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 1.95.2.23 2008/01/05 23:59:42 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][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. If the command matched is B<ALL>, the
340 C<SETENV> tag is implied for that command; this default may
341 be overridden by use of the C<UNSETENV> tag.
345 B<sudo> allows shell-style I<wildcards> (aka meta or glob characters)
346 to be used in pathnames as well as command line arguments in the
347 I<sudoers> file. Wildcard matching is done via the B<POSIX>
348 L<fnmatch(3)> routine. Note that these are I<not> regular expressions.
354 Matches any set of zero or more characters.
358 Matches any single character.
362 Matches any character in the specified range.
366 Matches any character B<not> in the specified range.
370 For any character "x", evaluates to "x". This is used to
371 escape special characters such as: "*", "?", "[", and "}".
375 Note that a forward slash ('/') will B<not> be matched by
376 wildcards used in the pathname. When matching the command
377 line arguments, however, a slash B<does> get matched by
378 wildcards. This is to make a path like:
382 match F</usr/bin/who> but not F</usr/bin/X11/xterm>.
384 =head2 Exceptions to wildcard rules
386 The following exceptions apply to the above rules:
392 If the empty string C<""> is the only command line argument in the
393 I<sudoers> entry it means that command is not allowed to be run
394 with B<any> arguments.
398 =head2 Other special characters and reserved words
400 The pound sign ('#') is used to indicate a comment (unless it is
401 part of a #include directive or unless it occurs in the context of
402 a user name and is followed by one or more digits, in which case
403 it is treated as a uid). Both the comment character and any text
404 after it, up to the end of the line, are ignored.
406 The reserved word B<ALL> is a built-in I<alias> that always causes
407 a match to succeed. It can be used wherever one might otherwise
408 use a C<Cmnd_Alias>, C<User_Alias>, C<Runas_Alias>, or C<Host_Alias>.
409 You should not try to define your own I<alias> called B<ALL> as the
410 built-in alias will be used in preference to your own. Please note
411 that using B<ALL> can be dangerous since in a command context, it
412 allows the user to run B<any> command on the system.
414 An exclamation point ('!') can be used as a logical I<not> operator
415 both in an I<alias> and in front of a C<Cmnd>. This allows one to
416 exclude certain values. Note, however, that using a C<!> in
417 conjunction with the built-in C<ALL> alias to allow a user to
418 run "all but a few" commands rarely works as intended (see SECURITY
421 Long lines can be continued with a backslash ('\') as the last
422 character on the line.
424 Whitespace between elements in a list as well as special syntactic
425 characters in a I<User Specification> ('=', ':', '(', ')') is optional.
427 The following characters must be escaped with a backslash ('\') when
428 used as part of a word (e.g.E<nbsp>a username or hostname):
429 '@', '!', '=', ':', ',', '(', ')', '\'.
431 =head1 SUDOERS OPTIONS
433 B<sudo>'s behavior can be modified by C<Default_Entry> lines, as
434 explained earlier. A list of all supported Defaults parameters,
435 grouped by type, are listed below.
441 =item always_set_home
443 If set, B<sudo> will set the C<HOME> environment variable to the home
444 directory of the target user (which is root unless the B<-u> option is used).
445 This effectively means that the B<-H> flag is always implied.
446 This flag is I<off> by default.
450 If set, users must authenticate themselves via a password (or other
451 means of authentication) before they may run commands. This default
452 may be overridden via the C<PASSWD> and C<NOPASSWD> tags.
453 This flag is I<on> by default.
457 If set, B<visudo> will use the value of the EDITOR or VISUAL
458 environment variables before falling back on the default editor list.
459 Note that this may create a security hole as it allows the user to
460 run any arbitrary command as root without logging. A safer alternative
461 is to place a colon-separated list of editors in the C<editor>
462 variable. B<visudo> will then only use the EDITOR or VISUAL if
463 they match a value specified in C<editor>. This flag is I<@env_editor@> by
468 If set, B<sudo> will reset the environment to only contain the
469 LOGNAME, SHELL, USER, USERNAME and the C<SUDO_*> variables. Any
470 variables in the caller's environment that match the C<env_keep>
471 and C<env_check> lists are then added. The default contents of the
472 C<env_keep> and C<env_check> lists are displayed when B<sudo> is
473 run by root with the I<-V> option. If B<sudo> was compiled with
474 the C<SECURE_PATH> option, its value will be used for the C<PATH>
475 environment variable. This flag is I<on> by default.
