.\"
.\" Copyright (c) 1994-1996, 1998-2005, 2007-2012
.\" 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.
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.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\" ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\" 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.
.\"
.Dd July 10, 2012
.Dt SUDO @mansectsu@
.Os Sudo @PACKAGE_VERSION@
.Sh NAME
.Nm sudo ,
.Nm sudoedit
.Nd execute a command as another user
.Sh SYNOPSIS
.Nm sudo
.Fl h No | Fl K No | Fl k No | Fl L No | Fl V
.Nm sudo
.Fl v
.Op Fl AknS
.Bk -words
.Op Fl a Ar auth_type
.Ek
.Bk -words
.Op Fl g Ar group name No | Ar #gid
.Ek
.Bk -words
.Op Fl p Ar prompt
.Ek
.Bk -words
.Op Fl u Ar user name No | Ar #uid
.Ek
.Nm sudo
.Fl l Ns Op Ar l
.Op Fl AknS
.Bk -words
.Op Fl a Ar auth_type
.Ek
.Bk -words
.Op Fl g Ar group name No | Ar #gid
.Ek
.Bk -words
.Op Fl p Ar prompt
.Ek
.Bk -words
.Op Fl U Ar user name
.Ek
.Bk -words
.Op Fl u Ar user name No | Ar #uid
.Ek
.Op Ar command
.Nm sudo
.Op Fl AbEHnPS
.Bk -words
.Op Fl a Ar auth_type
.Ek
.Bk -words
.Op Fl C Ar fd
.Ek
.Bk -words
.Op Fl c Ar class No | Ar -
.Ek
.Bk -words
.Op Fl g Ar group name No | Ar #gid
.Ek
.Bk -words
.Op Fl p Ar prompt
.Ek
.Bk -words
.Op Fl r Ar role
.Ek
.Bk -words
.Op Fl t Ar type
.Ek
.Bk -words
.Op Fl u Ar user name No | Ar #uid
.Ek
.Bk -words
.Op Sy VAR Ns = Ns Ar value
.Ek
.Bk -words
.Fl i No | Fl s
.Ek
.Op Ar command
.Nm sudoedit
.Op Fl AnS
.Bk -words
.Op Fl a Ar auth_type
.Ek
.Bk -words
.Op Fl C Ar fd
.Ek
.Bk -words
.Op Fl c Ar class No | Ar -
.Ek
.Bk -words
.Op Fl g Ar group name No | Ar #gid
.Ek
.Bk -words
.Op Fl p Ar prompt
.Ek
.Bk -words
.Op Fl u Ar user name No | Ar #uid
.Ek
.Bk -words
file ...
.Ek
.Sh DESCRIPTION
.Nm sudo
allows a permitted user to execute a
.Ar command
as the superuser or another user, as specified by the
.Em sudoers
file.
See the
.Sx COMMAND EXECUTION
section below for more details.
.Pp
.Nm sudo
determines who is an authorized user by consulting the file
.Pa @sysconfdir@/sudoers .
By running
.Nm sudo
with the
.Fl v
option, a user can update the time stamp without running a
.Ar command .
If authentication is required,
.Nm sudo
will exit if the user's password is not entered within a configurable
time limit.
The default password prompt timeout is
.Li @password_timeout@
minutes.
.Pp
When invoked as
.Nm sudoedit ,
the
.Fl e
option (described below), is implied.
.Pp
The options are as follows:
.Bl -tag -width Fl
.It Fl A
Normally, if
.Nm sudo
requires a password, it will read it from the user's terminal.
If the
.Fl A No ( Em askpass Ns No )
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
.Ev SUDO_ASKPASS
environment variable is set, it specifies the path to the helper
program.
Otherwise, the value specified by the
.Em askpass
option in
.Xr sudoers @mansectform@
is used.
If no askpass program is available,
.Nm sudo
will exit with an error.
.It Fl a Ar type
The
.Fl a No ( Em "authentication type" Ns No )
option causes
.Nm sudo
to use the specified authentication type when validating the user,
as allowed by
.Pa /etc/login.conf .
The system administrator may specify a list of sudo-specific
authentication methods by adding an
.Dq auth-sudo
entry in
.Pa /etc/login.conf .
This option is only available on systems that support BSD authentication.
.It Fl b
The
.Fl b No ( Em background Ns No )
option tells
.Nm sudo
to run the given command in the background.
Note that if you use the
.Fl b
option you cannot use shell job control to manipulate the process.
Most interactive commands will fail to work properly in background
mode.
.It Fl C Ar fd
Normally,
.Nm sudo
will close all open file descriptors other than standard input,
standard output and standard error.
The
.Fl C No ( Em close from Ns No )
option allows the user to specify a starting point above the standard
error (file descriptor three).
Values less than three are not permitted.
This option is only available when the administrator has enabled the
.Em closefrom_override
option in
.Xr sudoers @mansectform@ .
