1SUDOERS(5) BSD File Formats Manual SUDOERS(5)
2
4 sudoers — default sudo security policy module
5
7 The sudoers policy module determines a user's sudo privileges. It is the
8 default sudo policy plugin. The policy is driven by the /etc/sudoers
9 file or, optionally in LDAP. The policy format is described in detail in
10 the SUDOERS FILE FORMAT section. For information on storing sudoers pol‐
11 icy information in LDAP, please see sudoers.ldap(5).
12 Authentication and logging
14 The sudoers security policy requires that most users authenticate them‐
15 selves before they can use sudo. A password is not required if the
16 invoking user is root, if the target user is the same as the invoking
17 user, or if the policy has disabled authentication for the user or com‐
18 mand. Unlike su(1), when sudoers requires authentication, it validates
19 the invoking user's credentials, not the target user's (or root's) cre‐
20 dentials. This can be changed via the rootpw, targetpw and runaspw
21 flags, described later.
22 If a user who is not listed in the policy tries to run a command via
24 sudo, mail is sent to the proper authorities. The address used for such
25 mail is configurable via the mailto Defaults entry (described later) and
26 defaults to root.
27 Note that mail will not be sent if an unauthorized user tries to run sudo
29 with the -l or -v option. This allows users to determine for themselves
30 whether or not they are allowed to use sudo.
31 If sudo is run by root and the SUDO_USER environment variable is set, the
33 sudoers policy will use this value to determine who the actual user is.
34 This can be used by a user to log commands through sudo even when a root
35 shell has been invoked. It also allows the -e option to remain useful
36 even when invoked via a sudo-run script or program. Note, however, that
37 the sudoers lookup is still done for root, not the user specified by
38 SUDO_USER.
39 sudoers uses time stamp files for credential caching. Once a user has
41 been authenticated, the time stamp is updated and the user may then use
42 sudo without a password for a short period of time (5 minutes unless
43 overridden by the timeout option). By default, sudoers uses a tty-based
44 time stamp which means that there is a separate time stamp for each of a
45 user's login sessions. The tty_tickets option can be disabled to force
46 the use of a single time stamp for all of a user's sessions.
47 sudoers can log both successful and unsuccessful attempts (as well as
49 errors) to syslog(3), a log file, or both. By default, sudoers will log
50 via syslog(3) but this is changeable via the syslog and logfile Defaults
51 settings.
52 sudoers also supports logging a command's input and output streams. I/O
54 logging is not on by default but can be enabled using the log_input and
55 log_output Defaults flags as well as the LOG_INPUT and LOG_OUTPUT command
56 tags.
57 Command environment
59 Since environment variables can influence program behavior, sudoers pro‐
60 vides a means to restrict which variables from the user's environment are
61 inherited by the command to be run. There are two distinct ways sudoers
62 can deal with environment variables.
63 By default, the env_reset option is enabled. This causes commands to be
65 executed with a new, minimal environment. On AIX (and Linux systems
66 without PAM), the environment is initialized with the contents of the
67 /etc/environment file. The new environment contains the TERM, PATH,
68 HOME, MAIL, SHELL, LOGNAME, USER, USERNAME and SUDO_* variables in addi‐
69 tion to variables from the invoking process permitted by the env_check
70 and env_keep options. This is effectively a whitelist for environment
71 variables.
72 If, however, the env_reset option is disabled, any variables not explic‐
74 itly denied by the env_check and env_delete options are inherited from
75 the invoking process. In this case, env_check and env_delete behave like
76 a blacklist. Since it is not possible to blacklist all potentially dan‐
77 gerous environment variables, use of the default env_reset behavior is
78 encouraged.
79 In all cases, environment variables with a value beginning with () are
81 removed as they could be interpreted as bash functions. The list of
82 environment variables that sudo allows or denies is contained in the out‐
83 put of “sudo -V” when run as root.
84 Note that the dynamic linker on most operating systems will remove vari‐
86 ables that can control dynamic linking from the environment of setuid
87 executables, including sudo. Depending on the operating system this may
88 include _RLD*, DYLD_*, LD_*, LDR_*, LIBPATH, SHLIB_PATH, and others.
89 These type of variables are removed from the environment before sudo even
90 begins execution and, as such, it is not possible for sudo to preserve
91 them.
92 As a special case, if sudo's -i option (initial login) is specified,
94 sudoers will initialize the environment regardless of the value of
95 env_reset. The DISPLAY, PATH and TERM variables remain unchanged; HOME,
96 MAIL, SHELL, USER, and LOGNAME are set based on the target user. On AIX
97 (and Linux systems without PAM), the contents of /etc/environment are
98 also included. All other environment variables are removed.
99 Finally, if the env_file option is defined, any variables present in that
101 file will be set to their specified values as long as they would not con‐
102 flict with an existing environment variable.
103
105 The sudoers file is composed of two types of entries: aliases (basically
106 variables) and user specifications (which specify who may run what).
107 When multiple entries match for a user, they are applied in order. Where
109 there are multiple matches, the last match is used (which is not neces‐
110 sarily the most specific match).
111 The sudoers grammar will be described below in Extended Backus-Naur Form
113 (EBNF). Don't despair if you are unfamiliar with EBNF; it is fairly sim‐
114 ple, and the definitions below are annotated.
115 Quick guide to EBNF
117 EBNF is a concise and exact way of describing the grammar of a language.
118 Each EBNF definition is made up of production rules. E.g.,
119 symbol ::= definition | alternate1 | alternate2 ...
121 Each production rule references others and thus makes up a grammar for
123 the language. EBNF also contains the following operators, which many
124 readers will recognize from regular expressions. Do not, however, con‐
125 fuse them with “wildcard” characters, which have different meanings.
126 ? Means that the preceding symbol (or group of symbols) is optional.
128 That is, it may appear once or not at all.
129 * Means that the preceding symbol (or group of symbols) may appear
131 zero or more times.
132 + Means that the preceding symbol (or group of symbols) may appear
134 one or more times.
135 Parentheses may be used to group symbols together. For clarity, we will
137 use single quotes ('') to designate what is a verbatim character string
138 (as opposed to a symbol name).
139 Aliases
141 There are four kinds of aliases: User_Alias, Runas_Alias, Host_Alias and
142 Cmnd_Alias.
143 Alias ::= 'User_Alias' User_Alias (':' User_Alias)* |
145 'Runas_Alias' Runas_Alias (':' Runas_Alias)* |
146 'Host_Alias' Host_Alias (':' Host_Alias)* |
147 'Cmnd_Alias' Cmnd_Alias (':' Cmnd_Alias)*
148 User_Alias ::= NAME '=' User_List
150 Runas_Alias ::= NAME '=' Runas_List
152 Host_Alias ::= NAME '=' Host_List
154 Cmnd_Alias ::= NAME '=' Cmnd_List
156 NAME ::= [A-Z]([A-Z][0-9]_)*
158 Each alias definition is of the form
160 Alias_Type NAME = item1, item2, ...
162 where Alias_Type is one of User_Alias, Runas_Alias, Host_Alias, or
164 Cmnd_Alias. A NAME is a string of uppercase letters, numbers, and under‐
165 score characters (‘_’). A NAME must start with an uppercase letter. It
166 is possible to put several alias definitions of the same type on a single
167 line, joined by a colon (‘:’). E.g.,
168 Alias_Type NAME = item1, item2, item3 : NAME = item4, item5
170 The definitions of what constitutes a valid alias member follow.
172 User_List ::= User |
174 User ',' User_List
175 User ::= '!'* user name |
177 '!'* #uid |
178 '!'* %group |
179 '!'* %#gid |
180 '!'* +netgroup |
181 '!'* %:nonunix_group |
182 '!'* %:#nonunix_gid |
183 '!'* User_Alias
184 A User_List is made up of one or more user names, user ids (prefixed with
186 ‘#’), system group names and ids (prefixed with ‘%’ and ‘%#’ respec‐
187 tively), netgroups (prefixed with ‘+’), non-Unix group names and IDs
188 (prefixed with ‘%:’ and ‘%:#’ respectively) and User_Aliases. Each list
189 item may be prefixed with zero or more ‘!’ operators. An odd number of
190 ‘!’ operators negate the value of the item; an even number just cancel
191 each other out.
192 A user name, uid, group, gid, netgroup, nonunix_group or nonunix_gid may
194 be enclosed in double quotes to avoid the need for escaping special char‐
195 acters. Alternately, special characters may be specified in escaped hex
196 mode, e.g. \x20 for space. When using double quotes, any prefix charac‐
197 ters must be included inside the quotes.
198 The actual nonunix_group and nonunix_gid syntax depends on the underlying
200 group provider plugin (see the group_plugin description below). For
201 instance, the QAS AD plugin supports the following formats:
202 · Group in the same domain: "%:Group Name"
204 · Group in any domain: "%:Group Name@FULLY.QUALIFIED.DOMAIN"
206 · Group SID: "%:S-1-2-34-5678901234-5678901234-5678901234-567"
208 Note that quotes around group names are optional. Unquoted strings must
210 use a backslash (‘\’) to escape spaces and special characters. See Other
211 special characters and reserved words for a list of characters that need
212 to be escaped.
213 Runas_List ::= Runas_Member |
215 Runas_Member ',' Runas_List
216 Runas_Member ::= '!'* user name |
218 '!'* #uid |
219 '!'* %group |
220 '!'* %#gid |
221 '!'* %:nonunix_group |
222 '!'* %:#nonunix_gid |
223 '!'* +netgroup |
224 '!'* Runas_Alias
225 A Runas_List is similar to a User_List except that instead of
227 User_Aliases it can contain Runas_Aliases. Note that user names and
228 groups are matched as strings. In other words, two users (groups) with
229 the same uid (gid) are considered to be distinct. If you wish to match
230 all user names with the same uid (e.g. root and toor), you can use a uid
231 instead (#0 in the example given).