479 Set this flag if you want to put fully qualified hostnames in the
480 I<sudoers> file. I.e., instead of myhost you would use myhost.mydomain.edu.
481 You may still use the short form if you wish (and even mix the two).
482 Beware that turning on I<fqdn> requires B<sudo> to make DNS lookups
483 which may make affect B<sudo> performance if DNS stops working (for example
484 if the machine is not plugged into the network). The default behavior for
485 Debian has been modified to minimize the potential of a problem, but there
486 may still be some cases in which lack of working DNS might make sudo work
487 very slowly. Also note that
488 you must use the host's official name as DNS knows it. That is,
489 you may not use a host alias (C<CNAME> entry) due to performance
490 issues and the fact that there is no way to get all aliases from
491 DNS. If your machine's hostname (as returned by the C<hostname>
492 command) is already fully qualified you shouldn't need to set
493 I<fqdn>. This flag is I<@fqdn@> by default.
497 If set, B<sudo> will ignore '.' or '' (current dir) in the C<PATH>
498 environment variable; the C<PATH> itself is not modified. This
499 flag is I<@ignore_dot@> by default. Currently, while it is possible
500 to set I<ignore_dot> in I<sudoers>, its value is not used. This option
501 should be considered read-only (it will be fixed in a future version
504 =item ignore_local_sudoers
506 If set via LDAP, parsing of @sysconfdir@/sudoers will be skipped.
507 This is intended for Enterprises that wish to prevent the usage of local
508 sudoers files so that only LDAP is used. This thwarts the efforts of
509 rogue operators who would attempt to add roles to @sysconfdir@/sudoers.
510 When this option is present, @sysconfdir@/sudoers does not even need to exist.
511 Since this option tells B<sudo> how to behave when no specific LDAP entries
512 have been matched, this sudoOption is only meaningful for the cn=defaults
513 section. This flag is I<off> by default.
517 If set, B<sudo> will insult users when they enter an incorrect
518 password. This flag is I<@insults@> by default.
522 If set, the hostname will be logged in the (non-syslog) B<sudo> log file.
523 This flag is I<off> by default.
527 If set, the four-digit year will be logged in the (non-syslog) B<sudo> log file.
528 This flag is I<off> by default.
530 =item long_otp_prompt
532 When validating with a One Time Password (OPT) scheme such as
533 B<S/Key> or B<OPIE>, a two-line prompt is used to make it easier
534 to cut and paste the challenge to a local window. It's not as
535 pretty as the default but some people find it more convenient. This
536 flag is I<@long_otp_prompt@> by default.
540 Send mail to the I<mailto> user every time a users runs B<sudo>.
541 This flag is I<off> by default.
545 Send mail to the I<mailto> user if the user running B<sudo> does not
546 enter the correct password. This flag is I<off> by default.
550 If set, mail will be sent to the I<mailto> user if the invoking
551 user exists in the I<sudoers> file, but is not allowed to run
552 commands on the current host. This flag is I<@mail_no_host@> by default.
556 If set, mail will be sent to the I<mailto> user if the invoking
557 user is allowed to use B<sudo> but the command they are trying is not
558 listed in their I<sudoers> file entry or is explicitly denied.
559 This flag is I<@mail_no_perms@> by default.
563 If set, mail will be sent to the I<mailto> user if the invoking
564 user is not in the I<sudoers> file. This flag is I<@mail_no_user@>
569 If set, all commands run via B<sudo> will behave as if the C<NOEXEC>
570 tag has been set, unless overridden by a C<EXEC> tag. See the
571 description of I<NOEXEC and EXEC> below as well as the L<PREVENTING SHELL
572 ESCAPES> section at the end of this manual. This flag is I<off> by default.
576 Normally, B<sudo> will tell the user when a command could not be
577 found in their C<PATH> environment variable. Some sites may wish
578 to disable this as it could be used to gather information on the
579 location of executables that the normal user does not have access
580 to. The disadvantage is that if the executable is simply not in
581 the user's C<PATH>, B<sudo> will tell the user that they are not
582 allowed to run it, which can be confusing. This flag is I<@path_info@>
585 =item passprompt_override
587 The password prompt specified by I<passprompt> will normally only
588 be used if the passwod prompt provided by systems such as PAM matches
589 the string "Password:". If I<passprompt_override> is set, I<passprompt>
590 will always be used. This flag is I<off> by default.
