Copyright (c) 1994-1996,1998-2003 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
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Sponsored in part by the Defense Advanced Research Projects
Agency (DARPA) and Air Force Research Laboratory, Air Force
Materiel Command, USAF, under agreement number F39502-99-1-0512.

$Sudo: sudo.pod,v 1.73 2004/09/08 18:34:38 millert Exp $
Automatically generated by Pod::Man v1.37, Pod::Parser v1.14

Standard preamble:
========================================================================

\\$1

.. ..

..

.. Set up some character translations and predefined strings. \*(-- will
give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
double quote, and \*(R" will give a right double quote. | will give a
real vertical bar. \*(C+ will give a nicer C++. Capital omega is used to
do unbreakable dashes and therefore won't be available. \*(C` and \*(C'
expand to `' in nroff, nothing in troff, for use with C<>.
.tr \(*W-|\(bv\*(Tr . ds -- \(*W- . ds PI pi . if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch . if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch . ds L" "" . ds R" "" . ds C` . ds C' 'br\} . ds -- \|\(em\| . ds PI \(*p . ds L" `` . ds R" '' 'br\}
If the F register is turned on, we'll generate index entries on stderr for
titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and index
entries marked with X<> in POD. Of course, you'll have to process the
output yourself in some meaningful fashion.
. de IX . tm Index:\\$1\t\\n%\t"\\$2" .. . nr % 0 . rr F .\}
For nroff, turn off justification. Always turn off hyphenation; it makes
way too many mistakes in technical documents.

Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
Fear. Run. Save yourself. No user-serviceable parts.
. \" fudge factors for nroff and troff . ds #H 0 . ds #V .8m . ds #F .3m . ds #[ \f1 . ds #] .\} . ds #H ((1u-(\\\\n(.fu%2u))*.13m) . ds #V .6m . ds #F 0 . ds #[ \& . ds #] \& .\} . \" simple accents for nroff and troff . ds ' \& . ds ` \& . ds ^ \& . ds , \& . ds ~ ~ . ds / .\} . ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u" . ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u' . ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u' . ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u' . ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u' . ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u' .\} . \" troff and (daisy-wheel) nroff accents . \" corrections for vroff . \" for low resolution devices (crt and lpr) \{\ . ds : e . ds 8 ss . ds o a . ds d- d\h'-1'\(ga . ds D- D\h'-1'\(hy . ds th \o'bp' . ds Th \o'LP' . ds ae ae . ds Ae AE .\} ========================================================================

Title "SUDO 8" sudo, sudoedit - execute a command as another user Header "SYNOPSIS" \fBsudo -K | -L | -V | -h | -k | -l | -v

\fBsudo [-HPSb] [-a auth_type] [-c class|-] [-p prompt] [-u username|#uid] {-e file [...] | -i | -s | command}

\fBsudoedit [-S] [-a auth_type] [-p prompt] [-u username|#uid] file [...]

Header "DESCRIPTION" \fBsudo allows a permitted user to execute a command as the superuser or another user, as specified in the sudoers file. The real and effective uid and gid are set to match those of the target user as specified in the passwd file and the group vector is initialized based on the group file (unless the -P option was specified). If the invoking user is root or if the target user is the same as the invoking user, no password is required. Otherwise, \fBsudo requires that users authenticate themselves with a password by default (\s-1NOTE:\s0 in the default configuration this is the user's password, not the root password). Once a user has been authenticated, a timestamp is updated and the user may then use sudo without a password for a short period of time (\*(C`5\*(C' minutes unless overridden in sudoers).

When invoked as sudoedit, the -e option (described below), is implied.

\fBsudo determines who is an authorized user by consulting the file \fI/etc/sudoers. By giving sudo the -v flag a user can update the time stamp without running a command. The password prompt itself will also time out if the user's password is not entered within \*(C`5\*(C' minutes (unless overridden via \fIsudoers).

If a user who is not listed in the sudoers file tries to run a command via sudo, mail is sent to the proper authorities, as defined at configure time or in the sudoers file (defaults to \f(CW\*(C`root\*(C'). Note that the mail will not be sent if an unauthorized user tries to run sudo with the -l or -v flags. This allows users to determine for themselves whether or not they are allowed to use sudo.

If sudo is run by root and the \*(C`SUDO_USER\*(C' environment variable is set, sudo will use this value to determine who the actual user is. This can be used by a user to log commands through sudo even when a root shell has been invoked. It also allows the -e flag to remain useful even when being run via a sudo-run script or program. Note however, that the sudoers lookup is still done for root, not the user specified by \*(C`SUDO_USER\*(C'.

