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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 multiple matches, 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 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).
AAlliiaasseess
There are four kinds of aliases: User_Alias, Runas_Alias, Host_Alias
and Cmnd_Alias.
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
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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 uppercase 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 ::= '!'* user name |
'!'* '#'uid |
'!'* '%'group |
'!'* '+'netgroup |
'!'* '%:'nonunix_group |
'!'* User_Alias
A User_List is made up of one or more user names, 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.
A user name, group, netgroup or nonunix_group may be enclosed in double
quotes to avoid the need for escaping special characters. Alternately,
special characters may be specified in escaped hex mode, e.g. \x20 for
space.
The nonunix_group syntax depends on the underlying implementation. For
instance, the QAS AD backend supports the following formats:
+o Group in the same domain: "Group Name"
+o Group in any domain: "Group Name@FULLY.QUALIFIED.DOMAIN"
+o Group SID: "S-1-2-34-5678901234-5678901234-5678901234-567"
Note that quotes around group names are optional. Unquoted strings
must use a backslash (\) to escape spaces and the '@' symbol.
Runas_List ::= Runas_Member |
Runas_Member ',' Runas_List
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SUDOERS(4) MAINTENANCE COMMANDS SUDOERS(4)
Runas_Member ::= '!'* user name |
'!'* '#'uid |
'!'* '%'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 user names 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 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 ::= '!'* host name |
'!'* ip_addr |
'!'* network(/netmask)? |
'!'* '+'netgroup |
'!'* Host_Alias
A Host_List is made up of one or more host names, 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, ssuuddoo 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 host name may include
shell-style wildcards (see the Wildcards section below), but unless the
host name 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.
Note ssuuddoo only inspects actual network interfaces; this means that IP
address 127.0.0.1 (localhost) will never match. Also, the host name
"localhost" will only match if that is the actual host name, which is
usually only the case for non-networked systems.
Cmnd_List ::= Cmnd |
Cmnd ',' Cmnd_List
commandname ::= file name |
file name args |
file name '""'
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 file name which may
1.7.4 July 21, 2010 3
SUDOERS(4) MAINTENANCE COMMANDS SUDOERS(4)
include shell-style wildcards (see the Wildcards section below). A
simple file name 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 path name 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 ssuuddoo with the --ee option (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, 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 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 disable 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.
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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.
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? SELinux_Spec? Tag_Spec* Cmnd
Runas_Spec ::= '(' Runas_List? (':' Runas_List)? ')'
SELinux_Spec ::= ('ROLE=role' | 'TYPE=type')
Tag_Spec ::= ('NOPASSWD:' | 'PASSWD:' | 'NOEXEC:' | 'EXEC:' |
'SETENV:' | 'NOSETENV:' | 'LOG_INPUT:' | 'NOLOG_INPUT:' |
'LOG_OUTPUT:' | 'NOLOG_OUTPUT:')
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.
The basic structure of a user specification is `who = where (as_whom)
what'. Let's break that down into its constituent parts:
RRuunnaass__SSppeecc
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 ssuuddoo's --uu option. The second defines a list of
groups that can be specified via ssuuddoo's --gg 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 --gg
option may be specified. If the first Runas_List is empty but the
second 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 rroooott 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 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.,
$ sudo -u operator /bin/ls.
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SUDOERS(4) MAINTENANCE COMMANDS SUDOERS(4)
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.
We can extend this to allow ddggbb to run /bin/ls with either the user or
group set to ooppeerraattoorr:
dgb boulder = (operator : operator) /bin/ls, (root) /bin/kill, \
/usr/bin/lprm
In the following example, user ttccmm 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 ttccmm.
tcm boulder = (:dialer) /usr/bin/tip, /usr/bin/cu, \
/usr/local/bin/minicom
SSEELLiinnuuxx__SSppeecc
On systems with SELinux support, _s_u_d_o_e_r_s entries may optionally have an
SELinux role and/or type associated with a command. If a role or type
is specified with the command it will override any default values
specified in _s_u_d_o_e_r_s. A role or type specified on the command line,
however, will supercede the values in _s_u_d_o_e_r_s.
