Annotation of embedaddon/sudo/doc/sudoers.pod, revision 1.1.1.1
1.1 misho 1: Copyright (c) 1994-1996, 1998-2005, 2007-2011
2: Todd C. Miller <Todd.Miller@courtesan.com>
3:
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19: Materiel Command, USAF, under agreement number F39502-99-1-0512.
20:
21: =pod
22:
23: =head1 NAME
24:
25: sudoers - default sudo security policy module
26:
27: =head1 DESCRIPTION
28:
29: The I<sudoers> policy module determines a user's B<sudo> privileges.
30: It is the default B<sudo> policy plugin. The policy is driven by
31: the F<@sysconfdir@/sudoers> file or, optionally in LDAP. The policy
32: format is described in detail in the L<"SUDOERS FILE FORMAT">
33: section. For information on storing I<sudoers> policy information
34: in LDAP, please see L<sudoers.ldap(5)>.
35:
36: =head2 Authentication and Logging
37:
38: The I<sudoers> security policy requires that most users authenticate
39: themselves before they can use B<sudo>. A password is not required
40: if the invoking user is root, if the target user is the same as the
41: invoking user, or if the policy has disabled authentication for the
42: user or command. Unlike L<su(1)>, when I<sudoers> requires
43: authentication, it validates the invoking user's credentials, not
44: the target user's (or root's) credentials. This can be changed via
45: the I<rootpw>, I<targetpw> and I<runaspw> flags, described later.
46:
47: If a user who is not listed in the policy tries to run a command
48: via B<sudo>, mail is sent to the proper authorities. The address
49: used for such mail is configurable via the I<mailto> Defaults entry
50: (described later) and defaults to C<@mailto@>.
51:
52: Note that mail will not be sent if an unauthorized user tries to
53: run B<sudo> with the B<-l> or B<-v> option. This allows users to
54: determine for themselves whether or not they are allowed to use
55: B<sudo>.
56:
57: If B<sudo> is run by root and the C<SUDO_USER> environment variable
58: is set, the I<sudoers> policy will use this value to determine who
59: the actual user is. This can be used by a user to log commands
60: through sudo even when a root shell has been invoked. It also
61: allows the B<-e> option to remain useful even when invoked via a
62: sudo-run script or program. Note, however, that the I<sudoers>
63: lookup is still done for root, not the user specified by C<SUDO_USER>.
64:
65: I<sudoers> uses time stamp files for credential caching. Once a
66: user has been authenticated, a time stamp is updated and the user
67: may then use sudo without a password for a short period of time
68: (C<@timeout@> minutes unless overridden by the I<timeout> option.
69: By default, I<sudoers> uses a tty-based time stamp which means that
70: there is a separate time stamp for each of a user's login sessions.
71: The I<tty_tickets> option can be disabled to force the use of a
72: single time stamp for all of a user's sessions.
73:
74: I<sudoers> can log both successful and unsuccessful attempts (as well
75: as errors) to syslog(3), a log file, or both. By default, I<sudoers>
76: will log via syslog(3) but this is changeable via the I<syslog>
77: and I<logfile> Defaults settings.
78:
79: I<sudoers> also supports logging a command's input and output
80: streams. I/O logging is not on by default but can be enabled using
81: the I<log_input> and I<log_output> Defaults flags as well as the
82: C<LOG_INPUT> and C<LOG_OUTPUT> command tags.
83:
84: =head2 Command Environment
85:
86: Since environment variables can influence program behavior, I<sudoers>
87: provides a means to restrict which variables from the user's
88: environment are inherited by the command to be run. There are two
89: distinct ways I<sudoers> can deal with environment variables.
90:
91: By default, the I<env_reset> option is enabled. This causes commands
92: to be executed with a minimal environment containing C<TERM>,
93: C<PATH>, C<HOME>, C<MAIL>, C<SHELL>, C<LOGNAME>, C<USER> and C<USERNAME> in
94: addition to variables from the invoking process permitted by the
95: I<env_check> and I<env_keep> options. This is effectively a whitelist
96: for environment variables.
97:
98: If, however, the I<env_reset> option is disabled, any variables not
99: explicitly denied by the I<env_check> and I<env_delete> options are
100: inherited from the invoking process. In this case, I<env_check>
101: and I<env_delete> behave like a blacklist. Since it is not possible
102: to blacklist all potentially dangerous environment variables, use
103: of the default I<env_reset> behavior is encouraged.
104:
105: In all cases, environment variables with a value beginning with
106: C<()> are removed as they could be interpreted as B<bash> functions.
107: The list of environment variables that B<sudo> allows or denies is
108: contained in the output of C<sudo -V> when run as root.
109:
110: Note that the dynamic linker on most operating systems will remove
111: variables that can control dynamic linking from the environment of
112: setuid executables, including B<sudo>. Depending on the operating
113: system this may include C<_RLD*>, C<DYLD_*>, C<LD_*>, C<LDR_*>,
114: C<LIBPATH>, C<SHLIB_PATH>, and others. These type of variables are
115: removed from the environment before B<sudo> even begins execution
116: and, as such, it is not possible for B<sudo> to preserve them.
117:
118: As a special case, if B<sudo>'s B<-i> option (initial login) is
119: specified, I<sudoers> will initialize the environment regardless
120: of the value of I<env_reset>. The I<DISPLAY>, I<PATH> and I<TERM>
121: variables remain unchanged; I<HOME>, I<MAIL>, I<SHELL>, I<USER>,
122: and I<LOGNAME> are set based on the target user. On Linux and AIX
123: systems the contents of F</etc/environment> are also included. All
124: other environment variables are removed.
125:
126: =head1 SUDOERS FILE FORMAT
127:
128: The I<sudoers> file is composed of two types of entries: aliases
129: (basically variables) and user specifications (which specify who
130: may run what).
131:
132: When multiple entries match for a user, they are applied in order.
133: Where there are multiple matches, the last match is used (which is
134: not necessarily the most specific match).
135:
136: The I<sudoers> grammar will be described below in Extended Backus-Naur
137: Form (EBNF). Don't despair if you don't know what EBNF is; it is
138: fairly simple, and the definitions below are annotated.
139:
140: =head2 Quick guide to EBNF
141:
142: EBNF is a concise and exact way of describing the grammar of a language.
143: Each EBNF definition is made up of I<production rules>. E.g.,
144:
145: symbol ::= definition | alternate1 | alternate2 ...
146:
147: Each I<production rule> references others and thus makes up a
148: grammar for the language. EBNF also contains the following
149: operators, which many readers will recognize from regular
150: expressions. Do not, however, confuse them with "wildcard"
151: characters, which have different meanings.
152:
153: =over 4
154:
155: =item C<?>
156:
157: Means that the preceding symbol (or group of symbols) is optional.
158: That is, it may appear once or not at all.
159:
160: =item C<*>
161:
162: Means that the preceding symbol (or group of symbols) may appear
163: zero or more times.
164:
165: =item C<+>
166:
167: Means that the preceding symbol (or group of symbols) may appear
168: one or more times.
169:
170: =back
171:
172: Parentheses may be used to group symbols together. For clarity,
173: we will use single quotes ('') to designate what is a verbatim character
174: string (as opposed to a symbol name).
175:
176: =head2 Aliases
177:
178: There are four kinds of aliases: C<User_Alias>, C<Runas_Alias>,
179: C<Host_Alias> and C<Cmnd_Alias>.
180:
181: Alias ::= 'User_Alias' User_Alias (':' User_Alias)* |
182: 'Runas_Alias' Runas_Alias (':' Runas_Alias)* |
183: 'Host_Alias' Host_Alias (':' Host_Alias)* |
184: 'Cmnd_Alias' Cmnd_Alias (':' Cmnd_Alias)*
185:
186: User_Alias ::= NAME '=' User_List
187:
188: Runas_Alias ::= NAME '=' Runas_List
189:
190: Host_Alias ::= NAME '=' Host_List
191:
192: Cmnd_Alias ::= NAME '=' Cmnd_List
193:
194: NAME ::= [A-Z]([A-Z][0-9]_)*
195:
196: Each I<alias> definition is of the form
197:
198: Alias_Type NAME = item1, item2, ...
199:
200: where I<Alias_Type> is one of C<User_Alias>, C<Runas_Alias>, C<Host_Alias>,
201: or C<Cmnd_Alias>. A C<NAME> is a string of uppercase letters, numbers,
202: and underscore characters ('_'). A C<NAME> B<must> start with an
203: uppercase letter. It is possible to put several alias definitions
204: of the same type on a single line, joined by a colon (':'). E.g.,
205:
206: Alias_Type NAME = item1, item2, item3 : NAME = item4, item5
207:
208: The definitions of what constitutes a valid I<alias> member follow.
209:
210: User_List ::= User |
211: User ',' User_List
212:
213: User ::= '!'* user name |
214: '!'* #uid |
215: '!'* %group |
216: '!'* %#gid |
217: '!'* +netgroup |
218: '!'* %:nonunix_group |
219: '!'* %:#nonunix_gid |
220: '!'* User_Alias
221:
222: A C<User_List> is made up of one or more user names, user ids
223: (prefixed with '#'), system group names and ids (prefixed with '%'
224: and '%#' respectively), netgroups (prefixed with '+'), non-Unix
225: group names and IDs (prefixed with '%:' and '%:#' respectively) and
226: C<User_Alias>es. Each list item may be prefixed with zero or more
227: '!' operators. An odd number of '!' operators negate the value of
228: the item; an even number just cancel each other out.
229:
230: A C<user name>, C<uid>, C<group>, C<gid>, C<netgroup>, C<nonunix_group>
231: or C<nonunix_gid> may be enclosed in double quotes to avoid the
232: need for escaping special characters. Alternately, special characters
233: may be specified in escaped hex mode, e.g. \x20 for space. When
234: using double quotes, any prefix characters must be included inside
235: the quotes.
