NAME
sudo - execute a command as another user
SYNOPSIS
ssuuddoo -KK | -LL | -VV | -hh | -kk | -ll | -vv
ssuuddoo [-HHPPSSbb] [-aa authtype] [-cc class|-] [-pp prompt] [-uu username|#uid]
{-ee file [...] | -ii | -ss | command}
ssuuddooeeddiitt [-SS] [-aa authtype] [-pp prompt] [-uu username|#uid] file [...]
DESCRIPTION
ssuuddoo allows a permitted user to execute a command as the superuser oranother 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 groupfile (unless the -PP option was specified). If the invoking user is
root or if the target user is the same as the invoking user, no pass-
word is required. Otherwise, ssuuddoo requires that users authenticatethemselves with a password by default (NOTE: in the default configura-
tion this is the user's password, not the root password). Once a user has been authenticated, a timestamp is updated and the user may thenuse sudo without a password for a short period of time (5 minutes
unless overridden in sudoers).
When invoked as ssuuddooeeddiitt, the -ee option (described below), is implied.
ssuuddoo determines who is an authorized user by consulting the file /pri-
vate/etc/sudoers. By giving ssuuddoo the -vv 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 0 minutes(unless overridden via sudoers).
If a user who is not listed in the sudoers file tries to run a command
via ssuuddoo, mail is sent to the proper authorities, as defined at config-
ure time or in the sudoers file (defaults to root). Note that the mail
will not be sent if an unauthorized user tries to run sudo with the -ll
or -vv flags. This allows users to determine for themselves whether or
not they are allowed to use ssuuddoo. If ssuuddoo is run by root and the SUDOUSER environment variable is set, ssuuddoo will use this value to determine who the actual user is. This canbe used by a user to log commands through sudo even when a root shell
has been invoked. It also allows the -ee 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
SUDOUSER. ssuuddoo can log both successful and unsuccessful attempts (as well as errors) to syslog(3), a log file, or both. By default ssuuddoo will logvia syslog(3) but this is changeable at configure time or via the sudo-
ers file. OOPPTTIIOONNSS ssuuddoo accepts the following command line options:-H The -HH (HOME) option sets the HOME environment variable to the
homedir of the target user (root by default) as specified in passwd(5). By default, ssuuddoo does not modify HOME (see sethome andalwayssethome in sudoers(5)).
-K The -KK (sure kill) option is like -kk except that it removes the
user's timestamp entirely. Like -kk, this option does not require a
password.-L The -LL (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).-P The -PP (preserve group vector) option causes ssuuddoo to preserve the
invoking user's group vector unaltered. By default, ssuuddoo will ini-
tialize 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.-S The -SS (stdin) option causes ssuuddoo to read the password from the
standard input instead of the terminal device.-V The -VV (version) option causes ssuuddoo to print the version number and
exit. If the invoking user is already root the -VV option will
print out a list of the defaults ssuuddoo was compiled with as well as the machine's local network addresses.-a The -aa (authentication type) option causes ssuuddoo to use the speci-
fied authentication type when validating the user, as allowed by /etc/login.conf. The system administrator may specify a list ofsudo-specific authentication methods by adding an "auth-sudo" entry
in /etc/login.conf. This option is only available on systems that support BSD authentication where ssuuddoo has been configured with the-with-bsdauth option.
-b The -bb (background) option tells ssuuddoo to run the given command in
the background. Note that if you use the -bb option you cannot use
shell job control to manipulate the process.-c The -cc (class) option causes ssuuddoo to run the specified command with
resources limited by the specified login class. The class argumentcan be either a class name as defined in /etc/login.conf, or a sin-
gle '-' character. Specifying a class of - indicates that the com-
mand 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 ssuuddoo command must be run from a shell that is already root. This option is only available on systems with BSD login classes where ssuuddoo hasbeen configured with the -with-logincap option.
-e The -ee (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 "sudoedit" is used when consulting the sudoers file. If
the user is authorized by sudoers the following steps are taken:
1. Temporary copies are made of the files to be edited with the owner set to the invoking user. 2. The editor specified by the VISUAL or EDITOR environment variables is run to edit the temporary files. If neither VISUAL nor EDITOR are set, the program listed in the editorsudoers variable is used.
