1 Copyright (c) 1994-1996, 1998-2005, 2007
2 Todd C. Miller <Todd.Miller@courtesan.com>
4 Permission to use, copy, modify, and distribute this software for any
5 purpose with or without fee is hereby granted, provided that the above
6 copyright notice and this permission notice appear in all copies.
8 THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9 WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10 MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11 ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13 ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14 OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15 ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
17 Sponsored in part by the Defense Advanced Research Projects
18 Agency (DARPA) and Air Force Research Laboratory, Air Force
19 Materiel Command, USAF, under agreement number F39502-99-1-0512.
21 $Sudo: sudoers.pod,v 1.95.2.26 2008/02/19 18:13:17 millert Exp $
26 sudoers - list of which users may execute what
30 The I<sudoers> file is composed of two types of entries: aliases
31 (basically variables) and user specifications (which specify who
34 When multiple entries match for a user, they are applied in order.
35 Where there are multiple matches, the last match is used (which is
36 not necessarily the most specific match).
38 The I<sudoers> grammar will be described below in Extended Backus-Naur
39 Form (EBNF). Don't despair if you don't know what EBNF is; it is
40 fairly simple, and the definitions below are annotated.
42 =head2 Quick guide to EBNF
44 EBNF is a concise and exact way of describing the grammar of a language.
45 Each EBNF definition is made up of I<production rules>. E.g.,
47 symbol ::= definition | alternate1 | alternate2 ...
49 Each I<production rule> references others and thus makes up a
50 grammar for the language. EBNF also contains the following
51 operators, which many readers will recognize from regular
52 expressions. Do not, however, confuse them with "wildcard"
53 characters, which have different meanings.
59 Means that the preceding symbol (or group of symbols) is optional.
60 That is, it may appear once or not at all.
64 Means that the preceding symbol (or group of symbols) may appear
69 Means that the preceding symbol (or group of symbols) may appear
74 Parentheses may be used to group symbols together. For clarity,
75 we will use single quotes ('') to designate what is a verbatim character
76 string (as opposed to a symbol name).
80 There are four kinds of aliases: C<User_Alias>, C<Runas_Alias>,
81 C<Host_Alias> and C<Cmnd_Alias>.
83 Alias ::= 'User_Alias' User_Alias (':' User_Alias)* |
84 'Runas_Alias' Runas_Alias (':' Runas_Alias)* |
85 'Host_Alias' Host_Alias (':' Host_Alias)* |
86 'Cmnd_Alias' Cmnd_Alias (':' Cmnd_Alias)*
88 User_Alias ::= NAME '=' User_List
90 Runas_Alias ::= NAME '=' Runas_List
92 Host_Alias ::= NAME '=' Host_List
94 Cmnd_Alias ::= NAME '=' Cmnd_List
96 NAME ::= [A-Z]([a-z][A-Z][0-9]_)*
98 Each I<alias> definition is of the form
100 Alias_Type NAME = item1, item2, ...
102 where I<Alias_Type> is one of C<User_Alias>, C<Runas_Alias>, C<Host_Alias>,
103 or C<Cmnd_Alias>. A C<NAME> is a string of uppercase letters, numbers,
104 and underscore characters ('_'). A C<NAME> B<must> start with an
105 uppercase letter. It is possible to put several alias definitions
106 of the same type on a single line, joined by a colon (':'). E.g.,
108 Alias_Type NAME = item1, item2, item3 : NAME = item4, item5
110 The definitions of what constitutes a valid I<alias> member follow.
115 User ::= '!'* username |
120 A C<User_List> is made up of one or more usernames, system groups
121 (prefixed with '%'), netgroups (prefixed with '+') and other aliases.
122 Each list item may be prefixed with one or more '!' operators.
123 An odd number of '!' operators negate the value of the item; an even
124 number just cancel each other out.
126 Runas_List ::= Runas_User |
127 Runas_User ',' Runas_List
129 Runas_User ::= '!'* username |
135 A C<Runas_List> is similar to a C<User_List> except that it can
136 also contain uids (prefixed with '#') and instead of C<User_Alias>es
137 it can contain C<Runas_Alias>es. Note that usernames and groups
138 are matched as strings. In other words, two users (groups) with
139 the same uid (gid) are considered to be distinct. If you wish to
140 match all usernames with the same uid (e.g.E<nbsp>root and toor), you
141 can use a uid instead (#0 in the example given).
146 Host ::= '!'* hostname |
148 '!'* network(/netmask)? |
152 A C<Host_List> is made up of one or more hostnames, IP addresses,
153 network numbers, netgroups (prefixed with '+') and other aliases.
154 Again, the value of an item may be negated with the '!' operator.
155 If you do not specify a netmask along with the network number,
156 B<sudo> will query each of the local host's network interfaces and,
157 if the network number corresponds to one of the hosts's network
158 interfaces, the corresponding netmask will be used. The netmask
159 may be specified either in standard IP address notation
160 (e.g.E<nbsp>255.255.255.0 or ffff:ffff:ffff:ffff::),
161 or CIDR notation (number of bits, e.g.E<nbsp>24 or 64). A hostname may
162 include shell-style wildcards (see the L<Wildcards> section below),
163 but unless the C<hostname> command on your machine returns the fully
164 qualified hostname, you'll need to use the I<fqdn> option for
165 wildcards to be useful.
170 commandname ::= filename |
174 Cmnd ::= '!'* commandname |
179 A C<Cmnd_List> is a list of one or more commandnames, directories, and other
180 aliases. A commandname is a fully qualified filename which may include
181 shell-style wildcards (see the L<Wildcards> section below). A simple
182 filename allows the user to run the command with any arguments he/she
183 wishes. However, you may also specify command line arguments (including
184 wildcards). Alternately, you can specify C<""> to indicate that the command
185 may only be run B<without> command line arguments. A directory is a
186 fully qualified pathname ending in a '/'. When you specify a directory
187 in a C<Cmnd_List>, the user will be able to run any file within that directory
188 (but not in any subdirectories therein).