.It Fl c Ar class
The
.Fl c No ( Em class Ns No )
option causes
.Nm sudo
to run the specified command with resources limited by the specified
login class.
The
.Em class
argument can be either a class name as defined in
.Pa /etc/login.conf ,
or a single
.Ql \-
character.
Specifying a
.Ar class
of
.Li -
indicates that the command should be run restricted by the default
login capabilities for the user the command is run as.
If the
.Ar class
argument specifies an existing user class, the command must be run
as root, or the
.Nm sudo
command must be run from a shell that is already root.
This option is only available on systems with BSD login classes.
.It Fl E
The
.Fl E No ( Em preserve environment Ns No )
option will override the
.Em env_reset
option in
.Xr sudoers @mansectform@ .
It is only available when either the matching command has the
.Li SETENV
tag or the
.Em setenv
option is set in
.Xr sudoers @mansectform@ .
.Nm sudo
will return an error if the
.Fl E
option is specified and the user does not have permission to preserve
the environment.
.It Fl e
The
.Fl e No ( Em edit Ns No )
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
.Em sudoers
file.
If the user is authorized by
.Em sudoers ,
the following steps are taken:
.Bl -enum -offset 4
.It
Temporary copies are made of the files to be edited with the owner
set to the invoking user.
.It
The editor specified by the
.Ev SUDO_EDITOR ,
.Ev VISUAL
or
.Ev EDITOR
environment variables (in that order) is run to edit the temporary files.
If none of
.Ev SUDO_EDITOR ,
.Ev VISUAL
or
.Ev EDITOR
are set, the first program listed in the
.Em editor
.Xr sudoers @mansectform@
option is used.
.It
If they have been modified, the temporary files are copied back to
their original location and the temporary versions are removed.
.El
.Pp
If the specified file does not exist, it will be created.
Note that unlike most commands run by
.Em sudo ,
the editor is run with the invoking user's environment unmodified.
If, for some reason,
.Nm sudo
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.
.It Fl g Ar group
Normally,
.Nm sudo
runs a command with the primary group set to the one specified by
the password database for the user the command is being run as (by
default, root).
The
.Fl g No ( Em group Ns No )
option causes
.Nm sudo
to run the command with the primary group set to
.Ar group
instead.
To specify a
.Em gid
instead of a
.Em "group name" ,
use
.Em #gid .
When running commands as a
.Em gid ,
many shells require that the
.Ql #
be escaped with a backslash
.Pq Ql \e .
If no
.Fl u
option is specified, the command will be run as the invoking user
(not root).
In either case, the primary group will be set to
.Em group .
.It Fl H
The
.Fl H No ( Em HOME Ns No )
option option sets the
.Ev HOME
environment variable to the home directory of the target user (root
by default) as specified by the password database.
The default handling of the
.Ev HOME
environment variable depends on
.Xr sudoers @mansectform@
settings.
By default,
.Nm sudo
will set
.Ev HOME
if
.Em env_reset
or
.Em always_set_home
are set, or if
.Em set_home
is set and the
.Fl s
option is specified on the command line.
.It Fl h
The
.Fl h No ( Em help Ns No )
option causes
.Nm sudo
to print a short help message to the standard output and exit.
.It Fl i Op Ar command
The
.Fl i No ( Em simulate initial login Ns No )
option runs the shell specified by the password database entry of
the target user as a login shell.
This means that login-specific resource files such as
.Pa .profile
or
.Pa .login
will be read by the shell.
If a command is specified, it is passed to the shell for execution
via the shell's
.Fl c
option.
If no command is specified, an interactive shell is executed.
.Nm sudo
attempts to change to that user's home directory before running the
shell.
It also initializes the environment to a minimal
set of variables, similar to what is present when a user logs in.
The
.Sx Command environment
section below documents in detail how the
.Fl i
option affects the environment in which a command is run.
.It Fl K
The
.Fl K No ( sure Em kill Ns No )
option is like
.Fl k
except that it removes the user's time stamp file entirely and
may not be used in conjunction with a command or other option.
This option does not require a password.
.It Fl k Op Ar command
When used alone, the
.Fl k No ( Em kill Ns No )
option to
.Nm sudo
invalidates the user's time stamp file.
The next time
.Nm sudo
is run a password will be required.
This option does not require a password and was added to allow a
user to revoke
.Nm sudo
permissions from a
.Pa .logout
file.
.Pp
When used in conjunction with a command or an option that may require
a password, the
.Fl k
option will cause
.Nm sudo
to ignore the user's time stamp file.
As a result,
.Nm sudo
will prompt for a password (if one is required by
.Em sudoers )
and will not update the user's time stamp file.
.It Fl L
The
.Fl L No ( Em list No defaults Ns )
option will list the parameters that
may be set in a
.Em Defaults
line along with a short description for each.
