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][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 affect B<sudo> performance if DNS stops working (for example
482 if the machine is not plugged into the network). The default behavior for
483 Debian has been modified to minimize the potential of a problem, but there
484 may still be some cases in which lack of working DNS might make sudo work
485 very slowly. Also note that
486 you must use the host's official name as DNS knows it. That is,
487 you may not use a host alias (C<CNAME> entry) due to performance
488 issues and the fact that there is no way to get all aliases from
489 DNS. If your machine's hostname (as returned by the C<hostname>
490 command) is already fully qualified you shouldn't need to set
491 I<fqdn>. This flag is I<@fqdn@> by default.
495 If set, B<sudo> will ignore '.' or '' (current dir) in the C<PATH>
496 environment variable; the C<PATH> itself is not modified. This
497 flag is I<@ignore_dot@> by default. Currently, while it is possible
498 to set I<ignore_dot> in I<sudoers>, its value is not used. This option
499 should be considered read-only (it will be fixed in a future version
502 =item ignore_local_sudoers
504 If set via LDAP, parsing of @sysconfdir@/sudoers will be skipped.
505 This is intended for Enterprises that wish to prevent the usage of local
506 sudoers files so that only LDAP is used. This thwarts the efforts of
507 rogue operators who would attempt to add roles to @sysconfdir@/sudoers.
508 When this option is present, @sysconfdir@/sudoers does not even need to exist.
509 Since this option tells B<sudo> how to behave when no specific LDAP entries
510 have been matched, this sudoOption is only meaningful for the cn=defaults
511 section. This flag is I<off> by default.
515 If set, B<sudo> will insult users when they enter an incorrect
516 password. This flag is I<@insults@> by default.
520 If set, the hostname will be logged in the (non-syslog) B<sudo> log file.
521 This flag is I<off> by default.
525 If set, the four-digit year will be logged in the (non-syslog) B<sudo> log file.
526 This flag is I<off> by default.
528 =item long_otp_prompt
530 When validating with a One Time Password (OPT) scheme such as
531 B<S/Key> or B<OPIE>, a two-line prompt is used to make it easier
532 to cut and paste the challenge to a local window. It's not as
533 pretty as the default but some people find it more convenient. This
534 flag is I<@long_otp_prompt@> by default.
538 Send mail to the I<mailto> user every time a users runs B<sudo>.
539 This flag is I<off> by default.
543 Send mail to the I<mailto> user if the user running B<sudo> does not
544 enter the correct password. This flag is I<off> by default.
548 If set, mail will be sent to the I<mailto> user if the invoking
549 user exists in the I<sudoers> file, but is not allowed to run
550 commands on the current host. This flag is I<@mail_no_host@> by default.
554 If set, mail will be sent to the I<mailto> user if the invoking
555 user is allowed to use B<sudo> but the command they are trying is not
556 listed in their I<sudoers> file entry or is explicitly denied.
557 This flag is I<@mail_no_perms@> by default.
561 If set, mail will be sent to the I<mailto> user if the invoking
562 user is not in the I<sudoers> file. This flag is I<@mail_no_user@>
567 If set, all commands run via B<sudo> will behave as if the C<NOEXEC>
568 tag has been set, unless overridden by a C<EXEC> tag. See the
569 description of I<NOEXEC and EXEC> below as well as the L<PREVENTING SHELL
570 ESCAPES> section at the end of this manual. This flag is I<off> by default.
574 Normally, B<sudo> will tell the user when a command could not be
575 found in their C<PATH> environment variable. Some sites may wish
576 to disable this as it could be used to gather information on the
577 location of executables that the normal user does not have access
578 to. The disadvantage is that if the executable is simply not in
579 the user's C<PATH>, B<sudo> will tell the user that they are not
580 allowed to run it, which can be confusing. This flag is I<@path_info@>
583 =item preserve_groups
585 By default B<sudo> will initialize the group vector to the list of
586 groups the target user is in. When I<preserve_groups> is set, the
587 user's existing group vector is left unaltered. The real and
588 effective group IDs, however, are still set to match the target
589 user. This flag is I<off> by default.
