SUDOERS(4) MAINTENANCE COMMANDS SUDOERS(4)
NNAAMMEE
sudoers - list of which users may execute what
DDEESSCCRRIIPPTTIIOONN
The _s_u_d_o_e_r_s 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 conflicting values, the last
match is used (which is not necessarily the most specific
match).
The _s_u_d_o_e_r_s 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.
QQuuiicckk gguuiiddee ttoo EEBBNNFF
EBNF is a concise and exact way of describing the grammar
of a language. Each EBNF definition is made up of _p_r_o_d_u_c_
_t_i_o_n _r_u_l_e_s. E.g.,
symbol ::= definition | alternate1 | alternate2 ...
Each _p_r_o_d_u_c_t_i_o_n _r_u_l_e references others and thus makes up a
grammar for the language. EBNF also contains the follow
ing operators, which many readers will recognize from reg
ular expressions. Do not, however, confuse them with
"wildcard" characters, which have different meanings.
? Means that the preceding symbol (or group of sym
bols) is optional. That is, it may appear once or
not at all.
* Means that the preceding symbol (or group of sym
bols) may appear zero or more times.
+ Means that the preceding symbol (or group of sym
bols) 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).
AAlliiaasseess
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 _a_l_i_a_s definition is of the form
Alias_Type NAME = item1, item2, ...
where _A_l_i_a_s___T_y_p_e is one of User_Alias, Runas_Alias,
Host_Alias, or Cmnd_Alias. A NAME is a string of upper
case letters, numbers, and underscore characters ('_'). A
NAME mmuusstt 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 _a_l_i_a_s member
follow.
User_List ::= User |
User ',' User_List
User ::= '!'* username |
'!'* '%'group |
'!'* '+'netgroup |
'!'* User_Alias
A User_List is made up of one or more usernames, system
groups (prefixed with '%'), netgroups (prefixed with '+')
and other aliases. Each list item may be prefixed with
one 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_User |
Runas_User ',' Runas_List
Runas_User ::= '!'* username |
'!'* '#'uid |
'!'* '%'group |
'!'* +netgroup |
'!'* Runas_Alias
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A Runas_List is similar to a User_List except that it can
also contain uids (prefixed with '#') and 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 con
sidered to be distinct. If you wish to match all user
names 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 with a network number, the netmask of the host's
ethernet interface(s) will be used when matching. The
netmask may be specified either in dotted quad notation
(e.g. 255.255.255.0) or CIDR notation (number of bits,
e.g. 24). A hostname may include shell-style wildcards
(see the Wildcards section below), but unless the hostname
command on your machine returns the fully qualified host
name, you'll need to use the _f_q_d_n 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, direc
tories, and other aliases. A commandname is a fully qual
ified filename which may include shell-style wildcards
(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
wwiitthhoouutt command line arguments. A directory is a fully
qualified pathname ending in a '/'. When you specify a
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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 argu
ments: ',', ':', '=', '\'. The special command "sudoedit"
is used to permit a user to run ssuuddoo with the --ee flag (or
as ssuuddooeeddiitt). It may take command line arguments just as
a normal command does.
DDeeffaauullttss
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, or commands being run
as a specific user.
Default_Type ::= 'Defaults' |
'Defaults' '@' Host |
'Defaults' ':' User |
'Defaults' '>' RunasUser
Default_Entry ::= Default_Type Parameter_List
Parameter_List ::= Parameter |
Parameter ',' Parameter_List
Parameter ::= Parameter '=' Value |
Parameter '+=' Value |
Parameter '-=' Value |
'!'* Parameter
Parameters may be ffllaaggss, iinntteeggeerr values, ssttrriinnggss, or
lliissttss. 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 dis
able them. Values 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.
FFllaaggss:
long_otp_prompt
When validating with a One Time Password
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scheme (SS//KKeeyy or OOPPIIEE), 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 _o_f_f by default.
ignore_dot If set, ssuuddoo will ignore '.' or '' (current
dir) in the PATH environment variable; the
PATH itself is not modified. This flag is _o_f_f
by default. Currently, while it is possible
to set _i_g_n_o_r_e___d_o_t in _s_u_d_o_e_r_s, its value is not
used. This option should be considered read-
only (it will be fixed in a future version of
ssuuddoo).
mail_always Send mail to the _m_a_i_l_t_o user every time a
users runs ssuuddoo. This flag is _o_f_f by default.
mail_badpass
Send mail to the _m_a_i_l_t_o user if the user run
ning sudo does not enter the correct password.
