2 Copyright (c) 1994-1996,1998-2004 Todd C. Miller <Todd.Miller@courtesan.com>
4 Permission to use, copy, modify, and distribute this software for any
5 purpose with or without fee is hereby granted, provided that the above
6 copyright notice and this permission notice appear in all copies.
8 THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9 WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10 MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11 ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13 ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14 OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15 ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
17 Sponsored in part by the Defense Advanced Research Projects
18 Agency (DARPA) and Air Force Research Laboratory, Air Force
19 Materiel Command, USAF, under agreement number F39502-99-1-0512.
21 $Sudo: sudoers.pod,v 1.96 2004/09/06 20:45:27 millert Exp $
26 sudoers - list of which users may execute what
30 The I<sudoers> file is composed of two types of entries: aliases
31 (basically variables) and user specifications (which specify who
34 When multiple entries match for a user, they are applied in order.
35 Where there are conflicting values, the last match is used (which
36 is not necessarily the most specific match).
38 The I<sudoers> grammar will be described below in Extended Backus-Naur
39 Form (EBNF). Don't despair if you don't know what EBNF is; it is
40 fairly simple, and the definitions below are annotated.
42 =head2 Quick guide to EBNF
44 EBNF is a concise and exact way of describing the grammar of a language.
45 Each EBNF definition is made up of I<production rules>. E.g.,
47 symbol ::= definition | alternate1 | alternate2 ...
49 Each I<production rule> references others and thus makes up a
50 grammar for the language. EBNF also contains the following
51 operators, which many readers will recognize from regular
52 expressions. Do not, however, confuse them with "wildcard"
53 characters, which have different meanings.
59 Means that the preceding symbol (or group of symbols) is optional.
60 That is, it may appear once or not at all.
64 Means that the preceding symbol (or group of symbols) may appear
69 Means that the preceding symbol (or group of symbols) may appear
74 Parentheses may be used to group symbols together. For clarity,
75 we will use single quotes ('') to designate what is a verbatim character
76 string (as opposed to a symbol name).
80 There are four kinds of aliases: C<User_Alias>, C<Runas_Alias>,
81 C<Host_Alias> and C<Cmnd_Alias>.
83 Alias ::= 'User_Alias' User_Alias (':' User_Alias)* |
84 'Runas_Alias' Runas_Alias (':' Runas_Alias)* |
85 'Host_Alias' Host_Alias (':' Host_Alias)* |
86 'Cmnd_Alias' Cmnd_Alias (':' Cmnd_Alias)*
88 User_Alias ::= NAME '=' User_List
90 Runas_Alias ::= NAME '=' Runas_List
92 Host_Alias ::= NAME '=' Host_List
94 Cmnd_Alias ::= NAME '=' Cmnd_List
96 NAME ::= [A-Z]([a-z][A-Z][0-9]_)*
98 Each I<alias> definition is of the form
100 Alias_Type NAME = item1, item2, ...
102 where I<Alias_Type> is one of C<User_Alias>, C<Runas_Alias>, C<Host_Alias>,
103 or C<Cmnd_Alias>. A C<NAME> is a string of uppercase letters, numbers,
104 and underscore characters ('_'). A C<NAME> B<must> start with an
105 uppercase letter. It is possible to put several alias definitions
106 of the same type on a single line, joined by a colon (':'). E.g.,
108 Alias_Type NAME = item1, item2, item3 : NAME = item4, item5
110 The definitions of what constitutes a valid I<alias> member follow.
115 User ::= '!'* username |
120 A C<User_List> is made up of one or more usernames, system groups
121 (prefixed with '%'), netgroups (prefixed with '+') and other aliases.
122 Each list item may be prefixed with one or more '!' operators.
123 An odd number of '!' operators negate the value of the item; an even
124 number just cancel each other out.
126 Runas_List ::= Runas_User |
127 Runas_User ',' Runas_List
129 Runas_User ::= '!'* username |
135 A C<Runas_List> is similar to a C<User_List> except that it can
136 also contain uids (prefixed with '#') and instead of C<User_Alias>es
137 it can contain C<Runas_Alias>es. Note that usernames and groups
138 are matched as strings. In other words, two users (groups) with
139 the same uid (gid) are considered to be distinct. If you wish to
140 match all usernames with the same uid (e.g. root and toor), you
141 can use a uid instead (#0 in the example given).
146 Host ::= '!'* hostname |
148 '!'* network(/netmask)? |
152 A C<Host_List> is made up of one or more hostnames, IP addresses,
153 network numbers, netgroups (prefixed with '+') and other aliases.
154 Again, the value of an item may be negated with the '!' operator.
155 If you do not specify a netmask with a network number, the netmask
156 of the host's ethernet interface(s) will be used when matching.
157 The netmask may be specified either in dotted quad notation (e.g.
158 255.255.255.0) or CIDR notation (number of bits, e.g. 24). A hostname
159 may include shell-style wildcards (see the L<Wildcards> section below),
160 but unless the C<hostname> command on your machine returns the fully
161 qualified hostname, you'll need to use the I<fqdn> option for wildcards
167 commandname ::= filename |
171 Cmnd ::= '!'* commandname |
176 A C<Cmnd_List> is a list of one or more commandnames, directories, and other
177 aliases. A commandname is a fully qualified filename which may include
178 shell-style wildcards (see the L<Wildcards> section below). A simple
179 filename allows the user to run the command with any arguments he/she
180 wishes. However, you may also specify command line arguments (including
181 wildcards). Alternately, you can specify C<""> to indicate that the command
182 may only be run B<without> command line arguments. A directory is a
183 fully qualified pathname ending in a '/'. When you specify a directory
184 in a C<Cmnd_List>, the user will be able to run any file within that directory
185 (but not in any subdirectories therein).
