SUDOERS(4) File Formats Manual SUDOERS(4)
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ssuuddooeerrss - default sudo security policy plugin
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The ssuuddooeerrss policy plugin determines a user's ssuuddoo privileges. It is the
default ssuuddoo policy plugin. The policy is driven by the /etc/sudoers
file or, optionally in LDAP. The policy format is described in detail in
the SUDOERS FILE FORMAT section. For information on storing ssuuddooeerrss
policy information in LDAP, please see sudoers.ldap(4).
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ssuuddoo consults the sudo.conf(4) file to determine which policy and and I/O
logging plugins to load. If no sudo.conf(4) file is present, or if it
contains no Plugin lines, ssuuddooeerrss will be used for policy decisions and
I/O logging. To explicitly configure sudo.conf(4) to use the ssuuddooeerrss
plugin, the following configuration can be used.
Plugin sudoers_policy sudoers.so
Plugin sudoers_io sudoers.so
Starting with ssuuddoo 1.8.5, it is possible to specify optional arguments to
the ssuuddooeerrss plugin in the sudo.conf(4) file. These arguments, if
present, should be listed after the path to the plugin (i.e. after
sudoers.so). Multiple arguments may be specified, separated by white
space. For example:
Plugin sudoers_policy sudoers.so sudoers_mode=0400
The following plugin arguments are supported:
ldap_conf=pathname
The ldap_conf argument can be used to override the default path
to the ldap.conf file.
ldap_secret=pathname
The ldap_secret argument can be used to override the default
path to the ldap.secret file.
sudoers_file=pathname
The sudoers_file argument can be used to override the default
path to the sudoers file.
sudoers_uid=uid
The sudoers_uid argument can be used to override the default
owner of the sudoers file. It should be specified as a numeric
user ID.
sudoers_gid=gid
The sudoers_gid argument can be used to override the default
group of the sudoers file. It must be specified as a numeric
group ID (not a group name).
sudoers_mode=mode
The sudoers_mode argument can be used to override the default
file mode for the sudoers file. It should be specified as an
octal value.
For more information on configuring sudo.conf(4), please refer to its
manual.
UUsseerr AAuutthheennttiiccaattiioonn
The ssuuddooeerrss security policy requires that most users authenticate
themselves before they can use ssuuddoo. A password is not required if the
invoking user is root, if the target user is the same as the invoking
user, or if the policy has disabled authentication for the user or
command. Unlike su(1), when ssuuddooeerrss requires authentication, it
validates the invoking user's credentials, not the target user's (or
root's) credentials. This can be changed via the rootpw, targetpw and
runaspw flags, described later.
If a user who is not listed in the policy tries to run a command via
ssuuddoo, mail is sent to the proper authorities. The address used for such
mail is configurable via the mailto Defaults entry (described later) and
defaults to root.
Note that no mail will be sent if an unauthorized user tries to run ssuuddoo
with the --ll or --vv option unless there is an authentication error and
either the mail_always or mail_badpass flags are enabled. This allows
users to determine for themselves whether or not they are allowed to use
ssuuddoo. All attempts to run ssuuddoo (successful or not) will be logged,
regardless of whether or not mail is sent.
If ssuuddoo is run by root and the SUDO_USER environment variable is set, the
ssuuddooeerrss policy will use this value to determine who the actual user is.
This can be used by a user to log commands through sudo even when a root
shell has been invoked. It also allows the --ee option to remain useful
even when invoked via a sudo-run script or program. Note, however, that
the sudoers file lookup is still done for root, not the user specified by
SUDO_USER.
ssuuddooeerrss uses per-user time stamp files for credential caching. Once a
user has been authenticated, a record is written containing the uid that
was used to authenticate, the terminal session ID, and a time stamp
(using a monotonic clock if one is available). The user may then use
ssuuddoo without a password for a short period of time (5 minutes unless
overridden by the timeout option). By default, ssuuddooeerrss uses a separate
record for each tty, which means that a user's login sessions are
authenticated separately. The tty_tickets option can be disabled to
force the use of a single time stamp for all of a user's sessions.
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ssuuddooeerrss can log both successful and unsuccessful attempts (as well as
errors) to syslog(3), a log file, or both. By default, ssuuddooeerrss will log
via syslog(3) but this is changeable via the syslog and logfile Defaults
settings. See LOG FORMAT for a description of the log file format.
ssuuddooeerrss is also capable of running a command in a pseudo-tty and logging
all input and/or output. The standard input, standard output and
standard error can be logged even when not associated with a terminal.
I/O logging is not on by default but can be enabled using the log_input
and log_output options as well as the LOG_INPUT and LOG_OUTPUT command
tags. See I/O LOG FILES for details on how I/O log files are stored.
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Since environment variables can influence program behavior, ssuuddooeerrss
provides a means to restrict which variables from the user's environment
are inherited by the command to be run. There are two distinct ways
ssuuddooeerrss can deal with environment variables.
By default, the env_reset option is enabled. This causes commands to be
executed with a new, minimal environment. On AIX (and Linux systems
without PAM), the environment is initialized with the contents of the
/etc/environment file. On BSD systems, if the use_loginclass option is
enabled, the environment is initialized based on the path and setenv
settings in /etc/login.conf. The new environment contains the TERM,
PATH, HOME, MAIL, SHELL, LOGNAME, USER, USERNAME and SUDO_* variables in
addition to variables from the invoking process permitted by the
env_check and env_keep options. This is effectively a whitelist for
environment variables. Environment variables with a value beginning with
() are removed unless both the name and value parts are matched by
env_keep or env_check, as they will be interpreted as functions by older
versions of the bbaasshh shell. Prior to version 1.8.11, such variables were
always removed.
If, however, the env_reset option is disabled, any variables not
explicitly denied by the env_check and env_delete options are inherited
from the invoking process. In this case, env_check and env_delete behave
like a blacklist. Environment variables with a value beginning with ()
are always removed, even if they do not match one of the blacklists.
Since it is not possible to blacklist all potentially dangerous
environment variables, use of the default env_reset behavior is
encouraged.
By default, environment variables are matched by name. However, if the
pattern includes an equal sign (`='), both the variables name and value
must match. For example, an old-style (pre-shellshock) bbaasshh shell
function could be matched as follows:
env_keep += "my_func=()*"
Without the ``=()*'' suffix, this would not match, as old-style bbaasshh
shell functions are not preserved by default.
The complete list of environment variables that ssuuddoo allows or denies is
contained in the output of ``sudo -V'' when run as root. Please note
that this list varies based on the operating system ssuuddoo is running on.
On systems that support PAM where the ppaamm_eennvv module is enabled for ssuuddoo,
variables in the PAM environment may be merged in to the environment. If
a variable in the PAM environment is already present in the user's
environment, the value will only be overridden if the variable was not
preserved by ssuuddooeerrss. When env_reset is enabled, variables preserved
from the invoking user's environment by the env_keep list take precedence
over those in the PAM environment. When env_reset is disabled, variables
present the invoking user's environment take precedence over those in the
PAM environment unless they match a pattern in the env_delete list.
Note that the dynamic linker on most operating systems will remove
variables that can control dynamic linking from the environment of setuid
executables, including ssuuddoo. Depending on the operating system this may
include _RLD*, DYLD_*, LD_*, LDR_*, LIBPATH, SHLIB_PATH, and others.
These type of variables are removed from the environment before ssuuddoo even
begins execution and, as such, it is not possible for ssuuddoo to preserve
them.
