=cut
-Copyright (c) 1994-1996,1998-2004 Todd C. Miller <Todd.Miller@courtesan.com>
+Copyright (c) 1994-1996, 1998-2005, 2007
+ Todd C. Miller <Todd.Miller@courtesan.com>
Permission to use, copy, modify, and distribute this software for any
purpose with or without fee is hereby granted, provided that the above
Agency (DARPA) and Air Force Research Laboratory, Air Force
Materiel Command, USAF, under agreement number F39502-99-1-0512.
-$Sudo: sudoers.pod,v 1.96 2004/09/06 20:45:27 millert Exp $
+$Sudo: sudoers.pod,v 1.95.2.20 2007/08/27 19:52:28 millert Exp $
=pod
=head1 NAME
may run what).
When multiple entries match for a user, they are applied in order.
-Where there are conflicting values, the last match is used (which
-is not necessarily the most specific match).
+Where there are multiple matches, the last match is used (which is
+not necessarily the most specific match).
The I<sudoers> grammar will be described below in Extended Backus-Naur
Form (EBNF). Don't despair if you don't know what EBNF is; it is
expressions. Do not, however, confuse them with "wildcard"
characters, which have different meanings.
-=over 8
+=over 4
=item C<?>
it can contain C<Runas_Alias>es. Note that usernames and groups
are matched as strings. In other words, two users (groups) with
the same uid (gid) are considered to be distinct. If you wish to
-match all usernames with the same uid (e.g. root and toor), you
+match all usernames with the same uid (e.g.E<nbsp>root and toor), you
can use a uid instead (#0 in the example given).
Host_List ::= Host |
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 the L<Wildcards> section below),
+If you do not specify a netmask along with the network number,
+B<sudo> will query each of the local host's network interfaces and,
+if the network number corresponds to one of the hosts's network
+interfaces, the corresponding netmask will be used. The netmask
+may be specified either in standard IP address notation
+(e.g.E<nbsp>255.255.255.0 or ffff:ffff:ffff:ffff::),
+or CIDR notation (number of bits, e.g.E<nbsp>24 or 64). A hostname may
+include shell-style wildcards (see the L<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.
+qualified hostname, you'll need to use the I<fqdn> option for
+wildcards to be useful.
Cmnd_List ::= Cmnd |
Cmnd ',' Cmnd_List
specific user, or commands being run as a specific user.
Default_Type ::= 'Defaults' |
- 'Defaults' '@' Host |
- 'Defaults' ':' User |
- 'Defaults' '>' RunasUser
+ 'Defaults' '@' Host_List |
+ 'Defaults' ':' User_List |
+ 'Defaults' '>' Runas_List
Default_Entry ::= Default_Type Parameter_List
It is not an error to use the C<-=> operator to remove an element
that does not exist in a list.
-B<Flags>:
+See L</"SUDOERS OPTIONS"> for a list of supported Defaults parameters.
-=over 12
+=head2 User Specification
-=item long_otp_prompt
+ User_Spec ::= User_List Host_List '=' Cmnd_Spec_List \
+ (':' Host_List '=' Cmnd_Spec_List)*
-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.
+ Cmnd_Spec_List ::= Cmnd_Spec |
+ Cmnd_Spec ',' Cmnd_Spec_List
-=item ignore_dot
+ Cmnd_Spec ::= Runas_Spec? Tag_Spec* Cmnd
-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. Currently, while it is possible
-to set I<ignore_dot> in I<sudoers>, its value is not used. This option
-should be considered read-only (it will be fixed in a future version
-of B<sudo>).
+ Runas_Spec ::= '(' Runas_List ')'
-=item mail_always
+ Tag_Spec ::= ('NOPASSWD:' | 'PASSWD:' | 'NOEXEC:' | 'EXEC:' |
+ 'SETENV:' | 'NOSETENV:')
-Send mail to the I<mailto> user every time a users runs B<sudo>.
-This flag is I<off> by default.
+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.
-=item mail_badpass
+Let's break that down into its constituent parts:
-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.
+=head2 Runas_Spec
-=item mail_no_user
+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:
-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.