187 If a C<Cmnd> has associated command line arguments, then the arguments
188 in the C<Cmnd> must match exactly those given by the user on the command line
189 (or match the wildcards if there are any). Note that the following
190 characters must be escaped with a '\' if they are used in command
191 arguments: ',', ':', '=', '\'. The special command C<"sudoedit">
192 is used to permit a user to run B<sudo> with the B<-e> flag (or
193 as B<sudoedit>). It may take command line arguments just as
194 a normal command does.
198 Certain configuration options may be changed from their default
199 values at runtime via one or more C<Default_Entry> lines. These
200 may affect all users on any host, all users on a specific host, a
201 specific user, or commands being run as a specific user.
203 Default_Type ::= 'Defaults' |
204 'Defaults' '@' Host |
205 'Defaults' ':' User |
206 'Defaults' '>' RunasUser
208 Default_Entry ::= Default_Type Parameter_List
210 Parameter_List ::= Parameter |
211 Parameter ',' Parameter_List
213 Parameter ::= Parameter '=' Value |
214 Parameter '+=' Value |
215 Parameter '-=' Value |
218 Parameters may be B<flags>, B<integer> values, B<strings>, or B<lists>.
219 Flags are implicitly boolean and can be turned off via the '!'
220 operator. Some integer, string and list parameters may also be
221 used in a boolean context to disable them. Values may be enclosed
222 in double quotes (C<">) when they contain multiple words. Special
223 characters may be escaped with a backslash (C<\>).
225 Lists have two additional assignment operators, C<+=> and C<-=>.
226 These operators are used to add to and delete from a list respectively.
227 It is not an error to use the C<-=> operator to remove an element
228 that does not exist in a list.
234 =item long_otp_prompt
236 When validating with a One Time Password scheme (B<S/Key> or B<OPIE>),
237 a two-line prompt is used to make it easier to cut and paste the
238 challenge to a local window. It's not as pretty as the default but
239 some people find it more convenient. This flag is I<@long_otp_prompt@>
244 If set, B<sudo> will ignore '.' or '' (current dir) in the C<PATH>
245 environment variable; the C<PATH> itself is not modified. This
246 flag is I<@ignore_dot@> by default. Currently, while it is possible
247 to set I<ignore_dot> in I<sudoers>, its value is not used. This option
248 should be considered read-only (it will be fixed in a future version
253 Send mail to the I<mailto> user every time a users runs B<sudo>.
254 This flag is I<off> by default.
258 Send mail to the I<mailto> user if the user running sudo does not
259 enter the correct password. This flag is I<off> by default.
263 If set, mail will be sent to the I<mailto> user if the invoking
264 user is not in the I<sudoers> file. This flag is I<@mail_no_user@>
269 If set, mail will be sent to the I<mailto> user if the invoking
270 user exists in the I<sudoers> file, but is not allowed to run
271 commands on the current host. This flag is I<@mail_no_host@> by default.
275 If set, mail will be sent to the I<mailto> user if the invoking
276 user is allowed to use B<sudo> but the command they are trying is not
277 listed in their I<sudoers> file entry or is explicitly denied.
278 This flag is I<@mail_no_perms@> by default.
282 If set, users must authenticate on a per-tty basis. Normally,
283 B<sudo> uses a directory in the ticket dir with the same name as
284 the user running it. With this flag enabled, B<sudo> will use a
285 file named for the tty the user is logged in on in that directory.
286 This flag is I<@tty_tickets@> by default.
290 If set, users must authenticate themselves via a password (or other
291 means of authentication) before they may run commands. This default
292 may be overridden via the C<PASSWD> and C<NOPASSWD> tags.
293 This flag is I<on> by default.
297 If set, root is allowed to run B<sudo> too. Disabling this prevents users
298 from "chaining" B<sudo> commands to get a root shell by doing something
299 like C<"sudo sudo /bin/sh">. Note, however, that turning off I<root_sudo>
300 will also prevent root and from running B<sudoedit>.
301 Disabling I<root_sudo> provides no real additional security; it
302 exists purely for historical reasons.
303 This flag is I<@root_sudo@> by default.
307 If set, the hostname will be logged in the (non-syslog) B<sudo> log file.
308 This flag is I<off> by default.
312 If set, the four-digit year will be logged in the (non-syslog) B<sudo> log file.
313 This flag is I<off> by default.
317 If set and B<sudo> is invoked with no arguments it acts as if the
318 B<-s> flag had been given. That is, it runs a shell as root (the
319 shell is determined by the C<SHELL> environment variable if it is
320 set, falling back on the shell listed in the invoking user's
321 /etc/passwd entry if not). This flag is I<off> by default.
325 If set and B<sudo> is invoked with the B<-s> flag the C<HOME>
326 environment variable will be set to the home directory of the target
327 user (which is root unless the B<-u> option is used). This effectively
328 makes the B<-s> flag imply B<-H>. This flag is I<off> by default.
330 =item always_set_home
332 If set, B<sudo> will set the C<HOME> environment variable to the home
333 directory of the target user (which is root unless the B<-u> option is used).