This flag is _o_f_f by default.
mail_no_user
If set, mail will be sent to the _m_a_i_l_t_o user
if the invoking user is not in the _s_u_d_o_e_r_s
file. This flag is _o_n by default.
mail_no_host
If set, mail will be sent to the _m_a_i_l_t_o user
if the invoking user exists in the _s_u_d_o_e_r_s
file, but is not allowed to run commands on
the current host. This flag is _o_f_f by
default.
mail_no_perms
If set, mail will be sent to the _m_a_i_l_t_o user
if the invoking user is allowed to use ssuuddoo
but the command they are trying is not listed
in their _s_u_d_o_e_r_s file entry or is explicitly
denied. This flag is _o_f_f by default.
tty_tickets If set, users must authenticate on a per-tty
basis. Normally, ssuuddoo uses a directory in the
ticket dir with the same name as the user run
ning it. With this flag enabled, ssuuddoo will
use a file named for the tty the user is
logged in on in that directory. This flag is
_o_f_f by default.
authenticate
If set, users must authenticate themselves via
a password (or other means of authentication)
before they may run commands. This default
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may be overridden via the PASSWD and NOPASSWD
tags. This flag is _o_n by default.
root_sudo If set, root is allowed to run ssuuddoo too. Dis
abling this prevents users from "chaining"
ssuuddoo commands to get a root shell by doing
something like "sudo sudo /bin/sh". Note,
however, that turning off _r_o_o_t___s_u_d_o will also
prevent root and from running ssuuddooeeddiitt. Dis
abling _r_o_o_t___s_u_d_o provides no real additional
security; it exists purely for historical rea
sons. This flag is _o_n by default.
log_host If set, the hostname will be logged in the
(non-syslog) ssuuddoo log file. This flag is _o_f_f
by default.
log_year If set, the four-digit year will be logged in
the (non-syslog) ssuuddoo log file. This flag is
_o_f_f by default.
shell_noargs
If set and ssuuddoo is invoked with no arguments
it acts as if the --ss flag 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 _o_f_f by default.
set_home If set and ssuuddoo is invoked with the --ss flag
the HOME environment variable will be set to
the home directory of the target user (which
is root unless the --uu option is used). This
effectively makes the --ss flag imply --HH. This
flag is _o_f_f by default.
always_set_home
If set, ssuuddoo will set the HOME environment
variable to the home directory of the target
user (which is root unless the --uu option is
used). This effectively means that the --HH
flag is always implied. This flag is _o_f_f by
default.
path_info Normally, ssuuddoo will tell the user when a com
mand could not be found in their PATH environ
ment 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 disadvan
tage is that if the executable is simply not
in the user's PATH, ssuuddoo will tell the user
that they are not allowed to run it, which can
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be confusing. This flag is _o_f_f by default.
preserve_groups
By default ssuuddoo will initialize the group vec
tor to the list of groups the target user is
in. When _p_r_e_s_e_r_v_e___g_r_o_u_p_s 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 _o_f_f by default.
fqdn Set this flag if you want to put fully quali
fied hostnames in the _s_u_d_o_e_r_s file. I.e.,
instead of myhost you would use myhost.mydo
main.edu. You may still use the short form if
you wish (and even mix the two). Beware that
turning on _f_q_d_n requires ssuuddoo to make DNS
lookups which may make ssuuddoo 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 _f_q_d_n. This flag is _o_f_f by default.
insults If set, ssuuddoo will insult users when they enter
an incorrect password. This flag is _o_f_f by
default.
requiretty If set, ssuuddoo will only run when the user is
logged in to a real tty. This will disallow
things like "rsh somehost sudo ls" since
_r_s_h(1) does not allocate a tty. Because it is
not possible to turn off echo when there is no
tty present, some sites may with to set this
flag to prevent a user from entering a visible
password. This flag is _o_f_f by default.
env_editor If set, vviissuuddoo will use the value of the EDI
TOR 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. vviissuuddoo will then only
use the EDITOR or VISUAL if they match a value
specified in editor. This flag is off by
default.
