On 04/01/09 16:53, Garrett D'Amore wrote:
> Can we please have the aforementioned manual page, either in mail or in
> the case materials?
Sure, sudo(1m) and sudoers(4) below.
Joep
--- sudo(1m) ----
MAINTENANCE COMMANDS SUDO(1m)
NAME
sudo, sudoedit - execute a command as another user
SYNOPSIS
sudo [-n] -h | -K | -k | -L | -V | -v
sudo -l[l] [-AnS] [-g groupname|#gid] [-U username]
[-u username|#uid] [command]
sudo [-AbEHnPS] [-C fd] [-g groupname|#gid] [-p prompt]
[-u username|#uid] [VAR=value] [-i | -s] [command]
sudoedit [-AnS] [-C fd] [-g groupname|#gid] [-p prompt]
[-u username|#uid] file ...
DESCRIPTION
sudo allows a permitted user to execute a command as the
superuser or another 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 group file (unless
the -P option was specified). If the invoking user is root
or if the target user is the same as the invoking user, no
password is required. Otherwise, sudo requires that users
authenticate themselves with a password by default (NOTE: in
the default configuration this is the user's password, not
the root password). Once a user has been authenticated, a
timestamp is updated and the user may then use sudo without
a password for a short period of time (5 minutes unless
overridden in sudoers).
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 running sudo with the -v option, 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
option. 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
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MAINTENANCE COMMANDS SUDO(1m)
commands through sudo even when a root shell has been
invoked. It also allows the -e option 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.
OPTIONS
sudo accepts the following command line options:
-A Normally, if sudo requires a password, it will
read it from the current terminal. If the -A
(askpass) option is specified, a 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, the value specified by the askpass
option in sudoers(4) is used.
-b The -b (background) option tells sudo 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 process.
-C fd Normally, sudo will close all open file
descriptors other than standard input, standard
output and standard error. The -C (close from)
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 if the
administrator has enabled the closefrom_override
option in sudoers(4).
-E The -E (preserve environment) option will
override the env_reset option in sudoers(4)).
It is only available when either the matching
command has the SETENV tag or the setenv option
is set in sudoers(4).
-e The -e (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:
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MAINTENANCE COMMANDS SUDO(1m)
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 SUDO_EDITOR,
VISUAL or EDITOR environment variables is
run to edit the temporary files. If none of
SUDO_EDITOR, VISUAL or EDITOR are set, the
first program listed in the editor sudoers
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
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.
-g group Normally, sudo sets the primary group to the one
specified by the passwd database for the user
the command is being run as (by default, root).
The -g (group) option causes sudo to run the
specified command with the primary group set to
group. To specify a gid instead of a group
name, use #gid. When running commands as a gid,
many shells require that the '#' be escaped with
a backslash ('\'). If no -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 group.
-H The -H (HOME) option sets the HOME environment
variable to the homedir of the target user (root
by default) as specified in passwd(4). By
default, sudo does not modify HOME (see set_home
and always_set_home in sudoers(4)).
-h The -h (help) option causes sudo to print a
usage message and exit.
-i [command]
The -i (simulate initial login) option runs the
shell specified in the passwd(4) entry of the
target user as a login shell. This means that
login-specific resource files such as .profile
or .login will be read by the shell. If a
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MAINTENANCE COMMANDS SUDO(1m)
command is specified, it is passed to the shell
for execution. Otherwise, an interactive shell
is executed. sudo attempts to change to that
user's home directory before running the shell.
It also initializes the environment, leaving
DISPLAY and TERM unchanged, setting HOME, SHELL,
USER, LOGNAME, and PATH, as well as the contents
of /etc/environment on Linux and AIX systems.
All other environment variables are removed.
-K The -K (sure kill) option is like -k except that
it removes the user's timestamp entirely. Like
-k, this option does not require a password.
-k The -k (kill) option to sudo invalidates the
user's timestamp by setting the time on it to
the Epoch. The next time sudo is run a password
will be required. This option does not require
a password and was added to allow a user to
revoke sudo permissions from a .logout file.
-L The -L (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).
-l[l] [command]
If no command is specified, the -l (list) option
will list the allowed (and forbidden) commands
for the invoking user (or the user specified by
the -U option) on the current host. If a
command is specified and is permitted by
sudoers, the fully-qualified path to the command
is displayed along with any command line
arguments. If command is specified but not
allowed, sudo will exit with a status value of
1. If the -l option is specified with an l
argument (i.e. -ll), or if -l is specified
multiple times, a longer list format is used.
-n The -n (non-interactive) option prevents sudo
from prompting the user for a password. If a
password is required for the command to run,
sudo will display an error messages and exit.
-P The -P (preserve group vector) option causes
sudo to preserve the invoking user's group
vector unaltered. By default, 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.
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-p prompt The -p (prompt) option allows you to override
the default password prompt and use a custom
one. The following percent (`%') escapes are
supported:
%H expanded to the local hostname including the
domain name (on if the machine's hostname is
fully qualified or the fqdn sudoers option
is set)
%h expanded to the local hostname without the
domain name
%p expanded to the user whose password is being
asked for (respects the rootpw, targetpw and
runaspw flags in sudoers)
%U expanded to the login name of the user the
command will be run as (defaults to root)
%u expanded to the invoking user's login name
%% two consecutive % characters are collapsed
into a single % character
The prompt specified by the -p option will
override the system password prompt on systems
that support PAM unless the passprompt_override
flag is disabled in sudoers.
-S The -S (stdin) option causes sudo to read the
password from the standard input instead of the
terminal device.
-s [command]
The -s (shell) option runs the shell specified
by the SHELL environment variable if it is set
or the shell as specified in passwd(4). If a
command is specified, it is passed to the shell
for execution. Otherwise, an interactive shell
is executed.
-U user The -U (other user) option is used in
conjunction with the -l option to specify the
user whose privileges should be listed. Only
root or a user with sudo ALL on the current host
may use this option.
-u user The -u (user) option causes sudo to run the
specified command as a user other than root. To
specify a uid instead of a user name, use #uid.
When running commands as a uid, many shells
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MAINTENANCE COMMANDS SUDO(1m)
require that the '#' be escaped with a backslash
('\'). Note that if the targetpw Defaults
option is set (see sudoers(4)) it is not
possible to run commands with a uid not listed
in the password database.
-V The -V (version) option causes sudo to print the
version number and exit. If the invoking user
is already root the -V option will print out a
list of the defaults sudo was compiled with as
well as the machine's local network addresses.
