NAME¶

sudoers — default sudo security policy plugin

DESCRIPTION¶

The sudoers policy plugin 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).

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

Plugin sudoers_audit sudoers.so sudoers_mode=0400 error_recovery=false

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

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 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.

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]_)*

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

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

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

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

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? Option_Spec* Tag_Spec* Cmnd

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

Option_Spec ::= (SELinux_Spec | Date_Spec | Timeout_Spec | Chdir_Spec | Chroot_Spec)

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

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

Timeout_Spec ::= 'TIMEOUT=timeout'

Chdir_Spec ::= 'CWD=directory'

Chroot_Spec ::= 'CHROOT=directory'

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

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

20170214083000Z
2017021408Z
20160315220000-0500
20151201235900

/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_query_group_plugin

If a group_plugin 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 group_plugin. This flag is off by default.

always_set_home

If enabled, sudo will set the HOME environment variable to the home directory of the target user (which is the root user unless the -u option is used). This flag is largely obsolete and has no effect unless the env_reset flag has been disabled or HOME is present in the env_keep list, both of which are strongly discouraged. 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.

case_insensitive_group

If enabled, group names in sudoers will be matched in a case insensitive manner. This may be necessary when users are stored in LDAP or AD. This flag is on by default.

case_insensitive_user

If enabled, user names in sudoers will be matched in a case insensitive manner. This may be necessary when groups are stored in LDAP or AD. This flag is on by default.

closefrom_override

If set, the user may use the -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.

exec_background

By default, sudo runs a command as the foreground process as long as sudo itself is running in the foreground. When the exec_background flag is enabled and the command is being run in a pseudo-terminal (due to I/O logging or the use_pty 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 SIGTTIN signal (or SIGTTOU in the case of terminal settings). If this happens when sudo 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 sudo 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 sudo 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 tcgetattr() and tcsetattr() system calls (this is a bug in macOS). Furthermore, because this behavior depends on the command stopping with the SIGTTIN or SIGTTOU signals, programs that catch these signals and suspend themselves with a different signal (usually SIGTOP) will not be automatically foregrounded. Some versions of the linux su(1) command behave this way. This flag is off 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 use_pty flag is enabled.

env_editor

If set, visudo will use the value of the SUDO_EDITOR, VISUAL or EDITOR environment variables before falling back on the default editor list. Note that visudo is typically run as root so this flag may allow a user with visudo privileges to run arbitrary commands as root without logging. An alternative is to place a colon-separated list of “safe” editors int the editor variable. visudo will then only use SUDO_EDITOR, VISUAL or EDITOR if they match a value specified in editor. If the env_reset flag is enabled, the SUDO_EDITOR, VISUAL and/or EDITOR environment variables must be present in the env_keep list for the env_editor flag to function when visudo is invoked via sudo. 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 and SUDO_* variables. Any variables in the caller's environment or in the file specified by the restricted_env_file setting 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 setting (if any). The contents of the env_keep and env_check lists, as modified by global Defaults parameters in sudoers, are displayed when sudo is run by root with the -V option. If the secure_path setting is enabled, 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 flag 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 flag should not be used when the sudoers file 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 flag 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 host 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 flag 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_audit_errors

Allow commands to be run even if sudoers 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 sudoers supports audit logging, including FreeBSD, Linux, macOS and Solaris. This flag is on 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_iolog_errors

Allow commands to be run even if sudoers 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 off by default.

ignore_logfile_errors

Allow commands to be run even if sudoers 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 sudoers is configured to use file-based logging via the logfile setting. 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 flag is enabled, /etc/sudoers does not even need to exist. Since this flag 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.

ignore_unknown_defaults

If set, sudo will not produce a warning if it encounters an unknown Defaults entry in the sudoers file or an unknown sudoOption in LDAP. 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_allowed

If set, sudoers 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 on by default.

This setting is only supported by version 1.8.29 or higher.

log_denied

If set, sudoers 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 on by default.

This setting is only supported by version 1.8.29 or higher.

log_host

If set, the host name will be included in log entries written to the file configured by the logfile setting. This flag is off by default.

log_input

If set, sudo 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 sudo is actually reading the standard input. This may have unexpected results when using sudo in a shell script that expects to process the standard input. For more information about I/O logging, see the I/O LOG FILES section. This flag is off by default.

log_output

If set, sudo will run the command in a pseudo-terminal and log all output that is sent to the screen, similar to the script(1) command. For more information about I/O logging, see the I/O LOG FILES section. This flag is off by default.

log_server_keepalive

If set, sudo 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 ignore_iolog_errors flag (I/O logging enabled) or the ignore_log_errors flag (I/O logging disabled) is set. This flag is on by default.