TTaagg__SSppeecc
A command may have zero or more tags associated with it. There are
eight possible tag values, NOPASSWD, PASSWD, NOEXEC, EXEC, SETENV,
NOSETENV, LOG_INPUT, NOLOG_INPUT, LOG_OUTPUT and NOLOG_OUTPUT. 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).
_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 rroooott on the machine rushmore 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
1.7.4 July 21, 2010 6
SUDOERS(4) MAINTENANCE COMMANDS SUDOERS(4)
the group specified by the _e_x_e_m_p_t___g_r_o_u_p 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.
_N_O_E_X_E_C _a_n_d _E_X_E_C
If ssuuddoo has been compiled with _n_o_e_x_e_c 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 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 NOEXEC works and whether or not it will work on your system.
_S_E_T_E_N_V _a_n_d _N_O_S_E_T_E_N_V
These tags override the value of the _s_e_t_e_n_v 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 _e_n_v___c_h_e_c_k, _e_n_v___d_e_l_e_t_e, or _e_n_v___k_e_e_p. As such,
only trusted users should be allowed to set variables in this manner.
If the command matched is AALLLL, the SETENV tag is implied for that
command; this default may be overridden by use of the NOSETENV tag.
_L_O_G___I_N_P_U_T _a_n_d _N_O_L_O_G___I_N_P_U_T
These tags override the value of the _l_o_g___i_n_p_u_t option on a per-command
basis. For more information, see the description of _l_o_g___i_n_p_u_t in the
"SUDOERS OPTIONS" section below.
_L_O_G___O_U_T_P_U_T _a_n_d _N_O_L_O_G___O_U_T_P_U_T
These tags override the value of the _l_o_g___o_u_t_p_u_t option on a per-command
basis. For more information, see the description of _l_o_g___o_u_t_p_u_t in the
"SUDOERS OPTIONS" section below.
WWiillddccaarrddss
ssuuddoo allows shell-style _w_i_l_d_c_a_r_d_s (aka meta or glob characters) to be
used in host names, path names and command line arguments in the
_s_u_d_o_e_r_s file. Wildcard matching is done via the PPOOSSIIXX _g_l_o_b(3) and
_f_n_m_a_t_c_h(3) routines. Note that these are _n_o_t regular expressions.
* Matches any set of zero or more characters.
? Matches any single character.
1.7.4 July 21, 2010 7
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[...] 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 "}".
POSIX character classes may also be used if your system's _g_l_o_b(3) and
_f_n_m_a_t_c_h(3) functions support them. However, because the ':' character
has special meaning in _s_u_d_o_e_r_s, it must be escaped. For example:
/bin/ls [[\:alpha\:]]*
Would match any file name beginning with a letter.
Note that a forward slash ('/') will nnoott be matched by wildcards used
in the path name. When matching the command line arguments, however, a
slash ddooeess get matched by wildcards. 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.
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 command is not allowed to be run
with aannyy arguments.
IInncclluuddiinngg ootthheerr ffiilleess ffrroomm wwiitthhiinn ssuuddooeerrss
It is possible to include other _s_u_d_o_e_r_s files from within the _s_u_d_o_e_r_s
file currently being parsed using the #include and #includedir
directives.
This can be used, for example, to keep a site-wide _s_u_d_o_e_r_s file in
addition to a local, per-machine file. For the sake of this example
the site-wide _s_u_d_o_e_r_s will be _/_e_t_c_/_s_u_d_o_e_r_s and the per-machine one will
be _/_e_t_c_/_s_u_d_o_e_r_s_._l_o_c_a_l. To include _/_e_t_c_/_s_u_d_o_e_r_s_._l_o_c_a_l from within
_/_e_t_c_/_s_u_d_o_e_r_s we would use the following line in _/_e_t_c_/_s_u_d_o_e_r_s:
#include /etc/sudoers.local
When ssuuddoo reaches this line it will suspend processing of the current
file (_/_e_t_c_/_s_u_d_o_e_r_s) and switch to _/_e_t_c_/_s_u_d_o_e_r_s_._l_o_c_a_l. Upon reaching
the end of _/_e_t_c_/_s_u_d_o_e_r_s_._l_o_c_a_l, the rest of _/_e_t_c_/_s_u_d_o_e_r_s 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.
