2 Copyright (c) 1994-1996, 1998-2005, 2007
3 Todd C. Miller <Todd.Miller@courtesan.com>
5 Permission to use, copy, modify, and distribute this software for any
6 purpose with or without fee is hereby granted, provided that the above
7 copyright notice and this permission notice appear in all copies.
9 THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
18 Sponsored in part by the Defense Advanced Research Projects
19 Agency (DARPA) and Air Force Research Laboratory, Air Force
20 Materiel Command, USAF, under agreement number F39502-99-1-0512.
22 $Sudo: sudoers.pod,v 1.95.2.20 2007/08/27 19:52:28 millert Exp $
27 sudoers - list of which users may execute what
31 The I<sudoers> file is composed of two types of entries: aliases
32 (basically variables) and user specifications (which specify who
35 When multiple entries match for a user, they are applied in order.
36 Where there are multiple matches, the last match is used (which is
37 not necessarily the most specific match).
39 The I<sudoers> grammar will be described below in Extended Backus-Naur
40 Form (EBNF). Don't despair if you don't know what EBNF is; it is
41 fairly simple, and the definitions below are annotated.
43 =head2 Quick guide to EBNF
45 EBNF is a concise and exact way of describing the grammar of a language.
46 Each EBNF definition is made up of I<production rules>. E.g.,
48 symbol ::= definition | alternate1 | alternate2 ...
50 Each I<production rule> references others and thus makes up a
51 grammar for the language. EBNF also contains the following
52 operators, which many readers will recognize from regular
53 expressions. Do not, however, confuse them with "wildcard"
54 characters, which have different meanings.
60 Means that the preceding symbol (or group of symbols) is optional.
61 That is, it may appear once or not at all.
65 Means that the preceding symbol (or group of symbols) may appear
70 Means that the preceding symbol (or group of symbols) may appear
75 Parentheses may be used to group symbols together. For clarity,
76 we will use single quotes ('') to designate what is a verbatim character
77 string (as opposed to a symbol name).
81 There are four kinds of aliases: C<User_Alias>, C<Runas_Alias>,
82 C<Host_Alias> and C<Cmnd_Alias>.
84 Alias ::= 'User_Alias' User_Alias (':' User_Alias)* |
85 'Runas_Alias' Runas_Alias (':' Runas_Alias)* |
86 'Host_Alias' Host_Alias (':' Host_Alias)* |
87 'Cmnd_Alias' Cmnd_Alias (':' Cmnd_Alias)*
89 User_Alias ::= NAME '=' User_List
91 Runas_Alias ::= NAME '=' Runas_List
93 Host_Alias ::= NAME '=' Host_List
95 Cmnd_Alias ::= NAME '=' Cmnd_List
97 NAME ::= [A-Z]([A-Z][0-9]_)*
99 Each I<alias> definition is of the form
101 Alias_Type NAME = item1, item2, ...
103 where I<Alias_Type> is one of C<User_Alias>, C<Runas_Alias>, C<Host_Alias>,
104 or C<Cmnd_Alias>. A C<NAME> is a string of uppercase letters, numbers,
105 and underscore characters ('_'). A C<NAME> B<must> start with an
106 uppercase letter. It is possible to put several alias definitions
107 of the same type on a single line, joined by a colon (':'). E.g.,
109 Alias_Type NAME = item1, item2, item3 : NAME = item4, item5
111 The definitions of what constitutes a valid I<alias> member follow.
116 User ::= '!'* username |
121 A C<User_List> is made up of one or more usernames, system groups
122 (prefixed with '%'), netgroups (prefixed with '+') and other aliases.
123 Each list item may be prefixed with one or more '!' operators.
124 An odd number of '!' operators negate the value of the item; an even
125 number just cancel each other out.
127 Runas_List ::= Runas_User |
128 Runas_User ',' Runas_List
130 Runas_User ::= '!'* username |
136 A C<Runas_List> is similar to a C<User_List> except that it can
137 also contain uids (prefixed with '#') and instead of C<User_Alias>es
138 it can contain C<Runas_Alias>es. Note that usernames and groups
139 are matched as strings. In other words, two users (groups) with
140 the same uid (gid) are considered to be distinct. If you wish to
141 match all usernames with the same uid (e.g.E<nbsp>root and toor), you
142 can use a uid instead (#0 in the example given).
147 Host ::= '!'* hostname |
149 '!'* network(/netmask)? |
153 A C<Host_List> is made up of one or more hostnames, IP addresses,
154 network numbers, netgroups (prefixed with '+') and other aliases.
155 Again, the value of an item may be negated with the '!' operator.
156 If you do not specify a netmask along with the network number,
157 B<sudo> will query each of the local host's network interfaces and,
158 if the network number corresponds to one of the hosts's network
159 interfaces, the corresponding netmask will be used. The netmask
160 may be specified either in standard IP address notation
161 (e.g.E<nbsp>255.255.255.0 or ffff:ffff:ffff:ffff::),
162 or CIDR notation (number of bits, e.g.E<nbsp>24 or 64). A hostname may
163 include shell-style wildcards (see the L<Wildcards> section below),
164 but unless the C<hostname> command on your machine returns the fully
165 qualified hostname, you'll need to use the I<fqdn> option for
166 wildcards to be useful.
171 commandname ::= filename |
175 Cmnd ::= '!'* commandname |
180 A C<Cmnd_List> is a list of one or more commandnames, directories, and other
181 aliases. A commandname is a fully qualified filename which may include
182 shell-style wildcards (see the L<Wildcards> section below). A simple
183 filename allows the user to run the command with any arguments he/she
184 wishes. However, you may also specify command line arguments (including
185 wildcards). Alternately, you can specify C<""> to indicate that the command
186 may only be run B<without> command line arguments. A directory is a
187 fully qualified pathname ending in a '/'. When you specify a directory
188 in a C<Cmnd_List>, the user will be able to run any file within that directory
189 (but not in any subdirectories therein).