As a special case, if ssuuddoo's --ii option (initial login) is specified,
ssuuddooeerrss will initialize the environment regardless of the value of
env_reset. The DISPLAY, PATH and TERM variables remain unchanged; HOME,
MAIL, SHELL, USER, and LOGNAME are set based on the target user. On AIX
(and Linux systems without PAM), the contents of /etc/environment are
also included. On BSD systems, if the use_loginclass flag is enabled,
the path and setenv variables in /etc/login.conf are also applied. All
other environment variables are removed.
Finally, if the env_file option is defined, any variables present in that
file will be set to their specified values as long as they would not
conflict with an existing environment variable.
SSUUDDOOEERRSS FFIILLEE FFOORRMMAATT
The sudoers file is composed of two types of entries: aliases (basically
variables) and user specifications (which specify who may run what).
When multiple entries match for a user, they are applied in order. Where
there are multiple matches, the last match is used (which is not
necessarily the most specific match).
The sudoers file grammar will be described below in Extended Backus-Naur
Form (EBNF). Don't despair if you are unfamiliar with EBNF; it is fairly
simple, and the definitions below are annotated.
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EBNF is a concise and exact way of describing the grammar of a language.
Each EBNF definition is made up of production rules. E.g.,
symbol ::= definition | alternate1 | alternate2 ...
Each production rule references others and thus makes up a grammar for
the language. EBNF also contains the following operators, which many
readers will recognize from regular expressions. Do not, however,
confuse them with ``wildcard'' characters, which have different meanings.
? Means that the preceding symbol (or group of symbols) is optional.
That is, it may appear once or not at all.
* Means that the preceding symbol (or group of symbols) may appear
zero or more times.
+ Means that the preceding symbol (or group of symbols) may appear
one or more times.
Parentheses may be used to group symbols together. For clarity, we will
use single quotes ('') to designate what is a verbatim character string
(as opposed to a symbol name).
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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
Cmnd_Alias ::= NAME '=' Cmnd_List
NAME ::= [A-Z]([A-Z][0-9]_)*
Each alias definition is of the form
Alias_Type NAME = item1, item2, ...
where Alias_Type is one of User_Alias, Runas_Alias, Host_Alias, or
Cmnd_Alias. A NAME is a string of uppercase letters, numbers, and
underscore characters (`_'). A NAME 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
It is a syntax error to redefine an existing alias. It is possible to
use the same name for aliases of different types, but this is not
recommended.
The definitions of what constitutes a valid alias member follow.
User_List ::= User |
User ',' User_List
User ::= '!'* user name |
'!'* #uid |
'!'* %group |
'!'* %#gid |
'!'* +netgroup |
'!'* %:nonunix_group |
'!'* %:#nonunix_gid |
'!'* User_Alias
A User_List is made up of one or more user names, user IDs (prefixed with
`#'), system group names and IDs (prefixed with `%' and `%#'
respectively), netgroups (prefixed with `+'), non-Unix group names and
IDs (prefixed with `%:' and `%:#' respectively) 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. User netgroups are matched using the user and domain
members only; the host member is not used when matching.
A user name, uid, group, gid, netgroup, nonunix_group or nonunix_gid 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. When using double quotes, any prefix
characters must be included inside the quotes.
The actual nonunix_group and nonunix_gid syntax depends on the underlying
group provider plugin. For instance, the QAS AD plugin supports the
following formats:
+ Group in the same domain: "%:Group Name"
+ Group in any domain: "%:Group Name@FULLY.QUALIFIED.DOMAIN"
+ Group SID: "%:S-1-2-34-5678901234-5678901234-5678901234-567"
See GROUP PROVIDER PLUGINS for more information.
Note that quotes around group names are optional. Unquoted strings must
use a backslash (`\') to escape spaces and special characters. See Other
special characters and reserved words for a list of characters that need
to be escaped.
Runas_List ::= Runas_Member |
Runas_Member ',' Runas_List
Runas_Member ::= '!'* user name |
'!'* #uid |
'!'* %group |
'!'* %#gid |
'!'* %:nonunix_group |
'!'* %:#nonunix_gid |
'!'* +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. Host netgroups
are matched using the host (both qualified and unqualified) and domain
members only; the user member is not used when matching. If you specify
a network number without a netmask, 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, will use the netmask of that
interface. 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 fqdn option for wildcards to be useful. Note that 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.
digest ::= [A-Fa-f0-9]+ |
[[A-Za-z0-9+/=]+
Digest_Spec ::= "sha224" ':' digest |
"sha256" ':' digest |
"sha384" ':' digest |
"sha512" ':' digest
Cmnd_List ::= Cmnd |
Cmnd ',' Cmnd_List
command name ::= file name |
file name args |
file name '""'
Cmnd ::= Digest_Spec? '!'* command name |
'!'* directory |
'!'* "sudoedit" |
'!'* Cmnd_Alias
A Cmnd_List is a list of one or more command names, directories, and
other aliases. A command name is a fully qualified file name which may
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 sub-directories 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 built-in 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. Note that
``sudoedit'' is a command built into ssuuddoo itself and must be specified in
the sudoers file without a leading path.
If a command name is prefixed with a Digest_Spec, the command will only
match successfully if it can be verified using the specified SHA-2
digest. The following digest formats are supported: sha224, sha256,
sha384 and sha512. The string may be specified in either hex or base64
format (base64 is more compact). There are several utilities capable of
generating SHA-2 digests in hex format such as openssl, shasum,
sha224sum, sha256sum, sha384sum, sha512sum.
For example, using openssl:
$ openssl dgst -sha224 /bin/ls
SHA224(/bin/ls)= 118187da8364d490b4a7debbf483004e8f3e053ec954309de2c41a25
It is also possible to use openssl to generate base64 output:
$ openssl dgst -binary -sha224 /bin/ls | openssl base64
EYGH2oNk1JC0p9679IMATo8+BT7JVDCd4sQaJQ==
Warning, if the user has write access to the command itself (directly or
via a ssuuddoo command), it may be possible for the user to replace the
command after the digest check has been performed but before the command
is executed. A similar race condition exists on systems that lack the
fexecve(2) system call when the directory in which the command is located
is writable by the user.
Command digests are only supported by version 1.8.7 or higher.
DDeeffaauullttss
Certain configuration options may be changed from their default values at
run-time 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.
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? Solaris_Priv_Spec? Tag_Spec* Cmnd
Runas_Spec ::= '(' Runas_List? (':' Runas_List)? ')'
SELinux_Spec ::= ('ROLE=role' | 'TYPE=type')
Solaris_Priv_Spec ::= ('PRIVS=privset' | 'LIMITPRIVS=privset')
Tag_Spec ::= ('EXEC:' | 'NOEXEC:' | 'FOLLOW:' | 'NOFOLLOW' |
'LOG_INPUT:' | 'NOLOG_INPUT:' | 'LOG_OUTPUT:' |
'NOLOG_OUTPUT:' | 'MAIL:' | 'NOMAIL:' | 'PASSWD:' |
'NOPASSWD:' | 'SETENV:' | 'NOSETENV:')
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 both Runas_Lists are empty, the
command may only be run as the invoking user. 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 /bin/ls, /bin/kill, and /usr/bin/lprm--but only as
ooppeerraattoorr. E.g.,
$ sudo -u operator /bin/ls
It is also possible to override a Runas_Spec later on in an entry. If we
modify the entry like so:
dgb boulder = (operator) /bin/ls, (root) /bin/kill, /usr/bin/lprm
Then user ddggbb is now allowed to run /bin/ls as ooppeerraattoorr, but /bin/kill
and /usr/bin/lprm 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
Note that while the group portion of the Runas_Spec permits the user to
run as command with that group, it does not force the user to do so. If
no group is specified on the command line, the command will run with the
group listed in the target user's password database entry. The following
would all be permitted by the sudoers entry above:
$ sudo -u operator /bin/ls
$ sudo -u operator -g operator /bin/ls
$ sudo -g operator /bin/ls
In the following example, user ttccmm may run commands that access a modem
device file with the dialer group.
tcm boulder = (:dialer) /usr/bin/tip, /usr/bin/cu,\
/usr/local/bin/minicom
Note that in this example only the group will be set, the command still
runs as user ttccmm. E.g.
