1 Copyright (c) 1994-1996, 1998-2005, 2007
2 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 1.95.2.26 2008/02/19 18:13:17 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 multiple matches, the last match is used (which is
36 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][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.E<nbsp>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 along with the network number,
156 B<sudo> will query each of the local host's network interfaces and,
157 if the network number corresponds to one of the hosts's network
158 interfaces, the corresponding netmask will be used. The netmask
159 may be specified either in standard IP address notation
160 (e.g.E<nbsp>255.255.255.0 or ffff:ffff:ffff:ffff::),
161 or CIDR notation (number of bits, e.g.E<nbsp>24 or 64). A hostname may
162 include shell-style wildcards (see the L<Wildcards> section below),
163 but unless the C<hostname> command on your machine returns the fully
164 qualified hostname, you'll need to use the I<fqdn> option for
165 wildcards to be useful.
170 commandname ::= filename |
174 Cmnd ::= '!'* commandname |
179 A C<Cmnd_List> is a list of one or more commandnames, directories, and other
180 aliases. A commandname is a fully qualified filename which may include
181 shell-style wildcards (see the L<Wildcards> section below). A simple
182 filename allows the user to run the command with any arguments he/she
183 wishes. However, you may also specify command line arguments (including
184 wildcards). Alternately, you can specify C<""> to indicate that the command
185 may only be run B<without> command line arguments. A directory is a
186 fully qualified pathname ending in a '/'. When you specify a directory
187 in a C<Cmnd_List>, the user will be able to run any file within that directory
188 (but not in any subdirectories therein).
190 If a C<Cmnd> has associated command line arguments, then the arguments
191 in the C<Cmnd> must match exactly those given by the user on the command line
192 (or match the wildcards if there are any). Note that the following
193 characters must be escaped with a '\' if they are used in command
194 arguments: ',', ':', '=', '\'. The special command C<"sudoedit">
195 is used to permit a user to run B<sudo> with the B<-e> flag (or
196 as B<sudoedit>). It may take command line arguments just as
197 a normal command does.
201 Certain configuration options may be changed from their default
202 values at runtime via one or more C<Default_Entry> lines. These
203 may affect all users on any host, all users on a specific host, a
204 specific user, or commands being run as a specific user.
206 Default_Type ::= 'Defaults' |
207 'Defaults' '@' Host_List |
208 'Defaults' ':' User_List |
209 'Defaults' '>' Runas_List
211 Default_Entry ::= Default_Type Parameter_List
213 Parameter_List ::= Parameter |
214 Parameter ',' Parameter_List
216 Parameter ::= Parameter '=' Value |
217 Parameter '+=' Value |
218 Parameter '-=' Value |
221 Parameters may be B<flags>, B<integer> values, B<strings>, or B<lists>.
222 Flags are implicitly boolean and can be turned off via the '!'
223 operator. Some integer, string and list parameters may also be
224 used in a boolean context to disable them. Values may be enclosed
225 in double quotes (C<">) when they contain multiple words. Special
226 characters may be escaped with a backslash (C<\>).
228 Lists have two additional assignment operators, C<+=> and C<-=>.
229 These operators are used to add to and delete from a list respectively.
230 It is not an error to use the C<-=> operator to remove an element
231 that does not exist in a list.
233 See L</"SUDOERS OPTIONS"> for a list of supported Defaults parameters.
235 =head2 User Specification
237 User_Spec ::= User_List Host_List '=' Cmnd_Spec_List \
238 (':' Host_List '=' Cmnd_Spec_List)*
240 Cmnd_Spec_List ::= Cmnd_Spec |
241 Cmnd_Spec ',' Cmnd_Spec_List
243 Cmnd_Spec ::= Runas_Spec? Tag_Spec* Cmnd
245 Runas_Spec ::= '(' Runas_List ')'
247 Tag_Spec ::= ('NOPASSWD:' | 'PASSWD:' | 'NOEXEC:' | 'EXEC:' |
248 'SETENV:' | 'NOSETENV:')
250 A B<user specification> determines which commands a user may run
251 (and as what user) on specified hosts. By default, commands are
252 run as B<root>, but this can be changed on a per-command basis.
254 Let's break that down into its constituent parts:
258 A C<Runas_Spec> is simply a C<Runas_List> (as defined above)
259 enclosed in a set of parentheses. If you do not specify a
260 C<Runas_Spec> in the user specification, a default C<Runas_Spec>
261 of B<root> will be used. A C<Runas_Spec> sets the default for
262 commands that follow it. What this means is that for the entry:
264 dgb boulder = (operator) /bin/ls, /bin/kill, /usr/bin/lprm
266 The user B<dgb> may run F</bin/ls>, F</bin/kill>, and
267 F</usr/bin/lprm> -- but only as B<operator>. E.g.,
269 $ sudo -u operator /bin/ls.
271 It is also possible to override a C<Runas_Spec> later on in an
272 entry. If we modify the entry like so:
274 dgb boulder = (operator) /bin/ls, (root) /bin/kill, /usr/bin/lprm
276 Then user B<dgb> is now allowed to run F</bin/ls> as B<operator>,
277 but F</bin/kill> and F</usr/bin/lprm> as B<root>.