334 This effectively means that the B<-H> flag is always implied.
335 This flag is I<off> by default.
339 Normally, B<sudo> will tell the user when a command could not be
340 found in their C<PATH> environment variable. Some sites may wish
341 to disable this as it could be used to gather information on the
342 location of executables that the normal user does not have access
343 to. The disadvantage is that if the executable is simply not in
344 the user's C<PATH>, B<sudo> will tell the user that they are not
345 allowed to run it, which can be confusing. This flag is I<off> by
348 =item preserve_groups
350 By default B<sudo> will initialize the group vector to the list of
351 groups the target user is in. When I<preserve_groups> is set, the
352 user's existing group vector is left unaltered. The real and
353 effective group IDs, however, are still set to match the target
354 user. This flag is I<off> by default.
358 Set this flag if you want to put fully qualified hostnames in the
359 I<sudoers> file. I.e., instead of myhost you would use myhost.mydomain.edu.
360 You may still use the short form if you wish (and even mix the two).
361 Beware that turning on I<fqdn> requires B<sudo> to make DNS lookups
362 which may make affect B<sudo> performance if DNS stops working (for example
363 if the machine is not plugged into the network). The default behavior for
364 Debian has been modified to minimize the potential of a problem, but there
365 may still be some cases in which lack of working DNS might make sudo work
366 very slowly. Also note that
367 you must use the host's official name as DNS knows it. That is,
368 you may not use a host alias (C<CNAME> entry) due to performance
369 issues and the fact that there is no way to get all aliases from
370 DNS. If your machine's hostname (as returned by the C<hostname>
371 command) is already fully qualified you shouldn't need to set
372 I<fqdn>. This flag is I<@fqdn@> by default.
376 If set, B<sudo> will insult users when they enter an incorrect
377 password. This flag is I<@insults@> by default.
381 If set, B<sudo> will only run when the user is logged in to a real
382 tty. This will disallow things like C<"rsh somehost sudo ls"> since
383 L<rsh(1)> does not allocate a tty. Because it is not possible to turn
384 off echo when there is no tty present, some sites may wish to set
385 this flag to prevent a user from entering a visible password. This
386 flag is I<off> by default.
390 If set, B<visudo> will use the value of the EDITOR or VISUAL
391 environment variables before falling back on the default editor list.
392 Note that this may create a security hole as it allows the user to
393 run any arbitrary command as root without logging. A safer alternative
394 is to place a colon-separated list of editors in the C<editor>
395 variable. B<visudo> will then only use the EDITOR or VISUAL if
396 they match a value specified in C<editor>. This flag is C<@env_editor@> by
401 If set, B<sudo> will prompt for the root password instead of the password
402 of the invoking user. This flag is I<off> by default.
406 If set, B<sudo> will prompt for the password of the user defined by the
407 I<runas_default> option (defaults to C<@runas_default@>) instead of the
408 password of the invoking user. This flag is I<off> by default.
412 If set, B<sudo> will prompt for the password of the user specified by
413 the B<-u> flag (defaults to C<root>) instead of the password of the
414 invoking user. Note that this precludes the use of a uid not listed
415 in the passwd database as an argument to the B<-u> flag.
416 This flag is I<off> by default.
420 Normally, B<sudo> will set the C<LOGNAME> and C<USER> environment variables
421 to the name of the target user (usually root unless the B<-u> flag is given).
422 However, since some programs (including the RCS revision control system)
423 use C<LOGNAME> to determine the real identity of the user, it may be desirable
424 to change this behavior. This can be done by negating the set_logname option.
428 Normally, when B<sudo> executes a command the real and effective
429 UIDs are set to the target user (root by default). This option
430 changes that behavior such that the real UID is left as the invoking
431 user's UID. In other words, this makes B<sudo> act as a setuid
432 wrapper. This can be useful on systems that disable some potentially
433 dangerous functionality when a program is run setuid. Note, however,
434 that this means that sudo will run with the real uid of the invoking
435 user which may allow that user to kill B<sudo> before it can log a
436 failure, depending on how your OS defines the interaction between
437 signals and setuid processes.
441 If set, B<sudo> will reset the environment to only contain the
442 following variables: C<HOME>, C<LOGNAME>, C<PATH>, C<SHELL>, C<TERM>,
443 C<DISPLAY>, C<XAUTHORITY>, C<XAUTHORIZATION>,
444 C<LANG>, C<LANGUAGE>, C<LC_*>,
445 and C<USER> (in addition to the C<SUDO_*> variables).
447 Of these, only C<TERM>, C<DISPLAY>, C<XAUTHORITY>, C<XAUTHORIZATION>,
448 C<LANG>, C<LANGUAGE>, and C<LC_*> are copied unaltered from the old environment.
449 The other variables are set to default values (possibly modified
450 by the value of the I<set_logname> option). If B<sudo> was compiled
451 with the C<SECURE_PATH> option, its value will be used for the C<PATH>
452 environment variable.
454 This option is enabled by default.
456 Other variables may be preserved with the I<env_keep> option.
460 If set, B<sudo> will apply the defaults specified for the target user's
461 login class if one exists. Only available if B<sudo> is configured with
462 the --with-logincap option. This flag is I<off> by default.
466 If set, all commands run via sudo will behave as if the C<NOEXEC>
467 tag has been set, unless overridden by a C<EXEC> tag. See the
468 description of I<NOEXEC and EXEC> below as well as the L<PREVENTING SHELL
469 ESCAPES> section at the end of this manual. This flag is I<off> by default.
471 =item ignore_local_sudoers
473 If set via LDAP, parsing of @sysconfdir@/sudoers will be skipped.
474 This is intended for an Enterprises that wish to prevent the usage of local
475 sudoers files so that only LDAP is used. This thwarts the efforts of
476 rogue operators who would attempt to add roles to @sysconfdir@/sudoers.