-v If given the -v (validate) option, sudo will
update the user's timestamp, prompting for the
user's password if necessary. This extends the
sudo timeout for another 5 minutes (or whatever
the timeout is set to in sudoers) but does not
run a command.
-- The -- option indicates that sudo should stop
processing command line arguments. It is most
useful in conjunction with the -s option.
Environment variables to be set for the command may also be
passed on the command line in the form of VAR=value, e.g.
LD_LIBRARY_PATH=/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
setenv option is set in sudoers, the command to be run has
the SETENV tag set or the command matched is ALL, the user
may set variables that would overwise be forbidden. See
sudoers(4) for more information.
RETURN VALUES
Upon successful execution of a program, the exit status from
sudo will simply be the exit status of the program that was
executed.
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.
SECURITY NOTES
sudo tries to be safe when executing external commands.
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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
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MAINTENANCE COMMANDS SUDO(1m)
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(4).
ENVIRONMENT
sudo utilizes the following environment variables:
EDITOR Default editor to use in -e (sudoedit) mode
if neither SUDO_EDITOR nor VISUAL is set
HOME In -s or -H mode (or if sudo was configured
with the --enable-shell-sets-home option),
set to homedir of the target user
PATH Set to a sane value if the secure_path
sudoers option is set.
SHELL Used to determine shell to run with -s
option
SUDO_ASKPASS Specifies the path to a helper program used
to read the password if no terminal is
available or if the -A option is specified.
SUDO_COMMAND Set to the command run by sudo
SUDO_EDITOR Default editor to use in -e (sudoedit) mode
SUDO_GID Set to the group ID of the user who invoked
sudo
SUDO_PROMPT Used as the default password prompt
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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 of the user who invoked
sudo
USER Set to the target user (root unless the -u
option is specified)
VISUAL Default editor to use in -e (sudoedit) mode
if SUDO_EDITOR is not set
FILES
/etc/sudoers List of who can run what
/var/run/sudo Directory containing timestamps
/etc/environment Initial environment for -i mode on
Linux and AIX
EXAMPLES
Note: the following examples assume suitable sudoers(4)
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), passwd(4), sudoers(5), visudo(1m)
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AUTHORS
Many people have worked on sudo over the years; this version
consists of code written primarily by:
Todd C. Miller
See the HISTORY file in the sudo distribution or visit
http://www.sudo.ws/sudo/history.html for a short history of
sudo.
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
sudo. Also, many programs (such as editors) allow the user
to run commands via shell escapes, thus avoiding sudo's
checks. However, on most systems it is possible to prevent
shell escapes with sudo's noexec functionality. See the
sudoers(4) manual for details.
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).
BUGS
If you feel you have found a bug in sudo, please submit a
bug report at http://www.sudo.ws/sudo/bugs/
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.
DISCLAIMER
sudo 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 sudo or http://www.sudo.ws/sudo/license.html for
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MAINTENANCE COMMANDS SUDO(1m)
complete details.
ATTRIBUTES
See attributes(5) for descriptions of the following
attributes:
_____________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| Availability | SUNWsudor, SUNWsudou|
| Interface Stability | Uncommitted |
|___________________________________________|
NOTES
sudo does not create audit(2) records; for a Role Based
administration solution that performs auditing of all
actions, please refer to rbac(5).
Source for sudo is available on http://opensolaris.org.
1.7.0 Last change: November 15, 2008 11
--- sudo(1m) ----
MAINTENANCE COMMANDS SUDOERS(4)
NAME
sudoers - list of which users may execute what
DESCRIPTION
The sudoers file is composed of two types of entries:
aliases (basically variables) and user specifications (which
specify who may run what).
When multiple entries match for a user, they are applied in
order. Where there are multiple matches, the last match is
used (which is not necessarily the most specific match).
The sudoers grammar will be described below in Extended
Backus-Naur Form (EBNF). Don't despair if you don't know
what EBNF is; it is fairly simple, and the definitions below
are annotated.
Quick guide to EBNF
EBNF is a concise and exact way of describing the grammar of
a language. Each EBNF definition is made up of production
rules. E.g.,
symbol ::= definition | alternate1 | alternate2 ...
Each production rule references others and thus makes up a
grammar for the language. EBNF also contains the following
operators, which many readers will recognize from regular
expressions. Do not, however, confuse them with "wildcard"
characters, which have different meanings.
? Means that the preceding symbol (or group of symbols) is
optional. That is, it may appear once or not at all.
* Means that the preceding symbol (or group of symbols)
may appear zero or more times.
+ Means that the preceding symbol (or group of symbols)
may appear one or more times.
Parentheses may be used to group symbols together. For
clarity, we will use single quotes ('') to designate what is
a verbatim character string (as opposed to a symbol name).
Aliases
There are four kinds of aliases: User_Alias, Runas_Alias,
Host_Alias and Cmnd_Alias.
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Alias ::= 'User_Alias' User_Alias (':' User_Alias)* |
'Runas_Alias' Runas_Alias (':' Runas_Alias)* |
'Host_Alias' Host_Alias (':' Host_Alias)* |
'Cmnd_Alias' Cmnd_Alias (':' Cmnd_Alias)*
User_Alias ::= NAME '=' User_List
Runas_Alias ::= NAME '=' Runas_List
Host_Alias ::= NAME '=' Host_List
Cmnd_Alias ::= NAME '=' Cmnd_List
NAME ::= [A-Z]([A-Z][0-9]_)*
Each alias definition is of the form
Alias_Type NAME = item1, item2, ...
where Alias_Type is one of User_Alias, Runas_Alias,
Host_Alias, or Cmnd_Alias. A NAME is a string of uppercase
letters, numbers, and underscore characters ('_'). A NAME
must start with an uppercase letter. It is possible to put
several alias definitions of the same type on a single line,
joined by a colon (':'). E.g.,
Alias_Type NAME = item1, item2, item3 : NAME = item4, item5
The definitions of what constitutes a valid alias member
follow.
User_List ::= User |
User ',' User_List
User ::= '!'* username |
'!'* '#'uid |
'!'* '%'group |
'!'* '+'netgroup |
'!'* User_Alias
A User_List is made up of one or more usernames, uids
(prefixed with '#'), system groups (prefixed with '%'),
netgroups (prefixed with '+') and User_Aliases. Each list
item may be prefixed with zero or more '!' operators. An
odd number of '!' operators negate the value of the item; an
even number just cancel each other out.