281 A command may have zero or more tags associated with it. There are
282 six possible tag values, C<NOPASSWD>, C<PASSWD>, C<NOEXEC>, C<EXEC>,
283 C<SETENV> and C<NOSETENV>.
284 Once a tag is set on a C<Cmnd>, subsequent C<Cmnd>s in the
285 C<Cmnd_Spec_List>, inherit the tag unless it is overridden by the
286 opposite tag (i.e.: C<PASSWD> overrides C<NOPASSWD> and C<NOEXEC>
289 =head3 NOPASSWD and PASSWD
291 By default, B<sudo> requires that a user authenticate him or herself
292 before running a command. This behavior can be modified via the
293 C<NOPASSWD> tag. Like a C<Runas_Spec>, the C<NOPASSWD> tag sets
294 a default for the commands that follow it in the C<Cmnd_Spec_List>.
295 Conversely, the C<PASSWD> tag can be used to reverse things.
298 ray rushmore = NOPASSWD: /bin/kill, /bin/ls, /usr/bin/lprm
300 would allow the user B<ray> to run F</bin/kill>, F</bin/ls>, and
301 F</usr/bin/lprm> as root on the machine rushmore as B<root> without
302 authenticating himself. If we only want B<ray> to be able to
303 run F</bin/kill> without a password the entry would be:
305 ray rushmore = NOPASSWD: /bin/kill, PASSWD: /bin/ls, /usr/bin/lprm
307 Note, however, that the C<PASSWD> tag has no effect on users who are
308 in the group specified by the I<exempt_group> option.
310 By default, if the C<NOPASSWD> tag is applied to any of the entries
311 for a user on the current host, he or she will be able to run
312 C<sudo -l> without a password. Additionally, a user may only run
313 C<sudo -v> without a password if the C<NOPASSWD> tag is present
314 for all a user's entries that pertain to the current host.
315 This behavior may be overridden via the verifypw and listpw options.
317 =head3 NOEXEC and EXEC
319 If B<sudo> has been compiled with I<noexec> support and the underlying
320 operating system supports it, the C<NOEXEC> tag can be used to prevent
321 a dynamically-linked executable from running further commands itself.
323 In the following example, user B<aaron> may run F</usr/bin/more>
324 and F</usr/bin/vi> but shell escapes will be disabled.
326 aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
328 See the L<PREVENTING SHELL ESCAPES> section below for more details
329 on how C<NOEXEC> works and whether or not it will work on your system.
331 =head3 SETENV and NOSETENV
333 These tags override the value of the I<setenv> option on a per-command
334 basis. Note that if C<SETENV> has been set for a command, any
335 environment variables set on the command line way are not subject
336 to the restrictions imposed by I<env_check>, I<env_delete>, or
337 I<env_keep>. As such, only trusted users should be allowed to set
338 variables in this manner. If the command matched is B<ALL>, the
339 C<SETENV> tag is implied for that command; this default may
340 be overridden by use of the C<UNSETENV> tag.
344 B<sudo> allows shell-style I<wildcards> (aka meta or glob characters)
345 to be used in pathnames as well as command line arguments in the
346 I<sudoers> file. Wildcard matching is done via the B<POSIX>
347 L<fnmatch(3)> routine. Note that these are I<not> regular expressions.
353 Matches any set of zero or more characters.
357 Matches any single character.
361 Matches any character in the specified range.
365 Matches any character B<not> in the specified range.
369 For any character "x", evaluates to "x". This is used to
370 escape special characters such as: "*", "?", "[", and "}".
374 Note that a forward slash ('/') will B<not> be matched by
375 wildcards used in the pathname. When matching the command
376 line arguments, however, a slash B<does> get matched by
377 wildcards. This is to make a path like:
381 match F</usr/bin/who> but not F</usr/bin/X11/xterm>.
383 =head2 Exceptions to wildcard rules
385 The following exceptions apply to the above rules:
391 If the empty string C<""> is the only command line argument in the
392 I<sudoers> entry it means that command is not allowed to be run
393 with B<any> arguments.
397 =head2 Other special characters and reserved words
399 The pound sign ('#') is used to indicate a comment (unless it is
400 part of a #include directive or unless it occurs in the context of
401 a user name and is followed by one or more digits, in which case
402 it is treated as a uid). Both the comment character and any text
403 after it, up to the end of the line, are ignored.
405 The reserved word B<ALL> is a built-in I<alias> that always causes
406 a match to succeed. It can be used wherever one might otherwise
407 use a C<Cmnd_Alias>, C<User_Alias>, C<Runas_Alias>, or C<Host_Alias>.
408 You should not try to define your own I<alias> called B<ALL> as the
409 built-in alias will be used in preference to your own. Please note
410 that using B<ALL> can be dangerous since in a command context, it
411 allows the user to run B<any> command on the system.
413 An exclamation point ('!') can be used as a logical I<not> operator
414 both in an I<alias> and in front of a C<Cmnd>. This allows one to
415 exclude certain values. Note, however, that using a C<!> in
416 conjunction with the built-in C<ALL> alias to allow a user to
417 run "all but a few" commands rarely works as intended (see SECURITY
420 Long lines can be continued with a backslash ('\') as the last
421 character on the line.
423 Whitespace between elements in a list as well as special syntactic
424 characters in a I<User Specification> ('=', ':', '(', ')') is optional.
