed to the command, whether it has required it or not (the kernel buffers terminals so it is not possible to tell whether the command really wants the input). This is different from historic

behavior or when the command is not being run in a pseudo-terminal.

For this to work seamlessly, the operating system must support the automatic restarting of system calls. Unfortunately, not all operating systems do this by default, and even those that do may have bugs. For example, macOS fails to restart the

and

system calls (this is a bug in macOS). Furthermore, because this behavior depends on the command stopping with the

signals, programs that catch these signals and suspend themselves with a different signal (usually

will not be automatically foregrounded. Some versions of the linux

command behave this way. This flag is

by default.

This setting is only supported by version 1.8.7 or higher. It has no effect unless I/O logging is enabled or the

flag is enabled.

If set,

will use the value of the

environment variables before falling back on the default editor list. Note that

is typically run as root so this flag may allow a user with

privileges to run arbitrary commands as root without logging. An alternative is to place a colon-separated list of

editors int the

setting.

will then only use

if they match a value specified in

If the

flag is enabled, the

and/or

environment variables must be present in the

list for the

flag to function when

is invoked via

This flag is

by default.

If set,

will run the command in a minimal environment containing the

and

variables. Any variables in the caller's environment or in the file specified by the

setting that match the

and

lists are then added, followed by any variables present in the file specified by the

setting (if any). The contents of the

and

lists, as modified by global Defaults parameters in

are displayed when

is run by root with the

option. If the

setting is enabled, its value will be used for the

environment variable. This flag is

by default.

Normally,

uses the

function to do shell-style globbing when matching path names. However, since it accesses the file system,

can take a long time to complete for some patterns, especially when the pattern references a network file system that is mounted on demand (auto mounted). The

flag causes

to use the

function, which does not access the file system to do its matching. The disadvantage of

is that it is unable to match relative path names such as

This has security implications when path names that include globbing characters are used with the negation operator,

as such rules can be trivially bypassed. As such, this flag should not be used when the

file contains rules that contain negated path names which include globbing characters. This flag is

by default.

Set this flag if you want to put fully qualified host names in the

file when the local host name (as returned by the

command) does not contain the domain name. In other words, instead of myhost you would use myhost.mydomain.edu. You may still use the short form if you wish (and even mix the two). This flag is only effective when the

host name, as returned by the

function, is a fully-qualified domain name. This is usually the case when the system is configured to use DNS for host name resolution.

If the system is configured to use the

file in preference to DNS, the

host name may not be fully-qualified. The order that sources are queried for host name resolution is usually specified in the

or, in some cases,

file. In the

file, the first host name of the entry is considered to be the

name; subsequent names are aliases that are not used by

For example, the following hosts file line for the machine

has the fully-qualified domain name as the

host name, and the short version as an alias.

If the machine's hosts file entry is not formatted properly, the

flag will not be effective if it is queried before DNS.

Beware that when using DNS for host name resolution, turning on

requires

to make DNS lookups which renders

unusable if DNS stops working (for example if the machine is disconnected from the network). Also note that just like with the hosts file, you must use the

name as DNS knows it. That is, you may not use a host alias

entry

due to performance issues and the fact that there is no way to get all aliases from DNS.

This flag is

by default.

Allow commands to be run even if

cannot write to the audit log. If enabled, an audit log write failure is not treated as a fatal error. If disabled, a command may only be run after the audit event is successfully written. This flag is only effective on systems for which

supports audit logging, including

Linux, macOS, and Solaris. This flag is

by default.

If set,

will ignore "." or "" (both denoting current directory) in the

environment variable; the

itself is not modified. This flag is

by default.

Allow commands to be run even if

cannot write to the I/O log (local or remote). If enabled, an I/O log write failure is not treated as a fatal error. If disabled, the command will be terminated if the I/O log cannot be written to. This flag is

by default.

Allow commands to be run even if

cannot write to the log file. If enabled, a log file write failure is not treated as a fatal error. If disabled, a command may only be run after the log file entry is successfully written. This flag only has an effect when

is configured to use file-based logging via the

setting. This flag is

by default.

If set via LDAP, parsing of

will be skipped. This is intended for Enterprises that wish to prevent the usage of local sudoers files so that only LDAP is used. This thwarts the efforts of rogue operators who would attempt to add roles to

When this flag is enabled,

does not even need to exist. Since this flag tells

how to behave when no specific LDAP entries have been matched, this sudoOption is only meaningful for the

section. This flag is

by default.

If set,

will not produce a warning if it encounters an unknown Defaults entry in the

file or an unknown sudoOption in LDAP. This flag is

by default.

If set,

will insult users when they enter an incorrect password. This flag is

by default.

If set,

will log commands allowed by the policy to the system audit log (where supported) as well as to syslog and/or a log file. This flag is

by default.

This setting is only supported by version 1.8.29 or higher.

If set,

will log commands denied by the policy to the system audit log (where supported) as well as to syslog and/or a log file. This flag is

by default.

This setting is only supported by version 1.8.29 or higher.

If set,

will log the exit value of commands that are run to syslog and/or a log file. If a command was terminated by a signal, the signal name is logged as well. This flag is

by default.

This setting is only supported by version 1.9.8 or higher.

If set, the host name will be included in log entries written to the file configured by the

setting. This flag is

by default.

If set,

will run the command in a pseudo-terminal and log all user input. If the standard input is not connected to the user's tty, due to I/O redirection or because the command is part of a pipeline, that input is also captured and stored in a separate log file. Anything sent to the standard input will be consumed, regardless of whether or not the command run via

is actually reading the standard input. This may have unexpected results when using

in a shell script that expects to process the standard input. For more information about I/O logging, see the

section. This flag is

by default.

If set,

will run the command in a pseudo-terminal and log all output that is sent to the screen, similar to the

command. For more information about I/O logging, see the

section. This flag is

by default.

If set,

will enable the TCP keepalive socket option on the connection to the log server. This enables the periodic transmission of keepalive messages to the server. If the server does not respond to a message, the connection will be closed and the running command will be terminated unless the

flag (I/O logging enabled) or the

flag (I/O logging disabled) is set. This flag is

by default.

This setting is only supported by version 1.9.0 or higher.

If set, the server certificate received during the TLS handshake must be valid and it must contain either the server name (from

or its IP address. If either of these conditions is not met, the TLS handshake will fail. This flag is

by default.

This setting is only supported by version 1.9.0 or higher.

If set,

will log when a command spawns a child process and executes a program using the

library functions. For example, if a shell is run by

the individual commands run via the shell will be logged. This flag is

by default.

The

flag uses the same underlying mechanism as the

setting. See

for more information on what systems support this option and its limitations. This setting is only supported by version 1.9.8 or higher and is incompatible with SELinux RBAC support.

If set, the four-digit year will be logged in the (non-syslog)

log file. This flag is

by default.

When validating with a One Time Password (OTP) scheme such as

a two-line prompt is used to make it easier to cut and paste the challenge to a local window. It's not as pretty as the default but some people find it more convenient. This flag is

by default.

Send mail to the

user every time a user attempts to run a command via

(this includes

No mail will be sent if the user runs

with the

option unless there is an authentication error and the

flag is also set. This flag is

by default.

Send mail to the

user every time a user runs

This flag is

by default.

Send mail to the

user if the user running

does not enter the correct password. If the command the user is attempting to run is not permitted by

and one of the

flags are set, this flag will have no effect. This flag is

by default.

If set, mail will be sent to the

user if the invoking user exists in the

file, but is not allowed to run commands on the current host. This flag is

by default.

If set, mail will be sent to the

user if the invoking user is allowed to use

but the command they are trying is not listed in their

file entry or is explicitly denied. This flag is

by default.