592 =item preserve_groups
594 By default B<sudo> will initialize the group vector to the list of
595 groups the target user is in. When I<preserve_groups> is set, the
596 user's existing group vector is left unaltered. The real and
597 effective group IDs, however, are still set to match the target
598 user. This flag is I<off> by default.
602 If set, B<sudo> will only run when the user is logged in to a real
603 tty. This will disallow things like C<"rsh somehost sudo ls"> since
604 L<rsh(1)> does not allocate a tty. Because it is not possible to turn
605 off echo when there is no tty present, some sites may wish to set
606 this flag to prevent a user from entering a visible password. This
607 flag is I<off> by default.
611 If set, root is allowed to run B<sudo> too. Disabling this prevents users
612 from "chaining" B<sudo> commands to get a root shell by doing something
613 like C<"sudo sudo /bin/sh">. Note, however, that turning off I<root_sudo>
614 will also prevent root and from running B<sudoedit>.
615 Disabling I<root_sudo> provides no real additional security; it
616 exists purely for historical reasons.
617 This flag is I<@root_sudo@> by default.
621 If set, B<sudo> will prompt for the root password instead of the password
622 of the invoking user. This flag is I<off> by default.
626 If set, B<sudo> will prompt for the password of the user defined by the
627 I<runas_default> option (defaults to C<@runas_default@>) instead of the
628 password of the invoking user. This flag is I<off> by default.
632 If set and B<sudo> is invoked with the B<-s> flag the C<HOME>
633 environment variable will be set to the home directory of the target
634 user (which is root unless the B<-u> option is used). This effectively
635 makes the B<-s> flag imply B<-H>. This flag is I<off> by default.
639 Normally, B<sudo> will set the C<LOGNAME>, C<USER> and C<USERNAME>
640 environment variables to the name of the target user (usually root
641 unless the B<-u> flag is given). However, since some programs
642 (including the RCS revision control system) use C<LOGNAME> to
643 determine the real identity of the user, it may be desirable to
644 change this behavior. This can be done by negating the set_logname
645 option. Note that if the I<env_reset> option has not been disabled,
646 entries in the I<env_keep> list will override the value of
647 I<set_logname>. This flag is I<off> by default.
651 Allow the user to disable the I<env_reset> option from the command
652 line. Additionally, environment variables set via the command line
653 are not subject to the restrictions imposed by I<env_check>,
654 I<env_delete>, or I<env_keep>. As such, only trusted users should
655 be allowed to set variables in this manner. This flag is I<off>
660 If set and B<sudo> is invoked with no arguments it acts as if the
661 B<-s> flag had been given. That is, it runs a shell as root (the
662 shell is determined by the C<SHELL> environment variable if it is
663 set, falling back on the shell listed in the invoking user's
664 /etc/passwd entry if not). This flag is I<off> by default.
668 Normally, when B<sudo> executes a command the real and effective
669 UIDs are set to the target user (root by default). This option
670 changes that behavior such that the real UID is left as the invoking
671 user's UID. In other words, this makes B<sudo> act as a setuid
672 wrapper. This can be useful on systems that disable some potentially
673 dangerous functionality when a program is run setuid. This option
674 is only effective on systems with either the setreuid() or setresuid()
675 function. This flag is I<off> by default.
679 If set, B<sudo> will prompt for the password of the user specified by
680 the B<-u> flag (defaults to C<root>) instead of the password of the
681 invoking user. Note that this precludes the use of a uid not listed
682 in the passwd database as an argument to the B<-u> flag.
683 This flag is I<off> by default.
687 If set, users must authenticate on a per-tty basis. Normally,
688 B<sudo> uses a directory in the ticket dir with the same name as
689 the user running it. With this flag enabled, B<sudo> will use a
690 file named for the tty the user is logged in on in that directory.
691 This flag is I<@tty_tickets@> by default.
695 If set, B<sudo> will apply the defaults specified for the target user's
696 login class if one exists. Only available if B<sudo> is configured with
697 the --with-logincap option. This flag is I<off> by default.