This option will be removed from a future version of
.Nm sudo .
.It Fl l Ns Oo Sy l Oc Op Ar command
If no
.Ar command
is specified, the
.Fl l No ( Em list Ns No )
option will list the allowed (and forbidden) commands for the
invoking user (or the user specified by the
.Fl U
option) on the current host.
If a
.Ar command
is specified and is permitted by
.Em sudoers ,
the fully-qualified
path to the command is displayed along with any command line
arguments.
If
.Ar command
is specified but not allowed,
.Nm sudo
will exit with a status value of 1.
If the
.Fl l
option is specified with an
.Ar l
argument
.Pq i.e.\& Fl ll ,
or if
.Fl l
is specified multiple times, a longer list format is used.
.It Fl n
The
.Fl n No ( Em non-interactive Ns No )
option prevents
.Nm sudo
from prompting the user for a password.
If a password is required for the command to run,
.Nm sudo
will display an error message and exit.
.It Fl P
The
.Fl P No ( Em preserve group vector Ns No )
option causes
.Nm sudo
to preserve the invoking user's group vector unaltered.
By default,
.Nm sudo
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.
.It Fl p Ar prompt
The
.Fl p No ( Em prompt Ns No )
option allows you to override the default password prompt and use
a custom one.
The following percent
.Pq Ql %
escapes are supported:
.Bl -tag -width 2n
.It Li %H
expanded to the host name including the domain name (on if the
machine's host name is fully qualified or the
.Em fqdn
option is set in
.Xr sudoers @mansectform@ )
.It Li %h
expanded to the local host name without the domain name
.It Li %p
expanded to the name of the user whose password is being requested
(respects the
.Em rootpw ,
.Em targetpw ,
and
.Em runaspw
flags in
.Xr sudoers @mansectform@ )
.It Li \&%U
expanded to the login name of the user the command will be run as
(defaults to root unless the
.Fl u
option is also specified)
.It Li %u
expanded to the invoking user's login name
.It Li %%
two consecutive
.Ql %
characters are collapsed into a single
.Ql %
character
.El
.Pp
The prompt specified by the
.Fl p
option will override the system password prompt on systems that
support PAM unless the
.Em passprompt_override
flag is disabled in
.Em sudoers .
.It Fl r Ar role
The
.Fl r No ( Em role Ns No )
option causes the new (SELinux) security context to have the role
specified by
.Ar role .
.It Fl S
The
.Fl S ( Em stdin Ns No )
option causes
.Nm sudo
to read the password from the standard input instead of the terminal
device.
The password must be followed by a newline character.
.It Fl s Op Ar command
The
.Fl s ( Em shell Ns No )
option runs the shell specified by the
.Ev SHELL
environment variable if it is set or the shell as specified in the
password database.
If a command is specified, it is passed to the shell for execution
via the shell's
.Fl c
option.
If no command is specified, an interactive shell is executed.
.It Fl t Ar type
The
.Fl t ( Em type Ns No )
option causes the new (SELinux) security context to have the type
specified by
.Ar type .
If no type is specified, the default type is derived from the
specified role.
.It Fl U Ar user
The
.Fl U ( Em other user Ns No )
option is used in conjunction with the
.Fl l
option to specify the user whose privileges should be listed.
Only root or a user with the
.Li ALL
privilege on the current host may use this option.
.It Fl u Ar user
The
.Fl u ( Em user Ns No )
option causes
.Nm sudo
to run the specified command as a user other than
.Em root .
To specify a
.Em uid
instead of a
.Em user name ,
.Em #uid .
When running commands as a
.Em uid ,
many shells require that the
.Ql #
be escaped with a backslash
.Pq Ql \e .
Note that if the
.Em targetpw
Defaults option is set (see
.Xr sudoers @mansectform@ ) ,
it is not possible to run commands with a uid not listed in the
password database.
.It Fl V
The
.Fl V ( Em version Ns No )
option causes
.Nm sudo
to print its version string and exit.
If the invoking user is already root the
.Fl V
option will display the arguments passed to configure when
.Nm sudo
was built as well a list of the defaults
.Nm sudo
was compiled with as well as the machine's local network addresses.
.It Fl v
When given the
.Fl v ( Em validate Ns No )
option,
.Nm sudo
will update the user's time stamp file, authenticating the user's
password if necessary.
This extends the
.Nm sudo
timeout for another
.Li @timeout@
minutes (or whatever the timeout is set to in
.Em sudoers )
but does not run a command.
.It Fl -
The
.Fl -
option indicates that
.Nm sudo
should stop processing command line arguments.
.El
.Pp
Environment variables to be set for the command may also be passed
on the command line in the form of
.Sy VAR Ns No = Ns Em value ,
e.g.\&
.Sy LD_LIBRARY_PATH Ns No = Ns Em /usr/local/pkg/lib .
Variables passed on the command line are subject to the same
restrictions as normal environment variables with one important
exception.