If set, mail will be sent to the

user if the invoking user is not in the

file. This flag is

by default.

By default,

will look up each group the user is a member of by group-ID to determine the group name (this is only done once). The resulting list of the user's group names is used when matching groups listed in the

file. This works well on systems where the number of groups listed in the

file is larger than the number of groups a typical user belongs to. On systems where group lookups are slow, where users may belong to a large number of groups, and where the number of groups listed in the

file is relatively small, it may be prohibitively expensive and running commands via

may take longer than normal. On such systems it may be faster to use the

flag to avoid resolving the user's group-IDs to group names. In this case,

must look up any group name listed in the

file and use the group-ID instead of the group name when determining whether the user is a member of the group.

Note that if

is enabled, group database lookups performed by

will be keyed by group name as opposed to group-ID. On systems where there are multiple sources for the group database, it is possible to have conflicting group names or group-IDs in the local

file and the remote group database. On such systems, enabling or disabling

can be used to choose whether group database queries are performed by name (enabled) or ID (disabled), which may aid in working around group entry conflicts.

The

flag has no effect when

data is stored in LDAP. This flag is

by default.

This setting is only supported by version 1.8.18 or higher.

If set, all commands run via

will behave as if the

tag has been set, unless overridden by an

tag. See the description of

above as well as the

section at the end of this manual. This flag is

by default.

This setting is only supported by version 1.9.8 or higher and is incompatible with SELinux RBAC support.

On most systems, the dynamic loader will ignore

(or the equivalent) when running set-user-ID and set-group-ID programs, effectively disabling intercept mode. To prevent this from happening,

will not permit a set-user-ID or set-group-ID program to be run in intercept mode unless

is set. This flag has no effect unless the

flag is enabled or the

tag has been set for the command. This flag is

by default.

This setting is only supported by version 1.9.8 or higher.

If set, commands run by an intercepted process must be authenticated when the user's time stamp is not current. For example, if a shell is run with

enabled, as soon as the invoking user's time stamp is out of date, subsequent commands will need to be authenticated. This flag has no effect unless the

flag is enabled or the

tag has been set for the command. This flag is

by default.

This setting is only supported by version 1.9.8 or higher.

If set, netgroup lookups will be performed using the full netgroup tuple: host name, user name, and domain (if one is set). Historically,

only matched the user name and domain for netgroups used in a

and only matched the host name and domain for netgroups used in a

This flag is

by default.

If set, all commands run via

will behave as if the

tag has been set, unless overridden by an

tag. See the description of

above as well as the

section at the end of this manual. This flag is

by default.

On systems that use PAM for authentication,

will perform PAM account validation for the invoking user by default. The actual checks performed depend on which PAM modules are configured. If enabled, account validation will be performed regardless of whether or not a password is required. This flag is

by default.

This setting is only supported by version 1.8.28 or higher.

On systems that use PAM for authentication,

will set the PAM remote host value to the name of the local host when the

flag is enabled. On Linux systems, enabling

may result in DNS lookups of the local host name when PAM is initialized. On Solaris versions prior to Solaris 8,

must be enabled if

is also enabled to avoid a crash in the Solaris PAM implementation.

This flag is

by default on systems other than Solaris.

This setting is only supported by version 1.9.0 or higher.

On systems that use PAM for authentication,

will set the PAM remote user value to the name of the user that invoked sudo when the

flag is enabled. This flag is

by default.

This setting is only supported by version 1.9.0 or higher.

On systems that use PAM for authentication,

will create a new PAM session for the command to be run in. Unless

is given the

options, PAM session modules are run with the

flag enabled. This prevents last login information from being displayed for every command on some systems. Disabling

may be needed on older PAM implementations or on operating systems where opening a PAM session changes the utmp or wtmp files. If PAM session support is disabled, resource limits may not be updated for the command being run. If

and

are disabled,

has not been set and I/O logging has not been configured,

will execute the command directly instead of running it as a child process. This flag is

by default.

This setting is only supported by version 1.8.7 or higher.

On systems that use PAM for authentication,

will attempt to establish credentials for the target user by default, if supported by the underlying authentication system. One example of a credential is a Kerberos ticket. If

and

are disabled,

has not been set and I/O logging has not been configured,

will execute the command directly instead of running it as a child process. This flag is

by default.

This setting is only supported by version 1.8.8 or higher.

If set, the prompt specified by

or the

environment variable will always be used and will replace the prompt provided by a PAM module or other authentication method. This flag is

by default.

Normally,

will tell the user when a command could not be found in their

environment variable. Some sites may wish to disable this as it could be used to gather information on the location of executables that the normal user does not have access to. The disadvantage is that if the executable is simply not in the user's

will tell the user that they are not allowed to run it, which can be confusing. This flag is

by default.

By default,

will initialize the group vector to the list of groups the target user is in. When

is set, the user's existing group vector is left unaltered. The real and effective group-IDs, however, are still set to match the target user. This flag is

by default.

By default,

reads the password like most other Unix programs, by turning off echo until the user hits the return (or enter) key. Some users become confused by this as it appears to them that

has hung at this point. When

is set,

will provide visual feedback when the user presses a key. Note that this does have a security impact as an onlooker may be able to determine the length of the password being entered. This flag is

by default.

If set,

will only run when the user is logged in to a real tty. When this flag is set,

can only be run from a login session and not via other means such as

or cgi-bin scripts. This flag is

by default.

If set, root is allowed to run

too. Disabling this prevents users from

commands to get a root shell by doing something like

Note, however, that turning off

will also prevent root from running

Disabling

provides no real additional security; it exists purely for historical reasons. This flag is

by default.

If set,

will prompt for the root password instead of the password of the invoking user when running a command or editing a file. This flag is

by default.

If enabled, allow matching of runas user and group IDs that are not present in the password or group databases. In addition to explicitly matching unknown user or group IDs in a

this option also allows the

alias to match unknown IDs. This flag is

by default.

This setting is only supported by version 1.8.30 or higher. Older versions of

always allowed matching of unknown user and group IDs.

If enabled,

will only run commands as a user whose shell appears in the

file, even if the invoking user's

would otherwise permit it. If no

file is present, a system-dependent list of built-in default shells is used. On many operating systems, system users such as

do not have a valid shell and this flag can be used to prevent commands from being run as those users. This flag is

by default.

This setting is only supported by version 1.8.30 or higher.

If set,

will prompt for the password of the user defined by the

option (defaults to

instead of the password of the invoking user when running a command or editing a file. This flag is

by default.

If enabled and

is invoked with the

option, the

environment variable will be set to the home directory of the target user (which is the root user unless the

option is used). This flag is largely obsolete and has no effect unless the

flag has been disabled or

is present in the

list, both of which are strongly discouraged. This flag is

by default.

Normally,

will set the

and

environment variables to the name of the target user (usually root unless the

option is given). However, since some programs (including the RCS revision control system) use

to determine the real identity of the user, it may be desirable to change this behavior. This can be done by negating the set_logname option. Note that

will have no effect if the

option has not been disabled and the

list contains

This flag is

by default.

When enabled,

will create an entry in the utmp (or utmpx) file when a pseudo-terminal is allocated. A pseudo-terminal is allocated by

when it is running in a terminal and one or more of the

flags is enabled. By default, the new entry will be a copy of the user's existing utmp entry (if any), with the tty, time, type, and pid fields updated. This flag is

by default.

Allow the user to disable the

option from the command line via the

option. Additionally, environment variables set via the command line are not subject to the restrictions imposed by

As such, only trusted users should be allowed to set variables in this manner. This flag is

by default.