426 The following characters must be escaped with a backslash ('\') when
427 used as part of a word (e.g.E<nbsp>a username or hostname):
428 '@', '!', '=', ':', ',', '(', ')', '\'.
430 =head1 SUDOERS OPTIONS
432 B<sudo>'s behavior can be modified by C<Default_Entry> lines, as
433 explained earlier. A list of all supported Defaults parameters,
434 grouped by type, are listed below.
440 =item always_set_home
442 If set, B<sudo> will set the C<HOME> environment variable to the home
443 directory of the target user (which is root unless the B<-u> option is used).
444 This effectively means that the B<-H> flag is always implied.
445 This flag is I<off> by default.
449 If set, users must authenticate themselves via a password (or other
450 means of authentication) before they may run commands. This default
451 may be overridden via the C<PASSWD> and C<NOPASSWD> tags.
452 This flag is I<on> by default.
456 If set, B<visudo> will use the value of the EDITOR or VISUAL
457 environment variables before falling back on the default editor list.
458 Note that this may create a security hole as it allows the user to
459 run any arbitrary command as root without logging. A safer alternative
460 is to place a colon-separated list of editors in the C<editor>
461 variable. B<visudo> will then only use the EDITOR or VISUAL if
462 they match a value specified in C<editor>. This flag is I<@env_editor@> by
467 If set, B<sudo> will reset the environment to only contain the
468 LOGNAME, SHELL, USER, USERNAME and the C<SUDO_*> variables. Any
469 variables in the caller's environment that match the C<env_keep>
470 and C<env_check> lists are then added. The default contents of the
471 C<env_keep> and C<env_check> lists are displayed when B<sudo> is
472 run by root with the I<-V> option. If B<sudo> was compiled with
473 the C<SECURE_PATH> option, its value will be used for the C<PATH>
474 environment variable. This flag is I<on> by default.
478 Set this flag if you want to put fully qualified hostnames in the
479 I<sudoers> file. I.e., instead of myhost you would use myhost.mydomain.edu.
480 You may still use the short form if you wish (and even mix the two).
481 Beware that turning on I<fqdn> requires B<sudo> to make DNS lookups
482 which may make B<sudo> unusable if DNS stops working (for example
483 if the machine is not plugged into the network). Also note that
484 you must use the host's official name as DNS knows it. That is,
485 you may not use a host alias (C<CNAME> entry) due to performance
486 issues and the fact that there is no way to get all aliases from
487 DNS. If your machine's hostname (as returned by the C<hostname>
488 command) is already fully qualified you shouldn't need to set
489 I<fqdn>. This flag is I<@fqdn@> by default.
493 If set, B<sudo> will ignore '.' or '' (current dir) in the C<PATH>
494 environment variable; the C<PATH> itself is not modified. This
495 flag is I<@ignore_dot@> by default. Currently, while it is possible
496 to set I<ignore_dot> in I<sudoers>, its value is not used. This option
497 should be considered read-only (it will be fixed in a future version
500 =item ignore_local_sudoers
502 If set via LDAP, parsing of F<@sysconfdir@/sudoers> will be skipped.
503 This is intended for Enterprises that wish to prevent the usage of local
504 sudoers files so that only LDAP is used. This thwarts the efforts of
505 rogue operators who would attempt to add roles to F<@sysconfdir@/sudoers>.
506 When this option is present, F<@sysconfdir@/sudoers> does not even need to
507 exist. Since this option tells B<sudo> how to behave when no specific LDAP
508 entries have been matched, this sudoOption is only meaningful for the
509 C<cn=defaults> section. This flag is I<off> by default.
513 If set, B<sudo> will insult users when they enter an incorrect
514 password. This flag is I<@insults@> by default.
518 If set, the hostname will be logged in the (non-syslog) B<sudo> log file.
519 This flag is I<off> by default.
523 If set, the four-digit year will be logged in the (non-syslog) B<sudo> log file.
524 This flag is I<off> by default.
526 =item long_otp_prompt
528 When validating with a One Time Password (OPT) scheme such as
529 B<S/Key> or B<OPIE>, a two-line prompt is used to make it easier
530 to cut and paste the challenge to a local window. It's not as
531 pretty as the default but some people find it more convenient. This
532 flag is I<@long_otp_prompt@> by default.
536 Send mail to the I<mailto> user every time a users runs B<sudo>.
537 This flag is I<off> by default.
541 Send mail to the I<mailto> user if the user running B<sudo> does not
542 enter the correct password. This flag is I<off> by default.
546 If set, mail will be sent to the I<mailto> user if the invoking
547 user exists in the I<sudoers> file, but is not allowed to run
548 commands on the current host. This flag is I<@mail_no_host@> by default.
552 If set, mail will be sent to the I<mailto> user if the invoking
553 user is allowed to use B<sudo> but the command they are trying is not
554 listed in their I<sudoers> file entry or is explicitly denied.