232 Host_List ::= Host |
234 Host ',' Host_List
235 Host ::= '!'* host name |
237 '!'* ip_addr |
238 '!'* network(/netmask)? |
239 '!'* +netgroup |
240 '!'* Host_Alias
241 A Host_List is made up of one or more host names, IP addresses, network
243 numbers, netgroups (prefixed with ‘+’) and other aliases. Again, the
244 value of an item may be negated with the ‘!’ operator. If you do not
245 specify a netmask along with the network number, sudo will query each of
246 the local host's network interfaces and, if the network number corre‐
247 sponds to one of the hosts's network interfaces, the corresponding net‐
248 mask will be used. The netmask may be specified either in standard IP
249 address notation (e.g. 255.255.255.0 or ffff:ffff:ffff:ffff::), or CIDR
250 notation (number of bits, e.g. 24 or 64). A host name may include shell-
251 style wildcards (see the Wildcards section below), but unless the host
252 name command on your machine returns the fully qualified host name,
253 you'll need to use the fqdn option for wildcards to be useful. Note that
254 sudo only inspects actual network interfaces; this means that IP address
255 127.0.0.1 (localhost) will never match. Also, the host name “localhost”
256 will only match if that is the actual host name, which is usually only
257 the case for non-networked systems.
258 Cmnd_List ::= Cmnd |
260 Cmnd ',' Cmnd_List
261 command name ::= file name |
263 file name args |
264 file name '""'
265 Cmnd ::= '!'* command name |
267 '!'* directory |
268 '!'* "sudoedit" |
269 '!'* Cmnd_Alias
270 A Cmnd_List is a list of one or more command names, directories, and
272 other aliases. A command name is a fully qualified file name which may
273 include shell-style wildcards (see the Wildcards section below). A sim‐
274 ple file name allows the user to run the command with any arguments
275 he/she wishes. However, you may also specify command line arguments
276 (including wildcards). Alternately, you can specify "" to indicate that
277 the command may only be run without command line arguments. A directory
278 is a fully qualified path name ending in a ‘/’. When you specify a
279 directory in a Cmnd_List, the user will be able to run any file within
280 that directory (but not in any sub-directories therein).
281 If a Cmnd has associated command line arguments, then the arguments in
283 the Cmnd must match exactly those given by the user on the command line
284 (or match the wildcards if there are any). Note that the following char‐
285 acters must be escaped with a ‘\’ if they are used in command arguments:
286 ‘,’, ‘:’, ‘=’, ‘\’. The special command “sudoedit” is used to permit a
287 user to run sudo with the -e option (or as sudoedit). It may take com‐
288 mand line arguments just as a normal command does.
289 Defaults
291 Certain configuration options may be changed from their default values at
292 run-time via one or more Default_Entry lines. These may affect all users
293 on any host, all users on a specific host, a specific user, a specific
294 command, or commands being run as a specific user. Note that per-command
295 entries may not include command line arguments. If you need to specify
296 arguments, define a Cmnd_Alias and reference that instead.
297 Default_Type ::= 'Defaults' |
299 'Defaults' '@' Host_List |
300 'Defaults' ':' User_List |
301 'Defaults' '!' Cmnd_List |
302 'Defaults' '>' Runas_List
303 Default_Entry ::= Default_Type Parameter_List
305 Parameter_List ::= Parameter |
307 Parameter ',' Parameter_List
308 Parameter ::= Parameter '=' Value |
310 Parameter '+=' Value |
311 Parameter '-=' Value |
312 '!'* Parameter
313 Parameters may be flags, integer values, strings, or lists. Flags are
315 implicitly boolean and can be turned off via the ‘!’ operator. Some
316 integer, string and list parameters may also be used in a boolean context
317 to disable them. Values may be enclosed in double quotes ("") when they
318 contain multiple words. Special characters may be escaped with a back‐
319 slash (‘\’).
320 Lists have two additional assignment operators, += and -=. These opera‐
322 tors are used to add to and delete from a list respectively. It is not
323 an error to use the -= operator to remove an element that does not exist
324 in a list.
325 Defaults entries are parsed in the following order: generic, host and
327 user Defaults first, then runas Defaults and finally command defaults.
328 See SUDOERS OPTIONS for a list of supported Defaults parameters.
330 User specification
332 User_Spec ::= User_List Host_List '=' Cmnd_Spec_List \
333 (':' Host_List '=' Cmnd_Spec_List)*
334 Cmnd_Spec_List ::= Cmnd_Spec |
336 Cmnd_Spec ',' Cmnd_Spec_List
337 Cmnd_Spec ::= Runas_Spec? SELinux_Spec? Tag_Spec* Cmnd
339 Runas_Spec ::= '(' Runas_List? (':' Runas_List)? ')'
341 SELinux_Spec ::= ('ROLE=role' | 'TYPE=type')
343 Tag_Spec ::= ('NOPASSWD:' | 'PASSWD:' | 'NOEXEC:' | 'EXEC:' |
345 'SETENV:' | 'NOSETENV:' | 'LOG_INPUT:' | 'NOLOG_INPUT:' |
346 'LOG_OUTPUT:' | 'NOLOG_OUTPUT:')
347 A user specification determines which commands a user may run (and as
349 what user) on specified hosts. By default, commands are run as root, but
350 this can be changed on a per-command basis.
351 The basic structure of a user specification is “who where = (as_whom)
353 what”. Let's break that down into its constituent parts:
354 Runas_Spec
356 A Runas_Spec determines the user and/or the group that a command may be
357 run as. A fully-specified Runas_Spec consists of two Runas_Lists (as
358 defined above) separated by a colon (‘:’) and enclosed in a set of paren‐
359 theses. The first Runas_List indicates which users the command may be
360 run as via sudo's -u option. The second defines a list of groups that
361 can be specified via sudo's -g option. If both Runas_Lists are speci‐
362 fied, the command may be run with any combination of users and groups
363 listed in their respective Runas_Lists. If only the first is specified,
364 the command may be run as any user in the list but no -g option may be
365 specified. If the first Runas_List is empty but the second is specified,
366 the command may be run as the invoking user with the group set to any
367 listed in the Runas_List. If both Runas_Lists are empty, the command may
368 only be run as the invoking user. If no Runas_Spec is specified the com‐
369 mand may be run as root and no group may be specified.
370 A Runas_Spec sets the default for the commands that follow it. What this
372 means is that for the entry:
373 dgb boulder = (operator) /bin/ls, /bin/kill, /usr/bin/lprm
375 The user dgb may run /bin/ls, /bin/kill, and /usr/bin/lprm—but only as
377 operator. E.g.,
378 $ sudo -u operator /bin/ls
380 It is also possible to override a Runas_Spec later on in an entry. If we
382 modify the entry like so:
383 dgb boulder = (operator) /bin/ls, (root) /bin/kill, /usr/bin/lprm
385 Then user dgb is now allowed to run /bin/ls as operator, but /bin/kill
387 and /usr/bin/lprm as root.
388 We can extend this to allow dgb to run /bin/ls with either the user or
390 group set to operator:
391 dgb boulder = (operator : operator) /bin/ls, (root) /bin/kill,\
393 /usr/bin/lprm
394 Note that while the group portion of the Runas_Spec permits the user to
396 run as command with that group, it does not force the user to do so. If
397 no group is specified on the command line, the command will run with the
398 group listed in the target user's password database entry. The following
399 would all be permitted by the sudoers entry above:
400 $ sudo -u operator /bin/ls
402 $ sudo -u operator -g operator /bin/ls
403 $ sudo -g operator /bin/ls
404 In the following example, user tcm may run commands that access a modem
406 device file with the dialer group.
407 tcm boulder = (:dialer) /usr/bin/tip, /usr/bin/cu,\
409 /usr/local/bin/minicom
410 Note that in this example only the group will be set, the command still
412 runs as user tcm. E.g.
413 $ sudo -g dialer /usr/bin/cu
415 Multiple users and groups may be present in a Runas_Spec, in which case
417 the user may select any combination of users and groups via the -u and -g
418 options. In this example:
419 alan ALL = (root, bin : operator, system) ALL
421 user alan may run any command as either user root or bin, optionally set‐
423 ting the group to operator or system.
424 SELinux_Spec
426 On systems with SELinux support, sudoers entries may optionally have an
427 SELinux role and/or type associated with a command. If a role or type is
428 specified with the command it will override any default values specified
429 in sudoers. A role or type specified on the command line, however, will
430 supersede the values in sudoers.
431 Tag_Spec
433 A command may have zero or more tags associated with it. There are ten
434 possible tag values: NOPASSWD, PASSWD, NOEXEC, EXEC, SETENV, NOSETENV,
435 LOG_INPUT, NOLOG_INPUT, LOG_OUTPUT and NOLOG_OUTPUT. Once a tag is set
436 on a Cmnd, subsequent Cmnds in the Cmnd_Spec_List, inherit the tag unless
437 it is overridden by the opposite tag (in other words, PASSWD overrides
438 NOPASSWD and NOEXEC overrides EXEC).
439 NOPASSWD and PASSWD
441 By default, sudo requires that a user authenticate him or herself before
443 running a command. This behavior can be modified via the NOPASSWD tag.
444 Like a Runas_Spec, the NOPASSWD tag sets a default for the commands that
445 follow it in the Cmnd_Spec_List. Conversely, the PASSWD tag can be used
446 to reverse things. For example:
447 ray rushmore = NOPASSWD: /bin/kill, /bin/ls, /usr/bin/lprm
449 would allow the user ray to run /bin/kill, /bin/ls, and /usr/bin/lprm as
451 root on the machine rushmore without authenticating himself. If we only
452 want ray to be able to run /bin/kill without a password the entry would
453 be:
454 ray rushmore = NOPASSWD: /bin/kill, PASSWD: /bin/ls, /usr/bin/lprm
456 Note, however, that the PASSWD tag has no effect on users who are in the
458 group specified by the exempt_group option.
459 By default, if the NOPASSWD tag is applied to any of the entries for a
461 user on the current host, he or she will be able to run “sudo -l” without
462 a password. Additionally, a user may only run “sudo -v” without a pass‐
463 word if the NOPASSWD tag is present for all a user's entries that pertain
464 to the current host. This behavior may be overridden via the verifypw
465 and listpw options.
466 NOEXEC and EXEC
468 If sudo has been compiled with noexec support and the underlying operat‐
470 ing system supports it, the NOEXEC tag can be used to prevent a dynami‐
471 cally-linked executable from running further commands itself.
472 In the following example, user aaron may run /usr/bin/more and
474 /usr/bin/vi but shell escapes will be disabled.