If the
.Em setenv
option is set in
.Em sudoers ,
the command to be run has the
.Li SETENV
tag set or the command matched is
.Li ALL ,
the user may set variables that would otherwise be forbidden.
See
.Xr sudoers @mansectform@
for more information.
.Ss Authentication and logging
.Nm sudo
requires that most users authenticate themselves by default.
A password is not required
if the invoking user is root, if the target user is the same as the
invoking user, or if the authentication has been disabled for the
user or command in the
.Em sudoers
file.
Unlike
.Xr su 1 ,
when
.Nm sudo
requires
authentication, it validates the invoking user's credentials, not
the target user's (or root's) credentials.
This can be changed via
the
.Em rootpw ,
.Em targetpw
and
.Em runaspw
Defaults entries in
.Em sudoers .
.Pp
If a user who is not listed in
.Em sudoers
tries to run a command via
.Nm sudo ,
mail is sent to the proper authorities.
The address
used for such mail is configurable via the
.Em mailto
.Em sudoers
Defaults entry and defaults to
.Li @mailto@ .
.Pp
Note that mail will not be sent if an unauthorized user tries to
run
.Nm sudo
with the
.Fl l
or
.Fl v
option.
This allows users to
determine for themselves whether or not they are allowed to use
.Nm sudo .
.Pp
If
.Nm sudo
is run by root and the
.Ev SUDO_USER
environment variable
is set, its value will be used to determine who the actual user is.
This can be used by a user to log commands
through
.Nm sudo
even when a root shell has been invoked.
It also
allows the
.Fl e
option to remain useful even when invoked via a
sudo-run script or program.
Note, however, that the
.Em sudoers
lookup is still done for root, not the user specified by
.Ev SUDO_USER .
.Pp
.Nm sudo
uses time stamp files for credential caching.
Once a
user has been authenticated, the time stamp is updated and the user
may then use sudo without a password for a short period of time
.Po
.Li @timeout@
minutes unless overridden by the
.Em timeout
option
.Pc .
By default,
.Nm sudo
uses a tty-based time stamp which means that
there is a separate time stamp for each of a user's login sessions.
The
.Em tty_tickets
option can be disabled to force the use of a
single time stamp for all of a user's sessions.
.Pp
.Nm sudo
can log both successful and unsuccessful attempts (as well
as errors) to
.Xr syslog 3 ,
a log file, or both.
By default,
.Nm sudo
will log via
.Xr syslog 3
but this is changeable via the
.Em syslog
and
.Em logfile
Defaults settings.
.Pp
.Nm sudo
also supports logging a command's input and output
streams.
I/O logging is not on by default but can be enabled using
the
.Em log_input
and
.Em log_output
Defaults flags as well as the
.Li LOG_INPUT
and
.Li LOG_OUTPUT
command tags.
.Ss Command environment
Since environment variables can influence program behavior,
.Nm sudo
provides a means to restrict which variables from the user's
environment are inherited by the command to be run.
There are two
distinct ways
.Em sudoers
can be configured to handle with environment variables.
.Pp
By default, the
.Em env_reset
option is enabled.
This causes commands
to be executed with a new, minimal environment.
On AIX (and Linux
systems without PAM), the environment is initialized with the
contents of the
.Pa /etc/environment
file.
On BSD systems, if the
.Em use_loginclass
option is enabled, the environment is initialized
based on the
.Em path
and
.Em setenv
settings in
.Pa /etc/login.conf .
The new environment contains the
.Ev TERM ,
.Ev PATH ,
.Ev HOME ,
.Ev MAIL ,
.Ev SHELL ,
.Ev LOGNAME ,
.Ev USER ,
.Ev USERNAME
and
.Ev SUDO_*
variables
in addition to variables from the invoking process permitted by the
.Em env_check
and
.Em env_keep
options.
This is effectively a whitelist
for environment variables.
.Pp
If, however, the
.Em env_reset
option is disabled, any variables not
explicitly denied by the
.Em env_check
and
.Em env_delete
options are
inherited from the invoking process.
In this case,
.Em env_check
and
.Em env_delete
behave like a blacklist.
Since it is not possible
to blacklist all potentially dangerous environment variables, use
of the default
.Em env_reset
behavior is encouraged.
.Pp
In all cases, environment variables with a value beginning with
.Li ()
are removed as they could be interpreted as
.Sy bash
functions.
The list of environment variables that
.Nm sudo
allows or denies is
contained in the output of
.Dq Li sudo -V
when run as root.
.Pp
Note that the dynamic linker on most operating systems will remove
variables that can control dynamic linking from the environment of
setuid executables, including
.Nm sudo .
Depending on the operating
system this may include
.Ev _RLD* ,
.Ev DYLD_* ,
.Ev LD_* ,
.Ev LDR_* ,
.Ev LIBPATH ,
.Ev SHLIB_PATH ,
and others.