555 This flag is I<@mail_no_perms@> by default.
559 If set, mail will be sent to the I<mailto> user if the invoking
560 user is not in the I<sudoers> file. This flag is I<@mail_no_user@>
565 If set, all commands run via B<sudo> will behave as if the C<NOEXEC>
566 tag has been set, unless overridden by a C<EXEC> tag. See the
567 description of I<NOEXEC and EXEC> below as well as the L<PREVENTING SHELL
568 ESCAPES> section at the end of this manual. This flag is I<off> by default.
572 Normally, B<sudo> will tell the user when a command could not be
573 found in their C<PATH> environment variable. Some sites may wish
574 to disable this as it could be used to gather information on the
575 location of executables that the normal user does not have access
576 to. The disadvantage is that if the executable is simply not in
577 the user's C<PATH>, B<sudo> will tell the user that they are not
578 allowed to run it, which can be confusing. This flag is I<@path_info@>
581 =item passprompt_override
583 The password prompt specified by I<passprompt> will normally only
584 be used if the passwod prompt provided by systems such as PAM matches
585 the string "Password:". If I<passprompt_override> is set, I<passprompt>
586 will always be used. This flag is I<off> by default.
588 =item preserve_groups
590 By default B<sudo> will initialize the group vector to the list of
591 groups the target user is in. When I<preserve_groups> is set, the
592 user's existing group vector is left unaltered. The real and
593 effective group IDs, however, are still set to match the target
594 user. This flag is I<off> by default.
598 If set, B<sudo> will only run when the user is logged in to a real
599 tty. This will disallow things like C<"rsh somehost sudo ls"> since
600 L<rsh(1)> does not allocate a tty. Because it is not possible to turn
601 off echo when there is no tty present, some sites may wish to set
602 this flag to prevent a user from entering a visible password. This
603 flag is I<off> by default.
607 If set, root is allowed to run B<sudo> too. Disabling this prevents users
608 from "chaining" B<sudo> commands to get a root shell by doing something
609 like C<"sudo sudo /bin/sh">. Note, however, that turning off I<root_sudo>
610 will also prevent root and from running B<sudoedit>.
611 Disabling I<root_sudo> provides no real additional security; it
612 exists purely for historical reasons.
613 This flag is I<@root_sudo@> by default.
617 If set, B<sudo> will prompt for the root password instead of the password
618 of the invoking user. This flag is I<off> by default.
622 If set, B<sudo> will prompt for the password of the user defined by the
623 I<runas_default> option (defaults to C<@runas_default@>) instead of the
624 password of the invoking user. This flag is I<off> by default.
628 If set and B<sudo> is invoked with the B<-s> flag the C<HOME>
629 environment variable will be set to the home directory of the target
630 user (which is root unless the B<-u> option is used). This effectively
631 makes the B<-s> flag imply B<-H>. This flag is I<off> by default.
635 Normally, B<sudo> will set the C<LOGNAME>, C<USER> and C<USERNAME>
636 environment variables to the name of the target user (usually root
637 unless the B<-u> flag is given). However, since some programs
638 (including the RCS revision control system) use C<LOGNAME> to
639 determine the real identity of the user, it may be desirable to
640 change this behavior. This can be done by negating the set_logname
641 option. Note that if the I<env_reset> option has not been disabled,
642 entries in the I<env_keep> list will override the value of
643 I<set_logname>. This flag is I<off> by default.
647 Allow the user to disable the I<env_reset> option from the command
648 line. Additionally, environment variables set via the command line
649 are not subject to the restrictions imposed by I<env_check>,
650 I<env_delete>, or I<env_keep>. As such, only trusted users should
651 be allowed to set variables in this manner. This flag is I<off>
656 If set and B<sudo> is invoked with no arguments it acts as if the
657 B<-s> flag had been given. That is, it runs a shell as root (the
658 shell is determined by the C<SHELL> environment variable if it is
659 set, falling back on the shell listed in the invoking user's
660 /etc/passwd entry if not). This flag is I<off> by default.
664 Normally, when B<sudo> executes a command the real and effective
665 UIDs are set to the target user (root by default). This option
666 changes that behavior such that the real UID is left as the invoking
667 user's UID. In other words, this makes B<sudo> act as a setuid
668 wrapper. This can be useful on systems that disable some potentially
669 dangerous functionality when a program is run setuid. This option
670 is only effective on systems with either the setreuid() or setresuid()
671 function. This flag is I<off> by default.
675 If set, B<sudo> will prompt for the password of the user specified by
676 the B<-u> flag (defaults to C<root>) instead of the password of the
677 invoking user. Note that this precludes the use of a uid not listed
678 in the passwd database as an argument to the B<-u> flag.
679 This flag is I<off> by default.
683 If set, users must authenticate on a per-tty basis. Normally,
684 B<sudo> uses a directory in the ticket dir with the same name as
685 the user running it. With this flag enabled, B<sudo> will use a
686 file named for the tty the user is logged in on in that directory.
687 This flag is I<@tty_tickets@> by default.
691 If set, B<sudo> will apply the defaults specified for the target user's
692 login class if one exists. Only available if B<sudo> is configured with
693 the --with-logincap option. This flag is I<off> by default.
703 The number of tries a user gets to enter his/her password before
704 B<sudo> logs the failure and exits. The default is C<@passwd_tries@>.
708 B<Integers that can be used in a boolean context>:
714 Number of characters per line for the file log. This value is used
715 to decide when to wrap lines for nicer log files. This has no
716 effect on the syslog log file, only the file log. The default is
717 C<@loglen@> (use 0 or negate the option to disable word wrap).
721 Number of minutes before the B<sudo> password prompt times out.
722 The default is C<@password_timeout@>; set this to C<0> for no password timeout.
724 =item timestamp_timeout
726 Number of minutes that can elapse before B<sudo> will ask for a
727 passwd again. The default is C<@timeout@>. Set this to C<0> to always
728 prompt for a password.
