=cut Copyright (c) 1994-1996,1998-2001 Todd C. Miller <Todd.Miller@courtesan.com> All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. 3. The name of the author may not be used to endorse or promote products derived from this software without specific prior written permission from the author. 4. Products derived from this software may not be called "Sudo" nor may "Sudo" appear in their names without specific prior written permission from the author. THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. $Sudo: sudoers.pod,v 1.63 2002/01/13 18:36:44 millert Exp $ =pod =head1 NAME sudoers - list of which users may execute what =head1 DESCRIPTION The I<sudoers> file is composed of two types of entries: aliases (basically variables) and user specifications (which specify who may run what). The grammar of I<sudoers> will be described below in Extended Backus-Naur Form (EBNF). Don't despair if you don't know what EBNF is; it is fairly simple, and the definitions below are annotated. =head2 Quick guide to EBNF EBNF is a concise and exact way of describing the grammar of a language. Each EBNF definition is made up of I<production rules>. E.g., symbol ::= definition | alternate1 | alternate2 ... Each I<production rule> references others and thus makes up a grammar for the language. EBNF also contains the following operators, which many readers will recognize from regular expressions. Do not, however, confuse them with "wildcard" characters, which have different meanings. =over 8 =item C<?> Means that the preceding symbol (or group of symbols) is optional. That is, it may appear once or not at all. =item C<*> Means that the preceding symbol (or group of symbols) may appear zero or more times. =item C<+> Means that the preceding symbol (or group of symbols) may appear one or more times. =back Parentheses may be used to group symbols together. For clarity, we will use single quotes ('') to designate what is a verbatim character string (as opposed to a symbol name). =head2 Aliases There are four kinds of aliases: C<User_Alias>, C<Runas_Alias>, C<Host_Alias> and C<Cmnd_Alias>. Alias ::= 'User_Alias' User_Alias (':' User_Alias)* | 'Runas_Alias' Runas_Alias (':' Runas_Alias)* | 'Host_Alias' Host_Alias (':' Host_Alias)* | 'Cmnd_Alias' Cmnd_Alias (':' Cmnd_Alias)* User_Alias ::= NAME '=' User_List Runas_Alias ::= NAME '=' Runas_List Host_Alias ::= NAME '=' Host_List Cmnd_Alias ::= NAME '=' Cmnd_List NAME ::= [A-Z]([A-Z][0-9]_)* Each I<alias> definition is of the form Alias_Type NAME = item1, item2, ... where I<Alias_Type> is one of C<User_Alias>, C<Runas_Alias>, C<Host_Alias>, or C<Cmnd_Alias>. A C<NAME> is a string of uppercase letters, numbers, and the underscore characters ('_'). A C<NAME> B<must> start with an uppercase letter. It is possible to put several alias definitions of the same type on a single line, joined by a colon (':'). E.g., Alias_Type NAME = item1, item2, item3 : NAME = item4, item5 The definitions of what constitutes a valid I<alias> member follow. User_List ::= User | User ',' User_List User ::= '!'* username | '!'* '%'group | '!'* '+'netgroup | '!'* User_Alias A C<User_List> is made up of one or more usernames, uids (prefixed with '#'), System groups (prefixed with '%'), netgroups (prefixed with '+') and other aliases. Each list item may be prefixed with one or more '!' operators. An odd number of '!' operators negate the value of the item; an even number just cancel each other out. Runas_List ::= Runas_User | Runas_User ',' Runas_List Runas_User ::= '!'* username | '!'* '#'uid | '!'* '%'group | '!'* +netgroup | '!'* Runas_Alias A C<Runas_List> is similar to a C<User_List> except that it can also contain uids (prefixed with '#') and instead of C<User_Alias>es it can contain C<Runas_Alias>es. Host_List ::= Host | Host ',' Host_List Host ::= '!'* hostname | '!'* ip_addr | '!'* network(/netmask)? | '!'* '+'netgroup | '!'