593 If set, B<sudo> will only run when the user is logged in to a real
594 tty. This will disallow things like C<"rsh somehost sudo ls"> since
595 L<rsh(1)> does not allocate a tty. Because it is not possible to turn
596 off echo when there is no tty present, some sites may wish to set
597 this flag to prevent a user from entering a visible password. This
598 flag is I<off> by default.
602 If set, root is allowed to run B<sudo> too. Disabling this prevents users
603 from "chaining" B<sudo> commands to get a root shell by doing something
604 like C<"sudo sudo /bin/sh">. Note, however, that turning off I<root_sudo>
605 will also prevent root and from running B<sudoedit>.
606 Disabling I<root_sudo> provides no real additional security; it
607 exists purely for historical reasons.
608 This flag is I<@root_sudo@> by default.
612 If set, B<sudo> will prompt for the root password instead of the password
613 of the invoking user. This flag is I<off> by default.
617 If set, B<sudo> will prompt for the password of the user defined by the
618 I<runas_default> option (defaults to C<@runas_default@>) instead of the
619 password of the invoking user. This flag is I<off> by default.
623 If set and B<sudo> is invoked with the B<-s> flag the C<HOME>
624 environment variable will be set to the home directory of the target
625 user (which is root unless the B<-u> option is used). This effectively
626 makes the B<-s> flag imply B<-H>. This flag is I<off> by default.
630 Normally, B<sudo> will set the C<LOGNAME>, C<USER> and C<USERNAME>
631 environment variables to the name of the target user (usually root
632 unless the B<-u> flag is given). However, since some programs
633 (including the RCS revision control system) use C<LOGNAME> to
634 determine the real identity of the user, it may be desirable to
635 change this behavior. This can be done by negating the set_logname
636 option. Note that if the I<env_reset> option has not been disabled,
637 entries in the I<env_keep> list will override the value of
638 I<set_logname>. This flag is I<off> by default.
642 Allow the user to disable the I<env_reset> option from the command
643 line. Additionally, environment variables set via the command line
644 are not subject to the restrictions imposed by I<env_check>,
645 I<env_delete>, or I<env_keep>. As such, only trusted users should
646 be allowed to set variables in this manner. This flag is I<off>
651 If set and B<sudo> is invoked with no arguments it acts as if the
652 B<-s> flag had been given. That is, it runs a shell as root (the
653 shell is determined by the C<SHELL> environment variable if it is
654 set, falling back on the shell listed in the invoking user's
655 /etc/passwd entry if not). This flag is I<off> by default.
659 Normally, when B<sudo> executes a command the real and effective
660 UIDs are set to the target user (root by default). This option
661 changes that behavior such that the real UID is left as the invoking
662 user's UID. In other words, this makes B<sudo> act as a setuid
663 wrapper. This can be useful on systems that disable some potentially
664 dangerous functionality when a program is run setuid. This option
665 is only effective on systems with either the setreuid() or setresuid()
666 function. This flag is I<off> by default.
670 If set, B<sudo> will prompt for the password of the user specified by
671 the B<-u> flag (defaults to C<root>) instead of the password of the
672 invoking user. Note that this precludes the use of a uid not listed
673 in the passwd database as an argument to the B<-u> flag.
674 This flag is I<off> by default.
678 If set, users must authenticate on a per-tty basis. Normally,
679 B<sudo> uses a directory in the ticket dir with the same name as
680 the user running it. With this flag enabled, B<sudo> will use a
681 file named for the tty the user is logged in on in that directory.
682 This flag is I<@tty_tickets@> by default.
686 If set, B<sudo> will apply the defaults specified for the target user's
687 login class if one exists. Only available if B<sudo> is configured with
688 the --with-logincap option. This flag is I<off> by default.
698 The number of tries a user gets to enter his/her password before
699 B<sudo> logs the failure and exits. The default is C<@passwd_tries@>.
703 B<Integers that can be used in a boolean context>:
709 Number of characters per line for the file log. This value is used
710 to decide when to wrap lines for nicer log files. This has no
711 effect on the syslog log file, only the file log. The default is
712 C<@loglen@> (use 0 or negate the option to disable word wrap).
716 Number of minutes before the B<sudo> password prompt times out.
717 The default is C<@password_timeout@>; set this to C<0> for no password timeout.
719 =item timestamp_timeout
721 Number of minutes that can elapse before B<sudo> will ask for a
722 passwd again. The default is C<@timeout@>. Set this to C<0> to always
723 prompt for a password.