191 If a C<Cmnd> has associated command line arguments, then the arguments
192 in the C<Cmnd> must match exactly those given by the user on the command line
193 (or match the wildcards if there are any). Note that the following
194 characters must be escaped with a '\' if they are used in command
195 arguments: ',', ':', '=', '\'. The special command C<"sudoedit">
196 is used to permit a user to run B<sudo> with the B<-e> flag (or
197 as B<sudoedit>). It may take command line arguments just as
198 a normal command does.
202 Certain configuration options may be changed from their default
203 values at runtime via one or more C<Default_Entry> lines. These
204 may affect all users on any host, all users on a specific host, a
205 specific user, or commands being run as a specific user.
207 Default_Type ::= 'Defaults' |
208 'Defaults' '@' Host_List |
209 'Defaults' ':' User_List |
210 'Defaults' '>' Runas_List
212 Default_Entry ::= Default_Type Parameter_List
214 Parameter_List ::= Parameter |
215 Parameter ',' Parameter_List
217 Parameter ::= Parameter '=' Value |
218 Parameter '+=' Value |
219 Parameter '-=' Value |
222 Parameters may be B<flags>, B<integer> values, B<strings>, or B<lists>.
223 Flags are implicitly boolean and can be turned off via the '!'
224 operator. Some integer, string and list parameters may also be
225 used in a boolean context to disable them. Values may be enclosed
226 in double quotes (C<">) when they contain multiple words. Special
227 characters may be escaped with a backslash (C<\>).
229 Lists have two additional assignment operators, C<+=> and C<-=>.
230 These operators are used to add to and delete from a list respectively.
231 It is not an error to use the C<-=> operator to remove an element
232 that does not exist in a list.
234 See L</"SUDOERS OPTIONS"> for a list of supported Defaults parameters.
236 =head2 User Specification
238 User_Spec ::= User_List Host_List '=' Cmnd_Spec_List \
239 (':' Host_List '=' Cmnd_Spec_List)*
241 Cmnd_Spec_List ::= Cmnd_Spec |
242 Cmnd_Spec ',' Cmnd_Spec_List
244 Cmnd_Spec ::= Runas_Spec? Tag_Spec* Cmnd
246 Runas_Spec ::= '(' Runas_List ')'
248 Tag_Spec ::= ('NOPASSWD:' | 'PASSWD:' | 'NOEXEC:' | 'EXEC:' |
249 'SETENV:' | 'NOSETENV:')
251 A B<user specification> determines which commands a user may run
252 (and as what user) on specified hosts. By default, commands are
253 run as B<root>, but this can be changed on a per-command basis.
255 Let's break that down into its constituent parts:
259 A C<Runas_Spec> is simply a C<Runas_List> (as defined above)
260 enclosed in a set of parentheses. If you do not specify a
261 C<Runas_Spec> in the user specification, a default C<Runas_Spec>
262 of B<root> will be used. A C<Runas_Spec> sets the default for
263 commands that follow it. What this means is that for the entry:
265 dgb boulder = (operator) /bin/ls, /bin/kill, /usr/bin/lprm
267 The user B<dgb> may run F</bin/ls>, F</bin/kill>, and
268 F</usr/bin/lprm> -- but only as B<operator>. E.g.,
270 $ sudo -u operator /bin/ls.
272 It is also possible to override a C<Runas_Spec> later on in an
273 entry. If we modify the entry like so:
275 dgb boulder = (operator) /bin/ls, (root) /bin/kill, /usr/bin/lprm
277 Then user B<dgb> is now allowed to run F</bin/ls> as B<operator>,
278 but F</bin/kill> and F</usr/bin/lprm> as B<root>.
282 A command may have zero or more tags associated with it. There are
283 six possible tag values, C<NOPASSWD>, C<PASSWD>, C<NOEXEC>, C<EXEC>,
284 C<SETENV> and C<NOSETENV>.
285 Once a tag is set on a C<Cmnd>, subsequent C<Cmnd>s in the
286 C<Cmnd_Spec_List>, inherit the tag unless it is overridden by the
287 opposite tag (i.e.: C<PASSWD> overrides C<NOPASSWD> and C<NOEXEC>
290 =head3 NOPASSWD and PASSWD
292 By default, B<sudo> requires that a user authenticate him or herself
293 before running a command. This behavior can be modified via the
294 C<NOPASSWD> tag. Like a C<Runas_Spec>, the C<NOPASSWD> tag sets
295 a default for the commands that follow it in the C<Cmnd_Spec_List>.
296 Conversely, the C<PASSWD> tag can be used to reverse things.
299 ray rushmore = NOPASSWD: /bin/kill, /bin/ls, /usr/bin/lprm
301 would allow the user B<ray> to run F</bin/kill>, F</bin/ls>, and
302 F</usr/bin/lprm> as root on the machine rushmore as B<root> without
303 authenticating himself. If we only want B<ray> to be able to
304 run F</bin/kill> without a password the entry would be:
306 ray rushmore = NOPASSWD: /bin/kill, PASSWD: /bin/ls, /usr/bin/lprm
308 Note, however, that the C<PASSWD> tag has no effect on users who are
309 in the group specified by the I<exempt_group> option.
311 By default, if the C<NOPASSWD> tag is applied to any of the entries
312 for a user on the current host, he or she will be able to run
313 C<sudo -l> without a password. Additionally, a user may only run
314 C<sudo -v> without a password if the C<NOPASSWD> tag is present
315 for all a user's entries that pertain to the current host.