The file name may include the %h escape, signifying the short form of
the host name. I.e., if the machine's host name is "xerxes", then
#include /etc/sudoers.%h
1.7.4 July 21, 2010 8
SUDOERS(4) MAINTENANCE COMMANDS SUDOERS(4)
will cause ssuuddoo to include the file _/_e_t_c_/_s_u_d_o_e_r_s_._x_e_r_x_e_s.
The #includedir directive can be used to create a _s_u_d_o_._d directory that
the system package manager can drop _s_u_d_o_e_r_s rules into as part of
package installation. For example, given:
#includedir /etc/sudoers.d
ssuuddoo will read each file in _/_e_t_c_/_s_u_d_o_e_r_s_._d, skipping file names that
end in ~ or contain a . character to avoid causing problems with
package manager or editor temporary/backup files. Files are parsed in
sorted lexical order. That is, _/_e_t_c_/_s_u_d_o_e_r_s_._d_/_0_1___f_i_r_s_t will be parsed
before _/_e_t_c_/_s_u_d_o_e_r_s_._d_/_1_0___s_e_c_o_n_d. Be aware that because the sorting is
lexical, not numeric, _/_e_t_c_/_s_u_d_o_e_r_s_._d_/_1___w_h_o_o_p_s would be loaded aafftteerr
_/_e_t_c_/_s_u_d_o_e_r_s_._d_/_1_0___s_e_c_o_n_d. Using a consistent number of leading zeroes
in the file names can be used to avoid such problems.
Note that unlike files included via #include, vviissuuddoo will not edit the
files in a #includedir directory unless one of them contains a syntax
error. It is still possible to run vviissuuddoo with the -f flag to edit the
files directly.
OOtthheerr ssppeecciiaall cchhaarraacctteerrss aanndd rreesseerrvveedd wwoorrddss
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 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 user name or host name): '@', '!', '=',
':', ',', '(', ')', '\'.
1.7.4 July 21, 2010 9
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SSUUDDOOEERRSS OOPPTTIIOONNSS
ssuuddoo'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.
BBoooolleeaann FFllaaggss:
always_set_home If enabled, 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 option is always implied. Note that HOME
is already set when the the _e_n_v___r_e_s_e_t option is
enabled, so _a_l_w_a_y_s___s_e_t___h_o_m_e is only effective for
configurations where _e_n_v___r_e_s_e_t is disabled. 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 may be overridden via
the PASSWD and NOPASSWD tags. This flag is _o_n by
default.
closefrom_override
If set, the user may use ssuuddoo's --CC option which
overrides the default starting point at which ssuuddoo
begins closing open file descriptors. This flag is _o_f_f
by default.
compress_io If set, and ssuuddoo is configured to log a command's input
or output, the I/O logs will be compressed using zzlliibb.
This flag is _o_n by default when ssuuddoo is compiled with
zzlliibb support.
env_editor If set, vviissuuddoo 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. vviissuuddoo will then only
use the EDITOR or VISUAL if they match a value
specified in editor. This flag is _o_f_f by default.
env_reset If set, ssuuddoo will reset the environment to only contain
the LOGNAME, MAIL, 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 ssuuddoo is run by root
with the _-_V option. If the _s_e_c_u_r_e___p_a_t_h option is set,
its value will be used for the PATH environment
variable. This flag is _o_n by default.
fast_glob Normally, ssuuddoo uses the _g_l_o_b(3) function to do shell-
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style globbing when matching path names. However,
since it accesses the file system, _g_l_o_b(3) can take a
long time to complete for some patterns, especially
when the pattern references a network file system that
is mounted on demand (automounted). The _f_a_s_t___g_l_o_b
option causes ssuuddoo to use the _f_n_m_a_t_c_h(3) function,
which does not access the file system to do its
matching. The disadvantage of _f_a_s_t___g_l_o_b is that it is
unable to match relative path names such as _._/_l_s or
_._._/_b_i_n_/_l_s. This has security implications when path
names that include globbing characters are used with
the negation operator, '!', as such rules can be
trivially bypassed. As such, this option should not be
used when _s_u_d_o_e_r_s contains rules that contain negated
path names which include globbing characters. This
flag is _o_f_f by default.
fqdn Set this flag if you want to put fully qualified host
names in the _s_u_d_o_e_r_s 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 _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 host name (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.