729 If set to a value less than C<0> the user's timestamp will never
730 expire. This can be used to allow users to create or delete their
731 own timestamps via C<sudo -v> and C<sudo -k> respectively.
735 Umask to use when running the command. Negate this option or set
736 it to 0777 to preserve the user's umask. The default is C<@sudo_umask@>.
744 =item badpass_message
746 Message that is displayed if a user enters an incorrect password.
747 The default is C<@badpass_message@> unless insults are enabled.
751 A colon (':') separated list of editors allowed to be used with
752 B<visudo>. B<visudo> will choose the editor that matches the user's
753 EDITOR environment variable if possible, or the first editor in the
754 list that exists and is executable. The default is the path to vi
759 Subject of the mail sent to the I<mailto> user. The escape C<%h>
760 will expand to the hostname of the machine.
761 Default is C<@mailsub@>.
765 Path to a shared library containing dummy versions of the execv(),
766 execve() and fexecve() library functions that just return an error.
767 This is used to implement the I<noexec> functionality on systems that
768 support C<LD_PRELOAD> or its equivalent. Defaults to F<@noexec_file@>.
772 The default prompt to use when asking for a password; can be overridden
773 via the B<-p> option or the C<SUDO_PROMPT> environment variable.
774 The following percent (`C<%>') escapes are supported:
780 expanded to the local hostname including the domain name
781 (on if the machine's hostname is fully qualified or the I<fqdn>
786 expanded to the local hostname without the domain name
790 expanded to the user whose password is being asked for (respects the
791 I<rootpw>, I<targetpw> and I<runaspw> flags in I<sudoers>)
795 expanded to the login name of the user the command will
796 be run as (defaults to root)
800 expanded to the invoking user's login name
804 two consecutive C<%> characters are collapsed into a single C<%> character
808 The default value is C<@passprompt@>.
812 The default SELinux role to use when constructing a new security
813 context to run the command. The default role may be overridden on
814 a per-command basis in I<sudoers> or via command line options.
815 This option is only available whe B<sudo> is built with SELinux support.
819 The default user to run commands as if the B<-u> flag is not specified
820 on the command line. This defaults to C<@runas_default@>.
821 Note that if I<runas_default> is set it B<must> occur before
822 any C<Runas_Alias> specifications.
826 Syslog priority to use when user authenticates unsuccessfully.
827 Defaults to C<@badpri@>.
831 Syslog priority to use when user authenticates successfully.
832 Defaults to C<@goodpri@>.
836 The directory in which B<sudo> stores its timestamp files.
837 The default is F<@timedir@>.
841 The owner of the timestamp directory and the timestamps stored therein.
842 The default is C<root>.
846 The default SELinux type to use when constructing a new security
847 context to run the command. The default type may be overridden on
848 a per-command basis in I<sudoers> or via command line options.
849 This option is only available whe B<sudo> is built with SELinux support.
853 B<Strings that can be used in a boolean context>:
859 Users in this group are exempt from password and PATH requirements.
860 This is not set by default.
864 This option controls when a short lecture will be printed along with
865 the password prompt. It has the following possible values:
871 Always lecture the user.
875 Never lecture the user.
879 Only lecture the user the first time they run B<sudo>.
883 If no value is specified, a value of I<once> is implied.
884 Negating the option results in a value of I<never> being used.
885 The default value is I<@lecture@>.
889 Path to a file containing an alternate B<sudo> lecture that will
890 be used in place of the standard lecture if the named file exists.
891 By default, B<sudo> uses a built-in lecture.
895 This option controls when a password will be required when a
896 user runs B<sudo> with the B<-l> flag. It has the following possible values:
902 All the user's I<sudoers> entries for the current host must have
903 the C<NOPASSWD> flag set to avoid entering a password.
907 The user must always enter a password to use the B<-l> flag.
911 At least one of the user's I<sudoers> entries for the current host
912 must have the C<NOPASSWD> flag set to avoid entering a password.
916 The user need never enter a password to use the B<-l> flag.
920 If no value is specified, a value of I<any> is implied.
921 Negating the option results in a value of I<never> being used.
922 The default value is I<any>.
926 Path to the B<sudo> log file (not the syslog log file). Setting a path
927 turns on logging to a file; negating this option turns it off.
928 By default, B<sudo> logs via syslog.
932 Flags to use when invoking mailer. Defaults to B<-t>.
936 Path to mail program used to send warning mail.
937 Defaults to the path to sendmail found at configure time.
941 Address to send warning and error mail to. The address should
942 be enclosed in double quotes (C<">) to protect against B<sudo>
943 interpreting the C<@> sign. Defaults to C<@mailto@>.
947 Syslog facility if syslog is being used for logging (negate to
948 disable syslog logging). Defaults to C<@logfac@>.
952 This option controls when a password will be required when a user runs
953 B<sudo> with the B<-v> flag. It has the following possible values:
959 All the user's I<sudoers> entries for the current host must have
960 the C<NOPASSWD> flag set to avoid entering a password.