236:
237: The actual C<nonunix_group> and C<nonunix_gid> syntax depends on
238: the underlying group provider plugin (see the I<group_plugin>
239: description below). For instance, the QAS AD plugin supports the
240: following formats:
241:
242: =over 4
243:
244: =item *
245:
246: Group in the same domain: "Group Name"
247:
248: =item *
249:
250: Group in any domain: "Group Name@FULLY.QUALIFIED.DOMAIN"
251:
252: =item *
253:
254: Group SID: "S-1-2-34-5678901234-5678901234-5678901234-567"
255:
256: =back
257:
258: Note that quotes around group names are optional. Unquoted strings
259: must use a backslash (\) to escape spaces and special characters.
260: See L<"Other special characters and reserved words"> for a list of
261: characters that need to be escaped.
262:
263: Runas_List ::= Runas_Member |
264: Runas_Member ',' Runas_List
265:
266: Runas_Member ::= '!'* user name |
267: '!'* #uid |
268: '!'* %group |
269: '!'* %#gid |
270: '!'* %:nonunix_group |
271: '!'* %:#nonunix_gid |
272: '!'* +netgroup |
273: '!'* Runas_Alias
274:
275: A C<Runas_List> is similar to a C<User_List> except that instead
276: of C<User_Alias>es it can contain C<Runas_Alias>es. Note that
277: user names and groups are matched as strings. In other words, two
278: users (groups) with the same uid (gid) are considered to be distinct.
279: If you wish to match all user names with the same uid (e.g.E<nbsp>root
280: and toor), you can use a uid instead (#0 in the example given).
281:
282: Host_List ::= Host |
283: Host ',' Host_List
284:
285: Host ::= '!'* host name |
286: '!'* ip_addr |
287: '!'* network(/netmask)? |
288: '!'* +netgroup |
289: '!'* Host_Alias
290:
291: A C<Host_List> is made up of one or more host names, IP addresses,
292: network numbers, netgroups (prefixed with '+') and other aliases.
293: Again, the value of an item may be negated with the '!' operator.
294: If you do not specify a netmask along with the network number,
295: B<sudo> will query each of the local host's network interfaces and,
296: if the network number corresponds to one of the hosts's network
297: interfaces, the corresponding netmask will be used. The netmask
298: may be specified either in standard IP address notation
299: (e.g.E<nbsp>255.255.255.0 or ffff:ffff:ffff:ffff::),
300: or CIDR notation (number of bits, e.g.E<nbsp>24 or 64). A host name may
301: include shell-style wildcards (see the L<Wildcards> section below),
302: but unless the C<host name> command on your machine returns the fully
303: qualified host name, you'll need to use the I<fqdn> option for
304: wildcards to be useful. Note B<sudo> only inspects actual network
305: interfaces; this means that IP address 127.0.0.1 (localhost) will
306: never match. Also, the host name "localhost" will only match if
307: that is the actual host name, which is usually only the case for
308: non-networked systems.
309:
310: Cmnd_List ::= Cmnd |
311: Cmnd ',' Cmnd_List
312:
313: commandname ::= file name |
314: file name args |
315: file name '""'
316:
317: Cmnd ::= '!'* commandname |
318: '!'* directory |
319: '!'* "sudoedit" |
320: '!'* Cmnd_Alias
321:
322: A C<Cmnd_List> is a list of one or more commandnames, directories, and other
323: aliases. A commandname is a fully qualified file name which may include
324: shell-style wildcards (see the L<Wildcards> section below). A simple
325: file name allows the user to run the command with any arguments he/she
326: wishes. However, you may also specify command line arguments (including
327: wildcards). Alternately, you can specify C<""> to indicate that the command
328: may only be run B<without> command line arguments. A directory is a
329: fully qualified path name ending in a '/'. When you specify a directory
330: in a C<Cmnd_List>, the user will be able to run any file within that directory
331: (but not in any subdirectories therein).
332:
333: If a C<Cmnd> has associated command line arguments, then the arguments
334: in the C<Cmnd> must match exactly those given by the user on the command line
335: (or match the wildcards if there are any). Note that the following
336: characters must be escaped with a '\' if they are used in command
337: arguments: ',', ':', '=', '\'. The special command C<"sudoedit">
338: is used to permit a user to run B<sudo> with the B<-e> option (or
339: as B<sudoedit>). It may take command line arguments just as
340: a normal command does.
341:
342: =head2 Defaults
343:
344: Certain configuration options may be changed from their default
345: values at runtime via one or more C<Default_Entry> lines. These
346: may affect all users on any host, all users on a specific host, a
347: specific user, a specific command, or commands being run as a specific user.
348: Note that per-command entries may not include command line arguments.
349: If you need to specify arguments, define a C<Cmnd_Alias> and reference
350: that instead.
351:
352: Default_Type ::= 'Defaults' |
353: 'Defaults' '@' Host_List |
354: 'Defaults' ':' User_List |
355: 'Defaults' '!' Cmnd_List |
356: 'Defaults' '>' Runas_List
357:
358: Default_Entry ::= Default_Type Parameter_List
359:
360: Parameter_List ::= Parameter |
361: Parameter ',' Parameter_List
362:
363: Parameter ::= Parameter '=' Value |
364: Parameter '+=' Value |
365: Parameter '-=' Value |
366: '!'* Parameter
367:
368: Parameters may be B<flags>, B<integer> values, B<strings>, or B<lists>.
369: Flags are implicitly boolean and can be turned off via the '!'
370: operator. Some integer, string and list parameters may also be
371: used in a boolean context to disable them. Values may be enclosed
372: in double quotes (C<">) when they contain multiple words. Special
373: characters may be escaped with a backslash (C<\>).
374:
375: Lists have two additional assignment operators, C<+=> and C<-=>.
376: These operators are used to add to and delete from a list respectively.
377: It is not an error to use the C<-=> operator to remove an element
378: that does not exist in a list.
379:
380: Defaults entries are parsed in the following order: generic, host
381: and user Defaults first, then runas Defaults and finally command
382: defaults.
383:
384: See L<"SUDOERS OPTIONS"> for a list of supported Defaults parameters.
385:
386: =head2 User Specification
387:
388: User_Spec ::= User_List Host_List '=' Cmnd_Spec_List \
389: (':' Host_List '=' Cmnd_Spec_List)*
390:
391: Cmnd_Spec_List ::= Cmnd_Spec |
392: Cmnd_Spec ',' Cmnd_Spec_List
393:
394: Cmnd_Spec ::= Runas_Spec? SELinux_Spec? Tag_Spec* Cmnd
395:
396: Runas_Spec ::= '(' Runas_List? (':' Runas_List)? ')'
397:
398: SELinux_Spec ::= ('ROLE=role' | 'TYPE=type')
399:
400: Tag_Spec ::= ('NOPASSWD:' | 'PASSWD:' | 'NOEXEC:' | 'EXEC:' |
401: 'SETENV:' | 'NOSETENV:' | 'LOG_INPUT:' | 'NOLOG_INPUT:' |
402: 'LOG_OUTPUT:' | 'NOLOG_OUTPUT:')
403:
404: A B<user specification> determines which commands a user may run
405: (and as what user) on specified hosts. By default, commands are
406: run as B<root>, but this can be changed on a per-command basis.
407:
408: The basic structure of a user specification is `who where = (as_whom)
409: what'. Let's break that down into its constituent parts:
410:
411: =head2 Runas_Spec
412:
413: A C<Runas_Spec> determines the user and/or the group that a command
414: may be run as. A fully-specified C<Runas_Spec> consists of two
415: C<Runas_List>s (as defined above) separated by a colon (':') and
416: enclosed in a set of parentheses. The first C<Runas_List> indicates
417: which users the command may be run as via B<sudo>'s B<-u> option.
418: The second defines a list of groups that can be specified via
419: B<sudo>'s B<-g> option. If both C<Runas_List>s are specified, the
420: command may be run with any combination of users and groups listed
421: in their respective C<Runas_List>s. If only the first is specified,
422: the command may be run as any user in the list but no B<-g> option
423: may be specified. If the first C<Runas_List> is empty but the
424: second is specified, the command may be run as the invoking user
425: with the group set to any listed in the C<Runas_List>. If no
426: C<Runas_Spec> is specified the command may be run as B<root> and
427: no group may be specified.
428:
429: A C<Runas_Spec> sets the default for the commands that follow it.
430: What this means is that for the entry:
431:
432: dgb boulder = (operator) /bin/ls, /bin/kill, /usr/bin/lprm
433:
434: The user B<dgb> may run F</bin/ls>, F</bin/kill>, and
435: F</usr/bin/lprm> -- but only as B<operator>. E.g.,
436:
437: $ sudo -u operator /bin/ls
438:
439: It is also possible to override a C<Runas_Spec> later on in an
440: entry. If we modify the entry like so:
441:
442: dgb boulder = (operator) /bin/ls, (root) /bin/kill, /usr/bin/lprm
443:
444: Then user B<dgb> is now allowed to run F</bin/ls> as B<operator>,
445: but F</bin/kill> and F</usr/bin/lprm> as B<root>.
446:
447: We can extend this to allow B<dgb> to run C</bin/ls> with either
448: the user or group set to B<operator>:
449:
450: dgb boulder = (operator : operator) /bin/ls, (root) /bin/kill, \
451: /usr/bin/lprm
452:
453: Note that while the group portion of the C<Runas_Spec> permits the
454: user to run as command with that group, it does not force the user
455: to do so. If no group is specified on the command line, the command
456: will run with the group listed in the target user's password database
457: entry. The following would all be permitted by the sudoers entry above:
458:
459: $ sudo -u operator /bin/ls
460: $ sudo -u operator -g operator /bin/ls
461: $ sudo -g operator /bin/ls
462:
463: In the following example, user B<tcm> may run commands that access
464: a modem device file with the dialer group.
465:
466: tcm boulder = (:dialer) /usr/bin/tip, /usr/bin/cu, \
467: /usr/local/bin/minicom
468:
469: Note that in this example only the group will be set, the command
470: still runs as user B<tcm>. E.g.
471:
472: $ sudo -g dialer /usr/bin/cu
473:
474: Multiple users and groups may be present in a C<Runas_Spec>, in
475: which case the user may select any combination of users and groups
476: via the B<-u> and B<-g> options. In this example:
477:
478: alan ALL = (root, bin : operator, system) ALL
479:
480: user B<alan> may run any command as either user root or bin,
481: optionally setting the group to operator or system.