This setting is only supported by version 1.9.0 or higher.

log_server_verify

If set, the server certificate received during the TLS handshake must be valid and it must contain either the server name (from log_servers) or its IP address. If either of these conditions is not met, the TLS handshake will fail. This flag is on by default.

This setting is only supported by version 1.9.0 or higher.

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_all_cmnds

Send mail to the mailto user every time a user attempts to run a command via sudo (this includes sudoedit). No mail will be sent if the user runs sudo with the -l or -v option unless there is an authentication error and the mail_badpass flag is also set. This flag is off by default.

mail_always

Send mail to the mailto user every time a user 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_all_cmnds, 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.

match_group_by_gid

By default, sudoers 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 sudoers file. This works well on systems where the number of groups listed in the sudoers 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 sudoers file is relatively small, it may be prohibitively expensive and running commands via sudo may take longer than normal. On such systems it may be faster to use the match_group_by_gid flag to avoid resolving the user's group-IDs to group names. In this case, sudoers must look up any group name listed in the sudoers 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 match_group_by_gid is enabled, group database lookups performed by sudoers 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 /etc/group file and the remote group database. On such systems, enabling or disabling match_group_by_gid 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 match_group_by_gid flag has no effect when sudoers data is stored in LDAP. This flag is off by default.

This setting is only supported by version 1.8.18 or higher.

netgroup_tuple

If set, netgroup lookups will be performed using the full netgroup tuple: host name, user name and domain (if one is set). Historically, sudo only matched the user name and domain for netgroups used in a User_List and only matched the host name and domain for netgroups used in a Host_List. This flag is off by default.

noexec

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

pam_acct_mgmt

On systems that use PAM for authentication, sudo 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 on by default.

This setting is only supported by version 1.8.28 or higher.

pam_rhost

On systems that use PAM for authentication, sudo will set the PAM remote host value to the name of the local host when the pam_rhost flag is enabled. On Linux systems, enabling pam_rhost may result in DNS lookups of the local host name when PAM is initialized. On Solaris versions prior to Solaris 8, pam_rhost must be enabled if pam_ruser is also enabled to avoid a crash in the Solaris PAM implementation.

This flag is off by default on systems other than Solaris.

This setting is only supported by version 1.9.0 or higher.

pam_ruser

On systems that use PAM for authentication, sudo will set the PAM remote user value to the name of the user that invoked sudo when the pam_ruser flag is enabled. This flag is on by default.

This setting is only supported by version 1.9.0 or higher.

pam_session

On systems that use PAM for authentication, sudo will create a new PAM session for the command to be run in. Unless sudo is given the -i or -s options, PAM session modules are run with the “silent” flag enabled. This prevents last login information from being displayed for every command on some systems. Disabling pam_session 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 pam_session, pam_setcred, and use_pty are disabled, log_servers has not been set and I/O logging has not been configured, sudo will execute the command directly instead of running it as a child process. This flag is on by default.

This setting is only supported by version 1.8.7 or higher.

pam_setcred

On systems that use PAM for authentication, sudo 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 pam_session, pam_setcred, and use_pty are disabled, log_servers has not been set and I/O logging has not been configured, sudo will execute the command directly instead of running it as a child process. This flag is on by default.

This setting is only supported by version 1.8.8 or higher.

passprompt_override

If set, the prompt specified by passprompt or the SUDO_PROMPT environment variable will always be used and will replace the prompt provided by a PAM module or other authentication method. 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.

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 when running a command or editing a file. This flag is off by default.

runas_allow_unknown_id

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 Runas_List, this option also allows the ALL alias to match unknown IDs. This flag is off by default.

This setting is only supported by version 1.8.30 or higher. Older versions of sudo always allowed matching of unknown user and group IDs.

runas_check_shell

If enabled, sudo will only run commands as a user whose shell appears in the /etc/shells file, even if the invoking user's Runas_List would otherwise permit it. If no /etc/shells file is present, a system-dependent list of built-in default shells is used. On many operating systems, system users such as “bin”, do not have a valid shell and this flag can be used to prevent commands from being run as those users. This flag is off by default.

This setting is only supported by version 1.8.30 or higher.