477 When this option is present, @sysconfdir@/sudoers does not even need to exist.
478 Since this options tells sudo how to behave when no specific LDAP entries
479 have been matched, this sudoOption is only meaningful for the cn=defaults
480 section. This flag is I<off> by default.
490 The number of tries a user gets to enter his/her password before
491 B<sudo> logs the failure and exits. The default is C<@passwd_tries@>.
495 B<Integers that can be used in a boolean context>:
501 Number of characters per line for the file log. This value is used
502 to decide when to wrap lines for nicer log files. This has no
503 effect on the syslog log file, only the file log. The default is
504 C<@loglen@> (use 0 or negate the option to disable word wrap).
506 =item timestamp_timeout
508 Number of minutes that can elapse before B<sudo> will ask for a
509 passwd again. The default is C<@timeout@>. Set this to C<0> to always
510 prompt for a password.
511 If set to a value less than C<0> the user's timestamp will never
512 expire. This can be used to allow users to create or delete their
513 own timestamps via C<sudo -v> and C<sudo -k> respectively.
517 Number of minutes before the B<sudo> password prompt times out.
518 The default is C<@password_timeout@>, set this to C<0> for no password timeout.
522 Umask to use when running the command. Negate this option or set
523 it to 0777 to preserve the user's umask. The default is C<@sudo_umask@>.
533 Subject of the mail sent to the I<mailto> user. The escape C<%h>
534 will expand to the hostname of the machine.
535 Default is C<@mailsub@>.
537 =item badpass_message
539 Message that is displayed if a user enters an incorrect password.
540 The default is C<@badpass_message@> unless insults are enabled.
544 The directory in which B<sudo> stores its timestamp files.
545 The default is F<@timedir@>.
549 The owner of the timestamp directory and the timestamps stored therein.
550 The default is C<root>.
554 The default prompt to use when asking for a password; can be overridden
555 via the B<-p> option or the C<SUDO_PROMPT> environment variable.
556 The following percent (`C<%>') escapes are supported:
562 expanded to the invoking user's login name
566 expanded to the login name of the user the command will
567 be run as (defaults to root)
571 expanded to the local hostname without the domain name
575 expanded to the local hostname including the domain name
576 (on if the machine's hostname is fully qualified or the I<fqdn>
581 two consecutive C<%> characters are collapsed into a single C<%> character
585 The default value is C<@passprompt@>.
589 The default user to run commands as if the B<-u> flag is not specified
590 on the command line. This defaults to C<@runas_default@>.
591 Note that if I<runas_default> is set it B<must> occur before
592 any C<Runas_Alias> specifications.
596 Syslog priority to use when user authenticates successfully.
597 Defaults to C<@goodpri@>.
601 Syslog priority to use when user authenticates unsuccessfully.
602 Defaults to C<@badpri@>.
606 A colon (':') separated list of editors allowed to be used with
607 B<visudo>. B<visudo> will choose the editor that matches the user's
608 USER environment variable if possible, or the first editor in the
609 list that exists and is executable. The default is the path to vi
614 Path to a shared library containing dummy versions of the execv(),
615 execve() and fexecve() library functions that just return an error.
616 This is used to implement the I<noexec> functionality on systems that
617 support C<LD_PRELOAD> or its equivalent. Defaults to F<@noexec_file@>.
621 B<Strings that can be used in a boolean context>:
627 This option controls when a short lecture will be printed along with
628 the password prompt. It has the following possible values:
634 Never lecture the user.
638 Only lecture the user the first time they run B<sudo>.
642 Always lecture the user.
646 If no value is specified, a value of I<once> is implied.
647 Negating the option results in a value of I<never> being used.
648 The default value is I<@lecture@>.
652 Path to a file containing an alternate sudo lecture that will
653 be used in place of the standard lecture if the named file exists.
657 Path to the B<sudo> log file (not the syslog log file). Setting a path
658 turns on logging to a file; negating this option turns it off.
662 Syslog facility if syslog is being used for logging (negate to
663 disable syslog logging). Defaults to C<@logfac@>.
667 Path to mail program used to send warning mail.
668 Defaults to the path to sendmail found at configure time.
672 Flags to use when invoking mailer. Defaults to B<-t>.
676 Address to send warning and error mail to. The address should
677 be enclosed in double quotes (C<">) to protect against sudo
678 interpreting the C<@> sign. Defaults to C<@mailto@>.
682 Users in this group are exempt from password and PATH requirements. This
683 option is turned on for Debian.
687 This option controls when a password will be required when a user runs
688 B<sudo> with the B<-v> flag. It has the following possible values:
694 All the user's I<sudoers> entries for the current host must have
695 the C<NOPASSWD> flag set to avoid entering a password.
699 At least one of the user's I<sudoers> entries for the current host
700 must have the C<NOPASSWD> flag set to avoid entering a password.
704 The user need never enter a password to use the B<-v> flag.
708 The user must always enter a password to use the B<-v> flag.
712 If no value is specified, a value of I<all> is implied.
713 Negating the option results in a value of I<never> being used.
714 The default value is I<all>.
718 This option controls when a password will be required when a
719 user runs B<sudo> with the B<-l> flag. It has the following possible values:
725 All the user's I<sudoers> entries for the current host must have
726 the C<NOPASSWD> flag set to avoid entering a password.
730 At least one of the user's I<sudoers> entries for the current host
731 must have the C<NOPASSWD> flag set to avoid entering a password.