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rootpw If set, ssuuddoo will prompt for the root password
instead of the password of the invoking user.
This flag is _o_f_f by default.
runaspw If set, ssuuddoo will prompt for the password of
the user defined by the _r_u_n_a_s___d_e_f_a_u_l_t option
(defaults to root) instead of the password of
the invoking user. This flag is _o_f_f by
default.
targetpw If set, ssuuddoo will prompt for the password of
the user specified by the --uu flag (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 --uu flag. This flag is _o_f_f by
default.
set_logname Normally, ssuuddoo will set the LOGNAME and USER
environment variables to the name of the tar
get user (usually root unless the --uu flag is
given). However, since some programs (includ
ing the RCS revision control system) use LOG
NAME 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.
stay_setuid Normally, when ssuuddoo 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 ssuuddoo act as a setuid wrapper. This
can be useful on systems that disable some
potentially dangerous functionality when a
program is run setuid. Note, however, that
this means that sudo will run with the real
uid of the invoking user which may allow that
user to kill ssuuddoo before it can log a failure,
depending on how your OS defines the interac
tion between signals and setuid processes.
env_reset If set, ssuuddoo will reset the environment to
only contain the following variables: HOME,
LOGNAME, PATH, SHELL, TERM, and USER (in addi
tion to the SUDO_* variables). Of these, only
TERM is copied unaltered from the old environ
ment. The other variables are set to default
values (possibly modified by the value of the
_s_e_t___l_o_g_n_a_m_e option). If ssuuddoo was compiled
with the SECURE_PATH option, its value will be
used for the PATH environment variable. Other
variables may be preserved with the _e_n_v___k_e_e_p
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option.
use_loginclass
If set, ssuuddoo will apply the defaults specified
for the target user's login class if one
exists. Only available if ssuuddoo is configured
with the --with-logincap option. This flag is
_o_f_f 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 _N_O_E_X_E_C _a_n_d _E_X_E_C below as well as the "PRE
VENTING SHELL ESCAPES" section at the end of
this manual. This flag is _o_f_f by default.
ignore_local_sudoers
If set via LDAP, parsing of @sysconfdir@/sudo
ers will be skipped. This is intended for an
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
@sysconfdir@/sudoers. When this option is
present, @sysconfdir@/sudoers does not even
need to exist. Since this options 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 _o_f_f by default.
IInntteeggeerrss:
passwd_tries
The number of tries a user gets to enter
his/her password before ssuuddoo logs the failure
and exits. The default is 3.
IInntteeggeerrss tthhaatt ccaann bbee uusseedd iinn aa bboooolleeaann ccoonntteexxtt:
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).
timestamp_timeout
Number of minutes that can elapse before ssuuddoo
will ask for a passwd again. The default is
5. Set this to 0 to always prompt for a pass
word. If set to a value less than 0 the
user's timestamp will never expire. This can
be used to allow users to create or delete
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their own timestamps via sudo -v and sudo -k
respectively.
passwd_timeout
Number of minutes before the ssuuddoo password
prompt times out. The default is 5, set this
to 0 for no password timeout.
umask Umask to use when running the command. Negate
this option or set it to 0777 to preserve the
user's umask. The default is 0022.
SSttrriinnggss:
mailsub Subject of the mail sent to the _m_a_i_l_t_o user.
The escape %h will expand to the hostname of
the machine. Default is *** SECURITY informa
tion for %h ***.
badpass_message
Message that is displayed if a user enters an
incorrect password. The default is Sorry, try
again. unless insults are enabled.
timestampdir
The directory in which ssuuddoo stores its times
tamp files. The default is _/_v_a_r_/_r_u_n_/_s_u_d_o.
timestampowner
The owner of the timestamp directory and the
timestamps stored therein. The default is
root.
passprompt The default prompt to use when asking for a
password; can be overridden via the --pp option
or the SUDO_PROMPT environment variable. The
following percent (`%') escapes are supported:
%u expanded to the invoking user's login
name
%U expanded to the login name of the user
the command will be run as (defaults
to root)
%h expanded to the local hostname without
the domain name
%H expanded to the local hostname includ
ing the domain name (on if the
machine's hostname is fully qualified
or the _f_q_d_n option is set)
%% two consecutive % characters are
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collaped into a single % character
The default value is Password:.
runas_default
The default user to run commands as if the --uu
flag is not specified on the command line.