482:
483: =head2 SELinux_Spec
484:
485: On systems with SELinux support, I<sudoers> entries may optionally have
486: an SELinux role and/or type associated with a command. If a role or
487: type is specified with the command it will override any default values
488: specified in I<sudoers>. A role or type specified on the command line,
489: however, will supercede the values in I<sudoers>.
490:
491: =head2 Tag_Spec
492:
493: A command may have zero or more tags associated with it. There are
494: eight possible tag values, C<NOPASSWD>, C<PASSWD>, C<NOEXEC>,
495: C<EXEC>, C<SETENV>, C<NOSETENV>, C<LOG_INPUT>, C<NOLOG_INPUT>,
496: C<LOG_OUTPUT> and C<NOLOG_OUTPUT>. Once a tag is set on a C<Cmnd>,
497: subsequent C<Cmnd>s in the C<Cmnd_Spec_List>, inherit the tag unless
498: it is overridden by the opposite tag (i.e.: C<PASSWD> overrides
499: C<NOPASSWD> and C<NOEXEC> overrides C<EXEC>).
500:
501: =head3 NOPASSWD and PASSWD
502:
503: By default, B<sudo> requires that a user authenticate him or herself
504: before running a command. This behavior can be modified via the
505: C<NOPASSWD> tag. Like a C<Runas_Spec>, the C<NOPASSWD> tag sets
506: a default for the commands that follow it in the C<Cmnd_Spec_List>.
507: Conversely, the C<PASSWD> tag can be used to reverse things.
508: For example:
509:
510: ray rushmore = NOPASSWD: /bin/kill, /bin/ls, /usr/bin/lprm
511:
512: would allow the user B<ray> to run F</bin/kill>, F</bin/ls>, and
513: F</usr/bin/lprm> as B<root> on the machine rushmore without
514: authenticating himself. If we only want B<ray> to be able to
515: run F</bin/kill> without a password the entry would be:
516:
517: ray rushmore = NOPASSWD: /bin/kill, PASSWD: /bin/ls, /usr/bin/lprm
518:
519: Note, however, that the C<PASSWD> tag has no effect on users who are
520: in the group specified by the I<exempt_group> option.
521:
522: By default, if the C<NOPASSWD> tag is applied to any of the entries
523: for a user on the current host, he or she will be able to run
524: C<sudo -l> without a password. Additionally, a user may only run
525: C<sudo -v> without a password if the C<NOPASSWD> tag is present
526: for all a user's entries that pertain to the current host.
527: This behavior may be overridden via the verifypw and listpw options.
528:
529: =head3 NOEXEC and EXEC
530:
531: If B<sudo> has been compiled with I<noexec> support and the underlying
532: operating system supports it, the C<NOEXEC> tag can be used to prevent
533: a dynamically-linked executable from running further commands itself.
534:
535: In the following example, user B<aaron> may run F</usr/bin/more>
536: and F</usr/bin/vi> but shell escapes will be disabled.
537:
538: aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
539:
540: See the L<PREVENTING SHELL ESCAPES> section below for more details
541: on how C<NOEXEC> works and whether or not it will work on your system.
542:
543: =head3 SETENV and NOSETENV
544:
545: These tags override the value of the I<setenv> option on a per-command
546: basis. Note that if C<SETENV> has been set for a command, the user
547: may disable the I<env_reset> option from the command line via the
548: B<-E> option. Additionally, environment variables set on the command
549: line are not subject to the restrictions imposed by I<env_check>,
550: I<env_delete>, or I<env_keep>. As such, only trusted users should
551: be allowed to set variables in this manner. If the command matched
552: is B<ALL>, the C<SETENV> tag is implied for that command; this
553: default may be overridden by use of the C<NOSETENV> tag.
554:
555: =head3 LOG_INPUT and NOLOG_INPUT
556:
557: These tags override the value of the I<log_input> option on a
558: per-command basis. For more information, see the description of
559: I<log_input> in the L<"SUDOERS OPTIONS"> section below.
560:
561: =head3 LOG_OUTPUT and NOLOG_OUTPUT
562:
563: These tags override the value of the I<log_output> option on a
564: per-command basis. For more information, see the description of
565: I<log_output> in the L<"SUDOERS OPTIONS"> section below.
566:
567: =head2 Wildcards
568:
569: B<sudo> allows shell-style I<wildcards> (aka meta or glob characters)
570: to be used in host names, path names and command line arguments in
571: the I<sudoers> file. Wildcard matching is done via the B<POSIX>
572: L<glob(3)> and L<fnmatch(3)> routines. Note that these are I<not>
573: regular expressions.
574:
575: =over 8
576:
577: =item C<*>
578:
579: Matches any set of zero or more characters.
580:
581: =item C<?>
582:
583: Matches any single character.
584:
585: =item C<[...]>
586:
587: Matches any character in the specified range.
588:
589: =item C<[!...]>
590:
591: Matches any character B<not> in the specified range.
592:
593: =item C<\x>
594:
595: For any character "x", evaluates to "x". This is used to
596: escape special characters such as: "*", "?", "[", and "}".
597:
598: =back
599:
600: POSIX character classes may also be used if your system's L<glob(3)>
601: and L<fnmatch(3)> functions support them. However, because the
602: C<':'> character has special meaning in I<sudoers>, it must be
603: escaped. For example:
604:
605: /bin/ls [[\:alpha\:]]*
606:
607: Would match any file name beginning with a letter.
608:
609: Note that a forward slash ('/') will B<not> be matched by
610: wildcards used in the path name. When matching the command
611: line arguments, however, a slash B<does> get matched by
612: wildcards. This is to make a path like:
613:
614: /usr/bin/*
615:
616: match F</usr/bin/who> but not F</usr/bin/X11/xterm>.
617:
618: =head2 Exceptions to wildcard rules
619:
620: The following exceptions apply to the above rules:
621:
622: =over 8
623:
624: =item C<"">
625:
626: If the empty string C<""> is the only command line argument in the
627: I<sudoers> entry it means that command is not allowed to be run
628: with B<any> arguments.
629:
630: =back
631:
632: =head2 Including other files from within sudoers
633:
634: It is possible to include other I<sudoers> files from within the
635: I<sudoers> file currently being parsed using the C<#include> and
636: C<#includedir> directives.
637:
638: This can be used, for example, to keep a site-wide I<sudoers> file
639: in addition to a local, per-machine file. For the sake of this
640: example the site-wide I<sudoers> will be F</etc/sudoers> and the
641: per-machine one will be F</etc/sudoers.local>. To include
642: F</etc/sudoers.local> from within F</etc/sudoers> we would use the
643: following line in F</etc/sudoers>:
644:
645: =over 4
646:
647: C<#include /etc/sudoers.local>
648:
649: =back
650:
651: When B<sudo> reaches this line it will suspend processing of the
652: current file (F</etc/sudoers>) and switch to F</etc/sudoers.local>.
653: Upon reaching the end of F</etc/sudoers.local>, the rest of
654: F</etc/sudoers> will be processed. Files that are included may
655: themselves include other files. A hard limit of 128 nested include
656: files is enforced to prevent include file loops.
657:
658: The file name may include the C<%h> escape, signifying the short form
659: of the host name. I.e., if the machine's host name is "xerxes", then
660:
661: C<#include /etc/sudoers.%h>
662:
663: will cause B<sudo> to include the file F</etc/sudoers.xerxes>.
664:
665: The C<#includedir> directive can be used to create a F<sudo.d>
666: directory that the system package manager can drop I<sudoers> rules
667: into as part of package installation. For example, given:
668:
669: C<#includedir /etc/sudoers.d>
670:
671: B<sudo> will read each file in F</etc/sudoers.d>, skipping file
672: names that end in C<~> or contain a C<.> character to avoid causing
673: problems with package manager or editor temporary/backup files.
674: Files are parsed in sorted lexical order. That is,
675: F</etc/sudoers.d/01_first> will be parsed before
676: F</etc/sudoers.d/10_second>. Be aware that because the sorting is
677: lexical, not numeric, F</etc/sudoers.d/1_whoops> would be loaded
678: B<after> F</etc/sudoers.d/10_second>. Using a consistent number
679: of leading zeroes in the file names can be used to avoid such
680: problems.
681:
682: Note that unlike files included via C<#include>, B<visudo> will not
683: edit the files in a C<#includedir> directory unless one of them
684: contains a syntax error. It is still possible to run B<visudo>
685: with the C<-f> flag to edit the files directly.
686:
687: =head2 Other special characters and reserved words
688:
689: The pound sign ('#') is used to indicate a comment (unless it is
690: part of a #include directive or unless it occurs in the context of
691: a user name and is followed by one or more digits, in which case
692: it is treated as a uid). Both the comment character and any text
693: after it, up to the end of the line, are ignored.
694:
695: The reserved word B<ALL> is a built-in I<alias> that always causes
696: a match to succeed. It can be used wherever one might otherwise
697: use a C<Cmnd_Alias>, C<User_Alias>, C<Runas_Alias>, or C<Host_Alias>.
698: You should not try to define your own I<alias> called B<ALL> as the
699: built-in alias will be used in preference to your own. Please note
700: that using B<ALL> can be dangerous since in a command context, it
701: allows the user to run B<any> command on the system.
702:
703: An exclamation point ('!') can be used as a logical I<not> operator
704: both in an I<alias> and in front of a C<Cmnd>. This allows one to
705: exclude certain values. Note, however, that using a C<!> in
706: conjunction with the built-in C<ALL> alias to allow a user to
707: run "all but a few" commands rarely works as intended (see SECURITY
708: NOTES below).
709:
710: Long lines can be continued with a backslash ('\') as the last
711: character on the line.
712:
713: Whitespace between elements in a list as well as special syntactic
714: characters in a I<User Specification> ('=', ':', '(', ')') is optional.
715:
716: The following characters must be escaped with a backslash ('\') when
717: used as part of a word (e.g.E<nbsp>a user name or host name):
718: '!', '=', ':', ',', '(', ')', '\'.
719:
720: =head1 SUDOERS OPTIONS
721:
722: B<sudo>'s behavior can be modified by C<Default_Entry> lines, as
723: explained earlier. A list of all supported Defaults parameters,
724: grouped by type, are listed below.