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 when running a command or editing a file. This flag is off by default.

selinux

If enabled, the user may specify an SELinux role and/or type to use when running the command, as permitted by the SELinux policy. If SELinux is disabled on the system, this flag has no effect. This flag is on 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 the root user unless the -u option is used). This flag is largely obsolete and has no effect unless the env_reset flag has been disabled or HOME is present in the env_keep list, both of which are strongly discouraged. This flag is off by default.

set_logname

Normally, sudo will set the LOGNAME and USER 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 set_logname will have no effect if the env_reset option has not been disabled and the env_keep list contains LOGNAME or USER. This flag is on by default.

set_utmp

When enabled, sudo will create an entry in the utmp (or utmpx) file when a pseudo-terminal is allocated. A pseudo-terminal is allocated by sudo when it is running in a terminal and one or more of the log_input, log_output or use_pty 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 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 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 setreuid(2) or setresuid(2) system call. This flag is off by default.

sudoedit_checkdir

If set, sudoedit 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 sudoedit will refuse to edit a file located in a writable directory. These restrictions are not enforced when sudoedit is run by root. On some systems, if all directory components of the path to be edited are not readable by the target user, sudoedit will be unable to edit the file. This flag is on 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.

sudoedit_follow

By default, sudoedit will not follow symbolic links when opening files. The sudoedit_follow option can be enabled to allow sudoedit to open symbolic links. It may be overridden on a per-command basis by the FOLLOW and NOFOLLOW tags. This flag is off by default.

This setting is only supported by version 1.8.15 or higher.

syslog_pid

When logging via syslog(3), include the process ID in the log entry. This flag is off by default.

This setting is only supported by version 1.8.21 or higher.

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 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 -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 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 timestamp_type option.

umask_override

If set, sudo will set the umask as specified in the sudoers file without modification. This makes it possible to specify a umask in the sudoers file that is more permissive 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.

use_netgroups

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 NETGROUP_BASE directive is present in the /etc/sudo-ldap.conf file. If netgroups are not needed, this option can be disabled to reduce the load on the LDAP server. This flag is on by default.

use_pty

If set, and sudo 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 sudo process is not attached to a terminal, use_pty has no effect.

A malicious program run under sudo 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 off by default.

user_command_timeouts

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 sudoers file and on the command line, the smaller of the two timeouts will be used. See the Timeout_Spec section for a description of the timeout syntax. This flag is off by default.

This setting is only supported by version 1.8.20 or higher.

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.

command_timeout

The maximum amount of time a command is allowed to run before it is terminated. See the Timeout_Spec section for a description of the timeout syntax.

This setting is only supported by version 1.8.20 or higher.

log_server_timeout

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

maxseq

The maximum sequence number that will be substituted for the “%{seq}” escape in the I/O log file (see the iolog_dir description below for more information). While the value substituted for “%{seq}” is in base 36, maxseq itself should be expressed in decimal. Values larger than 2176782336 (which corresponds to the base 36 sequence number “ZZZZZZ”) will be silently truncated to 2176782336. The default value is 2176782336.

Once the local sequence number reaches the value of maxseq, it will “roll over” to zero, after which sudoers will truncate and re-use any existing I/O log path names.

This setting is only supported by version 1.8.7 or higher.

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.

syslog_maxlen

On many systems, syslog(3) 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, sudoers creates log messages up to 980 bytes which corresponds to the historic BSD syslog implementation which used a 1024 byte buffer to store the message, date, hostname and program name. To prevent syslog messages from being truncated, sudoers will split up log messages that are larger than syslog_maxlen bytes. When a message is split, additional parts will include the string “(command continued)” after the user name and before the continued command line arguments.

This setting is only supported by version 1.8.19 or higher.

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 not expire until the system is rebooted. This can be used to allow users to create or delete their own time stamps via “sudo -v” and “sudo -k” respectively.

umask

File mode creation mask to use when running the command. Negate this option or set it to 0777 to prevent sudoers from changing the umask. Unless the umask_override flag is set, the actual umask will be the union of the user's umask and the value of the umask setting, which defaults to 0022. This guarantees that sudo never lowers the umask when running a command.

If umask is explicitly set in sudoers, it will override any umask setting in PAM or login.conf. If umask is not set in sudoers, the umask specified by PAM or login.conf will take precedence. The umask setting in PAM is not used for sudoedit, which does not create a new PAM session.

Strings:

authfail_message

Message that is displayed after a user fails to authenticate. The message may include the ‘%d’ escape which will expand to the number of failed password attempts. If set, it overrides the default message, %d incorrect password attempt(s).