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.
ignore_local_sudoers
If set via LDAP, parsing of _/_e_t_c_/_s_u_d_o_e_r_s 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
_/_e_t_c_/_s_u_d_o_e_r_s. When this option is present,
_/_e_t_c_/_s_u_d_o_e_r_s does not even need to exist. Since this
option tells ssuuddoo 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.
insults If set, ssuuddoo will insult users when they enter an
incorrect password. This flag is _o_f_f by default.
log_host If set, the host name will be logged in the (non-
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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.
long_otp_prompt When validating with a One Time Password (OPT) scheme
such as 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.
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 running ssuuddoo
does not enter the correct password. This flag is _o_f_f
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.
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.
noexec If set, all commands run via ssuuddoo 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 "PREVENTING SHELL ESCAPES" section at the
end of this manual. This flag is _o_f_f by default.
path_info Normally, ssuuddoo 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, ssuuddoo will tell the user that they are
not allowed to run it, which can be confusing. This
flag is _o_n by default.
passprompt_override
The password prompt specified by _p_a_s_s_p_r_o_m_p_t will
normally only be used if the password prompt provided
by systems such as PAM matches the string "Password:".
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If _p_a_s_s_p_r_o_m_p_t___o_v_e_r_r_i_d_e is set, _p_a_s_s_p_r_o_m_p_t will always
be used. This flag is _o_f_f by default.
preserve_groups By default, ssuuddoo will initialize the group vector 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.
pwfeedback By default, ssuuddoo reads the password like most other
Unix programs, by turning off echo until the user hits
the return (or enter) key. Some users become confused
by this as it appears to them that ssuuddoo has hung at
this point. When _p_w_f_e_e_d_b_a_c_k is set, ssuuddoo will provide
visual feedback when the user presses a key. Note that
this does have a security impact as an onlooker may be
able to determine the length of the password being
entered. 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. When this flag is set, ssuuddoo can only be
run from a login session and not via other means such
as _c_r_o_n(1m) or cgi-bin scripts. This flag is _o_f_f by
default.
root_sudo If set, root is allowed to run ssuuddoo too. Disabling
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 from running ssuuddooeeddiitt.
Disabling _r_o_o_t___s_u_d_o provides no real additional
security; it exists purely for historical reasons.
This flag is _o_n by default.
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.
set_home If enabled and ssuuddoo is invoked with the --ss option 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
option imply --HH. Note that HOME is already set when
the the _e_n_v___r_e_s_e_t option is enabled, so _s_e_t___h_o_m_e is
only effective for configurations where _e_n_v___r_e_s_e_t is
disabled. This flag is _o_f_f by default.
set_logname Normally, ssuuddoo will set the LOGNAME, USER and USERNAME
1.7.4 July 21, 2010 13
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environment variables to the name of the target user
(usually root unless the --uu 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 _e_n_v___r_e_s_e_t option has not been
disabled, entries in the _e_n_v___k_e_e_p list will override
the value of _s_e_t___l_o_g_n_a_m_e. This flag is _o_n by default.
setenv Allow the user to disable the _e_n_v___r_e_s_e_t option from the
command line. Additionally, environment variables set
via the command line are not subject to the
restrictions imposed by _e_n_v___c_h_e_c_k, _e_n_v___d_e_l_e_t_e, or
_e_n_v___k_e_e_p. As such, only trusted users should be
allowed to set variables in this manner. 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 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 _o_f_f by default.
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. This option is only effective on systems
with either the _s_e_t_r_e_u_i_d_(_) or _s_e_t_r_e_s_u_i_d_(_) function.