725:
726: B<Boolean Flags>:
727:
728: =over 16
729:
730: =item always_set_home
731:
732: If enabled, B<sudo> will set the C<HOME> environment variable to the
733: home directory of the target user (which is root unless the B<-u>
734: option is used). This effectively means that the B<-H> option is
735: always implied. Note that C<HOME> is already set when the the
736: I<env_reset> option is enabled, so I<always_set_home> is only
737: effective for configurations where either I<env_reset> is disabled
738: or C<HOME> is present in the I<env_keep> list.
739: This flag is I<off> by default.
740:
741: =item authenticate
742:
743: If set, users must authenticate themselves via a password (or other
744: means of authentication) before they may run commands. This default
745: may be overridden via the C<PASSWD> and C<NOPASSWD> tags.
746: This flag is I<on> by default.
747:
748: =item closefrom_override
749:
750: If set, the user may use B<sudo>'s B<-C> option which
751: overrides the default starting point at which B<sudo> begins
752: closing open file descriptors. This flag is I<off> by default.
753:
754: =item compress_io
755:
756: If set, and B<sudo> is configured to log a command's input or output,
757: the I/O logs will be compressed using B<zlib>. This flag is I<on>
758: by default when B<sudo> is compiled with B<zlib> support.
759:
760: =item env_editor
761:
762: If set, B<visudo> will use the value of the EDITOR or VISUAL
763: environment variables before falling back on the default editor list.
764: Note that this may create a security hole as it allows the user to
765: run any arbitrary command as root without logging. A safer alternative
766: is to place a colon-separated list of editors in the C<editor>
767: variable. B<visudo> will then only use the EDITOR or VISUAL if
768: they match a value specified in C<editor>. This flag is I<@env_editor@> by
769: default.
770:
771: =item env_reset
772:
773: If set, B<sudo> will reset the environment to only contain the
774: LOGNAME, MAIL, SHELL, USER, USERNAME and the C<SUDO_*> variables. Any
775: variables in the caller's environment that match the C<env_keep>
776: and C<env_check> lists are then added. The default contents of the
777: C<env_keep> and C<env_check> lists are displayed when B<sudo> is
778: run by root with the I<-V> option. If the I<secure_path> option
779: is set, its value will be used for the C<PATH> environment variable.
780: This flag is I<@env_reset@> by default.
781:
782: =item fast_glob
783:
784: Normally, B<sudo> uses the L<glob(3)> function to do shell-style
785: globbing when matching path names. However, since it accesses the
786: file system, L<glob(3)> can take a long time to complete for some
787: patterns, especially when the pattern references a network file
788: system that is mounted on demand (automounted). The I<fast_glob>
789: option causes B<sudo> to use the L<fnmatch(3)> function, which does
790: not access the file system to do its matching. The disadvantage
791: of I<fast_glob> is that it is unable to match relative path names
792: such as F<./ls> or F<../bin/ls>. This has security implications
793: when path names that include globbing characters are used with the
794: negation operator, C<'!'>, as such rules can be trivially bypassed.
795: As such, this option should not be used when I<sudoers> contains rules
796: that contain negated path names which include globbing characters.
797: This flag is I<off> by default.
798:
799: =item fqdn
800:
801: Set this flag if you want to put fully qualified host names in the
802: I<sudoers> file. I.e., instead of myhost you would use myhost.mydomain.edu.
803: You may still use the short form if you wish (and even mix the two).
804: Beware that turning on I<fqdn> requires B<sudo> to make DNS lookups
805: which may make B<sudo> unusable if DNS stops working (for example
806: if the machine is not plugged into the network). Also note that
807: you must use the host's official name as DNS knows it. That is,
808: you may not use a host alias (C<CNAME> entry) due to performance
809: issues and the fact that there is no way to get all aliases from
810: DNS. If your machine's host name (as returned by the C<hostname>
811: command) is already fully qualified you shouldn't need to set
812: I<fqdn>. This flag is I<@fqdn@> by default.
813:
814: =item ignore_dot
815:
816: If set, B<sudo> will ignore '.' or '' (current dir) in the C<PATH>
817: environment variable; the C<PATH> itself is not modified. This
818: flag is I<@ignore_dot@> by default.
819:
820: =item ignore_local_sudoers
821:
822: If set via LDAP, parsing of F<@sysconfdir@/sudoers> will be skipped.
823: This is intended for Enterprises that wish to prevent the usage of local
824: sudoers files so that only LDAP is used. This thwarts the efforts of
825: rogue operators who would attempt to add roles to F<@sysconfdir@/sudoers>.
826: When this option is present, F<@sysconfdir@/sudoers> does not even need to
827: exist. Since this option tells B<sudo> how to behave when no specific LDAP
828: entries have been matched, this sudoOption is only meaningful for the
829: C<cn=defaults> section. This flag is I<off> by default.
830:
831: =item insults
832:
833: If set, B<sudo> will insult users when they enter an incorrect
834: password. This flag is I<@insults@> by default.
835:
836: =item log_host
837:
838: If set, the host name will be logged in the (non-syslog) B<sudo> log file.
839: This flag is I<off> by default.
840:
841: =item log_input
842:
843: If set, B<sudo> will run the command in a I<pseudo tty> and log all
844: user input.
845: If the standard input is not connected to the user's tty, due to
846: I/O redirection or because the command is part of a pipeline, that
847: input is also captured and stored in a separate log file.
848:
849: Input is logged to the directory specified by the I<iolog_dir>
850: option (F<@iolog_dir@> by default) using a unique session ID that
851: is included in the normal B<sudo> log line, prefixed with I<TSID=>.
852: The I<iolog_file> option may be used to control the format of the
853: session ID.
854:
855: Note that user input may contain sensitive information such as
856: passwords (even if they are not echoed to the screen), which will
857: be stored in the log file unencrypted. In most cases, logging the
858: command output via I<log_output> is all that is required.
859:
860: =item log_output
861:
862: If set, B<sudo> will run the command in a I<pseudo tty> and log all
863: output that is sent to the screen, similar to the script(1) command.
864: If the standard output or standard error is not connected to the
865: user's tty, due to I/O redirection or because the command is part
866: of a pipeline, that output is also captured and stored in separate
867: log files.
868:
869: Output is logged to the directory specified by the I<iolog_dir>
870: option (F<@iolog_dir@> by default) using a unique session ID that
871: is included in the normal B<sudo> log line, prefixed with I<TSID=>.
872: The I<iolog_file> option may be used to control the format of the
873: session ID.
874:
875: Output logs may be viewed with the L<sudoreplay(8)> utility, which
876: can also be used to list or search the available logs.
877:
878: =item log_year
879:
880: If set, the four-digit year will be logged in the (non-syslog) B<sudo> log file.
881: This flag is I<off> by default.
882:
883: =item long_otp_prompt
884:
885: When validating with a One Time Password (OTP) scheme such as
886: B<S/Key> or B<OPIE>, a two-line prompt is used to make it easier
887: to cut and paste the challenge to a local window. It's not as
888: pretty as the default but some people find it more convenient. This
889: flag is I<@long_otp_prompt@> by default.
890:
891: =item mail_always
892:
893: Send mail to the I<mailto> user every time a users runs B<sudo>.
894: This flag is I<off> by default.
895:
896: =item mail_badpass
897:
898: Send mail to the I<mailto> user if the user running B<sudo> does not
899: enter the correct password. This flag is I<off> by default.
900:
901: =item mail_no_host
902:
903: If set, mail will be sent to the I<mailto> user if the invoking
904: user exists in the I<sudoers> file, but is not allowed to run
905: commands on the current host. This flag is I<@mail_no_host@> by default.
906:
907: =item mail_no_perms
908:
909: If set, mail will be sent to the I<mailto> user if the invoking
910: user is allowed to use B<sudo> but the command they are trying is not
911: listed in their I<sudoers> file entry or is explicitly denied.
912: This flag is I<@mail_no_perms@> by default.
913:
914: =item mail_no_user
915:
916: If set, mail will be sent to the I<mailto> user if the invoking
917: user is not in the I<sudoers> file. This flag is I<@mail_no_user@>
918: by default.
919:
920: =item noexec
921:
922: If set, all commands run via B<sudo> will behave as if the C<NOEXEC>
923: tag has been set, unless overridden by a C<EXEC> tag. See the
924: description of I<NOEXEC and EXEC> below as well as the L<PREVENTING SHELL
925: ESCAPES> section at the end of this manual. This flag is I<off> by default.
926:
927: =item path_info
928:
929: Normally, B<sudo> will tell the user when a command could not be
930: found in their C<PATH> environment variable. Some sites may wish
931: to disable this as it could be used to gather information on the
932: location of executables that the normal user does not have access
933: to. The disadvantage is that if the executable is simply not in
934: the user's C<PATH>, B<sudo> will tell the user that they are not
935: allowed to run it, which can be confusing. This flag is I<@path_info@>
936: by default.
937:
938: =item passprompt_override
939:
940: The password prompt specified by I<passprompt> will normally only
941: be used if the password prompt provided by systems such as PAM matches
942: the string "Password:". If I<passprompt_override> is set, I<passprompt>
943: will always be used. This flag is I<off> by default.
944:
945: =item preserve_groups
946:
947: By default, B<sudo> will initialize the group vector to the list of
948: groups the target user is in. When I<preserve_groups> is set, the
949: user's existing group vector is left unaltered. The real and
950: effective group IDs, however, are still set to match the target
951: user. This flag is I<off> by default.
952:
953: =item pwfeedback
954:
955: By default, B<sudo> reads the password like most other Unix programs,
956: by turning off echo until the user hits the return (or enter) key.
957: Some users become confused by this as it appears to them that B<sudo>
958: has hung at this point. When I<pwfeedback> is set, B<sudo> will
959: provide visual feedback when the user presses a key. Note that
960: this does have a security impact as an onlooker may be able to
961: determine the length of the password being entered.
962: This flag is I<off> by default.
963:
964: =item requiretty
965:
966: If set, B<sudo> will only run when the user is logged in to a real
967: tty. When this flag is set, B<sudo> can only be run from a login
968: session and not via other means such as L<cron(8)> or cgi-bin scripts.