Runas_List ::= Runas_Member |
Runas_Member ',' Runas_List
Runas_Member ::= '!'* username |
'!'* '#'uid |
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'!'* '%'group |
'!'* +netgroup |
'!'* Runas_Alias
A Runas_List is similar to a User_List except that instead
of User_Aliases it can contain Runas_Aliases. Note that
usernames and groups are matched as strings. In other
words, two users (groups) with the same uid (gid) are
considered to be distinct. If you wish to match all
usernames with the same uid (e.g. root and toor), you can
use a uid instead (#0 in the example given).
Host_List ::= Host |
Host ',' Host_List
Host ::= '!'* hostname |
'!'* ip_addr |
'!'* network(/netmask)? |
'!'* '+'netgroup |
'!'* Host_Alias
A Host_List is made up of one or more hostnames, IP
addresses, network numbers, netgroups (prefixed with '+')
and other aliases. Again, the value of an item may be
negated with the '!' operator. If you do not specify a
netmask along with the network number, sudo will query each
of the local host's network interfaces and, if the network
number corresponds to one of the hosts's network interfaces,
the corresponding netmask will be used. The netmask may be
specified either in standard IP address notation
(e.g. 255.255.255.0 or ffff:ffff:ffff:ffff::), or CIDR
notation (number of bits, e.g. 24 or 64). A hostname may
include shell-style wildcards (see the Wildcards section
below), but unless the hostname command on your machine
returns the fully qualified hostname, you'll need to use the
fqdn option for wildcards to be useful.
Cmnd_List ::= Cmnd |
Cmnd ',' Cmnd_List
commandname ::= filename |
filename args |
filename '""'
Cmnd ::= '!'* commandname |
'!'* directory |
'!'* "sudoedit" |
'!'* Cmnd_Alias
A Cmnd_List is a list of one or more commandnames,
directories, and other aliases. A commandname is a fully
qualified filename which may include shell-style wildcards
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(see the Wildcards section below). A simple filename allows
the user to run the command with any arguments he/she
wishes. However, you may also specify command line
arguments (including wildcards). Alternately, you can
specify "" to indicate that the command may only be run
without command line arguments. A directory is a fully
qualified pathname ending in a '/'. When you specify a
directory in a Cmnd_List, the user will be able to run any
file within that directory (but not in any subdirectories
therein).
If a Cmnd has associated command line arguments, then the
arguments in the Cmnd must match exactly those given by the
user on the command line (or match the wildcards if there
are any). Note that the following characters must be
escaped with a '\' if they are used in command arguments:
',', ':', '=', '\'. The special command "sudoedit" is used
to permit a user to run sudo with the -e option (or as
sudoedit). It may take command line arguments just as a
normal command does.
Defaults
Certain configuration options may be changed from their
default values at runtime via one or more Default_Entry
lines. These may affect all users on any host, all users on
a specific host, a specific user, a specific command, or
commands being run as a specific user. Note that per-
command entries may not include command line arguments. If
you need to specify arguments, define a Cmnd_Alias and
reference that instead.
Default_Type ::= 'Defaults' |
'Defaults' '@' Host_List |
'Defaults' ':' User_List |
'Defaults' '!' Cmnd_List |
'Defaults' '>' Runas_List
Default_Entry ::= Default_Type Parameter_List
Parameter_List ::= Parameter |
Parameter ',' Parameter_List
Parameter ::= Parameter '=' Value |
Parameter '+=' Value |
Parameter '-=' Value |
'!'* Parameter
Parameters may be flags, integer values, strings, or lists.
Flags are implicitly boolean and can be turned off via the
'!' operator. Some integer, string and list parameters may
also be used in a boolean context to disable them. Values
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may be enclosed in double quotes (") when they contain
multiple words. Special characters may be escaped with a
backslash (\).
Lists have two additional assignment operators, += and -=.
These operators are used to add to and delete from a list
respectively. It is not an error to use the -= operator to
remove an element that does not exist in a list.
Defaults entries are parsed in the following order: generic,
host and user Defaults first, then runas Defaults and
finally command defaults.
See "SUDOERS OPTIONS" for a list of supported Defaults
parameters.
User Specification
User_Spec ::= User_List Host_List '=' Cmnd_Spec_List \
(':' Host_List '=' Cmnd_Spec_List)*
Cmnd_Spec_List ::= Cmnd_Spec |
Cmnd_Spec ',' Cmnd_Spec_List
Cmnd_Spec ::= Runas_Spec? Tag_Spec* Cmnd
Runas_Spec ::= '(' Runas_List? (: Runas_List)? ')'
Tag_Spec ::= ('NOPASSWD:' | 'PASSWD:' | 'NOEXEC:' | 'EXEC:' |
'SETENV:' | 'NOSETENV:' )
A user specification determines which commands a user may
run (and as what user) on specified hosts. By default,
commands are run as root, but this can be changed on a per-
command basis.
Let's break that down into its constituent parts:
Runas_Spec
A Runas_Spec determines the user and/or the group that a
command may be run as. A fully-specified Runas_Spec
consists of two Runas_Lists (as defined above) separated by
a colon (':') and enclosed in a set of parentheses. The
first Runas_List indicates which users the command may be
run as via sudo's -u option. The second defines a list of
groups that can be specified via sudo's -g option. If both
Runas_Lists are specified, the command may be run with any
combination of users and groups listed in their respective
Runas_Lists. If only the first is specified, the command
may be run as any user in the list but no -g option may be
specified. If the first Runas_List is empty but the second
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is specified, the command may be run as the invoking user
with the group set to any listed in the Runas_List. If no
Runas_Spec is specified the command may be run as root and
no group may be specified.
A Runas_Spec sets the default for the commands that follow
it. What this means is that for the entry:
dgb boulder = (operator) /bin/ls, /bin/kill, /usr/bin/lprm
The user dgb may run /bin/ls, /bin/kill, and /usr/bin/lprm
-- but only as operator. E.g.,
$ sudo -u operator /bin/ls.
It is also possible to override a Runas_Spec later on in an
entry. If we modify the entry like so:
dgb boulder = (operator) /bin/ls, (root) /bin/kill, /usr/bin/lprm
Then user dgb is now allowed to run /bin/ls as operator, but
/bin/kill and /usr/bin/lprm as root.
We can extend this to allow dgb to run /bin/ls with either
the user or group set to operator:
dgb boulder = (operator : operator) /bin/ls, (root) /bin/kill, \
/usr/bin/lprm
In the following example, user tcm may run commands that
access a modem device file with the dialer group. Note that
in this example only the group will be set, the command
still runs as user tcm.
tcm boulder = (:dialer) /usr/bin/tip, /usr/bin/cu, \
/usr/local/bin/minicom
Tag_Spec
A command may have zero or more tags associated with it.