316 This behavior may be overridden via the verifypw and listpw options.
318 =head3 NOEXEC and EXEC
320 If B<sudo> has been compiled with I<noexec> support and the underlying
321 operating system supports it, the C<NOEXEC> tag can be used to prevent
322 a dynamically-linked executable from running further commands itself.
324 In the following example, user B<aaron> may run F</usr/bin/more>
325 and F</usr/bin/vi> but shell escapes will be disabled.
327 aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
329 See the L<PREVENTING SHELL ESCAPES> section below for more details
330 on how C<NOEXEC> works and whether or not it will work on your system.
332 =head3 SETENV and NOSETENV
334 These tags override the value of the I<setenv> option on a per-command
335 basis. Note that if C<SETENV> has been set for a command, any
336 environment variables set on the command line way are not subject
337 to the restrictions imposed by I<env_check>, I<env_delete>, or
338 I<env_keep>. As such, only trusted users should be allowed to set
339 variables in this manner.
343 B<sudo> allows shell-style I<wildcards> (aka meta or glob characters)
344 to be used in pathnames as well as command line arguments in the
345 I<sudoers> file. Wildcard matching is done via the B<POSIX>
346 L<fnmatch(3)> routine. Note that these are I<not> regular expressions.
352 Matches any set of zero or more characters.
356 Matches any single character.
360 Matches any character in the specified range.
364 Matches any character B<not> in the specified range.
368 For any character "x", evaluates to "x". This is used to
369 escape special characters such as: "*", "?", "[", and "}".
373 Note that a forward slash ('/') will B<not> be matched by
374 wildcards used in the pathname. When matching the command
375 line arguments, however, a slash B<does> get matched by
376 wildcards. This is to make a path like:
380 match F</usr/bin/who> but not F</usr/bin/X11/xterm>.
382 =head2 Exceptions to wildcard rules
384 The following exceptions apply to the above rules:
390 If the empty string C<""> is the only command line argument in the
391 I<sudoers> entry it means that command is not allowed to be run
392 with B<any> arguments.
396 =head2 Other special characters and reserved words
398 The pound sign ('#') is used to indicate a comment (unless it is
399 part of a #include directive or unless it occurs in the context of
400 a user name and is followed by one or more digits, in which case
401 it is treated as a uid). Both the comment character and any text
402 after it, up to the end of the line, are ignored.
404 The reserved word B<ALL> is a built-in I<alias> that always causes
405 a match to succeed. It can be used wherever one might otherwise
406 use a C<Cmnd_Alias>, C<User_Alias>, C<Runas_Alias>, or C<Host_Alias>.
407 You should not try to define your own I<alias> called B<ALL> as the
408 built-in alias will be used in preference to your own. Please note
409 that using B<ALL> can be dangerous since in a command context, it
410 allows the user to run B<any> command on the system.
412 An exclamation point ('!') can be used as a logical I<not> operator
413 both in an I<alias> and in front of a C<Cmnd>. This allows one to
414 exclude certain values. Note, however, that using a C<!> in
415 conjunction with the built-in C<ALL> alias to allow a user to
416 run "all but a few" commands rarely works as intended (see SECURITY
419 Long lines can be continued with a backslash ('\') as the last
420 character on the line.
422 Whitespace between elements in a list as well as special syntactic
423 characters in a I<User Specification> ('=', ':', '(', ')') is optional.
425 The following characters must be escaped with a backslash ('\') when
426 used as part of a word (e.g.E<nbsp>a username or hostname):
427 '@', '!', '=', ':', ',', '(', ')', '\'.
429 =head1 SUDOERS OPTIONS
431 B<sudo>'s behavior can be modified by C<Default_Entry> lines, as
432 explained earlier. A list of all supported Defaults parameters,
433 grouped by type, are listed below.
439 =item always_set_home
441 If set, B<sudo> will set the C<HOME> environment variable to the home
442 directory of the target user (which is root unless the B<-u> option is used).
443 This effectively means that the B<-H> flag is always implied.
444 This flag is I<off> by default.
448 If set, users must authenticate themselves via a password (or other
449 means of authentication) before they may run commands. This default
450 may be overridden via the C<PASSWD> and C<NOPASSWD> tags.
451 This flag is I<on> by default.
455 If set, B<visudo> will use the value of the EDITOR or VISUAL
456 environment variables before falling back on the default editor list.
457 Note that this may create a security hole as it allows the user to
458 run any arbitrary command as root without logging. A safer alternative
459 is to place a colon-separated list of editors in the C<editor>
460 variable. B<visudo> will then only use the EDITOR or VISUAL if
461 they match a value specified in C<editor>. This flag is I<@env_editor@> by
466 If set, B<sudo> will reset the environment to only contain the
467 LOGNAME, SHELL, USER, USERNAME and the C<SUDO_*> variables. Any
468 variables in the caller's environment that match the C<env_keep>
469 and C<env_check> lists are then added. The default contents of the
470 C<env_keep> and C<env_check> lists are displayed when B<sudo> is
471 run by root with the I<-V> option. If B<sudo> was compiled with
472 the C<SECURE_PATH> option, its value will be used for the C<PATH>
473 environment variable. This flag is I<on> by default.
