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sudo(8) MAINTENANCE COMMANDS sudo(8)
NNNNAAAAMMMMEEEE
sudo - execute a command as the superuser
SSSSYYYYNNNNOOOOPPPPSSSSIIIISSSS
ssssuuuuddddoooo ----VVVV | ----hhhh | ----llll | ----vvvv | ----kkkk | ----ssss | ----HHHH | [ ----bbbb ] | [ ----pppp
prompt ] [ ----uuuu username/#uid] _c_o_m_m_a_n_d
DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
ssssuuuuddddoooo allows a permitted user to execute a _c_o_m_m_a_n_d as the
superuser (real and effective uid and gid are set to 0 and
root's group as set in the passwd file respectively).
ssssuuuuddddoooo determines who is an authorized user by consulting
the file _/_e_t_c_/_s_u_d_o_e_r_s. By giving ssssuuuuddddoooo the -v flag a user
can update the time stamp without running a _c_o_m_m_a_n_d_. The
password prompt itself will also time out if the password
is not entered with N minutes (again, this is defined at
installation time and defaults to 5 minutes).
If an unauthorized user executes ssssuuuuddddoooo, mail will be sent
from the user to the local authorities (defined at
installation time).
ssssuuuuddddoooo was designed to log via the 4.3 BSD _s_y_s_l_o_g(3)
facility but can log to a file instead if so desired (or
to both syslog and a file).
All preferences are defined at installation time and are
derived from the options.h and pathnames.h include files
as well as as well as the Makefile.
OOOOPPPPTTTTIIIIOOOONNNNSSSS
ssssuuuuddddoooo accepts the following command line options:
-V The -V (_v_e_r_s_i_o_n) option causes ssssuuuuddddoooo to print the
version number and exit.
-l The -l (_l_i_s_t) option will list out the allowed and
forbidden commands for the user on the current host.
-h The -h (_h_e_l_p) option causes ssssuuuuddddoooo to print the version
of ssssuuuuddddoooo and a usage message before exiting.
-v If given the -v (_v_a_l_i_d_a_t_e) option, ssssuuuuddddoooo will update
the user's timestamp file, prompting for a password if
necessary. This extends the ssssuuuuddddoooo timeout to for
another N minutes (where N is defined at installation
time and defaults to 5 minutes) but does not run a
command.
-k The -k (_k_i_l_l) option to ssssuuuuddddoooo removes the user's
timestamp file, thus requiring a password the next
time ssssuuuuddddoooo is run. This option does not require a
password and was added to allow a user to revoke ssssuuuuddddoooo
12/Jan/98 1.5.4 1
sudo(8) MAINTENANCE COMMANDS sudo(8)
permissions from a .logout file.
-b The -b (_b_a_c_k_g_r_o_u_n_d) option tells ssssuuuuddddoooo 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 command.
-p The -p (_p_r_o_m_p_t) option allows you to override the
default password prompt and use a custom one. If the
password prompt contains the %u escape, %u will be
replaced by the user's login name. Similarly, %h will
be replaced by the local hostname.
-u The -u (_u_s_e_r) option causes sudo to run the specified
command as a user other than _r_o_o_t. To specify a _u_i_d
instead of a _u_s_e_r_n_a_m_e, use "#uid".
-s The -s (_s_h_e_l_l) option runs the shell specified by the
_S_H_E_L_L environmental variable if it is set or the shell
as specified in _p_a_s_s_w_d(5).
-H The -H (_H_O_M_E) option sets the _H_O_M_E environmental
variable to the homedir of the target user (root by
default) as specified in _p_a_s_s_w_d(5).
-- The -- flag indicates that ssssuuuuddddoooo should stop processing
command line arguments. It is most useful in
conjunction with the -s flag.
RRRREEEETTTTUUUURRRRNNNN VVVVAAAALLLLUUUUEEEESSSS
ssssuuuuddddoooo quits with an exit value of 1 if there is a
configuration/permission problem or if ssssuuuuddddoooo cannot execute
the given command. In the latter case the error string is
printed to stderr via _p_e_r_r_o_r(3). If ssssuuuuddddoooo cannot _s_t_a_t(2)
one or more entries in the user's PATH the error is
printed on stderr via _p_e_r_r_o_r(3). (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
_s_t_a_t(3) to return "permission denied" is if you are
running an automounter and one of the directories in your
PATH is on a machine that is currently unreachable.