There are eight possible tag values, NOPASSWD, PASSWD,
NOEXEC, EXEC, SETENV and NOSETENV. Once a tag is set on a
Cmnd, subsequent Cmnds in the Cmnd_Spec_List, inherit the
tag unless it is overridden by the opposite tag (i.e.:
PASSWD overrides NOPASSWD and NOEXEC overrides EXEC).
NOPASSWD and PASSWD
By default, sudo requires that a user authenticate him or
herself before running a command. This behavior can be
modified via the NOPASSWD tag. Like a Runas_Spec, the
NOPASSWD tag sets a default for the commands that follow it
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in the Cmnd_Spec_List. Conversely, the PASSWD tag can be
used to reverse things. For example:
ray rushmore = NOPASSWD: /bin/kill, /bin/ls, /usr/bin/lprm
would allow the user ray to run /bin/kill, /bin/ls, and
/usr/bin/lprm as root on the machine rushmore without
authenticating himself. If we only want ray to be able to
run /bin/kill without a password the entry would be:
ray rushmore = NOPASSWD: /bin/kill, PASSWD: /bin/ls, /usr/bin/lprm
Note, however, that the PASSWD tag has no effect on users
who are in the group specified by the exempt_group option.
By default, if the NOPASSWD tag is applied to any of the
entries for a user on the current host, he or she will be
able to run sudo -l without a password. Additionally, a
user may only run sudo -v without a password if the NOPASSWD
tag is present for all a user's entries that pertain to the
current host. This behavior may be overridden via the
verifypw and listpw options.
NOEXEC and EXEC
If sudo has been compiled with noexec support and the
underlying operating system supports it, the NOEXEC tag can
be used to prevent a dynamically-linked executable from
running further commands itself.
In the following example, user aaron may run /usr/bin/more
and /usr/bin/vi but shell escapes will be disabled.
aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
See the "PREVENTING SHELL ESCAPES" section below for more
details on how NOEXEC works and whether or not it will work
on your system.
SETENV and NOSETENV
These tags override the value of the setenv option on a per-
command basis. Note that if SETENV has been set for a
command, any environment variables set on the command line
way are not subject to the restrictions imposed by
env_check, env_delete, or env_keep. As such, only trusted
users should be allowed to set variables in this manner. If
the command matched is ALL, the SETENV tag is implied for
that command; this default may be overridden by use of the
UNSETENV tag.
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Wildcards
sudo allows shell-style wildcards (aka meta or glob
characters) to be used in hostnames, pathnames and command
line arguments in the sudoers file. Wildcard matching is
done via the POSIX fnmatch(3) routine. Note that these are
not regular expressions.
* Matches any set of zero or more characters.
? Matches any single character.
[...] Matches any character in the specified range.
[!...] Matches any character not in the specified range.
\x For any character "x", evaluates to "x". This is
used to escape special characters such as: "*", "?",
"[", and "}".
POSIX character classes may also be used if your system's
fnmatch(3) function supports them. However, because the ':'
character has special meaning in sudoers, it must be
escaped. For example:
/bin/ls [[\:alpha\:]]*
Would match any filename beginning with a letter.
Note that a forward slash ('/') will not be matched by
wildcards used in the pathname. When matching the command
line arguments, however, a slash does get matched by
wildcards. This is to make a path like:
/usr/bin/*
match /usr/bin/who but not /usr/bin/X11/xterm.
Exceptions to wildcard rules
The following exceptions apply to the above rules:
"" If the empty string "" is the only command line
argument in the sudoers entry it means that command
is not allowed to be run with any arguments.
Including other files from within sudoers
It is possible to include other sudoers files from within
the sudoers file currently being parsed using the #include
directive, similar to the one used by the C preprocessor.
This is useful, for example, for keeping a site-wide sudoers
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file in addition to a per-machine local one. For the sake
of this example the site-wide sudoers will be /etc/sudoers
and the per-machine one will be /etc/sudoers.local. To
include /etc/sudoers.local from /etc/sudoers we would use
the following line in /etc/sudoers:
#include /etc/sudoers.local
When sudo reaches this line it will suspend processing of
the current file (/etc/sudoers) and switch to
/etc/sudoers.local. Upon reaching the end of
/etc/sudoers.local, the rest of /etc/sudoers will be
processed. Files that are included may themselves include
other files. A hard limit of 128 nested include files is
enforced to prevent include file loops.
Other special characters and reserved words
The pound sign ('#') is used to indicate a comment (unless
it is part of a #include directive or unless it occurs in
the context of a user name and is followed by one or more
digits, in which case it is treated as a uid). Both the
comment character and any text after it, up to the end of
the line, are ignored.
The reserved word ALL is a built-in alias that always causes
a match to succeed. It can be used wherever one might
otherwise use a Cmnd_Alias, User_Alias, Runas_Alias, or
Host_Alias. You should not try to define your own alias
called ALL as the built-in alias will be used in preference
to your own. Please note that using ALL can be dangerous
since in a command context, it allows the user to run any
command on the system.
An exclamation point ('!') can be used as a logical not
operator both in an alias and in front of a Cmnd. This
allows one to exclude certain values. Note, however, that
using a ! in conjunction with the built-in ALL alias to
allow a user to run "all but a few" commands rarely works as
intended (see SECURITY NOTES below).
Long lines can be continued with a backslash ('\') as the
last character on the line.
Whitespace between elements in a list as well as special
syntactic characters in a User Specification ('=', ':', '(',
')') is optional.
The following characters must be escaped with a backslash
('\') when used as part of a word (e.g. a username or
hostname): '@', '!', '=', ':', ',', '(', ')', '\'.
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SUDOERS OPTIONS
sudo's behavior can be modified by Default_Entry lines, as
explained earlier. A list of all supported Defaults
parameters, grouped by type, are listed below.
Flags:
always_set_home If set, sudo will set the HOME environment
variable to the home directory of the target
user (which is root unless the -u option is
used). This effectively means that the -H
option is always implied. This flag is off
by default.
authenticate If set, users must authenticate themselves
via a password (or other means of
authentication) before they may run
commands. This default may be overridden
via the PASSWD and NOPASSWD tags. This flag
is on by default.
closefrom_override
If set, the user may use sudo's -C option
which overrides the default starting point
at which sudo begins closing open file
descriptors. This flag is off by default.
env_editor If set, visudo will use the value of the
EDITOR or VISUAL environment variables
before falling back on the default editor
list. Note that this may create a security
hole as it allows the user to run any
arbitrary command as root without logging.