477 Set this flag if you want to put fully qualified hostnames in the
478 I<sudoers> file. I.e., instead of myhost you would use myhost.mydomain.edu.
479 You may still use the short form if you wish (and even mix the two).
480 Beware that turning on I<fqdn> requires B<sudo> to make DNS lookups
481 which may make B<sudo> unusable if DNS stops working (for example
482 if the machine is not plugged into the network). Also note that
483 you must use the host's official name as DNS knows it. That is,
484 you may not use a host alias (C<CNAME> entry) due to performance
485 issues and the fact that there is no way to get all aliases from
486 DNS. If your machine's hostname (as returned by the C<hostname>
487 command) is already fully qualified you shouldn't need to set
488 I<fqdn>. This flag is I<@fqdn@> by default.
492 If set, B<sudo> will ignore '.' or '' (current dir) in the C<PATH>
493 environment variable; the C<PATH> itself is not modified. This
494 flag is I<@ignore_dot@> by default. Currently, while it is possible
495 to set I<ignore_dot> in I<sudoers>, its value is not used. This option
496 should be considered read-only (it will be fixed in a future version
499 =item ignore_local_sudoers
501 If set via LDAP, parsing of @sysconfdir@/sudoers will be skipped.
502 This is intended for Enterprises that wish to prevent the usage of local
503 sudoers files so that only LDAP is used. This thwarts the efforts of
504 rogue operators who would attempt to add roles to @sysconfdir@/sudoers.
505 When this option is present, @sysconfdir@/sudoers does not even need to exist.
506 Since this option tells B<sudo> how to behave when no specific LDAP entries
507 have been matched, this sudoOption is only meaningful for the cn=defaults
508 section. This flag is I<off> by default.
512 If set, B<sudo> will insult users when they enter an incorrect
513 password. This flag is I<@insults@> by default.
517 If set, the hostname will be logged in the (non-syslog) B<sudo> log file.
518 This flag is I<off> by default.
522 If set, the four-digit year will be logged in the (non-syslog) B<sudo> log file.
523 This flag is I<off> by default.
525 =item long_otp_prompt
527 When validating with a One Time Password (OPT) scheme such as
528 B<S/Key> or B<OPIE>, a two-line prompt is used to make it easier
529 to cut and paste the challenge to a local window. It's not as
530 pretty as the default but some people find it more convenient. This
531 flag is I<@long_otp_prompt@> by default.
535 Send mail to the I<mailto> user every time a users runs B<sudo>.
536 This flag is I<off> by default.
540 Send mail to the I<mailto> user if the user running B<sudo> does not
541 enter the correct password. This flag is I<off> by default.
545 If set, mail will be sent to the I<mailto> user if the invoking
546 user exists in the I<sudoers> file, but is not allowed to run
547 commands on the current host. This flag is I<@mail_no_host@> by default.
551 If set, mail will be sent to the I<mailto> user if the invoking
552 user is allowed to use B<sudo> but the command they are trying is not
553 listed in their I<sudoers> file entry or is explicitly denied.
554 This flag is I<@mail_no_perms@> by default.
558 If set, mail will be sent to the I<mailto> user if the invoking
559 user is not in the I<sudoers> file. This flag is I<@mail_no_user@>
564 If set, all commands run via B<sudo> will behave as if the C<NOEXEC>
565 tag has been set, unless overridden by a C<EXEC> tag. See the
566 description of I<NOEXEC and EXEC> below as well as the L<PREVENTING SHELL
567 ESCAPES> section at the end of this manual. This flag is I<off> by default.
571 Normally, B<sudo> will tell the user when a command could not be
572 found in their C<PATH> environment variable. Some sites may wish
573 to disable this as it could be used to gather information on the
574 location of executables that the normal user does not have access
575 to. The disadvantage is that if the executable is simply not in
576 the user's C<PATH>, B<sudo> will tell the user that they are not
577 allowed to run it, which can be confusing. This flag is I<@path_info@>
580 =item preserve_groups
582 By default B<sudo> will initialize the group vector to the list of
583 groups the target user is in. When I<preserve_groups> is set, the
584 user's existing group vector is left unaltered. The real and
585 effective group IDs, however, are still set to match the target
586 user. This flag is I<off> by default.
590 If set, B<sudo> will only run when the user is logged in to a real
591 tty. This will disallow things like C<"rsh somehost sudo ls"> since
592 L<rsh(1)> does not allocate a tty. Because it is not possible to turn
593 off echo when there is no tty present, some sites may wish to set
594 this flag to prevent a user from entering a visible password. This
595 flag is I<off> by default.
599 If set, root is allowed to run B<sudo> too. Disabling this prevents users
600 from "chaining" B<sudo> commands to get a root shell by doing something
601 like C<"sudo sudo /bin/sh">. Note, however, that turning off I<root_sudo>
602 will also prevent root and from running B<sudoedit>.
603 Disabling I<root_sudo> provides no real additional security; it
604 exists purely for historical reasons.
605 This flag is I<@root_sudo@> by default.
609 If set, B<sudo> will prompt for the root password instead of the password
610 of the invoking user. This flag is I<off> by default.
614 If set, B<sudo> will prompt for the password of the user defined by the
615 I<runas_default> option (defaults to C<@runas_default@>) instead of the
616 password of the invoking user. This flag is I<off> by default.
620 If set and B<sudo> is invoked with the B<-s> flag the C<HOME>
621 environment variable will be set to the home directory of the target
622 user (which is root unless the B<-u> option is used). This effectively
623 makes the B<-s> flag imply B<-H>. This flag is I<off> by default.