969: This flag is I<off> by default.
970:
971: =item root_sudo
972:
973: If set, root is allowed to run B<sudo> too. Disabling this prevents users
974: from "chaining" B<sudo> commands to get a root shell by doing something
975: like C<"sudo sudo /bin/sh">. Note, however, that turning off I<root_sudo>
976: will also prevent root from running B<sudoedit>.
977: Disabling I<root_sudo> provides no real additional security; it
978: exists purely for historical reasons.
979: This flag is I<@root_sudo@> by default.
980:
981: =item rootpw
982:
983: If set, B<sudo> will prompt for the root password instead of the password
984: of the invoking user. This flag is I<off> by default.
985:
986: =item runaspw
987:
988: If set, B<sudo> will prompt for the password of the user defined by the
989: I<runas_default> option (defaults to C<@runas_default@>) instead of the
990: password of the invoking user. This flag is I<off> by default.
991:
992: =item set_home
993:
994: If enabled and B<sudo> is invoked with the B<-s> option the C<HOME>
995: environment variable will be set to the home directory of the target
996: user (which is root unless the B<-u> option is used). This effectively
997: makes the B<-s> option imply B<-H>. Note that C<HOME> is already
998: set when the the I<env_reset> option is enabled, so I<set_home> is
999: only effective for configurations where either I<env_reset> is disabled
1000: or C<HOME> is present in the I<env_keep> list.
1001: This flag is I<off> by default.
1002:
1003: =item set_logname
1004:
1005: Normally, B<sudo> will set the C<LOGNAME>, C<USER> and C<USERNAME>
1006: environment variables to the name of the target user (usually root
1007: unless the B<-u> option is given). However, since some programs
1008: (including the RCS revision control system) use C<LOGNAME> to
1009: determine the real identity of the user, it may be desirable to
1010: change this behavior. This can be done by negating the set_logname
1011: option. Note that if the I<env_reset> option has not been disabled,
1012: entries in the I<env_keep> list will override the value of
1013: I<set_logname>. This flag is I<on> by default.
1014:
1015: =item set_utmp
1016:
1017: When enabled, B<sudo> will create an entry in the utmp (or utmpx)
1018: file when a pseudo-tty is allocated. A pseudo-tty is allocated by
1019: B<sudo> when the I<log_input>, I<log_output> or I<use_pty> flags
1020: are enabled. By default, the new entry will be a copy of the user's
1021: existing utmp entry (if any), with the tty, time, type and pid
1022: fields updated. This flag is I<on> by default.
1023:
1024: =item setenv
1025:
1026: Allow the user to disable the I<env_reset> option from the command
1027: line via the B<-E> option. Additionally, environment variables set
1028: via the command line are not subject to the restrictions imposed
1029: by I<env_check>, I<env_delete>, or I<env_keep>. As such, only
1030: trusted users should be allowed to set variables in this manner.
1031: This flag is I<off> by default.
1032:
1033: =item shell_noargs
1034:
1035: If set and B<sudo> is invoked with no arguments it acts as if the
1036: B<-s> option had been given. That is, it runs a shell as root (the
1037: shell is determined by the C<SHELL> environment variable if it is
1038: set, falling back on the shell listed in the invoking user's
1039: /etc/passwd entry if not). This flag is I<off> by default.
1040:
1041: =item stay_setuid
1042:
1043: Normally, when B<sudo> executes a command the real and effective
1044: UIDs are set to the target user (root by default). This option
1045: changes that behavior such that the real UID is left as the invoking
1046: user's UID. In other words, this makes B<sudo> act as a setuid
1047: wrapper. This can be useful on systems that disable some potentially
1048: dangerous functionality when a program is run setuid. This option
1049: is only effective on systems with either the setreuid() or setresuid()
1050: function. This flag is I<off> by default.
1051:
1052: =item targetpw
1053:
1054: If set, B<sudo> will prompt for the password of the user specified
1055: by the B<-u> option (defaults to C<root>) instead of the password
1056: of the invoking user. In addition, the timestamp file name will
1057: include the target user's name. Note that this flag precludes the
1058: use of a uid not listed in the passwd database as an argument to
1059: the B<-u> option. This flag is I<off> by default.
1060:
1061: =item tty_tickets
1062:
1063: If set, users must authenticate on a per-tty basis. With this flag
1064: enabled, B<sudo> will use a file named for the tty the user is
1065: logged in on in the user's time stamp directory. If disabled, the
1066: time stamp of the directory is used instead. This flag is
1067: I<@tty_tickets@> by default.
1068:
1069: =item umask_override
1070:
1071: If set, B<sudo> will set the umask as specified by I<sudoers> without
1072: modification. This makes it possible to specify a more permissive
1073: umask in I<sudoers> than the user's own umask and matches historical
1074: behavior. If I<umask_override> is not set, B<sudo> will set the
1075: umask to be the union of the user's umask and what is specified in
1076: I<sudoers>. This flag is I<@umask_override@> by default.
1077:
1078: =item use_loginclass
1079:
1080: If set, B<sudo> will apply the defaults specified for the target user's
1081: login class if one exists. Only available if B<sudo> is configured with
1082: the --with-logincap option. This flag is I<off> by default.
1083:
1084: =item use_pty
1085:
1086: If set, B<sudo> will run the command in a pseudo-pty even if no I/O
1087: logging is being gone. A malicious program run under B<sudo> could
1088: conceivably fork a background process that retains to the user's
1089: terminal device after the main program has finished executing. Use
1090: of this option will make that impossible. This flag is I<off> by default.
1091:
1092: =item utmp_runas
1093:
1094: If set, B<sudo> will store the name of the runas user when updating
1095: the utmp (or utmpx) file. By default, B<sudo> stores the name of
1096: the invoking user. This flag is I<off> by default.
1097:
1098: =item visiblepw
1099:
1100: By default, B<sudo> will refuse to run if the user must enter a
1101: password but it is not possible to disable echo on the terminal.
1102: If the I<visiblepw> flag is set, B<sudo> will prompt for a password
1103: even when it would be visible on the screen. This makes it possible
1104: to run things like C<"rsh somehost sudo ls"> since L<rsh(1)> does
1105: not allocate a tty. This flag is I<off> by default.
1106:
1107: =back
1108:
1109: B<Integers>:
1110:
1111: =over 16
1112:
1113: =item closefrom
1114:
1115: Before it executes a command, B<sudo> will close all open file
1116: descriptors other than standard input, standard output and standard
1117: error (ie: file descriptors 0-2). The I<closefrom> option can be used
1118: to specify a different file descriptor at which to start closing.
1119: The default is C<3>.
1120:
1121: =item passwd_tries
1122:
1123: The number of tries a user gets to enter his/her password before
1124: B<sudo> logs the failure and exits. The default is C<@passwd_tries@>.
1125:
1126: =back
1127:
1128: B<Integers that can be used in a boolean context>:
1129:
1130: =over 16
1131:
1132: =item loglinelen
1133:
1134: Number of characters per line for the file log. This value is used
1135: to decide when to wrap lines for nicer log files. This has no
1136: effect on the syslog log file, only the file log. The default is
1137: C<@loglen@> (use 0 or negate the option to disable word wrap).
1138:
1139: =item passwd_timeout
1140:
1141: Number of minutes before the B<sudo> password prompt times out, or
1142: C<0> for no timeout. The timeout may include a fractional component
1143: if minute granularity is insufficient, for example C<2.5>. The
1144: default is C<@password_timeout@>.
1145:
1146: =item timestamp_timeout
1147:
1148: Number of minutes that can elapse before B<sudo> will ask for a
1149: passwd again. The timeout may include a fractional component if
1150: minute granularity is insufficient, for example C<2.5>. The default
1151: is C<@timeout@>. Set this to C<0> to always prompt for a password.
1152: If set to a value less than C<0> the user's timestamp will never
1153: expire. This can be used to allow users to create or delete their
1154: own timestamps via C<sudo -v> and C<sudo -k> respectively.
1155:
1156: =item umask
1157:
1158: Umask to use when running the command. Negate this option or set
1159: it to 0777 to preserve the user's umask. The actual umask that is
1160: used will be the union of the user's umask and the value of the
1161: I<umask> option, which defaults to C<@sudo_umask@>. This guarantees
1162: that B<sudo> never lowers the umask when running a command. Note
1163: on systems that use PAM, the default PAM configuration may specify
1164: its own umask which will override the value set in I<sudoers>.
1165:
1166: =back
1167:
1168: B<Strings>:
1169:
1170: =over 16
1171:
1172: =item badpass_message
1173:
1174: Message that is displayed if a user enters an incorrect password.
1175: The default is C<@badpass_message@> unless insults are enabled.
1176:
1177: =item editor
1178:
1179: A colon (':') separated list of editors allowed to be used with
1180: B<visudo>. B<visudo> will choose the editor that matches the user's
1181: EDITOR environment variable if possible, or the first editor in the
1182: list that exists and is executable. The default is C<"@editor@">.
1183:
1184: =item iolog_dir
1185:
1186: The top-level directory to use when constructing the path name for
1187: the input/output log directory. Only used if the I<log_input> or
1188: I<log_output> options are enabled or when the C<LOG_INPUT> or
1189: C<LOG_OUTPUT> tags are present for a command. The session sequence
1190: number, if any, is stored in the directory.
1191: The default is C<"@iolog_dir@">.
1192:
1193: The following percent (`C<%>') escape sequences are supported:
1194:
1195: =over 4
1196:
1197: =item C<%{seq}>
1198:
1199: expanded to a monotonically increasing base-36 sequence number, such as 0100A5,
1200: where every two digits are used to form a new directory, e.g. F<01/00/A5>
1201:
1202: =item C<%{user}>
1203:
1204: expanded to the invoking user's login name
1205:
1206: =item C<%{group}>
1207:
1208: expanded to the name of the invoking user's real group ID
1209:
1210: =item C<%{runas_user}>
1211:
1212: expanded to the login name of the user the command will
1213: be run as (e.g. root)
1214:
1215: =item C<%{runas_group}>
1216:
1217: expanded to the group name of the user the command will
1218: be run as (e.g. wheel)
1219:
1220: =item C<%{hostname}>
1221:
1222: expanded to the local host name without the domain name
1223:
1224: =item C<%{command}>
1225:
1226: expanded to the base name of the command being run
1227:
1228: =back
1229:
1230: In addition, any escape sequences supported by the system's strftime()
1231: function will be expanded.