This defaults to root. Note that if
_r_u_n_a_s___d_e_f_a_u_l_t is set it mmuusstt occur before any
Runas_Alias specifications.
syslog_goodpri
Syslog priority to use when user authenticates
successfully. Defaults to notice.
syslog_badpri
Syslog priority to use when user authenticates
unsuccessfully. Defaults to alert.
editor A colon (':') separated list of editors
allowed to be used with vviissuuddoo. vviissuuddoo will
choose the editor that matches the user's USER
environment variable if possible, or the first
editor in the list that exists and is exe
cutable. The default is the path to vi on
your system.
noexec_file Path to a shared library containing dummy ver
sions of the _e_x_e_c_v_(_), _e_x_e_c_v_e_(_) and _f_e_x_e_c_v_e_(_)
library functions that just return an error.
This is used to implement the _n_o_e_x_e_c function
ality on systems that support LD_PRELOAD or
its equivalent. Defaults to
_/_u_s_r_/_l_o_c_a_l_/_l_i_b_e_x_e_c_/_s_u_d_o___n_o_e_x_e_c_._s_o.
SSttrriinnggss tthhaatt ccaann bbee uusseedd iinn aa bboooolleeaann ccoonntteexxtt:
lecture This option controls when a short lecture will
be printed along with the password prompt. It
has the following possible values:
never Never lecture the user.
once Only lecture the user the first time
they run ssuuddoo.
always Always lecture the user.
If no value is specified, a value of _o_n_c_e is
implied. Negating the option results in a
value of _n_e_v_e_r being used. The default value
is _o_n_c_e.
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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.
logfile Path to the ssuuddoo log file (not the syslog log
file). Setting a path turns on logging to a
file; negating this option turns it off.
syslog Syslog facility if syslog is being used for
logging (negate to disable syslog logging).
Defaults to local2.
mailerpath Path to mail program used to send warning
mail. Defaults to the path to sendmail found
at configure time.
mailerflags Flags to use when invoking mailer. Defaults to
--tt.
mailto Address to send warning and error mail to.
The address should be enclosed in double
quotes (") to protect against sudo interpret
ing the @ sign. Defaults to root.
exempt_group
Users in this group are exempt from password
and PATH requirements. This is not set by
default.
verifypw This option controls when a password will be
required when a user runs ssuuddoo with the --vv
flag. It has the following possible values:
all All the user's _s_u_d_o_e_r_s entries for the
current host must have the NOPASSWD
flag set to avoid entering a password.
any At least one of the user's _s_u_d_o_e_r_s
entries for the current host must have
the NOPASSWD flag set to avoid enter
ing a password.
never The user need never enter a password
to use the --vv flag.
always The user must always enter a password
to use the --vv flag.
If no value is specified, a value of _a_l_l is
implied. Negating the option results in a
value of _n_e_v_e_r being used. The default value
is _a_l_l.
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listpw This option controls when a password will be
required when a user runs ssuuddoo with the --ll
flag. It has the following possible values:
all All the user's _s_u_d_o_e_r_s entries for the
current host must have the NOPASSWD
flag set to avoid entering a password.
any At least one of the user's _s_u_d_o_e_r_s
entries for the current host must have
the NOPASSWD flag set to avoid enter
ing a password.
never The user need never enter a password
to use the --ll flag.
always The user must always enter a password
to use the --ll flag.
If no value is specified, a value of _a_n_y is
implied. Negating the option results in a
value of _n_e_v_e_r being used. The default value
is _a_n_y.