627 Normally, B<sudo> will set the C<LOGNAME>, C<USER> and C<USERNAME>
628 environment variables to the name of the target user (usually root
629 unless the B<-u> flag is given). However, since some programs
630 (including the RCS revision control system) use C<LOGNAME> to
631 determine the real identity of the user, it may be desirable to
632 change this behavior. This can be done by negating the set_logname
633 option. Note that if the I<env_reset> option has not been disabled,
634 entries in the I<env_keep> list will override the value of
635 I<set_logname>. This flag is I<off> by default.
639 Allow the user to disable the I<env_reset> option from the command
640 line. Additionally, environment variables set via the command line
641 are not subject to the restrictions imposed by I<env_check>,
642 I<env_delete>, or I<env_keep>. As such, only trusted users should
643 be allowed to set variables in this manner. This flag is I<off>
648 If set and B<sudo> is invoked with no arguments it acts as if the
649 B<-s> flag had been given. That is, it runs a shell as root (the
650 shell is determined by the C<SHELL> environment variable if it is
651 set, falling back on the shell listed in the invoking user's
652 /etc/passwd entry if not). This flag is I<off> by default.
656 Normally, when B<sudo> executes a command the real and effective
657 UIDs are set to the target user (root by default). This option
658 changes that behavior such that the real UID is left as the invoking
659 user's UID. In other words, this makes B<sudo> act as a setuid
660 wrapper. This can be useful on systems that disable some potentially
661 dangerous functionality when a program is run setuid. This option
662 is only effective on systems with either the setreuid() or setresuid()
663 function. This flag is I<off> by default.
667 If set, B<sudo> will prompt for the password of the user specified by
668 the B<-u> flag (defaults to C<root>) instead of the password of the
669 invoking user. Note that this precludes the use of a uid not listed
670 in the passwd database as an argument to the B<-u> flag.
671 This flag is I<off> by default.
675 If set, users must authenticate on a per-tty basis. Normally,
676 B<sudo> uses a directory in the ticket dir with the same name as
677 the user running it. With this flag enabled, B<sudo> will use a
678 file named for the tty the user is logged in on in that directory.
679 This flag is I<@tty_tickets@> by default.
683 If set, B<sudo> will apply the defaults specified for the target user's
684 login class if one exists. Only available if B<sudo> is configured with
685 the --with-logincap option. This flag is I<off> by default.
695 The number of tries a user gets to enter his/her password before
696 B<sudo> logs the failure and exits. The default is C<@passwd_tries@>.
700 B<Integers that can be used in a boolean context>:
706 Number of characters per line for the file log. This value is used
707 to decide when to wrap lines for nicer log files. This has no
708 effect on the syslog log file, only the file log. The default is
709 C<@loglen@> (use 0 or negate the option to disable word wrap).
713 Number of minutes before the B<sudo> password prompt times out.
714 The default is C<@password_timeout@>; set this to C<0> for no password timeout.
716 =item timestamp_timeout
718 Number of minutes that can elapse before B<sudo> will ask for a
719 passwd again. The default is C<@timeout@>. Set this to C<0> to always
720 prompt for a password.
721 If set to a value less than C<0> the user's timestamp will never
722 expire. This can be used to allow users to create or delete their
723 own timestamps via C<sudo -v> and C<sudo -k> respectively.
727 Umask to use when running the command. Negate this option or set
728 it to 0777 to preserve the user's umask. The default is C<@sudo_umask@>.
736 =item badpass_message
738 Message that is displayed if a user enters an incorrect password.
739 The default is C<@badpass_message@> unless insults are enabled.
743 A colon (':') separated list of editors allowed to be used with
744 B<visudo>. B<visudo> will choose the editor that matches the user's
745 EDITOR environment variable if possible, or the first editor in the
746 list that exists and is executable. The default is the path to vi
751 Subject of the mail sent to the I<mailto> user. The escape C<%h>
752 will expand to the hostname of the machine.
753 Default is C<@mailsub@>.
757 Path to a shared library containing dummy versions of the execv(),
758 execve() and fexecve() library functions that just return an error.
759 This is used to implement the I<noexec> functionality on systems that
760 support C<LD_PRELOAD> or its equivalent. Defaults to F<@noexec_file@>.
764 The default prompt to use when asking for a password; can be overridden
765 via the B<-p> option or the C<SUDO_PROMPT> environment variable.
766 The following percent (`C<%>') escapes are supported:
772 expanded to the local hostname including the domain name
773 (on if the machine's hostname is fully qualified or the I<fqdn>
778 expanded to the local hostname without the domain name
782 expanded to the login name of the user the command will
783 be run as (defaults to root)
787 expanded to the invoking user's login name
791 two consecutive C<%> characters are collapsed into a single C<%> character
795 The default value is C<@passprompt@>.
799 The default user to run commands as if the B<-u> flag is not specified
800 on the command line. This defaults to C<@runas_default@>.
801 Note that if I<runas_default> is set it B<must> occur before
802 any C<Runas_Alias> specifications.
806 Syslog priority to use when user authenticates unsuccessfully.
807 Defaults to C<@badpri@>.
811 Syslog priority to use when user authenticates successfully.
812 Defaults to C<@goodpri@>.
816 The directory in which B<sudo> stores its timestamp files.
817 The default is F<@timedir@>.
821 The owner of the timestamp directory and the timestamps stored therein.
822 The default is C<root>.
826 B<Strings that can be used in a boolean context>:
832 Users in this group are exempt from password and PATH requirements.
833 This is not set by default.
837 This option controls when a short lecture will be printed along with
838 the password prompt. It has the following possible values:
844 Always lecture the user.
848 Never lecture the user.
852 Only lecture the user the first time they run B<sudo>.
856 If no value is specified, a value of I<once> is implied.
857 Negating the option results in a value of I<never> being used.
858 The default value is I<@lecture@>.
862 Path to a file containing an alternate B<sudo> lecture that will
863 be used in place of the standard lecture if the named file exists.
864 By default, B<sudo> uses a built-in lecture.
868 This option controls when a password will be required when a
869 user runs B<sudo> with the B<-l> flag. It has the following possible values:
875 All the user's I<sudoers> entries for the current host must have
876 the C<NOPASSWD> flag set to avoid entering a password.