475 aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
477 See the Preventing shell escapes section below for more details on how
479 NOEXEC works and whether or not it will work on your system.
480 SETENV and NOSETENV
482 These tags override the value of the setenv option on a per-command
484 basis. Note that if SETENV has been set for a command, the user may dis‐
485 able the env_reset option from the command line via the -E option. Addi‐
486 tionally, environment variables set on the command line are not subject
487 to the restrictions imposed by env_check, env_delete, or env_keep. As
488 such, only trusted users should be allowed to set variables in this man‐
489 ner. If the command matched is ALL, the SETENV tag is implied for that
490 command; this default may be overridden by use of the NOSETENV tag.
491 LOG_INPUT and NOLOG_INPUT
493 These tags override the value of the log_input option on a per-command
495 basis. For more information, see the description of log_input in the
496 SUDOERS OPTIONS section below.
497 LOG_OUTPUT and NOLOG_OUTPUT
499 These tags override the value of the log_output option on a per-command
501 basis. For more information, see the description of log_output in the
502 SUDOERS OPTIONS section below.
503 Wildcards
505 sudo allows shell-style wildcards (aka meta or glob characters) to be
506 used in host names, path names and command line arguments in the sudoers
507 file. Wildcard matching is done via the POSIX [22mglob(3) and fnmatch(3)
508 routines. Note that these are not regular expressions.
509 * Matches any set of zero or more characters.
511 ? Matches any single character.
513 [...] Matches any character in the specified range.
515 [!...] Matches any character not in the specified range.
517 \x For any character ‘x’, evaluates to ‘x’. This is used to
519 escape special characters such as: ‘*’, ‘?’, ‘[’, and ‘]’.
520 POSIX character classes may also be used if your system's glob(3) and
522 fnmatch(3) functions support them. However, because the ‘:’ character
523 has special meaning in sudoers, it must be escaped. For example:
524 /bin/ls [[alpha]]*
526 Would match any file name beginning with a letter.
528 Note that a forward slash (‘/’) will not be matched by wildcards used in
530 the path name. This is to make a path like:
531 /usr/bin/*
533 match /usr/bin/who but not /usr/bin/X11/xterm.
535 When matching the command line arguments, however, a slash does get
537 matched by wildcards since command line arguments may contain arbitrary
538 strings and not just path names.
539 Wildcards in command line arguments should be used with care. Because
541 command line arguments are matched as a single, concatenated string, a
542 wildcard such as ‘?’ or ‘*’ can match multiple words. For example, while
543 a sudoers entry like:
544 %operator ALL = /bin/cat /var/log/messages*
546 will allow command like:
548 $ sudo cat /var/log/messages.1
550 It will also allow:
552 $ sudo cat /var/log/messages /etc/shadow
554 which is probably not what was intended.
556 Exceptions to wildcard rules
558 The following exceptions apply to the above rules:
559 "" If the empty string "" is the only command line argument in the
561 sudoers entry it means that command is not allowed to be run
562 with any arguments.
563 sudoedit Command line arguments to the sudoedit built-in command should
565 always be path names, so a forward slash (‘/’) will not be
566 matched by a wildcard.
567 Including other files from within sudoers
569 It is possible to include other sudoers files from within the sudoers
570 file currently being parsed using the #include and #includedir direc‐
571 tives.
572 This can be used, for example, to keep a site-wide sudoers file in addi‐
574 tion to a local, per-machine file. For the sake of this example the
575 site-wide sudoers will be /etc/sudoers and the per-machine one will be
576 /etc/sudoers.local. To include /etc/sudoers.local from within
577 /etc/sudoers we would use the following line in /etc/sudoers:
578 #include /etc/sudoers.local
580 When sudo reaches this line it will suspend processing of the current
582 file (/etc/sudoers) and switch to /etc/sudoers.local. Upon reaching the
583 end of /etc/sudoers.local, the rest of /etc/sudoers will be processed.
584 Files that are included may themselves include other files. A hard limit
585 of 128 nested include files is enforced to prevent include file loops.
586 If the path to the include file is not fully-qualified (does not begin
588 with a ‘/’, it must be located in the same directory as the sudoers file
589 it was included from. For example, if /etc/sudoers contains the line:
590 #include sudoers.local
592 the file that will be included is /etc/sudoers.local.
594 The file name may also include the %h escape, signifying the short form
596 of the host name. In other words, if the machine's host name is
597 “xerxes”, then
598 #include /etc/sudoers.%h
600 will cause sudo to include the file /etc/sudoers.xerxes.
602 The #includedir directive can be used to create a sudo.d directory that
604 the system package manager can drop sudoers rules into as part of package
605 installation. For example, given:
606 #includedir /etc/sudoers.d
608 sudo will read each file in /etc/sudoers.d, skipping file names that end
610 in ‘~’ or contain a ‘.’ character to avoid causing problems with package
611 manager or editor temporary/backup files. Files are parsed in sorted
612 lexical order. That is, /etc/sudoers.d/01_first will be parsed before
613 /etc/sudoers.d/10_second. Be aware that because the sorting is lexical,
614 not numeric, /etc/sudoers.d/1_whoops would be loaded after
615 /etc/sudoers.d/10_second. Using a consistent number of leading zeroes in
616 the file names can be used to avoid such problems.
617 Note that unlike files included via #include, visudo will not edit the
619 files in a #includedir directory unless one of them contains a syntax
620 error. It is still possible to run visudo with the -f flag to edit the
621 files directly.
622 Other special characters and reserved words
624 The pound sign (‘#’) is used to indicate a comment (unless it is part of
625 a #include directive or unless it occurs in the context of a user name
626 and is followed by one or more digits, in which case it is treated as a
627 uid). Both the comment character and any text after it, up to the end of
628 the line, are ignored.
629 The reserved word ALL is a built-in alias that always causes a match to
631 succeed. It can be used wherever one might otherwise use a Cmnd_Alias,
632 User_Alias, Runas_Alias, or Host_Alias. You should not try to define
633 your own alias called ALL as the built-in alias will be used in prefer‐
634 ence to your own. Please note that using ALL can be dangerous since in a
635 command context, it allows the user to run any command on the system.
636 An exclamation point (‘!’) can be used as a logical not operator in a
638 list or alias as well as in front of a Cmnd. This allows one to exclude
639 certain values. For the ‘!’ operator to be effective, there must be
640 something for it to exclude. For example, to match all users except for
641 root one would use:
642 ALL,!root
644 If the ALL, is omitted, as in:
646 !root
648 it would explicitly deny root but not match any other users. This is
650 different from a true “negation” operator.
651 Note, however, that using a ‘!’ in conjunction with the built-in ALL
653 alias to allow a user to run “all but a few” commands rarely works as
654 intended (see SECURITY NOTES below).
655 Long lines can be continued with a backslash (‘\’) as the last character
657 on the line.
658 White space between elements in a list as well as special syntactic char‐
660 acters in a User Specification (‘=’, ‘:’, ‘(’, ‘)’) is optional.
661 The following characters must be escaped with a backslash (‘\’) when used
663 as part of a word (e.g. a user name or host name): ‘!’, ‘=’, ‘:’, ‘,’,
664 ‘(’, ‘)’, ‘\’.
665
667 sudo's behavior can be modified by Default_Entry lines, as explained ear‐
668 lier. A list of all supported Defaults parameters, grouped by type, are
669 listed below.
670 Boolean Flags:
672 always_set_home If enabled, sudo will set the HOME environment variable
674 to the home directory of the target user (which is root
675 unless the -u option is used). This effectively means
676 that the -H option is always implied. Note that HOME
677 is already set when the the env_reset option is
678 enabled, so always_set_home is only effective for con‐
679 figurations where either env_reset is disabled or HOME
680 is present in the env_keep list. This flag is off by
681 default.
682 authenticate If set, users must authenticate themselves via a pass‐
684 word (or other means of authentication) before they may
685 run commands. This default may be overridden via the
686 PASSWD and NOPASSWD tags. This flag is on by default.
687 closefrom_override
689 If set, the user may use sudo's -C option which over‐
690 rides the default starting point at which sudo begins
691 closing open file descriptors. This flag is off by
692 default.
693 compress_io If set, and sudo is configured to log a command's input
695 or output, the I/O logs will be compressed using zlib.
696 This flag is on by default when sudo is compiled with
697 zlib support.
698 env_editor If set, visudo will use the value of the EDITOR or
700 VISUAL environment variables before falling back on the
701 default editor list. Note that this may create a secu‐
702 rity hole as it allows the user to run any arbitrary
703 command as root without logging. A safer alternative
704 is to place a colon-separated list of editors in the
705 editor variable. visudo will then only use the EDITOR
706 or VISUAL if they match a value specified in editor.
707 This flag is on by default.
708 env_reset If set, sudo will run the command in a minimal environ‐
710 ment containing the TERM, PATH, HOME, MAIL, SHELL,
711 LOGNAME, USER, USERNAME and SUDO_* variables. Any
712 variables in the caller's environment that match the
713 env_keep and env_check lists are then added, followed
714 by any variables present in the file specified by the
715 env_file option (if any). The default contents of the
716 env_keep and env_check lists are displayed when sudo is
717 run by root with the -V option. If the secure_path
718 option is set, its value will be used for the PATH
719 environment variable. This flag is on by default.
720 fast_glob Normally, sudo uses the glob(3) function to do shell-
722 style globbing when matching path names. However,
723 since it accesses the file system, glob(3) can take a
724 long time to complete for some patterns, especially
725 when the pattern references a network file system that
726 is mounted on demand (auto mounted). The fast_glob
727 option causes sudo to use the fnmatch(3) function,
728 which does not access the file system to do its match‐
729 ing. The disadvantage of fast_glob is that it is
730 unable to match relative path names such as ./ls or
731 ../bin/ls. This has security implications when path
732 names that include globbing characters are used with
733 the negation operator, ‘!’, as such rules can be triv‐
734 ially bypassed. As such, this option should not be
735 used when sudoers contains rules that contain negated
736 path names which include globbing characters. This
737 flag is off by default.