+ dgb boulder = (operator) /bin/ls, /bin/kill, /usr/bin/lprm
-=item mail_no_host
+The user B<dgb> may run F</bin/ls>, F</bin/kill>, and
+F</usr/bin/lprm> -- but only as B<operator>. E.g.,
-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.
+ $ sudo -u operator /bin/ls.
-=item mail_no_perms
+It is also possible to override a C<Runas_Spec> later on in an
+entry. If we modify the entry like so:
-If set, mail will be sent to the I<mailto> user if the invoking
-user is allowed to use B<sudo> but the command they are trying is not
-listed in their I<sudoers> file entry or is explicitly denied.
-This flag is I<@mail_no_perms@> by default.
+ dgb boulder = (operator) /bin/ls, (root) /bin/kill, /usr/bin/lprm
-=item tty_tickets
+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>.
-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.
+=head2 Tag_Spec
-=item authenticate
+A command may have zero or more tags associated with it. There are
+six possible tag values, C<NOPASSWD>, C<PASSWD>, C<NOEXEC>, C<EXEC>,
+C<SETENV> and C<NOSETENV>.
+Once a tag is set on a C<Cmnd>, subsequent C<Cmnd>s in the
+C<Cmnd_Spec_List>, inherit the tag unless it is overridden by the
+opposite tag (i.e.: C<PASSWD> overrides C<NOPASSWD> and C<NOEXEC>
+overrides C<EXEC>).
-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.
+=head3 NOPASSWD and PASSWD
-=item root_sudo
+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:
-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">. Note, however, that turning off I<root_sudo>
-will also prevent root and from running B<sudoedit>.
-Disabling I<root_sudo> provides no real additional security; it
-exists purely for historical reasons.
-This flag is I<@root_sudo@> by default.
+ ray rushmore = NOPASSWD: /bin/kill, /bin/ls, /usr/bin/lprm
-=item log_host
+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:
-If set, the hostname will be logged in the (non-syslog) B<sudo> log file.
-This flag is I<off> by default.
+ ray rushmore = NOPASSWD: /bin/kill, PASSWD: /bin/ls, /usr/bin/lprm
-=item log_year
+Note, however, that the C<PASSWD> tag has no effect on users who are
+in the group specified by the I<exempt_group> option.
-If set, the four-digit year will be logged in the (non-syslog) B<sudo> log file.
-This flag is I<off> by default.
+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.
-=item shell_noargs
+=head3 NOEXEC and EXEC
-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.
+If B<sudo> has been compiled with I<noexec> support and the underlying
+operating system supports it, the C<NOEXEC> tag can be used to prevent
+a dynamically-linked executable from running further commands itself.
-=item set_home
+In the following example, user B<aaron> may run F</usr/bin/more>
+and F</usr/bin/vi> but shell escapes will be disabled.
-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.
+ aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
-=item always_set_home
+See the L<PREVENTING SHELL ESCAPES> section below for more details
+on how C<NOEXEC> works and whether or not it will work on your system.
-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.
+=head3 SETENV and NOSETENV
-=item path_info
+These tags override the value of the I<setenv> option on a per-command
+basis. Note that if C<SETENV> has been set for a command, any
+environment variables set on the command line way are not subject
+to the restrictions imposed by I<env_check>, I<env_delete>, or
+I<env_keep>. As such, only trusted users should be allowed to set
+variables in this manner.
-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.
+=head2 Wildcards
-=item preserve_groups
+B<sudo> allows shell-style I<wildcards> (aka meta or glob characters)
+to be used in pathnames as well as command line arguments in the
+I<sudoers> file. Wildcard matching is done via the B<POSIX>
+L<fnmatch(3)> routine. Note that these are I<not> regular expressions.
-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.
+=over 8
-=item fqdn
+=item C<*>
-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.
+Matches any set of zero or more characters.
-=item insults
+=item C<?>
-If set, B<sudo> will insult users when they enter an incorrect
-password. This flag is I<@insults@> by default.
+Matches any single character.
-=item requiretty
+=item C<[...]>
-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
-L<rsh(1)> does not allocate a tty. Because it is not possible to turn
-off 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.
+Matches any character in the specified range.