707 The number of tries a user gets to enter his/her password before
708 B<sudo> logs the failure and exits. The default is C<@passwd_tries@>.
712 B<Integers that can be used in a boolean context>:
718 Number of characters per line for the file log. This value is used
719 to decide when to wrap lines for nicer log files. This has no
720 effect on the syslog log file, only the file log. The default is
721 C<@loglen@> (use 0 or negate the option to disable word wrap).
725 Number of minutes before the B<sudo> password prompt times out.
726 The default is C<@password_timeout@>; set this to C<0> for no password timeout.
728 =item timestamp_timeout
730 Number of minutes that can elapse before B<sudo> will ask for a
731 passwd again. The default is C<@timeout@>. Set this to C<0> to always
732 prompt for a password.
733 If set to a value less than C<0> the user's timestamp will never
734 expire. This can be used to allow users to create or delete their
735 own timestamps via C<sudo -v> and C<sudo -k> respectively.
739 Umask to use when running the command. Negate this option or set
740 it to 0777 to preserve the user's umask. The default is C<@sudo_umask@>.
748 =item badpass_message
750 Message that is displayed if a user enters an incorrect password.
751 The default is C<@badpass_message@> unless insults are enabled.
755 A colon (':') separated list of editors allowed to be used with
756 B<visudo>. B<visudo> will choose the editor that matches the user's
757 EDITOR environment variable if possible, or the first editor in the
758 list that exists and is executable. The default is the path to vi
763 Subject of the mail sent to the I<mailto> user. The escape C<%h>
764 will expand to the hostname of the machine.
765 Default is C<@mailsub@>.
769 Path to a shared library containing dummy versions of the execv(),
770 execve() and fexecve() library functions that just return an error.
771 This is used to implement the I<noexec> functionality on systems that
772 support C<LD_PRELOAD> or its equivalent. Defaults to F<@noexec_file@>.
776 The default prompt to use when asking for a password; can be overridden
777 via the B<-p> option or the C<SUDO_PROMPT> environment variable.
778 The following percent (`C<%>') escapes are supported:
784 expanded to the local hostname including the domain name
785 (on if the machine's hostname is fully qualified or the I<fqdn>
790 expanded to the local hostname without the domain name
794 expanded to the user whose password is being asked for (respects the
795 I<rootpw>, I<targetpw> and I<runaspw> flags in I<sudoers>)
799 expanded to the login name of the user the command will
800 be run as (defaults to root)
804 expanded to the invoking user's login name
808 two consecutive C<%> characters are collapsed into a single C<%> character
812 The default value is C<@passprompt@>.
816 The default user to run commands as if the B<-u> flag is not specified
817 on the command line. This defaults to C<@runas_default@>.
818 Note that if I<runas_default> is set it B<must> occur before
819 any C<Runas_Alias> specifications.
823 Syslog priority to use when user authenticates unsuccessfully.
824 Defaults to C<@badpri@>.
828 Syslog priority to use when user authenticates successfully.
829 Defaults to C<@goodpri@>.
833 The directory in which B<sudo> stores its timestamp files.
834 The default is F<@timedir@>.
838 The owner of the timestamp directory and the timestamps stored therein.
839 The default is C<root>.
843 B<Strings that can be used in a boolean context>:
849 Users in this group are exempt from password and PATH requirements.
850 This is not set by default.
854 This option controls when a short lecture will be printed along with
855 the password prompt. It has the following possible values:
861 Always lecture the user.
865 Never lecture the user.
869 Only lecture the user the first time they run B<sudo>.
873 If no value is specified, a value of I<once> is implied.
874 Negating the option results in a value of I<never> being used.
875 The default value is I<@lecture@>.
879 Path to a file containing an alternate B<sudo> lecture that will
880 be used in place of the standard lecture if the named file exists.
881 By default, B<sudo> uses a built-in lecture.
885 This option controls when a password will be required when a
886 user runs B<sudo> with the B<-l> flag. It has the following possible values:
892 All the user's I<sudoers> entries for the current host must have
893 the C<NOPASSWD> flag set to avoid entering a password.
897 The user must always enter a password to use the B<-l> flag.
901 At least one of the user's I<sudoers> entries for the current host
902 must have the C<NOPASSWD> flag set to avoid entering a password.