These type of variables are
removed from the environment before
.Nm sudo
even begins execution
and, as such, it is not possible for
.Nm sudo
to preserve them.
.Pp
As a special case, if
.Nm sudo Ns No 's
.Fl i
option (initial login) is
specified,
.Nm sudo
will initialize the environment regardless
of the value of
.Em env_reset .
The
.Ev DISPLAY ,
.Ev PATH
and
.Ev TERM
variables remain unchanged;
.Ev HOME ,
.Ev MAIL ,
.Ev SHELL ,
.Ev USER ,
and
.Ev LOGNAME
are set based on the target user.
On AIX (and Linux
systems without PAM), the contents of
.Pa /etc/environment
are also
included.
On BSD systems, if the
.Em use_loginclass
option is
enabled, the
.Em path
and
.Em setenv
variables in
.Pa /etc/login.conf
are also applied.
All other environment variables are removed.
.Pp
Finally, if the
.Em env_file
option is defined, any variables present
in that file will be set to their specified values as long as they
would not conflict with an existing environment variable.
.Sh COMMAND EXECUTION
When
.Nm sudo
executes a command, the
.Em sudoers
file specifies the execution envionment for the command.
Typically, the real and effective uid and gid 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
.Fl P
option was specified).
.Pp
The
.Em sudoers
file settings affect the following execution parameters:
.Bl -bullet
.It
real and effective user ID
.It
real and effective group ID
.It
supplementary group IDs
.It
the environment list
.It
SELinux role and type
.It
Solaris project
.It
Solaris privileges
.It
BSD login class
.It
file creation mode mask (umask)
.El
.Pp
See the
.Sx Command environment
section for details on how the environment list is constructed.
.Ss Process model
If
.Nm sudo
has been configured with PAM support or if I/O logging is enabled,
.Nm sudo
must wait until the command has completed before it will exit.
In the case of PAM,
.Nm sudo
must remain running so that it can close the PAM session
when the command is finished.
If neither PAM nor I/O logging are configured,
.Nm sudo
will execute the command without calling
.Xr fork 2 .
In either case,
.Nm sudo
sets up the execution environment as described above, and calls the
.Xr execve
system call (potentially in a child process).
If I/O logging is enabled, a new pseudo-terminal
.Pq Dq pty
is created and a second
.Nm sudo
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
.Dq orphaned process group
and it would not receive any job control signals.
.Ss Signal handling
If the command is run as a child of the
.Nm sudo
process (due to PAM or I/O logging),
.Nm sudo
will relay signals it receives to the command.
Unless the command is being run in a new pty, the
.Dv SIGHUP ,
.Dv SIGINT
and
.Dv SIGQUIT
signals are not relayed unless they are sent by a user process,
not the kernel.
Otherwise, the command would receive
.Dv SIGINT
twice every time the user entered control-C.
Some signals, such as
.Dv SIGSTOP
and
.Dv SIGKILL ,
cannot be caught and thus will not be relayed to the command.
As a general rule,
.Dv SIGTSTP
should be used instead of
.Dv SIGSTOP
when you wish to suspend a command being run by
.Nm sudo .
.Pp
As a special case,
.Nm sudo
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
.Xr reboot @mansectsu@
command sends
.Dv SIGTERM
to all non-system processes other than itself before rebooting
the systyem.
This prevents
.Nm sudo
from relaying the
.Dv SIGTERM
signal it received back to
.Xr reboot @mansectsu@ ,
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
.Nm sudo
and not any other processes that the command may create.
As a result, running a script that calls
.Xr reboot @mansectsu@
or
.Xr shutdown @mansectsu@
via
.Nm sudo
may cause the system to end up in this undefined state unless the
.Xr reboot @mansectsu@
or
.Xr shutdown @mansectsu@
are run using the
.Fn exec
family of functions instead of
.Fn system
(which interposes a shell between the command and the calling process).
.Sh EXIT VALUE
Upon successful execution of a program, the exit status from
.Em sudo
will simply be the exit status of the program that was executed.
.Pp
Otherwise,
.Nm sudo
exits with a value of 1 if there is a configuration/permission
problem or if
.Nm sudo
cannot execute the given command.
In the latter case the error string is printed to the standard error.
If
.Nm sudo
cannot
.Xr stat 2
one or more entries in the user's
.Ev 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
.Xr stat 2
to return
.Dq permission denied
is if you are running an automounter and one of the directories in
your
.Ev PATH
is on a machine that is currently unreachable.
.Sh LOG FORMAT
.Nm sudo
can log events using either
.Xr syslog 3
or a simple log file.
In each case the log format is almost identical.