3. If they have been modified, the temporary files are copied back to their original location and the temporary versions are removed. If the specified file does not exist, it will be created. Note that unlike most commands run by ssuuddoo, the editor is run with the invoking user's environment unmodified. If, for some reason, ssuuddoo is unable to update a file with its edited version, the user will receive a warning and the edited copy will remain in a temporary file.-h The -hh (help) option causes ssuuddoo to print a usage message and exit.
-i The -ii (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 - to
tell the shell to run as a login shell. ssuuddoo attempts to change tothat user's home directory before running the shell. It also ini-
tializes the environment, leaving TERM unchanged, setting HOME,SHELL, USER, LOGNAME, and PATH, and unsetting all other environment
variables. Note that because the shell to use is determined beforethe sudoers file is parsed, a runasdefault setting in sudoers will
specify the user to run the shell as but will not affect which shell is actually run.-k The -kk (kill) option to ssuuddoo invalidates the user's timestamp by
setting the time on it to the epoch. The next time ssuuddoo is run a password will be required. This option does not require a password and was added to allow a user to revoke ssuuddoo permissions from a .logout file.-l The -ll (list) option will list out the allowed (and forbidden) com-
mands for the user on the current host.-p The -pp (prompt) option allows you to override the default password
prompt and use a custom one. The following percent (`%') escapes
are supported:%u expanded to the invoking user's login name
%U expanded to the login name of the user the command will be
run as (defaults to root)%h expanded to the local hostname without the domain name
%H expanded to the local hostname including the domain name
(on if the machine's hostname is fully qualified or thefqdn sudoers option is set)
%% two consecutive % characters are collapsed into a single %
character-s The -ss (shell) option runs the shell specified by the SHELL envi-
ronment variable if it is set or the shell as specified in passwd(5).-u The -uu (user) option causes ssuuddoo to run the specified command as a
user other than root. To specify a uid instead of a username, use#uid. Note that if the targetpw Defaults option is set (see sudo-
ers(5)) it is not possible to run commands with a uid not listed in the password database.-v If given the -vv (validate) option, ssuuddoo will update the user's
timestamp, prompting for the user's password if necessary. This extends the ssuuddoo timeout for another 5 minutes (or whatever thetimeout is set to in sudoers) but does not run a command.
- The -- flag indicates that ssuuddoo should stop processing command line
arguments. It is most useful in conjunction with the -ss flag.
RETURN VALUES
Upon successful execution of a program, the return value from ssuuddoo will simply be the return value of the program that was executed.Otherwise, ssuuddoo quits with an exit value of 1 if there is a configura-
tion/permission problem or if ssuuddoo cannot execute the given command.In the latter case the error string is printed to stderr. If ssuuddoo can-
not stat(2) one or more entries in the user's PATH 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 forstat(2) to return "permission denied" is if you are running an auto-
mounter and one of the directories in your PATH is on a machine that is currently unreachable. SSEECCUURRIITTYY NNOOTTEESS ssuuddoo 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 ssuuddoo runs. To combat this the LD*, RLD*,SHLIBPATH (HP-UX only), and LIBPATH (AIX only) environment variables
are removed from the environment passed on to all commands executed.ssuuddoo will also remove the IFS, CDPATH, ENV, BASHENV, KRBCONF, KRB-
CONFDIR, KRBTKFILE, KRB5CONFIG, LOCALDOMAIN, RESOPTIONS, HOSTALIASES,
NLSPATH, PATHLOCALE, TERMINFO, TERMINFODIRS and TERMPATH variables as they too can pose a threat. If the TERMCAP variable is set and is a pathname, it too is ignored. Additionally, if the LC* or LANGUAGEvariables contain the / or % characters, they are ignored. Environment
variables with a value beginning with () are also removed as they could be interpreted as bbaasshh functions. If ssuuddoo has been compiled with SecurID support, the VARACE, USRACE and DLCACE variables are clearedas well. The list of environment variables that ssuuddoo clears is con-
tained in the output of sudo -V when run as root.
