SUDO(1m) System Manager's Manual SUDO(1m)
NNAAMMEE
ssuuddoo, ssuuddooeeddiitt - execute a command as another user
SSYYNNOOPPSSIISS
ssuuddoo --hh | --KK | --kk | --VV
ssuuddoo --vv [--AAkknnSS] [--aa _t_y_p_e] [--gg _g_r_o_u_p] [--hh _h_o_s_t] [--pp _p_r_o_m_p_t] [--uu _u_s_e_r]
ssuuddoo --ll [--AAkknnSS] [--aa _t_y_p_e] [--gg _g_r_o_u_p] [--hh _h_o_s_t] [--pp _p_r_o_m_p_t] [--UU _u_s_e_r]
[--uu _u_s_e_r] [_c_o_m_m_a_n_d]
ssuuddoo [--AAbbEEHHnnPPSS] [--aa _t_y_p_e] [--CC _n_u_m] [--cc _c_l_a_s_s] [--gg _g_r_o_u_p] [--hh _h_o_s_t]
[--pp _p_r_o_m_p_t] [--rr _r_o_l_e] [--tt _t_y_p_e] [--uu _u_s_e_r] [VVAARR=_v_a_l_u_e] [--ii | --ss]
[_c_o_m_m_a_n_d]
ssuuddooeeddiitt [--AAkknnSS] [--aa _t_y_p_e] [--CC _n_u_m] [--cc _c_l_a_s_s] [--gg _g_r_o_u_p] [--hh _h_o_s_t]
[--pp _p_r_o_m_p_t] [--uu _u_s_e_r] file ...
DDEESSCCRRIIPPTTIIOONN
ssuuddoo allows a permitted user to execute a _c_o_m_m_a_n_d as the superuser or
another user, as specified by the security policy.
ssuuddoo supports a plugin architecture for security policies and
input/output logging. Third parties can develop and distribute their own
policy and I/O logging plugins to work seamlessly with the ssuuddoo front
end. The default security policy is _s_u_d_o_e_r_s, which is configured via the
file _/_e_t_c_/_s_u_d_o_e_r_s, or via LDAP. See the _P_l_u_g_i_n_s section for more
information.
The security policy determines what privileges, if any, a user has to run
ssuuddoo. The policy may require that users authenticate themselves with a
password or another authentication mechanism. If authentication is
required, ssuuddoo will exit if the user's password is not entered within a
configurable time limit. This limit is policy-specific; the default
password prompt timeout for the _s_u_d_o_e_r_s security policy is 5 minutes.
Security policies may support credential caching to allow the user to run
ssuuddoo again for a period of time without requiring authentication. The
_s_u_d_o_e_r_s policy caches credentials for 5 minutes, unless overridden in
sudoers(4). By running ssuuddoo with the --vv option, a user can update the
cached credentials without running a _c_o_m_m_a_n_d.
When invoked as ssuuddooeeddiitt, the --ee option (described below), is implied.
Security policies may log successful and failed attempts to use ssuuddoo. If
an I/O plugin is configured, the running command's input and output may
be logged as well.
The options are as follows:
--AA, ----aasskkppaassss
Normally, if ssuuddoo requires a password, it will read it from
the user's terminal. If the --AA (_a_s_k_p_a_s_s) option is
specified, a (possibly graphical) helper program is executed
to read the user's password and output the password to the
standard output. If the SUDO_ASKPASS environment variable is
set, it specifies the path to the helper program. Otherwise,
if sudo.conf(4) contains a line specifying the askpass
program, that value will be used. For example:
# Path to askpass helper program
Path askpass /usr/X11R6/bin/ssh-askpass
If no askpass program is available, ssuuddoo will exit with an
error.
--aa _t_y_p_e, ----aauutthh--ttyyppee=_t_y_p_e
Use the specified BSD authentication _t_y_p_e when validating the
user, if allowed by _/_e_t_c_/_l_o_g_i_n_._c_o_n_f. The system
administrator may specify a list of sudo-specific
authentication methods by adding an ``auth-sudo'' entry in
_/_e_t_c_/_l_o_g_i_n_._c_o_n_f. This option is only available on systems
that support BSD authentication.
--bb, ----bbaacckkggrroouunndd
Run the given command in the background. Note that it is not
possible to use shell job control to manipulate background
processes started by ssuuddoo. Most interactive commands will
fail to work properly in background mode.