738 fqdn Set this flag if you want to put fully qualified host
740 names in the sudoers file when the local host name (as
741 returned by the hostname command) does not contain the
742 domain name. In other words, instead of myhost you
743 would use myhost.mydomain.edu. You may still use the
744 short form if you wish (and even mix the two). This
745 option is only effective when the “canonical” host
746 name, as returned by the getaddrinfo() or
747 gethostbyname() function, is a fully-qualified domain
748 name. This is usually the case when the system is con‐
749 figured to use DNS for host name resolution.
750 If the system is configured to use the /etc/hosts file
752 in preference to DNS, the “canonical” host name may not
753 be fully-qualified. The order that sources are queried
754 for hosts name resolution is usually specified in the
755 /etc/nsswitch.conf, /etc/netsvc.conf, /etc/host.conf,
756 or, in some cases, /etc/resolv.conf file. In the
757 /etc/hosts file, the first host name of the entry is
758 considered to be the “canonical” name; subsequent names
759 are aliases that are not used by sudoers. For example,
760 the following hosts file line for the machine “xyzzy”
761 has the fully-qualified domain name as the “canonical”
762 host name, and the short version as an alias.
763 192.168.1.1 xyzzy.sudo.ws xyzzy
765 If the machine's hosts file entry is not formatted
767 properly, the fqdn option will not be effective if it
768 is queried before DNS.
769 Beware that when using DNS for host name resolution,
771 turning on fqdn requires sudoers to make DNS lookups
772 which renders sudo unusable if DNS stops working (for
773 example if the machine is disconnected from the net‐
774 work). Also note that just like with the hosts file,
775 you must use the “canonical” name as DNS knows it.
776 That is, you may not use a host alias (CNAME entry) due
777 to performance issues and the fact that there is no way
778 to get all aliases from DNS.
779 This flag is off by default.
781 ignore_dot If set, sudo will ignore "." or "" (both denoting cur‐
783 rent directory) in the PATH environment variable; the
784 PATH itself is not modified. This flag is on by
785 default.
786 ignore_local_sudoers
788 If set via LDAP, parsing of /etc/sudoers will be
789 skipped. This is intended for Enterprises that wish to
790 prevent the usage of local sudoers files so that only
791 LDAP is used. This thwarts the efforts of rogue opera‐
792 tors who would attempt to add roles to /etc/sudoers.
793 When this option is present, /etc/sudoers does not even
794 need to exist. Since this option tells sudo how to
795 behave when no specific LDAP entries have been matched,
796 this sudoOption is only meaningful for the cn=defaults
797 section. This flag is off by default.
798 insults If set, sudo will insult users when they enter an
800 incorrect password. This flag is off by default.
801 log_host If set, the host name will be logged in the (non-sys‐
803 log) sudo log file. This flag is off by default.
804 log_input If set, sudo will run the command in a pseudo tty and
806 log all user input. If the standard input is not con‐
807 nected to the user's tty, due to I/O redirection or
808 because the command is part of a pipeline, that input
809 is also captured and stored in a separate log file.
810 Input is logged to the directory specified by the
812 iolog_dir option (/var/log/sudo-io by default) using a
813 unique session ID that is included in the normal sudo
814 log line, prefixed with “TSID=”. The iolog_file option
815 may be used to control the format of the session ID.
816 Note that user input may contain sensitive information
818 such as passwords (even if they are not echoed to the
819 screen), which will be stored in the log file unen‐
820 crypted. In most cases, logging the command output via
821 log_output is all that is required.
822 log_output If set, sudo will run the command in a pseudo tty and
824 log all output that is sent to the screen, similar to
825 the script(1) command. If the standard output or stan‐
826 dard error is not connected to the user's tty, due to
827 I/O redirection or because the command is part of a
828 pipeline, that output is also captured and stored in
829 separate log files.
830 Output is logged to the directory specified by the
832 iolog_dir option (/var/log/sudo-io by default) using a
833 unique session ID that is included in the normal sudo
834 log line, prefixed with “TSID=”. The iolog_file option
835 may be used to control the format of the session ID.
836 Output logs may be viewed with the sudoreplay(8) util‐
838 ity, which can also be used to list or search the
839 available logs.
840 log_year If set, the four-digit year will be logged in the (non-
842 syslog) sudo log file. This flag is off by default.
843 long_otp_prompt When validating with a One Time Password (OTP) scheme
845 such as S/Key or OPIE, a two-line prompt is used to
846 make it easier to cut and paste the challenge to a
847 local window. It's not as pretty as the default but
848 some people find it more convenient. This flag is off
849 by default.
850 mail_always Send mail to the mailto user every time a users runs
852 sudo. This flag is off by default.
853 mail_badpass Send mail to the mailto user if the user running sudo
855 does not enter the correct password. If the command
856 the user is attempting to run is not permitted by
857 sudoers and one of the mail_always, mail_no_host,
858 mail_no_perms or mail_no_user flags are set, this flag
859 will have no effect. This flag is off by default.
860 mail_no_host If set, mail will be sent to the mailto user if the
862 invoking user exists in the sudoers file, but is not
863 allowed to run commands on the current host. This flag
864 is off by default.
865 mail_no_perms If set, mail will be sent to the mailto user if the
867 invoking user is allowed to use sudo but the command
868 they are trying is not listed in their sudoers file
869 entry or is explicitly denied. This flag is off by
870 default.
871 mail_no_user If set, mail will be sent to the mailto user if the
873 invoking user is not in the sudoers file. This flag is
874 on by default.
875 noexec If set, all commands run via sudo will behave as if the
877 NOEXEC tag has been set, unless overridden by a EXEC
878 tag. See the description of NOEXEC and EXEC below as
879 well as the Preventing shell escapes section at the end
880 of this manual. This flag is off by default.
881 path_info Normally, sudo will tell the user when a command could
883 not be found in their PATH environment variable. Some
884 sites may wish to disable this as it could be used to
885 gather information on the location of executables that
886 the normal user does not have access to. The disadvan‐
887 tage is that if the executable is simply not in the
888 user's PATH, sudo will tell the user that they are not
889 allowed to run it, which can be confusing. This flag
890 is on by default.
891 passprompt_override
893 The password prompt specified by passprompt will nor‐
894 mally only be used if the password prompt provided by
895 systems such as PAM matches the string “Password:”. If
896 passprompt_override is set, passprompt will always be
897 used. This flag is off by default.
898 preserve_groups By default, sudo will initialize the group vector to
900 the list of groups the target user is in. When
901 preserve_groups is set, the user's existing group vec‐
902 tor is left unaltered. The real and effective group
903 IDs, however, are still set to match the target user.
904 This flag is off by default.
905 pwfeedback By default, sudo reads the password like most other
907 Unix programs, by turning off echo until the user hits
908 the return (or enter) key. Some users become confused
909 by this as it appears to them that sudo has hung at
910 this point. When pwfeedback is set, sudo will provide
911 visual feedback when the user presses a key. Note that
912 this does have a security impact as an onlooker may be
913 able to determine the length of the password being
914 entered. This flag is off by default.
915 requiretty If set, sudo will only run when the user is logged in
917 to a real tty. When this flag is set, sudo can only be
918 run from a login session and not via other means such
919 as cron(8) or cgi-bin scripts. This flag is off by
920 default.
921 root_sudo If set, root is allowed to run sudo too. Disabling
923 this prevents users from “chaining” sudo commands to
924 get a root shell by doing something like “sudo sudo
925 /bin/sh”. Note, however, that turning off root_sudo
926 will also prevent root from running sudoedit. Dis‐
927 abling root_sudo provides no real additional security;
928 it exists purely for historical reasons. This flag is
929 on by default.
930 rootpw If set, sudo will prompt for the root password instead
932 of the password of the invoking user. This flag is off
933 by default.
934 runaspw If set, sudo will prompt for the password of the user
936 defined by the runas_default option (defaults to root)
937 instead of the password of the invoking user. This
938 flag is off by default.
939 set_home If enabled and sudo is invoked with the -s option the
941 HOME environment variable will be set to the home
942 directory of the target user (which is root unless the
943 -u option is used). This effectively makes the -s
944 option imply -H. Note that HOME is already set when
945 the the env_reset option is enabled, so set_home is
946 only effective for configurations where either
947 env_reset is disabled or HOME is present in the
948 env_keep list. This flag is off by default.
949 set_logname Normally, sudo will set the LOGNAME, USER and USERNAME
951 environment variables to the name of the target user
952 (usually root unless the -u option is given). However,
953 since some programs (including the RCS revision control
954 system) use LOGNAME to determine the real identity of
955 the user, it may be desirable to change this behavior.
956 This can be done by negating the set_logname option.
957 Note that if the env_reset option has not been dis‐
958 abled, entries in the env_keep list will override the
959 value of set_logname. This flag is on by default.
960 set_utmp When enabled, sudo will create an entry in the utmp (or
962 utmpx) file when a pseudo-tty is allocated. A pseudo-
963 tty is allocated by sudo when the log_input, log_output
964 or use_pty flags are enabled. By default, the new
965 entry will be a copy of the user's existing utmp entry
966 (if any), with the tty, time, type and pid fields
967 updated. This flag is on by default.
968 setenv Allow the user to disable the env_reset option from the
970 command line via the -E option. Additionally, environ‐
971 ment variables set via the command line are not subject
972 to the restrictions imposed by env_check, env_delete,
973 or env_keep. As such, only trusted users should be
974 allowed to set variables in this manner. This flag is
975 off by default.
976 shell_noargs If set and sudo is invoked with no arguments it acts as
978 if the -s option had been given. That is, it runs a
979 shell as root (the shell is determined by the SHELL
980 environment variable if it is set, falling back on the
981 shell listed in the invoking user's /etc/passwd entry
982 if not). This flag is off by default.
983 stay_setuid Normally, when sudo executes a command the real and
985 effective UIDs are set to the target user (root by
986 default). This option changes that behavior such that
987 the real UID is left as the invoking user's UID. In
988 other words, this makes sudo act as a setuid wrapper.
989 This can be useful on systems that disable some poten‐
990 tially dangerous functionality when a program is run
991 setuid. This option is only effective on systems that
992 support either the setreuid(2) or setresuid(2) system
993 call. This flag is off by default.