-=item env_editor
+=item C<[!...]>
-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.
+Matches any character B<not> in the specified range.
-=item rootpw
+=item C<\x>
-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.
+For any character "x", evaluates to "x". This is used to
+escape special characters such as: "*", "?", "[", and "}".
-=item runaspw
+=back
-If set, B<sudo> will prompt for the password of the user defined by the
-I<runas_default> option (defaults to C<@runas_default@>) instead of the
-password of the invoking user. This flag is I<off> by default.
+Note that a forward slash ('/') will B<not> be matched by
+wildcards used in the pathname. When matching the command
+line arguments, however, a slash B<does> get matched by
+wildcards. This is to make a path like:
-=item targetpw
+ /usr/bin/*
-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. Note that this precludes the use of a uid not listed
-in the passwd database as an argument to the B<-u> flag.
-This flag is I<off> by default.
+match F</usr/bin/who> but not F</usr/bin/X11/xterm>.
-=item set_logname
+=head2 Exceptions to wildcard rules
-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.
+The following exceptions apply to the above rules:
-=item stay_setuid
+=over 8
-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 C<"">
-=item env_reset
+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.
-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.
+=back
-=item use_loginclass
+=head2 Other special characters and reserved words
-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.
+The pound sign ('#') is used to indicate a comment (unless it is
+part of a #include directive or 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.
-=item noexec
+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.
-If set, all commands run via sudo will behave as if the C<NOEXEC>
-tag has been set, unless overridden by a C<EXEC> tag. See the
-description of I<NOEXEC and EXEC> below as well as the L<PREVENTING SHELL
-ESCAPES> section at the end of this manual. This flag is I<off> by default.
+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).
-=item ignore_local_sudoers
+Long lines can be continued with a backslash ('\') as the last
+character on the line.
-If set via LDAP, parsing of @sysconfdir@/sudoers will be skipped.
-This is intended for an Enterprises that wish to prevent the usage of local
-sudoers files so that only LDAP is used. This thwarts the efforts of
-rogue operators who would attempt to add roles to @sysconfdir@/sudoers.
-When this option is present, @sysconfdir@/sudoers does not even need to exist.
-Since this options tells sudo how to behave when no specific LDAP entries
-have been matched, this sudoOption is only meaningful for the cn=defaults
-section. This flag is I<off> by default.
+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.E<nbsp>a username or hostname):
+'@', '!', '=', ':', ',', '(', ')', '\'.
+
+=head1 SUDOERS OPTIONS
+
+B<sudo>'s behavior can be modified by C<Default_Entry> lines, as
+explained earlier. A list of all supported Defaults parameters,
+grouped by type, are listed below.
+
+B<Flags>:
+
+=over 16
+
+=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 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 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 I<@env_editor@> by
+default.
+
+=item env_reset
+
+If set, B<sudo> will reset the environment to only contain the
+LOGNAME, SHELL, USER, USERNAME and the C<SUDO_*> variables. Any
+variables in the caller's environment that match the C<env_keep>
+and C<env_check> lists are then added. The default contents of the
+C<env_keep> and C<env_check> lists are displayed when B<sudo> is
+run by root with the I<-V> option. If B<sudo> was compiled with
+the C<SECURE_PATH> option, its value will be used for the C<PATH>
+environment variable. This flag is I<on> 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 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. Currently, while it is possible
+to set I<ignore_dot> in I<sudoers>, its value is not used. This option
+should be considered read-only (it will be fixed in a future version
+of B<sudo>).
+
+=item ignore_local_sudoers
+
+If set via LDAP, parsing of @sysconfdir@/sudoers will be skipped.
+This is intended for Enterprises that wish to prevent the usage of local
+sudoers files so that only LDAP is used. This thwarts the efforts of
+rogue operators who would attempt to add roles to @sysconfdir@/sudoers.
+When this option is present, @sysconfdir@/sudoers does not even need to exist.
