sudoedit - Unix, Linux Command

sudo [-bEHPS]
[-p prompt]
[-u username|#uid]
[VAR=value] {-i | -s | command}


sudoedit [-S]
[-p prompt] [-u username|#uid]
file ...


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


sudo determines who is an authorized user by consulting the file
/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 5 minutes (unless overridden via
sudoers).


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
root).  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 SUDO_USER 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 SUDO_USER.


sudo 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.



If the specified file does not exist, it will be created.  Note
that unlike most commands run by sudo, the editor is run with
the invoking user’s environment unmodified.  If, for some reason,
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.


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
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.


There are two distinct ways to deal with environment variables.
By default, the env_reset sudoers option is enabled.
This causes commands to be executed with a minimal environment
containing TERM, PATH, HOME, SHELL, LOGNAME, USER
and USERNAME in addition to variables from the invoking process
permitted by the env_check and env_keep sudoers options.
There is effectively a whitelist for environment variables.


If, however, the env_reset option is disabled in sudoers, any
variables not explicitly denied by the env_check and env_delete
options are inherited from the invoking process.  In this case,
env_check and env_delete behave like a blacklist.  Since it
is not possible to blacklist all potentially dangerous environment
variables, use of the default env_reset behavior is encouraged.


In all cases, environment variables with a value beginning with
() are removed as they could be interpreted as bash functions.
The list of environment variables that sudo allows or denies is
contained in the output of sudo -V when run as root.


Note that the dynamic linker on most operating systems will remove
variables that can control dynamic linking from the environment of
setuid executables, including sudo.  Depending on the operating
system this may include _RLD*, DYLD_*, LD_*, LDR_*,
LIBPATH, SHLIB_PATH, and others.  These type of variables are
removed from the environment before sudo even begins execution
and, as such, it is not possible for sudo to preserve them.


To prevent command spoofing, sudo 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 not modified and is passed
unchanged to the program that sudo executes.


sudo 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 or if it is writable by a user other than
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 sudo 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 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/run/sudo with the appropriate owner (root)
and permissions (0700) in the system startup files.


sudo will not honor timestamps set far in the future.
Timestamps with a date greater than current_time + 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 sudo 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 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.  For more
information, please see the PREVENTING SHELL ESCAPES section in
sudoers(5).


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"




        Todd C. Miller
        Chris Jepeway


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


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 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 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).


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