880 The user must always enter a password to use the B<-l> flag.
884 At least one of the user's I<sudoers> entries for the current host
885 must have the C<NOPASSWD> flag set to avoid entering a password.
889 The user need never enter a password to use the B<-l> flag.
893 If no value is specified, a value of I<any> is implied.
894 Negating the option results in a value of I<never> being used.
895 The default value is I<any>.
899 Path to the B<sudo> log file (not the syslog log file). Setting a path
900 turns on logging to a file; negating this option turns it off.
901 By default, B<sudo> logs via syslog.
905 Flags to use when invoking mailer. Defaults to B<-t>.
909 Path to mail program used to send warning mail.
910 Defaults to the path to sendmail found at configure time.
914 Address to send warning and error mail to. The address should
915 be enclosed in double quotes (C<">) to protect against B<sudo>
916 interpreting the C<@> sign. Defaults to C<@mailto@>.
920 Syslog facility if syslog is being used for logging (negate to
921 disable syslog logging). Defaults to C<@logfac@>.
925 This option controls when a password will be required when a user runs
926 B<sudo> with the B<-v> flag. It has the following possible values:
932 All the user's I<sudoers> entries for the current host must have
933 the C<NOPASSWD> flag set to avoid entering a password.
937 The user must always enter a password to use the B<-v> flag.
941 At least one of the user's I<sudoers> entries for the current host
942 must have the C<NOPASSWD> flag set to avoid entering a password.
946 The user need never enter a password to use the B<-v> flag.
950 If no value is specified, a value of I<all> is implied.
951 Negating the option results in a value of I<never> being used.
952 The default value is I<all>.
956 B<Lists that can be used in a boolean context>:
962 Environment variables to be removed from the user's environment if
963 the variable's value contains C<%> or C</> characters. This can
964 be used to guard against printf-style format vulnerabilities in
965 poorly-written programs. The argument may be a double-quoted,
966 space-separated list or a single value without double-quotes. The
967 list can be replaced, added to, deleted from, or disabled by using
968 the C<=>, C<+=>, C<-=>, and C<!> operators respectively. Regardless
969 of whether the C<env_reset> option is enabled or disabled, variables
970 specified by C<env_check> will be preserved in the environment if
971 they pass the aforementioned check. The default list of environment
972 variables to check is displayed when B<sudo> is run by root with
977 Environment variables to be removed from the user's environment.
978 The argument may be a double-quoted, space-separated list or a
979 single value without double-quotes. The list can be replaced, added
980 to, deleted from, or disabled by using the C<=>, C<+=>, C<-=>, and
981 C<!> operators respectively. The default list of environment
982 variables to remove is displayed when B<sudo> is run by root with the
983 I<-V> option. Note that many operating systems will remove potentially
984 dangerous variables from the environment of any setuid process (such
989 Environment variables to be preserved in the user's environment
990 when the I<env_reset> option is in effect. This allows fine-grained
991 control over the environment B<sudo>-spawned processes will receive.
992 The argument may be a double-quoted, space-separated list or a
993 single value without double-quotes. The list can be replaced, added
994 to, deleted from, or disabled by using the C<=>, C<+=>, C<-=>, and
995 C<!> operators respectively. The default list of variables to keep
996 is displayed when B<sudo> is run by root with the I<-V> option.
1000 When logging via L<syslog(3)>, B<sudo> accepts the following values
1001 for the syslog facility (the value of the B<syslog> Parameter):
1002 B<authpriv> (if your OS supports it), B<auth>, B<daemon>, B<user>,
1003 B<local0>, B<local1>, B<local2>, B<local3>, B<local4>, B<local5>,
1004 B<local6>, and B<local7>. The following syslog priorities are
1005 supported: B<alert>, B<crit>, B<debug>, B<emerg>, B<err>, B<info>,
1006 B<notice>, and B<warning>.
1012 =item F<@sysconfdir@/sudoers>C< >
1013 List of who can run what
1015 =item F</etc/group>C< >
1018 =item F</etc/netgroup>C< >
1019 List of network groups
1025 Since the I<sudoers> file is parsed in a single pass, order is
1026 important. In general, you should structure I<sudoers> such that
1027 the C<Host_Alias>, C<User_Alias>, and C<Cmnd_Alias> specifications
1028 come first, followed by any C<Default_Entry> lines, and finally the
1029 C<Runas_Alias> and user specifications. The basic rule of thumb
1030 is you cannot reference an Alias that has not already been defined.