If set and

is invoked with no arguments it acts as if the

option had been given. That is, it runs a shell as root (the shell is determined by the

environment variable if it is set, falling back on the shell listed in the invoking user's /etc/passwd entry if not). This flag is

by default.

Normally, when

executes a command the real and effective user-IDs are set to the target user (root by default). This option changes that behavior such that the real user-ID is left as the invoking user's user-ID. In other words, this makes

act as a set-user-ID wrapper. This can be useful on systems that disable some potentially dangerous functionality when a program is run set-user-ID. This option is only effective on systems that support either the

system call. This flag is

by default.

If set,

will check all directory components of the path to be edited for writability by the invoking user. Symbolic links will not be followed in writable directories and

will refuse to edit a file located in a writable directory. These restrictions are not enforced when

is run by root. On some systems, if all directory components of the path to be edited are not readable by the target user,

will be unable to edit the file. This flag is

by default.

This setting was first introduced in version 1.8.15 but initially suffered from a race condition. The check for symbolic links in writable intermediate directories was added in version 1.8.16.

By default,

will not follow symbolic links when opening files. The

option can be enabled to allow

to open symbolic links. It may be overridden on a per-command basis by the

and

tags. This flag is

by default.

This setting is only supported by version 1.8.15 or higher.

When logging via

include the process ID in the log entry. This flag is

by default.

This setting is only supported by version 1.8.21 or higher.

If set,

will prompt for the password of the user specified by the

option (defaults to

instead of the password of the invoking user when running a command or editing a file. Note that this flag precludes the use of a user-ID not listed in the passwd database as an argument to the

option. This flag is

by default.

If set, users must authenticate on a per-tty basis. With this flag enabled,

will use a separate record in the time stamp file for each terminal. If disabled, a single record is used for all login sessions.

This option has been superseded by the

option.

If set,

will set the umask as specified in the

file without modification. This makes it possible to specify a umask in the

file that is more permissive than the user's own umask and matches historical behavior. If

is not set,

will set the umask to be the union of the user's umask and what is specified in

This flag is

by default.

If set, netgroups (prefixed with

may be used in place of a user or host. For LDAP-based sudoers, netgroup support requires an expensive sub-string match on the server unless the

directive is present in the

file. If netgroups are not needed, this option can be disabled to reduce the load on the LDAP server. This flag is

by default.

If set, and

is running in a terminal, the command will be run in a pseudo-terminal (even if no I/O logging is being done). If the

process is not attached to a terminal,

has no effect.

A malicious program run under

may be capable of injecting commands into the user's terminal or running a background process that retains access to the user's terminal device even after the main program has finished executing. By running the command in a separate pseudo-terminal, this attack is no longer possible. This flag is

by default.

If set, the user may specify a timeout on the command line. If the timeout expires before the command has exited, the command will be terminated. If a timeout is specified both in the

file and on the command line, the smaller of the two timeouts will be used. See the

section for a description of the timeout syntax. This flag is

by default.

This setting is only supported by version 1.8.20 or higher.

If set,

will store the name of the runas user when updating the utmp (or utmpx) file. By default,

stores the name of the invoking user. This flag is

by default.

By default,

will refuse to run if the user must enter a password but it is not possible to disable echo on the terminal. If the

flag is set,

will prompt for a password even when it would be visible on the screen. This makes it possible to run things like

since by default,

does not allocate a tty when running a command. This flag is

by default.

Before it executes a command,

will close all open file descriptors other than standard input, standard output, and standard error (file descriptors 0-2). The

option can be used to specify a different file descriptor at which to start closing. The default is

The maximum amount of time a command is allowed to run before it is terminated. See the

section for a description of the timeout syntax.

This setting is only supported by version 1.8.20 or higher.

The maximum amount of time to wait when connecting to a log server or waiting for a server response. See the

section for a description of the timeout syntax. The default value is 30 seconds.

This setting is only supported by version 1.9.0 or higher.

The maximum sequence number that will be substituted for the

escape in the I/O log file (see the

description below for more information). While the value substituted for

is in base 36,

itself should be expressed in decimal. Values larger than 2176782336 (which corresponds to the base 36 sequence number

will be silently truncated to 2176782336. The default value is 2176782336.

Once the local sequence number reaches the value of

it will

to zero, after which

will truncate and re-use any existing I/O log path names.

This setting is only supported by version 1.8.7 or higher.

The number of tries a user gets to enter his/her password before

logs the failure and exits. The default is

On many systems,

has a relatively small log buffer. IETF RFC 5424 states that syslog servers must support messages of at least 480 bytes and should support messages up to 2048 bytes. By default,

creates log messages up to 980 bytes which corresponds to the historic

syslog implementation which used a 1024 byte buffer to store the message, date, hostname, and program name. To prevent syslog messages from being truncated,

will split up log messages that are larger than

bytes. When a message is split, additional parts will include the string

after the user name and before the continued command line arguments.

This setting is only supported by version 1.8.19 or higher.

Number of characters per line for the file log. This value is used to decide when to wrap lines for nicer log files. This has no effect on the syslog log file, only the file log. The default is

(use 0 or negate the option to disable word wrap).

Number of minutes before the

password prompt times out, or

for no timeout. The timeout may include a fractional component if minute granularity is insufficient, for example

The default is

Number of minutes that can elapse before

will ask for a passwd again. The timeout may include a fractional component if minute granularity is insufficient, for example

The default is

Set this to

to always prompt for a password. If set to a value less than

the user's time stamp will not expire until the system is rebooted. This can be used to allow users to create or delete their own time stamps via

and

respectively.

File mode creation mask to use when running the command. Negate this option or set it to 0777 to prevent

from changing the umask. Unless the

flag is set, the actual umask will be the union of the user's umask and the value of the

setting, which defaults to

This guarantees that

never lowers the umask when running a command.

is explicitly set in

it will override any umask setting in PAM or login.conf. If

is not set in

the umask specified by PAM or login.conf will take precedence. The umask setting in PAM is not used for

which does not create a new PAM session.

Message that is displayed after a user fails to authenticate. The message may include the

escape which will expand to the number of failed password attempts. If set, it overrides the default message,

Message that is displayed if a user enters an incorrect password. The default is

unless insults are enabled.

A colon

separated list of editors path names used by

and

For

this list is used to find an editor when none of the

environment variables are set to an editor that exists and is executable. For

it is used as a white list of allowed editors;

will choose the editor that matches the user's

environment variable if possible, or the first editor in the list that exists and is executable if not. Unless invoked as

does not preserve the

environment variables unless they are present in the

list or the

option is disabled. The default is

The top-level directory to use when constructing the path name for the input/output log directory. Only used if the

options are enabled or when the

tags are present for a command. The session sequence number, if any, is stored in the directory. The default is

The following percent

escape sequences are supported:

expanded to a monotonically increasing base-36 sequence number, such as 0100A5, where every two digits are used to form a new directory, e.g.,

expanded to the invoking user's login name

expanded to the name of the invoking user's real group-ID

expanded to the login name of the user the command will be run as (e.g., root)

expanded to the group name of the user the command will be run as (e.g., wheel)

expanded to the local host name without the domain name

expanded to the base name of the command being run

In addition, any escape sequences supported by the system's

function will be expanded.

To include a literal

character, the string

should be used.

The path name, relative to

in which to store input/output logs when the

options are enabled or when the

tags are present for a command. Note that

may contain directory components. The default is

See the

option above for a list of supported percent

escape sequences.

In addition to the escape sequences, path names that end in six or more

will have the

replaced with a unique combination of digits and letters, similar to the

function.