.Ss Accepted command log entries
Commands that sudo runs are logged using the following format (split
into multiple lines for readability):
.Bd -literal -offset 4n
date hostname progname: username : TTY=ttyname ; PWD=cwd ; \e
USER=runasuser ; GROUP=runasgroup ; TSID=logid ; \e
ENV=env_vars COMMAND=command
.Ed
.Pp
Where the fields are as follows:
.Bl -tag -width 12n
.It date
The date the command was run.
Typically, this is in the format
.Dq MMM, DD, HH:MM:SS .
If logging via
.Xr syslog 3 ,
the actual date format is controlled by the syslog daemon.
If logging to a file and the
.Em log_year
option is enabled,
the date will also include the year.
.It hostname
The name of the host
.Nm sudo
was run on.
This field is only present when logging via
.Xr syslog 3 .
.It progname
The name of the program, usually
.Em sudo
or
.Em sudoedit .
This field is only present when logging via
.Xr syslog 3 .
.It username
The login name of the user who ran
.Nm sudo .
.It ttyname
The short name of the terminal (e.g.\&
.Dq console ,
.Dq tty01 ,
or
.Dq pts/0 )
.Nm sudo
was run on, or
.Dq unknown
if there was no terminal present.
.It cwd
The current working directory that
.Nm sudo
was run in.
.It runasuser
The user the command was run as.
.It runasgroup
The group the command was run as if one was specified on the command line.
.It logid
An I/O log identifier that can be used to replay the command's output.
This is only present when the
.Em log_input
or
.Em log_output
option is enabled.
.It env_vars
A list of environment variables specified on the command line,
if specified.
.It command
The actual command that was executed.
.El
.Pp
Messages are logged using the locale specified by
.Em sudoers_locale ,
which defaults to the
.Dq Li C
locale.
.Ss Denied command log entries
If the user is not allowed to run the command, the reason for the denial
will follow the user name.
Possible reasons include:
.Bl -tag -width 4
.It user NOT in sudoers
The user is not listed in the
.Em sudoers
file.
.It user NOT authorized on host
The user is listed in the
.Em sudoers
file but is not allowed to run commands on the host.
.It command not allowed
The user is listed in the
.Em sudoers
file for the host but they are not allowed to run the specified command.
.It 3 incorrect password attempts
The user failed to enter their password after 3 tries.
The actual number of tries will vary based on the number of
failed attempts and the value of the
.Em passwd_tries
.Em sudoers
option.
.It a password is required
The
.Fl n
option was specified but a password was required.
.It sorry, you are not allowed to set the following environment variables
The user specified environment variables on the command line that
were not allowed by
.Em sudoers .
.El
.Ss Error log entries
If an error occurs,
.Nm sudo
will log a message and, in most cases, send a message to the
administrator via email.
Possible errors include:
.Bl -tag -width 4
.It parse error in @sysconfdir@/sudoers near line N
.Nm sudo
encountered an error when parsing the specified file.
In some cases, the actual error may be one line above or below the
line number listed, depending on the type of error.
.It problem with defaults entries
The
.Em sudoers
file contains one or more unknown Defaults settings.
This does not prevent
.Nm sudo
from running, but the
.Em sudoers
file should be checked using
.Nm visudo .
.It timestamp owner (username): \&No such user
The time stamp directory owner, as specified by the
.Em timestampowner
setting, could not be found in the password database.
.It unable to open/read @sysconfdir@/sudoers
The
.Em sudoers
file could not be opened for reading.
This can happen when the
.Em sudoers
file is located on a remote file system that maps user ID 0 to
a different value.
Normally,
.Nm sudo
tries to open
.Em sudoers
using group permissions to avoid this problem.
.It unable to stat @sysconfdir@/sudoers
The
.Pa @sysconfdir@/sudoers
file is missing.
.It @sysconfdir@/sudoers is not a regular file
The
.Pa @sysconfdir@/sudoers
file exists but is not a regular file or symbolic link.
.It @sysconfdir@/sudoers is owned by uid N, should be 0
The
.Em sudoers
file has the wrong owner.
.It @sysconfdir@/sudoers is world writable
The permissions on the
.Em sudoers
file allow all users to write to it.
The
.Em sudoers
file must not be world-writable, the default file mode
is 0440 (readable by owner and group, writable by none).
.It @sysconfdir@/sudoers is owned by gid N, should be 1
The
.Em sudoers
file has the wrong group ownership.
.It unable to open @timedir@/username/ttyname
.Em sudoers
was unable to read or create the user's time stamp file.
.It unable to write to @timedir@/username/ttyname
.Em sudoers
was unable to write to the user's time stamp file.
.It unable to mkdir to @timedir@/username
.Em sudoers
was unable to create the user's time stamp directory.
.El
.Ss Notes on logging via syslog
By default,
.Em sudoers
logs messages via
.Xr syslog 3 .
The
.Em date ,
.Em hostname ,
and
.Em progname
fields are added by the syslog daemon, not
.Em sudoers
itself.
As such, they may vary in format on different systems.