1032 Below are example I<sudoers> entries. Admittedly, some of
1033 these are a bit contrived. First, we define our I<aliases>:
1035 # User alias specification
1036 User_Alias FULLTIMERS = millert, mikef, dowdy
1037 User_Alias PARTTIMERS = bostley, jwfox, crawl
1038 User_Alias WEBMASTERS = will, wendy, wim
1040 # Runas alias specification
1041 Runas_Alias OP = root, operator
1042 Runas_Alias DB = oracle, sybase
1044 # Host alias specification
1045 Host_Alias SPARC = bigtime, eclipse, moet, anchor :\
1046 SGI = grolsch, dandelion, black :\
1047 ALPHA = widget, thalamus, foobar :\
1048 HPPA = boa, nag, python
1049 Host_Alias CUNETS = 128.138.0.0/255.255.0.0
1050 Host_Alias CSNETS = 128.138.243.0, 128.138.204.0/24, 128.138.242.0
1051 Host_Alias SERVERS = master, mail, www, ns
1052 Host_Alias CDROM = orion, perseus, hercules
1054 # Cmnd alias specification
1055 Cmnd_Alias DUMPS = /usr/bin/mt, /usr/sbin/dump, /usr/sbin/rdump,\
1056 /usr/sbin/restore, /usr/sbin/rrestore
1057 Cmnd_Alias KILL = /usr/bin/kill
1058 Cmnd_Alias PRINTING = /usr/sbin/lpc, /usr/bin/lprm
1059 Cmnd_Alias SHUTDOWN = /usr/sbin/shutdown
1060 Cmnd_Alias HALT = /usr/sbin/halt
1061 Cmnd_Alias REBOOT = /usr/sbin/reboot
1062 Cmnd_Alias SHELLS = /usr/bin/sh, /usr/bin/csh, /usr/bin/ksh, \
1063 /usr/local/bin/tcsh, /usr/bin/rsh, \
1065 Cmnd_Alias SU = /usr/bin/su
1066 Cmnd_Alias PAGERS = /usr/bin/more, /usr/bin/pg, /usr/bin/less
1068 Here we override some of the compiled in default values. We want
1069 B<sudo> to log via L<syslog(3)> using the I<auth> facility in all
1070 cases. We don't want to subject the full time staff to the B<sudo>
1071 lecture, user B<millert> need not give a password, and we don't
1072 want to reset the C<LOGNAME>, C<USER> or C<USERNAME> environment
1073 variables when running commands as root. Additionally, on the
1074 machines in the I<SERVERS> C<Host_Alias>, we keep an additional
1075 local log file and make sure we log the year in each log line since
1076 the log entries will be kept around for several years. Lastly, we
1077 disable shell escapes for the commands in the PAGERS C<Cmnd_Alias>
1078 (F</usr/bin/more>, F</usr/bin/pg> and F</usr/bin/less>).
1080 # Override built-in defaults
1081 Defaults syslog=auth
1082 Defaults>root !set_logname
1083 Defaults:FULLTIMERS !lecture
1084 Defaults:millert !authenticate
1085 Defaults@SERVERS log_year, logfile=/var/log/sudo.log
1086 Defaults!PAGERS noexec
1088 The I<User specification> is the part that actually determines who may
1091 root ALL = (ALL) ALL
1092 %wheel ALL = (ALL) ALL
1094 We let B<root> and any user in group B<wheel> run any command on any
1097 FULLTIMERS ALL = NOPASSWD: ALL
1099 Full time sysadmins (B<millert>, B<mikef>, and B<dowdy>) may run any
1100 command on any host without authenticating themselves.
1102 PARTTIMERS ALL = ALL
1104 Part time sysadmins (B<bostley>, B<jwfox>, and B<crawl>) may run any
1105 command on any host but they must authenticate themselves first
1106 (since the entry lacks the C<NOPASSWD> tag).
1110 The user B<jack> may run any command on the machines in the I<CSNETS> alias
1111 (the networks C<128.138.243.0>, C<128.138.204.0>, and C<128.138.242.0>).
1112 Of those networks, only C<128.138.204.0> has an explicit netmask (in
1113 CIDR notation) indicating it is a class C network. For the other
1114 networks in I<CSNETS>, the local machine's netmask will be used
1119 The user B<lisa> may run any command on any host in the I<CUNETS> alias
1120 (the class B network C<128.138.0.0>).
1122 operator ALL = DUMPS, KILL, SHUTDOWN, HALT, REBOOT, PRINTING,\
1123 sudoedit /etc/printcap, /usr/oper/bin/
1125 The B<operator> user may run commands limited to simple maintenance.
1126 Here, those are commands related to backups, killing processes, the
1127 printing system, shutting down the system, and any commands in the
1128 directory F</usr/oper/bin/>.
1130 joe ALL = /usr/bin/su operator
1132 The user B<joe> may only L<su(1)> to operator.
1134 pete HPPA = /usr/bin/passwd [A-z]*, !/usr/bin/passwd root
1136 The user B<pete> is allowed to change anyone's password except for
1137 root on the I<HPPA> machines. Note that this assumes L<passwd(1)>
1138 does not take multiple usernames on the command line.
1140 bob SPARC = (OP) ALL : SGI = (OP) ALL
1142 The user B<bob> may run anything on the I<SPARC> and I<SGI> machines
1143 as any user listed in the I<OP> C<Runas_Alias> (B<root> and B<operator>).
1147 The user B<jim> may run any command on machines in the I<biglab> netgroup.
1148 B<sudo> knows that "biglab" is a netgroup due to the '+' prefix.
1150 +secretaries ALL = PRINTING, /usr/bin/adduser, /usr/bin/rmuser
1152 Users in the B<secretaries> netgroup need to help manage the printers
1153 as well as add and remove users, so they are allowed to run those
1154 commands on all machines.
1156 fred ALL = (DB) NOPASSWD: ALL
1158 The user B<fred> can run commands as any user in the I<DB> C<Runas_Alias>
1159 (B<oracle> or B<sybase>) without giving a password.
1161 john ALPHA = /usr/bin/su [!-]*, !/usr/bin/su *root*
1163 On the I<ALPHA> machines, user B<john> may su to anyone except root
1164 but he is not allowed to give L<su(1)> any flags.
1166 jen ALL, !SERVERS = ALL
1168 The user B<jen> may run any command on any machine except for those
1169 in the I<SERVERS> C<Host_Alias> (master, mail, www and ns).
1171 jill SERVERS = /usr/bin/, !SU, !SHELLS
1173 For any machine in the I<SERVERS> C<Host_Alias>, B<jill> may run
1174 any commands in the directory F</usr/bin/> except for those commands
1175 belonging to the I<SU> and I<SHELLS> C<Cmnd_Aliases>.
1177 steve CSNETS = (operator) /usr/local/op_commands/
1179 The user B<steve> may run any command in the directory /usr/local/op_commands/
1180 but only as user operator.