$ sudo -g dialer /usr/bin/cu
Multiple users and groups may be present in a Runas_Spec, in which case
the user may select any combination of users and groups via the --uu and --gg
options. In this example:
alan ALL = (root, bin : operator, system) ALL
user aallaann may run any command as either user root or bin, optionally
setting the group to operator or system.
SSEELLiinnuuxx_SSppeecc
On systems with SELinux support, sudoers file 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 sudoers. A role or type specified on the command line,
however, will supersede the values in sudoers.
SSoollaarriiss_PPrriivv_SSppeecc
On Solaris systems, sudoers file entries may optionally specify Solaris
privilege set and/or limit privilege set associated with a command. If
privileges or limit privileges are specified with the command it will
override any default values specified in sudoers.
A privilege set is a comma-separated list of privilege names. The
ppriv(1) command can be used to list all privileges known to the system.
For example:
$ ppriv -l
In addition, there are several ``special'' privilege strings:
none the empty set
all the set of all privileges
zone the set of all privileges available in the current zone
basic the default set of privileges normal users are granted at login
time
Privileges can be excluded from a set by prefixing the privilege name
with either an `!' or `-' character.
TTaagg_SSppeecc
A command may have zero or more tags associated with it. There are ten
possible tag values: EXEC, NOEXEC, FOLLOW, NOFOLLOW, LOG_INPUT,
NOLOG_INPUT, LOG_OUTPUT, NOLOG_OUTPUT, MAIL, NOMAIL, PASSWD, NOPASSWD,
SETENV, and NOSETENV. Once a tag is set on a Cmnd, subsequent Cmnds in
the Cmnd_Spec_List, inherit the tag unless it is overridden by the
opposite tag (in other words, PASSWD overrides NOPASSWD and NOEXEC
overrides EXEC).
EXEC and NOEXEC
If ssuuddoo has been compiled with noexec support and the underlying
operating system supports it, the NOEXEC tag can be used to prevent a
dynamically-linked executable from running further commands itself.
In the following example, user aaaarroonn may run /usr/bin/more and
/usr/bin/vi but shell escapes will be disabled.
aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
See the Preventing shell escapes section below for more details on how
NOEXEC works and whether or not it will work on your system.
FOLLOW and NOFOLLOW Starting with version 1.8.15, ssuuddooeeddiitt will not open
a file that is a symbolic link unless the sudoedit_follow option is
enabled. The FOLLOW and NOFOLLOW tags override the value of
sudoedit_follow and can be used to permit (or deny) the editing of
symbolic links on a per-command basis. These tags are only effective
for the sudoedit command and are ignored for all other commands.
LOG_INPUT and NOLOG_INPUT
These tags override the value of the log_input option on a per-command
basis. For more information, see the description of log_input in the
SUDOERS OPTIONS section below.
LOG_OUTPUT and NOLOG_OUTPUT
These tags override the value of the log_output option on a per-command
basis. For more information, see the description of log_output in the
SUDOERS OPTIONS section below.
MAIL and NOMAIL
These tags provide fine-grained control over whether mail will be sent
when a user runs a command by overriding the value of the
mail_all_cmnds option on a per-command basis. They have no effect when
ssuuddoo is run with the --ll or --vv options. A NOMAIL tag will also override
the mail_always and mail_no_perms options. For more information, see
the descriptions of mail_all_cmnds, mail_always, and mail_no_perms in
the SUDOERS OPTIONS section below.
PASSWD and NOPASSWD
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 /bin/kill, /bin/ls, and /usr/bin/lprm
as rroooott on the machine rushmore without authenticating himself. If we
only want rraayy to be able to run /bin/kill without a password the entry
would be:
ray rushmore = NOPASSWD: /bin/kill, PASSWD: /bin/ls, /usr/bin/lprm
Note, however, that the PASSWD tag has no effect on users who are in
the group specified by the exempt_group option.
By default, if the NOPASSWD tag is applied to any of the entries for a
user on the current host, he or she will be able to run ``sudo -l''
without a password. Additionally, a user may only run ``sudo -v''
without a password if the NOPASSWD tag is present for all a user's
entries that pertain to the current host. This behavior may be
overridden via the verifypw and listpw options.
SETENV and NOSETENV
These tags override the value of the setenv option on a per-command
basis. Note that if SETENV has been set for a command, the user may
disable the env_reset option from the command line via the --EE option.
Additionally, environment variables set on the command line are not
subject to the restrictions imposed by env_check, env_delete, or
env_keep. As such, only trusted users should be allowed to set
variables in this manner. 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.
WWiillddccaarrddss
ssuuddoo allows shell-style wildcards (aka meta or glob characters) to be
used in host names, path names and command line arguments in the sudoers
file. Wildcard matching is done via the glob(3) and fnmatch(3) functions
as specified by IEEE Std 1003.1 (``POSIX.1'').
* Matches any set of zero or more characters (including white
space).
? Matches any single character (including white space).
[...] Matches any character in the specified range.
[!...] Matches any character not in the specified range.
\x For any character `x', evaluates to `x'. This is used to
escape special characters such as: `*', `?', `[', and `]'.
NNoottee tthhaatt tthheessee aarree nnoott rreegguullaarr eexxpprreessssiioonnss.. Unlike a regular expression
there is no way to match one or more characters within a range.
Character classes may be used if your system's glob(3) and fnmatch(3)
functions support them. However, because the `:' character has special
meaning in sudoers, it must be escaped. For example:
/bin/ls [[\:alpha\:]]*
Would match any file name beginning with a letter.
Note that a forward slash (`/') will not be matched by wildcards used in
the file name portion of the command. This is to make a path like:
/usr/bin/*
match /usr/bin/who but not /usr/bin/X11/xterm.
When matching the command line arguments, however, a slash does get
matched by wildcards since command line arguments may contain arbitrary
strings and not just path names.
WWiillddccaarrddss iinn ccoommmmaanndd lliinnee aarrgguummeennttss sshhoouulldd bbee uusseedd wwiitthh ccaarree..
Command line arguments are matched as a single, concatenated string.
This mean a wildcard character such as `?' or `*' will match across word
boundaries, which may be unexpected. For example, while a sudoers entry
like:
%operator ALL = /bin/cat /var/log/messages*
will allow command like:
$ sudo cat /var/log/messages.1
It will also allow:
$ sudo cat /var/log/messages /etc/shadow
which is probably not what was intended. In most cases it is better to
do command line processing outside of the sudoers file in a scripting
language.
EExxcceeppttiioonnss ttoo wwiillddccaarrdd rruulleess
The following exceptions apply to the above rules:
"" If the empty string "" is the only command line argument in the
sudoers file entry it means that command is not allowed to be
run with any arguments.
sudoedit Command line arguments to the sudoedit built-in command should
always be path names, so a forward slash (`/') will not be
matched by a wildcard.