+Since this option tells B<sudo> how to behave when no specific LDAP entries
+have been matched, this sudoOption is only meaningful for the cn=defaults
+section. This flag is I<off> 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 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 long_otp_prompt
+
+When validating with a One Time Password (OPT) scheme such as
+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 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 B<sudo> does not
+enter the correct password. This flag is I<off> 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 is allowed to use B<sudo> but the command they are trying is not
+listed in their I<sudoers> file entry or is explicitly denied.
+This flag is I<@mail_no_perms@> 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 noexec
+
+If set, all commands run via B<sudo> will behave as if the C<NOEXEC>
+tag has been set, unless overridden by a C<EXEC> tag. See the
+description of I<NOEXEC and EXEC> below as well as the L<PREVENTING SHELL
+ESCAPES> section at the end of this manual. 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<@path_info@>
+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 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
+L<rsh(1)> does not allocate a tty. Because it is not possible to turn
+off echo when there is no tty present, some sites may wish to set
+this flag to prevent a user from entering a visible password. This
+flag is I<off> 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">. Note, however, that turning off I<root_sudo>
+will also prevent root and from running B<sudoedit>.
+Disabling I<root_sudo> provides no real additional security; it
+exists purely for historical reasons.
+This flag is I<@root_sudo@> 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<@runas_default@>) instead of the
+password of the invoking user. 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 set_logname
+
+Normally, B<sudo> will set the C<LOGNAME>, C<USER> and C<USERNAME>
+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. Note that if the I<env_reset> option has not been disabled,
+entries in the I<env_keep> list will override the value of
+I<set_logname>. This flag is I<off> by default.
+
+=item setenv
+
+Allow the user to disable the I<env_reset> option from the command
+line. Additionally, environment variables set via the command line
+are not subject to the restrictions imposed by I<env_check>,
+I<env_delete>, or I<env_keep>. As such, only trusted users should
+be allowed to set variables in this manner. 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 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. This option
+is only effective on systems with either the setreuid() or setresuid()
+function. 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. Note that this precludes the use of a uid not listed
+in the passwd database as an argument to the B<-u> flag.
+This flag is I<off> 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 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
+=over 16
=item passwd_tries
B<Integers that can be used in a boolean context>:
-=over 12
+=over 16
=item loglinelen
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 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 timestamp_timeout
Number of minutes that can elapse before B<sudo> will ask for a
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
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@>.
+=over 16
=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
+=item editor
-The directory in which B<sudo> stores its timestamp files.
-The default is F<@timedir@>.
+A colon (':') separated list of editors allowed to be used with
+B<visudo>. B<visudo> will choose the editor that matches the user's
+EDITOR 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.
-=item timestampowner
+=item mailsub
-The owner of the timestamp directory and the timestamps stored therein.
-The default is C<root>.
+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 noexec_file
+
+Path to a shared library containing dummy versions of the execv(),
+execve() and fexecve() library functions that just return an error.
+This is used to implement the I<noexec> functionality on systems that
+support C<LD_PRELOAD> or its equivalent. Defaults to F<@noexec_file@>.
=item passprompt
via the B<-p> option or the C<SUDO_PROMPT> environment variable.
The following percent (`C<%>') escapes are supported:
-=over 8
+=over 4
-=item C<%u>
+=item C<%H>
-expanded to the invoking user's login name
+expanded to the local hostname including the domain name
+(on if the machine's hostname is fully qualified or the I<fqdn>
+option is set)
+
+=item C<%h>
+
+expanded to the local hostname without the domain name
=item C<%U>
expanded to the login name of the user the command will
be run as (defaults to root)
-=item C<%h>
-
-expanded to the local hostname without the domain name
-
-=item C<%H>
+=item C<%u>
-expanded to the local hostname including the domain name
-(on if the machine's hostname is fully qualified or the I<fqdn>
-option is set)
+expanded to the invoking user's login name
=item C<%%>
-two consecutive C<%> characters are collaped into a single C<%> character
+two consecutive C<%> characters are collapsed into a single C<%> character
=back
Note that if I<runas_default> is set it B<must> occur before
any C<Runas_Alias> specifications.
-=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
+=item syslog_goodpri
-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.
+Syslog priority to use when user authenticates successfully.
+Defaults to C<@goodpri@>.