1232:
1233: To include a literal `C<%>' character, the string `C<%%>' should
1234: be used.
1235:
1236: =item iolog_file
1237:
1238: The path name, relative to I<iolog_dir>, in which to store input/output
1239: logs when the I<log_input> or I<log_output> options are enabled or
1240: when the C<LOG_INPUT> or C<LOG_OUTPUT> tags are present for a command.
1241: Note that I<iolog_file> may contain directory components.
1242: The default is C<"%{seq}">.
1243:
1244: See the I<iolog_dir> option above for a list of supported percent
1245: (`C<%>') escape sequences.
1246:
1247: In addition to the escape sequences, path names that end in six or
1248: more C<X>s will have the C<X>s replaced with a unique combination
1249: of digits and letters, similar to the mktemp() function.
1250:
1251: =item mailsub
1252:
1253: Subject of the mail sent to the I<mailto> user. The escape C<%h>
1254: will expand to the host name of the machine.
1255: Default is C<@mailsub@>.
1256:
1257: =item noexec_file
1258:
1259: This option is deprecated and will be removed in a future release
1260: of B<sudo>. The path to the noexec file should now be set in the
1261: F<@sysconfdir@/sudo.conf> file.
1262:
1263: =item passprompt
1264:
1265: The default prompt to use when asking for a password; can be overridden
1266: via the B<-p> option or the C<SUDO_PROMPT> environment variable.
1267: The following percent (`C<%>') escape sequences are supported:
1268:
1269: =over 4
1270:
1271: =item C<%H>
1272:
1273: expanded to the local host name including the domain name
1274: (only if the machine's host name is fully qualified or the I<fqdn>
1275: option is set)
1276:
1277: =item C<%h>
1278:
1279: expanded to the local host name without the domain name
1280:
1281: =item C<%p>
1282:
1283: expanded to the user whose password is being asked for (respects the
1284: I<rootpw>, I<targetpw> and I<runaspw> flags in I<sudoers>)
1285:
1286: =item C<%U>
1287:
1288: expanded to the login name of the user the command will
1289: be run as (defaults to root)
1290:
1291: =item C<%u>
1292:
1293: expanded to the invoking user's login name
1294:
1295: =item C<%%>
1296:
1297: two consecutive C<%> characters are collapsed into a single C<%> character
1298:
1299: =back
1300:
1301: The default value is C<@passprompt@>.
1302:
1303: =item role
1304:
1305: The default SELinux role to use when constructing a new security
1306: context to run the command. The default role may be overridden on
1307: a per-command basis in I<sudoers> or via command line options.
1308: This option is only available whe B<sudo> is built with SELinux support.
1309:
1310: =item runas_default
1311:
1312: The default user to run commands as if the B<-u> option is not specified
1313: on the command line. This defaults to C<@runas_default@>.
1314:
1315: =item syslog_badpri
1316:
1317: Syslog priority to use when user authenticates unsuccessfully.
1318: Defaults to C<@badpri@>.
1319:
1320: The following syslog priorities are supported: B<alert>, B<crit>,
1321: B<debug>, B<emerg>, B<err>, B<info>, B<notice>, and B<warning>.
1322:
1323: =item syslog_goodpri
1324:
1325: Syslog priority to use when user authenticates successfully.
1326: Defaults to C<@goodpri@>.
1327:
1328: See L<syslog_badpri> for the list of supported syslog priorities.
1329:
1330: =item sudoers_locale
1331:
1332: Locale to use when parsing the sudoers file, logging commands, and
1333: sending email. Note that changing the locale may affect how sudoers
1334: is interpreted. Defaults to C<"C">.
1335:
1336: =item timestampdir
1337:
1338: The directory in which B<sudo> stores its timestamp files.
1339: The default is F<@timedir@>.
1340:
1341: =item timestampowner
1342:
1343: The owner of the timestamp directory and the timestamps stored therein.
1344: The default is C<root>.
1345:
1346: =item type
1347:
1348: The default SELinux type to use when constructing a new security
1349: context to run the command. The default type may be overridden on
1350: a per-command basis in I<sudoers> or via command line options.
1351: This option is only available whe B<sudo> is built with SELinux support.
1352:
1353: =back
1354:
1355: B<Strings that can be used in a boolean context>:
1356:
1357: =over 12
1358:
1359: =item env_file
1360:
1361: The I<env_file> options specifies the fully qualified path to a
1362: file containing variables to be set in the environment of the program
1363: being run. Entries in this file should either be of the form
1364: C<VARIABLE=value> or C<export VARIABLE=value>. The value may
1365: optionally be surrounded by single or double quotes. Variables in
1366: this file are subject to other B<sudo> environment settings such
1367: as I<env_keep> and I<env_check>.
1368:
1369: =item exempt_group
1370:
1371: Users in this group are exempt from password and PATH requirements.
1372: The group name specified should not include a C<%> prefix.
1373: This is not set by default.
1374:
1375: =item group_plugin
1376:
1377: A string containing a I<sudoers> group plugin with optional arguments.
1378: This can be used to implement support for the C<nonunix_group>
1379: syntax described earlier. The string should consist of the plugin
1380: path, either fully-qualified or relative to the F<@prefix@/libexec>
1381: directory, followed by any configuration arguments the plugin
1382: requires. These arguments (if any) will be passed to the plugin's
1383: initialization function. If arguments are present, the string must
1384: be enclosed in double quotes (C<">).
1385:
1386: For example, given F</etc/sudo-group>, a group file in Unix group
1387: format, the sample group plugin can be used:
1388:
1389: Defaults group_plugin="sample_group.so /etc/sudo-group"
1390:
1391: For more information see L<sudo_plugin(5)>.
1392:
1393: =item lecture
1394:
1395: This option controls when a short lecture will be printed along with
1396: the password prompt. It has the following possible values:
1397:
1398: =over 8
1399:
1400: =item always
1401:
1402: Always lecture the user.
1403:
1404: =item never
1405:
1406: Never lecture the user.
1407:
1408: =item once
1409:
1410: Only lecture the user the first time they run B<sudo>.
1411:
1412: =back
1413:
1414: If no value is specified, a value of I<once> is implied.
1415: Negating the option results in a value of I<never> being used.
1416: The default value is I<@lecture@>.
1417:
1418: =item lecture_file
1419:
1420: Path to a file containing an alternate B<sudo> lecture that will
1421: be used in place of the standard lecture if the named file exists.
1422: By default, B<sudo> uses a built-in lecture.
1423:
1424: =item listpw
1425:
1426: This option controls when a password will be required when a
1427: user runs B<sudo> with the B<-l> option. It has the following possible values:
1428:
1429: =over 8
1430:
1431: =item all
1432:
1433: All the user's I<sudoers> entries for the current host must have
1434: the C<NOPASSWD> flag set to avoid entering a password.
1435:
1436: =item always
1437:
1438: The user must always enter a password to use the B<-l> option.
1439:
1440: =item any
1441:
1442: At least one of the user's I<sudoers> entries for the current host
1443: must have the C<NOPASSWD> flag set to avoid entering a password.
1444:
1445: =item never
1446:
1447: The user need never enter a password to use the B<-l> option.
1448:
1449: =back
1450:
1451: If no value is specified, a value of I<any> is implied.
1452: Negating the option results in a value of I<never> being used.
1453: The default value is I<any>.
1454:
1455: =item logfile
1456:
1457: Path to the B<sudo> log file (not the syslog log file). Setting a path
1458: turns on logging to a file; negating this option turns it off.
1459: By default, B<sudo> logs via syslog.
1460:
1461: =item mailerflags
1462:
1463: Flags to use when invoking mailer. Defaults to B<-t>.
1464:
1465: =item mailerpath
1466:
1467: Path to mail program used to send warning mail.
1468: Defaults to the path to sendmail found at configure time.
1469:
1470: =item mailfrom
1471:
1472: Address to use for the "from" address when sending warning and error
1473: mail. The address should be enclosed in double quotes (C<">) to
1474: protect against B<sudo> interpreting the C<@> sign. Defaults to
1475: the name of the user running B<sudo>.
1476:
1477: =item mailto
1478:
1479: Address to send warning and error mail to. The address should
1480: be enclosed in double quotes (C<">) to protect against B<sudo>
1481: interpreting the C<@> sign. Defaults to C<@mailto@>.
1482:
1483: =item secure_path
1484:
1485: Path used for every command run from B<sudo>. If you don't trust the
1486: people running B<sudo> to have a sane C<PATH> environment variable you may
1487: want to use this. Another use is if you want to have the "root path"
1488: be separate from the "user path." Users in the group specified by the
1489: I<exempt_group> option are not affected by I<secure_path>.
1490: This option is @secure_path@ by default.
1491:
1492: =item syslog
1493:
1494: Syslog facility if syslog is being used for logging (negate to
1495: disable syslog logging). Defaults to C<@logfac@>.
1496:
1497: The following syslog facilities are supported: B<authpriv> (if your
1498: OS supports it), B<auth>, B<daemon>, B<user>, B<local0>, B<local1>,
1499: B<local2>, B<local3>, B<local4>, B<local5>, B<local6>, and B<local7>.
1500:
1501: =item verifypw
1502:
1503: This option controls when a password will be required when a user runs
1504: B<sudo> with the B<-v> option. It has the following possible values:
1505:
1506: =over 8
1507:
1508: =item all
1509:
1510: All the user's I<sudoers> entries for the current host must have
1511: the C<NOPASSWD> flag set to avoid entering a password.
1512:
1513: =item always
1514:
1515: The user must always enter a password to use the B<-v> option.
1516:
1517: =item any
1518:
1519: At least one of the user's I<sudoers> entries for the current host
1520: must have the C<NOPASSWD> flag set to avoid entering a password.
1521:
1522: =item never
1523:
1524: The user need never enter a password to use the B<-v> option.
