Annotation of src/usr.bin/sudo/sudoers.pod, Revision 1.11
1.10 millert 1: Copyright (c) 1994-1996, 1998-2005, 2007-2008
1.5 millert 2: Todd C. Miller <Todd.Miller@courtesan.com>
1.1 millert 3:
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.
7:
8: THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9: WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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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.
16:
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.
20:
1.11 ! millert 21: $Sudo: sudoers.pod,v 1.153 2008/11/15 18:34:01 millert Exp $
1.1 millert 22: =pod
23:
24: =head1 NAME
25:
26: sudoers - list of which users may execute what
27:
28: =head1 DESCRIPTION
29:
30: The I<sudoers> file is composed of two types of entries: aliases
31: (basically variables) and user specifications (which specify who
32: may run what).
33:
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).
37:
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.
41:
42: =head2 Quick guide to EBNF
43:
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.,
46:
47: symbol ::= definition | alternate1 | alternate2 ...
48:
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.
54:
1.5 millert 55: =over 4
1.1 millert 56:
57: =item C<?>
58:
59: Means that the preceding symbol (or group of symbols) is optional.
60: That is, it may appear once or not at all.
61:
62: =item C<*>
63:
64: Means that the preceding symbol (or group of symbols) may appear
65: zero or more times.
66:
67: =item C<+>
68:
69: Means that the preceding symbol (or group of symbols) may appear
70: one or more times.
71:
72: =back
73:
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).
77:
78: =head2 Aliases
79:
80: There are four kinds of aliases: C<User_Alias>, C<Runas_Alias>,
81: C<Host_Alias> and C<Cmnd_Alias>.
82:
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)*
87:
88: User_Alias ::= NAME '=' User_List
89:
90: Runas_Alias ::= NAME '=' Runas_List
91:
92: Host_Alias ::= NAME '=' Host_List
93:
94: Cmnd_Alias ::= NAME '=' Cmnd_List
95:
96: NAME ::= [A-Z]([A-Z][0-9]_)*
97:
98: Each I<alias> definition is of the form
99:
100: Alias_Type NAME = item1, item2, ...
101:
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.,
107:
108: Alias_Type NAME = item1, item2, item3 : NAME = item4, item5
109:
110: The definitions of what constitutes a valid I<alias> member follow.
111:
112: User_List ::= User |
113: User ',' User_List
114:
115: User ::= '!'* username |
1.10 millert 116: '!'* '#'uid |
1.1 millert 117: '!'* '%'group |
118: '!'* '+'netgroup |
119: '!'* User_Alias
120:
1.10 millert 121: A C<User_List> is made up of one or more usernames, uids (prefixed
122: with '#'), system groups (prefixed with '%'), netgroups (prefixed
123: with '+') and C<User_Alias>es. Each list item may be prefixed with
124: zero or more '!' operators. An odd number of '!' operators negate
125: the value of the item; an even number just cancel each other out.
126:
127: Runas_List ::= Runas_Member |
128: Runas_Member ',' Runas_List
129:
130: Runas_Member ::= '!'* username |
131: '!'* '#'uid |
132: '!'* '%'group |
133: '!'* +netgroup |
134: '!'* Runas_Alias
135:
136: A C<Runas_List> is similar to a C<User_List> except that instead
137: of C<User_Alias>es it can contain C<Runas_Alias>es. Note that
138: usernames and groups are matched as strings. In other words, two
139: users (groups) with the same uid (gid) are considered to be distinct.
140: If you wish to match all usernames with the same uid (e.g.E<nbsp>root
141: and toor), you can use a uid instead (#0 in the example given).
1.1 millert 142:
143: Host_List ::= Host |
144: Host ',' Host_List
145:
146: Host ::= '!'* hostname |
147: '!'* ip_addr |
148: '!'* network(/netmask)? |
149: '!'* '+'netgroup |
150: '!'* Host_Alias
151:
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
1.5 millert 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
1.1 millert 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.
166:
167: Cmnd_List ::= Cmnd |
168: Cmnd ',' Cmnd_List
169:
170: commandname ::= filename |
171: filename args |
172: filename '""'
173:
174: Cmnd ::= '!'* commandname |
175: '!'* directory |
176: '!'* "sudoedit" |
177: '!'* Cmnd_Alias
178:
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).
189:
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">
1.11 ! millert 195: is used to permit a user to run B<sudo> with the B<-e> option (or
1.1 millert 196: as B<sudoedit>). It may take command line arguments just as
197: a normal command does.
198:
199: =head2 Defaults
200:
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
1.10 millert 204: specific user, a specific command, or commands being run as a specific user.
205: Note that per-command entries may not include command line arguments.
206: If you need to specify arguments, define a C<Cmnd_Alias> and reference
207: that instead.
1.1 millert 208:
209: Default_Type ::= 'Defaults' |
1.6 millert 210: 'Defaults' '@' Host_List |
211: 'Defaults' ':' User_List |
1.10 millert 212: 'Defaults' '!' Cmnd_List |
1.6 millert 213: 'Defaults' '>' Runas_List
1.1 millert 214:
215: Default_Entry ::= Default_Type Parameter_List
216:
217: Parameter_List ::= Parameter |
218: Parameter ',' Parameter_List
219:
220: Parameter ::= Parameter '=' Value |
221: Parameter '+=' Value |
222: Parameter '-=' Value |
223: '!'* Parameter
224:
225: Parameters may be B<flags>, B<integer> values, B<strings>, or B<lists>.
226: Flags are implicitly boolean and can be turned off via the '!'
227: operator. Some integer, string and list parameters may also be
228: used in a boolean context to disable them. Values may be enclosed
229: in double quotes (C<">) when they contain multiple words. Special
230: characters may be escaped with a backslash (C<\>).
231:
232: Lists have two additional assignment operators, C<+=> and C<-=>.
233: These operators are used to add to and delete from a list respectively.
234: It is not an error to use the C<-=> operator to remove an element
235: that does not exist in a list.
236:
1.10 millert 237: Defaults entries are parsed in the following order: generic, host
238: and user Defaults first, then runas Defaults and finally command
239: defaults.
240:
1.1 millert 241: See L</"SUDOERS OPTIONS"> for a list of supported Defaults parameters.
242:
243: =head2 User Specification
244:
245: User_Spec ::= User_List Host_List '=' Cmnd_Spec_List \
246: (':' Host_List '=' Cmnd_Spec_List)*
247:
248: Cmnd_Spec_List ::= Cmnd_Spec |
249: Cmnd_Spec ',' Cmnd_Spec_List
250:
251: Cmnd_Spec ::= Runas_Spec? Tag_Spec* Cmnd
252:
1.10 millert 253: Runas_Spec ::= '(' Runas_List? (: Runas_List)? ')'
1.1 millert 254:
255: Tag_Spec ::= ('NOPASSWD:' | 'PASSWD:' | 'NOEXEC:' | 'EXEC:' |
1.10 millert 256: 'SETENV:' | 'NOSETENV:' )
1.1 millert 257:
258: A B<user specification> determines which commands a user may run
259: (and as what user) on specified hosts. By default, commands are
260: run as B<root>, but this can be changed on a per-command basis.