.Pp
On most systems,
.Xr syslog 3
has a relatively small log buffer.
To prevent the command line arguments from being truncated,
.Nm sudo
will split up log messages that are larger than 960 characters
(not including the date, hostname, and the string
.Dq sudo ) .
When a message is split, additional parts will include the string
.Dq Pq command continued
after the user name and before the continued command line arguments.
.Ss Notes on logging to a file
If the
.Em logfile
option is set,
.Em sudoers
will log to a local file, such as
.Pa /var/log/sudo .
When logging to a file,
.Em sudoers
uses a format similar to
.Xr syslog 3 ,
with a few important differences:
.Bl -enum
.It
The
.Em progname
and
.Em hostname
fields are not present.
.It
If the
.Em log_year
.Em sudoers
option is enabled,
the date will also include the year.
.It
Lines that are longer than
.Em loglinelen
characters (80 by default) are word-wrapped and continued on the
next line with a four character indent.
This makes entries easier to read for a human being, but makes it
more difficult to use
.Xr grep 1
on the log files.
If the
.Em loglinelen
.Em sudoers
option is set to 0 (or negated with a
.Ql \&! ) ,
word wrap will be disabled.
.El
.Sh SECURITY NOTES
.Nm sudo
tries to be safe when executing external commands.
.Pp
To prevent command spoofing,
.Nm sudo
checks "." and "" (both denoting current directory) last when
searching for a command in the user's
.Ev PATH
(if one or both are in the
.Ev PATH ) .
Note, however, that the actual
.Ev PATH
environment variable is
.Em not
modified and is passed unchanged to the program that
.Nm sudo
executes.
.Pp
.Nm sudo
will check the ownership of its time stamp directory
.Po
.Pa @timedir@
by default
.Pc
and ignore the directory's contents if it is not owned by root or
if it is writable by a user other than root.
On systems that allow non-root users to give away files via
.Xr chown 2 ,
if the time stamp directory is located in a world-writable
directory (e.g.\&,
.Pa /tmp ) ,
it is possible for a user to create the time stamp directory before
.Nm sudo
is run.
However, because
.Nm sudo
checks the ownership and mode of the directory and its
contents, the only damage that can be done is to
.Dq hide
files by putting them in the time stamp dir.
This is unlikely to happen since once the time stamp dir is owned by root
and inaccessible by any other user, the user placing files there would be
unable to get them back out.
.Pp
.Nm sudo
will not honor time stamps set far in the future.
Time stamps with a date greater than current_time + 2 *
.Li TIMEOUT
will be ignored and sudo will log and complain.
This is done to keep a user from creating his/her own time stamp with a
bogus date on systems that allow users to give away files if the time
stamp directory is located in a world-writable directory.
.Pp
On systems where the boot time is available,
.Nm sudo
will ignore time stamps that date from before the machine booted.
.Pp
Since time stamp files live in the file system, they can outlive a
user's login session.
As a result, a user may be able to login, run a command with
.Nm sudo
after authenticating, logout, login again, and run
.Nm sudo
without authenticating so long as the time stamp file's modification
time is within
.Li @timeout@
minutes (or whatever the timeout is set to in
.Em sudoers ) .
When the
.Em tty_tickets
.Em sudoers
option is enabled, the time stamp has per-tty granularity but still
may outlive the user's session.
On Linux systems where the devpts filesystem is used, Solaris systems
with the devices filesystem, as well as other systems that utilize a
devfs filesystem that monotonically increase the inode number of devices
as they are created (such as Mac OS X),
.Nm sudo
is able to determine when a tty-based time stamp file is stale and will
ignore it.
Administrators should not rely on this feature as it is not universally
available.
.Pp
Please note that
.Nm sudo
will normally only log the command it explicitly runs.
If a user runs a command such as
.Li sudo su
or
.Li sudo sh ,
subsequent commands run from that shell are not subject to
.Nm sudo Ns No '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
.Nm sudo
to verify that the command does not inadvertently give the user an
effective root shell.
For more information, please see the
.Em PREVENTING SHELL ESCAPES
section in
.Xr sudoers @mansectform@ .
.Pp
To prevent the disclosure of potentially sensitive information,
.Nm sudo
disables core dumps by default while it is executing (they are
re-enabled for the command that is run).
.Pp
For information on the security implications of
.Em sudoers
entries, please see the
.Em SECURITY NOTES
section in
.Xr sudoers @mansectform@ .
.Sh ENVIRONMENT
.Nm sudo
utilizes the following environment variables:
.Bl -tag -width 15n
.It Ev EDITOR
Default editor to use in
.Fl e
(sudoedit) mode if neither
.Ev SUDO_EDITOR
nor
.Ev VISUAL
is set.
.It Ev MAIL
In
.Fl i
mode or when
.Em env_reset
is enabled in
.Em sudoers ,
set to the mail spool of the target user.