964 The user must always enter a password to use the B<-v> flag.
968 At least one of the user's I<sudoers> entries for the current host
969 must have the C<NOPASSWD> flag set to avoid entering a password.
973 The user need never enter a password to use the B<-v> flag.
977 If no value is specified, a value of I<all> is implied.
978 Negating the option results in a value of I<never> being used.
979 The default value is I<all>.
983 B<Lists that can be used in a boolean context>:
989 Environment variables to be removed from the user's environment if
990 the variable's value contains C<%> or C</> characters. This can
991 be used to guard against printf-style format vulnerabilities in
992 poorly-written programs. The argument may be a double-quoted,
993 space-separated list or a single value without double-quotes. The
994 list can be replaced, added to, deleted from, or disabled by using
995 the C<=>, C<+=>, C<-=>, and C<!> operators respectively. Regardless
996 of whether the C<env_reset> option is enabled or disabled, variables
997 specified by C<env_check> will be preserved in the environment if
998 they pass the aforementioned check. The default list of environment
999 variables to check is displayed when B<sudo> is run by root with
1004 Environment variables to be removed from the user's environment.
1005 The argument may be a double-quoted, space-separated list or a
1006 single value without double-quotes. The list can be replaced, added
1007 to, deleted from, or disabled by using the C<=>, C<+=>, C<-=>, and
1008 C<!> operators respectively. The default list of environment
1009 variables to remove is displayed when B<sudo> is run by root with the
1010 I<-V> option. Note that many operating systems will remove potentially
1011 dangerous variables from the environment of any setuid process (such
1016 Environment variables to be preserved in the user's environment
1017 when the I<env_reset> option is in effect. This allows fine-grained
1018 control over the environment B<sudo>-spawned processes will receive.
1019 The argument may be a double-quoted, space-separated list or a
1020 single value without double-quotes. The list can be replaced, added
1021 to, deleted from, or disabled by using the C<=>, C<+=>, C<-=>, and
1022 C<!> operators respectively. The default list of variables to keep
1023 is displayed when B<sudo> is run by root with the I<-V> option.
1027 When logging via L<syslog(3)>, B<sudo> accepts the following values
1028 for the syslog facility (the value of the B<syslog> Parameter):
1029 B<authpriv> (if your OS supports it), B<auth>, B<daemon>, B<user>,
1030 B<local0>, B<local1>, B<local2>, B<local3>, B<local4>, B<local5>,
1031 B<local6>, and B<local7>. The following syslog priorities are
1032 supported: B<alert>, B<crit>, B<debug>, B<emerg>, B<err>, B<info>,
1033 B<notice>, and B<warning>.
1039 =item F<@sysconfdir@/sudoers>
1041 List of who can run what
1047 =item F</etc/netgroup>
1049 List of network groups
1055 Since the I<sudoers> file is parsed in a single pass, order is
1056 important. In general, you should structure I<sudoers> such that
1057 the C<Host_Alias>, C<User_Alias>, and C<Cmnd_Alias> specifications
1058 come first, followed by any C<Default_Entry> lines, and finally the
1059 C<Runas_Alias> and user specifications. The basic rule of thumb
1060 is you cannot reference an Alias that has not already been defined.
1062 Below are example I<sudoers> entries. Admittedly, some of
1063 these are a bit contrived. First, we define our I<aliases>:
1065 # User alias specification
1066 User_Alias FULLTIMERS = millert, mikef, dowdy
1067 User_Alias PARTTIMERS = bostley, jwfox, crawl
1068 User_Alias WEBMASTERS = will, wendy, wim
1070 # Runas alias specification
1071 Runas_Alias OP = root, operator
1072 Runas_Alias DB = oracle, sybase
1074 # Host alias specification
1075 Host_Alias SPARC = bigtime, eclipse, moet, anchor :\
1076 SGI = grolsch, dandelion, black :\
1077 ALPHA = widget, thalamus, foobar :\
1078 HPPA = boa, nag, python
1079 Host_Alias CUNETS = 128.138.0.0/255.255.0.0
1080 Host_Alias CSNETS = 128.138.243.0, 128.138.204.0/24, 128.138.242.0
1081 Host_Alias SERVERS = master, mail, www, ns
1082 Host_Alias CDROM = orion, perseus, hercules
1084 # Cmnd alias specification
1085 Cmnd_Alias DUMPS = /usr/bin/mt, /usr/sbin/dump, /usr/sbin/rdump,\
1086 /usr/sbin/restore, /usr/sbin/rrestore
1087 Cmnd_Alias KILL = /usr/bin/kill
1088 Cmnd_Alias PRINTING = /usr/sbin/lpc, /usr/bin/lprm
1089 Cmnd_Alias SHUTDOWN = /usr/sbin/shutdown
1090 Cmnd_Alias HALT = /usr/sbin/halt
1091 Cmnd_Alias REBOOT = /usr/sbin/reboot
1092 Cmnd_Alias SHELLS = /usr/bin/sh, /usr/bin/csh, /usr/bin/ksh, \
1093 /usr/local/bin/tcsh, /usr/bin/rsh, \
1095 Cmnd_Alias SU = /usr/bin/su
1096 Cmnd_Alias PAGERS = /usr/bin/more, /usr/bin/pg, /usr/bin/less
1098 Here we override some of the compiled in default values. We want
1099 B<sudo> to log via L<syslog(3)> using the I<auth> facility in all
1100 cases. We don't want to subject the full time staff to the B<sudo>
1101 lecture, user B<millert> need not give a password, and we don't
1102 want to reset the C<LOGNAME>, C<USER> or C<USERNAME> environment
1103 variables when running commands as root. Additionally, on the
1104 machines in the I<SERVERS> C<Host_Alias>, we keep an additional
1105 local log file and make sure we log the year in each log line since
1106 the log entries will be kept around for several years. Lastly, we
1107 disable shell escapes for the commands in the PAGERS C<Cmnd_Alias>
1108 (F</usr/bin/more>, F</usr/bin/pg> and F</usr/bin/less>).