261:
262: Let's break that down into its constituent parts:
263:
264: =head2 Runas_Spec
265:
1.10 millert 266: A C<Runas_Spec> determines the user and/or the group that a command
267: may be run as. A fully-specified C<Runas_Spec> consists of two
268: C<Runas_List>s (as defined above) separated by a colon (':') and
269: enclosed in a set of parentheses. The first C<Runas_List> indicates
1.11 ! millert 270: which users the command may be run as via B<sudo>'s B<-u> option.
1.10 millert 271: The second defines a list of groups that can be specified via
1.11 ! millert 272: B<sudo>'s B<-g> option. If both C<Runas_List>s are specified, the
1.10 millert 273: command may be run with any combination of users and groups listed
274: in their respective C<Runas_List>s. If only the first is specified,
1.11 ! millert 275: the command may be run as any user in the list but no B<-g> option
1.10 millert 276: may be specified. If the first C<Runas_List> is empty but the
277: second is specified, the command may be run as the invoking user
278: with the group set to any listed in the C<Runas_List>. If no
279: C<Runas_Spec> is specified the command may be run as B<root> and
280: no group may be specified.
281:
282: A C<Runas_Spec> sets the default for the commands that follow it.
283: What this means is that for the entry:
1.1 millert 284:
285: dgb boulder = (operator) /bin/ls, /bin/kill, /usr/bin/lprm
286:
287: The user B<dgb> may run F</bin/ls>, F</bin/kill>, and
288: F</usr/bin/lprm> -- but only as B<operator>. E.g.,
289:
290: $ sudo -u operator /bin/ls.
291:
292: It is also possible to override a C<Runas_Spec> later on in an
293: entry. If we modify the entry like so:
294:
295: dgb boulder = (operator) /bin/ls, (root) /bin/kill, /usr/bin/lprm
296:
297: Then user B<dgb> is now allowed to run F</bin/ls> as B<operator>,
298: but F</bin/kill> and F</usr/bin/lprm> as B<root>.
299:
1.10 millert 300: We can extend this to allow B<dgb> to run C</bin/ls> with either
301: the user or group set to B<operator>:
302:
303: dgb boulder = (operator : operator) /bin/ls, (root) /bin/kill, \
304: /usr/bin/lprm
305:
306: In the following example, user B<tcm> may run commands that access
307: a modem device file with the dialer group. Note that in this example
308: only the group will be set, the command still runs as user B<tcm>.
309:
310: tcm boulder = (:dialer) /usr/bin/tip, /usr/bin/cu, \
311: /usr/local/bin/minicom
312:
1.1 millert 313: =head2 Tag_Spec
314:
315: A command may have zero or more tags associated with it. There are
1.10 millert 316: eight possible tag values, C<NOPASSWD>, C<PASSWD>, C<NOEXEC>, C<EXEC>,
1.1 millert 317: C<SETENV> and C<NOSETENV>.
318: Once a tag is set on a C<Cmnd>, subsequent C<Cmnd>s in the
319: C<Cmnd_Spec_List>, inherit the tag unless it is overridden by the
320: opposite tag (i.e.: C<PASSWD> overrides C<NOPASSWD> and C<NOEXEC>
321: overrides C<EXEC>).
322:
323: =head3 NOPASSWD and PASSWD
324:
325: By default, B<sudo> requires that a user authenticate him or herself
326: before running a command. This behavior can be modified via the
327: C<NOPASSWD> tag. Like a C<Runas_Spec>, the C<NOPASSWD> tag sets
328: a default for the commands that follow it in the C<Cmnd_Spec_List>.
329: Conversely, the C<PASSWD> tag can be used to reverse things.
330: For example:
331:
332: ray rushmore = NOPASSWD: /bin/kill, /bin/ls, /usr/bin/lprm
333:
334: would allow the user B<ray> to run F</bin/kill>, F</bin/ls>, and
1.9 millert 335: F</usr/bin/lprm> as B<root> on the machine rushmore without
1.1 millert 336: authenticating himself. If we only want B<ray> to be able to
337: run F</bin/kill> without a password the entry would be:
338:
339: ray rushmore = NOPASSWD: /bin/kill, PASSWD: /bin/ls, /usr/bin/lprm
340:
341: Note, however, that the C<PASSWD> tag has no effect on users who are
342: in the group specified by the I<exempt_group> option.
343:
344: By default, if the C<NOPASSWD> tag is applied to any of the entries
345: for a user on the current host, he or she will be able to run
346: C<sudo -l> without a password. Additionally, a user may only run
347: C<sudo -v> without a password if the C<NOPASSWD> tag is present
348: for all a user's entries that pertain to the current host.
349: This behavior may be overridden via the verifypw and listpw options.
350:
351: =head3 NOEXEC and EXEC
352:
353: If B<sudo> has been compiled with I<noexec> support and the underlying
354: operating system supports it, the C<NOEXEC> tag can be used to prevent
355: a dynamically-linked executable from running further commands itself.
356:
357: In the following example, user B<aaron> may run F</usr/bin/more>
358: and F</usr/bin/vi> but shell escapes will be disabled.
359:
360: aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
361:
362: See the L<PREVENTING SHELL ESCAPES> section below for more details
363: on how C<NOEXEC> works and whether or not it will work on your system.
364:
365: =head3 SETENV and NOSETENV
366:
367: These tags override the value of the I<setenv> option on a per-command
368: basis. Note that if C<SETENV> has been set for a command, any
369: environment variables set on the command line way are not subject
370: to the restrictions imposed by I<env_check>, I<env_delete>, or
371: I<env_keep>. As such, only trusted users should be allowed to set
1.7 millert 372: variables in this manner. If the command matched is B<ALL>, the
373: C<SETENV> tag is implied for that command; this default may
374: be overridden by use of the C<UNSETENV> tag.
1.1 millert 375:
376: =head2 Wildcards
377:
378: B<sudo> allows shell-style I<wildcards> (aka meta or glob characters)
379: to be used in pathnames as well as command line arguments in the
380: I<sudoers> file. Wildcard matching is done via the B<POSIX>
381: L<fnmatch(3)> routine. Note that these are I<not> regular expressions.
382:
383: =over 8
384:
385: =item C<*>
386:
387: Matches any set of zero or more characters.
388:
389: =item C<?>
390:
391: Matches any single character.
392:
393: =item C<[...]>
394:
395: Matches any character in the specified range.
396:
397: =item C<[!...]>
398:
399: Matches any character B<not> in the specified range.
400:
401: =item C<\x>
402:
403: For any character "x", evaluates to "x". This is used to
404: escape special characters such as: "*", "?", "[", and "}".
405:
406: =back
407:
1.10 millert 408: POSIX character classes may also be used if your system's
409: L<fnmatch(3)> function supports them. However, because the
410: C<':'> character has special meaning in I<sudoers>, it must
411: be escaped. For example:
412:
413: /bin/ls [[\:alpha\:]]*
414:
415: Would match any filename beginning with a letter.