--CC _n_u_m, ----cclloossee--ffrroomm=_n_u_m
Close all file descriptors greater than or equal to _n_u_m
before executing a command. Values less than three are not
permitted. By default, ssuuddoo will close all open file
descriptors other than standard input, standard output and
standard error when executing a command. The security policy
may restrict the user's ability to use this option. The
_s_u_d_o_e_r_s policy only permits use of the --CC option when the
administrator has enabled the _c_l_o_s_e_f_r_o_m___o_v_e_r_r_i_d_e option.
--cc _c_l_a_s_s, ----llooggiinn--ccllaassss=_c_l_a_s_s
Run the command with resource limits and scheduling priority
of the specified login _c_l_a_s_s. The _c_l_a_s_s argument can be
either a class name as defined in _/_e_t_c_/_l_o_g_i_n_._c_o_n_f, or a
single `-' character. If _c_l_a_s_s is -, the default login class
of the target user will be used. Otherwise, the command must
be run as root, or ssuuddoo must be run from a shell that is
already root. If the command is being run as a login shell,
additional _/_e_t_c_/_l_o_g_i_n_._c_o_n_f settings, such as the umask and
environment variables, will be applied if present. This
option is only available on systems with BSD login classes.
--EE, ----pprreesseerrvvee--eennvv
Indicates to the security policy that the user wishes to
preserve their existing environment variables. The security
policy may return an error if the user does not have
permission to preserve the environment.
--ee, ----eeddiitt Edit one or more files instead of running a command. In lieu
of a path name, the string "sudoedit" is used when consulting
the security policy. If the user is authorized by the
policy, 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 policy is run to edit the
temporary files. The _s_u_d_o_e_r_s policy uses the
SUDO_EDITOR, VISUAL and EDITOR environment variables
(in that order). If none of SUDO_EDITOR, VISUAL or
EDITOR are set, the first program listed in the _e_d_i_t_o_r
sudoers(4) option 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 _s_u_d_o, 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.
--gg _g_r_o_u_p, ----ggrroouupp=_g_r_o_u_p
Run the command with the primary group set to _g_r_o_u_p instead
of the primary group specified by the target user's password
database entry. The _g_r_o_u_p may be either a group name or a
numeric group ID (GID) prefixed with the `#' character (e.g.
#0 for GID 0). When running a command as a GID, many shells
require that the `#' be escaped with a backslash (`\'). If
no --uu option is specified, the command will be run as the
invoking user. In either case, the primary group will be set
to _g_r_o_u_p.
--HH, ----sseett--hhoommee
Request that the security policy set the HOME environment
variable to the home directory specified by the target user's
password database entry. Depending on the policy, this may
be the default behavior.
--hh, ----hheellpp Display a short help message to the standard output and exit.
--hh _h_o_s_t, ----hhoosstt=_h_o_s_t
Run the command on the specified _h_o_s_t if the security policy
plugin supports remote commands. Note that the _s_u_d_o_e_r_s
plugin does not currently support running remote commands.
This may also be used in conjunction with the --ll option to
list a user's privileges for the remote host.
--ii, ----llooggiinn
Run the shell specified by the target user's password
database entry as a login shell. This means that login-
specific resource files such as _._p_r_o_f_i_l_e or _._l_o_g_i_n will be
read by the shell. If a command is specified, it is passed
to the shell for execution via the shell's --cc option. If no
command is specified, an interactive shell is executed. ssuuddoo
attempts to change to that user's home directory before
running the shell. The command is run with an environment
similar to the one a user would receive at log in. The
_C_o_m_m_a_n_d _E_n_v_i_r_o_n_m_e_n_t section in the sudoers(4) manual
documents how the --ii option affects the environment in which
a command is run when the _s_u_d_o_e_r_s policy is in use.
--KK, ----rreemmoovvee--ttiimmeessttaammpp
Similar to the --kk option, except that it removes the user's
cached credentials entirely and may not be used in
conjunction with a command or other option. This option does
not require a password. Not all security policies support
credential caching.
--kk, ----rreesseett--ttiimmeessttaammpp
When used without a command, invalidates the user's cached
credentials. In other words, 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 _._l_o_g_o_u_t file.
When used in conjunction with a command or an option that may
require a password, this option will cause ssuuddoo to ignore the
user's cached credentials. As a result, ssuuddoo will prompt for
a password (if one is required by the security policy) and
will not update the user's cached credentials.
Not all security policies support credential caching.
--ll, ----lliisstt If no _c_o_m_m_a_n_d is specified, list the allowed (and forbidden)
commands for the invoking user (or the user specified by the
--UU option) on the current host. A longer list format is used
if this option is specified multiple times and the security
policy supports a verbose output format.
If a _c_o_m_m_a_n_d is specified and is permitted by the security
policy, the fully-qualified path to the command is displayed
along with any command line arguments. If _c_o_m_m_a_n_d is
specified but not allowed, ssuuddoo will exit with a status value
of 1.