\fBsudo can log both successful and unsuccessful attempts (as well as errors) to syslog\|(3), a log file, or both. By default sudo will log via syslog\|(3) but this is changeable at configure time or via the sudoers file.

Header "OPTIONS" \fBsudo accepts the following command line options: Item "-H" The -H (\s-1HOME\s0) option sets the \*(C`HOME\*(C' environment variable to the homedir of the target user (root by default) as specified in passwd(5). By default, sudo does not modify \*(C`HOME\*(C' (see set_home and always_set_home in sudoers(5)). Item "-K" The -K (sure kill) option is like -k except that it removes the user's timestamp entirely. Like -k, this option does not require a password. Item "-L" The -L (list defaults) option will list out the parameters that may be set in a Defaults line along with a short description for each. This option is useful in conjunction with grep\|(1). Item "-P" The -P (preserve group vector) option causes sudo to preserve the invoking user's group vector unaltered. By default, \fBsudo will initialize the group vector to the list of groups the target user is in. The real and effective group IDs, however, are still set to match the target user. Item "-S" The -S (stdin) option causes sudo to read the password from the standard input instead of the terminal device. Item "-V" The -V (version) option causes sudo to print the version number and exit. If the invoking user is already root the -V option will print out a list of the defaults sudo was compiled with as well as the machine's local network addresses. Item "-a" The -a (authentication type) option causes sudo to use the specified authentication type when validating the user, as allowed by /etc/login.conf. The system administrator may specify a list of sudo-specific authentication methods by adding an \*(L"auth-sudo\*(R" entry in /etc/login.conf. This option is only available on systems that support \s-1BSD\s0 authentication where sudo has been configured with the --with-bsdauth option. Item "-b" The -b (background) option tells sudo to run the given command in the background. Note that if you use the -b option you cannot use shell job control to manipulate the process. Item "-c" The -c (class) option causes sudo to run the specified command with resources limited by the specified login class. The class argument can be either a class name as defined in /etc/login.conf, or a single '-' character. Specifying a class of \*(C`-\*(C' indicates that the command should be run restricted by the default login capabilities for the user the command is run as. If the class argument specifies an existing user class, the command must be run as root, or the sudo command must be run from a shell that is already root. This option is only available on systems with \s-1BSD\s0 login classes where sudo has been configured with the --with-logincap option. Item "-e" The -e (edit) option indicates that, instead of running a command, the user wishes to edit one or more files. In lieu of a command, the string \*(L"sudoedit\*(R" is used when consulting the sudoers file. If the user is authorized by sudoers the following steps are taken: Item "-h" The -h (help) option causes sudo to print a usage message and exit. Item "-i" The -i (simulate initial login) option runs the shell specified in the passwd(5) entry of the user that the command is being run as. The command name argument given to the shell begins with a \*(C`-\*(C' to tell the shell to run as a login shell. sudo attempts to change to that user's home directory before running the shell. It also initializes the environment, leaving \s-1TERM\s0 unchanged, setting \s-1HOME\s0, \s-1SHELL\s0, \s-1USER\s0, \s-1LOGNAME\s0, and \fI\s-1PATH\s0, and unsetting all other environment variables. Note that because the shell to use is determined before the sudoers file is parsed, a runas_default setting in sudoers will specify the user to run the shell as but will not affect which shell is actually run. Item "-k" The -k (kill) option to sudo invalidates the user's timestamp by setting the time on it to the epoch. The next time sudo is run a password will be required. This option does not require a password and was added to allow a user to revoke sudo permissions from a .logout file. Item "-l" The -l (list) option will list out the allowed (and forbidden) commands for the user on the current host. Item "-p" The -p (prompt) option allows you to override the default password prompt and use a custom one. The following percent (`\*(C`%\*(C'') escapes are supported: Item "-s" The -s (shell) option runs the shell specified by the \s-1SHELL\s0 environment variable if it is set or the shell as specified in passwd(5). Item "-u" The -u (user) option causes sudo to run the specified command as a user other than root. To specify a uid instead of a \fIusername, use #uid. Note that if the targetpw Defaults option is set (see sudoers(5)) it is not possible to run commands with a uid not listed in the password database. Item "-v" If given the -v (validate) option, sudo will update the user's timestamp, prompting for the user's password if necessary. This extends the sudo timeout for another \*(C`5\*(C' minutes (or whatever the timeout is set to in sudoers) but does not run a command. The -- flag indicates that sudo should stop processing command line arguments. It is most useful in conjunction with the -s flag. Header "RETURN VALUES" Upon successful execution of a program, the return value from sudo will simply be the return value of the program that was executed.