If the path created by concatenating

and

already exists, the existing I/O log file will be truncated and overwritten unless

ends in six or more

If set,

will flush I/O log data to disk after each write instead of buffering it. This makes it possible to view the logs in real-time as the program is executing but may significantly reduce the effectiveness of I/O log compression. This flag is

by default.

This setting is only supported by version 1.8.20 or higher.

The group name to look up when setting the group-ID on new I/O log files and directories. If

is not set, the primary group-ID of the user specified by

is used. If neither

nor

are set, I/O log files and directories are created with group-ID 0.

This setting is only supported by version 1.8.19 or higher.

The file mode to use when creating I/O log files. Mode bits for read and write permissions for owner, group, or other are honored, everything else is ignored. The file permissions will always include the owner read and write bits, even if they are not present in the specified mode. When creating I/O log directories, search (execute) bits are added to match the read and write bits specified by

Defaults to 0600 (read and write by user only).

This setting is only supported by version 1.8.19 or higher.

The user name to look up when setting the user and group-IDs on new I/O log files and directories. If

is set, it will be used instead of the user's primary group-ID. By default, I/O log files and directories are created with user and group-ID 0.

This setting can be useful when the I/O logs are stored on a Network File System (NFS) share. Having a dedicated user own the I/O log files means that

does not write to the log files as user-ID 0, which is usually not permitted by NFS.

This setting is only supported by version 1.8.19 or higher.

The directory in which

stores per-user lecture status files. Once a user has received the lecture, a zero-length file is created in this directory so that

will not lecture the user again. This directory should

be cleared when the system reboots. The default is

The path to a certificate authority bundle file, in PEM format, to use instead of the system's default certificate authority database when authenticating the log server. The default is to use the system's default certificate authority database. This setting has no effect unless

is set and the remote log server is secured with TLS.

This setting is only supported by version 1.9.0 or higher.

The path to the

client's certificate file, in PEM format. This setting is required when the remote log server is secured with TLS and client certificate validation is enabled. For

client certificate validation is controlled by the

option, which defaults to

This setting is only supported by version 1.9.0 or higher.

The path to the

client's private key file, in PEM format. This setting is required when the remote log server is secured with TLS and client certificate validation is enabled. For

client certificate validation is controlled by the

option, which defaults to

This setting is only supported by version 1.9.0 or higher.

Subject of the mail sent to the

user. The escape

will expand to the host name of the machine. Default is

As of

version 1.8.1 this option is no longer supported. The path to the noexec file should now be set in the

file.

On systems that use PAM for authentication, this is the service name used when the

option is specified. The default value is either

depending on whether or not the

option is also specified. See the description of

for more information.

This setting is only supported by version 1.9.9 or higher.

On systems that use PAM for authentication, this is the service name used when the

option is specified. The default value is

See the description of

for more information.

This setting is only supported by version 1.8.8 or higher.

On systems that use PAM for authentication, the service name specifies the PAM policy to apply. This usually corresponds to an entry in the

file or a file in the

directory. The default value is

This setting is only supported by version 1.8.8 or higher.

The default prompt to use when asking for a password; can be overridden via the

option or the

environment variable. The following percent

escape sequences are supported:

expanded to the local host name including the domain name (only if the machine's host name is fully qualified or the

option is set)

expanded to the local host name without the domain name

expanded to the user whose password is being asked for (respects the

and

flags in

expanded to the login name of the user the command will be run as (defaults to root)

expanded to the invoking user's login name

two consecutive

characters are collapsed into a single

character

On systems that use PAM for authentication,

will only be used if the prompt provided by the PAM module matches the string

This ensures that the

setting does not interfere with challenge-response style authentication. The

flag can be used to change this behavior.

The default value is

The default user to run commands as if the

option is not specified on the command line. This defaults to

Locale to use when parsing the sudoers file, logging commands, and sending email. Note that changing the locale may affect how sudoers is interpreted. Defaults to

uses per-user time stamp files for credential caching. The

option can be used to specify the type of time stamp record used. It has the following possible values:

A single time stamp record is used for all of a user's login sessions, regardless of the terminal or parent process ID. An additional record is used to serialize password prompts when

is used multiple times in a pipeline, but this does not affect authentication.

A single time stamp record is used for all processes with the same parent process ID (usually the shell). Commands run from the same shell (or other common parent process) will not require a password for

minutes

by default

Commands run via

with a different parent process ID, for example from a shell script, will be authenticated separately.

One time stamp record is used for each terminal, which means that a user's login sessions are authenticated separately. If no terminal is present, the behavior is the same as

Commands run from the same terminal will not require a password for

minutes

by default

The time stamp is stored in the kernel as an attribute of the terminal device. If no terminal is present, the behavior is the same as

Negative

values are not supported and positive values are limited to a maximum of 60 minutes. This is currently only supported on

The default value is

This setting is only supported by version 1.8.21 or higher.

The directory in which

stores its time stamp files. This directory should be cleared when the system reboots. The default is

The owner of the lecture status directory, time stamp directory and all files stored therein. The default is

The

option specifies the path to a file that is created the first time a user that is a member of the

groups runs

Only available if

is configured with the

option. The default value is

The

option specifies the fully qualified path to a file containing variables to be set in the environment of the program being run. Entries in this file should either be of the form

The value may optionally be enclosed in single or double quotes. Variables in this file are only added if the variable does not already exist in the environment. This file is considered to be part of the security policy, its contents are not subject to other

environment restrictions such as

and

Users in this group are exempt from password and PATH requirements. The group name specified should not include a

prefix. This is not set by default.

Determines whether

will execute a command by its path or by an open file descriptor. It has the following possible values:

Always execute by file descriptor.

Never execute by file descriptor.

Only execute by file descriptor if the command has an associated digest in the

file.

The default value is

This avoids a time of check versus time of use race condition when the command is located in a directory writable by the invoking user.

Note that

will change the first element of the argument vector for scripts ($0 in the shell) due to the way the kernel runs script interpreters. Instead of being a normal path, it will refer to a file descriptor. For example,

on Solaris and

on Linux. A workaround is to use the

environment variable instead.

The

setting is only used when the command is matched by path name. It has no effect if the command is matched by the built-in

alias.

This setting is only supported by version 1.8.20 or higher. If the operating system does not support the

system call, this setting has no effect.

A string containing a

group plugin with optional arguments. The string should consist of the plugin path, either fully-qualified or relative to the

directory, followed by any configuration arguments the plugin requires. These arguments (if any) will be passed to the plugin's initialization function. If arguments are present, the string must be enclosed in double quotes

For more information see

This option controls when a short lecture will be printed along with the password prompt. It has the following possible values:

Always lecture the user.

Never lecture the user.

Only lecture the user the first time they run

If no value is specified, a value of

is implied. Negating the option results in a value of

being used. The default value is

Path to a file containing an alternate

lecture that will be used in place of the standard lecture if the named file exists. By default,

uses a built-in lecture.

This option controls when a password will be required when a user runs

with the

option. It has the following possible values:

All the user's

file entries for the current host must have the

flag set to avoid entering a password.

The user must always enter a password to use the

option.

At least one of the user's

file entries for the current host must have the

flag set to avoid entering a password.

The user need never enter a password to use the

option.

If no value is specified, a value of

is implied. Negating the option results in a value of

being used. The default value is

The event log format. Supported log formats are:

Logs in JSON format. JSON log entries contain the full user details as well as the execution environment if the command was allowed. Due to limitations of the protocol, JSON events sent via

may be truncated.

Traditional sudo-style logs, see

for a description of the log file format.

This setting affects logs sent via

as well as the file specified by the

setting, if any. The default value is

Path to the

log file (not the syslog log file). Setting a path turns on logging to a file; negating this option turns it off. By default,

logs via syslog.