1525:
1526: =back
1527:
1528: If no value is specified, a value of I<all> is implied.
1529: Negating the option results in a value of I<never> being used.
1530: The default value is I<all>.
1531:
1532: =back
1533:
1534: B<Lists that can be used in a boolean context>:
1535:
1536: =over 16
1537:
1538: =item env_check
1539:
1540: Environment variables to be removed from the user's environment if
1541: the variable's value contains C<%> or C</> characters. This can
1542: be used to guard against printf-style format vulnerabilities in
1543: poorly-written programs. The argument may be a double-quoted,
1544: space-separated list or a single value without double-quotes. The
1545: list can be replaced, added to, deleted from, or disabled by using
1546: the C<=>, C<+=>, C<-=>, and C<!> operators respectively. Regardless
1547: of whether the C<env_reset> option is enabled or disabled, variables
1548: specified by C<env_check> will be preserved in the environment if
1549: they pass the aforementioned check. The default list of environment
1550: variables to check is displayed when B<sudo> is run by root with
1551: the I<-V> option.
1552:
1553: =item env_delete
1554:
1555: Environment variables to be removed from the user's environment
1556: when the I<env_reset> option is not in effect. The argument may
1557: be a double-quoted, space-separated list or a single value without
1558: double-quotes. The list can be replaced, added to, deleted from,
1559: or disabled by using the C<=>, C<+=>, C<-=>, and C<!> operators
1560: respectively. The default list of environment variables to remove
1561: is displayed when B<sudo> is run by root with the I<-V> option.
1562: Note that many operating systems will remove potentially dangerous
1563: variables from the environment of any setuid process (such as
1564: B<sudo>).
1565:
1566: =item env_keep
1567:
1568: Environment variables to be preserved in the user's environment
1569: when the I<env_reset> option is in effect. This allows fine-grained
1570: control over the environment B<sudo>-spawned processes will receive.
1571: The argument may be a double-quoted, space-separated list or a
1572: single value without double-quotes. The list can be replaced, added
1573: to, deleted from, or disabled by using the C<=>, C<+=>, C<-=>, and
1574: C<!> operators respectively. The default list of variables to keep
1575: is displayed when B<sudo> is run by root with the I<-V> option.
1576:
1577: =back
1578:
1579: =head1 FILES
1580:
1581: =over 24
1582:
1583: =item F<@sysconfdir@/sudoers>
1584:
1585: List of who can run what
1586:
1587: =item F</etc/group>
1588:
1589: Local groups file
1590:
1591: =item F</etc/netgroup>
1592:
1593: List of network groups
1594:
1595: =item F<@iolog_dir@>
1596:
1597: I/O log files
1598:
1599: =item F<@timedir@>
1600:
1601: Directory containing time stamps for the I<sudoers> security policy
1602:
1603: =item F</etc/environment>
1604:
1605: Initial environment for B<-i> mode on Linux and AIX
1606:
1607: =back
1608:
1609: =head1 EXAMPLES
1610:
1611: Below are example I<sudoers> entries. Admittedly, some of
1612: these are a bit contrived. First, we allow a few environment
1613: variables to pass and then define our I<aliases>:
1614:
1615: # Run X applications through sudo; HOME is used to find the
1616: # .Xauthority file. Note that other programs use HOME to find
1617: # configuration files and this may lead to privilege escalation!
1618: Defaults env_keep += "DISPLAY HOME"
1619:
1620: # User alias specification
1621: User_Alias FULLTIMERS = millert, mikef, dowdy
1622: User_Alias PARTTIMERS = bostley, jwfox, crawl
1623: User_Alias WEBMASTERS = will, wendy, wim
1624:
1625: # Runas alias specification
1626: Runas_Alias OP = root, operator
1627: Runas_Alias DB = oracle, sybase
1628: Runas_Alias ADMINGRP = adm, oper
1629:
1630: # Host alias specification
1631: Host_Alias SPARC = bigtime, eclipse, moet, anchor :\
1632: SGI = grolsch, dandelion, black :\
1633: ALPHA = widget, thalamus, foobar :\
1634: HPPA = boa, nag, python
1635: Host_Alias CUNETS = 128.138.0.0/255.255.0.0
1636: Host_Alias CSNETS = 128.138.243.0, 128.138.204.0/24, 128.138.242.0
1637: Host_Alias SERVERS = master, mail, www, ns
1638: Host_Alias CDROM = orion, perseus, hercules
1639:
1640: # Cmnd alias specification
1641: Cmnd_Alias DUMPS = /usr/bin/mt, /usr/sbin/dump, /usr/sbin/rdump,\
1642: /usr/sbin/restore, /usr/sbin/rrestore
1643: Cmnd_Alias KILL = /usr/bin/kill
1644: Cmnd_Alias PRINTING = /usr/sbin/lpc, /usr/bin/lprm
1645: Cmnd_Alias SHUTDOWN = /usr/sbin/shutdown
1646: Cmnd_Alias HALT = /usr/sbin/halt
1647: Cmnd_Alias REBOOT = /usr/sbin/reboot
1648: Cmnd_Alias SHELLS = /usr/bin/sh, /usr/bin/csh, /usr/bin/ksh, \
1649: /usr/local/bin/tcsh, /usr/bin/rsh, \
1650: /usr/local/bin/zsh
1651: Cmnd_Alias SU = /usr/bin/su
1652: Cmnd_Alias PAGERS = /usr/bin/more, /usr/bin/pg, /usr/bin/less
1653:
1654: Here we override some of the compiled in default values. We want
1655: B<sudo> to log via L<syslog(3)> using the I<auth> facility in all
1656: cases. We don't want to subject the full time staff to the B<sudo>
1657: lecture, user B<millert> need not give a password, and we don't
1658: want to reset the C<LOGNAME>, C<USER> or C<USERNAME> environment
1659: variables when running commands as root. Additionally, on the
1660: machines in the I<SERVERS> C<Host_Alias>, we keep an additional
1661: local log file and make sure we log the year in each log line since
1662: the log entries will be kept around for several years. Lastly, we
1663: disable shell escapes for the commands in the PAGERS C<Cmnd_Alias>
1664: (F</usr/bin/more>, F</usr/bin/pg> and F</usr/bin/less>).
1665:
1666: # Override built-in defaults
1667: Defaults syslog=auth
1668: Defaults>root !set_logname
1669: Defaults:FULLTIMERS !lecture
1670: Defaults:millert !authenticate
1671: Defaults@SERVERS log_year, logfile=/var/log/sudo.log
1672: Defaults!PAGERS noexec
1673:
1674: The I<User specification> is the part that actually determines who may
1675: run what.
1676:
1677: root ALL = (ALL) ALL
1678: %wheel ALL = (ALL) ALL
1679:
1680: We let B<root> and any user in group B<wheel> run any command on any
1681: host as any user.
1682:
1683: FULLTIMERS ALL = NOPASSWD: ALL
1684:
1685: Full time sysadmins (B<millert>, B<mikef>, and B<dowdy>) may run any
1686: command on any host without authenticating themselves.
1687:
1688: PARTTIMERS ALL = ALL
1689:
1690: Part time sysadmins (B<bostley>, B<jwfox>, and B<crawl>) may run any
1691: command on any host but they must authenticate themselves first
1692: (since the entry lacks the C<NOPASSWD> tag).
1693:
1694: jack CSNETS = ALL
1695:
1696: The user B<jack> may run any command on the machines in the I<CSNETS> alias
1697: (the networks C<128.138.243.0>, C<128.138.204.0>, and C<128.138.242.0>).
1698: Of those networks, only C<128.138.204.0> has an explicit netmask (in
1699: CIDR notation) indicating it is a class C network. For the other
1700: networks in I<CSNETS>, the local machine's netmask will be used
1701: during matching.
1702:
1703: lisa CUNETS = ALL
1704:
1705: The user B<lisa> may run any command on any host in the I<CUNETS> alias
1706: (the class B network C<128.138.0.0>).
1707:
1708: operator ALL = DUMPS, KILL, SHUTDOWN, HALT, REBOOT, PRINTING,\
1709: sudoedit /etc/printcap, /usr/oper/bin/
1710:
1711: The B<operator> user may run commands limited to simple maintenance.
1712: Here, those are commands related to backups, killing processes, the
1713: printing system, shutting down the system, and any commands in the
1714: directory F</usr/oper/bin/>.
1715:
1716: joe ALL = /usr/bin/su operator
1717:
1718: The user B<joe> may only L<su(1)> to operator.
1719:
1720: pete HPPA = /usr/bin/passwd [A-Za-z]*, !/usr/bin/passwd root
1721:
1722: %opers ALL = (: ADMINGRP) /usr/sbin/
1723:
1724: Users in the B<opers> group may run commands in F</usr/sbin/> as themselves
1725: with any group in the I<ADMINGRP> C<Runas_Alias> (the B<adm> and B<oper>
1726: groups).
1727:
1728: The user B<pete> is allowed to change anyone's password except for
1729: root on the I<HPPA> machines. Note that this assumes L<passwd(1)>
1730: does not take multiple user names on the command line.
1731:
1732: bob SPARC = (OP) ALL : SGI = (OP) ALL
1733:
1734: The user B<bob> may run anything on the I<SPARC> and I<SGI> machines
1735: as any user listed in the I<OP> C<Runas_Alias> (B<root> and B<operator>).
1736:
1737: jim +biglab = ALL
1738:
1739: The user B<jim> may run any command on machines in the I<biglab> netgroup.
1740: B<sudo> knows that "biglab" is a netgroup due to the '+' prefix.
1741:
1742: +secretaries ALL = PRINTING, /usr/bin/adduser, /usr/bin/rmuser
1743:
1744: Users in the B<secretaries> netgroup need to help manage the printers
1745: as well as add and remove users, so they are allowed to run those
1746: commands on all machines.
1747:
1748: fred ALL = (DB) NOPASSWD: ALL
1749:
1750: The user B<fred> can run commands as any user in the I<DB> C<Runas_Alias>
1751: (B<oracle> or B<sybase>) without giving a password.
1752:
1753: john ALPHA = /usr/bin/su [!-]*, !/usr/bin/su *root*
1754:
1755: On the I<ALPHA> machines, user B<john> may su to anyone except root
1756: but he is not allowed to specify any options to the L<su(1)> command.