190 If a C<Cmnd> has associated command line arguments, then the arguments
191 in the C<Cmnd> must match exactly those given by the user on the command line
192 (or match the wildcards if there are any). Note that the following
193 characters must be escaped with a '\' if they are used in command
194 arguments: ',', ':', '=', '\'. The special command C<"sudoedit">
195 is used to permit a user to run B<sudo> with the B<-e> flag (or
196 as B<sudoedit>). It may take command line arguments just as
197 a normal command does.
201 Certain configuration options may be changed from their default
202 values at runtime via one or more C<Default_Entry> lines. These
203 may affect all users on any host, all users on a specific host, a
204 specific user, or commands being run as a specific user.
206 Default_Type ::= 'Defaults' |
207 'Defaults' '@' Host_List |
208 'Defaults' ':' User_List |
209 'Defaults' '>' Runas_List
211 Default_Entry ::= Default_Type Parameter_List
213 Parameter_List ::= Parameter |
214 Parameter ',' Parameter_List
216 Parameter ::= Parameter '=' Value |
217 Parameter '+=' Value |
218 Parameter '-=' Value |
221 Parameters may be B<flags>, B<integer> values, B<strings>, or B<lists>.
222 Flags are implicitly boolean and can be turned off via the '!'
223 operator. Some integer, string and list parameters may also be
224 used in a boolean context to disable them. Values may be enclosed
225 in double quotes (C<">) when they contain multiple words. Special
226 characters may be escaped with a backslash (C<\>).
228 Lists have two additional assignment operators, C<+=> and C<-=>.
229 These operators are used to add to and delete from a list respectively.
230 It is not an error to use the C<-=> operator to remove an element
231 that does not exist in a list.
233 See L</"SUDOERS OPTIONS"> for a list of supported Defaults parameters.
235 =head2 User Specification
237 User_Spec ::= User_List Host_List '=' Cmnd_Spec_List \
238 (':' Host_List '=' Cmnd_Spec_List)*
240 Cmnd_Spec_List ::= Cmnd_Spec |
241 Cmnd_Spec ',' Cmnd_Spec_List
243 Cmnd_Spec ::= Runas_Spec? Tag_Spec* Cmnd
245 Runas_Spec ::= '(' Runas_List ')'
247 Tag_Spec ::= ('NOPASSWD:' | 'PASSWD:' | 'NOEXEC:' | 'EXEC:' |
248 'SETENV:' | 'NOSETENV:')
250 A B<user specification> determines which commands a user may run
251 (and as what user) on specified hosts. By default, commands are
252 run as B<root>, but this can be changed on a per-command basis.
254 Let's break that down into its constituent parts:
258 A C<Runas_Spec> is simply a C<Runas_List> (as defined above)
259 enclosed in a set of parentheses. If you do not specify a
260 C<Runas_Spec> in the user specification, a default C<Runas_Spec>
261 of B<root> will be used. A C<Runas_Spec> sets the default for
262 commands that follow it. What this means is that for the entry:
264 dgb boulder = (operator) /bin/ls, /bin/kill, /usr/bin/lprm
266 The user B<dgb> may run F</bin/ls>, F</bin/kill>, and
267 F</usr/bin/lprm> -- but only as B<operator>. E.g.,
269 $ sudo -u operator /bin/ls.
271 It is also possible to override a C<Runas_Spec> later on in an
272 entry. If we modify the entry like so:
274 dgb boulder = (operator) /bin/ls, (root) /bin/kill, /usr/bin/lprm
276 Then user B<dgb> is now allowed to run F</bin/ls> as B<operator>,
277 but F</bin/kill> and F</usr/bin/lprm> as B<root>.
281 A command may have zero or more tags associated with it. There are
282 six possible tag values, C<NOPASSWD>, C<PASSWD>, C<NOEXEC>, C<EXEC>,
283 C<SETENV> and C<NOSETENV>.
284 Once a tag is set on a C<Cmnd>, subsequent C<Cmnd>s in the
285 C<Cmnd_Spec_List>, inherit the tag unless it is overridden by the
286 opposite tag (i.e.: C<PASSWD> overrides C<NOPASSWD> and C<NOEXEC>
289 =head3 NOPASSWD and PASSWD
291 By default, B<sudo> requires that a user authenticate him or herself
292 before running a command. This behavior can be modified via the
293 C<NOPASSWD> tag. Like a C<Runas_Spec>, the C<NOPASSWD> tag sets
294 a default for the commands that follow it in the C<Cmnd_Spec_List>.
295 Conversely, the C<PASSWD> tag can be used to reverse things.
298 ray rushmore = NOPASSWD: /bin/kill, /bin/ls, /usr/bin/lprm
300 would allow the user B<ray> to run F</bin/kill>, F</bin/ls>, and
301 F</usr/bin/lprm> as root on the machine rushmore as B<root> without
302 authenticating himself. If we only want B<ray> to be able to
303 run F</bin/kill> without a password the entry would be:
305 ray rushmore = NOPASSWD: /bin/kill, PASSWD: /bin/ls, /usr/bin/lprm
307 Note, however, that the C<PASSWD> tag has no effect on users who are
308 in the group specified by the I<exempt_group> option.
310 By default, if the C<NOPASSWD> tag is applied to any of the entries
311 for a user on the current host, he or she will be able to run
312 C<sudo -l> without a password. Additionally, a user may only run
313 C<sudo -v> without a password if the C<NOPASSWD> tag is present
314 for all a user's entries that pertain to the current host.
315 This behavior may be overridden via the verifypw and listpw options.
317 =head3 NOEXEC and EXEC
319 If B<sudo> has been compiled with I<noexec> support and the underlying
320 operating system supports it, the C<NOEXEC> tag can be used to prevent
321 a dynamically-linked executable from running further commands itself.
323 In the following example, user B<aaron> may run F</usr/bin/more>
324 and F</usr/bin/vi> but shell escapes will be disabled.