-=item noexec_file
+=item timestampdir
-Path to a shared library containing dummy versions of the execv(),
-execve() and fexecve() library functions that just return an error.
-This is used to implement the I<noexec> functionality on systems that
-support C<LD_PRELOAD> or its equivalent. Defaults to F<@noexec_file@>.
+The directory in which B<sudo> stores its timestamp files.
+The default is F<@timedir@>.
+
+=item timestampowner
+
+The owner of the timestamp directory and the timestamps stored therein.
+The default is C<root>.
=back
=over 12
+=item exempt_group
+
+Users in this group are exempt from password and PATH requirements.
+This is not set by default.
+
=item lecture
This option controls when a short lecture will be printed along with
=over 8
-=item never
+=item always
+
+Always lecture the user.
+
+=item never
+
+Never lecture the user.
+
+=item once
+
+Only lecture the user the first time they run B<sudo>.
+
+=back
+
+If no value is specified, a value of I<once> is implied.
+Negating the option results in a value of I<never> being used.
+The default value is I<@lecture@>.
+
+=item lecture_file
+
+Path to a file containing an alternate B<sudo> lecture that will
+be used in place of the standard lecture if the named file exists.
+By default, B<sudo> uses a built-in lecture.
+
+=item listpw
+
+This option controls when a password will be required when a
+user runs B<sudo> with the B<-l> 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 always
-Never lecture the user.
+The user must always enter a password to use the B<-l> flag.
-=item once
+=item any
-Only lecture the user the first time they run B<sudo>.
+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 always
+=item never
-Always lecture the user.
+The user need never enter a password to use the B<-l> flag.
=back
-If no value is specified, a value of I<once> is implied.
+If no value is specified, a value of I<any> is implied.
Negating the option results in a value of I<never> being used.
-The default value is I<@lecture@>.
-
-=item lecture_file
-
-Path to a file containing an alternate sudo lecture that will
-be used in place of the standard lecture if the named file exists.
+The default value is I<any>.
=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.
+By default, B<sudo> logs via syslog.
-=item syslog
+=item mailerflags
-Syslog facility if syslog is being used for logging (negate to
-disable syslog logging). Defaults to C<@logfac@>.
+Flags to use when invoking mailer. Defaults to B<-t>.
=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
+be enclosed in double quotes (C<">) to protect against B<sudo>
interpreting the C<@> sign. Defaults to C<@mailto@>.
-=item exempt_group
+=item syslog
-Users in this group are exempt from password and PATH requirements.
-This is not set by default.
+Syslog facility if syslog is being used for logging (negate to
+disable syslog logging). Defaults to C<@logfac@>.
=item verifypw
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
-
-If no value is specified, a value of I<all> is implied.
-Negating the option results in a value of I<never> being used.
-The default value is I<all>.
-
-=item listpw
-
-This option controls when a password will be required when a
-user runs B<sudo> with the B<-l> 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
=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.
+The user need never enter a password to use the B<-v> flag.
=back
-If no value is specified, a value of I<any> is implied.
+If no value is specified, a value of I<all> is implied.
Negating the option results in a value of I<never> being used.
-The default value is I<any>.
+The default value is I<all>.
=back
B<Lists that can be used in a boolean context>:
-=over 12
+=over 16
=item env_check
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 variables to check is printed when B<sudo> is
-run by root with the I<-V> option.
+the C<=>, C<+=>, C<-=>, and C<!> operators respectively. Regardless
+of whether the C<env_reset> option is enabled or disabled, variables
+specified by C<env_check> will be preserved in the environment if
+they pass the aforementioned check. The default list of environment
+variables to check is displayed when B<sudo> is run by root with
+the I<-V> option.
=item env_delete
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
-variables to remove is printed when B<sudo> is run by root with the
+variables to remove is displayed when B<sudo> is run by root with the
I<-V> option. Note that many operating systems will remove potentially
dangerous variables from the environment of any setuid process (such
as B<sudo>).
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.
+C<!> operators respectively. The default list of variables to keep
+is displayed when B<sudo> is run by root with the I<-V> option.