Flags to use when invoking mailer. Defaults to

Path to mail program used to send warning mail. Defaults to the path to sendmail found at configure time.

Address to use for the

address when sending warning and error mail. The address should be enclosed in double quotes

to protect against

interpreting the

sign. Defaults to the name of the user running

Address to send warning and error mail to. The address should be enclosed in double quotes

to protect against

interpreting the

sign. Defaults to

The maximum size to which the process's address space may grow (in bytes), if supported by the operating system. See

for more information.

The largest size core dump file that may be created (in bytes). See

for more information. Defaults to 0 (no core dump created).

The maximum amount of CPU time that the process may use (in seconds). See

for more information.

The maximum size of the data segment for the process (in bytes). See

for more information.

The largest size file that the process may create (in bytes). See

for more information.

The maximum number of locks that the process may establish, if supported by the operating system. See

for more information.

The maximum size that the process may lock in memory (in bytes), if supported by the operating system. See

for more information.

The maximum number of files that the process may have open. See

for more information.

The maximum number of processes that the user may run simultaneously. See

for more information.

The maximum size to which the process's resident set size may grow (in bytes). See

for more information.

The maximum size to which the process's stack may grow (in bytes). See

for more information.

The

option specifies the fully qualified path to a file containing variables to be set in the environment of the program being run. Entries in this file should either be of the form

The value may optionally be enclosed in single or double quotes. Variables in this file are only added if the variable does not already exist in the environment. Unlike

the file's contents are not trusted and are processed in a manner similar to that of the invoking user's environment. If

is enabled, variables in the file will only be added if they are matched by either the

list. If

is disabled, variables in the file are added as long as they are not matched by the

list. In either case, the contents of

are processed before the contents of

If set,

will use this value for the root directory when running a command. The special value

will allow the user to specify the root directory via

option. See the

section for more details.

It is only possible to use

as a command-specific Defaults setting if the command exists with the same path both inside and outside the chroot jail. This restriction does not apply to generic, host, or user-based Defaults settings or to a

that includes a

This setting is only supported by version 1.9.3 or higher.

If set,

will use this value for the working directory when running a command. The special value

will allow the user to specify the working directory via

option. See the

section for more details.

This setting is only supported by version 1.9.3 or higher.

If set,

will use this value in place of the user's

environment variable. This option can be used to reset the

to a known good value that contains directories for system administrator commands such as

Users in the group specified by the

option are not affected by

This option is not set by default.

Syslog facility if syslog is being used for logging (negate to disable syslog logging). Defaults to

The following syslog facilities are supported:

(if your OS supports it),

and

Syslog priority to use when the user is not allowed to run a command or when authentication is unsuccessful. Defaults to

The following syslog priorities are supported:

and

Negating the option or setting it to a value of

will disable logging of unsuccessful commands.

Syslog priority to use when the user is allowed to run a command and authentication is successful. Defaults to

See

for the list of supported syslog priorities. Negating the option or setting it to a value of

will disable logging of successful commands.

This option controls when a password will be required when a user runs

with the

option. It has the following possible values:

All the user's

file entries for the current host must have the

flag set to avoid entering a password.

The user must always enter a password to use the

option.

At least one of the user's

file entries for the current host must have the

flag set to avoid entering a password.

The user need never enter a password to use the

option.

If no value is specified, a value of

is implied. Negating the option results in a value of

being used. The default value is

Environment variables to be removed from the user's environment unless they are considered

For all variables except

means that the variable's value does not contain any

characters. This can be used to guard against printf-style format vulnerabilities in poorly-written programs. The

variable is considered unsafe if any of the following are true:

It consists of a fully-qualified path name, optionally prefixed with a colon

that does not match the location of the

directory.

It contains a

path element.

It contains white space or non-printable characters.

It is longer than the value of

The argument may be a double-quoted, space-separated list or a single value without double-quotes. The list can be replaced, added to, deleted from, or disabled by using the

and

operators respectively. Regardless of whether the

option is enabled or disabled, variables specified by

will be preserved in the environment if they pass the aforementioned check. The global list of environment variables to check is displayed when

is run by root with the

option.

Environment variables to be removed from the user's environment when the

option is not in effect. The argument may be a double-quoted, space-separated list or a single value without double-quotes. The list can be replaced, added to, deleted from, or disabled by using the

and

operators respectively. The global list of environment variables to remove is displayed when

is run by root with the

option. Note that many operating systems will remove potentially dangerous variables from the environment of any set-user-ID process (such as

Environment variables to be preserved in the user's environment when the

option is in effect. This allows fine-grained control over the environment

processes will receive. The argument may be a double-quoted, space-separated list or a single value without double-quotes. The list can be replaced, added to, deleted from, or disabled by using the

and

operators respectively. The global list of variables to keep is displayed when

is run by root with the

option.

Preserving the

environment variable has security implications since many programs use it when searching for configuration or data files. Adding

may enable a user to run unrestricted commands via

and is strongly discouraged. Users wishing to edit files with

should run

(or

to get their accustomed editor configuration instead of invoking the editor directly.

A list of one or more servers to use for remote event and I/O log storage, separated by white space. Log servers must be running

or another service that implements the protocol described by

Server addresses should be of the form

The host portion may be a host name, an IPv4 address, or an IPv6 address in square brackets.

If the optional

flag is present, the connection will be secured with Transport Layer Security (TLS) version 1.2 or 1.3. Versions of TLS prior to 1.2 are not supported.

If a port is specified, it may either be a port number or a well-known service name as defined by the system service name database. If no port is specified, port 30343 will be used for plaintext connections and port 30344 will be used for TLS connections.

When

is set, event log data will be logged both locally (see the

and

settings) as well as remotely, but I/O log data will only be logged remotely. If multiple hosts are specified, they will be attempted in reverse order. If no log servers are available, the user will not be able to run a command unless either the

flag (I/O logging enabled) or the

flag (I/O logging disabled) is set. Likewise, if the connection to the log server is interrupted while

is running, the command will be terminated unless the

flag (I/O logging enabled) or the

flag (I/O logging disabled) is set.

This setting is only supported by version 1.9.0 or higher.

The

plugin supports its own plugin interface to allow non-Unix group lookups which can query a group source other than the standard Unix group database. This can be used to implement support for the

syntax described earlier.

Group provider plugins are specified via the

setting. The argument to

should consist of the plugin path, either fully-qualified or relative to the

directory, followed by any configuration options the plugin requires. These options (if specified) will be passed to the plugin's initialization function. If options are present, the string must be enclosed in double quotes

The following group provider plugins are installed by default:

The

plugin supports an alternate group file that uses the same syntax as the

file. The path to the group file should be specified as an option to the plugin. For example, if the group file to be used is

Defaults group_plugin="group_file.so /etc/sudo-group"

The

plugin supports group lookups via the standard C library functions

and

This plugin can be used in instances where the user belongs to groups not present in the user's supplemental group vector. This plugin takes no options:

Defaults group_plugin=system_group.so

The group provider plugin API is described in detail in

can log events in either JSON or

format, this section describes the

log format. Depending on

configuration,

can log events via

to a local log file, or both. The log format is almost identical in both cases.

Commands that sudo runs are logged using the following format (split into multiple lines for readability):

date hostname progname: username : TTY=ttyname ; PWD=cwd ; \ USER=runasuser ; GROUP=runasgroup ; TSID=logid ; \ ENV=env_vars COMMAND=command

Where the fields are as follows:

The date the command was run. Typically, this is in the format

If logging via

the actual date format is controlled by the syslog daemon. If logging to a file and the

option is enabled, the date will also include the year.

