NAME¶

sudoers — default sudo security policy module

DESCRIPTION¶

The sudoers policy module determines a user's sudo privileges. It is the default sudo policy plugin. The policy is driven by the /etc/sudoers file or, optionally in LDAP. The policy format is described in detail in the SUDOERS FILE FORMAT section. For information on storing sudoers policy information in LDAP, please see sudoers.ldap(5).

SUDOERS FILE FORMAT¶

The sudoers 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 sudoers 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.

Alias ::= 'User_Alias'  User_Alias (':' User_Alias)* |
          'Runas_Alias' Runas_Alias (':' Runas_Alias)* |
          'Host_Alias'  Host_Alias (':' Host_Alias)* |
          'Cmnd_Alias'  Cmnd_Alias (':' Cmnd_Alias)*

User_Alias ::= NAME '=' User_List

Runas_Alias ::= NAME '=' Runas_List

Host_Alias ::= NAME '=' Host_List

Cmnd_Alias ::= NAME '=' Cmnd_List

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

Alias_Type NAME = item1, item2, ...

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

User_List ::= User |
              User ',' User_List

User ::= '!'* user name |
         '!'* #uid |
         '!'* %group |
         '!'* %#gid |
         '!'* +netgroup |
         '!'* %:nonunix_group |
         '!'* %:#nonunix_gid |
         '!'* User_Alias

Runas_List ::= Runas_Member |
               Runas_Member ',' Runas_List

Runas_Member ::= '!'* user name |
                 '!'* #uid |
                 '!'* %group |
                 '!'* %#gid |
                 '!'* %:nonunix_group |
                 '!'* %:#nonunix_gid |
                 '!'* +netgroup |
                 '!'* Runas_Alias

Host_List ::= Host |
              Host ',' Host_List

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

Cmnd_List ::= Cmnd |
              Cmnd ',' Cmnd_List

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

Cmnd ::= '!'* command name |
         '!'* directory |
         '!'* "sudoedit" |
         '!'* Cmnd_Alias

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

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? SELinux_Spec? Tag_Spec* Cmnd

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

SELinux_Spec ::= ('ROLE=role' | 'TYPE=type')

Tag_Spec ::= ('NOPASSWD:' | 'PASSWD:' | 'NOEXEC:' | 'EXEC:' |
              'SETENV:' | 'NOSETENV:' | 'LOG_INPUT:' | 'NOLOG_INPUT:' |
              'LOG_OUTPUT:' | 'NOLOG_OUTPUT:')

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

$ sudo -u operator /bin/ls

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

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

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

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

$ sudo -g dialer /usr/bin/cu

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

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

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

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

/bin/ls [[alpha]]*

/usr/bin/*

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

$ sudo cat /var/log/messages.1

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

#include /etc/sudoers.local

#include sudoers.local

#include /etc/sudoers.%h

#includedir /etc/sudoers.d

ALL,!root

!root

SUDOERS OPTIONS¶

sudo's behavior can be modified by Default_Entry lines, as explained earlier. A list of all supported Defaults parameters, grouped by type, are listed below.

Boolean Flags:

always_set_home

If enabled, sudo will set the HOME environment variable to the home directory of the target user (which is root unless the -u option is used). This effectively means that the -H option is always implied. Note that HOME is already set when the the env_reset option is enabled, so always_set_home is only effective for configurations where either env_reset is disabled or HOME is present in the env_keep list. This flag is off by default.

authenticate

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 PASSWD and NOPASSWD tags. This flag is on by default.

closefrom_override

If set, the user may use sudo's -C option which overrides the default starting point at which sudo begins closing open file descriptors. This flag is off by default.

compress_io

If set, and sudo is configured to log a command's input or output, the I/O logs will be compressed using zlib. This flag is on by default when sudo is compiled with zlib support.

env_editor

If set, visudo will use the value of the EDITOR or VISUAL environment variables before falling back on the default editor list. Note that this may create a security hole as it allows the user to run any arbitrary command as root without logging. A safer alternative is to place a colon-separated list of editors in the editor variable. visudo will then only use the EDITOR or VISUAL if they match a value specified in editor. This flag is on by default.