724 If set to a value less than C<0> the user's timestamp will never
725 expire. This can be used to allow users to create or delete their
726 own timestamps via C<sudo -v> and C<sudo -k> respectively.
730 Umask to use when running the command. Negate this option or set
731 it to 0777 to preserve the user's umask. The default is C<@sudo_umask@>.
739 =item badpass_message
741 Message that is displayed if a user enters an incorrect password.
742 The default is C<@badpass_message@> unless insults are enabled.
746 A colon (':') separated list of editors allowed to be used with
747 B<visudo>. B<visudo> will choose the editor that matches the user's
748 EDITOR environment variable if possible, or the first editor in the
749 list that exists and is executable. The default is the path to vi
754 Subject of the mail sent to the I<mailto> user. The escape C<%h>
755 will expand to the hostname of the machine.
756 Default is C<@mailsub@>.
760 Path to a shared library containing dummy versions of the execv(),
761 execve() and fexecve() library functions that just return an error.
762 This is used to implement the I<noexec> functionality on systems that
763 support C<LD_PRELOAD> or its equivalent. Defaults to F<@noexec_file@>.
767 The default prompt to use when asking for a password; can be overridden
768 via the B<-p> option or the C<SUDO_PROMPT> environment variable.
769 The following percent (`C<%>') escapes are supported:
775 expanded to the local hostname including the domain name
776 (on if the machine's hostname is fully qualified or the I<fqdn>
781 expanded to the local hostname without the domain name
785 expanded to the login name of the user the command will
786 be run as (defaults to root)
790 expanded to the invoking user's login name
794 two consecutive C<%> characters are collapsed into a single C<%> character
798 The default value is C<@passprompt@>.
802 The default user to run commands as if the B<-u> flag is not specified
803 on the command line. This defaults to C<@runas_default@>.
804 Note that if I<runas_default> is set it B<must> occur before
805 any C<Runas_Alias> specifications.
809 Syslog priority to use when user authenticates unsuccessfully.
810 Defaults to C<@badpri@>.
814 Syslog priority to use when user authenticates successfully.
815 Defaults to C<@goodpri@>.
819 The directory in which B<sudo> stores its timestamp files.
820 The default is F<@timedir@>.
824 The owner of the timestamp directory and the timestamps stored therein.
825 The default is C<root>.
829 B<Strings that can be used in a boolean context>:
835 Users in this group are exempt from password and PATH requirements.
836 This is not set by default.
840 This option controls when a short lecture will be printed along with
841 the password prompt. It has the following possible values:
847 Always lecture the user.
851 Never lecture the user.
855 Only lecture the user the first time they run B<sudo>.
859 If no value is specified, a value of I<once> is implied.
860 Negating the option results in a value of I<never> being used.
861 The default value is I<@lecture@>.
865 Path to a file containing an alternate B<sudo> lecture that will
866 be used in place of the standard lecture if the named file exists.
867 By default, B<sudo> uses a built-in lecture.
871 This option controls when a password will be required when a
872 user runs B<sudo> with the B<-l> flag. It has the following possible values:
878 All the user's I<sudoers> entries for the current host must have
879 the C<NOPASSWD> flag set to avoid entering a password.
883 The user must always enter a password to use the B<-l> flag.
887 At least one of the user's I<sudoers> entries for the current host
888 must have the C<NOPASSWD> flag set to avoid entering a password.
892 The user need never enter a password to use the B<-l> flag.
896 If no value is specified, a value of I<any> is implied.
897 Negating the option results in a value of I<never> being used.
898 The default value is I<any>.
902 Path to the B<sudo> log file (not the syslog log file). Setting a path
903 turns on logging to a file; negating this option turns it off.