--nn, ----nnoonn--iinntteerraaccttiivvee
Avoid prompting the user for input of any kind. If a
password is required for the command to run, ssuuddoo will
display an error message and exit.
--PP, ----pprreesseerrvvee--ggrroouuppss
Preserve the invoking user's group vector unaltered. By
default, the _s_u_d_o_e_r_s policy will initialize the group vector
to the list of groups the target user is a member of. The
real and effective group IDs, however, are still set to match
the target user.
--pp _p_r_o_m_p_t, ----pprroommpptt=_p_r_o_m_p_t
Use a custom password prompt with optional escape sequences.
The following percent (`%') escape sequences are supported by
the _s_u_d_o_e_r_s policy:
%H expanded to the host name including the domain name (on
if the machine's host name is fully qualified or the _f_q_d_n
option is set in sudoers(4))
%h expanded to the local host name without the domain name
%p expanded to the name of the user whose password is being
requested (respects the _r_o_o_t_p_w, _t_a_r_g_e_t_p_w, and _r_u_n_a_s_p_w
flags in sudoers(4))
%U expanded to the login name of the user the command will
be run as (defaults to root unless the --uu option is also
specified)
%u expanded to the invoking user's login name
%% two consecutive `%' characters are collapsed into a
single `%' character
The custom prompt will override the system password prompt on
systems that support PAM unless the _p_a_s_s_p_r_o_m_p_t___o_v_e_r_r_i_d_e flag
is disabled in _s_u_d_o_e_r_s.
--rr _r_o_l_e, ----rroollee=_r_o_l_e
Run the command with an SELinux security context that
includes the specified _r_o_l_e.
--SS, ----ssttddiinn
Write the prompt to the standard error and read the password
from the standard input instead of using the terminal device.
The password must be followed by a newline character.
--ss, ----sshheellll
Run the shell specified by the SHELL environment variable if
it is set or the shell specified by the invoking user's
password database entry. If a command is specified, it is
passed to the shell for execution via the shell's --cc option.
If no command is specified, an interactive shell is executed.
--tt _t_y_p_e, ----ttyyppee=_t_y_p_e
Run the command with an SELinux security context that
includes the specified _t_y_p_e. If no _t_y_p_e is specified, the
default type is derived from the role.
--UU _u_s_e_r, ----ootthheerr--uusseerr=_u_s_e_r
Used in conjunction with the --ll option to list the privileges
for _u_s_e_r instead of for the invoking user. The security
policy may restrict listing other users' privileges. The
_s_u_d_o_e_r_s policy only allows root or a user with the ALL
privilege on the current host to use this option.
--uu _u_s_e_r, ----uusseerr=_u_s_e_r
Run the command as a user other than the default target user
(usually _r_o_o_t _)_. The _u_s_e_r may be either a user name or a
numeric user ID (UID) prefixed with the `#' character (e.g.
#0 for UID 0). When running commands as a UID, many shells
require that the `#' be escaped with a backslash (`\'). Some
security policies may restrict UIDs to those listed in the
password database. The _s_u_d_o_e_r_s policy allows UIDs that are
not in the password database as long as the _t_a_r_g_e_t_p_w option
is not set. Other security policies may not support this.
--VV, ----vveerrssiioonn
Print the ssuuddoo version string as well as the version string
of the security policy plugin and any I/O plugins. If the
invoking user is already root the --VV option will display the
arguments passed to configure when ssuuddoo was built and plugins
may display more verbose information such as default options.
--vv, ----vvaalliiddaattee
Update the user's cached credentials, authenticating the user
if necessary. For the _s_u_d_o_e_r_s plugin, this extends the ssuuddoo
timeout for another 5 minutes by default, but does not run a
command. Not all security policies support cached
credentials.
---- The ---- option indicates that ssuuddoo should stop processing
command line arguments.
Environment variables to be set for the command may also be passed on the
command line in the form of VVAARR=_v_a_l_u_e, e.g.
LLDD__LLIIBBRRAARRYY__PPAATTHH=_/_u_s_r_/_l_o_c_a_l_/_p_k_g_/_l_i_b. Variables passed on the command line
are subject to restrictions imposed by the security policy plugin. The
_s_u_d_o_e_r_s policy subjects variables passed on the command line to the same
restrictions as normal environment variables with one important
exception. If the _s_e_t_e_n_v option is set in _s_u_d_o_e_r_s, the command to be run
has the SETENV tag set or the command matched is ALL, the user may set
variables that would otherwise be forbidden. See sudoers(4) for more
information.