The name of the host

was run on. This field is only present when logging via

The name of the program, usually

This field is only present when logging via

The login name of the user who ran

The short name of the terminal (e.g.,

was run on, or

if there was no terminal present.

The current working directory that

was run in.

The user the command was run as.

The group the command was run as if one was specified on the command line.

An I/O log identifier that can be used to replay the command's output. This is only present when the

option is enabled.

A list of environment variables specified on the command line, if specified.

The actual command that was executed.

Messages are logged using the locale specified by

which defaults to the

locale.

If the user is not allowed to run the command, the reason for the denial will follow the user name. Possible reasons include:

The user is not listed in the

file.

The user is listed in the

file but is not allowed to run commands on the host.

The user is listed in the

file for the host but they are not allowed to run the specified command.

The user failed to enter their password after 3 tries. The actual number of tries will vary based on the number of failed attempts and the value of the

option.

The

option was specified but a password was required.

The user specified environment variables on the command line that were not allowed by

If an error occurs,

will log a message and, in most cases, send a message to the administrator via email. Possible errors include:

encountered an error when parsing the specified file. In some cases, the actual error may be one line above or below the line number listed, depending on the type of error.

The

file contains one or more unknown Defaults settings. This does not prevent

from running, but the

file should be checked using

The time stamp directory owner, as specified by the

setting, could not be found in the password database.

The

file could not be opened for reading. This can happen when the

file is located on a remote file system that maps user-ID 0 to a different value. Normally,

tries to open the

file using group permissions to avoid this problem. Consider either changing the ownership of

or adding an argument like

(where

is the user-ID that owns the

file) to the end of the

line in the

file.

The

file is missing.

The

file exists but is not a regular file or symbolic link.

The

file has the wrong owner. If you wish to change the

file owner, please add

(where

is the user-ID that owns the

file) to the

line in the

file.

The permissions on the

file allow all users to write to it. The

file must not be world-writable, the default file mode is 0440 (readable by owner and group, writable by none). The default mode may be changed via the

option to the

line in the

file.

The

file has the wrong group ownership. If you wish to change the

file group ownership, please add

(where

is the group-ID that owns the

file) to the

line in the

file.

was unable to read or create the user's time stamp file. This can happen when

is set to a user other than root and the mode on

is not searchable by group or other. The default mode for

is 0711.

was unable to write to the user's time stamp file.

The time stamp directory is owned by a user other than

This can occur when the value of

has been changed.

will ignore the time stamp directory until the owner is corrected.

The time stamp directory is group-writable; it should be writable only by

The default mode for the time stamp directory is 0700.

will ignore the time stamp directory until the mode is corrected.

By default,

logs messages via

The

and

fields are added by the system's

function, not

itself. As such, they may vary in format on different systems.

The maximum size of syslog messages varies from system to system. The

setting can be used to change the maximum syslog message size from the default value of 980 bytes. For more information, see the description of

If the

option is set,

will log to a local file, such as

When logging to a file,

uses a format similar to

with a few important differences:

The

and

fields are not present.

If the

option is enabled, the date will also include the year.

Lines that are longer than

characters (80 by default) are word-wrapped and continued on the next line with a four character indent. This makes entries easier to read for a human being, but makes it more difficult to use

on the log files. If the

option is set to 0 (or negated with a

word wrap will be disabled.

When I/O logging is enabled,

will run the command in a pseudo-terminal and log all user input and/or output, depending on which options are enabled. I/O can be logged either to the local machine or to a remote log server. For local logs, I/O is logged to the directory specified by the

option

by default

using a unique session ID that is included in the

log line, prefixed with

The

option may be used to control the format of the session ID. For remote logs, the

setting is used to specify one or more log servers running

or another server that implements the protocol described by

For both local and remote I/O logs, each log is stored in a separate directory that contains the following files:

A text file containing information about the command. The first line consists of the following colon-delimited fields: the time the command was run, the name of the user who ran

the name of the target user, the name of the target group (optional), the terminal that

was run from, and the number of lines and columns of the terminal. The second and third lines contain the working directory the command was run from and the path name of the command itself (with arguments if present).

A JSON-formatted file containing information about the command. This is similar to the

file but contains additional information and is easily extensible. The

file will be used by

in preference to the

file if it exists. The file may contain the following elements:

A JSON object containing time the command was run. It consists of two values,

and

The number of columns of the terminal the command ran on, or zero if no terminal was present.

The fully-qualified path of the command that was run.

The number of lines of the terminal the command ran on, or zero if no terminal was present.

A JSON array representing the command's argument vector as passed to the

system call.

A JSON array representing the command's environment as passed to the

system call.

The group ID the command ran as. This element is only present when the user specifies a group on the command line.

The name of the group the command ran as. This element is only present when the user specifies a group on the command line.

The user ID the command ran as.

The name of the user the command ran as.

The current working directory at the time

was run.

The name of the host the command was run on.

The name of the user who ran the command via

The path name of the terminal the user invoked

from. If the command was run in a pseudo-terminal,

will be different from the terminal the command actually ran in.

Timing information used to replay the session. Each line consists of the I/O log entry type and amount of time since the last entry, followed by type-specific data. The I/O log entry types and their corresponding type-specific data are:

standard input, number of bytes in the entry

standard output, number of bytes in the entry

standard error, number of bytes in the entry

terminal input, number of bytes in the entry

terminal output, number of bytes in the entry

window change, new number lines and columns

bug compatibility for

1.8.7 terminal output

command suspend or resume, signal received

Raw input from the user's terminal, exactly as it was received. No post-processing is performed. For manual viewing, you may wish to convert carriage return characters in the log to line feeds. For example:

The standard input when no terminal is present, or input redirected from a pipe or file.

Output from the pseudo-terminal (what the command writes to the screen). Note that terminal-specific post-processing is performed before the data is logged. This means that, for example, line feeds are usually converted to line feed/carriage return pairs and tabs may be expanded to spaces.

The standard output when no terminal is present, or output redirected to a pipe or file.

The standard error redirected to a pipe or file.

All files other than

are compressed in gzip format unless the

flag has been disabled. Due to buffering, it is not normally possible to display the I/O logs in real-time as the program is executing. The I/O log data will not be complete until the program run by

has exited or has been terminated by a signal. The

flag can be used to disable buffering, in which case I/O log data is written to disk as soon as it is available. The output portion of an I/O log file can be viewed with the

utility, which can also be used to list or search the available logs.

Note that user input may contain sensitive information such as passwords (even if they are not echoed to the screen), which will be stored in the log file unencrypted. In most cases, logging the command output via

is all that is required.

Since each session's I/O logs are stored in a separate directory, traditional log rotation utilities cannot be used to limit the number of I/O logs. The simplest way to limit the number of I/O is by setting the

option to the maximum number of logs you wish to store. Once the I/O log sequence number reaches

it will be reset to zero and

will truncate and re-use any existing I/O logs.