904 By default, B<sudo> logs via syslog.
908 Flags to use when invoking mailer. Defaults to B<-t>.
912 Path to mail program used to send warning mail.
913 Defaults to the path to sendmail found at configure time.
917 Address to send warning and error mail to. The address should
918 be enclosed in double quotes (C<">) to protect against B<sudo>
919 interpreting the C<@> sign. Defaults to C<@mailto@>.
923 Syslog facility if syslog is being used for logging (negate to
924 disable syslog logging). Defaults to C<@logfac@>.
928 This option controls when a password will be required when a user runs
929 B<sudo> with the B<-v> flag. It has the following possible values:
935 All the user's I<sudoers> entries for the current host must have
936 the C<NOPASSWD> flag set to avoid entering a password.
940 The user must always enter a password to use the B<-v> flag.
944 At least one of the user's I<sudoers> entries for the current host
945 must have the C<NOPASSWD> flag set to avoid entering a password.
949 The user need never enter a password to use the B<-v> flag.
953 If no value is specified, a value of I<all> is implied.
954 Negating the option results in a value of I<never> being used.
955 The default value is I<all>.
959 B<Lists that can be used in a boolean context>:
965 Like I<env_keep>, but listed environment variables are taken from the user's environment if
966 the variable's value does B<not> contain C<%> or C</> characters. This can
967 be used to guard against printf-style format vulnerabilities in
968 poorly-written programs. The argument may be a double-quoted,
969 space-separated list or a single value without double-quotes. The
970 list can be replaced, added to, deleted from, or disabled by using
971 the C<=>, C<+=>, C<-=>, and C<!> operators respectively. Regardless
972 of whether the C<env_reset> option is enabled or disabled, variables
973 specified by C<env_check> will be preserved in the environment if
974 they pass the aforementioned check. The default list of environment
975 variables to check is displayed when B<sudo> is run by root with
981 Not effective due to security issues: only variables listed in
982 I<env_keep> or I<env_check> can be passed through B<sudo>!
984 The argument may be a double-quoted, space-separated list or a
985 single value without double-quotes. The list can be replaced, added
986 to, deleted from, or disabled by using the C<=>, C<+=>, C<-=>, and
987 C<!> operators respectively. The default list of environment
988 variables to remove is displayed when B<sudo> is run by root with the
989 I<-V> option. Note that many operating systems will remove potentially
990 dangerous variables from the environment of any setuid process (such
995 Environment variables to be preserved in the user's environment.
996 This allows fine-grained
997 control over the environment B<sudo>-spawned processes will receive.
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 variables to keep
1002 is displayed when B<sudo> is run by root with the I<-V> option.
1006 When logging via L<syslog(3)>, B<sudo> accepts the following values
1007 for the syslog facility (the value of the B<syslog> Parameter):
1008 B<authpriv> (if your OS supports it), B<auth>, B<daemon>, B<user>,
1009 B<local0>, B<local1>, B<local2>, B<local3>, B<local4>, B<local5>,
1010 B<local6>, and B<local7>. The following syslog priorities are
1011 supported: B<alert>, B<crit>, B<debug>, B<emerg>, B<err>, B<info>,
1012 B<notice>, and B<warning>.
1018 =item F<@sysconfdir@/sudoers>C< >
1019 List of who can run what
1021 =item F</etc/group>C< >
1024 =item F</etc/netgroup>C< >
1025 List of network groups
1031 Since the I<sudoers> file is parsed in a single pass, order is
1032 important. In general, you should structure I<sudoers> such that
1033 the C<Host_Alias>, C<User_Alias>, and C<Cmnd_Alias> specifications
1034 come first, followed by any C<Default_Entry> lines, and finally the
1035 C<Runas_Alias> and user specifications. The basic rule of thumb
1036 is that you cannot reference an Alias that has not already been defined.
1038 Below are example I<sudoers> entries. Admittedly, some of
1039 these are a bit contrived. First, we allow a few environment
1040 variables to pass and then define our I<aliases>:
1042 # Run X applications through sudo; HOME is used to find .Xauthority file
1043 # Note that some programs may use HOME for other purposes too and
1044 # this may lead to privilege escalation!