* Host_Alias A C<Host_List> is made up of one or more hostnames, IP addresses, network numbers, netgroups (prefixed with '+') and other aliases. Again, the value of an item may be negated with the '!' operator. If you do not specify a netmask with a network number, the netmask of the host's ethernet interface(s) will be used when matching. The netmask may be specified either in dotted quad notation (e.g. 255.255.255.0) or CIDR notation (number of bits, e.g. 24). A hostname may include shell-style wildcards (see `Wildcards' section below), but unless the C<hostname> command on your machine returns the fully qualified hostname, you'll need to use the I<fqdn> option for wildcards to be useful. Cmnd_List ::= Cmnd | Cmnd ',' Cmnd_List commandname ::= filename | filename args | filename '""' Cmnd ::= '!'* commandname | '!'* directory | '!'* Cmnd_Alias A C<Cmnd_List> is a list of one or more commandnames, directories, and other aliases. A commandname is a fully qualified filename which may include shell-style wildcards (see `Wildcards' section below). A simple filename allows the user to run the command with any arguments he/she wishes. However, you may also specify command line arguments (including wildcards). Alternately, you can specify C<""> to indicate that the command may only be run B<without> command line arguments. A directory is a fully qualified pathname ending in a '/'. When you specify a directory in a C<Cmnd_List>, the user will be able to run any file within that directory (but not in any subdirectories therein). If a C<Cmnd> has associated command line arguments, then the arguments in the C<Cmnd> must match exactly those given by the user on the command line (or match the wildcards if there are any). Note that the following characters must be escaped with a '\' if they are used in command arguments: ',', ':', '=', '\'. =head2 Defaults Certain configuration options may be changed from their default values at runtime via one or more C<Default_Entry> lines. These may affect all users on any host, all users on a specific host, or just a specific user. When multiple entries match, they are applied in order. Where there are conflicting values, the last value on a matching line takes effect. Default_Type ::= 'Defaults' || 'Defaults' ':' User || 'Defaults' '@' Host Default_Entry ::= Default_Type Parameter_List Parameter ::= Parameter '=' Value || Parameter '+=' Value || Parameter '-=' Value || '!'* Parameter || Parameters may be B<flags>, B<integer> values, B<strings>, or B<lists>. Flags are implicitly boolean and can be turned off via the '!' operator. Some integer, string and list parameters may also be used in a boolean context to disable them. Values may be enclosed in double quotes (C<">) when they contain multiple words. Special characters may be escaped with a backslash (C<\>). Lists have two additional assignment operators, C<+=> and C<-=>. These operators are used to add to and delete from a list respectively. It is not an error to use the C<-=> operator to remove an element that does not exist in a list. Note that since the I<sudoers> file is parsed in order the best place to put the Defaults section is after the Host, User, and Cmnd aliases but before the user specifications. B<Flags>: =over 12 =item long_otp_prompt When validating with a One Time Password scheme (B<S/Key> or B<OPIE>), a two-line prompt is used to make it easier to cut and paste the challenge to a local window. It's not as pretty as the default but some people find it more convenient. This flag is I<@long_otp_prompt@> by default. =item ignore_dot If set, B<sudo> will ignore '.' or '' (current dir) in the C<PATH> environment variable; the C<PATH> itself is not modified. This flag is I<@ignore_dot@> by default. =item mail_always Send mail to the I<mailto> user every time a users runs B<sudo>. This flag is I<off> by default. =item mail_badpass Send mail to the I<mailto> user if the user running sudo does not enter the correct password. This flag is I<off> by default. =item mail_no_user If set, mail will be sent to the I<mailto> user if the invoking user is not in the I<sudoers> file. This flag is I<@mail_no_user@> by default. =item mail_no_host If set, mail will be sent to the I<mailto> user if the invoking user exists in the I<sudoers> file, but is not allowed to run commands on the current host. This flag is I<@mail_no_host@> by default. =item mail_no_perms If set, mail will be sent to the I<mailto> user if the invoking user allowed to use B<sudo> but the command they are trying is not listed in their I<sudoers> file entry. This flag is I<@mail_no_perms@> by default. =item tty_tickets If set, users must authenticate on a per-tty