416:
1.1 millert 417: Note that a forward slash ('/') will B<not> be matched by
418: wildcards used in the pathname. When matching the command
419: line arguments, however, a slash B<does> get matched by
420: wildcards. This is to make a path like:
421:
422: /usr/bin/*
423:
424: match F</usr/bin/who> but not F</usr/bin/X11/xterm>.
425:
426: =head2 Exceptions to wildcard rules
427:
428: The following exceptions apply to the above rules:
429:
430: =over 8
431:
432: =item C<"">
433:
434: If the empty string C<""> is the only command line argument in the
435: I<sudoers> entry it means that command is not allowed to be run
436: with B<any> arguments.
437:
438: =back
439:
1.10 millert 440: =head2 Including other files from within sudoers
441:
442: It is possible to include other I<sudoers> files from within the
443: I<sudoers> file currently being parsed using the C<#include>
444: directive, similar to the one used by the C preprocessor. This is
445: useful, for example, for keeping a site-wide I<sudoers> file in
446: addition to a per-machine local one. For the sake of this example
447: the site-wide I<sudoers> will be F</etc/sudoers> and the per-machine
448: one will be F</etc/sudoers.local>. To include F</etc/sudoers.local>
449: from F</etc/sudoers> we would use the following line in F</etc/sudoers>:
450:
451: #include /etc/sudoers.local
452:
453: When B<sudo> reaches this line it will suspend processing of the
454: current file (F</etc/sudoers>) and switch to F</etc/sudoers.local>.
455: Upon reaching the end of F</etc/sudoers.local>, the rest of
456: F</etc/sudoers> will be processed. Files that are included may
457: themselves include other files. A hard limit of 128 nested include
458: files is enforced to prevent include file loops.
459:
1.1 millert 460: =head2 Other special characters and reserved words
461:
462: The pound sign ('#') is used to indicate a comment (unless it is
463: part of a #include directive or unless it occurs in the context of
464: a user name and is followed by one or more digits, in which case
465: it is treated as a uid). Both the comment character and any text
466: after it, up to the end of the line, are ignored.
467:
468: The reserved word B<ALL> is a built-in I<alias> that always causes
469: a match to succeed. It can be used wherever one might otherwise
470: use a C<Cmnd_Alias>, C<User_Alias>, C<Runas_Alias>, or C<Host_Alias>.
471: You should not try to define your own I<alias> called B<ALL> as the
472: built-in alias will be used in preference to your own. Please note
473: that using B<ALL> can be dangerous since in a command context, it
474: allows the user to run B<any> command on the system.
475:
476: An exclamation point ('!') can be used as a logical I<not> operator
477: both in an I<alias> and in front of a C<Cmnd>. This allows one to
478: exclude certain values. Note, however, that using a C<!> in
479: conjunction with the built-in C<ALL> alias to allow a user to
480: run "all but a few" commands rarely works as intended (see SECURITY
481: NOTES below).
482:
483: Long lines can be continued with a backslash ('\') as the last
484: character on the line.
485:
486: Whitespace between elements in a list as well as special syntactic
487: characters in a I<User Specification> ('=', ':', '(', ')') is optional.
488:
489: The following characters must be escaped with a backslash ('\') when
490: used as part of a word (e.g.E<nbsp>a username or hostname):
491: '@', '!', '=', ':', ',', '(', ')', '\'.
492:
493: =head1 SUDOERS OPTIONS
494:
495: B<sudo>'s behavior can be modified by C<Default_Entry> lines, as
496: explained earlier. A list of all supported Defaults parameters,
497: grouped by type, are listed below.
498:
499: B<Flags>:
500:
1.5 millert 501: =over 16
1.1 millert 502:
503: =item always_set_home
504:
505: If set, B<sudo> will set the C<HOME> environment variable to the home
506: directory of the target user (which is root unless the B<-u> option is used).
1.11 ! millert 507: This effectively means that the B<-H> option is always implied.
1.1 millert 508: This flag is I<off> by default.
509:
510: =item authenticate
511:
512: If set, users must authenticate themselves via a password (or other
513: means of authentication) before they may run commands. This default
514: may be overridden via the C<PASSWD> and C<NOPASSWD> tags.
515: This flag is I<on> by default.
516:
1.10 millert 517: =item closefrom_override
518:
519: If set, the user may use B<sudo>'s B<-C> option which
520: overrides the default starting point at which B<sudo> begins
521: closing open file descriptors. This flag is I<off> by default.
522:
1.1 millert 523: =item env_editor
524:
525: If set, B<visudo> will use the value of the EDITOR or VISUAL
526: environment variables before falling back on the default editor list.
527: Note that this may create a security hole as it allows the user to
528: run any arbitrary command as root without logging. A safer alternative
529: is to place a colon-separated list of editors in the C<editor>
530: variable. B<visudo> will then only use the EDITOR or VISUAL if
531: they match a value specified in C<editor>. This flag is I<@env_editor@> by
532: default.
533:
534: =item env_reset
535:
536: If set, B<sudo> will reset the environment to only contain the
537: LOGNAME, SHELL, USER, USERNAME and the C<SUDO_*> variables. Any
538: variables in the caller's environment that match the C<env_keep>
539: and C<env_check> lists are then added. The default contents of the
540: C<env_keep> and C<env_check> lists are displayed when B<sudo> is
1.10 millert 541: run by root with the I<-V> option. If the I<secure_path> option
542: is set, its value will be used for the C<PATH> environment variable.
543: This flag is I<on> by default.
1.1 millert 544:
545: =item fqdn
546:
547: Set this flag if you want to put fully qualified hostnames in the
548: I<sudoers> file. I.e., instead of myhost you would use myhost.mydomain.edu.
549: You may still use the short form if you wish (and even mix the two).
550: Beware that turning on I<fqdn> requires B<sudo> to make DNS lookups
551: which may make B<sudo> unusable if DNS stops working (for example
552: if the machine is not plugged into the network). Also note that
553: you must use the host's official name as DNS knows it. That is,
554: you may not use a host alias (C<CNAME> entry) due to performance
555: issues and the fact that there is no way to get all aliases from
556: DNS. If your machine's hostname (as returned by the C<hostname>
557: command) is already fully qualified you shouldn't need to set
558: I<fqdn>. This flag is I<@fqdn@> by default.
559:
560: =item ignore_dot
561:
562: If set, B<sudo> will ignore '.' or '' (current dir) in the C<PATH>
563: environment variable; the C<PATH> itself is not modified. This
1.10 millert 564: flag is I<@ignore_dot@> by default.
1.1 millert 565:
566: =item ignore_local_sudoers
567:
1.9 millert 568: If set via LDAP, parsing of F<@sysconfdir@/sudoers> will be skipped.
1.1 millert 569: This is intended for Enterprises that wish to prevent the usage of local
570: sudoers files so that only LDAP is used. This thwarts the efforts of
1.9 millert 571: rogue operators who would attempt to add roles to F<@sysconfdir@/sudoers>.
572: When this option is present, F<@sysconfdir@/sudoers> does not even need to
573: exist. Since this option tells B<sudo> how to behave when no specific LDAP
574: entries have been matched, this sudoOption is only meaningful for the
575: C<cn=defaults> section. This flag is I<off> by default.
1.1 millert 576:
577: =item insults
578:
579: If set, B<sudo> will insult users when they enter an incorrect
580: password. This flag is I<@insults@> by default.