1045 Defaults env_keep = "DISPLAY HOME"
1047 # User alias specification
1048 User_Alias FULLTIMERS = millert, mikef, dowdy
1049 User_Alias PARTTIMERS = bostley, jwfox, crawl
1050 User_Alias WEBMASTERS = will, wendy, wim
1052 # Runas alias specification
1053 Runas_Alias OP = root, operator
1054 Runas_Alias DB = oracle, sybase
1056 # Host alias specification
1057 Host_Alias SPARC = bigtime, eclipse, moet, anchor :\
1058 SGI = grolsch, dandelion, black :\
1059 ALPHA = widget, thalamus, foobar :\
1060 HPPA = boa, nag, python
1061 Host_Alias CUNETS = 128.138.0.0/255.255.0.0
1062 Host_Alias CSNETS = 128.138.243.0, 128.138.204.0/24, 128.138.242.0
1063 Host_Alias SERVERS = master, mail, www, ns
1064 Host_Alias CDROM = orion, perseus, hercules
1066 # Cmnd alias specification
1067 Cmnd_Alias DUMPS = /usr/bin/mt, /usr/sbin/dump, /usr/sbin/rdump,\
1068 /usr/sbin/restore, /usr/sbin/rrestore
1069 Cmnd_Alias KILL = /usr/bin/kill
1070 Cmnd_Alias PRINTING = /usr/sbin/lpc, /usr/bin/lprm
1071 Cmnd_Alias SHUTDOWN = /usr/sbin/shutdown
1072 Cmnd_Alias HALT = /usr/sbin/halt
1073 Cmnd_Alias REBOOT = /usr/sbin/reboot
1074 Cmnd_Alias SHELLS = /usr/bin/sh, /usr/bin/csh, /usr/bin/ksh, \
1075 /usr/local/bin/tcsh, /usr/bin/rsh, \
1077 Cmnd_Alias SU = /usr/bin/su
1078 Cmnd_Alias PAGERS = /usr/bin/more, /usr/bin/pg, /usr/bin/less
1080 Here we override some of the compiled in default values. We want
1081 B<sudo> to log via L<syslog(3)> using the I<auth> facility in all
1082 cases. We don't want to subject the full time staff to the B<sudo>
1083 lecture, user B<millert> need not give a password, and we don't
1084 want to reset the C<LOGNAME>, C<USER> or C<USERNAME> environment
1085 variables when running commands as root. Additionally, on the
1086 machines in the I<SERVERS> C<Host_Alias>, we keep an additional
1087 local log file and make sure we log the year in each log line since
1088 the log entries will be kept around for several years. Lastly, we
1089 disable shell escapes for the commands in the PAGERS C<Cmnd_Alias>
1090 (F</usr/bin/more>, F</usr/bin/pg> and F</usr/bin/less>).
1092 # Override built-in defaults
1093 Defaults syslog=auth
1094 Defaults>root !set_logname
1095 Defaults:FULLTIMERS !lecture
1096 Defaults:millert !authenticate
1097 Defaults@SERVERS log_year, logfile=/var/log/sudo.log
1098 Defaults!PAGERS noexec
1100 The I<User specification> is the part that actually determines who may
1103 root ALL = (ALL) ALL
1104 %wheel ALL = (ALL) ALL
1106 We let B<root> and any user in group B<wheel> run any command on any
1109 FULLTIMERS ALL = NOPASSWD: ALL
1111 Full time sysadmins (B<millert>, B<mikef>, and B<dowdy>) may run any
1112 command on any host without authenticating themselves.
1114 PARTTIMERS ALL = ALL
1116 Part time sysadmins (B<bostley>, B<jwfox>, and B<crawl>) may run any
1117 command on any host but they must authenticate themselves first
1118 (since the entry lacks the C<NOPASSWD> tag).
1122 The user B<jack> may run any command on the machines in the I<CSNETS> alias
1123 (the networks C<128.138.243.0>, C<128.138.204.0>, and C<128.138.242.0>).
1124 Of those networks, only C<128.138.204.0> has an explicit netmask (in
1125 CIDR notation) indicating it is a class C network. For the other
1126 networks in I<CSNETS>, the local machine's netmask will be used
1131 The user B<lisa> may run any command on any host in the I<CUNETS> alias
1132 (the class B network C<128.138.0.0>).