735 The user need never enter a password to use the B<-l> flag.
739 The user must always enter a password to use the B<-l> flag.
743 If no value is specified, a value of I<any> is implied.
744 Negating the option results in a value of I<never> being used.
745 The default value is I<any>.
749 B<Lists that can be used in a boolean context>:
755 Like I<env_keep>, but listed environment variables are taken from the user's environment if
756 the variable's value does B<not> contain C<%> or C</> characters. This can
757 be used to guard against printf-style format vulnerabilities in
758 poorly-written programs. The argument may be a double-quoted,
759 space-separated list or a single value without double-quotes. The
760 list can be replaced, added to, deleted from, or disabled by using
761 the C<=>, C<+=>, C<-=>, and C<!> operators respectively. The default
762 list of environment variables to check is printed when B<sudo> is
763 run by root with the I<-V> option.
768 Not effective due to security issues: only variables listed in
769 I<env_keep> or I<env_check> can be passed through B<sudo>!
771 The argument may be a double-quoted, space-separated list or a
772 single value without double-quotes. The list can be replaced, added
773 to, deleted from, or disabled by using the C<=>, C<+=>, C<-=>, and
774 C<!> operators respectively. The default list of environment
775 variables to remove is printed when B<sudo> is run by root with the
776 I<-V> option. Note that many operating systems will remove potentially
777 dangerous variables from the environment of any setuid process (such
782 Environment variables to be preserved in the user's environment.
783 This allows fine-grained
784 control over the environment B<sudo>-spawned processes will receive.
785 The argument may be a double-quoted, space-separated list or a
786 single value without double-quotes. The list can be replaced, added
787 to, deleted from, or disabled by using the C<=>, C<+=>, C<-=>, and
788 C<!> operators respectively. This list has no default members.
792 When logging via L<syslog(3)>, B<sudo> accepts the following values
793 for the syslog facility (the value of the B<syslog> Parameter):
794 B<authpriv> (if your OS supports it), B<auth>, B<daemon>, B<user>,
795 B<local0>, B<local1>, B<local2>, B<local3>, B<local4>, B<local5>,
796 B<local6>, and B<local7>. The following syslog priorities are
797 supported: B<alert>, B<crit>, B<debug>, B<emerg>, B<err>, B<info>,
798 B<notice>, and B<warning>.
800 =head2 User Specification
802 User_Spec ::= User_List Host_List '=' Cmnd_Spec_List \
803 (':' Host_List '=' Cmnd_Spec_List)*
805 Cmnd_Spec_List ::= Cmnd_Spec |
806 Cmnd_Spec ',' Cmnd_Spec_List
808 Cmnd_Spec ::= Runas_Spec? Tag_Spec* Cmnd
810 Runas_Spec ::= '(' Runas_List ')'
812 Tag_Spec ::= ('NOPASSWD:' | 'PASSWD:' | 'NOEXEC:' | 'EXEC:')
814 A B<user specification> determines which commands a user may run
815 (and as what user) on specified hosts. By default, commands are
816 run as B<root>, but this can be changed on a per-command basis.
818 Let's break that down into its constituent parts:
822 A C<Runas_Spec> is simply a C<Runas_List> (as defined above)
823 enclosed in a set of parentheses. If you do not specify a
824 C<Runas_Spec> in the user specification, a default C<Runas_Spec>
825 of B<root> will be used. A C<Runas_Spec> sets the default for
826 commands that follow it. What this means is that for the entry:
828 dgb boulder = (operator) /bin/ls, /bin/kill, /usr/bin/lprm
830 The user B<dgb> may run F</bin/ls>, F</bin/kill>, and
831 F</usr/bin/lprm> -- but only as B<operator>. E.g.,
833 $ sudo -u operator /bin/ls.
835 It is also possible to override a C<Runas_Spec> later on in an
836 entry. If we modify the entry like so:
838 dgb boulder = (operator) /bin/ls, (root) /bin/kill, /usr/bin/lprm
840 Then user B<dgb> is now allowed to run F</bin/ls> as B<operator>,
841 but F</bin/kill> and F</usr/bin/lprm> as B<root>.
845 A command may have zero or more tags associated with it. There are
846 four possible tag values, C<NOPASSWD>, C<PASSWD>, C<NOEXEC>, C<EXEC>.
847 Once a tag is set on a C<Cmnd>, subsequent C<Cmnd>s in the
848 C<Cmnd_Spec_List>, inherit the tag unless it is overridden by the
849 opposite tag (ie: C<PASSWD> overrides C<NOPASSWD> and C<EXEC>
850 overrides C<NOEXEC>).
852 =head3 NOPASSWD and PASSWD
854 By default, B<sudo> requires that a user authenticate him or herself
855 before running a command. This behavior can be modified via the
856 C<NOPASSWD> tag. Like a C<Runas_Spec>, the C<NOPASSWD> tag sets
857 a default for the commands that follow it in the C<Cmnd_Spec_List>.
858 Conversely, the C<PASSWD> tag can be used to reverse things.
861 ray rushmore = NOPASSWD: /bin/kill, /bin/ls, /usr/bin/lprm
863 would allow the user B<ray> to run F</bin/kill>, F</bin/ls>, and
864 F</usr/bin/lprm> as root on the machine rushmore as B<root> without
865 authenticating himself. If we only want B<ray> to be able to
866 run F</bin/kill> without a password the entry would be:
868 ray rushmore = NOPASSWD: /bin/kill, PASSWD: /bin/ls, /usr/bin/lprm
870 Note, however, that the C<PASSWD> tag has no effect on users who are
871 in the group specified by the exempt_group option.