326 aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
328 See the L<PREVENTING SHELL ESCAPES> section below for more details
329 on how C<NOEXEC> works and whether or not it will work on your system.
331 =head3 SETENV and NOSETENV
333 These tags override the value of the I<setenv> option on a per-command
334 basis. Note that if C<SETENV> has been set for a command, any
335 environment variables set on the command line way are not subject
336 to the restrictions imposed by I<env_check>, I<env_delete>, or
337 I<env_keep>. As such, only trusted users should be allowed to set
338 variables in this manner. If the command matched is B<ALL>, the
339 C<SETENV> tag is implied for that command; this default may
340 be overridden by use of the C<UNSETENV> tag.
344 B<sudo> allows shell-style I<wildcards> (aka meta or glob characters)
345 to be used in pathnames as well as command line arguments in the
346 I<sudoers> file. Wildcard matching is done via the B<POSIX>
347 L<fnmatch(3)> routine. Note that these are I<not> regular expressions.
353 Matches any set of zero or more characters.
357 Matches any single character.
361 Matches any character in the specified range.
365 Matches any character B<not> in the specified range.
369 For any character "x", evaluates to "x". This is used to
370 escape special characters such as: "*", "?", "[", and "}".
374 Note that a forward slash ('/') will B<not> be matched by
375 wildcards used in the pathname. When matching the command
376 line arguments, however, a slash B<does> get matched by
377 wildcards. This is to make a path like:
381 match F</usr/bin/who> but not F</usr/bin/X11/xterm>.
383 =head2 Exceptions to wildcard rules
385 The following exceptions apply to the above rules:
391 If the empty string C<""> is the only command line argument in the
392 I<sudoers> entry it means that command is not allowed to be run
393 with B<any> arguments.
397 =head2 Other special characters and reserved words
399 The pound sign ('#') is used to indicate a comment (unless it is
400 part of a #include directive or unless it occurs in the context of
401 a user name and is followed by one or more digits, in which case
402 it is treated as a uid). Both the comment character and any text
403 after it, up to the end of the line, are ignored.
405 The reserved word B<ALL> is a built-in I<alias> that always causes
406 a match to succeed. It can be used wherever one might otherwise
407 use a C<Cmnd_Alias>, C<User_Alias>, C<Runas_Alias>, or C<Host_Alias>.
408 You should not try to define your own I<alias> called B<ALL> as the
409 built-in alias will be used in preference to your own. Please note
410 that using B<ALL> can be dangerous since in a command context, it
411 allows the user to run B<any> command on the system.
413 An exclamation point ('!') can be used as a logical I<not> operator
414 both in an I<alias> and in front of a C<Cmnd>. This allows one to
415 exclude certain values. Note, however, that using a C<!> in
416 conjunction with the built-in C<ALL> alias to allow a user to
417 run "all but a few" commands rarely works as intended (see SECURITY
420 Long lines can be continued with a backslash ('\') as the last
421 character on the line.
423 Whitespace between elements in a list as well as special syntactic
424 characters in a I<User Specification> ('=', ':', '(', ')') is optional.
426 The following characters must be escaped with a backslash ('\') when
427 used as part of a word (e.g.E<nbsp>a username or hostname):
428 '@', '!', '=', ':', ',', '(', ')', '\'.
430 =head1 SUDOERS OPTIONS
432 B<sudo>'s behavior can be modified by C<Default_Entry> lines, as
433 explained earlier. A list of all supported Defaults parameters,
434 grouped by type, are listed below.
442 Send mail to the I<mailto> user if the user running B<sudo> does not
443 enter the correct password. This flag is I<off> by default.
447 If set, mail will be sent to the I<mailto> user if the invoking
448 user exists in the I<sudoers> file, but is not allowed to run
449 commands on the current host. This flag is I<@mail_no_host@> by default.
453 If set, mail will be sent to the I<mailto> user if the invoking
454 user is allowed to use B<sudo> but the command they are trying is not
455 listed in their I<sudoers> file entry or is explicitly denied.
456 This flag is I<@mail_no_perms@> by default.
460 If set, mail will be sent to the I<mailto> user if the invoking
461 user is not in the I<sudoers> file. This flag is I<@mail_no_user@>
466 If set, all commands run via B<sudo> will behave as if the C<NOEXEC>
467 tag has been set, unless overridden by a C<EXEC> tag. See the
468 description of I<NOEXEC and EXEC> below as well as the L<PREVENTING SHELL
469 ESCAPES> section at the end of this manual. This flag is I<off> by default.
473 If set, users must authenticate themselves via a password (or other
474 means of authentication) before they may run commands. This default
475 may be overridden via the C<PASSWD> and C<NOPASSWD> tags.
476 This flag is I<on> by default.
480 If set, B<visudo> will use the value of the EDITOR or VISUAL
481 environment variables before falling back on the default editor list.
482 Note that this may create a security hole as it allows the user to
483 run any arbitrary command as root without logging. A safer alternative
484 is to place a colon-separated list of editors in the C<editor>
485 variable. B<visudo> will then only use the EDITOR or VISUAL if
486 they match a value specified in C<editor>. This flag is I<@env_editor@> by
491 If set, B<sudo> will reset the environment to only contain the
492 LOGNAME, SHELL, USER, USERNAME and the C<SUDO_*> variables. Any
493 variables in the caller's environment that match the C<env_keep>
494 and C<env_check> lists are then added. The default contents of the
495 C<env_keep> and C<env_check> lists are displayed when B<sudo> is
496 run by root with the I<-V> option. If B<sudo> was compiled with
497 the C<SECURE_PATH> option, its value will be used for the C<PATH>
498 environment variable. This flag is I<on> by default.