A safer alternative is to place a colon-
separated list of editors in the editor
variable. visudo will then only use the
EDITOR or VISUAL if they match a value
specified in editor. This flag is off by
default.
env_reset If set, sudo will reset the environment to
only contain the LOGNAME, SHELL, USER,
USERNAME and the SUDO_* variables. Any
variables in the caller's environment that
match the env_keep and env_check lists are
then added. The default contents of the
env_keep and env_check lists are displayed
when sudo is run by root with the -V option.
If the secure_path option is set, its value
will be used for the PATH environment
variable. This flag is on by default.
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fqdn Set this flag if you want to put fully
qualified hostnames in the sudoers file.
I.e., instead of myhost you would use
myhost.mydomain.edu. You may still use the
short form if you wish (and even mix the
two). Beware that turning on fqdn requires
sudo to make DNS lookups which may make sudo
unusable if DNS stops working (for example
if the machine is not plugged into the
network). Also note that you must use the
host's official name as DNS knows it. That
is, you may not use a host alias (CNAME
entry) due to performance issues and the
fact that there is no way to get all aliases
from DNS. If your machine's hostname (as
returned by the hostname command) is already
fully qualified you shouldn't need to set
fqdn. This flag is off by default.
ignore_dot If set, sudo will ignore '.' or '' (current
dir) in the PATH environment variable; the
PATH itself is not modified. This flag is
off by default.
ignore_local_sudoers
If set via LDAP, parsing of /etc/sudoers
will be skipped. This is intended for
Enterprises that wish to prevent the usage
of local sudoers files so that only LDAP is
used. This thwarts the efforts of rogue
operators who would attempt to add roles to
/etc/sudoers. When this option is present,
/etc/sudoers does not even need to exist.
Since this option tells sudo how to behave
when no specific LDAP entries have been
matched, this sudoOption is only meaningful
for the cn=defaults section. This flag is
off by default.
insults If set, sudo will insult users when they
enter an incorrect password. This flag is
off by default.
log_host If set, the hostname will be logged in the
(non-syslog) sudo log file. This flag is
off by default.
log_year If set, the four-digit year will be logged
in the (non-syslog) sudo log file. This
flag is off by default.
long_otp_prompt When validating with a One Time Password
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(OPT) scheme such as S/Key or OPIE, a two-
line prompt is used to make it easier to cut
and paste the challenge to a local window.
It's not as pretty as the default but some
people find it more convenient. This flag
is off by default.
mail_always Send mail to the mailto user every time a
users runs sudo. This flag is off by
default.
mail_badpass Send mail to the mailto user if the user
running sudo does not enter the correct
password. This flag is off by default.
mail_no_host If set, mail will be sent to the mailto user
if the invoking user exists in the sudoers
file, but is not allowed to run commands on
the current host. This flag is off by
default.
mail_no_perms If set, mail will be sent to the mailto user
if the invoking user is allowed to use sudo
but the command they are trying is not
listed in their sudoers file entry or is
explicitly denied. This flag is off by
default.
mail_no_user If set, mail will be sent to the mailto user
if the invoking user is not in the sudoers
file. This flag is on by default.
noexec If set, all commands run via sudo will
behave as if the NOEXEC tag has been set,
unless overridden by a EXEC tag. See the
description of NOEXEC and EXEC below as well
as the "PREVENTING SHELL ESCAPES" section at
the end of this manual. This flag is off by
default.
path_info Normally, sudo will tell the user when a
command could not be found in their PATH
environment variable. Some sites may wish
to disable this as it could be used to
gather information on the location of
executables that the normal user does not
have access to. The disadvantage is that if
the executable is simply not in the user's
PATH, sudo will tell the user that they are
not allowed to run it, which can be
confusing. This flag is on by default.
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passprompt_override
The password prompt specified by passprompt
will normally only be used if the passwod
prompt provided by systems such as PAM
matches the string "Password:". If
passprompt_override is set, passprompt will
always be used. This flag is off by
default.
preserve_groups By default sudo will initialize the group
vector to the list of groups the target user
is in. When preserve_groups is set, the
user's existing group vector is left
unaltered. The real and effective group
IDs, however, are still set to match the
target user. This flag is off by default.
requiretty If set, sudo will only run when the user is
logged in to a real tty. When this flag is
set, sudo can only be run from a login
session and not via other means such as
cron(1m) or cgi-bin scripts. This flag is
off by default.
root_sudo If set, root is allowed to run sudo too.
Disabling this prevents users from
"chaining" sudo commands to get a root shell
by doing something like "sudo sudo /bin/sh".
Note, however, that turning off root_sudo
will also prevent root and from running
sudoedit. Disabling root_sudo provides no
real additional security; it exists purely
for historical reasons. This flag is on by
default.
rootpw If set, sudo will prompt for the root
password instead of the password of the
invoking user. This flag is off by default.
runaspw If set, sudo will prompt for the password of
the user defined by the runas_default option
(defaults to root) instead of the password
of the invoking user. This flag is off by
default.
set_home If set and sudo is invoked with the -s
option the HOME environment variable will be
set to the home directory of the target user
(which is root unless the -u option is
used). This effectively makes the -s option
imply -H. This flag is off by default.
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set_logname Normally, sudo will set the LOGNAME, USER
and USERNAME environment variables to the
name of the target user (usually root unless
the -u option is given). However, since
some programs (including the RCS revision
control system) use LOGNAME to determine the
real identity of the user, it may be
desirable to change this behavior. This can
be done by negating the set_logname option.
Note that if the env_reset option has not
been disabled, entries in the env_keep list
will override the value of set_logname.
This flag is off by default.
setenv Allow the user to disable the env_reset
option from the command line. Additionally,
environment variables set via the command
line are not subject to the restrictions
imposed by env_check, env_delete, or
env_keep. As such, only trusted users
should be allowed to set variables in this
manner. This flag is off by default.
shell_noargs If set and sudo is invoked with no arguments
it acts as if the -s option had been given.
That is, it runs a shell as root (the shell
is determined by the SHELL environment
variable if it is set, falling back on the
shell listed in the invoking user's
/etc/passwd entry if not). This flag is off
by default.
stay_setuid Normally, when sudo executes a command the
real and effective UIDs are set to the
target user (root by default). This option
changes that behavior such that the real UID
is left as the invoking user's UID. In
other words, this makes sudo act as a setuid
wrapper. This can be useful on systems that
disable some potentially dangerous
functionality when a program is run setuid.
This option is only effective on systems
with either the setreuid() or setresuid()
function. This flag is off by default.
targetpw If set, sudo will prompt for the password of
the user specified by the -u option
(defaults to root) instead of the password
of the invoking user. Note that this
precludes the use of a uid not listed in the
passwd database as an argument to the -u
option. This flag is off by default.