873 By default, if the C<NOPASSWD> tag is applied to any of the entries
874 for a user on the current host, he or she will be able to run
875 C<sudo -l> without a password. Additionally, a user may only run
876 C<sudo -v> without a password if the C<NOPASSWD> tag is present
877 for all a user's entries that pertain to the current host.
878 This behavior may be overridden via the verifypw and listpw options.
880 =head3 NOEXEC and EXEC
882 If sudo has been compiled with I<noexec> support and the underlying
883 operating system supports it, the C<NOEXEC> tag can be used to prevent
884 a dynamically-linked executable from running further commands itself.
886 In the following example, user B<aaron> may run F</usr/bin/more>
887 and F</usr/bin/vi> but shell escapes will be disabled.
889 aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
891 See the L<PREVENTING SHELL ESCAPES> section below for more details
892 on how I<noexec> works and whether or not it will work on your system.
896 B<sudo> allows shell-style I<wildcards> (aka meta or glob characters)
897 to be used in pathnames as well as command line arguments in the
898 I<sudoers> file. Wildcard matching is done via the B<POSIX>
899 L<fnmatch(3)> routine. Note that these are I<not> regular expressions.
905 Matches any set of zero or more characters.
909 Matches any single character.
913 Matches any character in the specified range.
917 Matches any character B<not> in the specified range.
921 For any character "x", evaluates to "x". This is used to
922 escape special characters such as: "*", "?", "[", and "}".
926 Note that a forward slash ('/') will B<not> be matched by
927 wildcards used in the pathname. When matching the command
928 line arguments, however, a slash B<does> get matched by
929 wildcards. This is to make a path like:
933 match F</usr/bin/who> but not F</usr/bin/X11/xterm>.
935 WARNING: a pathname with wildcards will B<not> match a user command
936 that consists of a relative path. In other words, given the
937 following I<sudoers> entry:
939 billy workstation = /usr/bin/*
941 user billy will be able to run any command in /usr/bin as root, such
942 as F</usr/bin/w>. The following two command will be allowed (the first
943 assumes that F</usr/bin> is in the user's path):
948 However, this will not:
953 For this reason you should only B<grant> access to commands using
954 wildcards and never B<restrict> access using them. This limitation
955 will be removed in a future version of B<sudo>.
957 =head2 Exceptions to wildcard rules
959 The following exceptions apply to the above rules:
965 If the empty string C<""> is the only command line argument in the
966 I<sudoers> entry it means that command is not allowed to be run
967 with B<any> arguments.
971 =head2 Other special characters and reserved words
973 The pound sign ('#') is used to indicate a comment (unless it
974 occurs in the context of a user name and is followed by one or
975 more digits, in which case it is treated as a uid). Both the
976 comment character and any text after it, up to the end of the line,
979 The reserved word B<ALL> is a built-in I<alias> that always causes
980 a match to succeed. It can be used wherever one might otherwise
981 use a C<Cmnd_Alias>, C<User_Alias>, C<Runas_Alias>, or C<Host_Alias>.
982 You should not try to define your own I<alias> called B<ALL> as the
983 built-in alias will be used in preference to your own. Please note
984 that using B<ALL> can be dangerous since in a command context, it
985 allows the user to run B<any> command on the system.
987 An exclamation point ('!') can be used as a logical I<not> operator
988 both in an I<alias> and in front of a C<Cmnd>. This allows one to
989 exclude certain values. Note, however, that using a C<!> in
990 conjunction with the built-in C<ALL> alias to allow a user to
991 run "all but a few" commands rarely works as intended (see SECURITY
994 Long lines can be continued with a backslash ('\') as the last
995 character on the line.
997 Whitespace between elements in a list as well as special syntactic
998 characters in a I<User Specification> ('=', ':', '(', ')') is optional.
1000 The following characters must be escaped with a backslash ('\') when
1001 used as part of a word (e.g. a username or hostname):
1002 '@', '!', '=', ':', ',', '(', ')', '\'.
1006 @sysconfdir@/sudoers List of who can run what
1007 /etc/group Local groups file
1008 /etc/netgroup List of network groups
1012 Since the I<sudoers> file is parsed in a single pass, order is
1013 important. In general, you should structure I<sudoers> such that
1014 the C<Host_Alias>, C<User_Alias>, and C<Cmnd_Alias> specifications
1015 come first, followed by any C<Default_Entry> lines, and finally the
1016 C<Runas_Alias> and user specifications. The basic rule of thumb
1017 is that you cannot reference an Alias that has not already been defined.
1019 Below are example I<sudoers> entries. Admittedly, some of
1020 these are a bit contrived. First, we allow a few environment
1021 variables to pass and then define our I<aliases>:
1023 # Run X applications through sudo; HOME is used to find .Xauthority file
1024 # Note that some programs may use HOME for other purposes too and
1025 # this may lead to privilege escalation!