Otherwise, sudo quits with an exit value of 1 if there is a configuration/permission problem or if sudo cannot execute the given command. In the latter case the error string is printed to stderr. If sudo cannot stat\|(2) one or more entries in the user's \f(CW\*(C`PATH\*(C' an error is printed on stderr. (If the directory does not exist or if it is not really a directory, the entry is ignored and no error is printed.) This should not happen under normal circumstances. The most common reason for stat\|(2) to return \*(L"permission denied\*(R" is if you are running an automounter and one of the directories in your \*(C`PATH\*(C' is on a machine that is currently unreachable.

Header "SECURITY NOTES" \fBsudo tries to be safe when executing external commands. Variables that control how dynamic loading and binding is done can be used to subvert the program that sudo runs. To combat this the \f(CW\*(C`LD_*\*(C', \*(C`_RLD_*\*(C', \*(C`SHLIB_PATH\*(C' (\s-1HP-UX\s0 only), and \*(C`LIBPATH\*(C' (\s-1AIX\s0 only) environment variables are removed from the environment passed on to all commands executed. sudo will also remove the \*(C`IFS\*(C', \f(CW\*(C`CDPATH\*(C', \*(C`ENV\*(C', \*(C`BASH_ENV\*(C', \*(C`KRB_CONF\*(C', \*(C`KRBCONFDIR\*(C', \*(C`KRBTKFILE\*(C', \f(CW\*(C`KRB5_CONFIG\*(C', \*(C`LOCALDOMAIN\*(C', \*(C`RES_OPTIONS\*(C', \*(C`HOSTALIASES\*(C', \f(CW\*(C`NLSPATH\*(C', \*(C`PATH_LOCALE\*(C', \*(C`TERMINFO\*(C', \*(C`TERMINFO_DIRS\*(C' and \f(CW\*(C`TERMPATH\*(C' variables as they too can pose a threat. If the \f(CW\*(C`TERMCAP\*(C' variable is set and is a pathname, it too is ignored. Additionally, if the \*(C`LC_*\*(C' or \*(C`LANGUAGE\*(C' variables contain the \f(CW\*(C`/\*(C' or \*(C`%\*(C' characters, they are ignored. Environment variables with a value beginning with \*(C`()\*(C' are also removed as they could be interpreted as bash functions. If sudo has been compiled with SecurID support, the \*(C`VAR_ACE\*(C', \*(C`USR_ACE\*(C' and \f(CW\*(C`DLC_ACE\*(C' variables are cleared as well. The list of environment variables that sudo clears is contained in the output of \f(CW\*(C`sudo -V\*(C' when run as root.

To prevent command spoofing, sudo checks \*(L".\*(R" and "" (both denoting current directory) last when searching for a command in the user's \s-1PATH\s0 (if one or both are in the \s-1PATH\s0). Note, however, that the actual \*(C`PATH\*(C' environment variable is not modified and is passed unchanged to the program that sudo executes.

For security reasons, if your \s-1OS\s0 supports shared libraries and does not disable user-defined library search paths for setuid programs (most do), you should either use a linker option that disables this behavior or link sudo statically.

\fBsudo will check the ownership of its timestamp directory (/var/run/sudo by default) and ignore the directory's contents if it is not owned by root and only writable by root. On systems that allow non-root users to give away files via chown\|(2), if the timestamp directory is located in a directory writable by anyone (e.g.: /tmp), it is possible for a user to create the timestamp directory before \fBsudo is run. However, because sudo checks the ownership and mode of the directory and its contents, the only damage that can be done is to \*(L"hide\*(R" files by putting them in the timestamp dir. This is unlikely to happen since once the timestamp dir is owned by root and inaccessible by any other user the user placing files there would be unable to get them back out. To get around this issue you can use a directory that is not world-writable for the timestamps (/var/adm/sudo for instance) or create /var/run/sudo with the appropriate owner (root) and permissions (0700) in the system startup files.

\fBsudo will not honor timestamps set far in the future. Timestamps with a date greater than current_time + 2 * \*(C`TIMEOUT\*(C' will be ignored and sudo will log and complain. This is done to keep a user from creating his/her own timestamp with a bogus date on systems that allow users to give away files.