502 Set this flag if you want to put fully qualified hostnames in the
503 I<sudoers> file. I.e., instead of myhost you would use myhost.mydomain.edu.
504 You may still use the short form if you wish (and even mix the two).
505 Beware that turning on I<fqdn> requires B<sudo> to make DNS lookups
506 which may make B<sudo> unusable if DNS stops working (for example
507 if the machine is not plugged into the network). Also note that
508 you must use the host's official name as DNS knows it. That is,
509 you may not use a host alias (C<CNAME> entry) due to performance
510 issues and the fact that there is no way to get all aliases from
511 DNS. If your machine's hostname (as returned by the C<hostname>
512 command) is already fully qualified you shouldn't need to set
513 I<fqdn>. This flag is I<@fqdn@> by default.
517 If set, B<sudo> will ignore '.' or '' (current dir) in the C<PATH>
518 environment variable; the C<PATH> itself is not modified. This
519 flag is I<@ignore_dot@> by default. Currently, while it is possible
520 to set I<ignore_dot> in I<sudoers>, its value is not used. This option
521 should be considered read-only (it will be fixed in a future version
524 =item ignore_local_sudoers
526 If set via LDAP, parsing of F<@sysconfdir@/sudoers> will be skipped.
527 This is intended for Enterprises that wish to prevent the usage of local
528 sudoers files so that only LDAP is used. This thwarts the efforts of
529 rogue operators who would attempt to add roles to F<@sysconfdir@/sudoers>.
530 When this option is present, F<@sysconfdir@/sudoers> does not even need to
531 exist. Since this option tells B<sudo> how to behave when no specific LDAP
532 entries have been matched, this sudoOption is only meaningful for the
533 C<cn=defaults> section. This flag is I<off> by default.
537 If set, B<sudo> will insult users when they enter an incorrect
538 password. This flag is I<@insults@> by default.
542 If set, the hostname will be logged in the (non-syslog) B<sudo> log file.
543 This flag is I<off> by default.
547 If set, the four-digit year will be logged in the (non-syslog) B<sudo> log file.
548 This flag is I<off> by default.
550 =item long_otp_prompt
552 When validating with a One Time Password (OPT) scheme such as
553 B<S/Key> or B<OPIE>, a two-line prompt is used to make it easier
554 to cut and paste the challenge to a local window. It's not as
555 pretty as the default but some people find it more convenient. This
556 flag is I<@long_otp_prompt@> by default.
560 Send mail to the I<mailto> user every time a users runs B<sudo>.
561 This flag is I<off> by default.
565 Send mail to the I<mailto> user if the user running B<sudo> does not
566 enter the correct password. This flag is I<off> by default.
570 If set, mail will be sent to the I<mailto> user if the invoking
571 user exists in the I<sudoers> file, but is not allowed to run
572 commands on the current host. This flag is I<@mail_no_host@> by default.
576 If set, mail will be sent to the I<mailto> user if the invoking
577 user is allowed to use B<sudo> but the command they are trying is not
578 listed in their I<sudoers> file entry or is explicitly denied.
579 This flag is I<@mail_no_perms@> by default.
583 If set, mail will be sent to the I<mailto> user if the invoking
584 user is not in the I<sudoers> file. This flag is I<@mail_no_user@>
589 If set, all commands run via B<sudo> will behave as if the C<NOEXEC>
590 tag has been set, unless overridden by a C<EXEC> tag. See the
591 description of I<NOEXEC and EXEC> below as well as the L<PREVENTING SHELL
592 ESCAPES> section at the end of this manual. This flag is I<off> by default.
596 Normally, B<sudo> will tell the user when a command could not be
597 found in their C<PATH> environment variable. Some sites may wish
598 to disable this as it could be used to gather information on the
599 location of executables that the normal user does not have access
600 to. The disadvantage is that if the executable is simply not in
601 the user's C<PATH>, B<sudo> will tell the user that they are not
602 allowed to run it, which can be confusing. This flag is I<@path_info@>
605 =item passprompt_override
607 The password prompt specified by I<passprompt> will normally only
608 be used if the passwod prompt provided by systems such as PAM matches
609 the string "Password:". If I<passprompt_override> is set, I<passprompt>
610 will always be used. This flag is I<off> by default.
612 =item preserve_groups
614 By default B<sudo> will initialize the group vector to the list of
615 groups the target user is in. When I<preserve_groups> is set, the
616 user's existing group vector is left unaltered. The real and
617 effective group IDs, however, are still set to match the target
618 user. This flag is I<off> by default.
622 If set, B<sudo> will only run when the user is logged in to a real
623 tty. This will disallow things like C<"rsh somehost sudo ls"> since
624 L<rsh(1)> does not allocate a tty. Because it is not possible to turn
625 off echo when there is no tty present, some sites may wish to set
626 this flag to prevent a user from entering a visible password. This
627 flag is I<off> by default.
631 If set, root is allowed to run B<sudo> too. Disabling this prevents users
632 from "chaining" B<sudo> commands to get a root shell by doing something
633 like C<"sudo sudo /bin/sh">. Note, however, that turning off I<root_sudo>
634 will also prevent root and from running B<sudoedit>.
635 Disabling I<root_sudo> provides no real additional security; it
636 exists purely for historical reasons.
637 This flag is I<@root_sudo@> by default.
641 If set, B<sudo> will prompt for the root password instead of the password
642 of the invoking user. This flag is I<off> by default.
646 If set, B<sudo> will prompt for the password of the user defined by the
647 I<runas_default> option (defaults to C<@runas_default@>) instead of the
648 password of the invoking user. This flag is I<off> by default.
652 If set and B<sudo> is invoked with the B<-s> flag the C<HOME>
653 environment variable will be set to the home directory of the target
654 user (which is root unless the B<-u> option is used). This effectively
655 makes the B<-s> flag imply B<-H>. This flag is I<off> by default.