=back
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 \
- (':' Host_List '=' Cmnd_Spec_List)*
-
- Cmnd_Spec_List ::= Cmnd_Spec |
- Cmnd_Spec ',' Cmnd_Spec_List
-
- Cmnd_Spec ::= Runas_Spec? Tag_Spec* Cmnd
-
- Runas_Spec ::= '(' Runas_List ')'
-
- Tag_Spec ::= ('NOPASSWD:' | 'PASSWD:' | 'NOEXEC:' | 'EXEC:')
-
-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/lprm
-
-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 Tag_Spec
-
-A command may have zero or more tags associated with it. There are
-four possible tag values, C<NOPASSWD>, C<PASSWD>, C<NOEXEC>, C<EXEC>.
-Once a tag is set on a C<Cmnd>, subsequent C<Cmnd>s in the
-C<Cmnd_Spec_List>, inherit the tag unless it is overridden by the
-opposite tag (ie: C<PASSWD> overrides C<NOPASSWD> and C<EXEC>
-overrides C<NOEXEC>).
-
-=head3 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.
-
-=head3 NOEXEC and EXEC
-
-If sudo has been compiled with I<noexec> support and the underlying
-operating system support it, the C<NOEXEC> tag can be used to prevent
-a dynamically-linked executable from running further commands itself.
-
-In the following example, user B<aaron> may run F</usr/bin/more>
-and F</usr/bin/vi> but shell escapes will be disabled.
-
- aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
-
-See the L<PREVENTING SHELL ESCAPES> section below for more details
-on how I<noexec> works and whether or not it will work on your system.
-
-=head2 Wildcards
-
-B<sudo> allows shell-style I<wildcards> (aka meta or glob characters)
-to be used in pathnames as well as command line arguments in the
-I<sudoers> file. Wildcard matching is done via the B<POSIX>
-L<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, a slash B<does> get matched by
-wildcards. This is to make a path like:
-
- /usr/bin/*
-
-match F</usr/bin/who> but not F</usr/bin/X11/xterm>.
-
-WARNING: a pathname with wildcards will B<not> match a user command
-that consists of a relative path. In other words, given the
-following I<sudoers> entry:
-
- billy workstation = /usr/bin/*
-
-user billy will be able to run any command in /usr/bin as root, such
-as F</usr/bin/w>. The following two command will be allowed (the first
-assumes that F</usr/bin> is in the user's path):
-
- $ sudo w
- $ sudo /usr/bin/w
-
-However, this will not:
-
- $ cd /usr/bin
- $ sudo ./w
-
-For this reason you should only B<grant> access to commands using
-wildcards and never B<restrict> access using them. This limitation
-will be removed in a future version of B<sudo>.
-
-=head2 Exceptions to wildcard rules
+=head1 FILES
-The following exceptions apply to the above rules:
+=over 4
-=over 8
+=item F<@sysconfdir@/sudoers>C< >
+List of who can run what
-=item C<"">
+=item F</etc/group>C< >
+Local groups file
-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.
+=item F</etc/netgroup>C< >
+List of network groups
=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 FILES
-
- @sysconfdir@/sudoers List of who can run what
- /etc/group Local groups file
- /etc/netgroup List of network groups
-
=head1 EXAMPLES
Since the I<sudoers> file is parsed in a single pass, order is
/usr/local/bin/tcsh, /usr/bin/rsh, \
/usr/local/bin/zsh
Cmnd_Alias SU = /usr/bin/su
+ Cmnd_Alias PAGERS = /usr/bin/more, /usr/bin/pg, /usr/bin/less
Here we override some of the compiled in default values. We want
B<sudo> to log via L<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, user B<millert> need not give a password, and we don't
-want to reset the C<LOGNAME> or C<USER> environment variables when
-running commands as root. Additionally, 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.
+want to reset the C<LOGNAME>, C<USER> or C<USERNAME> environment
+variables when running commands as root. Additionally, 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. Lastly, we
+disable shell escapes for the commands in the PAGERS C<Cmnd_Alias>
+(F</usr/bin/more>, F</usr/bin/pg> and F</usr/bin/less>).