env_reset

If set, sudo will run the command in a minimal environment containing the TERM, PATH, HOME, MAIL, SHELL, LOGNAME, USER, USERNAME and SUDO_* variables. Any variables in the caller's environment that match the env_keep and env_check lists are then added, followed by any variables present in the file specified by the env_file option (if any). The default contents of the env_keep and env_check lists are displayed when sudo is run by root with the -V option. If the secure_path option is set, its value will be used for the PATH environment variable. This flag is on by default.

fast_glob

Normally, sudo uses the glob(3) function to do shell-style globbing when matching path names. However, since it accesses the file system, glob(3) 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 fast_glob option causes sudo to use the fnmatch(3) function, which does not access the file system to do its matching. The disadvantage of fast_glob is that it is unable to match relative path names such as ./ls or ../bin/ls. 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 option should not be used when sudoers contains rules that contain negated path names which include globbing characters. This flag is off by default.

fqdn

Set this flag if you want to put fully qualified host names in the sudoers file when the local host name (as returned by the hostname 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 option is only effective when the “canonical” host name, as returned by the getaddrinfo() or gethostbyname() 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 /etc/hosts file in preference to DNS, the “canonical” host name may not be fully-qualified. The order that sources are queried for hosts name resolution is usually specified in the /etc/nsswitch.conf, /etc/netsvc.conf, /etc/host.conf, or, in some cases, /etc/resolv.conf file. In the /etc/hosts file, the first host name of the entry is considered to be the “canonical” name; subsequent names are aliases that are not used by sudoers. For example, the following hosts file line for the machine “xyzzy” has the fully-qualified domain name as the “canonical” host name, and the short version as an alias.

192.168.1.1 xyzzy.sudo.ws xyzzy

If the machine's hosts file entry is not formatted properly, the fqdn option will not be effective if it is queried before DNS.

Beware that when using DNS for host name resolution, turning on fqdn requires sudoers to make DNS lookups which renders sudo 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 “canonical” name as DNS knows it. That is, you may not use a host alias (CNAME entry) due to performance issues and the fact that there is no way to get all aliases from DNS.

This flag is off by default.

ignore_dot

If set, sudo will ignore "." or "" (both denoting current directory) in the PATH environment variable; the PATH itself is not modified. This flag is on by default.

ignore_local_sudoers

If set via LDAP, parsing of /etc/sudoers 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 /etc/sudoers. When this option is present, /etc/sudoers does not even need to exist. Since this option tells sudo how to behave when no specific LDAP entries have been matched, this sudoOption is only meaningful for the cn=defaults section. This flag is off by default.

insults

If set, sudo will insult users when they enter an incorrect password. This flag is off by default.

log_host

If set, the host name will be logged in the (non-syslog) sudo log file. This flag is off by default.

log_input

If set, sudo will run the command in a pseudo tty 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.

Input is logged to the directory specified by the iolog_dir option (/var/log/sudo-io by default) using a unique session ID that is included in the normal sudo log line, prefixed with “TSID=”. The iolog_file option may be used to control the format of the session ID.

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 log_output is all that is required.

log_output

If set, sudo will run the command in a pseudo tty and log all output that is sent to the screen, similar to the script(1) command. If the standard output or standard error is not connected to the user's tty, due to I/O redirection or because the command is part of a pipeline, that output is also captured and stored in separate log files.

Output is logged to the directory specified by the iolog_dir option (/var/log/sudo-io by default) using a unique session ID that is included in the normal sudo log line, prefixed with “TSID=”. The iolog_file option may be used to control the format of the session ID.