994 targetpw If set, sudo will prompt for the password of the user
996 specified by the -u option (defaults to root) instead
997 of the password of the invoking user. In addition, the
998 time stamp file name will include the target user's
999 name. Note that this flag precludes the use of a uid
1000 not listed in the passwd database as an argument to the
1001 -u option. This flag is off by default.
1002 tty_tickets If set, users must authenticate on a per-tty basis.
1004 With this flag enabled, sudo will use a file named for
1005 the tty the user is logged in on in the user's time
1006 stamp directory. If disabled, the time stamp of the
1007 directory is used instead. This flag is on by default.
1008 umask_override If set, sudo will set the umask as specified by sudoers
1010 without modification. This makes it possible to spec‐
1011 ify a more permissive umask in sudoers than the user's
1012 own umask and matches historical behavior. If
1013 umask_override is not set, sudo will set the umask to
1014 be the union of the user's umask and what is specified
1015 in sudoers. This flag is off by default. If set, sudo
1016 will run the command in a pseudo-pty even if no I/O
1017 logging is being gone. A malicious program run under
1018 sudo could conceivably fork a background process that
1019 retains to the user's terminal device after the main
1020 program has finished executing. Use of this option
1021 will make that impossible. This flag is off by
1022 default.
1023 utmp_runas If set, sudo will store the name of the runas user when
1025 updating the utmp (or utmpx) file. By default, sudo
1026 stores the name of the invoking user. This flag is off
1027 by default.
1028 visiblepw By default, sudo will refuse to run if the user must
1030 enter a password but it is not possible to disable echo
1031 on the terminal. If the visiblepw flag is set, sudo
1032 will prompt for a password even when it would be visi‐
1033 ble on the screen. This makes it possible to run
1034 things like “ssh somehost sudo ls” since by default,
1035 ssh(1) does not allocate a tty when running a command.
1036 This flag is off by default.
1037 Integers:
1039 closefrom Before it executes a command, sudo will close all open
1041 file descriptors other than standard input, standard
1042 output and standard error (ie: file descriptors 0-2).
1043 The closefrom option can be used to specify a different
1044 file descriptor at which to start closing. The default
1045 is 3.
1046 passwd_tries The number of tries a user gets to enter his/her pass‐
1048 word before sudo logs the failure and exits. The
1049 default is 3.
1050 Integers that can be used in a boolean context:
1052 loglinelen Number of characters per line for the file log. This
1054 value is used to decide when to wrap lines for nicer
1055 log files. This has no effect on the syslog log file,
1056 only the file log. The default is 80 (use 0 or negate
1057 the option to disable word wrap).
1058 passwd_timeout Number of minutes before the sudo password prompt times
1060 out, or 0 for no timeout. The timeout may include a
1061 fractional component if minute granularity is insuffi‐
1062 cient, for example 2.5. The default is 5.
1063 timestamp_timeout
1065 Number of minutes that can elapse before sudo will ask
1066 for a passwd again. The timeout may include a frac‐
1067 tional component if minute granularity is insufficient,
1068 for example 2.5. The default is 5. Set this to 0 to
1069 always prompt for a password. If set to a value less
1070 than 0 the user's time stamp will never expire. This
1071 can be used to allow users to create or delete their
1072 own time stamps via “sudo -v” and “sudo -k” respec‐
1073 tively.
1074 umask Umask to use when running the command. Negate this
1076 option or set it to 0777 to preserve the user's umask.
1077 The actual umask that is used will be the union of the
1078 user's umask and the value of the umask option, which
1079 defaults to 0022. This guarantees that sudo never low‐
1080 ers the umask when running a command. Note: on systems
1081 that use PAM, the default PAM configuration may specify
1082 its own umask which will override the value set in
1083 sudoers.
1084 Strings:
1086 badpass_message Message that is displayed if a user enters an incorrect
1088 password. The default is Sorry, try again. unless
1089 insults are enabled.
1090 editor A colon (‘:’) separated list of editors allowed to be
1092 used with visudo. visudo will choose the editor that
1093 matches the user's EDITOR environment variable if pos‐
1094 sible, or the first editor in the list that exists and
1095 is executable. The default is /usr/local/bin/vi.
1096 iolog_dir The top-level directory to use when constructing the
1098 path name for the input/output log directory. Only
1099 used if the log_input or log_output options are enabled
1100 or when the LOG_INPUT or LOG_OUTPUT tags are present
1101 for a command. The session sequence number, if any, is
1102 stored in the directory. The default is
1103 /var/log/sudo-io.
1104 The following percent (‘%’) escape sequences are sup‐
1106 ported:
1107 %{seq}
1109 expanded to a monotonically increasing base-36
1110 sequence number, such as 0100A5, where every two
1111 digits are used to form a new directory, e.g.
1112 01/00/A5
1113 %{user}
1115 expanded to the invoking user's login name
1116 %{group}
1118 expanded to the name of the invoking user's real
1119 group ID
1120 %{runas_user}
1122 expanded to the login name of the user the com‐
1123 mand will be run as (e.g. root)
1124 %{runas_group}
1126 expanded to the group name of the user the com‐
1127 mand will be run as (e.g. wheel)
1128 %{hostname}
1130 expanded to the local host name without the
1131 domain name
1132 %{command}
1134 expanded to the base name of the command being
1135 run
1136 In addition, any escape sequences supported by the sys‐
1138 tem's strftime(3) function will be expanded.
1139 To include a literal ‘%’ character, the string ‘%%’
1141 should be used.
1142 iolog_file The path name, relative to iolog_dir, in which to store
1144 input/output logs when the log_input or log_output
1145 options are enabled or when the LOG_INPUT or LOG_OUTPUT
1146 tags are present for a command. Note that iolog_file
1147 may contain directory components. The default is
1148 “%{seq}”.
1149 See the iolog_dir option above for a list of supported
1151 percent (‘%’) escape sequences.
1152 In addition to the escape sequences, path names that
1154 end in six or more Xs will have the Xs replaced with a
1155 unique combination of digits and letters, similar to
1156 the mktemp(3) function.
1157 mailsub Subject of the mail sent to the mailto user. The
1159 escape %h will expand to the host name of the machine.
1160 Default is “*** SECURITY information for %h ***”.
1161 noexec_file This option is no longer supported. The path to the
1163 noexec file should now be set in the /etc/sudo.conf
1164 file.
1165 pam_login_service
1167 On systems that use PAM for authentication, this is the
1168 service name used when the -i option is specified. The
1169 default value is “sudo-i”. See the description of
1170 pam_service for more information.
1171 pam_service On systems that use PAM for authentication, the service
1173 name specifies the PAM policy to apply. This usually
1174 corresponds to an entry in the pam.conf file or a file
1175 in the /etc/pam.d directory. The default value is
1176 “sudo”.
1177 passprompt The default prompt to use when asking for a password;
1179 can be overridden via the -p option or the SUDO_PROMPT
1180 environment variable. The following percent (‘%’)
1181 escape sequences are supported:
1182 %H expanded to the local host name including the
1184 domain name (only if the machine's host name is
1185 fully qualified or the fqdn option is set)
1186 %h expanded to the local host name without the
1188 domain name
1189 %p expanded to the user whose password is being
1191 asked for (respects the rootpw, targetpw and
1192 runaspw flags in sudoers)
1193 %U expanded to the login name of the user the com‐
1195 mand will be run as (defaults to root)
1196 %u expanded to the invoking user's login name
1198 %% two consecutive % characters are collapsed into a
1200 single % character
1201 The default value is “[sudo] password for %p:”. The
1203 default SELinux role to use when constructing a new
1204 security context to run the command. The default role
1205 may be overridden on a per-command basis in sudoers or
1206 via command line options. This option is only avail‐
1207 able when sudo is built with SELinux support.
1208 runas_default The default user to run commands as if the -u option is
1210 not specified on the command line. This defaults to
1211 root.
1212 syslog_badpri Syslog priority to use when user authenticates unsuc‐
1214 cessfully. Defaults to alert.
1215 The following syslog priorities are supported: alert,
1217 crit, debug, emerg, err, info, notice, and warning.
1218 syslog_goodpri Syslog priority to use when user authenticates success‐
1220 fully. Defaults to notice.
1221 See syslog_badpri for the list of supported syslog pri‐
1223 orities.
1224 sudoers_locale Locale to use when parsing the sudoers file, logging
1226 commands, and sending email. Note that changing the
1227 locale may affect how sudoers is interpreted. Defaults
1228 to “C”.
1229 timestampdir The directory in which sudo stores its time stamp
1231 files. The default is /var/db/sudo.
1232 timestampowner The owner of the time stamp directory and the time
1234 stamps stored therein. The default is root.
1235 type The default SELinux type to use when constructing a new
1237 security context to run the command. The default type
1238 may be overridden on a per-command basis in sudoers or
1239 via command line options. This option is only avail‐
1240 able when sudo is built with SELinux support.
1241 Strings that can be used in a boolean context:
1243 env_file The env_file option specifies the fully qualified path to a
1245 file containing variables to be set in the environment of
1246 the program being run. Entries in this file should either
1247 be of the form “VARIABLE=value” or “export VARIABLE=value”.
1248 The value may optionally be surrounded by single or double
1249 quotes. Variables in this file are subject to other sudo
1250 environment settings such as env_keep and env_check.
1251 exempt_group Users in this group are exempt from password and PATH
1253 requirements. The group name specified should not include
1254 a % prefix. This is not set by default.
1255 group_plugin A string containing a sudoers group plugin with optional
1257 arguments. This can be used to implement support for the
1258 nonunix_group syntax described earlier. The string should
1259 consist of the plugin path, either fully-qualified or rela‐
1260 tive to the /usr/libexec directory, followed by any config‐
1261 uration arguments the plugin requires. These arguments (if
1262 any) will be passed to the plugin's initialization func‐
1263 tion. If arguments are present, the string must be
1264 enclosed in double quotes ("").
1265 For example, given /etc/sudo-group, a group file in Unix
1267 group format, the sample group plugin can be used:
1268 Defaults group_plugin="sample_group.so /etc/sudo-group"
1270 For more information see sudo_plugin(5).
1272 lecture This option controls when a short lecture will be printed
1274 along with the password prompt. It has the following pos‐
1275 sible values:
1276 always Always lecture the user.
1278 never Never lecture the user.
1280 once Only lecture the user the first time they run sudo.