659 Normally, B<sudo> will set the C<LOGNAME>, C<USER> and C<USERNAME>
660 environment variables to the name of the target user (usually root
661 unless the B<-u> flag is given). However, since some programs
662 (including the RCS revision control system) use C<LOGNAME> to
663 determine the real identity of the user, it may be desirable to
664 change this behavior. This can be done by negating the set_logname
665 option. Note that if the I<env_reset> option has not been disabled,
666 entries in the I<env_keep> list will override the value of
667 I<set_logname>. This flag is I<off> by default.
671 Allow the user to disable the I<env_reset> option from the command
672 line. Additionally, environment variables set via the command line
673 are not subject to the restrictions imposed by I<env_check>,
674 I<env_delete>, or I<env_keep>. As such, only trusted users should
675 be allowed to set variables in this manner. This flag is I<off>
680 If set and B<sudo> is invoked with no arguments it acts as if the
681 B<-s> flag had been given. That is, it runs a shell as root (the
682 shell is determined by the C<SHELL> environment variable if it is
683 set, falling back on the shell listed in the invoking user's
684 /etc/passwd entry if not). This flag is I<off> by default.
688 Normally, when B<sudo> executes a command the real and effective
689 UIDs are set to the target user (root by default). This option
690 changes that behavior such that the real UID is left as the invoking
691 user's UID. In other words, this makes B<sudo> act as a setuid
692 wrapper. This can be useful on systems that disable some potentially
693 dangerous functionality when a program is run setuid. This option
694 is only effective on systems with either the setreuid() or setresuid()
695 function. This flag is I<off> by default.
699 If set, B<sudo> will prompt for the password of the user specified by
700 the B<-u> flag (defaults to C<root>) instead of the password of the
701 invoking user. Note that this precludes the use of a uid not listed
702 in the passwd database as an argument to the B<-u> flag.
703 This flag is I<off> by default.
707 If set, users must authenticate on a per-tty basis. Normally,
708 B<sudo> uses a directory in the ticket dir with the same name as
709 the user running it. With this flag enabled, B<sudo> will use a
710 file named for the tty the user is logged in on in that directory.
711 This flag is I<@tty_tickets@> by default.
715 If set, B<sudo> will apply the defaults specified for the target user's
716 login class if one exists. Only available if B<sudo> is configured with
717 the --with-logincap option. This flag is I<off> by default.
727 The number of tries a user gets to enter his/her password before
728 B<sudo> logs the failure and exits. The default is C<@passwd_tries@>.
732 B<Integers that can be used in a boolean context>:
738 Number of characters per line for the file log. This value is used
739 to decide when to wrap lines for nicer log files. This has no
740 effect on the syslog log file, only the file log. The default is
741 C<@loglen@> (use 0 or negate the option to disable word wrap).
745 Number of minutes before the B<sudo> password prompt times out.
746 The default is C<@password_timeout@>; set this to C<0> for no password timeout.
748 =item timestamp_timeout
750 Number of minutes that can elapse before B<sudo> will ask for a
751 passwd again. The default is C<@timeout@>. Set this to C<0> to always
752 prompt for a password.
753 If set to a value less than C<0> the user's timestamp will never
754 expire. This can be used to allow users to create or delete their
755 own timestamps via C<sudo -v> and C<sudo -k> respectively.
759 Umask to use when running the command. Negate this option or set
760 it to 0777 to preserve the user's umask. The default is C<@sudo_umask@>.
768 =item badpass_message
770 Message that is displayed if a user enters an incorrect password.
771 The default is C<@badpass_message@> unless insults are enabled.
775 A colon (':') separated list of editors allowed to be used with
776 B<visudo>. B<visudo> will choose the editor that matches the user's
777 EDITOR environment variable if possible, or the first editor in the
778 list that exists and is executable. The default is the path to vi
783 Subject of the mail sent to the I<mailto> user. The escape C<%h>
784 will expand to the hostname of the machine.
785 Default is C<@mailsub@>.
789 Path to a shared library containing dummy versions of the execv(),
790 execve() and fexecve() library functions that just return an error.
791 This is used to implement the I<noexec> functionality on systems that
792 support C<LD_PRELOAD> or its equivalent. Defaults to F<@noexec_file@>.
796 The default prompt to use when asking for a password; can be overridden
797 via the B<-p> option or the C<SUDO_PROMPT> environment variable.
798 The following percent (`C<%>') escapes are supported:
804 expanded to the local hostname including the domain name
805 (on if the machine's hostname is fully qualified or the I<fqdn>
810 expanded to the local hostname without the domain name
814 expanded to the user whose password is being asked for (respects the
815 I<rootpw>, I<targetpw> and I<runaspw> flags in I<sudoers>)
819 expanded to the login name of the user the command will
820 be run as (defaults to root)
824 expanded to the invoking user's login name
828 two consecutive C<%> characters are collapsed into a single C<%> character
832 The default value is C<@passprompt@>.
836 The default SELinux role to use when constructing a new security
837 context to run the command. The default role may be overridden on
838 a per-command basis in I<sudoers> or via command line options.
839 This option is only available whe B<sudo> is built with SELinux support.
843 The default user to run commands as if the B<-u> flag is not specified
844 on the command line. This defaults to C<@runas_default@>.
845 Note that if I<runas_default> is set it B<must> occur before
846 any C<Runas_Alias> specifications.
850 Syslog priority to use when user authenticates unsuccessfully.
851 Defaults to C<@badpri@>.
855 Syslog priority to use when user authenticates successfully.
856 Defaults to C<@goodpri@>.
860 The directory in which B<sudo> stores its timestamp files.
861 The default is F<@timedir@>.
865 The owner of the timestamp directory and the timestamps stored therein.
866 The default is C<root>.
870 The default SELinux type to use when constructing a new security
871 context to run the command. The default type may be overridden on
872 a per-command basis in I<sudoers> or via command line options.
873 This option is only available whe B<sudo> is built with SELinux support.
877 B<Strings that can be used in a boolean context>:
883 Users in this group are exempt from password and PATH requirements.
884 This is not set by default.
888 This option controls when a short lecture will be printed along with
889 the password prompt. It has the following possible values:
895 Always lecture the user.
899 Never lecture the user.
903 Only lecture the user the first time they run B<sudo>.
907 If no value is specified, a value of I<once> is implied.
908 Negating the option results in a value of I<never> being used.
909 The default value is I<@lecture@>.
913 Path to a file containing an alternate B<sudo> lecture that will
914 be used in place of the standard lecture if the named file exists.