basis. Normally, B<sudo> uses a directory in the ticket dir with the same name as the user running it. With this flag enabled, B<sudo> will use a file named for the tty the user is logged in on in that directory. This flag is I<@tty_tickets@> by default. =item lecture If set, a user will receive a short lecture the first time he/she runs B<sudo>. This flag is I<@lecture@> by default. =item authenticate If set, users must authenticate themselves via a password (or other means of authentication) before they may run commands. This default may be overridden via the C<PASSWD> and C<NOPASSWD> tags. This flag is I<on> by default. =item root_sudo If set, root is allowed to run B<sudo> too. Disabling this prevents users from "chaining" B<sudo> commands to get a root shell by doing something like C<"sudo sudo /bin/sh">. This flag is I<on> by default. =item log_host If set, the hostname will be logged in the (non-syslog) B<sudo> log file. This flag is I<off> by default. =item log_year If set, the four-digit year will be logged in the (non-syslog) B<sudo> log file. This flag is I<off> by default. =item shell_noargs If set and B<sudo> is invoked with no arguments it acts as if the B<-s> flag had been given. That is, it runs a shell as root (the shell is determined by the C<SHELL> environment variable if it is set, falling back on the shell listed in the invoking user's /etc/passwd entry if not). This flag is I<off> by default. =item set_home If set and B<sudo> is invoked with the B<-s> flag the C<HOME> environment variable will be set to the home directory of the target user (which is root unless the B<-u> option is used). This effectively makes the B<-s> flag imply B<-H>. This flag is I<off> by default. =item always_set_home If set, B<sudo> will set the C<HOME> environment variable to the home directory of the target user (which is root unless the B<-u> option is used). This effectively means that the B<-H> flag is always implied. This flag is I<off> by default. =item path_info Normally, B<sudo> will tell the user when a command could not be found in their C<PATH> environment variable. Some sites may wish to disable this as it could be used to gather information on the location of executables that the normal user does not have access to. The disadvantage is that if the executable is simply not in the user's C<PATH>, B<sudo> will tell the user that they are not allowed to run it, which can be confusing. This flag is I<off> by default. =item preserve_groups By default B<sudo> will initialize the group vector to the list of groups the target user is in. When I<preserve_groups> is set, the user's existing group vector is left unaltered. The real and effective group IDs, however, are still set to match the target user. This flag is I<off> by default. =item fqdn Set this flag if you want to put fully qualified hostnames in the I<sudoers> file. I.e.: instead of myhost you would use myhost.mydomain.edu. You may still use the short form if you wish (and even mix the two). Beware that turning on I<fqdn> requires B<sudo> to make DNS lookups which may make B<sudo> unusable if DNS stops working (for example if the machine is not plugged into the network). Also note that you must use the host's official name as DNS knows it. That is, you may not use a host alias (C<CNAME> entry) due to performance issues and the fact that there is no way to get all aliases from DNS. If your machine's hostname (as returned by the C<hostname> command) is already fully qualified you shouldn't need to set I<fqdn>. This flag is I<@fqdn@> by default. =item insults If set, B<sudo> will insult users when they enter an incorrect password. This flag is I<@insults@> by default. =item requiretty If set, B<sudo> will only run when the user is logged in to a real tty. This will disallow things like C<"rsh somehost sudo ls"> since rsh(1) does not allocate a tty. Because it is not possible to turn of echo when there is no tty present, some sites may with to set this flag to prevent a user from entering a visible password. This flag is I<off> by default. =item env_editor If set, B<visudo> will use the value of the EDITOR or VISUAL environment variables before falling back on the default editor list. Note that this may create a security hole as it allows the user to run any