581:
582: =item log_host
583:
584: If set, the hostname will be logged in the (non-syslog) B<sudo> log file.
585: This flag is I<off> by default.
586:
587: =item log_year
588:
589: If set, the four-digit year will be logged in the (non-syslog) B<sudo> log file.
590: This flag is I<off> by default.
591:
592: =item long_otp_prompt
593:
594: When validating with a One Time Password (OPT) scheme such as
595: B<S/Key> or B<OPIE>, a two-line prompt is used to make it easier
596: to cut and paste the challenge to a local window. It's not as
597: pretty as the default but some people find it more convenient. This
598: flag is I<@long_otp_prompt@> by default.
599:
600: =item mail_always
601:
602: Send mail to the I<mailto> user every time a users runs B<sudo>.
603: This flag is I<off> by default.
604:
605: =item mail_badpass
606:
607: Send mail to the I<mailto> user if the user running B<sudo> does not
608: enter the correct password. This flag is I<off> by default.
609:
610: =item mail_no_host
611:
612: If set, mail will be sent to the I<mailto> user if the invoking
613: user exists in the I<sudoers> file, but is not allowed to run
614: commands on the current host. This flag is I<@mail_no_host@> by default.
615:
616: =item mail_no_perms
617:
618: If set, mail will be sent to the I<mailto> user if the invoking
619: user is allowed to use B<sudo> but the command they are trying is not
620: listed in their I<sudoers> file entry or is explicitly denied.
621: This flag is I<@mail_no_perms@> by default.
622:
623: =item mail_no_user
624:
625: If set, mail will be sent to the I<mailto> user if the invoking
626: user is not in the I<sudoers> file. This flag is I<@mail_no_user@>
627: by default.
628:
629: =item noexec
630:
631: If set, all commands run via B<sudo> will behave as if the C<NOEXEC>
632: tag has been set, unless overridden by a C<EXEC> tag. See the
633: description of I<NOEXEC and EXEC> below as well as the L<PREVENTING SHELL
634: ESCAPES> section at the end of this manual. This flag is I<off> by default.
635:
636: =item path_info
637:
638: Normally, B<sudo> will tell the user when a command could not be
639: found in their C<PATH> environment variable. Some sites may wish
640: to disable this as it could be used to gather information on the
641: location of executables that the normal user does not have access
642: to. The disadvantage is that if the executable is simply not in
643: the user's C<PATH>, B<sudo> will tell the user that they are not
644: allowed to run it, which can be confusing. This flag is I<@path_info@>
645: by default.
1.7 millert 646:
647: =item passprompt_override
648:
649: The password prompt specified by I<passprompt> will normally only
650: be used if the passwod prompt provided by systems such as PAM matches
651: the string "Password:". If I<passprompt_override> is set, I<passprompt>
652: will always be used. This flag is I<off> by default.
1.1 millert 653:
654: =item preserve_groups
655:
656: By default B<sudo> will initialize the group vector to the list of
657: groups the target user is in. When I<preserve_groups> is set, the
658: user's existing group vector is left unaltered. The real and
659: effective group IDs, however, are still set to match the target
660: user. This flag is I<off> by default.
661:
662: =item requiretty
663:
664: If set, B<sudo> will only run when the user is logged in to a real
1.10 millert 665: tty. When this flag is set, B<sudo> can only be run from a login
666: session and not via other means such as L<cron(8)> or cgi-bin scripts.
667: This flag is I<off> by default.
1.1 millert 668:
669: =item root_sudo
670:
671: If set, root is allowed to run B<sudo> too. Disabling this prevents users
672: from "chaining" B<sudo> commands to get a root shell by doing something
673: like C<"sudo sudo /bin/sh">. Note, however, that turning off I<root_sudo>
674: will also prevent root and from running B<sudoedit>.
675: Disabling I<root_sudo> provides no real additional security; it
676: exists purely for historical reasons.
677: This flag is I<@root_sudo@> by default.
678:
679: =item rootpw
680:
681: If set, B<sudo> will prompt for the root password instead of the password
682: of the invoking user. This flag is I<off> by default.
683:
684: =item runaspw
685:
686: If set, B<sudo> will prompt for the password of the user defined by the
687: I<runas_default> option (defaults to C<@runas_default@>) instead of the
688: password of the invoking user. This flag is I<off> by default.
689:
690: =item set_home
691:
1.11 ! millert 692: If set and B<sudo> is invoked with the B<-s> option the C<HOME>
1.1 millert 693: environment variable will be set to the home directory of the target
694: user (which is root unless the B<-u> option is used). This effectively
1.11 ! millert 695: makes the B<-s> option imply B<-H>. This flag is I<off> by default.
1.1 millert 696:
697: =item set_logname
698:
699: Normally, B<sudo> will set the C<LOGNAME>, C<USER> and C<USERNAME>
700: environment variables to the name of the target user (usually root
1.11 ! millert 701: unless the B<-u> option is given). However, since some programs
1.1 millert 702: (including the RCS revision control system) use C<LOGNAME> to
703: determine the real identity of the user, it may be desirable to
704: change this behavior. This can be done by negating the set_logname
705: option. Note that if the I<env_reset> option has not been disabled,
706: entries in the I<env_keep> list will override the value of
707: I<set_logname>. This flag is I<off> by default.
708:
709: =item setenv
710:
711: Allow the user to disable the I<env_reset> option from the command
712: line. Additionally, environment variables set via the command line
713: are not subject to the restrictions imposed by I<env_check>,
714: I<env_delete>, or I<env_keep>. As such, only trusted users should
715: be allowed to set variables in this manner. This flag is I<off>
716: by default.
717:
718: =item shell_noargs
719:
720: If set and B<sudo> is invoked with no arguments it acts as if the
1.11 ! millert 721: B<-s> option had been given. That is, it runs a shell as root (the
1.1 millert 722: shell is determined by the C<SHELL> environment variable if it is
723: set, falling back on the shell listed in the invoking user's
724: /etc/passwd entry if not). This flag is I<off> by default.
725:
726: =item stay_setuid
727:
728: Normally, when B<sudo> executes a command the real and effective
729: UIDs are set to the target user (root by default). This option
730: changes that behavior such that the real UID is left as the invoking
731: user's UID. In other words, this makes B<sudo> act as a setuid
732: wrapper. This can be useful on systems that disable some potentially
733: dangerous functionality when a program is run setuid. This option
734: is only effective on systems with either the setreuid() or setresuid()
735: function. This flag is I<off> by default.
736:
737: =item targetpw
738:
739: If set, B<sudo> will prompt for the password of the user specified by
1.11 ! millert 740: the B<-u> option (defaults to C<root>) instead of the password of the
1.1 millert 741: invoking user. Note that this precludes the use of a uid not listed
1.11 ! millert 742: in the passwd database as an argument to the B<-u> option.
1.1 millert 743: This flag is I<off> by default.
744:
745: =item tty_tickets
746:
747: If set, users must authenticate on a per-tty basis. Normally,
748: B<sudo> uses a directory in the ticket dir with the same name as
749: the user running it. With this flag enabled, B<sudo> will use a
750: file named for the tty the user is logged in on in that directory.