This flag is _o_f_f by default.
targetpw If set, ssuuddoo will prompt for the password of the user
specified by the --uu option (defaults to root) instead
of the password of the invoking user. In addition, the
timestamp file name will include the target user's
name. Note that this flag precludes the use of a uid
not listed in the passwd database as an argument to the
--uu option. This flag is _o_f_f by default.
log_input If set, ssuuddoo will run the command in a _p_s_e_u_d_o _t_t_y and
log all user input. If the standard input is not
connected to the user's tty, due to I/O redirection or
because the command is part of a pipeline, that input
is also captured and stored in a separate log file.
Input is logged to the _/_v_a_r_/_l_o_g_/_s_u_d_o_-_i_o directory using
a unique session ID that is included in the normal ssuuddoo
log line, prefixed with _T_S_I_D_=.
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log_output If set, ssuuddoo will run the command in a _p_s_e_u_d_o _t_t_y and
log all output that is sent to the screen, similar to
the _s_c_r_i_p_t(1) command. If the standard output or
standard error is not connected to the user's tty, due
to I/O redirection or because the command is part of a
pipeline, that output is also captured and stored in
separate log files.
Output is logged to the _/_v_a_r_/_l_o_g_/_s_u_d_o_-_i_o directory
using a unique session ID that is included in the
normal ssuuddoo log line, prefixed with _T_S_I_D_=.
Output logs may be viewed with the _s_u_d_o_r_e_p_l_a_y(1m)
utility, which can also be used to list or search the
available logs.
tty_tickets If set, users must authenticate on a per-tty basis.
With this flag enabled, ssuuddoo will use a file named for
the tty the user is logged in on in the user's time
stamp directory. If disabled, the time stamp of the
directory is used instead. This flag is _o_n by default.
umask_override If set, ssuuddoo will set the umask as specified by _s_u_d_o_e_r_s
without modification. This makes it possible to
specify a more permissive umask in _s_u_d_o_e_r_s than the
user's own umask and matches historical behavior. If
_u_m_a_s_k___o_v_e_r_r_i_d_e is not set, ssuuddoo will set the umask to
be the union of the user's umask and what is specified
in _s_u_d_o_e_r_s. This flag is _o_f_f by default.
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.
use_pty If set, ssuuddoo will run the command in a pseudo-pty even
if no I/O logging is being gone. A malicious program
run under ssuuddoo could conceivably fork a background
process that retains to the user's terminal device
after the main program has finished executing. Use of
this option will make that impossible.
visiblepw By default, ssuuddoo will refuse to run if the user must
enter a password but it is not possible to disable echo
on the terminal. If the _v_i_s_i_b_l_e_p_w flag is set, ssuuddoo
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 _r_s_h(1) does
not allocate a tty. This flag is _o_f_f by default.
IInntteeggeerrss:
closefrom Before it executes a command, ssuuddoo will close all open
file descriptors other than standard input, standard
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output and standard error (ie: file descriptors 0-2).
The _c_l_o_s_e_f_r_o_m 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 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).
passwd_timeout Number of minutes before the ssuuddoo password prompt times
out, or 0 for no timeout. The timeout may include a
fractional component if minute granularity is
insufficient, for example 2.5. The default is 5.
timestamp_timeout
Number of minutes that can elapse before ssuuddoo will ask
for a passwd again. The timeout may include a
fractional component if minute granularity is
insufficient, for example 2.5. 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 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 ssuuddoo 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 _s_u_d_o_e_r_s.
SSttrriinnggss:
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 vviissuuddoo. vviissuuddoo 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 "vi".
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mailsub Subject of the mail sent to the _m_a_i_l_t_o user. The escape
%h will expand to the host name of the machine.
Default is *** SECURITY information for %h ***.
noexec_file Path to a shared library containing dummy versions 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 functionality 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.