arbitrary command as root without logging. A safer alternative is to place a colon-separated list of editors in the C<editor> variable. B<visudo> will then only use the EDITOR or VISUAL if they match a value specified in C<editor>. This flag is C<@env_editor@> by default. =item rootpw If set, B<sudo> will prompt for the root password instead of the password of the invoking user. This flag is I<off> by default. =item runaspw If set, B<sudo> will prompt for the password of the user defined by the I<runas_default> option (defaults to C<root>) instead of the password of the invoking user. This flag is I<off> by default. =item targetpw If set, B<sudo> will prompt for the password of the user specified by the B<-u> flag (defaults to C<root>) instead of the password of the invoking user. This flag is I<off> by default. =item set_logname Normally, B<sudo> will set the C<LOGNAME> and C<USER> environment variables to the name of the target user (usually root unless the B<-u> flag is given). However, since some programs (including the RCS revision control system) use C<LOGNAME> to determine the real identity of the user, it may be desirable to change this behavior. This can be done by negating the set_logname option. =item stay_setuid Normally, when B<sudo> executes a command the real and effective UIDs are set to the target user (root by default). This option changes that behavior such that the real UID is left as the invoking user's UID. In other words, this makes B<sudo> act as a setuid wrapper. This can be useful on systems that disable some potentially dangerous functionality when a program is run setuid. Note, however, that this means that sudo will run with the real uid of the invoking user which may allow that user to kill B<sudo> before it can log a failure, depending on how your OS defines the interaction between signals and setuid processes. =item env_reset If set, B<sudo> will reset the environment to only contain the following variables: C<HOME>, C<LOGNAME>, C<PATH>, C<SHELL>, C<TERM>, and C<USER> (in addition to the C<SUDO_*> variables). Of these, only C<TERM> is copied unaltered from the old environment. The other variables are set to default values (possibly modified by the value of the I<set_logname> option). If B<sudo> was compiled with the C<SECURE_PATH> option, its value will be used for the C<PATH> environment variable. Other variables may be preserved with the I<env_keep> option. =item use_loginclass If set, B<sudo> will apply the defaults specified for the target user's login class if one exists. Only available if B<sudo> is configured with the --with-logincap option. This flag is I<off> by default. =back B<Integers>: =over 12 =item passwd_tries The number of tries a user gets to enter his/her password before B<sudo> logs the failure and exits. The default is C<@passwd_tries@>. =back B<Integers that can be used in a boolean context>: =over 12 =item loglinelen Number of characters per line for the file log. This value is used to decide when to wrap lines for nicer log files. This has no effect on the syslog log file, only the file log. The default is C<@loglen@> (use 0 or negate the option to disable word wrap). =item timestamp_timeout Number of minutes that can elapse before B<sudo> will ask for a passwd again. The default is C<@timeout@>. Set this to C<0> to always prompt for a password. If set to a value less than C<0> the user's timestamp will never expire. This can be used to allow users to create or delete their own timestamps via C<sudo -v> and C<sudo -k> respectively. =item passwd_timeout Number of minutes before the B<sudo> password prompt times out. The default is C<@password_timeout@>, set this to C<0> for no password timeout. =item umask Umask to use when running the command. Negate this option or set it to 0777 to preserve the user's umask. The default is C<@sudo_umask@>. =back B<Strings>: =over 12 =item mailsub Subject of the mail sent to the I<mailto> user. The escape C<%h> will expand to the hostname of the machine. Default is C<@mailsub@>. =item badpass_message Message that is displayed if a user enters an incorrect password. The default is C<@badpass_message@> unless insults are enabled. =item timestampdir The directory in which B<sudo> stores its timestamp files. The default is F<@timedir@>. =item