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 path names used by sudoedit and visudo. For sudoedit, this list is used to find an editor when none of the SUDO_EDITOR, VISUAL or EDITOR environment variables are set to an editor that exists and is executable. For visudo, it is used as a white list of allowed editors; visudo will choose the editor that matches the user's SUDO_EDITOR, VISUAL or EDITOR environment variable if possible, or the first editor in the list that exists and is executable if not. Unless invoked as sudoedit, sudo does not preserve the SUDO_EDITOR, VISUAL or EDITOR environment variables unless they are present in the env_keep list or the env_reset option is disabled. The default is /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.

If the path created by concatenating iolog_dir and iolog_file already exists, the existing I/O log file will be truncated and overwritten unless iolog_file ends in six or more Xs.

iolog_flush

If set, sudo 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 off by default.

This setting is only supported by version 1.8.20 or higher.

iolog_group

The group name to look up when setting the group-ID on new I/O log files and directories. If iolog_group is not set, the primary group-ID of the user specified by iolog_user is used. If neither iolog_group nor iolog_user 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.

iolog_mode

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

This setting is only supported by version 1.8.19 or higher.

iolog_user

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

lecture_status_dir

The directory in which sudo stores per-user lecture status files. Once a user has received the lecture, a zero-length file is created in this directory so that sudo will not lecture the user again. This directory should not be cleared when the system reboots. The default is /var/db/sudo/lectured.

log_server_cabundle

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

This setting is only supported by version 1.9.0 or higher.

log_server_peer_cert

The path to the client's certificate file, in PEM format. This setting is required when log_servers is set and the remote log server is secured with TLS.

This setting is only supported by version 1.9.0 or higher.

log_server_peer_key

The path to the client's private key file, in PEM format. This setting is required when log_servers is set and the remote log server is secured with TLS.

This setting is only supported by version 1.9.0 or higher.

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

As of sudo version 1.8.1 this option is no longer supported. The path to the noexec file should now be set in the sudo.conf(5) 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.

This setting is only supported by version 1.8.8 or higher.

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”.

This setting is only supported by version 1.8.8 or higher.

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

On systems that use PAM for authentication, passprompt will only be used if the prompt provided by the PAM module matches the string “Password: ” or “username's Password: ”. This ensures that the passprompt setting does not interfere with challenge-response style authentication. The passprompt_override flag can be used to change this behavior.

The default value is “[sudo] password for %p: ”.

role

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 the sudoers file 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.

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”.

timestamp_type

sudoers uses per-user time stamp files for credential caching. The timestamp_type option can be used to specify the type of time stamp record used. It has the following possible values:

global

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

ppid

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 timestamp_timeout minutes (5 by default). Commands run via sudo with a different parent process ID, for example from a shell script, will be authenticated separately.

tty

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 ppid. Commands run from the same terminal will not require a password for timestamp_timeout minutes (5 by default).

kernel

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

The default value is tty.

This setting is only supported by version 1.8.21 or higher.

timestampdir

The directory in which sudo stores its time stamp files. This directory should be cleared when the system reboots. The default is /run/sudo/ts.

timestampowner

The owner of the lecture status directory, time stamp directory and all files 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 the sudoers file 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 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 sudo environment restrictions 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.

fdexec

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

always

Always execute by file descriptor.

never

Never execute by file descriptor.

digest_only

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

The default value is digest_only. 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 fdexec 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, /dev/fd/4 on Solaris and /proc/self/fd/4 on Linux. A workaround is to use the SUDO_COMMAND environment variable instead.

The fdexec 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 ALL alias.

This setting is only supported by version 1.8.20 or higher. If the operating system does not support the fexecve(2) system call, this setting has no effect.

group_plugin

A string containing a sudoers group plugin with optional arguments. The string should consist of the plugin path, either fully-qualified or relative to the /usr/libexec/sudo 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 GROUP PROVIDER PLUGINS.

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 file 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 file 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.

log_format

The event log format. Supported log formats are:

json

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 syslog may be truncated.

sudo

Traditional sudo-style logs, see LOG FORMAT for a description of the log file format.

This setting affects logs sent via syslog(3) as well as the file specified by the logfile setting, if any. The default value is sudo.