Sudo front-end configuration

List of who can run what

Local groups file

List of network groups

I/O log files

Directory containing time stamps for the

security policy

Directory containing lecture status files for the

security policy

Initial environment for

mode on AIX and Linux systems

Below are example

file entries. Admittedly, some of these are a bit contrived. First, we allow a few environment variables to pass and then define our

# Run X applications through sudo; HOME is used to find the # .Xauthority file. Note that other programs use HOME to find # configuration files and this may lead to privilege escalation! Defaults env_keep += "DISPLAY HOME"

# User alias specification User_Alias FULLTIMERS = millert, mikef, dowdy User_Alias PARTTIMERS = bostley, jwfox, crawl User_Alias WEBADMIN = will, wendy, wim

# Runas alias specification Runas_Alias OP = root, operator Runas_Alias DB = oracle, sybase Runas_Alias ADMINGRP = adm, oper

# Host alias specification Host_Alias SPARC = bigtime, eclipse, moet, anchor :\ SGI = grolsch, dandelion, black :\ ALPHA = widget, thalamus, foobar :\ HPPA = boa, nag, python Host_Alias CUNETS = 128.138.0.0/255.255.0.0 Host_Alias CSNETS = 128.138.243.0, 128.138.204.0/24, 128.138.242.0 Host_Alias SERVERS = primary, mail, www, ns Host_Alias CDROM = orion, perseus, hercules

# Cmnd alias specification Cmnd_Alias DUMPS = /usr/bin/mt, /usr/sbin/dump, /usr/sbin/rdump,\ /usr/sbin/restore, /usr/sbin/rrestore,\ sha224:0GomF8mNN3wlDt1HD9XldjJ3SNgpFdbjO1+NsQ== \ /home/operator/bin/start_backups Cmnd_Alias KILL = /usr/bin/kill Cmnd_Alias PRINTING = /usr/sbin/lpc, /usr/bin/lprm Cmnd_Alias SHUTDOWN = /usr/sbin/shutdown Cmnd_Alias HALT = /usr/sbin/halt Cmnd_Alias REBOOT = /usr/sbin/reboot Cmnd_Alias SHELLS = /usr/bin/sh, /usr/bin/csh, /usr/bin/ksh,\ /usr/local/bin/tcsh, /usr/bin/rsh,\ /usr/local/bin/zsh Cmnd_Alias SU = /usr/bin/su Cmnd_Alias PAGERS = /usr/bin/more, /usr/bin/pg, /usr/bin/less

Here we override some of the compiled in default values. We want

to log via

using the

facility in all cases and for commands to be run with the target user's home directory as the working directory. We don't want to subject the full time staff to the

lecture and we want to allow them to run commands in a

via the

option. User

need not provide a password and we don't want to reset the

environment variables when running commands as root. Additionally, on the machines in the

we keep an additional local log file and make sure we log the year in each log line since the log entries will be kept around for several years. Lastly, we disable shell escapes for the commands in the PAGERS

and

Note that this will not effectively constrain users with

privileges.

# Override built-in defaults Defaults syslog=auth,runcwd=~ Defaults>root !set_logname Defaults:FULLTIMERS !lecture,runchroot=* Defaults:millert !authenticate Defaults@SERVERS log_year, logfile=/var/log/sudo.log Defaults!PAGERS noexec

The

is the part that actually determines who may run what.

root ALL = (ALL) ALL %wheel ALL = (ALL) ALL

We let

and any user in group

run any command on any host as any user.

FULLTIMERS ALL = NOPASSWD: ALL

Full time sysadmins

and

may run any command on any host without authenticating themselves.

PARTTIMERS ALL = ALL

Part time sysadmins

and

may run any command on any host but they must authenticate themselves first (since the entry lacks the

tag).

jack CSNETS = ALL

The user

may run any command on the machines in the

alias (the networks

and

Of those networks, only

has an explicit netmask (in CIDR notation) indicating it is a class C network. For the other networks in

the local machine's netmask will be used during matching.

lisa CUNETS = ALL

The user

may run any command on any host in the

alias (the class B network

operator ALL = DUMPS, KILL, SHUTDOWN, HALT, REBOOT, PRINTING,\ sudoedit /etc/printcap, /usr/oper/bin/

The

user may run commands limited to simple maintenance. Here, those are commands related to backups, killing processes, the printing system, shutting down the system, and any commands in the directory

Note that one command in the

Cmnd_Alias includes a sha224 digest,

This is because the directory containing the script is writable by the operator user. If the script is modified (resulting in a digest mismatch) it will no longer be possible to run it via

joe ALL = /usr/bin/su operator

The user

may only

to operator.

pete HPPA = /usr/bin/passwd [A-Za-z]*, !/usr/bin/passwd *root*

%opers ALL = (: ADMINGRP) /usr/sbin/

Users in the

group may run commands in

as themselves with any group in the

(the

and

groups).

The user

is allowed to change anyone's password except for root on the

machines. Because command line arguments are matched as a single, concatenated string, the

wildcard will match

words. This example assumes that

does not take multiple user names on the command line. Note that on GNU systems, options to

may be specified after the user argument. As a result, this rule will also allow:

passwd username --expire

which may not be desirable.

bob SPARC = (OP) ALL : SGI = (OP) ALL

The user

may run anything on the

and

machines as any user listed in the

and

jim +biglab = ALL

The user

may run any command on machines in the

netgroup.

knows that

is a netgroup due to the

prefix.

+secretaries ALL = PRINTING, /usr/bin/adduser, /usr/bin/rmuser

Users in the

netgroup need to help manage the printers as well as add and remove users, so they are allowed to run those commands on all machines.

fred ALL = (DB) NOPASSWD: ALL

The user

can run commands as any user in the

without giving a password.

john ALPHA = /usr/bin/su [!-]*, !/usr/bin/su *root*

On the

machines, user

may su to anyone except root but he is not allowed to specify any options to the

command.

jen ALL, !SERVERS = ALL

The user

may run any command on any machine except for those in the

(primary, mail, www, and ns).

jill SERVERS = /usr/bin/, !SU, !SHELLS

For any machine in the

may run any commands in the directory

except for those commands belonging to the

and

While not specifically mentioned in the rule, the commands in the

all reside in

and have the

option set.

steve CSNETS = (operator) /usr/local/op_commands/

The user

may run any command in the directory /usr/local/op_commands/ but only as user operator.

matt valkyrie = KILL

On his personal workstation, valkyrie,

needs to be able to kill hung processes.

WEBADMIN www = (www) ALL, (root) /usr/bin/su www

On the host www, any user in the

(will, wendy, and wim), may run any command as user www (which owns the web pages) or simply

to www.

ALL CDROM = NOPASSWD: /sbin/umount /CDROM,\ /sbin/mount -o nosuid\,nodev /dev/cd0a /CDROM

Any user may mount or unmount a CD-ROM on the machines in the CDROM

(orion, perseus, hercules) without entering a password. This is a bit tedious for users to type, so it is a prime candidate for encapsulating in a shell script.

It is generally not effective to

commands from

using the

operator. A user can trivially circumvent this by copying the desired command to a different name and then executing that. For example:

bill ALL = ALL, !SU, !SHELLS

Doesn't really prevent

from running the commands listed in

since he can simply copy those commands to a different name, or use a shell escape from an editor or other program. Therefore, these kind of restrictions should be considered advisory at best (and reinforced by policy).

In general, if a user has sudo

there is nothing to prevent them from creating their own program that gives them a root shell (or making their own copy of a shell) regardless of any

elements in the user specification.

If the

option is in use, it is not possible to reliably negate commands where the path name includes globbing (aka wildcard) characters. This is because the C library's

function cannot resolve relative paths. While this is typically only an inconvenience for rules that grant privileges, it can result in a security issue for rules that subtract or revoke privileges.

For example, given the following

file entry:

john ALL = /usr/bin/passwd [a-zA-Z0-9]*, /usr/bin/chsh [a-zA-Z0-9]*,\ /usr/bin/chfn [a-zA-Z0-9]*, !/usr/bin/* root

User

can still run

is enabled by changing to

and running

instead.

Once

executes a program, that program is free to do whatever it pleases, including run other programs. This can be a security issue since it is not uncommon for a program to allow shell escapes, which lets a user bypass

access control and logging. Common programs that permit shell escapes include shells (obviously), editors, paginators, mail, and terminal programs.