1026 Defaults env_keep = "DISPLAY HOME"
1028 # User alias specification
1029 User_Alias FULLTIMERS = millert, mikef, dowdy
1030 User_Alias PARTTIMERS = bostley, jwfox, crawl
1031 User_Alias WEBMASTERS = will, wendy, wim
1033 # Runas alias specification
1034 Runas_Alias OP = root, operator
1035 Runas_Alias DB = oracle, sybase
1037 # Host alias specification
1038 Host_Alias SPARC = bigtime, eclipse, moet, anchor :\
1039 SGI = grolsch, dandelion, black :\
1040 ALPHA = widget, thalamus, foobar :\
1041 HPPA = boa, nag, python
1042 Host_Alias CUNETS = 128.138.0.0/255.255.0.0
1043 Host_Alias CSNETS = 128.138.243.0, 128.138.204.0/24, 128.138.242.0
1044 Host_Alias SERVERS = master, mail, www, ns
1045 Host_Alias CDROM = orion, perseus, hercules
1047 # Cmnd alias specification
1048 Cmnd_Alias DUMPS = /usr/bin/mt, /usr/sbin/dump, /usr/sbin/rdump,\
1049 /usr/sbin/restore, /usr/sbin/rrestore
1050 Cmnd_Alias KILL = /usr/bin/kill
1051 Cmnd_Alias PRINTING = /usr/sbin/lpc, /usr/bin/lprm
1052 Cmnd_Alias SHUTDOWN = /usr/sbin/shutdown
1053 Cmnd_Alias HALT = /usr/sbin/halt
1054 Cmnd_Alias REBOOT = /usr/sbin/reboot
1055 Cmnd_Alias SHELLS = /usr/bin/sh, /usr/bin/csh, /usr/bin/ksh, \
1056 /usr/local/bin/tcsh, /usr/bin/rsh, \
1058 Cmnd_Alias SU = /usr/bin/su
1060 Here we override some of the compiled in default values. We want
1061 B<sudo> to log via L<syslog(3)> using the I<auth> facility in all
1062 cases. We don't want to subject the full time staff to the B<sudo>
1063 lecture, user B<millert> need not give a password, and we don't
1064 want to reset the C<LOGNAME> or C<USER> environment variables when
1065 running commands as root. Additionally, on the machines in the
1066 I<SERVERS> C<Host_Alias>, we keep an additional local log file and
1067 make sure we log the year in each log line since the log entries
1068 will be kept around for several years.
1070 # Override built-in defaults
1071 Defaults syslog=auth
1072 Defaults>root !set_logname
1073 Defaults:FULLTIMERS !lecture
1074 Defaults:millert !authenticate
1075 Defaults@SERVERS log_year, logfile=/var/log/sudo.log
1077 The I<User specification> is the part that actually determines who may
1080 root ALL = (ALL) ALL
1081 %wheel ALL = (ALL) ALL
1083 We let B<root> and any user in group B<wheel> run any command on any
1086 FULLTIMERS ALL = NOPASSWD: ALL
1088 Full time sysadmins (B<millert>, B<mikef>, and B<dowdy>) may run any
1089 command on any host without authenticating themselves.
1091 PARTTIMERS ALL = ALL
1093 Part time sysadmins (B<bostley>, B<jwfox>, and B<crawl>) may run any
1094 command on any host but they must authenticate themselves first
1095 (since the entry lacks the C<NOPASSWD> tag).
1099 The user B<jack> may run any command on the machines in the I<CSNETS> alias
1100 (the networks C<128.138.243.0>, C<128.138.204.0>, and C<128.138.242.0>).
1101 Of those networks, only C<128.138.204.0> has an explicit netmask (in
1102 CIDR notation) indicating it is a class C network. For the other
1103 networks in I<CSNETS>, the local machine's netmask will be used
1108 The user B<lisa> may run any command on any host in the I<CUNETS> alias
1109 (the class B network C<128.138.0.0>).
1111 operator ALL = DUMPS, KILL, SHUTDOWN, HALT, REBOOT, PRINTING,\
1112 sudoedit /etc/printcap, /usr/oper/bin/
1114 The B<operator> user may run commands limited to simple maintenance.
1115 Here, those are commands related to backups, killing processes, the
1116 printing system, shutting down the system, and any commands in the
1117 directory F</usr/oper/bin/>.
1119 joe ALL = /usr/bin/su operator
1121 The user B<joe> may only L<su(1)> to operator.
1123 pete HPPA = /usr/bin/passwd [A-z]*, !/usr/bin/passwd root
1125 The user B<pete> is allowed to change anyone's password except for
1126 root on the I<HPPA> machines. Note that this assumes L<passwd(1)>
1127 does not take multiple usernames on the command line.
1129 bob SPARC = (OP) ALL : SGI = (OP) ALL
1131 The user B<bob> may run anything on the I<SPARC> and I<SGI> machines
1132 as any user listed in the I<OP> C<Runas_Alias> (B<root> and B<operator>).
1136 The user B<jim> may run any command on machines in the I<biglab> netgroup.
1137 B<Sudo> knows that "biglab" is a netgroup due to the '+' prefix.
1139 +secretaries ALL = PRINTING, /usr/bin/adduser, /usr/bin/rmuser
1141 Users in the B<secretaries> netgroup need to help manage the printers
1142 as well as add and remove users, so they are allowed to run those
1143 commands on all machines.
1145 fred ALL = (DB) NOPASSWD: ALL
1147 The user B<fred> can run commands as any user in the I<DB> C<Runas_Alias>
1148 (B<oracle> or B<sybase>) without giving a password.
1150 john ALPHA = /usr/bin/su [!-]*, !/usr/bin/su *root*
1152 On the I<ALPHA> machines, user B<john> may su to anyone except root
1153 but he is not allowed to give L<su(1)> any flags.
1155 jen ALL, !SERVERS = ALL
1157 The user B<jen> may run any command on any machine except for those
1158 in the I<SERVERS> C<Host_Alias> (master, mail, www and ns).
1160 jill SERVERS = /usr/bin/, !SU, !SHELLS
1162 For any machine in the I<SERVERS> C<Host_Alias>, B<jill> may run
1163 any commands in the directory /usr/bin/ except for those commands
1164 belonging to the I<SU> and I<SHELLS> C<Cmnd_Aliases>.