LLiissttss tthhaatt ccaann bbee uusseedd iinn aa bboooolleeaann ccoonntteexxtt:
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 vulnera
bilities in poorly-written programs. The
argument may be a double-quoted, space-sepa
rated list or a single value without dou
ble-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 check
is printed when ssuuddoo 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 sin
gle value without double-quotes. The list can
be replaced, added to, deleted from, or dis
abled by using the =, +=, -=, and ! operators
respectively. The default list of environment
variables to remove is printed when ssuuddoo 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 ssuuddoo).
env_keep Environment variables to be preserved in the
1.6.8p9 June, 20 2005 13
SUDOERS(4) MAINTENANCE COMMANDS SUDOERS(4)
user's environment when the _e_n_v___r_e_s_e_t option
is in effect. This allows fine-grained con
trol over the environment ssuuddoo-spawned pro
cesses will receive. The argument may be a
double-quoted, space-separated list or a sin
gle value without double-quotes. The list can
be replaced, added to, deleted from, or dis
abled by using the =, +=, -=, and ! operators
respectively. This list has no default mem
bers.
When logging via _s_y_s_l_o_g(3), ssuuddoo accepts the following
values for the syslog facility (the value of the ssyysslloogg
Parameter): aauutthhpprriivv (if your OS supports it), aauutthh, ddaaee
mmoonn, uusseerr, llooccaall00, llooccaall11, llooccaall22, llooccaall33, llooccaall44, llooccaall55,
llooccaall66, and llooccaall77. The following syslog priorities are
supported: aalleerrtt, ccrriitt, ddeebbuugg, eemmeerrgg, eerrrr, iinnffoo, nnoottiiccee,
and wwaarrnniinngg.
UUsseerr SSppeecciiffiiccaattiioonn
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 ')'
Tag_Spec ::= ('NOPASSWD:' | 'PASSWD:' | 'NOEXEC:' | 'EXEC:')
A uusseerr ssppeecciiffiiccaattiioonn determines which commands a user may
run (and as what user) on specified hosts. By default,
commands are run as rroooott, but this can be changed on a
per-command basis.
Let's break that down into its constituent parts:
RRuunnaass__SSppeecc
A Runas_Spec is simply a Runas_List (as defined above)
enclosed in a set of parentheses. If you do not specify a
Runas_Spec in the user specification, a default Runas_Spec
of rroooott will be used. A Runas_Spec sets the default for
commands that follow it. What this means is that for the
entry:
dgb boulder = (operator) /bin/ls, /bin/kill, /usr/bin/lprm
The user ddggbb may run _/_b_i_n_/_l_s, _/_b_i_n_/_k_i_l_l, and _/_u_s_r_/_b_i_n_/_l_p_r_m
-- but only as ooppeerraattoorr. E.g.,
1.6.8p9 June, 20 2005 14
SUDOERS(4) MAINTENANCE COMMANDS SUDOERS(4)
$ 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 ddggbb is now allowed to run _/_b_i_n_/_l_s as ooppeerraattoorr,
but _/_b_i_n_/_k_i_l_l and _/_u_s_r_/_b_i_n_/_l_p_r_m as rroooott.
TTaagg__SSppeecc
A command may have zero or more tags associated with it.
There are four possible tag values, NOPASSWD, PASSWD,
NOEXEC, EXEC. 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 (ie: PASSWD overrides
NOPASSWD and EXEC overrides NOEXEC).
_N_O_P_A_S_S_W_D _a_n_d _P_A_S_S_W_D
By default, ssuuddoo 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 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 rraayy to run _/_b_i_n_/_k_i_l_l, _/_b_i_n_/_l_s, and
_/_u_s_r_/_b_i_n_/_l_p_r_m as root on the machine rushmore as rroooott
without authenticating himself. If we only want rraayy to be
able to run _/_b_i_n_/_k_i_l_l 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 per
tain to the current host. This behavior may be overridden
via the verifypw and listpw options.
_N_O_E_X_E_C _a_n_d _E_X_E_C
If sudo has been compiled with _n_o_e_x_e_c support and the
underlying operating system support it, the NOEXEC tag can
be used to prevent a dynamically-linked executable from
1.6.8p9 June, 20 2005 15
SUDOERS(4) MAINTENANCE COMMANDS SUDOERS(4)
running further commands itself.