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.

restricted_env_file

The restricted_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 enclosed in single or double quotes. Variables in this file are only added if the variable does not already exist in the environment. Unlike env_file, the file's contents are not trusted and are processed in a manner similar to that of the invoking user's environment. If env_reset is enabled, variables in the file will only be added if they are matched by either the env_check or env_keep list. If env_reset is disabled, variables in the file are added as long as they are not matched by the env_delete list. In either case, the contents of restricted_env_file are processed before the contents of env_file.

runchroot

If set, sudo 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 sudo's -R option. See the Chroot_Spec section for more details.

It is only possible to use runchroot 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 Cmnd_Spec that includes a Chroot_Spec.

This setting is only supported by version 1.9.3 or higher.

runcwd

If set, sudo 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 sudo's -D option. See the Chdir_Spec section for more details.

This setting is only supported by version 1.9.3 or higher.

secure_path

If set, sudo will use this value in place of the user's PATH environment variable. This option can be used to reset the PATH to a known good value that contains directories for system administrator commands such as /usr/sbin.

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.

syslog_badpri

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

The following syslog priorities are supported: alert, crit, debug, emerg, err, info, notice, warning, and none. Negating the option or setting it to a value of none will disable logging of unsuccessful commands.

syslog_goodpri

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

See syslog_badpri for the list of supported syslog priorities. Negating the option or setting it to a value of none will disable logging of successful commands.

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 file 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 file 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 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 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 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 global 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 global 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 set-user-ID 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 global list of variables to keep is displayed when sudo is run by root with the -V option.

Preserving the HOME environment variable has security implications since many programs use it when searching for configuration or data files. Adding HOME to env_keep may enable a user to run unrestricted commands via sudo and is strongly discouraged. Users wishing to edit files with sudo should run sudoedit (or sudo -e) to get their accustomed editor configuration instead of invoking the editor directly.

log_servers

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 sudo_logsrvd or another service that implements the protocol described by sudo_logsrv.proto(5).

Server addresses should be of the form “host[:port][(tls)]”. The host portion may be a host name, an IPv4 address, or an IPv6 address in square brackets.

If the optional tls 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 log_servers is set, event log data will be logged both locally (see the syslog and log_file 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 ignore_iolog_errors flag (I/O logging enabled) or the ignore_log_errors flag (I/O logging disabled) is set. Likewise, if the connection to the log server is interrupted while sudo is running, the command will be terminated unless the ignore_iolog_errors flag (I/O logging enabled) or the ignore_log_errors flag (I/O logging disabled) is set.

This setting is only supported by version 1.9.0 or higher.

GROUP PROVIDER PLUGINS¶

The sudoers 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 nonunix_group syntax described earlier.

Group provider plugins are specified via the group_plugin setting. The argument to group_plugin should consist of the plugin path, either fully-qualified or relative to the /usr/libexec/sudo 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:

group_file

The group_file plugin supports an alternate group file that uses the same syntax as the /etc/group 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 /etc/sudo-group:

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

system_group

The system_group plugin supports group lookups via the standard C library functions getgrnam() and getgrid(). 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 sudo_plugin(5).

LOG FORMAT¶

sudoers can log events in either JSON or sudo format, this section describes the sudo log format. Depending on sudoers configuration, sudoers can log events via syslog(3), to a local log file, or both. The log format is almost identical in both cases. Any control characters present in the log data are formatted in octal with a leading ‘#’ character. For example, a horizontal tab is stored as ‘#011’ and an embedded carriage return is stored as ‘#015’. In addition, space characters in the command path are stored as ‘#040’. Command line arguments that contain spaces are enclosed in single quotes (''). This makes it possible to distinguish multiple command line arguments from a single argument that contains spaces. Literal single quotes and backslash characters (‘\’) in command line arguments are escaped with a backslash.

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

I/O LOG FILES¶

When I/O logging is enabled, sudo 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 iolog_dir option (/var/log/sudo-io by default) using a unique session ID that is included in the sudo log line, prefixed with “TSID=”. The iolog_file option may be used to control the format of the session ID. For remote logs, the log_servers setting is used to specify one or more log servers running sudo_logsrvd or another server that implements the protocol described by sudo_logsrv.proto(5).