CCOOMMMMAANNDD EEXXEECCUUTTIIOONN
When ssuuddoo executes a command, the security policy specifies the execution
environment for the command. Typically, the real and effective user and
group and IDs are set to match those of the target user, as specified in
the password database, and the group vector is initialized based on the
group database (unless the --PP option was specified).
The following parameters may be specified by security policy:
oo real and effective user ID
oo real and effective group ID
oo supplementary group IDs
oo the environment list
oo current working directory
oo file creation mode mask (umask)
oo SELinux role and type
oo Solaris project
oo Solaris privileges
oo BSD login class
oo scheduling priority (aka nice value)
PPrroocceessss mmooddeell
When ssuuddoo runs a command, it calls fork(2), sets up the execution
environment as described above, and calls the execve system call in the
child process. The main ssuuddoo process waits until the command has
completed, then passes the command's exit status to the security policy's
close function and exits. If an I/O logging plugin is configured or if
the security policy explicitly requests it, a new pseudo-terminal
(``pty'') is created and a second ssuuddoo process is used to relay job
control signals between the user's existing pty and the new pty the
command is being run in. This extra process makes it possible to, for
example, suspend and resume the command. Without it, the command would
be in what POSIX terms an ``orphaned process group'' and it would not
receive any job control signals. As a special case, if the policy plugin
does not define a close function and no pty is required, ssuuddoo will
execute the command directly instead of calling fork(2) first. The
_s_u_d_o_e_r_s policy plugin will only define a close function when I/O logging
is enabled, a pty is required, or the _p_a_m___s_e_s_s_i_o_n or _p_a_m___s_e_t_c_r_e_d options
are enabled. Note that _p_a_m___s_e_s_s_i_o_n and _p_a_m___s_e_t_c_r_e_d are enabled by
default on systems using PAM.
SSiiggnnaall hhaannddlliinngg
When the command is run as a child of the ssuuddoo process, ssuuddoo will relay
signals it receives to the command. Unless the command is being run in a
new pty, the SIGHUP, SIGINT and SIGQUIT signals are not relayed unless
they are sent by a user process, not the kernel. Otherwise, the command
would receive SIGINT twice every time the user entered control-C. Some
signals, such as SIGSTOP and SIGKILL, cannot be caught and thus will not
be relayed to the command. As a general rule, SIGTSTP should be used
instead of SIGSTOP when you wish to suspend a command being run by ssuuddoo.
As a special case, ssuuddoo will not relay signals that were sent by the
command it is running. This prevents the command from accidentally
killing itself. On some systems, the reboot(1m) command sends SIGTERM to
all non-system processes other than itself before rebooting the system.
This prevents ssuuddoo from relaying the SIGTERM signal it received back to
reboot(1m), which might then exit before the system was actually rebooted,
leaving it in a half-dead state similar to single user mode. Note,
however, that this check only applies to the command run by ssuuddoo and not
any other processes that the command may create. As a result, running a
script that calls reboot(1m) or shutdown(1m) via ssuuddoo may cause the system
to end up in this undefined state unless the reboot(1m) or shutdown(1m) are
run using the eexxeecc() family of functions instead of ssyysstteemm() (which
interposes a shell between the command and the calling process).
If no I/O logging plugins are loaded and the policy plugin has not
defined a cclloossee() function, set a command timeout or required that the
command be run in a new pty, ssuuddoo may execute the command directly
instead of running it as a child process.
PPlluuggiinnss
Plugins are dynamically loaded based on the contents of the sudo.conf(4)
file. If no sudo.conf(4) file is present, or it contains no Plugin
lines, ssuuddoo will use the traditional _s_u_d_o_e_r_s security policy and I/O
logging. See the sudo.conf(4) manual for details of the _/_e_t_c_/_s_u_d_o_._c_o_n_f
file and the sudo_plugin(1m) manual for more information about the ssuuddoo
plugin architecture.
EEXXIITT VVAALLUUEE
Upon successful execution of a program, the exit status from _s_u_d_o will
simply be the exit status of the program that was executed.
Otherwise, ssuuddoo exits with a value of 1 if there is a
configuration/permission problem or if ssuuddoo cannot execute the given
command. In the latter case the error string is printed to the standard
error. If ssuuddoo cannot 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 for stat(2) 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.
SSEECCUURRIITTYY NNOOTTEESS
ssuuddoo tries to be safe when executing external commands.
To prevent command spoofing, ssuuddoo checks "." and "" (both 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
environment variable is _n_o_t modified and is passed unchanged to the
program that ssuuddoo executes.