915 By default, B<sudo> uses a built-in lecture.
919 This option controls when a password will be required when a
920 user runs B<sudo> with the B<-l> flag. It has the following possible values:
926 All the user's I<sudoers> entries for the current host must have
927 the C<NOPASSWD> flag set to avoid entering a password.
931 The user must always enter a password to use the B<-l> flag.
935 At least one of the user's I<sudoers> entries for the current host
936 must have the C<NOPASSWD> flag set to avoid entering a password.
940 The user need never enter a password to use the B<-l> flag.
944 If no value is specified, a value of I<any> is implied.
945 Negating the option results in a value of I<never> being used.
946 The default value is I<any>.
950 Path to the B<sudo> log file (not the syslog log file). Setting a path
951 turns on logging to a file; negating this option turns it off.
952 By default, B<sudo> logs via syslog.
956 Flags to use when invoking mailer. Defaults to B<-t>.
960 Path to mail program used to send warning mail.
961 Defaults to the path to sendmail found at configure time.
965 Address to send warning and error mail to. The address should
966 be enclosed in double quotes (C<">) to protect against B<sudo>
967 interpreting the C<@> sign. Defaults to C<@mailto@>.
971 Syslog facility if syslog is being used for logging (negate to
972 disable syslog logging). Defaults to C<@logfac@>.
976 This option controls when a password will be required when a user runs
977 B<sudo> with the B<-v> flag. It has the following possible values:
983 All the user's I<sudoers> entries for the current host must have
984 the C<NOPASSWD> flag set to avoid entering a password.
988 The user must always enter a password to use the B<-v> flag.
992 At least one of the user's I<sudoers> entries for the current host
993 must have the C<NOPASSWD> flag set to avoid entering a password.
997 The user need never enter a password to use the B<-v> flag.
1001 If no value is specified, a value of I<all> is implied.
1002 Negating the option results in a value of I<never> being used.
1003 The default value is I<all>.
1007 B<Lists that can be used in a boolean context>:
1013 Environment variables to be removed from the user's environment if
1014 the variable's value contains C<%> or C</> characters. This can
1015 be used to guard against printf-style format vulnerabilities in
1016 poorly-written programs. The argument may be a double-quoted,
1017 space-separated list or a single value without double-quotes. The
1018 list can be replaced, added to, deleted from, or disabled by using
1019 the C<=>, C<+=>, C<-=>, and C<!> operators respectively. Regardless
1020 of whether the C<env_reset> option is enabled or disabled, variables
1021 specified by C<env_check> will be preserved in the environment if
1022 they pass the aforementioned check. The default list of environment
1023 variables to check is displayed when B<sudo> is run by root with
1029 Not effective due to security issues: only variables listed in
1030 I<env_keep> or I<env_check> can be passed through B<sudo>!
1032 The argument may be a double-quoted, space-separated list or a
1033 single value without double-quotes. The list can be replaced, added
1034 to, deleted from, or disabled by using the C<=>, C<+=>, C<-=>, and
1035 C<!> operators respectively. The default list of environment
1036 variables to remove is displayed when B<sudo> is run by root with the
1037 I<-V> option. Note that many operating systems will remove potentially
1038 dangerous variables from the environment of any setuid process (such
1043 Environment variables to be preserved in the user's environment.
1044 This allows fine-grained
1045 control over the environment B<sudo>-spawned processes will receive.
1046 The argument may be a double-quoted, space-separated list or a
1047 single value without double-quotes. The list can be replaced, added
1048 to, deleted from, or disabled by using the C<=>, C<+=>, C<-=>, and
1049 C<!> operators respectively. The default list of variables to keep
1050 is displayed when B<sudo> is run by root with the I<-V> option.
1054 When logging via L<syslog(3)>, B<sudo> accepts the following values
1055 for the syslog facility (the value of the B<syslog> Parameter):
1056 B<authpriv> (if your OS supports it), B<auth>, B<daemon>, B<user>,
1057 B<local0>, B<local1>, B<local2>, B<local3>, B<local4>, B<local5>,
1058 B<local6>, and B<local7>. The following syslog priorities are
1059 supported: B<alert>, B<crit>, B<debug>, B<emerg>, B<err>, B<info>,
1060 B<notice>, and B<warning>.
1066 =item F<@sysconfdir@/sudoers>
1068 List of who can run what
1074 =item F</etc/netgroup>
1076 List of network groups
1082 Since the I<sudoers> file is parsed in a single pass, order is
1083 important. In general, you should structure I<sudoers> such that
1084 the C<Host_Alias>, C<User_Alias>, and C<Cmnd_Alias> specifications
1085 come first, followed by any C<Default_Entry> lines, and finally the
1086 C<Runas_Alias> and user specifications. The basic rule of thumb
1087 is you cannot reference an Alias that has not already been defined.
1089 Below are example I<sudoers> entries. Admittedly, some of
1090 these are a bit contrived. First, we define our I<aliases>:
1092 Below are example I<sudoers> entries. Admittedly, some of
1093 these are a bit contrived. First, we allow a few environment
1094 variables to pass and then define our I<aliases>:
1096 # Run X applications through sudo; HOME is used to find .Xauthority file
1097 # Note that some programs may use HOME for other purposes too and
1098 # this may lead to privilege escalation!