In the following example, user aaaarroonn may run _/_u_s_r_/_b_i_n_/_m_o_r_e
and _/_u_s_r_/_b_i_n_/_v_i 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 _n_o_e_x_e_c works and whether or not it will
work on your system.
WWiillddccaarrddss
ssuuddoo allows shell-style _w_i_l_d_c_a_r_d_s (aka meta or glob char
acters) to be used in pathnames as well as command line
arguments in the _s_u_d_o_e_r_s file. Wildcard matching is done
via the PPOOSSIIXX _f_n_m_a_t_c_h(3) routine. Note that these are _n_o_t
regular expressions.
* Matches any set of zero or more characters.
? Matches any single character.
[...] Matches any character in the specified range.
[!...] Matches any character nnoott in the specified range.
\x For any character "x", evaluates to "x". This is
used to escape special characters such as: "*",
"?", "[", and "}".
Note that a forward slash ('/') will nnoott be matched by
wildcards used in the pathname. When matching the command
line arguments, however, a slash ddooeess get matched by wild
cards. This is to make a path like:
/usr/bin/*
match _/_u_s_r_/_b_i_n_/_w_h_o but not _/_u_s_r_/_b_i_n_/_X_1_1_/_x_t_e_r_m.
WARNING: a pathname with wildcards will nnoott match a user
command that consists of a relative path. In other words,
given the following _s_u_d_o_e_r_s entry:
billy workstation = /usr/bin/*
user billy will be able to run any command in /usr/bin as
root, such as _/_u_s_r_/_b_i_n_/_w. The following two command will
be allowed (the first assumes that _/_u_s_r_/_b_i_n is in the
user's path):
$ sudo w
$ sudo /usr/bin/w
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SUDOERS(4) MAINTENANCE COMMANDS SUDOERS(4)
However, this will not:
$ cd /usr/bin
$ sudo ./w
For this reason you should only ggrraanntt access to commands
using wildcards and never rreessttrriicctt access using them.
This limitation will be removed in a future version of
ssuuddoo.
EExxcceeppttiioonnss ttoo wwiillddccaarrdd rruulleess
The following exceptions apply to the above rules:
"" If the empty string "" is the only command line
argument in the _s_u_d_o_e_r_s entry it means that com
mand is not allowed to be run with aannyy arguments.
OOtthheerr ssppeecciiaall cchhaarraacctteerrss aanndd rreesseerrvveedd wwoorrddss
The pound sign ('#') is used to indicate a comment (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 AALLLL is a built-in _a_l_i_a_s 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
_a_l_i_a_s called AALLLL as the built-in alias will be used in
preference to your own. Please note that using AALLLL can be
dangerous since in a command context, it allows the user
to run aannyy command on the system.
An exclamation point ('!') can be used as a logical _n_o_t
operator both in an _a_l_i_a_s 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 _U_s_e_r _S_p_e_c_i_f_i_c_a_t_i_o_n ('=', ':',
'(', ')') is optional.
The following characters must be escaped with a backslash
('\') when used as part of a word (e.g. a username or
hostname): '@', '!', '=', ':', ',', '(', ')', '\'.
1.6.8p9 June, 20 2005 17
SUDOERS(4) MAINTENANCE COMMANDS SUDOERS(4)
FFIILLEESS
/etc/sudoers List of who can run what
/etc/group Local groups file
/etc/netgroup List of network groups
EEXXAAMMPPLLEESS
Since the _s_u_d_o_e_r_s file is parsed in a single pass, order
is important. In general, you should structure _s_u_d_o_e_r_s
such that the Host_Alias, User_Alias, and Cmnd_Alias spec
ifications come first, followed by any Default_Entry
lines, and finally the Runas_Alias and user specifica
tions. The basic rule of thumb is you cannot reference an
Alias that has not already been defined.
Below are example _s_u_d_o_e_r_s entries. Admittedly, some of
these are a bit contrived. First, we define our _a_l_i_a_s_e_s:
# 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
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
Here we override some of the compiled in default values.
We want ssuuddoo to log via _s_y_s_l_o_g(3) using the _a_u_t_h facility
in all cases. We don't want to subject the full time
staff to the ssuuddoo lecture, user mmiilllleerrtt need not give a
password, and we don't want to reset the LOGNAME or USER
1.6.8p9 June, 20 2005 18
SUDOERS(4) MAINTENANCE COMMANDS SUDOERS(4)
environment variables when running commands as root.