Output logs may be viewed with the sudoreplay(8) utility, which can also be used to list or search the available logs.

log_year

If set, the four-digit year will be logged in the (non-syslog) sudo log file. This flag is off by default.

long_otp_prompt

When validating with a One Time Password (OTP) scheme such as S/Key or OPIE, 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 off by default.

mail_always

Send mail to the mailto user every time a users runs sudo. This flag is off by default.

mail_badpass

Send mail to the mailto user if the user running sudo does not enter the correct password. If the command the user is attempting to run is not permitted by sudoers and one of the mail_always, mail_no_host, mail_no_perms or mail_no_user flags are set, this flag will have no effect. This flag is off by default.

mail_no_host

If set, mail will be sent to the mailto user if the invoking user exists in the sudoers file, but is not allowed to run commands on the current host. This flag is off by default.

mail_no_perms

If set, mail will be sent to the mailto user if the invoking user is allowed to use sudo but the command they are trying is not listed in their sudoers file entry or is explicitly denied. This flag is off by default.

mail_no_user

If set, mail will be sent to the mailto user if the invoking user is not in the sudoers file. This flag is on by default.

noexec

If set, all commands run via sudo will behave as if the NOEXEC tag has been set, unless overridden by a EXEC tag. See the description of NOEXEC and EXEC below as well as the Preventing shell escapes section at the end of this manual. This flag is off by default.

path_info

Normally, sudo will tell the user when a command could not be found in their PATH 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 PATH, sudo will tell the user that they are not allowed to run it, which can be confusing. This flag is on by default.

passprompt_override

The password prompt specified by passprompt will normally only be used if the password prompt provided by systems such as PAM matches the string “Password:”. If passprompt_override is set, passprompt will always be used. This flag is off by default.

preserve_groups

By default, sudo will initialize the group vector to the list of groups the target user is in. When preserve_groups 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 off by default.

pwfeedback

By default, sudo 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 sudo has hung at this point. When pwfeedback is set, sudo 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 off by default.

requiretty

If set, sudo will only run when the user is logged in to a real tty. When this flag is set, sudo can only be run from a login session and not via other means such as cron(8) or cgi-bin scripts. This flag is off by default.

root_sudo

If set, root is allowed to run sudo too. Disabling this prevents users from “chaining” sudo commands to get a root shell by doing something like “sudo sudo /bin/sh”. Note, however, that turning off root_sudo will also prevent root from running sudoedit. Disabling root_sudo provides no real additional security; it exists purely for historical reasons. This flag is on by default.

rootpw

If set, sudo will prompt for the root password instead of the password of the invoking user. This flag is off by default.

runaspw

If set, sudo will prompt for the password of the user defined by the runas_default option (defaults to root) instead of the password of the invoking user. This flag is off by default.

set_home

If enabled and sudo is invoked with the -s option the HOME environment variable will be set to the home directory of the target user (which is root unless the -u option is used). This effectively makes the -s option imply -H. Note that HOME is already set when the the env_reset option is enabled, so set_home is only effective for configurations where either env_reset is disabled or HOME is present in the env_keep list. This flag is off by default.

set_logname

Normally, sudo will set the LOGNAME, USER and USERNAME environment variables to the name of the target user (usually root unless the -u option is given). However, since some programs (including the RCS revision control system) use LOGNAME 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 if the env_reset option has not been disabled, entries in the env_keep list will override the value of set_logname. This flag is on by default.

set_utmp

When enabled, sudo will create an entry in the utmp (or utmpx) file when a pseudo-tty is allocated. A pseudo-tty is allocated by sudo when the log_input, log_output or use_pty flags are 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 on by default.

setenv

Allow the user to disable the env_reset option from the command line via the -E option. Additionally, environment variables set via the command line are not subject to the restrictions imposed by env_check, env_delete, or env_keep. As such, only trusted users should be allowed to set variables in this manner. This flag is off by default.

shell_noargs

If set and sudo is invoked with no arguments it acts as if the -s option had been given. That is, it runs a shell as root (the shell is determined by the SHELL 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 off by default.