751: This flag is I<@tty_tickets@> by default.
752:
753: =item use_loginclass
754:
755: If set, B<sudo> will apply the defaults specified for the target user's
756: login class if one exists. Only available if B<sudo> is configured with
757: the --with-logincap option. This flag is I<off> by default.
758:
1.10 millert 759: =item visiblepw
760:
761: By default, B<sudo> will refuse to run if the user must enter a
762: password but it is not possible to disable echo on the terminal.
763: If the I<visiblepw> flag is set, B<sudo> will prompt for a password
764: even when it would be visible on the screen. This makes it possible
765: to run things like C<"rsh somehost sudo ls"> since L<rsh(1)> does
766: not allocate a tty. This flag is I<off> by default.
767:
1.1 millert 768: =back
769:
770: B<Integers>:
771:
1.5 millert 772: =over 16
1.1 millert 773:
1.10 millert 774: =item closefrom
775:
776: Before it executes a command, B<sudo> will close all open file
777: descriptors other than standard input, standard output and standard
778: error (ie: file descriptors 0-2). The I<closefrom> option can be used
779: to specify a different file descriptor at which to start closing.
780: The default is C<3>.
781:
1.1 millert 782: =item passwd_tries
783:
784: The number of tries a user gets to enter his/her password before
785: B<sudo> logs the failure and exits. The default is C<@passwd_tries@>.
786:
787: =back
788:
789: B<Integers that can be used in a boolean context>:
790:
1.5 millert 791: =over 16
1.1 millert 792:
793: =item loglinelen
794:
795: Number of characters per line for the file log. This value is used
796: to decide when to wrap lines for nicer log files. This has no
797: effect on the syslog log file, only the file log. The default is
798: C<@loglen@> (use 0 or negate the option to disable word wrap).
799:
800: =item passwd_timeout
801:
802: Number of minutes before the B<sudo> password prompt times out.
803: The default is C<@password_timeout@>; set this to C<0> for no password timeout.
804:
805: =item timestamp_timeout
806:
807: Number of minutes that can elapse before B<sudo> will ask for a
808: passwd again. The default is C<@timeout@>. Set this to C<0> to always
809: prompt for a password.
810: If set to a value less than C<0> the user's timestamp will never
811: expire. This can be used to allow users to create or delete their
812: own timestamps via C<sudo -v> and C<sudo -k> respectively.
813:
814: =item umask
815:
816: Umask to use when running the command. Negate this option or set
1.10 millert 817: it to 0777 to preserve the user's umask. The actual umask that is
818: used will be the union of the user's umask and C<@sudo_umask@>.
819: This guarantees that B<sudo> never lowers the umask when running a
820: command. Note on systems that use PAM, the default PAM configuration
821: may specify its own umask which will override the value set in
822: I<sudoers>.
1.1 millert 823:
824: =back
825:
826: B<Strings>:
827:
1.5 millert 828: =over 16
1.1 millert 829:
830: =item badpass_message
831:
832: Message that is displayed if a user enters an incorrect password.
833: The default is C<@badpass_message@> unless insults are enabled.
834:
835: =item editor
836:
837: A colon (':') separated list of editors allowed to be used with
838: B<visudo>. B<visudo> will choose the editor that matches the user's
839: EDITOR environment variable if possible, or the first editor in the
840: list that exists and is executable. The default is the path to vi
841: on your system.
842:
843: =item mailsub
844:
845: Subject of the mail sent to the I<mailto> user. The escape C<%h>
846: will expand to the hostname of the machine.
847: Default is C<@mailsub@>.
848:
849: =item noexec_file
850:
851: Path to a shared library containing dummy versions of the execv(),
852: execve() and fexecve() library functions that just return an error.
853: This is used to implement the I<noexec> functionality on systems that
854: support C<LD_PRELOAD> or its equivalent. Defaults to F<@noexec_file@>.
855:
856: =item passprompt
857:
858: The default prompt to use when asking for a password; can be overridden
859: via the B<-p> option or the C<SUDO_PROMPT> environment variable.
860: The following percent (`C<%>') escapes are supported:
861:
1.5 millert 862: =over 4
1.1 millert 863:
864: =item C<%H>
865:
866: expanded to the local hostname including the domain name
867: (on if the machine's hostname is fully qualified or the I<fqdn>
868: option is set)
869:
870: =item C<%h>
871:
872: expanded to the local hostname without the domain name
1.8 millert 873:
874: =item C<%p>
875:
876: expanded to the user whose password is being asked for (respects the
877: I<rootpw>, I<targetpw> and I<runaspw> flags in I<sudoers>)
1.1 millert 878:
879: =item C<%U>
880:
881: expanded to the login name of the user the command will
882: be run as (defaults to root)
883:
884: =item C<%u>
885:
886: expanded to the invoking user's login name
887:
888: =item C<%%>
889:
890: two consecutive C<%> characters are collapsed into a single C<%> character
891:
892: =back
893:
894: The default value is C<@passprompt@>.
895:
896: =item runas_default
897:
1.11 ! millert 898: The default user to run commands as if the B<-u> option is not specified
1.1 millert 899: on the command line. This defaults to C<@runas_default@>.
900: Note that if I<runas_default> is set it B<must> occur before
901: any C<Runas_Alias> specifications.
902:
903: =item syslog_badpri
904:
905: Syslog priority to use when user authenticates unsuccessfully.
906: Defaults to C<@badpri@>.
907:
908: =item syslog_goodpri
909:
910: Syslog priority to use when user authenticates successfully.
911: Defaults to C<@goodpri@>.
912:
1.10 millert 913: =item sudoers_locale
914:
915: Locale to use when parsing the sudoers file. Note that changing
916: the locale may affect how sudoers is interpreted.
917: Defaults to C<"C">.
918:
1.1 millert 919: =item timestampdir
920:
921: The directory in which B<sudo> stores its timestamp files.
922: The default is F<@timedir@>.
923:
924: =item timestampowner
925:
926: The owner of the timestamp directory and the timestamps stored therein.
927: The default is C<root>.
928:
929: =back
930:
931: B<Strings that can be used in a boolean context>:
932:
933: =over 12
934:
1.10 millert 935: =item askpass
936:
937: The I<askpass> option specifies the fully-qualilfy path to a helper
938: program used to read the user's password when no terminal is
939: available. This may be the case when B<sudo> is executed from a
940: graphical (as opposed to text-based) application. The program
941: specified by I<askpass> should display the argument passed to it
942: as the prompt and write the user's password to the standard output.
943: The value of I<askpass> may be overridden by the C<SUDO_ASKPASS>
944: environment variable.
945:
946: =item env_file
947:
948: The I<env_file> options specifies the fully-qualilfy path to a file
949: containing variables to be set in the environment of the program
950: being run. Entries in this file should be of the form C<VARIABLE=value>.
951: Variables in this file are subject to other B<sudo> environment
952: settings such as I<env_keep> and I<env_check>.
953:
1.1 millert 954: =item exempt_group
955:
956: Users in this group are exempt from password and PATH requirements.
957: This is not set by default.