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tty_tickets If set, users must authenticate on a per-tty
basis. Normally, sudo uses a directory in
the ticket dir with the same name as the
user running it. With this flag enabled,
sudo will use a file named for the tty the
user is logged in on in that directory.
This flag is off by default.
visiblepw By default, sudo will refuse to run if the
user must enter a password but it is not
possible to disable echo on the terminal.
If the visiblepw flag is set, sudo will
prompt for a password even when it would be
visible on the screen. This makes it
possible to run things like "rsh somehost
sudo ls" since rsh(1) does not allocate a
tty. This flag is off by default.
Integers:
closefrom Before it executes a command, sudo will
close all open file descriptors other than
standard input, standard output and standard
error (ie: file descriptors 0-2). The
closefrom option can be used to specify a
different file descriptor at which to start
closing. The default is 3.
passwd_tries The number of tries a user gets to enter
his/her password before sudo logs the
failure and exits. The default is 3.
Integers that can be used in a boolean context:
loglinelen Number of characters per line for the file
log. This value is used to decide when to
wrap lines for nicer log files. This has no
effect on the syslog log file, only the file
log. The default is 80 (use 0 or negate the
option to disable word wrap).
passwd_timeout Number of minutes before the sudo password
prompt times out. The default is 5; set
this to 0 for no password timeout.
timestamp_timeout
Number of minutes that can elapse before
sudo will ask for a passwd again. The
default is 5. Set this to 0 to always
prompt for a password. If set to a value
less than 0 the user's timestamp will never
expire. This can be used to allow users to
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create or delete their own timestamps via
sudo -v and sudo -k respectively.
umask Umask to use when running the command.
Negate this option or set it to 0777 to
preserve the user's umask. The actual umask
that is used will be the union of the user's
umask and 0022. This guarantees that sudo
never lowers the umask when running a
command. Note on systems that use PAM, the
default PAM configuration may specify its
own umask which will override the value set
in sudoers.
Strings:
badpass_message Message that is displayed if a user enters
an incorrect password. The default is
Sorry, try again. unless insults are
enabled.
editor A colon (':') separated list of editors
allowed to be used with visudo. visudo will
choose the editor that matches the user's
EDITOR environment variable if possible, or
the first editor in the list that exists and
is executable. The default is the path to
vi on your system.
mailsub Subject of the mail sent to the mailto user.
The escape %h will expand to the hostname of
the machine. Default is *** SECURITY
information for %h ***.
noexec_file Path to a shared library containing dummy
versions of the execv(), execve() and
fexecve() library functions that just return
an error. This is used to implement the
noexec functionality on systems that support
LD_PRELOAD or its equivalent. Defaults to
/usr/lib/sudo_noexec.so.
passprompt The default prompt to use when asking for a
password; can be overridden via the -p
option or the SUDO_PROMPT environment
variable. The following percent (`%')
escapes are supported:
%H expanded to the local hostname including
the domain name (on if the machine's
hostname is fully qualified or the fqdn
option is set)
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%h expanded to the local hostname without
the domain name
%p expanded to the user whose password is
being asked for (respects the rootpw,
targetpw and runaspw flags in sudoers)
%U expanded to the login name of the user
the command will be run as (defaults to
root)
%u expanded to the invoking user's login
name
%% two consecutive % characters are
collapsed into a single % character
The default value is Password:.
runas_default The default user to run commands as if the
-u option is not specified on the command
line. This defaults to root. Note that if
runas_default is set it must occur before
any Runas_Alias specifications.
syslog_badpri Syslog priority to use when user
authenticates unsuccessfully. Defaults to
alert.
syslog_goodpri Syslog priority to use when user
authenticates successfully. Defaults to
notice.
sudoers_locale Locale to use when parsing the sudoers file.
Note that changing the locale may affect how
sudoers is interpreted. Defaults to "C".
timestampdir The directory in which sudo stores its
timestamp files. The default is
/var/run/sudo.
timestampowner The owner of the timestamp directory and the
timestamps stored therein. The default is
root.
Strings that can be used in a boolean context:
askpass The askpass option specifies the fully qualified
path to a helper program used to read the user's
password when no terminal is available. This
may be the case when sudo is executed from a
graphical (as opposed to text-based)
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application. The program specified by askpass
should display the argument passed to it as the
prompt and write the user's password to the
standard output. The value of askpass may be
overridden by the SUDO_ASKPASS environment
variable.
env_file The env_file options specifies the fully
qualified path to a file containing variables to
be set in the environment of the program being
run. Entries in this file should be of the form
VARIABLE=value. Variables in this file are
subject to other sudo environment settings such
as env_keep and env_check.
exempt_group
Users in this group are exempt from password and
PATH requirements. This is not set by default.
lecture This option controls when a short lecture will
be printed along with the password prompt. It
has the following possible values:
always Always lecture the user.
never Never lecture the user.
once Only lecture the user the first time
they run sudo.
If no value is specified, a value of once is
implied. Negating the option results in a value
of never being used. The default value is once.
lecture_file
Path to a file containing an alternate sudo
lecture that will be used in place of the
standard lecture if the named file exists. By
default, sudo uses a built-in lecture.
listpw This option controls when a password will be
required when a user runs sudo with the -l
option. It has the following possible values:
all All the user's sudoers entries for the
current host must have the NOPASSWD flag
set to avoid entering a password.
always The user must always enter a password to
use the -l option.
any At least one of the user's sudoers
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entries for the current host must have
the NOPASSWD flag set to avoid entering
a password.
never The user need never enter a password to
use the -l option.
If no value is specified, a value of any is
implied. Negating the option results in a value
of never being used. The default value is any.
logfile Path to the sudo log file (not the syslog log
file). Setting a path turns on logging to a
file; negating this option turns it off. By
default, sudo logs via syslog.
mailerflags Flags to use when invoking mailer. Defaults to
-t.
mailerpath Path to mail program used to send warning mail.
Defaults to the path to sendmail found at
configure time.
mailfrom Address to use for the "from" address when
sending warning and error mail. The address
should be enclosed in double quotes (") to
protect against sudo interpreting the @ sign.
Defaults to the name of the user running sudo.
mailto Address to send warning and error mail to. The
address should be enclosed in double quotes (")
to protect against sudo interpreting the @ sign.
Defaults to root.
secure_path Path used for every command run from sudo. If
you don't trust the people running sudo to have
a sane PATH environment variable you may want to
use this. Another use is if you want to have
the "root path" be separate from the "user
path." Users in the group specified by the
exempt_group option are not affected by
secure_path. This is not set by default.
syslog Syslog facility if syslog is being used for
logging (negate to disable syslog logging).