stay_setuid

Normally, when sudo executes a command the real and effective UIDs are set to the target user (root by default). This option changes that behavior such that the real UID is left as the invoking user's UID. In other words, this makes sudo act as a setuid wrapper. This can be useful on systems that disable some potentially dangerous functionality when a program is run setuid. This option is only effective on systems that support either the setreuid(2) or setresuid(2) system call. This flag is off by default.

targetpw

If set, sudo will prompt for the password of the user specified by the -u option (defaults to root) instead of the password of the invoking user. In addition, the time stamp file name will include the target user's name. Note that this flag precludes the use of a uid not listed in the passwd database as an argument to the -u option. This flag is off by default.

tty_tickets

If set, users must authenticate on a per-tty basis. With this flag enabled, sudo will use a file named for the tty the user is logged in on in the user's time stamp directory. If disabled, the time stamp of the directory is used instead. This flag is on by default.

umask_override

If set, sudo will set the umask as specified by sudoers without modification. This makes it possible to specify a more permissive umask in sudoers than the user's own umask and matches historical behavior. If umask_override is not set, sudo will set the umask to be the union of the user's umask and what is specified in sudoers. This flag is off by default. If set, sudo will run the command in a pseudo-pty even if no I/O logging is being gone. A malicious program run under sudo could conceivably fork a background process that retains to the user's terminal device after the main program has finished executing. Use of this option will make that impossible. This flag is off by default.

utmp_runas

If set, sudo will store the name of the runas user when updating the utmp (or utmpx) file. By default, sudo stores the name of the invoking user. This flag is off by default.

visiblepw

By default, sudo will refuse to run if the user must enter a password but it is not possible to disable echo on the terminal. If the visiblepw flag is set, sudo will prompt for a password even when it would be visible on the screen. This makes it possible to run things like “ssh somehost sudo ls” since by default, ssh(1) does not allocate a tty when running a command. This flag is off by default.

Integers:

closefrom

Before it executes a command, sudo will close all open file descriptors other than standard input, standard output and standard error (ie: file descriptors 0-2). The closefrom option can be used to specify a different file descriptor at which to start closing. The default is 3.

passwd_tries

The number of tries a user gets to enter his/her password before sudo logs the failure and exits. The default is 3.

Integers that can be used in a boolean context:

loglinelen

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

passwd_timeout

Number of minutes before the sudo password prompt times out, or 0 for no timeout. The timeout may include a fractional component if minute granularity is insufficient, for example 2.5. The default is 5.

timestamp_timeout

Number of minutes that can elapse before sudo will ask for a passwd again. The timeout may include a fractional component if minute granularity is insufficient, for example 2.5. The default is 5. Set this to 0 to always prompt for a password. If set to a value less than 0 the user's time stamp will never expire. This can be used to allow users to create or delete their own time stamps via “sudo -v” and “sudo -k” respectively.

umask

Umask to use when running the command. Negate this option or set it to 0777 to preserve the user's umask. The actual umask that is used will be the union of the user's umask and the value of the umask option, which defaults to 0022. This guarantees that sudo never lowers the umask when running a command. Note: on systems that use PAM, the default PAM configuration may specify its own umask which will override the value set in sudoers.

Strings:

badpass_message

Message that is displayed if a user enters an incorrect password. The default is Sorry, try again. unless insults are enabled.

editor

A colon (‘:’) separated list of editors allowed to be used with visudo. visudo will choose the editor that matches the user's EDITOR environment variable if possible, or the first editor in the list that exists and is executable. The default is /usr/local/bin/vi.

iolog_dir

The top-level directory to use when constructing the path name for the input/output log directory. Only used if the log_input or log_output options are enabled or when the LOG_INPUT or LOG_OUTPUT tags are present for a command. The session sequence number, if any, is stored in the directory. The default is /var/log/sudo-io.

The following percent (‘%’) escape sequences are supported:

%{seq}

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. 01/00/A5

%{user}

expanded to the invoking user's login name

%{group}

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

%{runas_user}

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

%{runas_group}

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

%{hostname}

expanded to the local host name without the domain name

%{command}

expanded to the base name of the command being run

In addition, any escape sequences supported by the system's strftime(3) function will be expanded.