.It Ev HOME
Set to the home directory of the target user if
.Fl i
or
.Fl H
are specified,
.Em env_reset
or
.Em always_set_home
are set in
.Em sudoers ,
or when the
.Fl s
option is specified and
.Em set_home
is set in
.Em sudoers .
.It Ev PATH
Set to a sane value if the
.Em secure_path
option is set in the
.Em sudoers
file.
.It Ev SHELL
Used to determine shell to run with
.Fl s
option.
.It Ev SUDO_ASKPASS
Specifies the path to a helper program used to read the password
if no terminal is available or if the
.Fl A
option is specified.
.It Ev SUDO_COMMAND
Set to the command run by sudo.
.It Ev SUDO_EDITOR
Default editor to use in
.Fl e
(sudoedit) mode.
.It Ev SUDO_GID
Set to the group ID of the user who invoked sudo.
.It Ev SUDO_PROMPT
Used as the default password prompt.
.It Ev SUDO_PS1
If set,
.Ev PS1
will be set to its value for the program being run.
.It Ev SUDO_UID
Set to the user ID of the user who invoked sudo.
.It Ev SUDO_USER
Set to the login name of the user who invoked sudo.
.It Ev USER
Set to the target user (root unless the
.Fl u
option is specified).
.It Ev VISUAL
Default editor to use in
.Fl e
(sudoedit) mode if
.Ev SUDO_EDITOR
is not set.
.El
.Sh FILES
.Bl -tag -width 24n
.It Pa @sysconfdir@/sudoers
List of who can run what
.It Pa @timedir@
Directory containing time stamps
.It Pa /etc/environment
Initial environment for
.Fl i
mode on AIX and Linux systems
.El
.Sh EXAMPLES
Note: the following examples assume suitable
.Xr sudoers 5
entries.
.Pp
To get a file listing of an unreadable directory:
.Bd -literal -offset indent
$ sudo ls /usr/local/protected
.Ed
.Pp
To list the home directory of user yaz on a machine where the file
system holding ~yaz is not exported as root:
.Bd -literal -offset indent
$ sudo -u yaz ls ~yaz
.Ed
.Pp
To edit the
.Pa index.html
file as user www:
.Bd -literal -offset indent
$ sudo -u www vi ~www/htdocs/index.html
.Ed
.Pp
To view system logs only accessible to root and users in the adm
group:
.Bd -literal -offset indent
$ sudo -g adm view /var/log/syslog
.Ed
.Pp
To run an editor as jim with a different primary group:
.Bd -literal -offset indent
$ sudo -u jim -g audio vi ~jim/sound.txt
.Ed
.Pp
To shut down a machine:
.Bd -literal -offset indent
$ sudo shutdown -r +15 "quick reboot"
.Ed
.Pp
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
.Li cd
and file redirection work.
.Bd -literal -offset indent
$ sudo sh -c "cd /home ; du -s * | sort -rn > USAGE"
.Ed
.Sh SEE ALSO
.Xr grep 1 ,
.Xr su 1 ,
.Xr stat 2 ,
.Xr login_cap 3 ,
.Xr passwd @mansectform@ ,
.Xr sudoers @mansectform@ ,
.Xr sudoreplay @mansectsu@ ,
.Xr visudo @mansectsu@
.Sh HISTORY
See the HISTORY file in the
.Nm sudo
distribution (http://www.sudo.ws/sudo/history.html) for a brief
history of sudo.
.Sh AUTHORS
Many people have worked on
.Nm sudo
over the years; this version consists of code written primarily by:
.Bd -ragged -offset indent
Todd C. Miller
.Ed
.Pp
See the CONTRIBUTORS file in the
.Nm sudo
distribution (http://www.sudo.ws/sudo/contributors.html) for an
exhaustive list of people who have contributed to
.Nm sudo .
.Sh 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
.Nm sudo .
Also, many programs (such as editors) allow the user to run commands
via shell escapes, thus avoiding
.Nm sudo Ns No 's
checks.
However, on most systems it is possible to prevent shell escapes with
.Nm sudo ' s
.Em noexec
functionality.
See the
.Xr sudoers @mansectform@
manual for details.
.Pp
It is not meaningful to run the
.Li cd
command directly via sudo, e.g.,
.Bd -literal -offset indent
$ sudo cd /usr/local/protected
.Ed
.Pp
since when the command exits the parent process (your shell) will
still be the same.
Please see the
.Sx EXAMPLES
section for more information.
.Pp
Running shell scripts via
.Nm sudo
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).
.Sh BUGS
If you feel you have found a bug in
.Nm sudo ,
please submit a bug report at http://www.sudo.ws/sudo/bugs/
.Sh SUPPORT
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.
.Sh DISCLAIMER
.Nm sudo
is provided
.Dq 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
.Nm sudo
or http://www.sudo.ws/sudo/license.html for complete details.