Additionally, on the machines in the _S_E_R_V_E_R_S 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.
# Override built-in defaults
Defaults syslog=auth
Defaults>root !set_logname
Defaults:FULLTIMERS !lecture
Defaults:millert !authenticate
Defaults@SERVERS log_year, logfile=/var/log/sudo.log
The _U_s_e_r _s_p_e_c_i_f_i_c_a_t_i_o_n is the part that actually deter
mines who may run what.
root ALL = (ALL) ALL
%wheel ALL = (ALL) ALL
We let rroooott and any user in group wwhheeeell run any command on
any host as any user.
FULLTIMERS ALL = NOPASSWD: ALL
Full time sysadmins (mmiilllleerrtt, mmiikkeeff, and ddoowwddyy) may run
any command on any host without authenticating themselves.
PARTTIMERS ALL = ALL
Part time sysadmins (bboossttlleeyy, jjwwffooxx, and ccrraawwll) may run
any command on any host but they must authenticate them
selves first (since the entry lacks the NOPASSWD tag).
jack CSNETS = ALL
The user jjaacckk may run any command on the machines in the
_C_S_N_E_T_S 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 _C_S_N_E_T_S,
the local machine's netmask will be used during matching.
lisa CUNETS = ALL
The user lliissaa may run any command on any host in the
_C_U_N_E_T_S alias (the class B network 128.138.0.0).
operator ALL = DUMPS, KILL, SHUTDOWN, HALT, REBOOT, PRINTING,\
sudoedit /etc/printcap, /usr/oper/bin/
The ooppeerraattoorr user may run commands limited to simple main
tenance. Here, those are commands related to backups,
killing processes, the printing system, shutting down the
system, and any commands in the directory _/_u_s_r_/_o_p_e_r_/_b_i_n_/.
1.6.8p9 June, 20 2005 19
SUDOERS(4) MAINTENANCE COMMANDS SUDOERS(4)
joe ALL = /usr/bin/su operator
The user jjooee may only _s_u(1) to operator.
pete HPPA = /usr/bin/passwd [A-z]*, !/usr/bin/passwd root
The user ppeettee is allowed to change anyone's password
except for root on the _H_P_P_A machines. Note that this
assumes _p_a_s_s_w_d(1) does not take multiple usernames on the
command line.
bob SPARC = (OP) ALL : SGI = (OP) ALL
The user bboobb may run anything on the _S_P_A_R_C and _S_G_I
machines as any user listed in the _O_P Runas_Alias (rroooott
and ooppeerraattoorr).
jim +biglab = ALL
The user jjiimm may run any command on machines in the _b_i_g_l_a_b
netgroup. SSuuddoo knows that "biglab" is a netgroup due to
the '+' prefix.
+secretaries ALL = PRINTING, /usr/bin/adduser, /usr/bin/rmuser
Users in the sseeccrreettaarriieess 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.
fred ALL = (DB) NOPASSWD: ALL
The user ffrreedd can run commands as any user in the _D_B
Runas_Alias (oorraaccllee or ssyybbaassee) without giving a password.
john ALPHA = /usr/bin/su [!-]*, !/usr/bin/su *root*
On the _A_L_P_H_A machines, user jjoohhnn may su to anyone except
root but he is not allowed to give _s_u(1) any flags.
jen ALL, !SERVERS = ALL
The user jjeenn may run any command on any machine except for
those in the _S_E_R_V_E_R_S Host_Alias (master, mail, www and
ns).
jill SERVERS = /usr/bin/, !SU, !SHELLS
For any machine in the _S_E_R_V_E_R_S Host_Alias, jjiillll may run
any commands in the directory /usr/bin/ except for those
commands belonging to the _S_U and _S_H_E_L_L_S Cmnd_Aliases.
steve CSNETS = (operator) /usr/local/op_commands/
The user sstteevvee may run any command in the directory
1.6.8p9 June, 20 2005 20
SUDOERS(4) MAINTENANCE COMMANDS SUDOERS(4)
/usr/local/op_commands/ but only as user operator.
matt valkyrie = KILL
On his personal workstation, valkyrie, mmaatttt 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 _W_E_B_M_A_S_T_E_R_S User_Alias
(will, wendy, and wim), may run any command as user www
(which owns the web pages) or simply _s_u(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.