passprompt The default prompt to use when asking for a password; can be overridden via the B<-p> option or the C<SUDO_PROMPT> environment variable. Supports two escapes: "%u" expands to the user's login name and "%h" expands to the local hostname. The default value is C<@passprompt@>. =item runas_default The default user to run commands as if the B<-u> flag is not specified on the command line. This defaults to C<@runas_default@>. =item syslog_goodpri Syslog priority to use when user authenticates successfully. Defaults to C<@goodpri@>. =item syslog_badpri Syslog priority to use when user authenticates unsuccessfully. Defaults to C<@badpri@>. =item editor A colon (':') separated list of editors allowed to be used with B<visudo>. B<visudo> will choose the editor that matches the user's USER environment variable if possible, or the first editor in the list that exists and is executable. The default is the path to vi on your system. =back B<Strings that can be used in a boolean context>: =over 12 =item logfile Path to the B<sudo> log file (not the syslog log file). Setting a path turns on logging to a file; negating this option turns it off. =item syslog Syslog facility if syslog is being used for logging (negate to disable syslog logging). Defaults to C<@logfac@>. =item mailerpath Path to mail program used to send warning mail. Defaults to the path to sendmail found at configure time. =item mailerflags Flags to use when invoking mailer. Defaults to B<-t>. =item mailto Address to send warning and error mail to. The address should be enclosed in double quotes (C<">) to protect against sudo interpreting the C<@> sign. Defaults to C<@mailto@>. =item exempt_group Users in this group are exempt from password and PATH requirements. This is not set by default. =item verifypw This option controls when a password will be required when a user runs B<sudo> with the B<-v> flag. It has the following possible values: =over 8 =item all All the user's I<sudoers> entries for the current host must have the C<NOPASSWD> flag set to avoid entering a password. =item any At least one of the user's I<sudoers> entries for the current host must have the C<NOPASSWD> flag set to avoid entering a password. =item never The user need never enter a password to use the B<-v> flag. =item always The user must always enter a password to use the B<-v> flag. =back The default value is `all'. =item listpw This option controls when a password will be required when a user runs B<sudo> with the B<-l>. It has the following possible values: =over 8 =item all All the user's I<sudoers> entries for the current host must have the C<NOPASSWD> flag set to avoid entering a password. =item any At least one of the user's I<sudoers> entries for the current host must have the C<NOPASSWD> flag set to avoid entering a password. =item never The user need never enter a password to use the B<-l> flag. =item always The user must always enter a password to use the B<-l> flag. =back The default value is `any'. =back B<Lists that can be used in a boolean context>: =over 12 =item env_check Environment variables to be removed from the user's environment if the variable's value contains C<%> or C</> characters. This can be used to guard against printf-style format vulnerabilties in poorly-written programs. The argument may be a double-quoted, space-separated list or a single value without double-quotes. The list can be replaced, added to, deleted from, or disabled by using the C<=>, C<+=>, C<-=>, and C<!> operators respectively. The default list of environment variable to check is printed when B<sudo> is run by root with the I<-V> option. =item env_delete Environment variables to be removed from the user's environment. The argument may be a double-quoted, space-separated list or a single value without double-quotes. The list can be replaced, added to, deleted from, or disabled by using the C<=>, C<+=>, C<-=>, and C<!> operators respectively. The default list of environment variable to remove is printed when B<sudo> is run by root with the I<-V> option. =item env_keep Environment variables to be preserved in the user's environment when the I<env_reset> option is in effect. This allows fine-grained control over the environment B<sudo>-spawned processes will receive. The argument may be a double-quoted, space-separated list or a single value without double-quotes. The list can be replaced, added to, deleted from, or disabled by using the C<=>, C<+=>, C<-=>, and C<!