1110 # Override built-in defaults
1111 Defaults syslog=auth
1112 Defaults>root !set_logname
1113 Defaults:FULLTIMERS !lecture
1114 Defaults:millert !authenticate
1115 Defaults@SERVERS log_year, logfile=/var/log/sudo.log
1116 Defaults!PAGERS noexec
1118 The I<User specification> is the part that actually determines who may
1121 root ALL = (ALL) ALL
1122 %wheel ALL = (ALL) ALL
1124 We let B<root> and any user in group B<wheel> run any command on any
1127 FULLTIMERS ALL = NOPASSWD: ALL
1129 Full time sysadmins (B<millert>, B<mikef>, and B<dowdy>) may run any
1130 command on any host without authenticating themselves.
1132 PARTTIMERS ALL = ALL
1134 Part time sysadmins (B<bostley>, B<jwfox>, and B<crawl>) may run any
1135 command on any host but they must authenticate themselves first
1136 (since the entry lacks the C<NOPASSWD> tag).
1140 The user B<jack> may run any command on the machines in the I<CSNETS> alias
1141 (the networks C<128.138.243.0>, C<128.138.204.0>, and C<128.138.242.0>).
1142 Of those networks, only C<128.138.204.0> has an explicit netmask (in
1143 CIDR notation) indicating it is a class C network. For the other
1144 networks in I<CSNETS>, the local machine's netmask will be used
1149 The user B<lisa> may run any command on any host in the I<CUNETS> alias
1150 (the class B network C<128.138.0.0>).
1152 operator ALL = DUMPS, KILL, SHUTDOWN, HALT, REBOOT, PRINTING,\
1153 sudoedit /etc/printcap, /usr/oper/bin/
1155 The B<operator> user may run commands limited to simple maintenance.
1156 Here, those are commands related to backups, killing processes, the
1157 printing system, shutting down the system, and any commands in the
1158 directory F</usr/oper/bin/>.
1160 joe ALL = /usr/bin/su operator
1162 The user B<joe> may only L<su(1)> to operator.
1164 pete HPPA = /usr/bin/passwd [A-z]*, !/usr/bin/passwd root
1166 The user B<pete> is allowed to change anyone's password except for
1167 root on the I<HPPA> machines. Note that this assumes L<passwd(1)>
1168 does not take multiple usernames on the command line.
1170 bob SPARC = (OP) ALL : SGI = (OP) ALL
1172 The user B<bob> may run anything on the I<SPARC> and I<SGI> machines
1173 as any user listed in the I<OP> C<Runas_Alias> (B<root> and B<operator>).
1177 The user B<jim> may run any command on machines in the I<biglab> netgroup.
1178 B<sudo> knows that "biglab" is a netgroup due to the '+' prefix.
1180 +secretaries ALL = PRINTING, /usr/bin/adduser, /usr/bin/rmuser
1182 Users in the B<secretaries> netgroup need to help manage the printers
1183 as well as add and remove users, so they are allowed to run those
1184 commands on all machines.
1186 fred ALL = (DB) NOPASSWD: ALL
1188 The user B<fred> can run commands as any user in the I<DB> C<Runas_Alias>
1189 (B<oracle> or B<sybase>) without giving a password.
1191 john ALPHA = /usr/bin/su [!-]*, !/usr/bin/su *root*
1193 On the I<ALPHA> machines, user B<john> may su to anyone except root
1194 but he is not allowed to give L<su(1)> any flags.
1196 jen ALL, !SERVERS = ALL
1198 The user B<jen> may run any command on any machine except for those
1199 in the I<SERVERS> C<Host_Alias> (master, mail, www and ns).
1201 jill SERVERS = /usr/bin/, !SU, !SHELLS
1203 For any machine in the I<SERVERS> C<Host_Alias>, B<jill> may run
1204 any commands in the directory F</usr/bin/> except for those commands
1205 belonging to the I<SU> and I<SHELLS> C<Cmnd_Aliases>.
1207 steve CSNETS = (operator) /usr/local/op_commands/
1209 The user B<steve> may run any command in the directory /usr/local/op_commands/
1210 but only as user operator.
1212 matt valkyrie = KILL
1214 On his personal workstation, valkyrie, B<matt> needs to be able to
1215 kill hung processes.
1217 WEBMASTERS www = (www) ALL, (root) /usr/bin/su www
1219 On the host www, any user in the I<WEBMASTERS> C<User_Alias> (will,
1220 wendy, and wim), may run any command as user www (which owns the
1221 web pages) or simply L<su(1)> to www.