IInncclluuddiinngg ootthheerr ffiilleess ffrroomm wwiitthhiinn ssuuddooeerrss
It is possible to include other sudoers files from within the sudoers
file currently being parsed using the #include and #includedir
directives.
This can be used, for example, to keep a site-wide sudoers file in
addition to a local, per-machine file. For the sake of this example the
site-wide sudoers file will be /etc/sudoers and the per-machine one will
be /etc/sudoers.local. To include /etc/sudoers.local from within
/etc/sudoers we would use the following line in /etc/sudoers:
#include /etc/sudoers.local
When ssuuddoo reaches this line it will suspend processing of the current
file (/etc/sudoers) and switch to /etc/sudoers.local. Upon reaching the
end of /etc/sudoers.local, the rest of /etc/sudoers will be processed.
Files that are included may themselves include other files. A hard limit
of 128 nested include files is enforced to prevent include file loops.
If the path to the include file is not fully-qualified (does not begin
with a `/', it must be located in the same directory as the sudoers file
it was included from. For example, if /etc/sudoers contains the line:
#include sudoers.local
the file that will be included is /etc/sudoers.local.
The file name may also include the %h escape, signifying the short form
of the host name. In other words, if the machine's host name is
``xerxes'', then
#include /etc/sudoers.%h
will cause ssuuddoo to include the file /etc/sudoers.xerxes.
The #includedir directive can be used to create a sudoers.d directory
that the system package manager can drop sudoers file rules into as part
of package installation. For example, given:
#includedir /etc/sudoers.d
ssuuddoo will read each file in /etc/sudoers.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, /etc/sudoers.d/01_first will be parsed before
/etc/sudoers.d/10_second. Be aware that because the sorting is lexical,
not numeric, /etc/sudoers.d/1_whoops would be loaded after
/etc/sudoers.d/10_second. 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 --ff flag to edit the
files directly, but this will not catch the redefinition of an alias that
is also present in a different file.
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 alias that always causes a match to
succeed. It can be used wherever one might otherwise use a Cmnd_Alias,
User_Alias, Runas_Alias, or Host_Alias. You should not try to define
your own alias called 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 any command on the
system.
An exclamation point (`!') can be used as a logical not operator in a
list or alias as well as in front of a Cmnd. This allows one to exclude
certain values. For the `!' operator to be effective, there must be
something for it to exclude. For example, to match all users except for
root one would use:
ALL,!root
If the AALLLL, is omitted, as in:
!root
it would explicitly deny root but not match any other users. This is
different from a true ``negation'' operator.
Note, however, that using a `!' in conjunction with the built-in AALLLL
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.
White space between elements in a list as well as special syntactic
characters in a User Specification (`=', `:', `(', `)') is optional.
The following characters must be escaped with a backslash (`\') when used
as part of a word (e.g. a user name or host name): `!', `=', `:', `,',
`(', `)', `\'.
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_query_group_plugin
If a group_plugin is configured, use it to resolve
groups of the form %group as long as there is not also
a system group of the same name. Normally, only groups
of the form %:group are passed to the group_plugin.
This flag is off by default.
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 by
default, HOME will be set to the home directory of the
target user when the env_reset option is enabled, so
always_set_home only has an effect for configurations
where either env_reset is disabled or HOME is present
in the env_keep list. This flag is off by default.
authenticate If set, users must authenticate themselves via a
password (or other means of authentication) before they
may run commands. This default may be overridden via
the PASSWD and NOPASSWD tags. This flag is on by
default.
closefrom_override
If set, the user may use ssuuddoo's --CC option which
overrides the default starting point at which ssuuddoo
begins closing open file descriptors. This flag is off
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 on by default when ssuuddoo is compiled with
zzlliibb support.
exec_background By default, ssuuddoo runs a command as the foreground
process as long as ssuuddoo itself is running in the
foreground. When the exec_background flag is enabled
and the command is being run in a pty (due to I/O
logging or the use_pty flag), the command will be run
as a background process. Attempts to read from the
controlling terminal (or to change terminal settings)
will result in the command being suspended with the
SIGTTIN signal (or SIGTTOU in the case of terminal
settings). If this happens when ssuuddoo is a foreground
process, the command will be granted the controlling
terminal and resumed in the foreground with no user
intervention required. The advantage of initially
running the command in the background is that ssuuddoo need
not read from the terminal unless the command
explicitly requests it. Otherwise, any terminal input
must be passed to the command, whether it has required
it or not (the kernel buffers terminals so it is not
possible to tell whether the command really wants the
input). This is different from historic sudo behavior
or when the command is not being run in a pty.
For this to work seamlessly, the operating system must
support the automatic restarting of system calls.
Unfortunately, not all operating systems do this by
default, and even those that do may have bugs. For
example, Mac OS X fails to restart the ttccggeettaattttrr() and
ttccsseettaattttrr() system calls (this is a bug in Mac OS X).
Furthermore, because this behavior depends on the
command stopping with the SIGTTIN or SIGTTOU signals,
programs that catch these signals and suspend
themselves with a different signal (usually SIGTOP)
will not be automatically foregrounded. Some versions
of the linux su(1) command behave this way. This flag
is off by default.
This setting is only supported by version 1.8.7 or
higher. It has no effect unless I/O logging is enabled
or the use_pty flag is enabled.
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. If the env_reset flag is enabled,
the EDITOR and/or VISUAL environment variables must be
present in the env_keep list for the env_editor flag to
function when vviissuuddoo is invoked via ssuuddoo. This flag is
off by default.
env_reset If set, ssuuddoo will run the command in a minimal
environment containing the TERM, PATH, HOME, MAIL,
SHELL, LOGNAME, USER, USERNAME and SUDO_* variables.
Any variables in the caller's environment that match
the env_keep and env_check lists are then added,
followed by any variables present in the file specified
by the env_file option (if any). The contents of the
env_keep and env_check lists, as modified by global
Defaults parameters in sudoers, are displayed when ssuuddoo
is run by root with the --VV option. If the secure_path
option is set, its value will be used for the PATH
environment variable. This flag is on by default.
fast_glob Normally, ssuuddoo uses the glob(3) function to do shell-
style globbing when matching path names. However,
since it accesses the file system, glob(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 (auto mounted). The fast_glob
option causes ssuuddoo to use the fnmatch(3) function,
which does not access the file system to do its
matching. The disadvantage of fast_glob is that it is
unable to match relative path names such as ./ls or
../bin/ls. 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 the sudoers file contains rules that contain
negated path names which include globbing characters.
This flag is off by default.
fqdn Set this flag if you want to put fully qualified host
names in the sudoers file when the local host name (as
returned by the hostname command) does not contain the
domain name. In other words, instead of myhost you
would use myhost.mydomain.edu. You may still use the
short form if you wish (and even mix the two). This
option is only effective when the ``canonical'' host
name, as returned by the ggeettaaddddrriinnffoo() or
ggeetthhoossttbbyynnaammee() function, is a fully-qualified domain
name. This is usually the case when the system is
configured to use DNS for host name resolution.
If the system is configured to use the /etc/hosts file
in preference to DNS, the ``canonical'' host name may
not be fully-qualified. The order that sources are
queried for host name resolution is usually specified
in the /etc/nsswitch.conf, /etc/netsvc.conf,
/etc/host.conf, or, in some cases, /etc/resolv.conf
file. In the /etc/hosts file, the first host name of
the entry is considered to be the ``canonical'' name;
subsequent names are aliases that are not used by
ssuuddooeerrss. For example, the following hosts file line
for the machine ``xyzzy'' has the fully-qualified
domain name as the ``canonical'' host name, and the
short version as an alias.