958:
959: =item lecture
960:
961: This option controls when a short lecture will be printed along with
962: the password prompt. It has the following possible values:
963:
964: =over 8
965:
966: =item always
967:
968: Always lecture the user.
969:
970: =item never
971:
972: Never lecture the user.
973:
974: =item once
975:
976: Only lecture the user the first time they run B<sudo>.
977:
978: =back
979:
980: If no value is specified, a value of I<once> is implied.
981: Negating the option results in a value of I<never> being used.
982: The default value is I<@lecture@>.
983:
984: =item lecture_file
985:
986: Path to a file containing an alternate B<sudo> lecture that will
987: be used in place of the standard lecture if the named file exists.
988: By default, B<sudo> uses a built-in lecture.
989:
990: =item listpw
991:
992: This option controls when a password will be required when a
1.11 ! millert 993: user runs B<sudo> with the B<-l> option. It has the following possible values:
1.1 millert 994:
995: =over 8
996:
997: =item all
998:
999: All the user's I<sudoers> entries for the current host must have
1000: the C<NOPASSWD> flag set to avoid entering a password.
1001:
1002: =item always
1003:
1.11 ! millert 1004: The user must always enter a password to use the B<-l> option.
1.1 millert 1005:
1006: =item any
1007:
1008: At least one of the user's I<sudoers> entries for the current host
1009: must have the C<NOPASSWD> flag set to avoid entering a password.
1010:
1011: =item never
1012:
1.11 ! millert 1013: The user need never enter a password to use the B<-l> option.
1.1 millert 1014:
1015: =back
1016:
1017: If no value is specified, a value of I<any> is implied.
1018: Negating the option results in a value of I<never> being used.
1019: The default value is I<any>.
1020:
1021: =item logfile
1022:
1023: Path to the B<sudo> log file (not the syslog log file). Setting a path
1024: turns on logging to a file; negating this option turns it off.
1025: By default, B<sudo> logs via syslog.
1026:
1027: =item mailerflags
1028:
1029: Flags to use when invoking mailer. Defaults to B<-t>.
1030:
1031: =item mailerpath
1032:
1033: Path to mail program used to send warning mail.
1034: Defaults to the path to sendmail found at configure time.
1035:
1.10 millert 1036: =item mailfrom
1037:
1038: Address to use for the "from" address when sending warning and error
1039: mail. The address should be enclosed in double quotes (C<">) to
1040: protect against B<sudo> interpreting the C<@> sign. Defaults to
1041: the name of the user running B<sudo>.
1042:
1.1 millert 1043: =item mailto
1044:
1045: Address to send warning and error mail to. The address should
1046: be enclosed in double quotes (C<">) to protect against B<sudo>
1047: interpreting the C<@> sign. Defaults to C<@mailto@>.
1048:
1.10 millert 1049: =item secure_path
1050:
1051: Path used for every command run from B<sudo>. If you don't trust the
1052: people running B<sudo> to have a sane C<PATH> environment variable you may
1053: want to use this. Another use is if you want to have the "root path"
1054: be separate from the "user path." Users in the group specified by the
1055: I<exempt_group> option are not affected by I<secure_path>.
1056: This is not set by default.
1057:
1.1 millert 1058: =item syslog
1059:
1060: Syslog facility if syslog is being used for logging (negate to
1061: disable syslog logging). Defaults to C<@logfac@>.
1062:
1063: =item verifypw
1064:
1065: This option controls when a password will be required when a user runs
1.11 ! millert 1066: B<sudo> with the B<-v> option. It has the following possible values:
1.1 millert 1067:
1068: =over 8
1069:
1070: =item all
1071:
1072: All the user's I<sudoers> entries for the current host must have
1073: the C<NOPASSWD> flag set to avoid entering a password.
1074:
1075: =item always
1076:
1.11 ! millert 1077: The user must always enter a password to use the B<-v> option.
1.1 millert 1078:
1079: =item any
1080:
1081: At least one of the user's I<sudoers> entries for the current host
1082: must have the C<NOPASSWD> flag set to avoid entering a password.
1083:
1084: =item never
1085:
1.11 ! millert 1086: The user need never enter a password to use the B<-v> option.
1.1 millert 1087:
1088: =back
1089:
1090: If no value is specified, a value of I<all> is implied.
1091: Negating the option results in a value of I<never> being used.
1092: The default value is I<all>.
1093:
1094: =back
1095:
1096: B<Lists that can be used in a boolean context>:
1097:
1.5 millert 1098: =over 16
1.1 millert 1099:
1100: =item env_check
1101:
1102: Environment variables to be removed from the user's environment if
1103: the variable's value contains C<%> or C</> characters. This can
1104: be used to guard against printf-style format vulnerabilities in
1105: poorly-written programs. The argument may be a double-quoted,
1106: space-separated list or a single value without double-quotes. The
1107: list can be replaced, added to, deleted from, or disabled by using
1108: the C<=>, C<+=>, C<-=>, and C<!> operators respectively. Regardless
1109: of whether the C<env_reset> option is enabled or disabled, variables
1110: specified by C<env_check> will be preserved in the environment if
1111: they pass the aforementioned check. The default list of environment
1112: variables to check is displayed when B<sudo> is run by root with
1113: the I<-V> option.
1114:
1115: =item env_delete
1116:
1117: Environment variables to be removed from the user's environment.
1118: The argument may be a double-quoted, space-separated list or a
1119: single value without double-quotes. The list can be replaced, added
1120: to, deleted from, or disabled by using the C<=>, C<+=>, C<-=>, and
1121: C<!> operators respectively. The default list of environment
1122: variables to remove is displayed when B<sudo> is run by root with the
1123: I<-V> option. Note that many operating systems will remove potentially
1124: dangerous variables from the environment of any setuid process (such
1125: as B<sudo>).
1126:
1127: =item env_keep
1128:
1129: Environment variables to be preserved in the user's environment
1130: when the I<env_reset> option is in effect. This allows fine-grained
1131: control over the environment B<sudo>-spawned processes will receive.
1132: The argument may be a double-quoted, space-separated list or a
1133: single value without double-quotes. The list can be replaced, added
1134: to, deleted from, or disabled by using the C<=>, C<+=>, C<-=>, and
1135: C<!> operators respectively. The default list of variables to keep
1136: is displayed when B<sudo> is run by root with the I<-V> option.
1137:
1138: =back
1139:
1140: When logging via L<syslog(3)>, B<sudo> accepts the following values
1141: for the syslog facility (the value of the B<syslog> Parameter):
1142: B<authpriv> (if your OS supports it), B<auth>, B<daemon>, B<user>,
1143: B<local0>, B<local1>, B<local2>, B<local3>, B<local4>, B<local5>,
1144: B<local6>, and B<local7>. The following syslog priorities are
1145: supported: B<alert>, B<crit>, B<debug>, B<emerg>, B<err>, B<info>,
1146: B<notice>, and B<warning>.