1223 ALL CDROM = NOPASSWD: /sbin/umount /CDROM,\
1224 /sbin/mount -o nosuid\,nodev /dev/cd0a /CDROM
1226 Any user may mount or unmount a CD-ROM on the machines in the CDROM
1227 C<Host_Alias> (orion, perseus, hercules) without entering a password.
1228 This is a bit tedious for users to type, so it is a prime candidate
1229 for encapsulating in a shell script.
1231 =head1 SECURITY NOTES
1233 It is generally not effective to "subtract" commands from C<ALL>
1234 using the '!' operator. A user can trivially circumvent this
1235 by copying the desired command to a different name and then
1236 executing that. For example:
1238 bill ALL = ALL, !SU, !SHELLS
1240 Doesn't really prevent B<bill> from running the commands listed in
1241 I<SU> or I<SHELLS> since he can simply copy those commands to a
1242 different name, or use a shell escape from an editor or other
1243 program. Therefore, these kind of restrictions should be considered
1244 advisory at best (and reinforced by policy).
1246 =head1 PREVENTING SHELL ESCAPES
1248 Once B<sudo> executes a program, that program is free to do whatever
1249 it pleases, including run other programs. This can be a security
1250 issue since it is not uncommon for a program to allow shell escapes,
1251 which lets a user bypass B<sudo>'s access control and logging.
1252 Common programs that permit shell escapes include shells (obviously),
1253 editors, paginators, mail and terminal programs.
1255 There are two basic approaches to this problem:
1261 Avoid giving users access to commands that allow the user to run
1262 arbitrary commands. Many editors have a restricted mode where shell
1263 escapes are disabled, though B<sudoedit> is a better solution to
1264 running editors via B<sudo>. Due to the large number of programs that
1265 offer shell escapes, restricting users to the set of programs that
1266 do not if often unworkable.
1270 Many systems that support shared libraries have the ability to
1271 override default library functions by pointing an environment
1272 variable (usually C<LD_PRELOAD>) to an alternate shared library.
1273 On such systems, B<sudo>'s I<noexec> functionality can be used to
1274 prevent a program run by B<sudo> from executing any other programs.
1275 Note, however, that this applies only to native dynamically-linked
1276 executables. Statically-linked executables and foreign executables
1277 running under binary emulation are not affected.
1279 To tell whether or not B<sudo> supports I<noexec>, you can run
1280 the following as root:
1282 sudo -V | grep "dummy exec"
1284 If the resulting output contains a line that begins with:
1286 File containing dummy exec functions:
1288 then B<sudo> may be able to replace the exec family of functions
1289 in the standard library with its own that simply return an error.
1290 Unfortunately, there is no foolproof way to know whether or not
1291 I<noexec> will work at compile-time. I<noexec> should work on
1292 SunOS, Solaris, *BSD, Linux, IRIX, Tru64 UNIX, MacOS X, and HP-UX
1293 11.x. It is known B<not> to work on AIX and UnixWare. I<noexec>
1294 is expected to work on most operating systems that support the
1295 C<LD_PRELOAD> environment variable. Check your operating system's
1296 manual pages for the dynamic linker (usually ld.so, ld.so.1, dyld,
1297 dld.sl, rld, or loader) to see if C<LD_PRELOAD> is supported.
1299 To enable I<noexec> for a command, use the C<NOEXEC> tag as documented
1300 in the User Specification section above. Here is that example again:
1302 aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
1304 This allows user B<aaron> to run F</usr/bin/more> and F</usr/bin/vi>
1305 with I<noexec> enabled. This will prevent those two commands from
1306 executing other commands (such as a shell). If you are unsure
1307 whether or not your system is capable of supporting I<noexec> you
1308 can always just try it out and see if it works.
1312 Note that restricting shell escapes is not a panacea. Programs
1313 running as root are still capable of many potentially hazardous
1314 operations (such as changing or overwriting files) that could lead
1315 to unintended privilege escalation. In the specific case of an
1316 editor, a safer approach is to give the user permission to run
1321 L<rsh(1)>, L<su(1)>, L<fnmatch(3)>, L<sudo(8)>, L<visudo(8)>
1325 The I<sudoers> file should B<always> be edited by the B<visudo>
1326 command which locks the file and does grammatical checking. It is
1327 imperative that I<sudoers> be free of syntax errors since B<sudo>
1328 will not run with a syntactically incorrect I<sudoers> file.
1330 When using netgroups of machines (as opposed to users), if you
1331 store fully qualified hostnames in the netgroup (as is usually the
1332 case), you either need to have the machine's hostname be fully qualified
1333 as returned by the C<hostname> command or use the I<fqdn> option in
1338 If you feel you have found a bug in B<sudo>, please submit a bug report
1339 at http://www.sudo.ws/sudo/bugs/
1343 Limited free support is available via the sudo-users mailing list,
1344 see http://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or
1345 search the archives.
1349 B<sudo> is provided ``AS IS'' and any express or implied warranties,
1350 including, but not limited to, the implied warranties of merchantability
1351 and fitness for a particular purpose are disclaimed. See the LICENSE
1352 file distributed with B<sudo> or http://www.sudo.ws/sudo/license.html
1353 for complete details.