To prevent command spoofing, ssuuddoo checks "." and "" (both denoting cur-
rent directory) last when searching for a command in the user's PATH (if one or both are in the PATH). Note, however, that the actual PATH environment variable is not modified and is passed unchanged to the program that ssuuddoo executes. For security reasons, if your OS supports shared libraries and does notdisable user-defined library search paths for setuid programs (most
do), you should either use a linker option that disables this behavior or link ssuuddoo statically.ssuuddoo will check the ownership of its timestamp directory (/var/db/sudo
by default) and ignore the directory's contents if it is not owned byroot 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 ssuuddoo is run. However, because ssuuddoo checks the ownership and mode of the directory and its contents, the only damage that can be done is to "hide" 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/db/sudo with the appropriate owner (root) and permissions (0700)
in the system startup files. ssuuddoo will not honor timestamps set far in the future. Timestamps witha date greater than currenttime + 2 * TIMEOUT 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 ssuuddoo will only log the command it explicitly runs. Ifa user runs a command such as sudo su or sudo sh, subsequent commands
run from that shell will not be logged, nor will ssuuddoo'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 ssuuddoo to verify that the command does not inadvertently give the user an effective root shell. ENVIRONMENT ssuuddoo utilizes the following environment variables:EDITOR Default editor to use in -e (sudoedit) mode if
VISUAL is not setHOME In -s or -H mode (or if sudo was configured with
the -enable-shell-sets-home option), set to
homedir of the target userPATH Set to a sane value if sudo was configured with
the -with-secure-path option
SHELL Used to determine shell to run with -s option
SUDOPROMPT Used as the default password promptSUDOCOMMAND Set to the command run by sudo
SUDOUSER Set to the login of the user who invoked sudo
SUDOUID Set to the uid of the user who invoked sudo
SUDOGID Set to the gid of the user who invoked sudo
SUDOPS1 If set, PS1 will be set to its valueUSER Set to the target user (root unless the -u option
is specified)VISUAL Default editor to use in -e (sudoedit) mode
FILES/private/etc/sudoers List of who can run what
/var/db/sudo Directory containing timestamps
EEXXAAMMPPLLEESSNote: the following examples assume suitable sudoers(5) entries.
To get a file listing of an unreadable directory:$ sudo ls /usr/local/protected
To list the home directory of user yazza on a machine where the file system holding ~yazza is not exported as root:$ sudo -u yazza ls ~yazza
To edit the index.html file as user www:$ sudo -u www vi ~www/htdocs/index.html
To shutdown a machine:$ sudo shutdown -r +15 "quick reboot"
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 cd and file
redirection work.$ sudo sh -c "cd /home ; du -s * | sort -rn > USAGE"
SEE ALSO
grep(1), su(1), stat(2), sudoers(5), passwd(5), visudo(8)
AUTHORS Many people have worked on ssuuddoo over the years; this version consists of code written primarily by: Todd Miller Chris Jepeway See the HISTORY file in the ssuuddoo distribution or visithttp://www.sudo.ws/sudo/history.html for a short history of ssuuddoo.
CCAAVVEEAATTSS There is no easy way to prevent a user from gaining a root shell if that user is allowed to run arbitrary commands via ssuuddoo. Also, many programs (such as editors) allow the user to run commands via shell escapes, thus avoiding ssuuddoo's checks. However, on most systems it is possible to prevent shell escapes with ssuuddoo's noexec functionality.See the sudoers(5) manual for details.
It is not meaningful to run the cd command directly via sudo, e.g.
$ sudo cd /usr/local/protected
since when whe command exits the parent process (your shell) will stillbe the same. Please see the EXAMPLES section for more information.
If users have sudo ALL 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 ssuuddoo can expose the same kernel bugs that make setuid shell scripts unsafe on some operating systems (if your OS has a /dev/fd/ directory, setuid shell scripts are generally safe).BUGS
If you feel you have found a bug in ssuuddoo, please submit a bug report athttp://www.sudo.ws/sudo/bugs/
SSUUPPPPOORRTT Commercial support is available for ssuuddoo, seehttp://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. DDIISSCCLLAAIIMMEERR SSuuddoo is provided ``AS IS'' and any express or implied warranties,including, but not limited to, the implied warranties of merchantabil-
ity and fitness for a particular purpose are disclaimed. See the LICENSE file distributed with ssuuddoo orhttp://www.sudo.ws/sudo/license.html for complete details.
1.6.8p12 June 20, 2005 SUDO(8)