1134 operator ALL = DUMPS, KILL, SHUTDOWN, HALT, REBOOT, PRINTING,\
1135 sudoedit /etc/printcap, /usr/oper/bin/
1137 The B<operator> user may run commands limited to simple maintenance.
1138 Here, those are commands related to backups, killing processes, the
1139 printing system, shutting down the system, and any commands in the
1140 directory F</usr/oper/bin/>.
1142 joe ALL = /usr/bin/su operator
1144 The user B<joe> may only L<su(1)> to operator.
1146 pete HPPA = /usr/bin/passwd [A-z]*, !/usr/bin/passwd root
1148 The user B<pete> is allowed to change anyone's password except for
1149 root on the I<HPPA> machines. Note that this assumes L<passwd(1)>
1150 does not take multiple usernames on the command line.
1152 bob SPARC = (OP) ALL : SGI = (OP) ALL
1154 The user B<bob> may run anything on the I<SPARC> and I<SGI> machines
1155 as any user listed in the I<OP> C<Runas_Alias> (B<root> and B<operator>).
1159 The user B<jim> may run any command on machines in the I<biglab> netgroup.
1160 B<sudo> knows that "biglab" is a netgroup due to the '+' prefix.
1162 +secretaries ALL = PRINTING, /usr/bin/adduser, /usr/bin/rmuser
1164 Users in the B<secretaries> netgroup need to help manage the printers
1165 as well as add and remove users, so they are allowed to run those
1166 commands on all machines.
1168 fred ALL = (DB) NOPASSWD: ALL
1170 The user B<fred> can run commands as any user in the I<DB> C<Runas_Alias>
1171 (B<oracle> or B<sybase>) without giving a password.
1173 john ALPHA = /usr/bin/su [!-]*, !/usr/bin/su *root*
1175 On the I<ALPHA> machines, user B<john> may su to anyone except root
1176 but he is not allowed to give L<su(1)> any flags.
1178 jen ALL, !SERVERS = ALL
1180 The user B<jen> may run any command on any machine except for those
1181 in the I<SERVERS> C<Host_Alias> (master, mail, www and ns).
1183 jill SERVERS = /usr/bin/, !SU, !SHELLS
1185 For any machine in the I<SERVERS> C<Host_Alias>, B<jill> may run
1186 any commands in the directory F</usr/bin/> except for those commands
1187 belonging to the I<SU> and I<SHELLS> C<Cmnd_Aliases>.
1189 steve CSNETS = (operator) /usr/local/op_commands/
1191 The user B<steve> may run any command in the directory /usr/local/op_commands/
1192 but only as user operator.
1194 matt valkyrie = KILL
1196 On his personal workstation, valkyrie, B<matt> needs to be able to
1197 kill hung processes.
1199 WEBMASTERS www = (www) ALL, (root) /usr/bin/su www
1201 On the host www, any user in the I<WEBMASTERS> C<User_Alias> (will,
1202 wendy, and wim), may run any command as user www (which owns the
1203 web pages) or simply L<su(1)> to www.
1205 ALL CDROM = NOPASSWD: /sbin/umount /CDROM,\
1206 /sbin/mount -o nosuid\,nodev /dev/cd0a /CDROM
1208 Any user may mount or unmount a CD-ROM on the machines in the CDROM
1209 C<Host_Alias> (orion, perseus, hercules) without entering a password.
1210 This is a bit tedious for users to type, so it is a prime candidate
1211 for encapsulating in a shell script.
1213 =head1 SECURITY NOTES
1215 It is generally not effective to "subtract" commands from C<ALL>
1216 using the '!' operator. A user can trivially circumvent this
1217 by copying the desired command to a different name and then
1218 executing that. For example:
1220 bill ALL = ALL, !SU, !SHELLS
1222 Doesn't really prevent B<bill> from running the commands listed in
1223 I<SU> or I<SHELLS> since he can simply copy those commands to a
1224 different name, or use a shell escape from an editor or other
1225 program. Therefore, these kind of restrictions should be considered
1226 advisory at best (and reinforced by policy).