To include a literal ‘%’ character, the string ‘%%’ should be used.

iolog_file

The path name, relative to iolog_dir, in which to store input/output logs when the log_input or log_output options are enabled or when the LOG_INPUT or LOG_OUTPUT tags are present for a command. Note that iolog_file may contain directory components. The default is “%{seq}”.

See the iolog_dir option above for a list of supported percent (‘%’) escape sequences.

In addition to the escape sequences, path names that end in six or more Xs will have the Xs replaced with a unique combination of digits and letters, similar to the mktemp(3) function.

mailsub

Subject of the mail sent to the mailto user. The escape %h will expand to the host name of the machine. Default is “*** SECURITY information for %h ***”.

noexec_file

This option is no longer supported. The path to the noexec file should now be set in the /etc/sudo.conf file.

pam_login_service

On systems that use PAM for authentication, this is the service name used when the -i option is specified. The default value is “sudo-i”. See the description of pam_service for more information.

pam_service

On systems that use PAM for authentication, the service name specifies the PAM policy to apply. This usually corresponds to an entry in the pam.conf file or a file in the /etc/pam.d directory. The default value is “sudo”.

passprompt

The default prompt to use when asking for a password; can be overridden via the -p option or the SUDO_PROMPT environment variable. The following percent (‘%’) escape sequences are supported:

%H

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

%h

expanded to the local host name without the domain name

%p

expanded to the user whose password is being asked for (respects the rootpw, targetpw and runaspw flags in sudoers)

%U

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

%u

expanded to the invoking user's login name

%%

two consecutive % characters are collapsed into a single % character

The default value is “[sudo] password for %p:”. The default SELinux role to use when constructing a new security context to run the command. The default role may be overridden on a per-command basis in sudoers or via command line options. This option is only available when sudo is built with SELinux support.

runas_default

The default user to run commands as if the -u option is not specified on the command line. This defaults to root.

syslog_badpri

Syslog priority to use when user authenticates unsuccessfully. Defaults to alert.

The following syslog priorities are supported: alert, crit, debug, emerg, err, info, notice, and warning.

syslog_goodpri

Syslog priority to use when user authenticates successfully. Defaults to notice.

See syslog_badpri for the list of supported syslog priorities.

sudoers_locale

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 “C”.

timestampdir

The directory in which sudo stores its time stamp files. The default is /var/db/sudo.

timestampowner

The owner of the time stamp directory and the time stamps stored therein. The default is root.

type

The default SELinux type to use when constructing a new security context to run the command. The default type may be overridden on a per-command basis in sudoers or via command line options. This option is only available when sudo is built with SELinux support.

Strings that can be used in a boolean context:

env_file

The env_file 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 “VARIABLE=value” or “export VARIABLE=value”. The value may optionally be surrounded by single or double quotes. Variables in this file are subject to other sudo environment settings such as env_keep and env_check.

exempt_group

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.

group_plugin

A string containing a sudoers group plugin with optional arguments. This can be used to implement support for the nonunix_group syntax described earlier. The string should consist of the plugin path, either fully-qualified or relative to the /usr/libexec 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 example, given /etc/sudo-group, a group file in Unix group format, the sample group plugin can be used:

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

For more information see sudo_plugin(5).

lecture

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

always

Always lecture the user.

never

Never lecture the user.

once

Only lecture the user the first time they run sudo.

If no value is specified, a value of once is implied. Negating the option results in a value of never being used. The default value is once.

lecture_file

Path to a file containing an alternate sudo lecture that will be used in place of the standard lecture if the named file exists. By default, sudo uses a built-in lecture.

listpw

This option controls when a password will be required when a user runs sudo with the -l option. It has the following possible values:

all

All the user's sudoers entries for the current host must have the NOPASSWD flag set to avoid entering a password.

always

The user must always enter a password to use the -l option.

any

At least one of the user's sudoers entries for the current host must have the NOPASSWD flag set to avoid entering a password.

never

The user need never enter a password to use the -l option.