1147:
1148: =head1 FILES
1149:
1.9 millert 1150: =over 24
1151:
1152: =item F<@sysconfdir@/sudoers>
1.4 millert 1153:
1.3 millert 1154: List of who can run what
1155:
1.9 millert 1156: =item F</etc/group>
1157:
1.3 millert 1158: Local groups file
1159:
1.9 millert 1160: =item F</etc/netgroup>
1161:
1.3 millert 1162: List of network groups
1.4 millert 1163:
1164: =back
1.1 millert 1165:
1166: =head1 EXAMPLES
1167:
1168: Below are example I<sudoers> entries. Admittedly, some of
1169: these are a bit contrived. First, we define our I<aliases>:
1170:
1171: # User alias specification
1172: User_Alias FULLTIMERS = millert, mikef, dowdy
1173: User_Alias PARTTIMERS = bostley, jwfox, crawl
1174: User_Alias WEBMASTERS = will, wendy, wim
1175:
1176: # Runas alias specification
1177: Runas_Alias OP = root, operator
1178: Runas_Alias DB = oracle, sybase
1179:
1180: # Host alias specification
1181: Host_Alias SPARC = bigtime, eclipse, moet, anchor :\
1182: SGI = grolsch, dandelion, black :\
1183: ALPHA = widget, thalamus, foobar :\
1184: HPPA = boa, nag, python
1185: Host_Alias CUNETS = 128.138.0.0/255.255.0.0
1186: Host_Alias CSNETS = 128.138.243.0, 128.138.204.0/24, 128.138.242.0
1187: Host_Alias SERVERS = master, mail, www, ns
1188: Host_Alias CDROM = orion, perseus, hercules
1189:
1190: # Cmnd alias specification
1191: Cmnd_Alias DUMPS = /usr/bin/mt, /usr/sbin/dump, /usr/sbin/rdump,\
1192: /usr/sbin/restore, /usr/sbin/rrestore
1193: Cmnd_Alias KILL = /usr/bin/kill
1194: Cmnd_Alias PRINTING = /usr/sbin/lpc, /usr/bin/lprm
1195: Cmnd_Alias SHUTDOWN = /usr/sbin/shutdown
1196: Cmnd_Alias HALT = /usr/sbin/halt
1197: Cmnd_Alias REBOOT = /usr/sbin/reboot
1198: Cmnd_Alias SHELLS = /usr/bin/sh, /usr/bin/csh, /usr/bin/ksh, \
1199: /usr/local/bin/tcsh, /usr/bin/rsh, \
1200: /usr/local/bin/zsh
1201: Cmnd_Alias SU = /usr/bin/su
1.5 millert 1202: Cmnd_Alias PAGERS = /usr/bin/more, /usr/bin/pg, /usr/bin/less
1.1 millert 1203:
1204: Here we override some of the compiled in default values. We want
1205: B<sudo> to log via L<syslog(3)> using the I<auth> facility in all
1206: cases. We don't want to subject the full time staff to the B<sudo>
1207: lecture, user B<millert> need not give a password, and we don't
1208: want to reset the C<LOGNAME>, C<USER> or C<USERNAME> environment
1209: variables when running commands as root. Additionally, on the
1210: machines in the I<SERVERS> C<Host_Alias>, we keep an additional
1211: local log file and make sure we log the year in each log line since
1.5 millert 1212: the log entries will be kept around for several years. Lastly, we
1213: disable shell escapes for the commands in the PAGERS C<Cmnd_Alias>
1214: (F</usr/bin/more>, F</usr/bin/pg> and F</usr/bin/less>).
1.1 millert 1215:
1216: # Override built-in defaults
1217: Defaults syslog=auth
1218: Defaults>root !set_logname
1219: Defaults:FULLTIMERS !lecture
1220: Defaults:millert !authenticate
1221: Defaults@SERVERS log_year, logfile=/var/log/sudo.log
1222: Defaults!PAGERS noexec
1223:
1224: The I<User specification> is the part that actually determines who may
1225: run what.
1226:
1227: root ALL = (ALL) ALL
1228: %wheel ALL = (ALL) ALL
1229:
1230: We let B<root> and any user in group B<wheel> run any command on any
1231: host as any user.
1232:
1233: FULLTIMERS ALL = NOPASSWD: ALL
1234:
1235: Full time sysadmins (B<millert>, B<mikef>, and B<dowdy>) may run any
1236: command on any host without authenticating themselves.
1237:
1238: PARTTIMERS ALL = ALL
1239:
1240: Part time sysadmins (B<bostley>, B<jwfox>, and B<crawl>) may run any
1241: command on any host but they must authenticate themselves first
1242: (since the entry lacks the C<NOPASSWD> tag).
1243:
1244: jack CSNETS = ALL
1245:
1246: The user B<jack> may run any command on the machines in the I<CSNETS> alias
1247: (the networks C<128.138.243.0>, C<128.138.204.0>, and C<128.138.242.0>).
1248: Of those networks, only C<128.138.204.0> has an explicit netmask (in
1249: CIDR notation) indicating it is a class C network. For the other
1250: networks in I<CSNETS>, the local machine's netmask will be used
1251: during matching.
1252:
1253: lisa CUNETS = ALL
1254:
1255: The user B<lisa> may run any command on any host in the I<CUNETS> alias
1256: (the class B network C<128.138.0.0>).
1257:
1258: operator ALL = DUMPS, KILL, SHUTDOWN, HALT, REBOOT, PRINTING,\
1259: sudoedit /etc/printcap, /usr/oper/bin/
1260:
1261: The B<operator> user may run commands limited to simple maintenance.
1262: Here, those are commands related to backups, killing processes, the
1263: printing system, shutting down the system, and any commands in the
1264: directory F</usr/oper/bin/>.
1265:
1266: joe ALL = /usr/bin/su operator
1267:
1268: The user B<joe> may only L<su(1)> to operator.
1269:
1.10 millert 1270: pete HPPA = /usr/bin/passwd [A-Za-z]*, !/usr/bin/passwd root
1.1 millert 1271:
1272: The user B<pete> is allowed to change anyone's password except for
1273: root on the I<HPPA> machines. Note that this assumes L<passwd(1)>
1274: does not take multiple usernames on the command line.
1275:
1276: bob SPARC = (OP) ALL : SGI = (OP) ALL
1277:
1278: The user B<bob> may run anything on the I<SPARC> and I<SGI> machines
1279: as any user listed in the I<OP> C<Runas_Alias> (B<root> and B<operator>).
1280:
1281: jim +biglab = ALL
1282:
1283: The user B<jim> may run any command on machines in the I<biglab> netgroup.
1284: B<sudo> knows that "biglab" is a netgroup due to the '+' prefix.
1285:
1286: +secretaries ALL = PRINTING, /usr/bin/adduser, /usr/bin/rmuser
1287:
1288: Users in the B<secretaries> netgroup need to help manage the printers
1289: as well as add and remove users, so they are allowed to run those
1290: commands on all machines.
1291:
1292: fred ALL = (DB) NOPASSWD: ALL
1293:
1294: The user B<fred> can run commands as any user in the I<DB> C<Runas_Alias>
1295: (B<oracle> or B<sybase>) without giving a password.
1296:
1297: john ALPHA = /usr/bin/su [!-]*, !/usr/bin/su *root*
1298:
1299: On the I<ALPHA> machines, user B<john> may su to anyone except root
1.11 ! millert 1300: but he is not allowed to specify any options to the L<su(1)> command.