192.168.1.1 xyzzy.sudo.ws xyzzy
If the machine's hosts file entry is not formatted
properly, the fqdn option will not be effective if it
is queried before DNS.
Beware that when using DNS for host name resolution,
turning on fqdn requires ssuuddooeerrss to make DNS lookups
which renders ssuuddoo unusable if DNS stops working (for
example if the machine is disconnected from the
network). Also note that just like with the hosts
file, you must use the ``canonical'' 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.
This flag is off by default.
ignore_dot If set, ssuuddoo will ignore "." or "" (both denoting
current directory) in the PATH environment variable;
the PATH itself is not modified. This flag is off by
default.
ignore_local_sudoers
If set via LDAP, parsing of /etc/sudoers will be
skipped. This is intended for Enterprises that wish to
prevent the usage of local sudoers files so that only
LDAP is used. This thwarts the efforts of rogue
operators who would attempt to add roles to
/etc/sudoers. When this option is present,
/etc/sudoers does not even need to exist. Since this
option tells 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
off by default.
insults If set, ssuuddoo will insult users when they enter an
incorrect password. This flag is off by default.
log_host If set, the host name will be logged in the (non-
syslog) ssuuddoo log file. This flag is off by default.
log_input If set, ssuuddoo will run the command in a pseudo-tty 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.
For more information, see the I/O LOG FILES section.
This flag is off by default.
log_output If set, ssuuddoo will run the command in a pseudo-tty and
log all output that is sent to the screen, similar to
the script(1) command. For more information, see the
I/O LOG FILES section. This flag is off by default.
log_year If set, the four-digit year will be logged in the (non-
syslog) ssuuddoo log file. This flag is off by default.
long_otp_prompt When validating with a One Time Password (OTP) 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 off
by default.
mail_all_cmnds Send mail to the mailto user every time a user attempts
to run a command via ssuuddoo (this includes ssuuddooeeddiitt). No
mail will be sent if the user runs ssuuddoo with the --ll or
--vv option unless there is an authentication error and
the mail_badpass flag is also set. This flag is off by
default.
mail_always Send mail to the mailto user every time a user runs
ssuuddoo. This flag is off by default.
mail_badpass Send mail to the mailto user if the user running ssuuddoo
does not enter the correct password. If the command
the user is attempting to run is not permitted by
ssuuddooeerrss and one of the mail_all_cmnds, mail_always,
mail_no_host, mail_no_perms or mail_no_user flags are
set, this flag will have no effect. This flag is off
by default.
mail_no_host If set, mail will be sent to the mailto user if the
invoking user exists in the sudoers file, but is not
allowed to run commands on the current host. This flag
is off by default.
mail_no_perms If set, mail will be sent to the mailto user if the
invoking user is allowed to use ssuuddoo but the command
they are trying is not listed in their sudoers file
entry or is explicitly denied. This flag is off by
default.
mail_no_user If set, mail will be sent to the mailto user if the
invoking user is not in the sudoers file. This flag is
on by default.
netgroup_tuple If set, netgroup lookups will be performed using the
full netgroup tuple: host name, user name and domain
(if one is set). Historically, ssuuddoo only matched the
user name and domain for netgroups used in a User_List
and only matched the host name and domain for netgroups
used in a Host_List. This flag is off by default.
noexec If set, all commands run via ssuuddoo will behave as if the
NOEXEC tag has been set, unless overridden by an EXEC
tag. See the description of EXEC and NOEXEC above as
well as the Preventing shell escapes section at the end
of this manual. This flag is off by default.
pam_session On systems that use PAM for authentication, ssuuddoo will
create a new PAM session for the command to be run in.
Disabling pam_session may be needed on older PAM
implementations or on operating systems where opening a
PAM session changes the utmp or wtmp files. If PAM
session support is disabled, resource limits may not be
updated for the command being run. If pam_session,
pam_setcred, and use_pty are disabled and I/O logging
has not been configured, ssuuddoo will execute the command
directly instead of running it as a child process.
This flag is on by default.
This setting is only supported by version 1.8.7 or
higher.
pam_setcred On systems that use PAM for authentication, ssuuddoo will
attempt to establish credentials for the target user by
default, if supported by the underlying authentication
system. One example of a credential is a Kerberos
ticket. If pam_session, pam_setcred, and use_pty are
disabled and I/O logging has not been configured, ssuuddoo
will execute the command directly instead of running it
as a child process. This flag is on by default.
This setting is only supported by version 1.8.8 or
higher.
passprompt_override
The password prompt specified by passprompt will
normally only be used if the password prompt provided
by systems such as PAM matches the string
``Password:''. If passprompt_override is set,
passprompt will always be used. This flag is off by
default.
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 on by default.
preserve_groups By default, ssuuddoo will initialize the group vector to
the list of groups the target user is in. When
preserve_groups is set, the user's existing group
vector is left unaltered. The real and effective group
IDs, however, are still set to match the target user.
This flag is off by default.
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 pwfeedback 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 off 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 cron(1m) or cgi-bin scripts. This flag is off 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 root_sudo
will also prevent root from running ssuuddooeeddiitt.
Disabling root_sudo provides no real additional
security; it exists purely for historical reasons.
This flag is on by default.
rootpw If set, ssuuddoo will prompt for the root password instead
of the password of the invoking user when running a
command or editing a file. This flag is off by
default.
runaspw If set, ssuuddoo will prompt for the password of the user
defined by the runas_default option (defaults to root)
instead of the password of the invoking user when
running a command or editing a file. This flag is off
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 env_reset option is enabled, so set_home is only
effective for configurations where either env_reset is
disabled or HOME is present in the env_keep list. This
flag is off by default.
set_logname Normally, ssuuddoo will set the LOGNAME, USER and USERNAME
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 set_logname will have no effect if the
env_reset option has not been disabled and the env_keep
list contains LOGNAME, USER or USERNAME. This flag is
on by default.
set_utmp When enabled, ssuuddoo will create an entry in the utmp (or
utmpx) file when a pseudo-tty is allocated. A pseudo-
tty is allocated by ssuuddoo when the log_input, log_output
or use_pty flags are enabled. By default, the new
entry will be a copy of the user's existing utmp entry
(if any), with the tty, time, type and pid fields
updated. This flag is on by default.
setenv Allow the user to disable the env_reset option from the
command line via the --EE option. Additionally,
environment variables set via the command line are not
subject to the restrictions imposed by env_check,
env_delete, or env_keep. As such, only trusted users
should be allowed to set variables in this manner.
This flag is off by default.
shell_noargs If set and 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 off 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
that support either the setreuid(2) or setresuid(2)
system call. This flag is off by default.
sudoedit_checkdir
If set, ssuuddooeeddiitt will check all directory components of
the path to be edited for writability by the invoking
user. Symbolic links will not be followed in writable
directories and ssuuddooeeddiitt will refuse to edit a file
located in a writable directory. These restrictions
are not enforced when ssuuddooeeddiitt is run by root. On some
systems, if all directory components of the path to be
edited are not readable by the target user, ssuuddooeeddiitt
will be unable to edit the file. This flag is on by
default.
This setting was first introduced in version 1.8.15 but
initially suffered from a race condition. The check
for symbolic links in writable intermediate directories
was added in version 1.8.16.
sudoedit_follow By default, ssuuddooeeddiitt will not follow symbolic links
when opening files. The sudoedit_follow option can be
enabled to allow ssuuddooeeddiitt to open symbolic links. It
may be overridden on a per-command basis by the FOLLOW
and NOFOLLOW tags. This flag is off by default.