906 The user need never enter a password to use the B<-l> flag.
910 If no value is specified, a value of I<any> is implied.
911 Negating the option results in a value of I<never> being used.
912 The default value is I<any>.
916 Path to the B<sudo> log file (not the syslog log file). Setting a path
917 turns on logging to a file; negating this option turns it off.
918 By default, B<sudo> logs via syslog.
922 Flags to use when invoking mailer. Defaults to B<-t>.
926 Path to mail program used to send warning mail.
927 Defaults to the path to sendmail found at configure time.
931 Address to send warning and error mail to. The address should
932 be enclosed in double quotes (C<">) to protect against B<sudo>
933 interpreting the C<@> sign. Defaults to C<@mailto@>.
937 Syslog facility if syslog is being used for logging (negate to
938 disable syslog logging). Defaults to C<@logfac@>.
942 This option controls when a password will be required when a user runs
943 B<sudo> with the B<-v> flag. It has the following possible values:
949 All the user's I<sudoers> entries for the current host must have
950 the C<NOPASSWD> flag set to avoid entering a password.
954 The user must always enter a password to use the B<-v> flag.
958 At least one of the user's I<sudoers> entries for the current host
959 must have the C<NOPASSWD> flag set to avoid entering a password.
963 The user need never enter a password to use the B<-v> flag.
967 If no value is specified, a value of I<all> is implied.
968 Negating the option results in a value of I<never> being used.
969 The default value is I<all>.
973 B<Lists that can be used in a boolean context>:
979 Like I<env_keep>, but listed environment variables are taken from the user's environment if
980 the variable's value does B<not> contain C<%> or C</> characters. This can
981 be used to guard against printf-style format vulnerabilities in
982 poorly-written programs. The argument may be a double-quoted,
983 space-separated list or a single value without double-quotes. The
984 list can be replaced, added to, deleted from, or disabled by using
985 the C<=>, C<+=>, C<-=>, and C<!> operators respectively. Regardless
986 of whether the C<env_reset> option is enabled or disabled, variables
987 specified by C<env_check> will be preserved in the environment if
988 they pass the aforementioned check. The default list of environment
989 variables to check is displayed when B<sudo> is run by root with
995 Not effective due to security issues: only variables listed in
996 I<env_keep> or I<env_check> can be passed through B<sudo>!
998 The argument may be a double-quoted, space-separated list or a
999 single value without double-quotes. The list can be replaced, added
1000 to, deleted from, or disabled by using the C<=>, C<+=>, C<-=>, and
1001 C<!> operators respectively. The default list of environment
1002 variables to remove is displayed when B<sudo> is run by root with the
1003 I<-V> option. Note that many operating systems will remove potentially
1004 dangerous variables from the environment of any setuid process (such
1009 Environment variables to be preserved in the user's environment.
1010 This allows fine-grained
1011 control over the environment B<sudo>-spawned processes will receive.
1012 The argument may be a double-quoted, space-separated list or a
1013 single value without double-quotes. The list can be replaced, added
1014 to, deleted from, or disabled by using the C<=>, C<+=>, C<-=>, and
1015 C<!> operators respectively. The default list of variables to keep
1016 is displayed when B<sudo> is run by root with the I<-V> option.
1020 When logging via L<syslog(3)>, B<sudo> accepts the following values
1021 for the syslog facility (the value of the B<syslog> Parameter):
1022 B<authpriv> (if your OS supports it), B<auth>, B<daemon>, B<user>,
1023 B<local0>, B<local1>, B<local2>, B<local3>, B<local4>, B<local5>,
1024 B<local6>, and B<local7>. The following syslog priorities are
1025 supported: B<alert>, B<crit>, B<debug>, B<emerg>, B<err>, B<info>,
1026 B<notice>, and B<warning>.
1032 =item F<@sysconfdir@/sudoers>C< >
1033 List of who can run what
1035 =item F</etc/group>C< >
1038 =item F</etc/netgroup>C< >
1039 List of network groups
1045 Since the I<sudoers> file is parsed in a single pass, order is
1046 important. In general, you should structure I<sudoers> such that
1047 the C<Host_Alias>, C<User_Alias>, and C<Cmnd_Alias> specifications
1048 come first, followed by any C<Default_Entry> lines, and finally the
1049 C<Runas_Alias> and user specifications. The basic rule of thumb
1050 is that you cannot reference an Alias that has not already been defined.