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:
%H expanded to the local host name including the
domain name (on if the machine's host name is fully
qualified or the _f_q_d_n option is set)
%h expanded to the local host name without the domain
name
%p expanded to the user whose password is being asked
for (respects the _r_o_o_t_p_w, _t_a_r_g_e_t_p_w and _r_u_n_a_s_p_w
flags in _s_u_d_o_e_r_s)
%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:.
role The default SELinux role to use when constructing a new
security context to run the command. The default role
may be overridden on a per-command basis in _s_u_d_o_e_r_s or
via command line options. This option is only
available whe ssuuddoo is built with SELinux support.
runas_default The default user to run commands as if the --uu option 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_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.
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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 ssuuddoo stores its timestamp files.
The default is _/_v_a_r_/_a_d_m_/_s_u_d_o.
timestampowner The owner of the timestamp directory and the timestamps
stored therein. The default is root.
type The default SELinux type to use when constructing a new
security context to run the command. The default type
may be overridden on a per-command basis in _s_u_d_o_e_r_s or
via command line options. This option is only
available whe ssuuddoo is built with SELinux support.
SSttrriinnggss tthhaatt ccaann bbee uusseedd iinn aa bboooolleeaann ccoonntteexxtt:
askpass The _a_s_k_p_a_s_s 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 ssuuddoo is
executed from a graphical (as opposed to text-based)
application. The program specified by _a_s_k_p_a_s_s should
display the argument passed to it as the prompt and write
the user's password to the standard output. The value of
_a_s_k_p_a_s_s may be overridden by the SUDO_ASKPASS environment
variable.
env_file The _e_n_v___f_i_l_e 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 either
be of the form VARIABLE=value or export VARIABLE=value.
The value may optionally be surrounded by single or double
quotes. Variables in this file are subject to other ssuuddoo
environment settings such as _e_n_v___k_e_e_p and _e_n_v___c_h_e_c_k.
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 ssuuddoo.
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 ssuuddoo lecture that
will be used in place of the standard lecture if the named
file exists. By default, ssuuddoo uses a built-in lecture.
listpw This option controls when a password will be required when
a user runs ssuuddoo with the --ll option. 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.
always The user must always enter a password to use the --ll
option.
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 entering a password.
never The user need never enter a password to use the --ll
option.
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.
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. By default, ssuuddoo logs via syslog.
mailerflags Flags to use when invoking mailer. Defaults to --tt.
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 ssuuddoo interpreting the @ sign.
Defaults to the name of the user running ssuuddoo.
mailto Address to send warning and error mail to. The address
should be enclosed in double quotes (") to protect against
ssuuddoo interpreting the @ sign. Defaults to root.
secure_path Path used for every command run from ssuuddoo. If you don't
trust the people running ssuuddoo 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
_e_x_e_m_p_t___g_r_o_u_p option are not affected by _s_e_c_u_r_e___p_a_t_h. This
option is not set by default.
syslog Syslog facility if syslog is being used for logging (negate
1.7.4 July 21, 2010 19
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to disable syslog logging). Defaults to auth.
verifypw This option controls when a password will be required when
a user runs ssuuddoo with the --vv option. 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.
always The user must always enter a password to use the --vv
option.
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 entering a password.
never The user need never enter a password to use the --vv
option.
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.
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 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 ssuuddoo
is run by root with the _-_V option.
env_delete Environment variables to be removed from the user's
environment when the _e_n_v___r_e_s_e_t option is not in effect.
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 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 user's
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environment when the _e_n_v___r_e_s_e_t option is in effect.
This allows fine-grained control over the environment
ssuuddoo-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 ssuuddoo is run by root
with the _-_V option.
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, ddaaeemmoonn, 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.
FFIILLEESS
_/_e_t_c_/_s_u_d_o_e_r_s List of who can run what
_/_e_t_c_/_g_r_o_u_p Local groups file
_/_e_t_c_/_n_e_t_g_r_o_u_p List of network groups
_/_v_a_r_/_l_o_g_/_s_u_d_o_-_i_o I/O log files
EEXXAAMMPPLLEESS
Below are example _s_u_d_o_e_r_s entries. Admittedly, some of these are a bit
contrived. First, we allow a few environment variables to pass and
then define our _a_l_i_a_s_e_s:
# Run X applications through sudo; HOME is used to find the
# .Xauthority file. Note that other programs use HOME to find
# configuration files and this may lead to privilege escalation!
Defaults env_keep += "DISPLAY HOME"
# 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
Runas_Alias ADMINGRP = adm, oper
# 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
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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
Cmnd_Alias PAGERS = /usr/bin/more, /usr/bin/pg, /usr/bin/less
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, USER
or USERNAME 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.