1228 =head1 PREVENTING SHELL ESCAPES
1230 Once B<sudo> executes a program, that program is free to do whatever
1231 it pleases, including run other programs. This can be a security
1232 issue since it is not uncommon for a program to allow shell escapes,
1233 which lets a user bypass B<sudo>'s access control and logging.
1234 Common programs that permit shell escapes include shells (obviously),
1235 editors, paginators, mail and terminal programs.
1237 There are two basic approaches to this problem:
1243 Avoid giving users access to commands that allow the user to run
1244 arbitrary commands. Many editors have a restricted mode where shell
1245 escapes are disabled, though B<sudoedit> is a better solution to
1246 running editors via B<sudo>. Due to the large number of programs that
1247 offer shell escapes, restricting users to the set of programs that
1248 do not if often unworkable.
1252 Many systems that support shared libraries have the ability to
1253 override default library functions by pointing an environment
1254 variable (usually C<LD_PRELOAD>) to an alternate shared library.
1255 On such systems, B<sudo>'s I<noexec> functionality can be used to
1256 prevent a program run by B<sudo> from executing any other programs.
1257 Note, however, that this applies only to native dynamically-linked
1258 executables. Statically-linked executables and foreign executables
1259 running under binary emulation are not affected.
1261 To tell whether or not B<sudo> supports I<noexec>, you can run
1262 the following as root:
1264 sudo -V | grep "dummy exec"
1266 If the resulting output contains a line that begins with:
1268 File containing dummy exec functions:
1270 then B<sudo> may be able to replace the exec family of functions
1271 in the standard library with its own that simply return an error.
1272 Unfortunately, there is no foolproof way to know whether or not
1273 I<noexec> will work at compile-time. I<noexec> should work on
1274 SunOS, Solaris, *BSD, Linux, IRIX, Tru64 UNIX, MacOS X, and HP-UX
1275 11.x. It is known B<not> to work on AIX and UnixWare. I<noexec>
1276 is expected to work on most operating systems that support the
1277 C<LD_PRELOAD> environment variable. Check your operating system's
1278 manual pages for the dynamic linker (usually ld.so, ld.so.1, dyld,
1279 dld.sl, rld, or loader) to see if C<LD_PRELOAD> is supported.
1281 To enable I<noexec> for a command, use the C<NOEXEC> tag as documented
1282 in the User Specification section above. Here is that example again:
1284 aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
1286 This allows user B<aaron> to run F</usr/bin/more> and F</usr/bin/vi>
1287 with I<noexec> enabled. This will prevent those two commands from
1288 executing other commands (such as a shell). If you are unsure
1289 whether or not your system is capable of supporting I<noexec> you
1290 can always just try it out and see if it works.
1294 Note that restricting shell escapes is not a panacea. Programs
1295 running as root are still capable of many potentially hazardous
1296 operations (such as changing or overwriting files) that could lead
1297 to unintended privilege escalation. In the specific case of an
1298 editor, a safer approach is to give the user permission to run
1303 L<rsh(1)>, L<su(1)>, L<fnmatch(3)>, L<sudo(8)>, L<visudo(8)>
1307 The I<sudoers> file should B<always> be edited by the B<visudo>
1308 command which locks the file and does grammatical checking. It is
1309 imperative that I<sudoers> be free of syntax errors since B<sudo>
1310 will not run with a syntactically incorrect I<sudoers> file.
1312 When using netgroups of machines (as opposed to users), if you
1313 store fully qualified hostnames in the netgroup (as is usually the
1314 case), you either need to have the machine's hostname be fully qualified
1315 as returned by the C<hostname> command or use the I<fqdn> option in
1320 If you feel you have found a bug in B<sudo>, please submit a bug report
1321 at http://www.sudo.ws/sudo/bugs/
1325 Limited free support is available via the sudo-users mailing list,
1326 see http://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or
1327 search the archives.
1331 B<sudo> is provided ``AS IS'' and any express or implied warranties,
1332 including, but not limited to, the implied warranties of merchantability
1333 and fitness for a particular purpose are disclaimed. See the LICENSE
1334 file distributed with B<sudo> or http://www.sudo.ws/sudo/license.html
1335 for complete details.