This setting is only supported by version 1.8.15 or
higher.
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 when running a
command or editing a file. 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
off by default.
tty_tickets If set, users must authenticate on a per-tty basis.
With this flag enabled, ssuuddoo will use a separate record
in the time stamp file for each tty. If disabled, a
single record is used for all login sessions. This
flag is on by default.
umask_override If set, ssuuddoo will set the umask as specified in the
sudoers file without modification. This makes it
possible to specify a umask in the sudoers file that is
more permissive than the user's own umask and matches
historical behavior. If umask_override is not set,
ssuuddoo will set the umask to be the union of the user's
umask and what is specified in sudoers. This flag is
off 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 off by default.
use_netgroups If set, netgroups (prefixed with `+'), may be used in
place of a user or host. For LDAP-based sudoers,
netgroup support requires an expensive substring match
on the server unless the NNEETTGGRROOUUPP_BBAASSEE directive is
present in the /etc/ldap.conf file. If netgroups are
not needed, this option can be disabled to reduce the
load on the LDAP server. This flag is on 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. This flag is
off by default.
utmp_runas If set, ssuuddoo will store the name of the runas user when
updating the utmp (or utmpx) file. By default, ssuuddoo
stores the name of the invoking user. This flag is off
by default.
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 visiblepw 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 ``ssh somehost sudo ls'' since by default,
ssh(1) does not allocate a tty when running a command.
This flag is off by default.
IInntteeggeerrss:
closefrom Before it executes a command, ssuuddoo will close all open
file descriptors other than standard input, standard
output and standard error (ie: file descriptors 0-2).
The closefrom option can be used to specify a different
file descriptor at which to start closing. The default
is 3.
maxseq The maximum sequence number that will be substituted
for the ``%{seq}'' escape in the I/O log file (see the
iolog_dir description above for more information).
While the value substituted for ``%{seq}'' is in base
36, maxseq itself should be expressed in decimal.
Values larger than 2176782336 (which corresponds to the
base 36 sequence number ``ZZZZZZ'') will be silently
truncated to 2176782336. The default value is
2176782336.
Once the local sequence number reaches the value of
maxseq, it will ``roll over'' to zero, after which
ssuuddooeerrss will truncate and re-use any existing I/O log
path names.
This setting is only supported by version 1.8.7 or
higher.
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 time stamp will not expire
until the system is rebooted. This can be used to
allow users to create or delete their own time stamps
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 the value of the umask option, which
defaults to 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 sudoers.
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 or VISUAL environment
variable if possible, or the first editor in the list
that exists and is executable. Note that the EDITOR
and VISUAL environment variables are not preserved by
default when the env_reset option is enabled. The
default is vi.
iolog_dir The top-level directory to use when constructing the
path name for the input/output log directory. Only
used if the log_input or log_output options are enabled
or when the LOG_INPUT or LOG_OUTPUT tags are present
for a command. The session sequence number, if any, is
stored in the directory. The default is
/var/log/sudo-io.
The following percent (`%') escape sequences are
supported:
%{seq}
expanded to a monotonically increasing base-36
sequence number, such as 0100A5, where every two
digits are used to form a new directory, e.g.
01/00/A5
%{user}
expanded to the invoking user's login name
%{group}
expanded to the name of the invoking user's real
group ID
%{runas_user}
expanded to the login name of the user the
command will be run as (e.g. root)
%{runas_group}
expanded to the group name of the user the
command will be run as (e.g. wheel)
%{hostname}
expanded to the local host name without the
domain name
%{command}
expanded to the base name of the command being
run
In addition, any escape sequences supported by the
system's strftime(3) function will be expanded.
To include a literal `%' character, the string `%%'
should be used.
iolog_file The path name, relative to iolog_dir, in which to store
input/output logs when the log_input or log_output
options are enabled or when the LOG_INPUT or LOG_OUTPUT
tags are present for a command. Note that iolog_file
may contain directory components. The default is
``%{seq}''.
See the iolog_dir option above for a list of supported
percent (`%') escape sequences.
In addition to the escape sequences, path names that
end in six or more Xs will have the Xs replaced with a
unique combination of digits and letters, similar to
the mktemp(3) function.
If the path created by concatenating iolog_dir and
iolog_file already exists, the existing I/O log file
will be truncated and overwritten unless iolog_file
ends in six or more Xs.
lecture_status_dir
The directory in which ssuuddoo stores per-user lecture
status files. Once a user has received the lecture, a
zero-length file is created in this directory so that
ssuuddoo will not lecture the user again. This directory
should not be cleared when the system reboots. The
default is /var/adm/sudo/lectured.
limitprivs The default Solaris limit privileges to use when
constructing a new privilege set for a command. This
bounds all privileges of the executing process. The
default limit privileges may be overridden on a per-
command basis in sudoers. This option is only
available if ssuuddooeerrss is built on Solaris 10 or higher.
mailsub Subject of the mail sent to the mailto user. The
escape %h will expand to the host name of the machine.
Default is ``*** SECURITY information for %h ***''.
noexec_file As of ssuuddoo version 1.8.1 this option is no longer
supported. The path to the noexec file should now be
set in the sudo.conf(4) file.
pam_login_service
On systems that use PAM for authentication, this is the
service name used when the --ii option is specified. The
default value is ``sudo''. See the description of
pam_service for more information.
This setting is only supported by version 1.8.8 or
higher.
pam_service On systems that use PAM for authentication, the service
name specifies the PAM policy to apply. This usually
corresponds to an entry in the pam.conf file or a file
in the /etc/pam.d directory. The default value is
``sudo''.
This setting is only supported by version 1.8.8 or
higher.
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 (`%')
escape sequences are supported:
%H expanded to the local host name including the
domain name (only if the machine's host name is
fully qualified or the fqdn 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 rootpw, targetpw and
runaspw flags in sudoers)
%U expanded to the login name of the user the
command will be run as (defaults to root)
%u expanded to the invoking user's login name
%% two consecutive % characters are collapsed into a
single % character
The default value is ``Password:''.
privs The default Solaris privileges to use when constructing
a new privilege set for a command. This is passed to
the executing process via the inherited privilege set,
but is bounded by the limit privileges. If the privs
option is specified but the limitprivs option is not,
the limit privileges of the executing process is set to
privs. The default privileges may be overridden on a
per-command basis in sudoers. This option is only
available if ssuuddooeerrss is built on Solaris 10 or higher.
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 the sudoers
file or via command line options. This option is only
available when 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.
syslog_badpri Syslog priority to use when user authenticates
unsuccessfully. Defaults to alert.
The following syslog priorities are supported: aalleerrtt,
ccrriitt, ddeebbuugg, eemmeerrgg, eerrrr, iinnffoo, nnoottiiccee, and wwaarrnniinngg.
syslog_goodpri Syslog priority to use when user authenticates
successfully. Defaults to notice.
See syslog_badpri for the list of supported syslog
priorities.
sudoers_locale Locale to use when parsing the sudoers file, logging
commands, and sending email. Note that changing the
locale may affect how sudoers is interpreted. Defaults
to ``C''.
timestampdir The directory in which ssuuddoo stores its time stamp
files. This directory should be cleared when the
system reboots. The default is /var/run/sudo/ts.
timestampowner The owner of the lecture status directory, time stamp
directory and all files 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 the sudoers
file or via command line options. This option is only
available when ssuuddoo is built with SELinux support.