1282 If no value is specified, a value of once is implied.
1284 Negating the option results in a value of never being used.
1285 The default value is once.
1286 lecture_file Path to a file containing an alternate sudo lecture that
1288 will be used in place of the standard lecture if the named
1289 file exists. By default, sudo uses a built-in lecture.
1290 listpw This option controls when a password will be required when
1292 a user runs sudo with the -l option. It has the following
1293 possible values:
1294 all All the user's sudoers entries for the current
1296 host must have the NOPASSWD flag set to avoid
1297 entering a password.
1298 always The user must always enter a password to use the
1300 -l option.
1301 any At least one of the user's sudoers entries for
1303 the current host must have the NOPASSWD flag set
1304 to avoid entering a password.
1305 never The user need never enter a password to use the
1307 -l option.
1308 If no value is specified, a value of any is implied.
1310 Negating the option results in a value of never being used.
1311 The default value is any.
1312 logfile Path to the sudo log file (not the syslog log file). Set‐
1314 ting a path turns on logging to a file; negating this
1315 option turns it off. By default, sudo logs via syslog.
1316 mailerflags Flags to use when invoking mailer. Defaults to -t.
1318 mailerpath Path to mail program used to send warning mail. Defaults
1320 to the path to sendmail found at configure time.
1321 mailfrom Address to use for the “from” address when sending warning
1323 and error mail. The address should be enclosed in double
1324 quotes ("") to protect against sudo interpreting the @
1325 sign. Defaults to the name of the user running sudo.
1326 mailto Address to send warning and error mail to. The address
1328 should be enclosed in double quotes ("") to protect against
1329 sudo interpreting the @ sign. Defaults to root.
1330 secure_path Path used for every command run from sudo. If you don't
1332 trust the people running sudo to have a sane PATH environ‐
1333 ment variable you may want to use this. Another use is if
1334 you want to have the “root path” be separate from the “user
1335 path”. Users in the group specified by the exempt_group
1336 option are not affected by secure_path. This option is not
1337 set by default.
1338 syslog Syslog facility if syslog is being used for logging (negate
1340 to disable syslog logging). Defaults to authpriv.
1341 The following syslog facilities are supported: authpriv (if
1343 your OS supports it), auth, daemon, user, local0, local1,
1344 local2, local3, local4, local5, local6, and local7.
1345 verifypw This option controls when a password will be required when
1347 a user runs sudo with the -v option. It has the following
1348 possible values:
1349 all All the user's sudoers entries for the current host
1351 must have the NOPASSWD flag set to avoid entering a
1352 password.
1353 always The user must always enter a password to use the -v
1355 option.
1356 any At least one of the user's sudoers entries for the
1358 current host must have the NOPASSWD flag set to
1359 avoid entering a password.
1360 never The user need never enter a password to use the -v
1362 option.
1363 If no value is specified, a value of all is implied.
1365 Negating the option results in a value of never being used.
1366 The default value is all.
1367 Lists that can be used in a boolean context:
1369 env_check Environment variables to be removed from the user's
1371 environment if unless they are considered “safe”. For
1372 all variables except TZ, “safe” means that the vari‐
1373 able's value does not contain any ‘%’ or ‘/’ charac‐
1374 ters. This can be used to guard against printf-style
1375 format vulnerabilities in poorly-written programs. The
1376 TZ variable is considerd unsafe if any of the following
1377 are true:
1378 · It consists of a fully-qualified path name, option‐
1380 ally prefixed with a colon (‘:’), that does not
1381 match the location of the zoneinfo directory.
1382 · It contains a .. path element.
1384 · It contains white space or non-printable charac‐
1386 ters.
1387 · It is longer than the value of PATH_MAX.
1389 The argument may be a double-quoted, space-separated
1391 list or a single value without double-quotes. The list
1392 can be replaced, added to, deleted from, or disabled by
1393 using the =, +=, -=, and ! operators respectively.
1394 Regardless of whether the env_reset option is enabled
1395 or disabled, variables specified by env_check will be
1396 preserved in the environment if they pass the aforemen‐
1397 tioned check. The default list of environment vari‐
1398 ables to check is displayed when sudo is run by root
1399 with the -V option.
1400 env_delete Environment variables to be removed from the user's
1402 environment when the env_reset option is not in effect.
1403 The argument may be a double-quoted, space-separated
1404 list or a single value without double-quotes. The list
1405 can be replaced, added to, deleted from, or disabled by
1406 using the =, +=, -=, and ! operators respectively. The
1407 default list of environment variables to remove is dis‐
1408 played when sudo is run by root with the -V option.
1409 Note that many operating systems will remove poten‐
1410 tially dangerous variables from the environment of any
1411 setuid process (such as sudo).
1412 env_keep Environment variables to be preserved in the user's
1414 environment when the env_reset option is in effect.
1415 This allows fine-grained control over the environment
1416 sudo-spawned processes will receive. The argument may
1417 be a double-quoted, space-separated list or a single
1418 value without double-quotes. The list can be replaced,
1419 added to, deleted from, or disabled by using the =, +=,
1420 -=, and ! operators respectively. The default list of
1421 variables to keep is displayed when sudo is run by root
1422 with the -V option.
1423
1425 sudoers can log events using either syslog(3) or a simple log file. In
1426 each case the log format is almost identical.
1427 Accepted command log entries
1429 Commands that sudo runs are logged using the following format (split into
1430 multiple lines for readability):
1431 date hostname progname: username : TTY=ttyname ; PWD=cwd ; \
1433 USER=runasuser ; GROUP=runasgroup ; TSID=logid ; \
1434 ENV=env_vars COMMAND=command
1435 Where the fields are as follows:
1437 date The date the command was run. Typically, this is in the
1439 format “MMM, DD, HH:MM:SS”. If logging via syslog(3), the
1440 actual date format is controlled by the syslog daemon. If
1441 logging to a file and the log_year option is enabled, the
1442 date will also include the year.
1443 hostname The name of the host sudo was run on. This field is only
1445 present when logging via syslog(3).
1446 progname The name of the program, usually sudo or sudoedit. This
1448 field is only present when logging via syslog(3).
1449 username The login name of the user who ran sudo.
1451 ttyname The short name of the terminal (e.g. “console”, “tty01”, or
1453 “pts/0”) sudo was run on, or “unknown” if there was no ter‐
1454 minal present.
1455 cwd The current working directory that sudo was run in.
1457 runasuser The user the command was run as.
1459 runasgroup The group the command was run as if one was specified on
1461 the command line.
1462 logid An I/O log identifier that can be used to replay the com‐
1464 mand's output. This is only present when the log_input or
1465 log_output option is enabled.
1466 env_vars A list of environment variables specified on the command
1468 line, if specified.
1469 command The actual command that was executed.
1471 Messages are logged using the locale specified by sudoers_locale, which
1473 defaults to the “C” locale.
1474 Denied command log entries
1476 If the user is not allowed to run the command, the reason for the denial
1477 will follow the user name. Possible reasons include:
1478 user NOT in sudoers
1480 The user is not listed in the sudoers file.
1481 user NOT authorized on host
1483 The user is listed in the sudoers file but is not allowed to run com‐
1484 mands on the host.
1485 command not allowed
1487 The user is listed in the sudoers file for the host but they are not
1488 allowed to run the specified command.
1489 3 incorrect password attempts
1491 The user failed to enter their password after 3 tries. The actual num‐
1492 ber of tries will vary based on the number of failed attempts and the
1493 value of the passwd_tries option.
1494 a password is required
1496 sudo's -n option was specified but a password was required.
1497 sorry, you are not allowed to set the following environment variables
1499 The user specified environment variables on the command line that were
1500 not allowed by sudoers.
1501 Error log entries
1503 If an error occurs, sudoers will log a message and, in most cases, send a
1504 message to the administrator via email. Possible errors include:
1505 parse error in /etc/sudoers near line N
1507 sudoers encountered an error when parsing the specified file. In some
1508 cases, the actual error may be one line above or below the line number
1509 listed, depending on the type of error.
1510 problem with defaults entries
1512 The sudoers file contains one or more unknown Defaults settings. This
1513 does not prevent sudo from running, but the sudoers file should be
1514 checked using visudo.
1515 timestamp owner (username): No such user
1517 The time stamp directory owner, as specified by the timestampowner set‐
1518 ting, could not be found in the password database.
1519 unable to open/read /etc/sudoers
1521 The sudoers file could not be opened for reading. This can happen when
1522 the sudoers file is located on a remote file system that maps user ID 0
1523 to a different value. Normally, sudoers tries to open sudoers using
1524 group permissions to avoid this problem. Consider changing the owner‐
1525 ship of /etc/sudoers by adding an option like “sudoers_uid=N” (where
1526 ‘N’ is the user ID that owns the sudoers file) to the sudoers plugin
1527 line in the /etc/sudo.conf file.
1528 unable to stat /etc/sudoers
1530 The /etc/sudoers file is missing.
1531 /etc/sudoers is not a regular file
1533 The /etc/sudoers file exists but is not a regular file or symbolic
1534 link.
1535 /etc/sudoers is owned by uid N, should be 0
1537 The sudoers file has the wrong owner. If you wish to change the
1538 sudoers file owner, please add “sudoers_uid=N” (where ‘N’ is the user
1539 ID that owns the sudoers file) to the sudoers plugin line in the
1540 /etc/sudo.conf file.
1541 /etc/sudoers is world writable
1543 The permissions on the sudoers file allow all users to write to it.
1544 The sudoers file must not be world-writable, the default file mode is
1545 0440 (readable by owner and group, writable by none). The default mode
1546 may be changed via the “sudoers_mode” option to the sudoers plugin line
1547 in the /etc/sudo.conf file.
1548 /etc/sudoers is owned by gid N, should be 1
1550 The sudoers file has the wrong group ownership. If you wish to change
1551 the sudoers file group ownership, please add “sudoers_gid=N” (where ‘N’
1552 is the group ID that owns the sudoers file) to the sudoers plugin line
1553 in the /etc/sudo.conf file.
1554 unable to open /var/db/sudo/username/ttyname
1556 sudoers was unable to read or create the user's time stamp file.
1557 unable to write to /var/db/sudo/username/ttyname
1559 sudoers was unable to write to the user's time stamp file.