SSEECCUURRIITTYY NNOOTTEESS
It is generally not effective to "subtract" commands from
ALL using the '!' operator. A user can trivially circum
vent this by copying the desired command to a different
name and then executing that. For example:
bill ALL = ALL, !SU, !SHELLS
Doesn't really prevent bbiillll from running the commands
listed in _S_U or _S_H_E_L_L_S since he can simply copy those com
mands 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).
PPRREEVVEENNTTIINNGG SSHHEELLLL EESSCCAAPPEESS
Once ssuuddoo 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
ssuuddoo's restrictions. Common programs that permit shell
escapes include shells (obviously), editors, paginators,
mail and terminal programs.
Many systems that support shared libraries have the abil
ity to override default library functions by pointing an
environment variable (usually LD_PRELOAD) to an alternate
shared library. On such systems, ssuuddoo's _n_o_e_x_e_c function
ality 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
1.6.8p9 June, 20 2005 21
SUDOERS(4) MAINTENANCE COMMANDS SUDOERS(4)
running under binary emulation are not affected.
To tell whether or not ssuuddoo supports _n_o_e_x_e_c, 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 ssuuddoo may be able to replace the exec family of func
tions in the standard library with its own that simply
return an error. Unfortunately, there is no foolproof way
to know whether or not _n_o_e_x_e_c will work at compile-time.
_N_o_e_x_e_c should work on SunOS, Solaris, *BSD, Linux, IRIX,
Tru64 UNIX, MacOS X, and HP-UX 11.x. It is known nnoott to
work on AIX and UnixWare. _N_o_e_x_e_c is expected to work on
most operating systems that support the LD_PRELOAD envi
ronment 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 sup
ported.
To enable _n_o_e_x_e_c for a command, use the NOEXEC tag as doc
umented in the User Specification section above. Here is
that example again:
aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
This allows user aaaarroonn to run _/_u_s_r_/_b_i_n_/_m_o_r_e and
_/_u_s_r_/_b_i_n_/_v_i with _n_o_e_x_e_c 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 _n_o_e_x_e_c you can always just try it
out and see if it works.
Note that disabling shell escapes is not a panacea. Pro
grams running as root are still capable of many poten
tially hazardous operations (such as changing or overwrit
ing files) that could lead to unintended privilege escala
tion. In the specific case of an editor, a safer approach
is to give the user permission to run ssuuddooeeddiitt.
SSEEEE AALLSSOO
_r_s_h(1), _s_u(1), _f_n_m_a_t_c_h(3), sudo(1m), visudo(1m)
CCAAVVEEAATTSS
The _s_u_d_o_e_r_s file should aallwwaayyss be edited by the vviissuuddoo
command which locks the file and does grammatical check
ing. It is imperative that _s_u_d_o_e_r_s be free of syntax
errors since ssuuddoo will not run with a syntactically incor
rect _s_u_d_o_e_r_s file.
1.6.8p9 June, 20 2005 22
SUDOERS(4) MAINTENANCE COMMANDS SUDOERS(4)
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 _f_q_d_n option in _s_u_d_o_e_r_s.
BBUUGGSS
If you feel you have found a bug in ssuuddoo, please submit a
bug report at http://www.sudo.ws/sudo/bugs/
SSUUPPPPOORRTT
Commercial support is available for ssuuddoo, see
http://www.sudo.ws/sudo/support.html for details.
Limited free support is available via the sudo-users mail
ing list, see http://www.sudo.ws/mail
man/listinfo/sudo-users to subscribe or search the
archives.
DDIISSCCLLAAIIMMEERR
SSuuddoo is provided ``AS IS'' and any express or implied war
ranties, including, but not limited to, the implied war
ranties of merchantability and fitness for a particular
purpose are disclaimed. See the LICENSE file distributed
with ssuuddoo or http://www.sudo.ws/sudo/license.html for com
plete details.
1.6.8p9 June, 20 2005 23