SSttrriinnggss tthhaatt ccaann bbee uusseedd iinn aa bboooolleeaann ccoonntteexxtt:
env_file The env_file option 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 env_keep
and env_check.
exempt_group Users in this group are exempt from password and PATH
requirements. The group name specified should not include
a % prefix. This is not set by default.
group_plugin A string containing a ssuuddooeerrss group plugin with optional
arguments. The string should consist of the plugin path,
either fully-qualified or relative to the
/usr/local/libexec/sudo directory, followed by any
configuration arguments the plugin requires. These
arguments (if any) will be passed to the plugin's
initialization function. If arguments are present, the
string must be enclosed in double quotes ("").
For more information see GROUP PROVIDER PLUGINS.
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 once is implied.
Negating the option results in a value of never being used.
The default value is once.
lecture_file Path to a file containing an alternate 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 sudoers file 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 sudoers file 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 any is implied.
Negating the option results in a value of never being used.
The default value is any.
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
exempt_group option are not affected by secure_path. This
option is not set by default.
syslog Syslog facility if syslog is being used for logging (negate
to disable syslog logging). Defaults to auth.
The following syslog facilities are supported: aauutthhpprriivv (if
your OS supports it), aauutthh, ddaaeemmoonn, uusseerr, llooccaall00, llooccaall11,
llooccaall22, llooccaall33, llooccaall44, llooccaall55, llooccaall66, and llooccaall77.
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 sudoers file 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 sudoers file 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 all is implied.
Negating the option results in a value of never being used.
The default value is all.
LLiissttss tthhaatt ccaann bbee uusseedd iinn aa bboooolleeaann ccoonntteexxtt:
env_check Environment variables to be removed from the user's
environment unless they are considered ``safe''. For
all variables except TZ, ``safe'' means that the
variable's value does not contain any `%' or `/'
characters. This can be used to guard against printf-
style format vulnerabilities in poorly-written
programs. The TZ variable is considered unsafe if any
of the following are true:
+ It consists of a fully-qualified path name,
optionally prefixed with a colon (`:'), that does
not match the location of the zoneinfo directory.
+ It contains a .. path element.
+ It contains white space or non-printable
characters.
+ It is longer than the value of PATH_MAX.
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 global list of environment
variables to check is displayed when ssuuddoo is run by
root with the --VV option.
env_delete Environment variables to be removed from the user's
environment when the env_reset 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
global list of environment variables to remove is
displayed when ssuuddoo is run by root with the --VV 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
environment when the env_reset 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 global list of
variables to keep is displayed when ssuuddoo is run by root
with the --VV option.
GGRROOUUPP PPRROOVVIIDDEERR PPLLUUGGIINNSS
The ssuuddooeerrss plugin supports its own plugin interface to allow non-Unix
group lookups which can query a group source other than the standard Unix
group database. This can be used to implement support for the
nonunix_group syntax described earlier.
Group provider plugins are specified via the group_plugin Defaults
setting. The argument to group_plugin should consist of the plugin path,
either fully-qualified or relative to the /usr/local/libexec/sudo
directory, followed by any configuration options the plugin requires.
These options (if specified) will be passed to the plugin's
initialization function. If options are present, the string must be
enclosed in double quotes ("").
The following group provider plugins are installed by default:
group_file
The group_file plugin supports an alternate group file that
uses the same syntax as the /etc/group file. The path to the
group file should be specified as an option to the plugin. For
example, if the group file to be used is /etc/sudo-group:
Defaults group_plugin="group_file.so /etc/sudo-group"
system_group
The system_group plugin supports group lookups via the standard
C library functions ggeettggrrnnaamm() and ggeettggrriidd(). This plugin can
be used in instances where the user belongs to groups not
present in the user's supplemental group vector. This plugin
takes no options:
Defaults group_plugin=system_group.so
The group provider plugin API is described in detail in sudo_plugin(1m).
LLOOGG FFOORRMMAATT
ssuuddooeerrss can log events using either syslog(3) or a simple log file. The
log format is almost identical in both cases.
AAcccceepptteedd ccoommmmaanndd lloogg eennttrriieess
Commands that sudo runs are logged using the following format (split into
multiple lines for readability):
date hostname progname: username : TTY=ttyname ; PWD=cwd ; \
USER=runasuser ; GROUP=runasgroup ; TSID=logid ; \
ENV=env_vars COMMAND=command
Where the fields are as follows:
date The date the command was run. Typically, this is in the
format ``MMM, DD, HH:MM:SS''. If logging via syslog(3),
the actual date format is controlled by the syslog daemon.
If logging to a file and the log_year option is enabled,
the date will also include the year.
hostname The name of the host ssuuddoo was run on. This field is only
present when logging via syslog(3).
progname The name of the program, usually sudo or sudoedit. This
field is only present when logging via syslog(3).
username The login name of the user who ran ssuuddoo.
ttyname The short name of the terminal (e.g. ``console'',
``tty01'', or ``pts/0'') ssuuddoo was run on, or ``unknown'' if
there was no terminal present.
cwd The current working directory that ssuuddoo was run in.
runasuser The user the command was run as.
runasgroup The group the command was run as if one was specified on
the command line.
logid An I/O log identifier that can be used to replay the
command's output. This is only present when the log_input
or log_output option is enabled.
env_vars A list of environment variables specified on the command
line, if specified.
command The actual command that was executed.
Messages are logged using the locale specified by sudoers_locale, which
defaults to the ``C'' locale.
DDeenniieedd ccoommmmaanndd lloogg eennttrriieess
If the user is not allowed to run the command, the reason for the denial
will follow the user name. Possible reasons include:
user NOT in sudoers
The user is not listed in the sudoers file.
user NOT authorized on host
The user is listed in the sudoers file but is not allowed to run
commands on the host.
command not allowed
The user is listed in the sudoers file for the host but they are not
allowed to run the specified command.
3 incorrect password attempts
The user failed to enter their password after 3 tries. The actual
number of tries will vary based on the number of failed attempts and
the value of the passwd_tries option.
a password is required
ssuuddoo's --nn option was specified but a password was required.
sorry, you are not allowed to set the following environment variables
The user specified environment variables on the command line that were
not allowed by sudoers.
EErrrroorr lloogg eennttrriieess
If an error occurs, ssuuddooeerrss will log a message and, in most cases, send a
message to the administrator via email. Possible errors include:
parse error in /etc/sudoers near line N
ssuuddooeerrss encountered an error when parsing the specified file. In some
cases, the actual error may be one line above or below the line number
listed, depending on the type of error.
problem with defaults entries
The sudoers file contains one or more unknown Defaults settings. This
does not prevent ssuuddoo from running, but the sudoers file should be
checked using vviissuuddoo.
timestamp owner (username): No such user
The time stamp directory owner, as specified by the timestampowner
setting, could not be found in the password database.
unable to open/read /etc/sudoers
The sudoers file could not be opened for reading. This can happen
when the sudoers file is located on a remote file system that maps
user ID 0 to a different value. Normally, ssuuddooeerrss tries to open the
sudoers file using group permissions to avoid this problem. Consider
either changing the ownership of /etc/sudoers or adding an argument
like ``sudoers_uid=N'' (where `N' is the user ID that owns the sudoers
file) to the end of the ssuuddooeerrss Plugin line in the sudo.conf(4) file.
unable to stat /etc/sudoers
The /etc/sudoers file is missing.
/etc/sudoers is not a regular file
The /etc/sudoers file exists but is not a regular file or symbolic
link.