# Override built-in defaults
Defaults syslog=auth
Defaults:FULLTIMERS !lecture
Defaults:millert !authenticate
Defaults@SERVERS log_year, logfile=/var/log/sudo.log
+ Defaults!PAGERS noexec
The I<User specification> is the part that actually determines who may
run what.
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.
+B<sudo> knows that "biglab" is a netgroup due to the '+' prefix.
+secretaries ALL = PRINTING, /usr/bin/adduser, /usr/bin/rmuser
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
+any commands in the directory F</usr/bin/> except for those commands
belonging to the I<SU> and I<SHELLS> C<Cmnd_Aliases>.
steve CSNETS = (operator) /usr/local/op_commands/
Once B<sudo> executes a program, that program is free to do whatever
it pleases, including run other programs. This can be a security
issue since it is not uncommon for a program to allow shell escapes,
-which lets a user bypass B<sudo>'s restrictions. Common programs
-that permit shell escapes include shells (obviously), editors,
-paginators, mail and terminal programs.
+which lets a user bypass B<sudo>'s access control and logging.
+Common programs that permit shell escapes include shells (obviously),
+editors, paginators, mail and terminal programs.
+
+There are two basic approaches to this problem:
+
+=over 10
+
+=item restrict
+
+Avoid giving users access to commands that allow the user to run
+arbitrary commands. Many editors have a restricted mode where shell
+escapes are disabled, though B<sudoedit> is a better solution to
+running editors via B<sudo>. Due to the large number of programs that
+offer shell escapes, restricting users to the set of programs that
+do not if often unworkable.
+
+=item noexec
Many systems that support shared libraries have the ability to
override default library functions by pointing an environment
variable (usually C<LD_PRELOAD>) to an alternate shared library.
On such systems, B<sudo>'s I<noexec> functionality can be used to
-prevent a program run by sudo from executing any other programs.
+prevent a program run by B<sudo> from executing any other programs.
Note, however, that this applies only to native dynamically-linked
executables. Statically-linked executables and foreign executables
running under binary emulation are not affected.
then B<sudo> may be able to replace the exec family of functions
in the standard library with its own that simply return an error.
Unfortunately, there is no foolproof way to know whether or not
-I<noexec> will work at compile-time. I<Noexec> should work on
+I<noexec> will work at compile-time. I<noexec> should work on
SunOS, Solaris, *BSD, Linux, IRIX, Tru64 UNIX, MacOS X, and HP-UX
-11.x. It is known B<not> to work on AIX and UnixWare. I<Noexec>
+11.x. It is known B<not> to work on AIX and UnixWare. I<noexec>
is expected to work on most operating systems that support the
C<LD_PRELOAD> environment variable. Check your operating system's
manual pages for the dynamic linker (usually ld.so, ld.so.1, dyld,
whether or not your system is capable of supporting I<noexec> you
can always just try it out and see if it works.
-Note that disabling shell escapes is not a panacea. Programs running
-as root are still capable of many potentially hazardous operations
-(such as changing or overwriting files) that could lead to unintended
-privilege escalation. In the specific case of an editor, a safer
-approach is to give the user permission to run B<sudoedit>.
+=back
+
+Note that restricting shell escapes is not a panacea. Programs
+running as root are still capable of many potentially hazardous
+operations (such as changing or overwriting files) that could lead
+to unintended privilege escalation. In the specific case of an
+editor, a safer approach is to give the user permission to run
+B<sudoedit>.
=head1 SEE ALSO
-L<rsh(1)>, L<su(1)>, L<fnmatch(3)>, L<sudo(@mansectsu@)>, L<visudo(@mansectsu@)>
+L<rsh(1)>, L<su(1)>, L<fnmatch(3)>, L<sudo(8)>, L<visudo(8)>
=head1 CAVEATS
=head1 SUPPORT
-Commercial support is available for B<sudo>, see
-http://www.sudo.ws/sudo/support.html for details.
-
Limited free support is available via the sudo-users mailing list,
see http://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or
search the archives.
=head1 DISCLAIMER
-B<Sudo> is provided ``AS IS'' and any express or implied warranties,
+B<sudo> 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. See the LICENSE
file distributed with B<sudo> or http://www.sudo.ws/sudo/license.html
projects / debian / sudo / blobdiff