Please note that sudo will only log the command it explicitly runs. If a user runs a command such as \*(C`sudo su\*(C' or \*(C`sudo sh\*(C', subsequent commands run from that shell will not be logged, nor will sudo's access control affect them. The same is true for commands that offer shell escapes (including most editors). Because of this, care must be taken when giving users access to commands via sudo to verify that the command does not inadvertently give the user an effective root shell.

Header "ENVIRONMENT" \fBsudo utilizes the following environment variables:

.Vb 2 EDITOR Default editor to use in -e (sudoedit) mode if VISUAL is not set .Ve

.Vb 3 HOME In -s or -H mode (or if sudo was configured with the --enable-shell-sets-home option), set to homedir of the target user .Ve

.Vb 2 PATH Set to a sane value if sudo was configured with the --with-secure-path option .Ve

.Vb 1 SHELL Used to determine shell to run with -s option .Ve

.Vb 1 SUDO_PROMPT Used as the default password prompt .Ve

.Vb 1 SUDO_COMMAND Set to the command run by sudo .Ve

.Vb 1 SUDO_USER Set to the login of the user who invoked sudo .Ve

.Vb 1 SUDO_UID Set to the uid of the user who invoked sudo .Ve

.Vb 1 SUDO_GID Set to the gid of the user who invoked sudo .Ve

.Vb 1 SUDO_PS1 If set, PS1 will be set to its value .Ve

.Vb 2 USER Set to the target user (root unless the -u option is specified) .Ve

.Vb 1 VISUAL Default editor to use in -e (sudoedit) mode .Ve

Header "FILES" .Vb 2 /etc/sudoers List of who can run what /var/run/sudo Directory containing timestamps .Ve Header "EXAMPLES" Note: the following examples assume suitable sudoers(5) entries.

To get a file listing of an unreadable directory:

.Vb 1 $ sudo ls /usr/local/protected .Ve

To list the home directory of user yazza on a machine where the file system holding ~yazza is not exported as root:

.Vb 1 $ sudo -u yazza ls ~yazza .Ve

To edit the index.html file as user www:

.Vb 1 $ sudo -u www vi ~www/htdocs/index.html .Ve

To shutdown a machine:

.Vb 1 $ sudo shutdown -r +15 "quick reboot" .Ve

To make a usage listing of the directories in the /home partition. Note that this runs the commands in a sub-shell to make the \*(C`cd\*(C' and file redirection work.

.Vb 1 $ sudo sh -c "cd /home ; du -s * | sort -rn > USAGE" .Ve

Header "SEE ALSO" \fIgrep\|(1), su\|(1), stat\|(2), login_cap\|(3), sudoers(5), passwd(5), visudo(8) Header "AUTHORS" Many people have worked on sudo over the years; this version consists of code written primarily by:

.Vb 2 Todd Miller Chris Jepeway .Ve

See the \s-1HISTORY\s0 file in the sudo distribution or visit http://www.sudo.ws/sudo/history.html for a short history of sudo.

Header "CAVEATS" There is no easy way to prevent a user from gaining a root shell if that user is allowed to run arbitrary commands via sudo. Also, many programs (such as editors) allow the user to run commands via shell escapes, thus avoiding sudo's checks. However, on most systems it is possible to prevent shell escapes with sudo's \fInoexec functionality. See the sudoers(5) manual for details.

It is not meaningful to run the \*(C`cd\*(C' command directly via sudo, e.g.

.Vb 1 $ sudo cd /usr/local/protected .Ve

since when whe command exits the parent process (your shell) will still be the same. Please see the \s-1EXAMPLES\s0 section for more information.

If users have sudo \*(C`ALL\*(C' there is nothing to prevent them from creating their own program that gives them a root shell regardless of any '!' elements in the user specification.

Running shell scripts via sudo can expose the same kernel bugs that make setuid shell scripts unsafe on some operating systems (if your \s-1OS\s0 has a /dev/fd/ directory, setuid shell scripts are generally safe).

Header "BUGS" If you feel you have found a bug in sudo, please submit a bug report at http://www.sudo.ws/sudo/bugs/ Header "SUPPORT" Commercial support is available for 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.

Header "DISCLAIMER" \fBSudo is provided ``\s-1AS\s0 \s-1IS\s0'' 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 \s-1LICENSE\s0 file distributed with sudo or http://www.sudo.ws/sudo/license.html for complete details.