Defaults to local2.
verifypw This option controls when a password will be
required when a user runs sudo with the -v
option. It has the following possible values:
all All the user's sudoers entries for the
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current host must have the NOPASSWD flag
set to avoid entering a password.
always The user must always enter a password to
use the -v option.
any At least one of the user's sudoers
entries for the current host must have
the NOPASSWD flag set to avoid entering
a password.
never The user need never enter a password to
use the -v option.
If no value is specified, a value of all is
implied. Negating the option results in a value
of never being used. The default value is all.
Lists that can be used in a boolean context:
env_check Environment variables to be removed from the
user's environment if the variable's value
contains % or / characters. This can be
used to guard against printf-style format
vulnerabilities in poorly-written programs.
The argument may be a double-quoted, space-
separated list or a single value without
double-quotes. The list can be replaced,
added to, deleted from, or disabled by using
the =, +=, -=, and ! operators respectively.
Regardless of whether the env_reset option
is enabled or disabled, variables specified
by env_check will be preserved in the
environment if they pass the aforementioned
check. The default list of environment
variables to check is displayed when sudo is
run by root with the -V option.
env_delete Environment variables to be removed from the
user's environment. The argument may be a
double-quoted, space-separated list or a
single value without double-quotes. The
list can be replaced, added to, deleted
from, or disabled by using the =, +=, -=,
and ! operators respectively. The default
list of environment variables to remove is
displayed when sudo is run by root with the
-V option. Note that many operating systems
will remove potentially dangerous variables
from the environment of any setuid process
(such as sudo).
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env_keep Environment variables to be preserved in the
user's environment when the env_reset option
is in effect. This allows fine-grained
control over the environment sudo-spawned
processes will receive. The argument may be
a double-quoted, space-separated list or a
single value without double-quotes. The
list can be replaced, added to, deleted
from, or disabled by using the =, +=, -=,
and ! operators respectively. The default
list of variables to keep is displayed when
sudo is run by root with the -V option.
When logging via syslog(3), sudo accepts the following
values for the syslog facility (the value of the syslog
Parameter): authpriv (if your OS supports it), auth, daemon,
user, local0, local1, local2, local3, local4, local5,
local6, and local7. The following syslog priorities are
supported: alert, crit, debug, emerg, err, info, notice, and
warning.
FILES
/etc/sudoers List of who can run what
/etc/group Local groups file
/etc/netgroup List of network groups
EXAMPLES
Below are example sudoers entries. Admittedly, some of
these are a bit contrived. First, we define our aliases:
# User alias specification
User_Alias FULLTIMERS = millert, mikef, dowdy
User_Alias PARTTIMERS = bostley, jwfox, crawl
User_Alias WEBMASTERS = will, wendy, wim
# Runas alias specification
Runas_Alias OP = root, operator
Runas_Alias DB = oracle, sybase
# Host alias specification
Host_Alias SPARC = bigtime, eclipse, moet, anchor :\
SGI = grolsch, dandelion, black :\
ALPHA = widget, thalamus, foobar :\
HPPA = boa, nag, python
Host_Alias CUNETS = 128.138.0.0/255.255.0.0
Host_Alias CSNETS = 128.138.243.0, 128.138.204.0/24, 128.138.242.0
Host_Alias SERVERS = master, mail, www, ns
Host_Alias CDROM = orion, perseus, hercules
# Cmnd alias specification
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Cmnd_Alias DUMPS = /usr/bin/mt, /usr/sbin/dump, /usr/sbin/rdump,\
/usr/sbin/restore, /usr/sbin/rrestore
Cmnd_Alias KILL = /usr/bin/kill
Cmnd_Alias PRINTING = /usr/sbin/lpc, /usr/bin/lprm
Cmnd_Alias SHUTDOWN = /usr/sbin/shutdown
Cmnd_Alias HALT = /usr/sbin/halt
Cmnd_Alias REBOOT = /usr/sbin/reboot
Cmnd_Alias SHELLS = /usr/bin/sh, /usr/bin/csh, /usr/bin/ksh, \
/usr/local/bin/tcsh, /usr/bin/rsh, \
/usr/local/bin/zsh
Cmnd_Alias SU = /usr/bin/su
Cmnd_Alias PAGERS = /usr/bin/more, /usr/bin/pg, /usr/bin/less
Here we override some of the compiled in default values. We
want sudo to log via syslog(3) using the auth facility in
all cases. We don't want to subject the full time staff to
the sudo lecture, user millert need not give a password, and
we don't want to reset the LOGNAME, USER or USERNAME
environment variables when running commands as root.
Additionally, on the machines in the SERVERS Host_Alias, we
keep an additional local log file and make sure we log the
year in each log line since the log entries will be kept
around for several years. Lastly, we disable shell escapes
for the commands in the PAGERS Cmnd_Alias (/usr/bin/more,
/usr/bin/pg and /usr/bin/less).
# Override built-in defaults
Defaults syslog=auth
Defaults>root !set_logname
Defaults:FULLTIMERS !lecture
Defaults:millert !authenticate
Defaults at SERVERS log_year, logfile=/var/log/sudo.log
Defaults!PAGERS noexec
The User specification is the part that actually determines
who may run what.
root ALL = (ALL) ALL
%wheel ALL = (ALL) ALL
We let root and any user in group wheel run any command on
any host as any user.
FULLTIMERS ALL = NOPASSWD: ALL
Full time sysadmins (millert, mikef, and dowdy) may run any
command on any host without authenticating themselves.
PARTTIMERS ALL = ALL
Part time sysadmins (bostley, jwfox, and crawl) may run any
command on any host but they must authenticate themselves
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first (since the entry lacks the NOPASSWD tag).
jack CSNETS = ALL
The user jack may run any command on the machines in the
CSNETS alias (the networks 128.138.243.0, 128.138.204.0, and
128.138.242.0). Of those networks, only 128.138.204.0 has
an explicit netmask (in CIDR notation) indicating it is a
class C network. For the other networks in CSNETS, the
local machine's netmask will be used during matching.
lisa CUNETS = ALL
The user lisa may run any command on any host in the CUNETS
alias (the class B network 128.138.0.0).
operator ALL = DUMPS, KILL, SHUTDOWN, HALT, REBOOT, PRINTING,\
sudoedit /etc/printcap, /usr/oper/bin/
The operator user may run commands limited to simple
maintenance. Here, those are commands related to backups,
killing processes, the printing system, shutting down the
system, and any commands in the directory /usr/oper/bin/.
joe ALL = /usr/bin/su operator
The user joe may only su(1) to operator.
pete HPPA = /usr/bin/passwd [A-Za-z]*, !/usr/bin/passwd root
The user pete is allowed to change anyone's password except
for root on the HPPA machines. Note that this assumes
passwd(1) does not take multiple usernames on the command
line.
bob SPARC = (OP) ALL : SGI = (OP) ALL
The user bob may run anything on the SPARC and SGI machines
as any user listed in the OP Runas_Alias (root and
operator).
jim +biglab = ALL
The user jim may run any command on machines in the biglab
netgroup. sudo knows that "biglab" is a netgroup due to the
'+' prefix.