1099 Defaults env_keep = "DISPLAY HOME"
1101 # User alias specification
1102 User_Alias FULLTIMERS = millert, mikef, dowdy
1103 User_Alias PARTTIMERS = bostley, jwfox, crawl
1104 User_Alias WEBMASTERS = will, wendy, wim
1106 # Runas alias specification
1107 Runas_Alias OP = root, operator
1108 Runas_Alias DB = oracle, sybase
1110 # Host alias specification
1111 Host_Alias SPARC = bigtime, eclipse, moet, anchor :\
1112 SGI = grolsch, dandelion, black :\
1113 ALPHA = widget, thalamus, foobar :\
1114 HPPA = boa, nag, python
1115 Host_Alias CUNETS = 128.138.0.0/255.255.0.0
1116 Host_Alias CSNETS = 128.138.243.0, 128.138.204.0/24, 128.138.242.0
1117 Host_Alias SERVERS = master, mail, www, ns
1118 Host_Alias CDROM = orion, perseus, hercules
1120 # Cmnd alias specification
1121 Cmnd_Alias DUMPS = /usr/bin/mt, /usr/sbin/dump, /usr/sbin/rdump,\
1122 /usr/sbin/restore, /usr/sbin/rrestore
1123 Cmnd_Alias KILL = /usr/bin/kill
1124 Cmnd_Alias PRINTING = /usr/sbin/lpc, /usr/bin/lprm
1125 Cmnd_Alias SHUTDOWN = /usr/sbin/shutdown
1126 Cmnd_Alias HALT = /usr/sbin/halt
1127 Cmnd_Alias REBOOT = /usr/sbin/reboot
1128 Cmnd_Alias SHELLS = /usr/bin/sh, /usr/bin/csh, /usr/bin/ksh, \
1129 /usr/local/bin/tcsh, /usr/bin/rsh, \
1131 Cmnd_Alias SU = /usr/bin/su
1132 Cmnd_Alias PAGERS = /usr/bin/more, /usr/bin/pg, /usr/bin/less
1134 Here we override some of the compiled in default values. We want
1135 B<sudo> to log via L<syslog(3)> using the I<auth> facility in all
1136 cases. We don't want to subject the full time staff to the B<sudo>
1137 lecture, user B<millert> need not give a password, and we don't
1138 want to reset the C<LOGNAME>, C<USER> or C<USERNAME> environment
1139 variables when running commands as root. Additionally, on the
1140 machines in the I<SERVERS> C<Host_Alias>, we keep an additional
1141 local log file and make sure we log the year in each log line since
1142 the log entries will be kept around for several years. Lastly, we
1143 disable shell escapes for the commands in the PAGERS C<Cmnd_Alias>
1144 (F</usr/bin/more>, F</usr/bin/pg> and F</usr/bin/less>).
1146 # Override built-in defaults
1147 Defaults syslog=auth
1148 Defaults>root !set_logname
1149 Defaults:FULLTIMERS !lecture
1150 Defaults:millert !authenticate
1151 Defaults@SERVERS log_year, logfile=/var/log/sudo.log
1152 Defaults!PAGERS noexec
1154 The I<User specification> is the part that actually determines who may
1157 root ALL = (ALL) ALL
1158 %wheel ALL = (ALL) ALL
1160 We let B<root> and any user in group B<wheel> run any command on any
1163 FULLTIMERS ALL = NOPASSWD: ALL
1165 Full time sysadmins (B<millert>, B<mikef>, and B<dowdy>) may run any
1166 command on any host without authenticating themselves.
1168 PARTTIMERS ALL = ALL
1170 Part time sysadmins (B<bostley>, B<jwfox>, and B<crawl>) may run any
1171 command on any host but they must authenticate themselves first
1172 (since the entry lacks the C<NOPASSWD> tag).
1176 The user B<jack> may run any command on the machines in the I<CSNETS> alias
1177 (the networks C<128.138.243.0>, C<128.138.204.0>, and C<128.138.242.0>).
1178 Of those networks, only C<128.138.204.0> has an explicit netmask (in
1179 CIDR notation) indicating it is a class C network. For the other
1180 networks in I<CSNETS>, the local machine's netmask will be used
1185 The user B<lisa> may run any command on any host in the I<CUNETS> alias
1186 (the class B network C<128.138.0.0>).
1188 operator ALL = DUMPS, KILL, SHUTDOWN, HALT, REBOOT, PRINTING,\
1189 sudoedit /etc/printcap, /usr/oper/bin/
1191 The B<operator> user may run commands limited to simple maintenance.
1192 Here, those are commands related to backups, killing processes, the
1193 printing system, shutting down the system, and any commands in the
1194 directory F</usr/oper/bin/>.
1196 joe ALL = /usr/bin/su operator
1198 The user B<joe> may only L<su(1)> to operator.
1200 pete HPPA = /usr/bin/passwd [A-z]*, !/usr/bin/passwd root
1202 The user B<pete> is allowed to change anyone's password except for
1203 root on the I<HPPA> machines. Note that this assumes L<passwd(1)>
1204 does not take multiple usernames on the command line.
1206 bob SPARC = (OP) ALL : SGI = (OP) ALL
1208 The user B<bob> may run anything on the I<SPARC> and I<SGI> machines
1209 as any user listed in the I<OP> C<Runas_Alias> (B<root> and B<operator>).
1213 The user B<jim> may run any command on machines in the I<biglab> netgroup.
1214 B<sudo> knows that "biglab" is a netgroup due to the '+' prefix.
1216 +secretaries ALL = PRINTING, /usr/bin/adduser, /usr/bin/rmuser
1218 Users in the B<secretaries> netgroup need to help manage the printers
1219 as well as add and remove users, so they are allowed to run those
1220 commands on all machines.
1222 fred ALL = (DB) NOPASSWD: ALL
1224 The user B<fred> can run commands as any user in the I<DB> C<Runas_Alias>
1225 (B<oracle> or B<sybase>) without giving a password.
1227 john ALPHA = /usr/bin/su [!-]*, !/usr/bin/su *root*
1229 On the I<ALPHA> machines, user B<john> may su to anyone except root
1230 but he is not allowed to give L<su(1)> any flags.
1232 jen ALL, !SERVERS = ALL
1234 The user B<jen> may run any command on any machine except for those
1235 in the I<SERVERS> C<Host_Alias> (master, mail, www and ns).