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

log

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

log.json

A JSON-formatted file containing information about the command. This is similar to the log file but contains additional information and is easily extensible. The log.json file will be used by sudoreplay(8) in preference to the log file if it exists. The file may contain the following elements:

timestamp

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

columns

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

command

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

lines

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

runargv

A JSON array representing the command's argument vector as passed to the execve(2) system call.

runenv

A JSON array representing the command's environment as passed to the execve(2) system call.

rungid

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

rungroup

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

runuid

The user ID the command ran as.

runuser

The name of the user the command ran as.

submitcwd

The current working directory at the time sudo was run.

submithost

The name of the host the command was run on.

submituser

The name of the user who ran the command via sudo.

ttyname

The path name of the terminal the user invoked sudo from. If the command was run in a pseudo-terminal, ttyname will be different from the terminal the command actually ran in.

timing

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:

0

standard input, number of bytes in the entry

1

standard output, number of bytes in the entry

2

standard error, number of bytes in the entry

3

terminal input, number of bytes in the entry

4

terminal output, number of bytes in the entry

5

window change, new number lines and columns

6

bug compatibility for sudo 1.8.7 terminal output

7

command suspend or resume, signal received

ttyin

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: ‘gunzip -c ttyin | tr "\r" "\n"’

stdin

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

ttyout

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.

stdout

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

stderr

The standard error redirected to a pipe or file.

All files other than log are compressed in gzip format unless the compress_io 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 sudo has exited or has been terminated by a signal. The iolog_flush 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 sudoreplay(8) 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 log_output or LOG_OUTPUT 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 maxseq option to the maximum number of logs you wish to store. Once the I/O log sequence number reaches maxseq, it will be reset to zero and sudoers will truncate and re-use any existing I/O logs.

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

/run/sudo/ts

Directory containing time stamps for the sudoers security policy

/var/db/sudo/lectured

Directory containing lecture status files for the sudoers security policy

/etc/environment

Initial environment for -i mode on AIX and Linux systems

EXAMPLES¶

Below are example sudoers file 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	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 sudo to log via syslog(3) using the auth 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 sudo lecture and we want to allow them to run commands in a chroot(2) “sandbox” via the -R option. User millert need not provide a password and we don't want to reset the LOGNAME or USER 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). Note that this will not effectively constrain users with sudo ALL 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 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/. Note that one command in the DUMPS Cmnd_Alias includes a sha224 digest, /home/operator/bin/start_backups. 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 sudo.

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. Because command line arguments are matched as a single, concatenated string, the ‘*’ wildcard will match multiple words. This example assumes that passwd(1) does not take multiple user names on the command line. Note that on GNU systems, options to passwd(1) 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 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 (primary, 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. While not specifically mentioned in the rule, the commands in the PAGERS Cmnd_Alias all reside in /usr/bin and have the noexec option set.

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.

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

On the host www, any user in the WEBADMIN 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 nosuid\,nodev /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

operator	sudoedit /etc/motd

$ sudoedit /etc/motd

DEBUGGING¶

Versions 1.8.4 and higher of the sudoers 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 sudo.conf(5) file.

The sudoers plugin uses the same debug flag format as the sudo front-end: subsystem@priority.

The priorities used by sudoers, in order of decreasing severity, are: crit, err, warn, notice, diag, info, trace and debug. Each priority, when specified, also includes all priorities higher than it. For example, a priority of notice would include debug messages logged at notice and higher.

The following subsystems are used by the sudoers plugin:

alias

User_Alias, Runas_Alias, Host_Alias and Cmnd_Alias processing

all

matches every subsystem

audit

BSM and Linux audit code

auth

user authentication

defaults

sudoers file Defaults settings

env

environment handling

ldap

LDAP-based sudoers

logging

logging support

match

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

netif

network interface handling

nss

network service switch handling in sudoers

parser

sudoers file parsing

perms

permission setting

plugin

The equivalent of main for the plugin.

pty

pseudo-terminal related code

rbtree

redblack tree internals

sssd

SSSD-based sudoers

util

utility functions

Debug sudo /var/log/sudo_debug match@info,nss@info

For more information, see the sudo.conf(5) manual.

SEE ALSO¶

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

AUTHORS¶

Many people have worked on sudo over the years; this version consists of code written primarily by:

See the CONTRIBUTORS file in the sudo distribution (https://www.sudo.ws/contributors.html) for an exhaustive list of people who have contributed to sudo.

CAVEATS¶

The sudoers file should always be edited by the visudo utility which locks the file and checks for syntax errors. If sudoers contains syntax errors, sudo may refuse to run, which is a serious problem if sudo is your only method of obtaining superuser privileges. Recent versions of sudoers will attempt to recover after a syntax error by ignoring the rest of the line after encountering an error. Older versions of sudo will not run if sudoers 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 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 https://bugzilla.sudo.ws/

SUPPORT¶

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.

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