1052 Below are example I<sudoers> entries. Admittedly, some of
1053 these are a bit contrived. First, we allow a few environment
1054 variables to pass and then define our I<aliases>:
1056 # Run X applications through sudo; HOME is used to find .Xauthority file
1057 # Note that some programs may use HOME for other purposes too and
1058 # this may lead to privilege escalation!
1059 Defaults env_keep = "DISPLAY HOME"
1061 # User alias specification
1062 User_Alias FULLTIMERS = millert, mikef, dowdy
1063 User_Alias PARTTIMERS = bostley, jwfox, crawl
1064 User_Alias WEBMASTERS = will, wendy, wim
1066 # Runas alias specification
1067 Runas_Alias OP = root, operator
1068 Runas_Alias DB = oracle, sybase
1070 # Host alias specification
1071 Host_Alias SPARC = bigtime, eclipse, moet, anchor :\
1072 SGI = grolsch, dandelion, black :\
1073 ALPHA = widget, thalamus, foobar :\
1074 HPPA = boa, nag, python
1075 Host_Alias CUNETS = 128.138.0.0/255.255.0.0
1076 Host_Alias CSNETS = 128.138.243.0, 128.138.204.0/24, 128.138.242.0
1077 Host_Alias SERVERS = master, mail, www, ns
1078 Host_Alias CDROM = orion, perseus, hercules
1080 # Cmnd alias specification
1081 Cmnd_Alias DUMPS = /usr/bin/mt, /usr/sbin/dump, /usr/sbin/rdump,\
1082 /usr/sbin/restore, /usr/sbin/rrestore
1083 Cmnd_Alias KILL = /usr/bin/kill
1084 Cmnd_Alias PRINTING = /usr/sbin/lpc, /usr/bin/lprm
1085 Cmnd_Alias SHUTDOWN = /usr/sbin/shutdown
1086 Cmnd_Alias HALT = /usr/sbin/halt
1087 Cmnd_Alias REBOOT = /usr/sbin/reboot
1088 Cmnd_Alias SHELLS = /usr/bin/sh, /usr/bin/csh, /usr/bin/ksh, \
1089 /usr/local/bin/tcsh, /usr/bin/rsh, \
1091 Cmnd_Alias SU = /usr/bin/su
1092 Cmnd_Alias PAGERS = /usr/bin/more, /usr/bin/pg, /usr/bin/less
1094 Here we override some of the compiled in default values. We want
1095 B<sudo> to log via L<syslog(3)> using the I<auth> facility in all
1096 cases. We don't want to subject the full time staff to the B<sudo>
1097 lecture, user B<millert> need not give a password, and we don't
1098 want to reset the C<LOGNAME>, C<USER> or C<USERNAME> environment
1099 variables when running commands as root. Additionally, on the
1100 machines in the I<SERVERS> C<Host_Alias>, we keep an additional
1101 local log file and make sure we log the year in each log line since
1102 the log entries will be kept around for several years. Lastly, we
1103 disable shell escapes for the commands in the PAGERS C<Cmnd_Alias>
1104 (F</usr/bin/more>, F</usr/bin/pg> and F</usr/bin/less>).
1106 # Override built-in defaults
1107 Defaults syslog=auth
1108 Defaults>root !set_logname
1109 Defaults:FULLTIMERS !lecture
1110 Defaults:millert !authenticate
1111 Defaults@SERVERS log_year, logfile=/var/log/sudo.log
1112 Defaults!PAGERS noexec
1114 The I<User specification> is the part that actually determines who may
1117 root ALL = (ALL) ALL
1118 %wheel ALL = (ALL) ALL
1120 We let B<root> and any user in group B<wheel> run any command on any
1123 FULLTIMERS ALL = NOPASSWD: ALL
1125 Full time sysadmins (B<millert>, B<mikef>, and B<dowdy>) may run any
1126 command on any host without authenticating themselves.
1128 PARTTIMERS ALL = ALL
1130 Part time sysadmins (B<bostley>, B<jwfox>, and B<crawl>) may run any
1131 command on any host but they must authenticate themselves first
1132 (since the entry lacks the C<NOPASSWD> tag).
1136 The user B<jack> may run any command on the machines in the I<CSNETS> alias
1137 (the networks C<128.138.243.0>, C<128.138.204.0>, and C<128.138.242.0>).