1757:
1758: jen ALL, !SERVERS = ALL
1759:
1760: The user B<jen> may run any command on any machine except for those
1761: in the I<SERVERS> C<Host_Alias> (master, mail, www and ns).
1762:
1763: jill SERVERS = /usr/bin/, !SU, !SHELLS
1764:
1765: For any machine in the I<SERVERS> C<Host_Alias>, B<jill> may run
1766: any commands in the directory F</usr/bin/> except for those commands
1767: belonging to the I<SU> and I<SHELLS> C<Cmnd_Aliases>.
1768:
1769: steve CSNETS = (operator) /usr/local/op_commands/
1770:
1771: The user B<steve> may run any command in the directory /usr/local/op_commands/
1772: but only as user operator.
1773:
1774: matt valkyrie = KILL
1775:
1776: On his personal workstation, valkyrie, B<matt> needs to be able to
1777: kill hung processes.
1778:
1779: WEBMASTERS www = (www) ALL, (root) /usr/bin/su www
1780:
1781: On the host www, any user in the I<WEBMASTERS> C<User_Alias> (will,
1782: wendy, and wim), may run any command as user www (which owns the
1783: web pages) or simply L<su(1)> to www.
1784:
1785: ALL CDROM = NOPASSWD: /sbin/umount /CDROM,\
1786: /sbin/mount -o nosuid\,nodev /dev/cd0a /CDROM
1787:
1788: Any user may mount or unmount a CD-ROM on the machines in the CDROM
1789: C<Host_Alias> (orion, perseus, hercules) without entering a password.
1790: This is a bit tedious for users to type, so it is a prime candidate
1791: for encapsulating in a shell script.
1792:
1793: =head1 SECURITY NOTES
1794:
1795: It is generally not effective to "subtract" commands from C<ALL>
1796: using the '!' operator. A user can trivially circumvent this
1797: by copying the desired command to a different name and then
1798: executing that. For example:
1799:
1800: bill ALL = ALL, !SU, !SHELLS
1801:
1802: Doesn't really prevent B<bill> from running the commands listed in
1803: I<SU> or I<SHELLS> since he can simply copy those commands to a
1804: different name, or use a shell escape from an editor or other
1805: program. Therefore, these kind of restrictions should be considered
1806: advisory at best (and reinforced by policy).
1807:
1808: Furthermore, if the I<fast_glob> option is in use, it is not possible
1809: to reliably negate commands where the path name includes globbing
1810: (aka wildcard) characters. This is because the C library's
1811: L<fnmatch(3)> function cannot resolve relative paths. While this
1812: is typically only an inconvenience for rules that grant privileges,
1813: it can result in a security issue for rules that subtract or revoke
1814: privileges.
1815:
1816: For example, given the following I<sudoers> entry:
1817:
1818: john ALL = /usr/bin/passwd [a-zA-Z0-9]*, /usr/bin/chsh [a-zA-Z0-9]*,
1819: /usr/bin/chfn [a-zA-Z0-9]*, !/usr/bin/* root
1820:
1821: User B<john> can still run C</usr/bin/passwd root> if I<fast_glob> is
1822: enabled by changing to F</usr/bin> and running C<./passwd root> instead.
1823:
1824: =head1 PREVENTING SHELL ESCAPES
1825:
1826: Once B<sudo> executes a program, that program is free to do whatever
1827: it pleases, including run other programs. This can be a security
1828: issue since it is not uncommon for a program to allow shell escapes,
1829: which lets a user bypass B<sudo>'s access control and logging.
1830: Common programs that permit shell escapes include shells (obviously),
1831: editors, paginators, mail and terminal programs.
1832:
1833: There are two basic approaches to this problem:
1834:
1835: =over 10
1836:
1837: =item restrict
1838:
1839: Avoid giving users access to commands that allow the user to run
1840: arbitrary commands. Many editors have a restricted mode where shell
1841: escapes are disabled, though B<sudoedit> is a better solution to
1842: running editors via B<sudo>. Due to the large number of programs that
1843: offer shell escapes, restricting users to the set of programs that
1844: do not is often unworkable.
1845:
1846: =item noexec
1847:
1848: Many systems that support shared libraries have the ability to
1849: override default library functions by pointing an environment
1850: variable (usually C<LD_PRELOAD>) to an alternate shared library.
1851: On such systems, B<sudo>'s I<noexec> functionality can be used to
1852: prevent a program run by B<sudo> from executing any other programs.
1853: Note, however, that this applies only to native dynamically-linked
1854: executables. Statically-linked executables and foreign executables
1855: running under binary emulation are not affected.
1856:
1857: The I<noexec> feature is known to work on SunOS, Solaris, *BSD,
1858: Linux, IRIX, Tru64 UNIX, MacOS X, HP-UX 11.x and AIX 5.3 and above.
1859: It should be supported on most operating systems that support the
1860: C<LD_PRELOAD> environment variable. Check your operating system's
1861: manual pages for the dynamic linker (usually ld.so, ld.so.1, dyld,
1862: dld.sl, rld, or loader) to see if C<LD_PRELOAD> is supported.
1863:
1864: On Solaris 10 and higher, I<noexec> uses Solaris privileges instead
1865: of the C<LD_PRELOAD> environment variable.
1866:
1867: To enable I<noexec> for a command, use the C<NOEXEC> tag as documented
1868: in the User Specification section above. Here is that example again:
1869:
1870: aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
1871:
1872: This allows user B<aaron> to run F</usr/bin/more> and F</usr/bin/vi>
1873: with I<noexec> enabled. This will prevent those two commands from
1874: executing other commands (such as a shell). If you are unsure
1875: whether or not your system is capable of supporting I<noexec> you
1876: can always just try it out and check whether shell escapes work
1877: when I<noexec> is enabled.
1878:
1879: =back
1880:
1881: Note that restricting shell escapes is not a panacea. Programs
1882: running as root are still capable of many potentially hazardous
1883: operations (such as changing or overwriting files) that could lead
1884: to unintended privilege escalation. In the specific case of an
1885: editor, a safer approach is to give the user permission to run
1886: B<sudoedit>.
1887:
1888: =head1 SECURITY NOTES
1889:
1890: I<sudoers> will check the ownership of its time stamp directory
1891: (F<@timedir@> by default) and ignore the directory's contents if
1892: it is not owned by root or if it is writable by a user other than
1893: root. On systems that allow non-root users to give away files via
1894: L<chown(2)>, if the time stamp directory is located in a world-writable
1895: directory (e.g., F</tmp>), it is possible for a user to create the
1896: time stamp directory before B<sudo> is run. However, because
1897: I<sudoers> checks the ownership and mode of the directory and its
1898: contents, the only damage that can be done is to "hide" files by
1899: putting them in the time stamp dir. This is unlikely to happen
1900: since once the time stamp dir is owned by root and inaccessible by
1901: any other user, the user placing files there would be unable to get
1902: them back out.
1903:
1904: I<sudoers> will not honor time stamps set far in the future. Time
1905: stamps with a date greater than current_time + 2 * C<TIMEOUT> will
1906: be ignored and sudo will log and complain. This is done to keep a
1907: user from creating his/her own time stamp with a bogus date on
1908: systems that allow users to give away files if the time stamp directory
1909: is located in a world-writable directory.
1910:
1911: On systems where the boot time is available, I<sudoers> will ignore
1912: time stamps that date from before the machine booted.
1913:
1914: Since time stamp files live in the file system, they can outlive a
1915: user's login session. As a result, a user may be able to login,
1916: run a command with B<sudo> after authenticating, logout, login
1917: again, and run B<sudo> without authenticating so long as the time
1918: stamp file's modification time is within C<@timeout@> minutes (or
1919: whatever the timeout is set to in I<sudoers>). When the I<tty_tickets>
1920: option is enabled, the time stamp has per-tty granularity but still
1921: may outlive the user's session. On Linux systems where the devpts
1922: filesystem is used, Solaris systems with the devices filesystem,
1923: as well as other systems that utilize a devfs filesystem that
1924: monotonically increase the inode number of devices as they are
1925: created (such as Mac OS X), I<sudoers> is able to determine when a
1926: tty-based time stamp file is stale and will ignore it. Administrators
1927: should not rely on this feature as it is not universally available.
1928:
1929: If users have sudo C<ALL> there is nothing to prevent them from
1930: creating their own program that gives them a root shell (or making
1931: their own copy of a shell) regardless of any '!' elements in the
1932: user specification.
1933:
1934: =head1 SEE ALSO
1935:
1936: L<rsh(1)>, L<su(1)>, L<fnmatch(3)>, L<glob(3)>, L<mktemp(3)>, L<strftime(3)>,
1937: L<sudoers.ldap(5)>, L<sudo_plugin(8)>, L<sudo(8)>, L<visudo(8)>
1938:
1939: =head1 CAVEATS
1940:
1941: The I<sudoers> file should B<always> be edited by the B<visudo>
1942: command which locks the file and does grammatical checking. It is
1943: imperative that I<sudoers> be free of syntax errors since B<sudo>
1944: will not run with a syntactically incorrect I<sudoers> file.
1945:
1946: When using netgroups of machines (as opposed to users), if you
1947: store fully qualified host name in the netgroup (as is usually the
1948: case), you either need to have the machine's host name be fully qualified
1949: as returned by the C<hostname> command or use the I<fqdn> option in
1950: I<sudoers>.
1951:
1952: =head1 BUGS
1953:
1954: If you feel you have found a bug in B<sudo>, please submit a bug report
1955: at http://www.sudo.ws/sudo/bugs/
1956:
1957: =head1 SUPPORT
1958:
1959: Limited free support is available via the sudo-users mailing list,
1960: see http://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or
1961: search the archives.
1962:
1963: =head1 DISCLAIMER
1964:
1965: B<sudo> is provided ``AS IS'' and any express or implied warranties,
1966: including, but not limited to, the implied warranties of merchantability
1967: and fitness for a particular purpose are disclaimed. See the LICENSE
1968: file distributed with B<sudo> or http://www.sudo.ws/sudo/license.html
1969: for complete details.
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