1182 matt valkyrie = KILL
1184 On his personal workstation, valkyrie, B<matt> needs to be able to
1185 kill hung processes.
1187 WEBMASTERS www = (www) ALL, (root) /usr/bin/su www
1189 On the host www, any user in the I<WEBMASTERS> C<User_Alias> (will,
1190 wendy, and wim), may run any command as user www (which owns the
1191 web pages) or simply L<su(1)> to www.
1193 ALL CDROM = NOPASSWD: /sbin/umount /CDROM,\
1194 /sbin/mount -o nosuid\,nodev /dev/cd0a /CDROM
1196 Any user may mount or unmount a CD-ROM on the machines in the CDROM
1197 C<Host_Alias> (orion, perseus, hercules) without entering a password.
1198 This is a bit tedious for users to type, so it is a prime candidate
1199 for encapsulating in a shell script.
1201 =head1 SECURITY NOTES
1203 It is generally not effective to "subtract" commands from C<ALL>
1204 using the '!' operator. A user can trivially circumvent this
1205 by copying the desired command to a different name and then
1206 executing that. For example:
1208 bill ALL = ALL, !SU, !SHELLS
1210 Doesn't really prevent B<bill> from running the commands listed in
1211 I<SU> or I<SHELLS> since he can simply copy those commands to a
1212 different name, or use a shell escape from an editor or other
1213 program. Therefore, these kind of restrictions should be considered
1214 advisory at best (and reinforced by policy).
1216 =head1 PREVENTING SHELL ESCAPES
1218 Once B<sudo> executes a program, that program is free to do whatever
1219 it pleases, including run other programs. This can be a security
1220 issue since it is not uncommon for a program to allow shell escapes,
1221 which lets a user bypass B<sudo>'s access control and logging.
1222 Common programs that permit shell escapes include shells (obviously),
1223 editors, paginators, mail and terminal programs.
1225 There are two basic approaches to this problem:
1231 Avoid giving users access to commands that allow the user to run
1232 arbitrary commands. Many editors have a restricted mode where shell
1233 escapes are disabled, though B<sudoedit> is a better solution to
1234 running editors via B<sudo>. Due to the large number of programs that
1235 offer shell escapes, restricting users to the set of programs that
1236 do not if often unworkable.
1240 Many systems that support shared libraries have the ability to
1241 override default library functions by pointing an environment
1242 variable (usually C<LD_PRELOAD>) to an alternate shared library.
1243 On such systems, B<sudo>'s I<noexec> functionality can be used to
1244 prevent a program run by B<sudo> from executing any other programs.
1245 Note, however, that this applies only to native dynamically-linked
1246 executables. Statically-linked executables and foreign executables
1247 running under binary emulation are not affected.
1249 To tell whether or not B<sudo> supports I<noexec>, you can run
1250 the following as root:
1252 sudo -V | grep "dummy exec"
1254 If the resulting output contains a line that begins with:
1256 File containing dummy exec functions:
1258 then B<sudo> may be able to replace the exec family of functions
1259 in the standard library with its own that simply return an error.
1260 Unfortunately, there is no foolproof way to know whether or not
1261 I<noexec> will work at compile-time. I<noexec> should work on
1262 SunOS, Solaris, *BSD, Linux, IRIX, Tru64 UNIX, MacOS X, and HP-UX
1263 11.x. It is known B<not> to work on AIX and UnixWare. I<noexec>
1264 is expected to work on most operating systems that support the
1265 C<LD_PRELOAD> environment variable. Check your operating system's
1266 manual pages for the dynamic linker (usually ld.so, ld.so.1, dyld,
1267 dld.sl, rld, or loader) to see if C<LD_PRELOAD> is supported.
1269 To enable I<noexec> for a command, use the C<NOEXEC> tag as documented
1270 in the User Specification section above. Here is that example again:
1272 aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
1274 This allows user B<aaron> to run F</usr/bin/more> and F</usr/bin/vi>
1275 with I<noexec> enabled. This will prevent those two commands from
1276 executing other commands (such as a shell). If you are unsure
1277 whether or not your system is capable of supporting I<noexec> you
1278 can always just try it out and see if it works.
1282 Note that restricting shell escapes is not a panacea. Programs
1283 running as root are still capable of many potentially hazardous
1284 operations (such as changing or overwriting files) that could lead
1285 to unintended privilege escalation. In the specific case of an
1286 editor, a safer approach is to give the user permission to run
1291 L<rsh(1)>, L<su(1)>, L<fnmatch(3)>, L<sudo(8)>, L<visudo(8)>
1295 The I<sudoers> file should B<always> be edited by the B<visudo>
1296 command which locks the file and does grammatical checking. It is
1297 imperative that I<sudoers> be free of syntax errors since B<sudo>
1298 will not run with a syntactically incorrect I<sudoers> file.
1300 When using netgroups of machines (as opposed to users), if you
1301 store fully qualified hostnames in the netgroup (as is usually the
1302 case), you either need to have the machine's hostname be fully qualified
1303 as returned by the C<hostname> command or use the I<fqdn> option in
1308 If you feel you have found a bug in B<sudo>, please submit a bug report
1309 at http://www.sudo.ws/sudo/bugs/
1313 Limited free support is available via the sudo-users mailing list,
1314 see http://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or
1315 search the archives.
1319 B<sudo> is provided ``AS IS'' and any express or implied warranties,
1320 including, but not limited to, the implied warranties of merchantability
1321 and fitness for a particular purpose are disclaimed. See the LICENSE
1322 file distributed with B<sudo> or http://www.sudo.ws/sudo/license.html
1323 for complete details.