1560 unable to mkdir to /var/db/sudo/username
1562 sudoers was unable to create the user's time stamp directory.
1563 Notes on logging via syslog
1565 By default, sudoers logs messages via syslog(3). The date, hostname, and
1566 progname fields are added by the syslog daemon, not sudoers itself. As
1567 such, they may vary in format on different systems.
1568 On most systems, syslog(3) has a relatively small log buffer. To prevent
1570 the command line arguments from being truncated, sudoers will split up
1571 log messages that are larger than 960 characters (not including the date,
1572 hostname, and the string “sudo”). When a message is split, additional
1573 parts will include the string “(command continued)” after the user name
1574 and before the continued command line arguments.
1575 Notes on logging to a file
1577 If the logfile option is set, sudoers will log to a local file, such as
1578 /var/log/sudo. When logging to a file, sudoers uses a format similar to
1579 syslog(3), with a few important differences:
1580 1. The progname and hostname fields are not present.
1582 2. If the log_year option is enabled, the date will also include the
1584 year.
1585 3. Lines that are longer than loglinelen characters (80 by default) are
1587 word-wrapped and continued on the next line with a four character
1588 indent. This makes entries easier to read for a human being, but
1589 makes it more difficult to use grep(1) on the log files. If the
1590 loglinelen option is set to 0 (or negated with a ‘!’), word wrap
1591 will be disabled.
1592
1594 The /etc/sudo.conf file determines which plugins the sudo front end will
1595 load. If no /etc/sudo.conf file is present, or it contains no Plugin
1596 lines, sudo will use the sudoers security policy and I/O logging, which
1597 corresponds to the following /etc/sudo.conf file.
1598 #
1600 # Default /etc/sudo.conf file
1601 #
1602 # Format:
1603 # Plugin plugin_name plugin_path plugin_options ...
1604 # Path askpass /path/to/askpass
1605 # Path noexec /path/to/sudo_noexec.so
1606 # Debug sudo /var/log/sudo_debug all@warn
1607 # Set disable_coredump true
1608 #
1609 # The plugin_path is relative to /usr/libexec unless
1610 # fully qualified.
1611 # The plugin_name corresponds to a global symbol in the plugin
1612 # that contains the plugin interface structure.
1613 # The plugin_options are optional.
1614 #
1615 Plugin policy_plugin sudoers.so
1616 Plugin io_plugin sudoers.so
1617 Plugin options
1619 Starting with sudo 1.8.5, it is possible to pass options to the sudoers
1620 plugin. Options may be listed after the path to the plugin (i.e. after
1621 sudoers.so); multiple options should be space-separated. For example:
1622 Plugin sudoers_policy sudoers.so sudoers_file=/etc/sudoers sudoers_uid=0 sudoers_gid=0 sudoers_mode=0440
1624 The following plugin options are supported:
1626 sudoers_file=pathname
1628 The sudoers_file option can be used to override the default
1629 path to the sudoers file.
1630 sudoers_uid=uid
1632 The sudoers_uid option can be used to override the default
1633 owner of the sudoers file. It should be specified as a numeric
1634 user ID.
1635 sudoers_gid=gid
1637 The sudoers_gid option can be used to override the default
1638 group of the sudoers file. It should be specified as a numeric
1639 group ID.
1640 sudoers_mode=mode
1642 The sudoers_mode option can be used to override the default
1643 file mode for the sudoers file. It should be specified as an
1644 octal value.
1645 Debug flags
1647 Versions 1.8.4 and higher of the sudoers plugin supports a debugging
1648 framework that can help track down what the plugin is doing internally if
1649 there is a problem. This can be configured in the /etc/sudo.conf file as
1650 described in sudo(8).
1651 The sudoers plugin uses the same debug flag format as the sudo front-end:
1653 subsystem@priority.
1654 The priorities used by sudoers, in order of decreasing severity, are:
1656 crit, err, warn, notice, diag, info, trace and debug. Each priority,
1657 when specified, also includes all priorities higher than it. For exam‐
1658 ple, a priority of notice would include debug messages logged at notice
1659 and higher.
1660 The following subsystems are used by sudoers:
1662 alias User_Alias, Runas_Alias, Host_Alias and Cmnd_Alias processing
1664 all matches every subsystem
1666 audit BSM and Linux audit code
1668 auth user authentication
1670 defaults sudoers Defaults settings
1672 env environment handling
1674 ldap LDAP-based sudoers
1676 logging logging support
1678 match matching of users, groups, hosts and netgroups in sudoers
1680 netif network interface handling
1682 nss network service switch handling in sudoers
1684 parser sudoers file parsing
1686 perms permission setting
1688 plugin The equivalent of main for the plugin.
1690 pty pseudo-tty related code
1692 rbtree redblack tree internals
1694 util utility functions
1696
1698 /etc/sudo.conf Sudo front end configuration
1699 /etc/sudoers List of who can run what
1701 /etc/group Local groups file
1703 /etc/netgroup List of network groups
1705 /var/log/sudo-io I/O log files
1707 /var/db/sudo Directory containing time stamps for the
1709 sudoers security policy
1710 /etc/environment Initial environment for -i mode on AIX and
1712 Linux systems
1713
1715 Below are example sudoers entries. Admittedly, some of these are a bit
1716 contrived. First, we allow a few environment variables to pass and then
1717 define our aliases:
1718 # Run X applications through sudo; HOME is used to find the
1720 # .Xauthority file. Note that other programs use HOME to find
1721 # configuration files and this may lead to privilege escalation!
1722 Defaults env_keep += "DISPLAY HOME"
1723 # User alias specification
1725 User_Alias FULLTIMERS = millert, mikef, dowdy
1726 User_Alias PARTTIMERS = bostley, jwfox, crawl
1727 User_Alias WEBMASTERS = will, wendy, wim
1728 # Runas alias specification
1730 Runas_Alias OP = root, operator
1731 Runas_Alias DB = oracle, sybase
1732 Runas_Alias ADMINGRP = adm, oper
1733 # Host alias specification
1735 Host_Alias SPARC = bigtime, eclipse, moet, anchor :\
1736 SGI = grolsch, dandelion, black :\
1737 ALPHA = widget, thalamus, foobar :\
1738 HPPA = boa, nag, python
1739 Host_Alias CUNETS = 128.138.0.0/255.255.0.0
1740 Host_Alias CSNETS = 128.138.243.0, 128.138.204.0/24, 128.138.242.0
1741 Host_Alias SERVERS = master, mail, www, ns
1742 Host_Alias CDROM = orion, perseus, hercules
1743 # Cmnd alias specification
1745 Cmnd_Alias DUMPS = /usr/bin/mt, /usr/sbin/dump, /usr/sbin/rdump,\
1746 /usr/sbin/restore, /usr/sbin/rrestore
1747 Cmnd_Alias KILL = /usr/bin/kill
1748 Cmnd_Alias PRINTING = /usr/sbin/lpc, /usr/bin/lprm
1749 Cmnd_Alias SHUTDOWN = /usr/sbin/shutdown
1750 Cmnd_Alias HALT = /usr/sbin/halt
1751 Cmnd_Alias REBOOT = /usr/sbin/reboot
1752 Cmnd_Alias SHELLS = /usr/bin/sh, /usr/bin/csh, /usr/bin/ksh,\
1753 /usr/local/bin/tcsh, /usr/bin/rsh,\
1754 /usr/local/bin/zsh
1755 Cmnd_Alias SU = /usr/bin/su
1756 Cmnd_Alias PAGERS = /usr/bin/more, /usr/bin/pg, /usr/bin/less
1757 Here we override some of the compiled in default values. We want sudo to
1759 log via syslog(3) using the auth facility in all cases. We don't want to
1760 subject the full time staff to the sudo lecture, user millert need not
1761 give a password, and we don't want to reset the LOGNAME, USER or USERNAME
1762 environment variables when running commands as root. Additionally, on
1763 the machines in the SERVERS Host_Alias, we keep an additional local log
1764 file and make sure we log the year in each log line since the log entries
1765 will be kept around for several years. Lastly, we disable shell escapes
1766 for the commands in the PAGERS Cmnd_Alias (/usr/bin/more, /usr/bin/pg and
1767 /usr/bin/less).
1768 # Override built-in defaults
1770 Defaults syslog=auth
1771 Defaults>root !set_logname
1772 Defaults:FULLTIMERS !lecture
1773 Defaults:millert !authenticate
1774 Defaults@SERVERS log_year, logfile=/var/log/sudo.log
1775 Defaults!PAGERS noexec
1776 The User specification is the part that actually determines who may run
1778 what.
1779 root ALL = (ALL) ALL
1781 %wheel ALL = (ALL) ALL
1782 We let root and any user in group wheel run any command on any host as
1784 any user.
1785 FULLTIMERS ALL = NOPASSWD: ALL
1787 Full time sysadmins (millert, mikef, and dowdy) may run any command on
1789 any host without authenticating themselves.
1790 PARTTIMERS ALL = ALL
1792 Part time sysadmins bostley, jwfox, and crawl) may run any command on any
1794 host but they must authenticate themselves first (since the entry lacks
1795 the NOPASSWD tag).
1796 jack CSNETS = ALL
1798 The user jack may run any command on the machines in the CSNETS alias
1800 (the networks 128.138.243.0, 128.138.204.0, and 128.138.242.0). Of those
1801 networks, only 128.138.204.0 has an explicit netmask (in CIDR notation)
1802 indicating it is a class C network. For the other networks in CSNETS,
1803 the local machine's netmask will be used during matching.
1804 lisa CUNETS = ALL
1806 The user lisa may run any command on any host in the CUNETS alias (the
1808 class B network 128.138.0.0).
1809 operator ALL = DUMPS, KILL, SHUTDOWN, HALT, REBOOT, PRINTING,\
1811 sudoedit /etc/printcap, /usr/oper/bin/
1812 The operator user may run commands limited to simple maintenance. Here,
1814 those are commands related to backups, killing processes, the printing
1815 system, shutting down the system, and any commands in the directory
1816 /usr/oper/bin/.