+secretaries ALL = PRINTING, /usr/bin/adduser, /usr/bin/rmuser
Users in the secretaries netgroup need to help manage the
printers as well as add and remove users, so they are
allowed to run those commands on all machines.
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fred ALL = (DB) NOPASSWD: ALL
The user fred can run commands as any user in the DB
Runas_Alias (oracle or sybase) without giving a password.
john ALPHA = /usr/bin/su [!-]*, !/usr/bin/su *root*
On the ALPHA machines, user john may su to anyone except
root but he is not allowed to specify any options to the
su(1) command.
jen ALL, !SERVERS = ALL
The user jen may run any command on any machine except for
those in the SERVERS Host_Alias (master, mail, www and ns).
jill SERVERS = /usr/bin/, !SU, !SHELLS
For any machine in the SERVERS Host_Alias, jill may run any
commands in the directory /usr/bin/ except for those
commands belonging to the SU and SHELLS Cmnd_Aliases.
steve CSNETS = (operator) /usr/local/op_commands/
The user steve may run any command in the directory
/usr/local/op_commands/ but only as user operator.
matt valkyrie = KILL
On his personal workstation, valkyrie, matt needs to be able
to kill hung processes.
WEBMASTERS www = (www) ALL, (root) /usr/bin/su www
On the host www, any user in the WEBMASTERS User_Alias
(will, wendy, and wim), may run any command as user www
(which owns the web pages) or simply su(1) to www.
ALL CDROM = NOPASSWD: /sbin/umount /CDROM,\
/sbin/mount -o nosuid\,nodev /dev/cd0a /CDROM
Any user may mount or unmount a CD-ROM on the machines in
the CDROM Host_Alias (orion, perseus, hercules) without
entering a password. This is a bit tedious for users to
type, so it is a prime candidate for encapsulating in a
shell script.
SECURITY NOTES
It is generally not effective to "subtract" commands from
ALL using the '!' operator. A user can trivially circumvent
this by copying the desired command to a different name and
then executing that. For example:
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bill ALL = ALL, !SU, !SHELLS
Doesn't really prevent bill from running the commands listed
in SU or SHELLS since he can simply copy those commands to a
different name, or use a shell escape from an editor or
other program. Therefore, these kind of restrictions should
be considered advisory at best (and reinforced by policy).
PREVENTING SHELL ESCAPES
Once sudo executes a program, that program is free to do
whatever it pleases, including run other programs. This can
be a security issue since it is not uncommon for a program
to allow shell escapes, which lets a user bypass sudo's
access control and logging. Common programs that permit
shell escapes include shells (obviously), editors,
paginators, mail and terminal programs.
There are two basic approaches to this problem:
restrict Avoid giving users access to commands that allow
the user to run arbitrary commands. Many editors
have a restricted mode where shell escapes are
disabled, though sudoedit is a better solution to
running editors via sudo. Due to the large number
of programs that offer shell escapes, restricting
users to the set of programs that do not if often
unworkable.
noexec Many systems that support shared libraries have
the ability to override default library functions
by pointing an environment variable (usually
LD_PRELOAD) to an alternate shared library. On
such systems, sudo's noexec functionality can be
used to prevent a program run by sudo from
executing any other programs. Note, however, that
this applies only to native dynamically-linked
executables. Statically-linked executables and
foreign executables running under binary emulation
are not affected.
To tell whether or not sudo supports noexec, you
can run the following as root:
sudo -V | grep "dummy exec"
If the resulting output contains a line that
begins with:
File containing dummy exec functions:
then sudo may be able to replace the exec family
of functions in the standard library with its own
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MAINTENANCE COMMANDS SUDOERS(4)
that simply return an error. Unfortunately, there
is no foolproof way to know whether or not noexec
will work at compile-time. noexec should work on
SunOS, Solaris, *BSD, Linux, IRIX, Tru64 UNIX,
MacOS X, and HP-UX 11.x. It is known not to work
on AIX and UnixWare. noexec is expected to work
on most operating systems that support the
LD_PRELOAD environment variable. Check your
operating system's manual pages for the dynamic
linker (usually ld.so, ld.so.1, dyld, dld.sl, rld,
or loader) to see if LD_PRELOAD is supported.
To enable noexec for a command, use the NOEXEC tag
as documented in the User Specification section
above. Here is that example again:
aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
This allows user aaron to run /usr/bin/more and
/usr/bin/vi with noexec enabled. This will
prevent those two commands from executing other
commands (such as a shell). If you are unsure
whether or not your system is capable of
supporting noexec you can always just try it out
and see if it works.
Note that restricting shell escapes is not a panacea.
Programs running as root are still capable of many
potentially hazardous operations (such as changing or
overwriting files) that could lead to unintended privilege
escalation. In the specific case of an editor, a safer
approach is to give the user permission to run sudoedit.
SEE ALSO
rsh(1), su(1), fnmatch(3), sudo(1m), visudo(8)
CAVEATS
The sudoers file should always be edited by the visudo
command which locks the file and does grammatical checking.
It is imperative that sudoers be free of syntax errors since
sudo will not run with a syntactically incorrect sudoers
file.
When using netgroups of machines (as opposed to users), if
you store fully qualified hostnames in the netgroup (as is
usually the case), you either need to have the machine's
hostname be fully qualified as returned by the hostname
command or use the fqdn option in sudoers.
BUGS
If you feel you have found a bug in sudo, please submit a
bug report at http://www.sudo.ws/sudo/bugs/
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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.
DISCLAIMER
sudo 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 sudo or http://www.sudo.ws/sudo/license.html for
complete details.
ATTRIBUTES
See attributes(5) for descriptions of the following
attributes:
_____________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| Availability | SUNWsudor, SUNWsudou|
| Interface Stability | Uncommitted |
|___________________________________________|
NOTES
sudo does not create audit(2) records; for a Role Based
administration solution that performs auditing of all
actions, please refer to rbac(5).
Source for sudo is available on http://opensolaris.org.
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