> operators respectively. This list has no default members. =back When logging via syslog(3), B<sudo> accepts the following values for the syslog facility (the value of the B<syslog> Parameter): B<authpriv> (if your OS supports it), B<auth>, B<daemon>, B<user>, B<local0>, B<local1>, B<local2>, B<local3>, B<local4>, B<local5>, B<local6>, and B<local7>. The following syslog priorities are supported: B<alert>, B<crit>, B<debug>, B<emerg>, B<err>, B<info>, B<notice>, and B<warning>. =head2 User Specification User_Spec ::= User_list Host_List '=' Cmnd_Spec_List \ (':' User_Spec)* Cmnd_Spec_List ::= Cmnd_Spec | Cmnd_Spec ',' Cmnd_Spec_List Cmnd_Spec ::= Runas_Spec? ('NOPASSWD:' | 'PASSWD:')? Cmnd Runas_Spec ::= '(' Runas_List ')' A B<user specification> determines which commands a user may run (and as what user) on specified hosts. By default, commands are run as B<root>, but this can be changed on a per-command basis. Let's break that down into its constituent parts: =head2 Runas_Spec A C<Runas_Spec> is simply a C<Runas_List> (as defined above) enclosed in a set of parentheses. If you do not specify a C<Runas_Spec> in the user specification, a default C<Runas_Spec> of B<root> will be used. A C<Runas_Spec> sets the default for commands that follow it. What this means is that for the entry: dgb boulder = (operator) /bin/ls, /bin/kill, /usr/bin/who The user B<dgb> may run F</bin/ls>, F</bin/kill>, and F</usr/bin/lprm> -- but only as B<operator>. E.g., sudo -u operator /bin/ls. It is also possible to override a C<Runas_Spec> later on in an entry. If we modify the entry like so: dgb boulder = (operator) /bin/ls, (root) /bin/kill, /usr/bin/lprm Then user B<dgb> is now allowed to run F</bin/ls> as B<operator>, but F</bin/kill> and F</usr/bin/lprm> as B<root>. =head2 NOPASSWD and PASSWD By default, B<sudo> requires that a user authenticate him or herself before running a command. This behavior can be modified via the C<NOPASSWD> tag. Like a C<Runas_Spec>, the C<NOPASSWD> tag sets a default for the commands that follow it in the C<Cmnd_Spec_List>. Conversely, the C<PASSWD> tag can be used to reverse things. For example: ray rushmore = NOPASSWD: /bin/kill, /bin/ls, /usr/bin/lprm would allow the user B<ray> to run F</bin/kill>, F</bin/ls>, and F</usr/bin/lprm> as root on the machine rushmore as B<root> without authenticating himself. If we only want B<ray> to be able to run F</bin/kill> without a password the entry would be: ray rushmore = NOPASSWD: /bin/kill, PASSWD: /bin/ls, /usr/bin/lprm Note, however, that the C<PASSWD> tag has no effect on users who are in the group specified by the exempt_group option. By default, if the C<NOPASSWD> tag is applied to any of the entries for a user on the current host, he or she will be able to run C<sudo -l> without a password. Additionally, a user may only run C<sudo -v> without a password if the C<NOPASSWD> tag is present for all a user's entries that pertain to the current host. This behavior may be overridden via the verifypw and listpw options. =head2 Wildcards (aka meta characters): B<sudo> allows shell-style I<wildcards> to be used in pathnames as well as command line arguments in the I<sudoers> file. Wildcard matching is done via the B<POSIX> C<fnmatch(3)> routine. Note that these are I<not> regular expressions. =over 8 =item C<*> Matches any set of zero or more characters. =item C<?> Matches any single character. =item C<[...]> Matches any character in the specified range. =item C<[!...]