1138 Of those networks, only C<128.138.204.0> has an explicit netmask (in
1139 CIDR notation) indicating it is a class C network. For the other
1140 networks in I<CSNETS>, the local machine's netmask will be used
1145 The user B<lisa> may run any command on any host in the I<CUNETS> alias
1146 (the class B network C<128.138.0.0>).
1148 operator ALL = DUMPS, KILL, SHUTDOWN, HALT, REBOOT, PRINTING,\
1149 sudoedit /etc/printcap, /usr/oper/bin/
1151 The B<operator> user may run commands limited to simple maintenance.
1152 Here, those are commands related to backups, killing processes, the
1153 printing system, shutting down the system, and any commands in the
1154 directory F</usr/oper/bin/>.
1156 joe ALL = /usr/bin/su operator
1158 The user B<joe> may only L<su(1)> to operator.
1160 pete HPPA = /usr/bin/passwd [A-z]*, !/usr/bin/passwd root
1162 The user B<pete> is allowed to change anyone's password except for
1163 root on the I<HPPA> machines. Note that this assumes L<passwd(1)>
1164 does not take multiple usernames on the command line.
1166 bob SPARC = (OP) ALL : SGI = (OP) ALL
1168 The user B<bob> may run anything on the I<SPARC> and I<SGI> machines
1169 as any user listed in the I<OP> C<Runas_Alias> (B<root> and B<operator>).
1173 The user B<jim> may run any command on machines in the I<biglab> netgroup.
1174 B<sudo> knows that "biglab" is a netgroup due to the '+' prefix.
1176 +secretaries ALL = PRINTING, /usr/bin/adduser, /usr/bin/rmuser
1178 Users in the B<secretaries> netgroup need to help manage the printers
1179 as well as add and remove users, so they are allowed to run those
1180 commands on all machines.
1182 fred ALL = (DB) NOPASSWD: ALL
1184 The user B<fred> can run commands as any user in the I<DB> C<Runas_Alias>
1185 (B<oracle> or B<sybase>) without giving a password.
1187 john ALPHA = /usr/bin/su [!-]*, !/usr/bin/su *root*
1189 On the I<ALPHA> machines, user B<john> may su to anyone except root
1190 but he is not allowed to give L<su(1)> any flags.
1192 jen ALL, !SERVERS = ALL
1194 The user B<jen> may run any command on any machine except for those
1195 in the I<SERVERS> C<Host_Alias> (master, mail, www and ns).
1197 jill SERVERS = /usr/bin/, !SU, !SHELLS
1199 For any machine in the I<SERVERS> C<Host_Alias>, B<jill> may run
1200 any commands in the directory F</usr/bin/> except for those commands
1201 belonging to the I<SU> and I<SHELLS> C<Cmnd_Aliases>.
1203 steve CSNETS = (operator) /usr/local/op_commands/
1205 The user B<steve> may run any command in the directory /usr/local/op_commands/
1206 but only as user operator.
1208 matt valkyrie = KILL
1210 On his personal workstation, valkyrie, B<matt> needs to be able to
1211 kill hung processes.
1213 WEBMASTERS www = (www) ALL, (root) /usr/bin/su www
1215 On the host www, any user in the I<WEBMASTERS> C<User_Alias> (will,
1216 wendy, and wim), may run any command as user www (which owns the
1217 web pages) or simply L<su(1)> to www.
1219 ALL CDROM = NOPASSWD: /sbin/umount /CDROM,\
1220 /sbin/mount -o nosuid\,nodev /dev/cd0a /CDROM
1222 Any user may mount or unmount a CD-ROM on the machines in the CDROM
1223 C<Host_Alias> (orion, perseus, hercules) without entering a password.
1224 This is a bit tedious for users to type, so it is a prime candidate
1225 for encapsulating in a shell script.
1227 =head1 SECURITY NOTES
1229 It is generally not effective to "subtract" commands from C<ALL>
1230 using the '!' operator. A user can trivially circumvent this
1231 by copying the desired command to a different name and then
1232 executing that. For example:
1234 bill ALL = ALL, !SU, !SHELLS
1236 Doesn't really prevent B<bill> from running the commands listed in
1237 I<SU> or I<SHELLS> since he can simply copy those commands to a
1238 different name, or use a shell escape from an editor or other
1239 program. Therefore, these kind of restrictions should be considered
1240 advisory at best (and reinforced by policy).