1166 steve CSNETS = (operator) /usr/local/op_commands/
1168 The user B<steve> may run any command in the directory /usr/local/op_commands/
1169 but only as user operator.
1171 matt valkyrie = KILL
1173 On his personal workstation, valkyrie, B<matt> needs to be able to
1174 kill hung processes.
1176 WEBMASTERS www = (www) ALL, (root) /usr/bin/su www
1178 On the host www, any user in the I<WEBMASTERS> C<User_Alias> (will,
1179 wendy, and wim), may run any command as user www (which owns the
1180 web pages) or simply L<su(1)> to www.
1182 ALL CDROM = NOPASSWD: /sbin/umount /CDROM,\
1183 /sbin/mount -o nosuid\,nodev /dev/cd0a /CDROM
1185 Any user may mount or unmount a CD-ROM on the machines in the CDROM
1186 C<Host_Alias> (orion, perseus, hercules) without entering a password.
1187 This is a bit tedious for users to type, so it is a prime candidate
1188 for encapsulating in a shell script.
1190 =head1 SECURITY NOTES
1192 It is generally not effective to "subtract" commands from C<ALL>
1193 using the '!' operator. A user can trivially circumvent this
1194 by copying the desired command to a different name and then
1195 executing that. For example:
1197 bill ALL = ALL, !SU, !SHELLS
1199 Doesn't really prevent B<bill> from running the commands listed in
1200 I<SU> or I<SHELLS> since he can simply copy those commands to a
1201 different name, or use a shell escape from an editor or other
1202 program. Therefore, these kind of restrictions should be considered
1203 advisory at best (and reinforced by policy).
1205 =head1 PREVENTING SHELL ESCAPES
1207 Once B<sudo> executes a program, that program is free to do whatever
1208 it pleases, including run other programs. This can be a security
1209 issue since it is not uncommon for a program to allow shell escapes,
1210 which lets a user bypass B<sudo>'s restrictions. Common programs
1211 that permit shell escapes include shells (obviously), editors,
1212 paginators, mail and terminal programs.
1214 Many systems that support shared libraries have the ability to
1215 override default library functions by pointing an environment
1216 variable (usually C<LD_PRELOAD>) to an alternate shared library.
1217 On such systems, B<sudo>'s I<noexec> functionality can be used to
1218 prevent a program run by sudo from executing any other programs.
1219 Note, however, that this applies only to native dynamically-linked
1220 executables. Statically-linked executables and foreign executables
1221 running under binary emulation are not affected.
1223 To tell whether or not B<sudo> supports I<noexec>, you can run
1224 the following as root:
1226 sudo -V | grep "dummy exec"
1228 If the resulting output contains a line that begins with:
1230 File containing dummy exec functions:
1232 then B<sudo> may be able to replace the exec family of functions
1233 in the standard library with its own that simply return an error.
1234 Unfortunately, there is no foolproof way to know whether or not
1235 I<noexec> will work at compile-time. I<Noexec> should work on
1236 SunOS, Solaris, *BSD, Linux, IRIX, Tru64 UNIX, MacOS X, and HP-UX
1237 11.x. It is known B<not> to work on AIX and UnixWare. I<Noexec>
1238 is expected to work on most operating systems that support the
1239 C<LD_PRELOAD> environment variable. Check your operating system's
1240 manual pages for the dynamic linker (usually ld.so, ld.so.1, dyld,
1241 dld.sl, rld, or loader) to see if C<LD_PRELOAD> is supported.
1243 To enable I<noexec> for a command, use the C<NOEXEC> tag as documented
1244 in the User Specification section above. Here is that example again:
1246 aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
1248 This allows user B<aaron> to run F</usr/bin/more> and F</usr/bin/vi>
1249 with I<noexec> enabled. This will prevent those two commands from
1250 executing other commands (such as a shell). If you are unsure
1251 whether or not your system is capable of supporting I<noexec> you
1252 can always just try it out and see if it works.
1254 Note that disabling shell escapes is not a panacea. Programs running
1255 as root are still capable of many potentially hazardous operations
1256 (such as changing or overwriting files) that could lead to unintended
1257 privilege escalation. In the specific case of an editor, a safer
1258 approach is to give the user permission to run B<sudoedit>.
1262 L<rsh(1)>, L<su(1)>, L<fnmatch(3)>, L<sudo(@mansectsu@)>, L<visudo(@mansectsu@)>
1266 The I<sudoers> file should B<always> be edited by the B<visudo>
1267 command which locks the file and does grammatical checking. It is
1268 imperative that I<sudoers> be free of syntax errors since B<sudo>
1269 will not run with a syntactically incorrect I<sudoers> file.
1271 When using netgroups of machines (as opposed to users), if you
1272 store fully qualified hostnames in the netgroup (as is usually the
1273 case), you either need to have the machine's hostname be fully qualified
1274 as returned by the C<hostname> command or use the I<fqdn> option in
1279 If you feel you have found a bug in B<sudo>, please submit a bug report
1280 at http://www.sudo.ws/sudo/bugs/
1284 Commercial support is available for B<sudo>, see
1285 http://www.sudo.ws/sudo/support.html for details.
1287 Limited free support is available via the sudo-users mailing list,
1288 see http://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or
1289 search the archives.
1293 B<Sudo> is provided ``AS IS'' and any express or implied warranties,
1294 including, but not limited to, the implied warranties of merchantability
1295 and fitness for a particular purpose are disclaimed. See the LICENSE
1296 file distributed with B<sudo> or http://www.sudo.ws/sudo/license.html
1297 for complete details.