> Matches any character B<not> in the specified range. =item C<\x> For any character "x", evaluates to "x". This is used to escape special characters such as: "*", "?", "[", and "}". =back Note that a forward slash ('/') will B<not> be matched by wildcards used in the pathname. When matching the command line arguments, however, as slash B<does> get matched by wildcards. This is to make a path like: /usr/bin/* match C</usr/bin/who> but not C</usr/bin/X11/xterm>. =head2 Exceptions to wildcard rules: The following exceptions apply to the above rules: =over 8 =item C<""> If the empty string C<""> is the only command line argument in the I<sudoers> entry it means that command is not allowed to be run with B<any> arguments. =back =head2 Other special characters and reserved words: The pound sign ('#') is used to indicate a comment (unless it occurs in the context of a user name and is followed by one or more digits, in which case it is treated as a uid). Both the comment character and any text after it, up to the end of the line, are ignored. The reserved word B<ALL> is a built in I<alias> that always causes a match to succeed. It can be used wherever one might otherwise use a C<Cmnd_Alias>, C<User_Alias>, C<Runas_Alias>, or C<Host_Alias>. You should not try to define your own I<alias> called B<ALL> as the built in alias will be used in preference to your own. Please note that using B<ALL> can be dangerous since in a command context, it allows the user to run B<any> command on the system. An exclamation point ('!') can be used as a logical I<not> operator both in an I<alias> and in front of a C<Cmnd>. This allows one to exclude certain values. Note, however, that using a C<!> in conjunction with the built in C<ALL> alias to allow a user to run "all but a few" commands rarely works as intended (see SECURITY NOTES below). Long lines can be continued with a backslash ('\') as the last character on the line. Whitespace between elements in a list as well as special syntactic characters in a I<User Specification> ('=', ':', '(', ')') is optional. The following characters must be escaped with a backslash ('\') when used as part of a word (e.g. a username or hostname): '@', '!', '=', ':', ',', '(', ')', '\'. =head1 EXAMPLES Below are example I<sudoers> entries. Admittedly, some of these are a bit contrived. First, we define our I<aliases>: # User alias specification User_Alias FULLTIMERS = millert, mikef, dowdy User_Alias PARTTIMERS = bostley, jwfox, crawl User_Alias WEBMASTERS = will, wendy, wim # Runas alias specification Runas_Alias OP = root, operator Runas_Alias DB = oracle, sybase # Host alias specification Host_Alias SPARC = bigtime, eclipse, moet, anchor :\ SGI = grolsch, dandelion, black :\ ALPHA = widget, thalamus, foobar :\ HPPA = boa, nag, python Host_Alias CUNETS = 18.104.22.168/255.255.0.0 Host_Alias CSNETS = 22.214.171.124, 126.96.36.199/24, 188.8.131.52 Host_Alias SERVERS = master, mail, www, ns Host_Alias CDROM = orion, perseus, hercules # Cmnd alias specification Cmnd_Alias DUMPS = /usr/bin/mt, /usr/sbin/dump, /usr/sbin/rdump,\ /usr/sbin/restore, /usr/sbin/rrestore Cmnd_Alias KILL = /usr/bin/kill Cmnd_Alias PRINTING = /usr/sbin/lpc, /usr/bin/lprm Cmnd_Alias SHUTDOWN = /usr/sbin/shutdown Cmnd_Alias HALT = /usr/sbin/halt, /usr/sbin/fasthalt Cmnd_Alias REBOOT = /usr/sbin/reboot, /usr/sbin/fastboot Cmnd_Alias SHELLS = /usr/bin/sh, /usr/bin/csh, /usr/bin/ksh, \ /usr/local/bin/tcsh, /usr/bin/rsh, \ /usr/local/bin/zsh Cmnd_Alias SU = /usr/bin/su Here we override some of the compiled in default values. We want B<sudo> to log via syslog(3) using the I<auth> facility in all cases. We don't want to subject the full time staff to the B<sudo> lecture, and user B<millert> need not give a password. In addition, on the machines in the I<SERVERS> C<Host_Alias>, we keep an additional local log file and make sure we log the year in each log line since the log entries will be kept around for several years. # Override built in defaults Defaults syslog=auth Defaults:FULLTIMERS !lecture Defaults:millert !authenticate Defaults@SERVERS log_year, logfile=/var/log/sudo.log The I<User specification> is the part that actually determines who may run what. root ALL = (ALL) ALL %wheel ALL = (ALL) ALL We let B<root> and any user in group B<wheel> run any command on any host as any user. FULLTIMERS ALL = NOPASSWD: ALL Full time sysadmins (B<millert>, B<mikef>, and B<dowdy>) may run any command on any host without authenticating themselves. PARTTIMERS ALL = ALL Part time sysadmins (B<bostley>, B<jwfox>, and B<crawl>) may run any command on any host but they must authenticate themselves first (since the entry lacks the C<NOPASSWD> tag). jack CSNETS = ALL The user B<jack> may run any command on the machines in the I<CSNETS> alias (the networks C<184.108.40.206>, C<220.127.116.11>, and C<18.104.22.168>). Of those networks, only C<22.214.171.124> has an explicit netmask (in