1237 jill SERVERS = /usr/bin/, !SU, !SHELLS
1239 For any machine in the I<SERVERS> C<Host_Alias>, B<jill> may run
1240 any commands in the directory F</usr/bin/> except for those commands
1241 belonging to the I<SU> and I<SHELLS> C<Cmnd_Aliases>.
1243 steve CSNETS = (operator) /usr/local/op_commands/
1245 The user B<steve> may run any command in the directory /usr/local/op_commands/
1246 but only as user operator.
1248 matt valkyrie = KILL
1250 On his personal workstation, valkyrie, B<matt> needs to be able to
1251 kill hung processes.
1253 WEBMASTERS www = (www) ALL, (root) /usr/bin/su www
1255 On the host www, any user in the I<WEBMASTERS> C<User_Alias> (will,
1256 wendy, and wim), may run any command as user www (which owns the
1257 web pages) or simply L<su(1)> to www.
1259 ALL CDROM = NOPASSWD: /sbin/umount /CDROM,\
1260 /sbin/mount -o nosuid\,nodev /dev/cd0a /CDROM
1262 Any user may mount or unmount a CD-ROM on the machines in the CDROM
1263 C<Host_Alias> (orion, perseus, hercules) without entering a password.
1264 This is a bit tedious for users to type, so it is a prime candidate
1265 for encapsulating in a shell script.
1267 =head1 SECURITY NOTES
1269 It is generally not effective to "subtract" commands from C<ALL>
1270 using the '!' operator. A user can trivially circumvent this
1271 by copying the desired command to a different name and then
1272 executing that. For example:
1274 bill ALL = ALL, !SU, !SHELLS
1276 Doesn't really prevent B<bill> from running the commands listed in
1277 I<SU> or I<SHELLS> since he can simply copy those commands to a
1278 different name, or use a shell escape from an editor or other
1279 program. Therefore, these kind of restrictions should be considered
1280 advisory at best (and reinforced by policy).
1282 =head1 PREVENTING SHELL ESCAPES
1284 Once B<sudo> executes a program, that program is free to do whatever
1285 it pleases, including run other programs. This can be a security
1286 issue since it is not uncommon for a program to allow shell escapes,
1287 which lets a user bypass B<sudo>'s access control and logging.
1288 Common programs that permit shell escapes include shells (obviously),
1289 editors, paginators, mail and terminal programs.
1291 There are two basic approaches to this problem:
1297 Avoid giving users access to commands that allow the user to run
1298 arbitrary commands. Many editors have a restricted mode where shell
1299 escapes are disabled, though B<sudoedit> is a better solution to
1300 running editors via B<sudo>. Due to the large number of programs that
1301 offer shell escapes, restricting users to the set of programs that
1302 do not if often unworkable.
1306 Many systems that support shared libraries have the ability to
1307 override default library functions by pointing an environment
1308 variable (usually C<LD_PRELOAD>) to an alternate shared library.
1309 On such systems, B<sudo>'s I<noexec> functionality can be used to
1310 prevent a program run by B<sudo> from executing any other programs.
1311 Note, however, that this applies only to native dynamically-linked
1312 executables. Statically-linked executables and foreign executables
1313 running under binary emulation are not affected.
1315 To tell whether or not B<sudo> supports I<noexec>, you can run
1316 the following as root:
1318 sudo -V | grep "dummy exec"
1320 If the resulting output contains a line that begins with:
1322 File containing dummy exec functions:
1324 then B<sudo> may be able to replace the exec family of functions
1325 in the standard library with its own that simply return an error.
1326 Unfortunately, there is no foolproof way to know whether or not
1327 I<noexec> will work at compile-time. I<noexec> should work on
1328 SunOS, Solaris, *BSD, Linux, IRIX, Tru64 UNIX, MacOS X, and HP-UX
1329 11.x. It is known B<not> to work on AIX and UnixWare. I<noexec>
1330 is expected to work on most operating systems that support the
1331 C<LD_PRELOAD> environment variable. Check your operating system's
1332 manual pages for the dynamic linker (usually ld.so, ld.so.1, dyld,
1333 dld.sl, rld, or loader) to see if C<LD_PRELOAD> is supported.
1335 To enable I<noexec> for a command, use the C<NOEXEC> tag as documented
1336 in the User Specification section above. Here is that example again:
1338 aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
1340 This allows user B<aaron> to run F</usr/bin/more> and F</usr/bin/vi>
1341 with I<noexec> enabled. This will prevent those two commands from
1342 executing other commands (such as a shell). If you are unsure
1343 whether or not your system is capable of supporting I<noexec> you
1344 can always just try it out and see if it works.
1348 Note that restricting shell escapes is not a panacea. Programs
1349 running as root are still capable of many potentially hazardous
1350 operations (such as changing or overwriting files) that could lead
1351 to unintended privilege escalation. In the specific case of an
1352 editor, a safer approach is to give the user permission to run
1357 L<rsh(1)>, L<su(1)>, L<fnmatch(3)>, L<sudo(8)>, L<visudo(8)>
1361 The I<sudoers> file should B<always> be edited by the B<visudo>
1362 command which locks the file and does grammatical checking. It is
1363 imperative that I<sudoers> be free of syntax errors since B<sudo>
1364 will not run with a syntactically incorrect I<sudoers> file.
1366 When using netgroups of machines (as opposed to users), if you
1367 store fully qualified hostnames in the netgroup (as is usually the
1368 case), you either need to have the machine's hostname be fully qualified
1369 as returned by the C<hostname> command or use the I<fqdn> option in
1374 If you feel you have found a bug in B<sudo>, please submit a bug report
1375 at http://www.sudo.ws/sudo/bugs/
1379 Limited free support is available via the sudo-users mailing list,
1380 see http://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or
1381 search the archives.
1385 B<sudo> is provided ``AS IS'' and any express or implied warranties,
1386 including, but not limited to, the implied warranties of merchantability
1387 and fitness for a particular purpose are disclaimed. See the LICENSE
1388 file distributed with B<sudo> or http://www.sudo.ws/sudo/license.html
1389 for complete details.