1.1 millert 1301:
1302: jen ALL, !SERVERS = ALL
1303:
1304: The user B<jen> may run any command on any machine except for those
1305: in the I<SERVERS> C<Host_Alias> (master, mail, www and ns).
1306:
1307: jill SERVERS = /usr/bin/, !SU, !SHELLS
1308:
1309: For any machine in the I<SERVERS> C<Host_Alias>, B<jill> may run
1.5 millert 1310: any commands in the directory F</usr/bin/> except for those commands
1.1 millert 1311: belonging to the I<SU> and I<SHELLS> C<Cmnd_Aliases>.
1312:
1313: steve CSNETS = (operator) /usr/local/op_commands/
1314:
1315: The user B<steve> may run any command in the directory /usr/local/op_commands/
1316: but only as user operator.
1317:
1318: matt valkyrie = KILL
1319:
1320: On his personal workstation, valkyrie, B<matt> needs to be able to
1321: kill hung processes.
1322:
1323: WEBMASTERS www = (www) ALL, (root) /usr/bin/su www
1324:
1325: On the host www, any user in the I<WEBMASTERS> C<User_Alias> (will,
1326: wendy, and wim), may run any command as user www (which owns the
1327: web pages) or simply L<su(1)> to www.
1328:
1329: ALL CDROM = NOPASSWD: /sbin/umount /CDROM,\
1330: /sbin/mount -o nosuid\,nodev /dev/cd0a /CDROM
1331:
1332: Any user may mount or unmount a CD-ROM on the machines in the CDROM
1333: C<Host_Alias> (orion, perseus, hercules) without entering a password.
1334: This is a bit tedious for users to type, so it is a prime candidate
1335: for encapsulating in a shell script.
1336:
1337: =head1 SECURITY NOTES
1338:
1339: It is generally not effective to "subtract" commands from C<ALL>
1340: using the '!' operator. A user can trivially circumvent this
1341: by copying the desired command to a different name and then
1342: executing that. For example:
1343:
1344: bill ALL = ALL, !SU, !SHELLS
1345:
1346: Doesn't really prevent B<bill> from running the commands listed in
1347: I<SU> or I<SHELLS> since he can simply copy those commands to a
1348: different name, or use a shell escape from an editor or other
1349: program. Therefore, these kind of restrictions should be considered
1350: advisory at best (and reinforced by policy).
1351:
1352: =head1 PREVENTING SHELL ESCAPES
1353:
1354: Once B<sudo> executes a program, that program is free to do whatever
1355: it pleases, including run other programs. This can be a security
1356: issue since it is not uncommon for a program to allow shell escapes,
1357: which lets a user bypass B<sudo>'s access control and logging.
1358: Common programs that permit shell escapes include shells (obviously),
1359: editors, paginators, mail and terminal programs.
1360:
1361: There are two basic approaches to this problem:
1362:
1363: =over 10
1364:
1365: =item restrict
1366:
1367: Avoid giving users access to commands that allow the user to run
1368: arbitrary commands. Many editors have a restricted mode where shell
1369: escapes are disabled, though B<sudoedit> is a better solution to
1370: running editors via B<sudo>. Due to the large number of programs that
1371: offer shell escapes, restricting users to the set of programs that
1372: do not if often unworkable.
1373:
1374: =item noexec
1375:
1376: Many systems that support shared libraries have the ability to
1377: override default library functions by pointing an environment
1378: variable (usually C<LD_PRELOAD>) to an alternate shared library.
1379: On such systems, B<sudo>'s I<noexec> functionality can be used to
1380: prevent a program run by B<sudo> from executing any other programs.
1381: Note, however, that this applies only to native dynamically-linked
1382: executables. Statically-linked executables and foreign executables
1383: running under binary emulation are not affected.
1384:
1385: To tell whether or not B<sudo> supports I<noexec>, you can run
1386: the following as root:
1387:
1388: sudo -V | grep "dummy exec"
1389:
1390: If the resulting output contains a line that begins with:
1391:
1392: File containing dummy exec functions:
1393:
1394: then B<sudo> may be able to replace the exec family of functions
1395: in the standard library with its own that simply return an error.
1396: Unfortunately, there is no foolproof way to know whether or not
1397: I<noexec> will work at compile-time. I<noexec> should work on
1398: SunOS, Solaris, *BSD, Linux, IRIX, Tru64 UNIX, MacOS X, and HP-UX
1399: 11.x. It is known B<not> to work on AIX and UnixWare. I<noexec>
1400: is expected to work on most operating systems that support the
1401: C<LD_PRELOAD> environment variable. Check your operating system's
1402: manual pages for the dynamic linker (usually ld.so, ld.so.1, dyld,
1403: dld.sl, rld, or loader) to see if C<LD_PRELOAD> is supported.
1404:
1405: To enable I<noexec> for a command, use the C<NOEXEC> tag as documented
1406: in the User Specification section above. Here is that example again:
1407:
1408: aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
1409:
1410: This allows user B<aaron> to run F</usr/bin/more> and F</usr/bin/vi>
1411: with I<noexec> enabled. This will prevent those two commands from
1412: executing other commands (such as a shell). If you are unsure
1413: whether or not your system is capable of supporting I<noexec> you
1414: can always just try it out and see if it works.
1415:
1416: =back
1417:
1418: Note that restricting shell escapes is not a panacea. Programs
1419: running as root are still capable of many potentially hazardous
1420: operations (such as changing or overwriting files) that could lead
1421: to unintended privilege escalation. In the specific case of an
1422: editor, a safer approach is to give the user permission to run
1423: B<sudoedit>.
1424:
1425: =head1 SEE ALSO
1426:
1427: L<rsh(1)>, L<su(1)>, L<fnmatch(3)>, L<sudo(8)>, L<visudo(8)>
1428:
1429: =head1 CAVEATS
1430:
1431: The I<sudoers> file should B<always> be edited by the B<visudo>
1432: command which locks the file and does grammatical checking. It is
1433: imperative that I<sudoers> be free of syntax errors since B<sudo>
1434: will not run with a syntactically incorrect I<sudoers> file.
1435:
1436: When using netgroups of machines (as opposed to users), if you
1437: store fully qualified hostnames in the netgroup (as is usually the
1438: case), you either need to have the machine's hostname be fully qualified
1439: as returned by the C<hostname> command or use the I<fqdn> option in
1440: I<sudoers>.
1441:
1442: =head1 BUGS
1443:
1444: If you feel you have found a bug in B<sudo>, please submit a bug report
1445: at http://www.sudo.ws/sudo/bugs/
1446:
1447: =head1 SUPPORT
1448:
1449: Limited free support is available via the sudo-users mailing list,
1450: see http://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or
1451: search the archives.
1452:
1453: =head1 DISCLAIMER
1454:
1455: B<sudo> is provided ``AS IS'' and any express or implied warranties,
1456: including, but not limited to, the implied warranties of merchantability
1457: and fitness for a particular purpose are disclaimed. See the LICENSE
1458: file distributed with B<sudo> or http://www.sudo.ws/sudo/license.html
1459: for complete details.
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