If no value is specified, a value of any is implied. Negating the option results in a value of never being used. The default value is any.

logfile

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

mailerflags

Flags to use when invoking mailer. Defaults to -t.

mailerpath

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

mailfrom

Address to use for the “from” address when sending warning and error mail. The address should be enclosed in double quotes ("") to protect against sudo interpreting the @ sign. Defaults to the name of the user running sudo.

mailto

Address to send warning and error mail to. The address should be enclosed in double quotes ("") to protect against sudo interpreting the @ sign. Defaults to root.

secure_path

Path used for every command run from sudo. If you don't trust the people running sudo to have a sane PATH environment variable you may want to use this. Another use is if you want to have the “root path” be separate from the “user path”. Users in the group specified by the exempt_group option are not affected by secure_path. This option is not set by default.

syslog

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

The following syslog facilities are supported: authpriv (if your OS supports it), auth, daemon, user, local0, local1, local2, local3, local4, local5, local6, and local7.

verifypw

This option controls when a password will be required when a user runs sudo with the -v option. It has the following possible values:

all

All the user's sudoers entries for the current host must have the NOPASSWD flag set to avoid entering a password.

always

The user must always enter a password to use the -v option.

any

At least one of the user's sudoers entries for the current host must have the NOPASSWD flag set to avoid entering a password.

never

The user need never enter a password to use the -v option.

If no value is specified, a value of all is implied. Negating the option results in a value of never being used. The default value is all.

Lists that can be used in a boolean context:

env_check

Environment variables to be removed from the user's environment if unless they are considered “safe”. For all variables except TZ, “safe” means that the variable's value does not contain any ‘%’ or ‘/’ characters. This can be used to guard against printf-style format vulnerabilities in poorly-written programs. The TZ variable is considerd 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 zoneinfo directory.
• It contains a .. path element.
• It contains white space or non-printable characters.
• It is longer than the value of PATH_MAX.

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 env_reset option is enabled or disabled, variables specified by env_check will be preserved in the environment if they pass the aforementioned check. The default list of environment variables to check is displayed when sudo is run by root with the -V option.

env_delete

Environment variables to be removed from the user's environment when the env_reset 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 default list of environment variables to remove is displayed when sudo is run by root with the -V option. Note that many operating systems will remove potentially dangerous variables from the environment of any setuid process (such as sudo).

env_keep

Environment variables to be preserved in the user's environment when the env_reset option is in effect. This allows fine-grained control over the environment sudo-spawned 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 default list of variables to keep is displayed when sudo is run by root with the -V option.

LOG FORMAT¶

sudoers can log events using either syslog(3) or a simple log file. In each case the log format is almost identical.

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

SUDO.CONF¶

The /etc/sudo.conf file determines which plugins the sudo front end will load. If no /etc/sudo.conf file is present, or it contains no Plugin lines, sudo will use the sudoers security policy and I/O logging, which corresponds to the following /etc/sudo.conf file.

#
# Default /etc/sudo.conf file
#
# Format:
#   Plugin plugin_name plugin_path plugin_options ...
#   Path askpass /path/to/askpass
#   Path noexec /path/to/sudo_noexec.so
#   Debug sudo /var/log/sudo_debug all@warn
#   Set disable_coredump true
#
# The plugin_path is relative to /usr/libexec unless
#   fully qualified.
# The plugin_name corresponds to a global symbol in the plugin
#   that contains the plugin interface structure.
# The plugin_options are optional.
#
Plugin policy_plugin sudoers.so
Plugin io_plugin sudoers.so

Plugin sudoers_policy sudoers.so sudoers_file=/etc/sudoers sudoers_uid=0 sudoers_gid=0 sudoers_mode=0440

FILES¶

/etc/sudo.conf

Sudo front end configuration

/etc/sudoers

List of who can run what

/etc/group

Local groups file

/etc/netgroup

List of network groups

/var/log/sudo-io

I/O log files

/var/db/sudo

Directory containing time stamps for the sudoers security policy

/etc/environment

Initial environment for -i mode on AIX and Linux systems

EXAMPLES¶

Below are example sudoers entries. Admittedly, some of these are a bit contrived. First, we allow a few environment variables to pass and then define our aliases:

# 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	WEBMASTERS = 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 = master, 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
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 sudo to log via syslog(3) using the auth facility in all cases. We don't want to subject the full time staff to the sudo lecture, user millert need not give a password, and we don't want to reset the LOGNAME, USER or USERNAME environment variables when running commands as root. Additionally, on the machines in the SERVERS Host_Alias, 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 Cmnd_Alias (/usr/bin/more, /usr/bin/pg and /usr/bin/less).

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

The User specification is the part that actually determines who may run what.

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

We let root and any user in group wheel run any command on any host as any user.

FULLTIMERS	ALL = NOPASSWD: ALL

Full time sysadmins (millert, mikef, and dowdy) may run any command on any host without authenticating themselves.

PARTTIMERS	ALL = ALL

Part time sysadmins bostley, jwfox, and crawl) may run any command on any host but they must authenticate themselves first (since the entry lacks the NOPASSWD tag).

jack		CSNETS = ALL

The user jack may run any command on the machines in the CSNETS alias (the networks 128.138.243.0, 128.138.204.0, and 128.138.242.0). Of those networks, only 128.138.204.0 has an explicit netmask (in CIDR notation) indicating it is a class C network. For the other networks in CSNETS, the local machine's netmask will be used during matching.

lisa		CUNETS = ALL

The user lisa may run any command on any host in the CUNETS alias (the class B network 128.138.0.0).

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

The operator 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 /usr/oper/bin/.

joe		ALL = /usr/bin/su operator

The user joe may only su(1) to operator.

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

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

Users in the opers group may run commands in /usr/sbin/ as themselves with any group in the ADMINGRP Runas_Alias (the adm and oper groups).

The user pete is allowed to change anyone's password except for root on the HPPA machines. Note that this assumes passwd(1) does not take multiple user names on the command line.

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

The user bob may run anything on the SPARC and SGI machines as any user listed in the OP Runas_Alias (root and operator.)

jim		+biglab = ALL

The user jim may run any command on machines in the biglab netgroup. sudo knows that “biglab” is a netgroup due to the ‘+’ prefix.

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

Users in the secretaries 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 fred can run commands as any user in the DB Runas_Alias (oracle or sybase) without giving a password.

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

On the ALPHA machines, user john may su to anyone except root but he is not allowed to specify any options to the su(1) command.

jen		ALL, !SERVERS = ALL

The user jen may run any command on any machine except for those in the SERVERS Host_Alias (master, mail, www and ns).

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

For any machine in the SERVERS Host_Alias, jill may run any commands in the directory /usr/bin/ except for those commands belonging to the SU and SHELLS Cmnd_Aliases.

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

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

matt		valkyrie = KILL

On his personal workstation, valkyrie, matt needs to be able to kill hung processes.

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

On the host www, any user in the WEBMASTERS User_Alias (will, wendy, and wim), may run any command as user www (which owns the web pages) or simply su(1) to www.

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

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

SECURITY NOTES¶

bill	ALL = ALL, !SU, !SHELLS

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

SEE ALSO¶

ssh(1), su(1), fnmatch(3), glob(3), mktemp(3), strftime(3), sudoers.ldap(5), sudo_plugin(8), sudo(8), visudo(8)

CAVEATS¶

The sudoers file should always be edited by the visudo command which locks the file and does grammatical checking. It is imperative that sudoers be free of syntax errors since sudo will not run with a syntactically incorrect sudoers file.

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 hostname command or use the fqdn option in sudoers.

BUGS¶

If you feel you have found a bug in sudo, please submit a bug report at http://www.sudo.ws/sudo/bugs/

SUPPORT¶

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

DISCLAIMER¶

sudo is provided “AS IS” 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 sudo or http://www.sudo.ws/sudo/license.html for complete details.