CIDR notation) indicating it is a class C network. For the other networks in I<CSNETS>, the local machine's netmask will be used during matching. lisa CUNETS = ALL The user B<lisa> may run any command on any host in the I<CUNETS> alias (the class B network C<126.96.36.199>). operator ALL = DUMPS, KILL, PRINTING, SHUTDOWN, HALT, REBOOT,\ /usr/oper/bin/ The B<operator> user may run commands limited to simple maintenance. Here, those are commands related to backups, killing processes, the printing system, shutting down the system, and any commands in the directory F</usr/oper/bin/>. joe ALL = /usr/bin/su operator The user B<joe> may only su(1) to operator. pete HPPA = /usr/bin/passwd [A-z]*, !/usr/bin/passwd root The user B<pete> is allowed to change anyone's password except for root on the I<HPPA> machines. Note that this assumes passwd(1) does not take multiple usernames on the command line. bob SPARC = (OP) ALL : SGI = (OP) ALL The user B<bob> may run anything on the I<SPARC> and I<SGI> machines as any user listed in the I<OP> C<Runas_Alias> (B<root> and B<operator>). jim +biglab = ALL The user B<jim> may run any command on machines in the I<biglab> netgroup. B<Sudo> knows that "biglab" is a netgroup due to the '+' prefix. +secretaries ALL = PRINTING, /usr/bin/adduser, /usr/bin/rmuser Users in the B<secretaries> netgroup need to help manage the printers as well as add and remove users, so they are allowed to run those commands on all machines. fred ALL = (DB) NOPASSWD: ALL The user B<fred> can run commands as any user in the I<DB> C<Runas_Alias> (B<oracle> or B<sybase>) without giving a password. john ALPHA = /usr/bin/su [!-]*, !/usr/bin/su *root* On the I<ALPHA> machines, user B<john> may su to anyone except root but he is not allowed to give su(1) any flags. jen ALL, !SERVERS = ALL The user B<jen> may run any command on any machine except for those in the I<SERVERS> C<Host_Alias> (master, mail, www and ns). jill SERVERS = /usr/bin/, !SU, !SHELLS For any machine in the I<SERVERS> C<Host_Alias>, B<jill> may run any commands in the directory /usr/bin/ except for those commands belonging to the I<SU> and I<SHELLS> C<Cmnd_Aliases>. steve CSNETS = (operator) /usr/local/op_commands/ The user B<steve> may run any command in the directory /usr/local/op_commands/ but only as user operator. matt valkyrie = KILL On his personal workstation, valkyrie, B<matt> needs to be able to kill hung processes. WEBMASTERS www = (www) ALL, (root) /usr/bin/su www On the host www, any user in the I<WEBMASTERS> C<User_Alias> (will, wendy, and wim), may run any command as user www (which owns the web pages) or simply su(1) to www. ALL CDROM = NOPASSWD: /sbin/umount /CDROM,\ /sbin/mount -o nosuid\,nodev /dev/cd0a /CDROM Any user may mount or unmount a CD-ROM on the machines in the CDROM C<Host_Alias> (orion, perseus, hercules) without entering a password. This is a bit tedious for users to type, so it is a prime candidate for encapsulating in a shell script. =head1 SECURITY NOTES It is generally not effective to "subtract" commands from C<ALL> using the '!' operator. A user can trivially circumvent this by copying the desired command to a different name and then executing that. For example: bill ALL = ALL, !SU, !SHELLS Doesn't really prevent B<bill> from running the commands listed in I<SU> or I<SHELLS> since he can simply copy those commands to a different name, or use a shell escape from an editor or other program. Therefore, these kind of restrictions should be considered advisory at best (and reinforced by policy). =head1 CAVEATS The I<sudoers> file should B<always> be edited by the B<visudo> command which locks the file and does grammatical checking. It is imperative that I<sudoers> be free of syntax errors since B<sudo> will not run with a syntactically incorrect I<sudoers> file. When using netgroups of machines (as opposed to users), if you store fully qualified hostnames in the netgroup (as is usually the case), you either need to have the machine's hostname be fully qualified as returned by the C<hostname> command or use the I<fqdn> option in I<sudoers>. =head1 FILES @sysconfdir@/sudoers List of who can run what /etc/group Local groups file /etc/netgroup List of network groups =head1 SEE ALSO rsh(1), sudo(8), visudo(8), su(1), fnmatch(3).