Please note that ssuuddoo will normally only log the command it explicitly
runs. If a user runs a command such as sudo su or sudo sh, subsequent
commands run from that shell are not subject to ssuuddoo's security policy.
The same is true for commands that offer shell escapes (including most
editors). If I/O logging is enabled, subsequent commands will have their
input and/or output logged, but there will not be traditional logs for
those commands. 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. For more
information, please see the _P_R_E_V_E_N_T_I_N_G _S_H_E_L_L _E_S_C_A_P_E_S section in
sudoers(4).
To prevent the disclosure of potentially sensitive information, ssuuddoo
disables core dumps by default while it is executing (they are re-enabled
for the command that is run). To aid in debugging ssuuddoo crashes, you may
wish to re-enable core dumps by setting ``disable_coredump'' to false in
the sudo.conf(4) file as follows:
Set disable_coredump false
See the sudo.conf(4) manual for more information.
EENNVVIIRROONNMMEENNTT
ssuuddoo utilizes the following environment variables. The security policy
has control over the actual content of the command's environment.
EDITOR Default editor to use in --ee (sudoedit) mode if neither
SUDO_EDITOR nor VISUAL is set.
MAIL In --ii mode or when _e_n_v___r_e_s_e_t is enabled in _s_u_d_o_e_r_s, set
to the mail spool of the target user.
HOME Set to the home directory of the target user if --ii or --HH
are specified, _e_n_v___r_e_s_e_t or _a_l_w_a_y_s___s_e_t___h_o_m_e are set in
_s_u_d_o_e_r_s, or when the --ss option is specified and _s_e_t___h_o_m_e
is set in _s_u_d_o_e_r_s.
PATH May be overridden by the security policy.
SHELL Used to determine shell to run with --ss option.
SUDO_ASKPASS Specifies the path to a helper program used to read the
password if no terminal is available or if the --AA option
is specified.
SUDO_COMMAND Set to the command run by sudo.
SUDO_EDITOR Default editor to use in --ee (sudoedit) mode.
SUDO_GID Set to the group ID of the user who invoked sudo.
SUDO_PROMPT Used as the default password prompt.
SUDO_PS1 If set, PS1 will be set to its value for the program
being run.
SUDO_UID Set to the user ID of the user who invoked sudo.
SUDO_USER Set to the login name of the user who invoked sudo.
USER Set to the target user (root unless the --uu option is
specified).
VISUAL Default editor to use in --ee (sudoedit) mode if
SUDO_EDITOR is not set.
FFIILLEESS
_/_e_t_c_/_s_u_d_o_._c_o_n_f ssuuddoo front end configuration
EEXXAAMMPPLLEESS
Note: the following examples assume a properly configured security
policy.
To get a file listing of an unreadable directory:
$ sudo ls /usr/local/protected
To list the home directory of user yaz on a machine where the file system
holding ~yaz is not exported as root:
$ sudo -u yaz ls ~yaz
To edit the _i_n_d_e_x_._h_t_m_l file as user www:
$ sudo -u www vi ~www/htdocs/index.html
To view system logs only accessible to root and users in the adm group:
$ sudo -g adm view /var/log/syslog
To run an editor as jim with a different primary group:
$ sudo -u jim -g audio vi ~jim/sound.txt
To shut down 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"
SSEEEE AALLSSOO
su(1), stat(2), login_cap(3), passwd(4), sudo.conf(4), sudoers(4),
sudo_plugin(1m), sudoreplay(1m), visudo(1m)
HHIISSTTOORRYY
See the HISTORY file in the ssuuddoo distribution
(http://www.sudo.ws/sudo/history.html) for a brief history of sudo.
AAUUTTHHOORRSS
Many people have worked on ssuuddoo over the years; this version consists of
code written primarily by:
Todd C. Miller
See the CONTRIBUTORS file in the ssuuddoo distribution
(http://www.sudo.ws/sudo/contributors.html) for an exhaustive list of
people who have contributed to 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 the sudoers(4) plugin's _n_o_e_x_e_c functionality.
It is not meaningful to run the cd command directly via sudo, e.g.,
$ sudo cd /usr/local/protected
since when the command exits the parent process (your shell) will still
be the same. Please see the _E_X_A_M_P_L_E_S section for more information.
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).
BBUUGGSS
If you feel you have found a bug in ssuuddoo, please submit a bug report at
http://www.sudo.ws/sudo/bugs/
SSUUPPPPOORRTT
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 merchantability
and fitness for a particular purpose are disclaimed. See the LICENSE
file distributed with ssuuddoo or http://www.sudo.ws/sudo/license.html for
complete details.
Sudo 1.8.8 August 14, 2013 Sudo 1.8.8
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