1242 =head1 PREVENTING SHELL ESCAPES
1244 Once B<sudo> executes a program, that program is free to do whatever
1245 it pleases, including run other programs. This can be a security
1246 issue since it is not uncommon for a program to allow shell escapes,
1247 which lets a user bypass B<sudo>'s access control and logging.
1248 Common programs that permit shell escapes include shells (obviously),
1249 editors, paginators, mail and terminal programs.
1251 There are two basic approaches to this problem:
1257 Avoid giving users access to commands that allow the user to run
1258 arbitrary commands. Many editors have a restricted mode where shell
1259 escapes are disabled, though B<sudoedit> is a better solution to
1260 running editors via B<sudo>. Due to the large number of programs that
1261 offer shell escapes, restricting users to the set of programs that
1262 do not if often unworkable.
1266 Many systems that support shared libraries have the ability to
1267 override default library functions by pointing an environment
1268 variable (usually C<LD_PRELOAD>) to an alternate shared library.
1269 On such systems, B<sudo>'s I<noexec> functionality can be used to
1270 prevent a program run by B<sudo> from executing any other programs.
1271 Note, however, that this applies only to native dynamically-linked
1272 executables. Statically-linked executables and foreign executables
1273 running under binary emulation are not affected.
1275 To tell whether or not B<sudo> supports I<noexec>, you can run
1276 the following as root:
1278 sudo -V | grep "dummy exec"
1280 If the resulting output contains a line that begins with:
1282 File containing dummy exec functions:
1284 then B<sudo> may be able to replace the exec family of functions
1285 in the standard library with its own that simply return an error.
1286 Unfortunately, there is no foolproof way to know whether or not
1287 I<noexec> will work at compile-time. I<noexec> should work on
1288 SunOS, Solaris, *BSD, Linux, IRIX, Tru64 UNIX, MacOS X, and HP-UX
1289 11.x. It is known B<not> to work on AIX and UnixWare. I<noexec>
1290 is expected to work on most operating systems that support the
1291 C<LD_PRELOAD> environment variable. Check your operating system's
1292 manual pages for the dynamic linker (usually ld.so, ld.so.1, dyld,
1293 dld.sl, rld, or loader) to see if C<LD_PRELOAD> is supported.
1295 To enable I<noexec> for a command, use the C<NOEXEC> tag as documented
1296 in the User Specification section above. Here is that example again:
1298 aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
1300 This allows user B<aaron> to run F</usr/bin/more> and F</usr/bin/vi>
1301 with I<noexec> enabled. This will prevent those two commands from
1302 executing other commands (such as a shell). If you are unsure
1303 whether or not your system is capable of supporting I<noexec> you
1304 can always just try it out and see if it works.
1308 Note that restricting shell escapes is not a panacea. Programs
1309 running as root are still capable of many potentially hazardous
1310 operations (such as changing or overwriting files) that could lead
1311 to unintended privilege escalation. In the specific case of an
1312 editor, a safer approach is to give the user permission to run
1317 L<rsh(1)>, L<su(1)>, L<fnmatch(3)>, L<sudo(8)>, L<visudo(8)>
1321 The I<sudoers> file should B<always> be edited by the B<visudo>
1322 command which locks the file and does grammatical checking. It is
1323 imperative that I<sudoers> be free of syntax errors since B<sudo>
1324 will not run with a syntactically incorrect I<sudoers> file.
1326 When using netgroups of machines (as opposed to users), if you
1327 store fully qualified hostnames in the netgroup (as is usually the
1328 case), you either need to have the machine's hostname be fully qualified
1329 as returned by the C<hostname> command or use the I<fqdn> option in
1334 If you feel you have found a bug in B<sudo>, please submit a bug report
1335 at http://www.sudo.ws/sudo/bugs/
1339 Limited free support is available via the sudo-users mailing list,
1340 see http://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or
1341 search the archives.
1345 B<sudo> is provided ``AS IS'' and any express or implied warranties,
1346 including, but not limited to, the implied warranties of merchantability
1347 and fitness for a particular purpose are disclaimed. See the LICENSE
1348 file distributed with B<sudo> or http://www.sudo.ws/sudo/license.html
1349 for complete details.