Lastly, we disable shell escapes for the commands in the PAGERS
Cmnd_Alias (_/_u_s_r_/_b_i_n_/_m_o_r_e, _/_u_s_r_/_b_i_n_/_p_g and _/_u_s_r_/_b_i_n_/_l_e_s_s).
# 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
Defaults!PAGERS noexec
The _U_s_e_r _s_p_e_c_i_f_i_c_a_t_i_o_n is the part that actually determines 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 themselves first (since the entry
lacks the NOPASSWD tag).
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SUDOERS(4) MAINTENANCE COMMANDS SUDOERS(4)
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 maintenance.
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_/.
joe ALL = /usr/bin/su operator
The user jjooee may only _s_u(1) to operator.
pete HPPA = /usr/bin/passwd [A-Za-z]*, !/usr/bin/passwd root
%opers ALL = (: ADMINGRP) /usr/sbin/
Users in the ooppeerrss group may run commands in _/_u_s_r_/_s_b_i_n_/ as themselves
with any group in the _A_D_M_I_N_G_R_P Runas_Alias (the aaddmm and ooppeerr groups).
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 user names 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
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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 specify any options to the _s_u(1) command.
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 _/_u_s_r_/_b_i_n_/ 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
/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 circumvent 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 commands to a different name, or
use a shell escape from an editor or other program. Therefore, these
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SUDOERS(4) MAINTENANCE COMMANDS SUDOERS(4)
kind of restrictions should be considered advisory at best (and
reinforced by policy).
Furthermore, if the _f_a_s_t___g_l_o_b option is in use, it is not possible to
reliably negate commands where the path name includes globbing (aka
wildcard) characters. This is because the C library's _f_n_m_a_t_c_h(3)
function cannot resolve relative paths. While this is typically only
an inconvenience for rules that grant privileges, it can result in a
security issue for rules that subtract or revoke privileges.
For example, given the following _s_u_d_o_e_r_s entry:
john ALL = /usr/bin/passwd [a-zA-Z0-9]*, /usr/bin/chsh [a-zA-Z0-9]*,
/usr/bin/chfn [a-zA-Z0-9]*, !/usr/bin/* root
User jjoohhnn can still run /usr/bin/passwd root if _f_a_s_t___g_l_o_b is enabled by
changing to _/_u_s_r_/_b_i_n and running ./passwd root instead.
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 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 ssuuddooeeddiitt is a better
solution to running editors via ssuuddoo. 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, ssuuddoo's _n_o_e_x_e_c functionality
can be used to prevent a program run by ssuuddoo 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 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:
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then ssuuddoo may be able to replace the exec family of functions
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 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 _n_o_e_x_e_c 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 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 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 ssuuddooeeddiitt.
SSEEEE AALLSSOO
_r_s_h(1), _s_u(1), _f_n_m_a_t_c_h(3), _g_l_o_b(3), _s_u_d_o(1m), _v_i_s_u_d_o(8)
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 checking. It is imperative that
_s_u_d_o_e_r_s be free of syntax errors since ssuuddoo will not run with a
syntactically incorrect _s_u_d_o_e_r_s file.
When using netgroups of machines (as opposed to users), if you store
fully qualified host name in the netgroup (as is usually the case), you
either need to have the machine's host name 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
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.
1.7.4 July 21, 2010 26
SUDOERS(4) MAINTENANCE COMMANDS SUDOERS(4)
DDIISSCCLLAAIIMMEERR
ssuuddoo is provided ``AS IS'' and any express or implied warranties,
including, but not limited to, the implied warranties of
merchantability and fitness for a particular purpose are disclaimed.
See the LICENSE file distributed with ssuuddoo or
http://www.sudo.ws/sudo/license.html for complete details.
1.7.4 July 21, 2010 27