1817 joe ALL = /usr/bin/su operator
1819 The user joe may only su(1) to operator.
1821 pete HPPA = /usr/bin/passwd [A-Za-z]*, !/usr/bin/passwd root
1823 %opers ALL = (: ADMINGRP) /usr/sbin/
1825 Users in the opers group may run commands in /usr/sbin/ as themselves
1827 with any group in the ADMINGRP Runas_Alias (the adm and oper groups).
1828 The user pete is allowed to change anyone's password except for root on
1830 the HPPA machines. Note that this assumes passwd(1) does not take multi‐
1831 ple user names on the command line.
1832 bob SPARC = (OP) ALL : SGI = (OP) ALL
1834 The user bob may run anything on the SPARC and SGI machines as any user
1836 listed in the OP Runas_Alias (root and operator.)
1837 jim +biglab = ALL
1839 The user jim may run any command on machines in the biglab netgroup.
1841 sudo knows that “biglab” is a netgroup due to the ‘+’ prefix.
1842 +secretaries ALL = PRINTING, /usr/bin/adduser, /usr/bin/rmuser
1844 Users in the secretaries netgroup need to help manage the printers as
1846 well as add and remove users, so they are allowed to run those commands
1847 on all machines.
1848 fred ALL = (DB) NOPASSWD: ALL
1850 The user fred can run commands as any user in the DB Runas_Alias (oracle
1852 or sybase) without giving a password.
1853 john ALPHA = /usr/bin/su [!-]*, !/usr/bin/su *root*
1855 On the ALPHA machines, user john may su to anyone except root but he is
1857 not allowed to specify any options to the su(1) command.
1858 jen ALL, !SERVERS = ALL
1860 The user jen may run any command on any machine except for those in the
1862 SERVERS Host_Alias (master, mail, www and ns).
1863 jill SERVERS = /usr/bin/, !SU, !SHELLS
1865 For any machine in the SERVERS Host_Alias, jill may run any commands in
1867 the directory /usr/bin/ except for those commands belonging to the SU and
1868 SHELLS Cmnd_Aliases.
1869 steve CSNETS = (operator) /usr/local/op_commands/
1871 The user steve may run any command in the directory /usr/local/op_com‐
1873 mands/ but only as user operator.
1874 matt valkyrie = KILL
1876 On his personal workstation, valkyrie, matt needs to be able to kill hung
1878 processes.
1879 WEBMASTERS www = (www) ALL, (root) /usr/bin/su www
1881 On the host www, any user in the WEBMASTERS User_Alias (will, wendy, and
1883 wim), may run any command as user www (which owns the web pages) or sim‐
1884 ply su(1) to www.
1885 ALL CDROM = NOPASSWD: /sbin/umount /CDROM,\
1887 /sbin/mount -o nosuidnodev /dev/cd0a /CDROM
1888 Any user may mount or unmount a CD-ROM on the machines in the CDROM
1890 Host_Alias (orion, perseus, hercules) without entering a password. This
1891 is a bit tedious for users to type, so it is a prime candidate for encap‐
1892 sulating in a shell script.
1893
1895 Limitations of the ‘!’ operator
1896 It is generally not effective to “subtract” commands from ALL using the
1897 ‘!’ operator. A user can trivially circumvent this by copying the
1898 desired command to a different name and then executing that. For exam‐
1899 ple:
1900 bill ALL = ALL, !SU, !SHELLS
1902 Doesn't really prevent bill from running the commands listed in SU or
1904 SHELLS since he can simply copy those commands to a different name, or
1905 use a shell escape from an editor or other program. Therefore, these
1906 kind of restrictions should be considered advisory at best (and rein‐
1907 forced by policy).
1908 In general, if a user has sudo ALL there is nothing to prevent them from
1910 creating their own program that gives them a root shell (or making their
1911 own copy of a shell) regardless of any ‘!’ elements in the user specifi‐
1912 cation.
1913 Security implications of fast_glob
1915 If the fast_glob option is in use, it is not possible to reliably negate
1916 commands where the path name includes globbing (aka wildcard) characters.
1917 This is because the C library's fnmatch(3) function cannot resolve rela‐
1918 tive paths. While this is typically only an inconvenience for rules that
1919 grant privileges, it can result in a security issue for rules that sub‐
1920 tract or revoke privileges.
1921 For example, given the following sudoers entry:
1923 john ALL = /usr/bin/passwd [a-zA-Z0-9]*, /usr/bin/chsh [a-zA-Z0-9]*,\
1925 /usr/bin/chfn [a-zA-Z0-9]*, !/usr/bin/* root
1926 User john can still run /usr/bin/passwd root if fast_glob is enabled by
1928 changing to /usr/bin and running ./passwd root instead.
1929 Preventing shell escapes
1931 Once sudo executes a program, that program is free to do whatever it
1932 pleases, including run other programs. This can be a security issue
1933 since it is not uncommon for a program to allow shell escapes, which lets
1934 a user bypass sudo's access control and logging. Common programs that
1935 permit shell escapes include shells (obviously), editors, paginators,
1936 mail and terminal programs.
1937 There are two basic approaches to this problem:
1939 restrict Avoid giving users access to commands that allow the user to
1941 run arbitrary commands. Many editors have a restricted mode
1942 where shell escapes are disabled, though sudoedit is a better
1943 solution to running editors via sudo. Due to the large number
1944 of programs that offer shell escapes, restricting users to the
1945 set of programs that do not is often unworkable.
1946 noexec Many systems that support shared libraries have the ability to
1948 override default library functions by pointing an environment
1949 variable (usually LD_PRELOAD) to an alternate shared library.
1950 On such systems, sudo's noexec functionality can be used to
1951 prevent a program run by sudo from executing any other pro‐
1952 grams. Note, however, that this applies only to native dynami‐
1953 cally-linked executables. Statically-linked executables and
1954 foreign executables running under binary emulation are not
1955 affected.
1956 The noexec feature is known to work on SunOS, Solaris, *BSD,
1958 Linux, IRIX, Tru64 UNIX, MacOS X, HP-UX 11.x and AIX 5.3 and
1959 above. It should be supported on most operating systems that
1960 support the LD_PRELOAD environment variable. Check your oper‐
1961 ating system's manual pages for the dynamic linker (usually
1962 ld.so, ld.so.1, dyld, dld.sl, rld, or loader) to see if
1963 LD_PRELOAD is supported.
1964 To enable noexec for a command, use the NOEXEC tag as docu‐
1966 mented in the User Specification section above. Here is that
1967 example again:
1968 aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
1970 This allows user aaron to run /usr/bin/more and /usr/bin/vi
1972 with noexec enabled. This will prevent those two commands from
1973 executing other commands (such as a shell). If you are unsure
1974 whether or not your system is capable of supporting noexec you
1975 can always just try it out and check whether shell escapes work
1976 when noexec is enabled.
1977 Note that restricting shell escapes is not a panacea. Programs running
1979 as root are still capable of many potentially hazardous operations (such
1980 as changing or overwriting files) that could lead to unintended privilege
1981 escalation. In the specific case of an editor, a safer approach is to
1982 give the user permission to run sudoedit.
1983 Time stamp file checks
1985 sudoers will check the ownership of its time stamp directory
1986 (/var/db/sudo by default) and ignore the directory's contents if it is
1987 not owned by root or if it is writable by a user other than root. On
1988 systems that allow non-root users to give away files via chown(2), if the
1989 time stamp directory is located in a world-writable directory (e.g.,
1990 /tmp), it is possible for a user to create the time stamp directory
1991 before sudo is run. However, because sudoers checks the ownership and
1992 mode of the directory and its contents, the only damage that can be done
1993 is to “hide” files by putting them in the time stamp dir. This is
1994 unlikely to happen since once the time stamp dir is owned by root and
1995 inaccessible by any other user, the user placing files there would be
1996 unable to get them back out.
1997 sudoers will not honor time stamps set far in the future. Time stamps
1999 with a date greater than current_time + 2 * TIMEOUT will be ignored and
2000 sudo will log and complain. This is done to keep a user from creating
2001 his/her own time stamp with a bogus date on systems that allow users to
2002 give away files if the time stamp directory is located in a world-
2003 writable directory.
2004 On systems where the boot time is available, sudoers will ignore time
2006 stamps that date from before the machine booted.
2007 Since time stamp files live in the file system, they can outlive a user's
2009 login session. As a result, a user may be able to login, run a command
2010 with sudo after authenticating, logout, login again, and run sudo without
2011 authenticating so long as the time stamp file's modification time is
2012 within 5 minutes (or whatever the timeout is set to in sudoers). When
2013 the tty_tickets option is enabled, the time stamp has per-tty granularity
2014 but still may outlive the user's session. On Linux systems where the
2015 devpts filesystem is used, Solaris systems with the devices filesystem,
2016 as well as other systems that utilize a devfs filesystem that monotoni‐
2017 cally increase the inode number of devices as they are created (such as
2018 Mac OS X), sudoers is able to determine when a tty-based time stamp file
2019 is stale and will ignore it. Administrators should not rely on this fea‐
2020 ture as it is not universally available.
2021
2023 ssh(1), su(1), fnmatch(3), glob(3), mktemp(3), strftime(3),
2024 sudoers.ldap(5), sudo_plugin(8), sudo(8), visudo(8)
2025
2027 The sudoers file should always be edited by the visudo command which
2028 locks the file and does grammatical checking. It is imperative that
2029 sudoers be free of syntax errors since sudo will not run with a syntacti‐
2030 cally incorrect sudoers file.
2031 When using netgroups of machines (as opposed to users), if you store
2033 fully qualified host name in the netgroup (as is usually the case), you
2034 either need to have the machine's host name be fully qualified as
2035 returned by the hostname command or use the fqdn option in sudoers.
2036
2038 If you feel you have found a bug in sudo, please submit a bug report at
2039 http://www.sudo.ws/sudo/bugs/
2040
2042 Limited free support is available via the sudo-users mailing list, see
2043 http://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search the
2044 archives.
2045
2047 sudo is provided “AS IS” and any express or implied warranties, includ‐
2048 ing, but not limited to, the implied warranties of merchantability and
2049 fitness for a particular purpose are disclaimed. See the LICENSE file
2050 distributed with sudo or http://www.sudo.ws/sudo/license.html for com‐
2051 plete details.
2052Sudo 1.8.6p3 July 16, 2012 Sudo 1.8.6p3