SSSSEEEECCCCUUUURRRRIIIITTTTYYYY NNNNOOOOTTTTEEEESSSS
ssssuuuuddddoooo 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 ssssuuuuddddoooo runs.
To combat this the LD_*, SHLIB_PATH (HP-UX only), LIBPATH
(AIX only), and _RLD_* environmental variables are removed
from the environment passed on to all commands executed.
ssssuuuuddddoooo will also remove the IFS, ENV, BASH_ENV and KRB_CONF
variables as they too can pose a threat.
To prevent command spoofing, ssssuuuuddddoooo checks "." and "" (both
12/Jan/98 1.5.4 2
sudo(8) MAINTENANCE COMMANDS sudo(8)
denoting current 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 environmental
variable is _n_o_t modified and is passed unchanged to the
program that ssssuuuuddddoooo executes.
For security reasons, if your OS supports shared
libraries, ssssuuuuddddoooo should always be statically linked unless
the dynamic loader disables user-defined library search
paths for setuid programs. (Most modern dynamic loaders
do this.)
ssssuuuuddddoooo will check the ownership of its timestamp directory
(_/_v_a_r_/_r_u_n_/_s_u_d_o or _/_t_m_p_/_._o_d_u_s by default) and ignore the
directory's contents if it is not owned by root and only
read, writable, and executable by root. On systems that
allow users to give files away to root (via chown), if the
timestamp directory is located in a directory writable by
anyone (ie: _/_t_m_p), it is possible for a user to create the
timestamp directory before ssssuuuuddddoooo is run. However, because
ssssuuuuddddoooo checks the ownership and mode of the directory, 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 (_/_v_a_r_/_a_d_m_/_s_u_d_o for instance).
sudo will not honor timestamp files set far in the future.
Timestamp files with a date greater than current_time + 2
* TIMEOUT will be ignored and sudo will log the anomaly.
This is done to keep a user from creating his/her own
timestamp file with a bogus date.
FFFFIIIILLLLEEEESSSS
/etc/sudoers file of authorized users.
EEEENNNNVVVVIIIIRRRROOOONNNNMMMMEEEENNNNTTTT VVVVAAAARRRRIIIIAAAABBBBLLLLEEEESSSS
PATH Set to a sane value if SECURE_PATH is set
SHELL Used to determine shell to run with -s option
HOME In -s mode, set to homedir of root (or runas user)
if built with the SHELL_SETS_HOME option
SUDO_PROMPT Replaces the default password prompt
SUDO_COMMAND Set to the command run by sudo
SUDO_USER Set to the login of the user who invoked sudo
SUDO_UID Set to the uid of the user who invoked sudo
SUDO_GID Set to the gid of the user who invoked sudo
SUDO_PS1 If set, PS1 will be set to its value
AAAAUUUUTTTTHHHHOOOORRRRSSSS
Many people have worked on ssssuuuuddddoooo over the years, this
12/Jan/98 1.5.4 3
sudo(8) MAINTENANCE COMMANDS sudo(8)
version consists of code written primarily by:
Jeff Nieusma
David Hieb
Todd Miller
Chris Jepeway
See the HISTORY file in the ssssuuuuddddoooo distribution for more
details.
Please send all bugs, comments, and changes to sudo-
bugs@courtesan.com.
DDDDIIIISSSSCCCCLLLLAAAAIIIIMMMMEEEERRRR
This program is distributed in the hope that it will be
useful, but WITHOUT ANY WARRANTY; without even the implied
warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE. See the GNU General Public License for more
details.
You should have received a copy of the GNU General Public
License along with this program; if not, write to the Free
Software Foundation, Inc., 675 Mass Ave, Cambridge, MA
02139, USA.
CCCCAAAAVVVVEEEEAAAATTTTSSSS
There is no easy way to prevent a user from gaining a root
shell if that user has access to commands allow shell
escapes.
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 ssssuuuuddddoooo can expose the same kernel
bugs that make setuid shell scripts unsafe on some
operating systems.
SSSSEEEEEEEE AAAALLLLSSSSOOOO
_s_u_d_o_e_r_s(5), _v_i_s_u_d_o(8), _s_u(1).
12/Jan/98 1.5.4 4
sudo(8) MAINTENANCE COMMANDS sudo(8)
12/Jan/98 1.5.4 5
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