There are four basic approaches to this problem:

Avoid giving users access to commands that allow the user to run arbitrary commands. Many editors have a restricted mode where shell escapes are disabled, though

is a better solution to running editors via

Due to the large number of programs that offer shell escapes, restricting users to the set of programs that do not is often unworkable.

Many systems that support shared libraries have the ability to override default library functions by pointing an environment variable (usually

to an alternate shared library. On such systems,

functionality can be used to transparently intercept an attempt to run a new command, allow or deny it based on

rules, and log the result. For example, this can be used to restrict the commands run from within a privileged shell. Note, however, that this applies only to dynamically-linked executables. Statically-linked executables and executables running under binary emulation are not affected. Also, most shells support built-in commands and the ability to read or write sensitive files that cannot be intercepted by

Currently,

functionality only works for programs that use the

library functions to run the new command. This may be expanded in a future release of

Because most dynamic loaders ignore

(or the equivalent) when running set-user-ID and set-group-ID programs,

will not permit such programs to be run in

mode.

The

feature is known to work on Solaris, *BSD, Linux, macOS, HP-UX 11.x and AIX 5.3 and above. It should be supported on most operating systems that support the

environment variable. Check your operating system's manual pages for the dynamic linker (usually ld.so, ld.so.1, dyld, dld.sl, rld, or loader) to see if

is supported. It is

supported when

SELinux RBAC support is in use due to a fundamental incompatibility.

To enable intercept mode on a per-command basis, use the

tag as documented in the User Specification section above. Here is that example again:

chuck research = INTERCEPT: ALL

This allows user

to run any command on the machine

in intercept mode. Any commands run via shell escapes will be validated and logged by

If you are unsure whether or not your system is capable of supporting

you can always just try it out and check whether or not external commands run via a shell are logged when

is enabled.

There are two separate but related ways to log additional commands. The first is to enable I/O logging using the

flag. This will log the command's output but will not create an event log entry when the additional command is run. The second is to enable the

flag in

which will create an event log entry every time a new command is run. If I/O logging is also enabled, the log entry will include a time offset into the I/O log to indicate when the command was run. This offset can be passed to the

utility to replay the I/O log at the exact moment when the command was run. The

flag uses the same mechanism as

(see above) and has the same limitations.

functionality can be used to prevent a program run by

from executing any other programs. On most systems, it uses the same mechanism as

(see above) and thus the same caveats apply. The

functionality is capable of blocking execution of commands run via the

and

functions. On Linux, a

filter is used to implement

On Solaris 10 and higher,

uses Solaris privileges instead of the

environment variable.

To enable

for a command, use the

tag as documented in the User Specification section above. Here is that example again:

aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi

This allows user

to run

and

with

enabled. This will prevent those two commands from executing other commands (such as a shell). If you are unsure whether or not your system is capable of supporting

you can always just try it out and check whether shell escapes work when

is enabled.

Note that restricting shell escapes is not a panacea. Programs running as root are still capable of many potentially hazardous operations (such as changing or overwriting files) that could lead to unintended privilege escalation. In the specific case of an editor, a safer approach is to give the user permission to run

(see below).

The

plugin includes

support which allows users to securely edit files with the editor of their choice. As

is a built-in command, it must be specified in the

file without a leading path. However, it may take command line arguments just as a normal command does. Wildcards used in

command line arguments are expected to be path names, so a forward slash

will not be matched by a wildcard.

Unlike other

commands, the editor is run with the permissions of the invoking user and with the environment unmodified. More information may be found in the description of the

option in

For example, to allow user operator to edit the

file:

operator sudoedit /etc/motd

The operator user then runs

as follows:

$ sudoedit /etc/motd

The editor will run as the operator user, not root, on a temporary copy of

After the file has been edited,

will be updated with the contents of the temporary copy.

Users should

be granted

permission to edit a file that resides in a directory the user has write access to, either directly or via a wildcard. If the user has write access to the directory it is possible to replace the legitimate file with a link to another file, allowing the editing of arbitrary files. To prevent this, starting with version 1.8.16, symbolic links will not be followed in writable directories and

will refuse to edit a file located in a writable directory unless the

option has been disabled or the invoking user is root. Additionally, in version 1.8.15 and higher,

will refuse to open a symbolic link unless either the

option is enabled or the

command is prefixed with the

tag in the

file.

will check the ownership of its time stamp directory

by default

and ignore the directory's contents if it is not owned by root or if it is writable by a user other than root. Older versions of

stored time stamp files in

this is no longer recommended as it may be possible for a user to create the time stamp themselves on systems that allow unprivileged users to change the ownership of files they create.

While the time stamp directory

be cleared at reboot time, not all systems contain a

directory. To avoid potential problems,

will ignore time stamp files that date from before the machine booted on systems where the boot time is available.

Some systems with graphical desktop environments allow unprivileged users to change the system clock. Since

relies on the system clock for time stamp validation, it may be possible on such systems for a user to run

for longer than

by setting the clock back. To combat this,

uses a monotonic clock (which never moves backwards) for its time stamps if the system supports it.

will not honor time stamps set far in the future. Time stamps with a date greater than current_time + 2 *

will be ignored and

will log and complain.

If the

option is set to

the time stamp record includes the device number of the terminal the user authenticated with. This provides per-terminal granularity but time stamp records may still outlive the user's session.

Unless the

option is set to

the time stamp record also includes the session ID of the process that last authenticated. This prevents processes in different terminal sessions from using the same time stamp record. On systems where a process's start time can be queried, the start time of the session leader is recorded in the time stamp record. If no terminal is present or the

option is set to

the start time of the parent process is used instead. In most cases this will prevent a time stamp record from being re-used without the user entering a password when logging out and back in again.

Versions 1.8.4 and higher of the

plugin support a flexible debugging framework that can help track down what the plugin is doing internally if there is a problem. This can be configured in the

file.

The

plugin uses the same debug flag format as the

front-end:

The priorities used by

in order of decreasing severity, are:

and

Each priority, when specified, also includes all priorities higher than it. For example, a priority of

would include debug messages logged at

and higher.

The following subsystems are used by the

plugin:

and

processing

matches every subsystem

BSM and Linux audit code

user authentication

file

settings

environment handling

LDAP-based sudoers

logging support

matching of users, groups, hosts, and netgroups in the

file

network interface handling

network service switch handling in

file parsing

permission setting

The equivalent of

for the plugin.

pseudo-terminal related code

redblack tree internals

SSSD-based sudoers

utility functions

For example:

Debug sudoers.so /var/log/sudoers_debug match@info,nss@info

For more information, see the

manual.

Many people have worked on

over the years; this version consists of code written primarily by:

See the CONTRIBUTORS file in the

distribution https://www.sudo.ws/contributors.html for an exhaustive list of people who have contributed to

The

file should

be edited by the

utility which locks the file and checks for syntax errors. If

contains syntax errors,

may refuse to run, which is a serious problem if

is your only method of obtaining superuser privileges. Recent versions of

will attempt to recover after a syntax error by ignoring the rest of the line after encountering an error. Older versions of

will not run if

contains a syntax error.

When using netgroups of machines (as opposed to users), if you store fully qualified host name in the netgroup (as is usually the case), you either need to have the machine's host name be fully qualified as returned by the

command or use the

option in

If you feel you have found a bug in

please submit a bug report at https://bugzilla.sudo.ws/

Limited free support is available via the sudo-users mailing list, see https://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search the archives.

is provided

and any express or implied warranties, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose are disclaimed. See the LICENSE file distributed with

or https://www.sudo.ws/license.html for complete details.