/etc/sudoers is owned by uid N, should be 0
The sudoers file has the wrong owner. If you wish to change the
sudoers file owner, please add ``sudoers_uid=N'' (where `N' is the
user ID that owns the sudoers file) to the ssuuddooeerrss Plugin line in the
sudo.conf(4) file.
/etc/sudoers is world writable
The permissions on the sudoers file allow all users to write to it.
The sudoers file must not be world-writable, the default file mode is
0440 (readable by owner and group, writable by none). The default
mode may be changed via the ``sudoers_mode'' option to the ssuuddooeerrss
Plugin line in the sudo.conf(4) file.
/etc/sudoers is owned by gid N, should be 1
The sudoers file has the wrong group ownership. If you wish to change
the sudoers file group ownership, please add ``sudoers_gid=N'' (where
`N' is the group ID that owns the sudoers file) to the ssuuddooeerrss Plugin
line in the sudo.conf(4) file.
unable to open /var/run/sudo/ts/username
ssuuddooeerrss was unable to read or create the user's time stamp file. This
can happen when timestampowner is set to a user other than root and
the mode on /var/run/sudo is not searchable by group or other. The
default mode for /var/run/sudo is 0711.
unable to write to /var/run/sudo/ts/username
ssuuddooeerrss was unable to write to the user's time stamp file.
/var/run/sudo/ts is owned by uid X, should be Y
The time stamp directory is owned by a user other than timestampowner.
This can occur when the value of timestampowner has been changed.
ssuuddooeerrss will ignore the time stamp directory until the owner is
corrected.
/var/run/sudo/ts is group writable
The time stamp directory is group-writable; it should be writable only
by timestampowner. The default mode for the time stamp directory is
0700. ssuuddooeerrss will ignore the time stamp directory until the mode is
corrected.
NNootteess oonn llooggggiinngg vviiaa ssyysslloogg
By default, ssuuddooeerrss logs messages via syslog(3). The date, hostname, and
progname fields are added by the syslog daemon, not ssuuddooeerrss itself. As
such, they may vary in format on different systems.
On most systems, syslog(3) has a relatively small log buffer. To prevent
the command line arguments from being truncated, ssuuddooeerrss will split up
log messages that are larger than 960 characters (not including the date,
hostname, and the string ``sudo''). When a message is split, additional
parts will include the string ``(command continued)'' after the user name
and before the continued command line arguments.
NNootteess oonn llooggggiinngg ttoo aa ffiillee
If the logfile option is set, ssuuddooeerrss will log to a local file, such as
/var/log/sudo. When logging to a file, ssuuddooeerrss uses a format similar to
syslog(3), with a few important differences:
1. The progname and hostname fields are not present.
2. If the log_year option is enabled, the date will also include the
year.
3. Lines that are longer than loglinelen characters (80 by default) are
word-wrapped and continued on the next line with a four character
indent. This makes entries easier to read for a human being, but
makes it more difficult to use grep(1) on the log files. If the
loglinelen option is set to 0 (or negated with a `!'), word wrap
will be disabled.
II//OO LLOOGG FFIILLEESS
When I/O logging is enabled, ssuuddoo will run the command in a pseudo-tty
and log all user input and/or output. I/O is logged to the directory
specified by the iolog_dir option (/var/log/sudo-io by default) using a
unique session ID that is included in the ssuuddoo log line, prefixed with
``TSID=''. The iolog_file option may be used to control the format of
the session ID.
Each I/O log is stored in a separate directory that contains the
following files:
log a text file containing the time the command was run, the name
of the user who ran ssuuddoo, the name of the target user, the name
of the target group (optional), the terminal that ssuuddoo was run
from, the number of rows and columns of the terminal, the
working directory the command was run from and the path name of
the command itself (with arguments if present)
timing a log of the amount of time between, and the number of bytes
in, each I/O log entry (used for session playback)
ttyin input from the user's tty (what the user types)
stdin input from a pipe or file
ttyout output from the pseudo-tty (what the command writes to the
screen)
stdout standard output to a pipe or redirected to a file
stderr standard error to a pipe or redirected to a file
All files other than log are compressed in gzip format unless the
compress_io option has been disabled. Due to buffering, the I/O log data
will not be complete until the ssuuddoo command has completed. The output
portion of an I/O log file can be viewed with the sudoreplay(1m) utility,
which can also be used to list or search the available logs.
Note that user input may contain sensitive information such as passwords
(even if they are not echoed to the screen), which will be stored in the
log file unencrypted. In most cases, logging the command output via
log_output or LOG_OUTPUT is all that is required.
Since each session's I/O logs are stored in a separate directory,
traditional log rotation utilities cannot be used to limit the number of
I/O logs. The simplest way to limit the number of I/O is by setting the
maxseq option to the maximum number of logs you wish to store. Once the
I/O log sequence number reaches maxseq, it will be reset to zero and
ssuuddooeerrss will truncate and re-use any existing I/O logs.
FFIILLEESS
/etc/sudo.conf Sudo front end configuration
/etc/sudoers List of who can run what
/etc/group Local groups file
/etc/netgroup List of network groups
/var/log/sudo-io I/O log files
/var/run/sudo/ts Directory containing time stamps for the
ssuuddooeerrss security policy
/var/adm/sudo/lectured Directory containing lecture status files for
the ssuuddooeerrss security policy
/etc/environment Initial environment for --ii mode on AIX and
Linux systems
EEXXAAMMPPLLEESS
Below are example sudoers file entries. Admittedly, some of these are a
bit contrived. First, we allow a few environment variables to pass and
then define our aliases:
# 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
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,\
sha224:0GomF8mNN3wlDt1HD9XldjJ3SNgpFdbjO1+NsQ== \
/home/operator/bin/start_backups
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 syslog(3) using the auth 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 SERVERS Host_Alias, we keep an additional local log
file and make sure we log the year in each log line since the log entries
will be kept around for several years. Lastly, we disable shell escapes
for the commands in the PAGERS Cmnd_Alias (/usr/bin/more, /usr/bin/pg and
/usr/bin/less). Note that this will not effectively constrain users with
ssuuddoo AALLLL privileges.
# 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 User specification 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).
jack CSNETS = ALL
The user jjaacckk may run any command on the machines in the CSNETS alias
(the networks 128.138.243.0, 128.138.204.0, and 128.138.242.0). Of those
networks, only 128.138.204.0 has an explicit netmask (in CIDR notation)
indicating it is a class C network. For the other networks in CSNETS,
the local machine's netmask will be used during matching.
lisa CUNETS = ALL
The user lliissaa may run any command on any host in the CUNETS alias (the
class B network 128.138.0.0).
operator ALL = DUMPS, KILL, SHUTDOWN, HALT, REBOOT, PRINTING,\
sudoedit /etc/printcap, /usr/oper/bin/
The 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
/usr/oper/bin/. Note that one command in the DUMPS Cmnd_Alias includes a
sha224 digest, /home/operator/bin/start_backups. This is because the
directory containing the script is writable by the operator user. If the
script is modified (resulting in a digest mismatch) it will no longer be
possible to run it via ssuuddoo.
joe ALL = /usr/bin/su operator
The user jjooee may only su(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 /usr/sbin/ as themselves
with any group in the ADMINGRP Runas_Alias (the aaddmm and ooppeerr groups).
The user ppeettee is allowed to change anyone's password except for root on
the HPPA machines. Because command line arguments are matched as a
single, concatenated string, the `*' wildcard will match multiple words.
This example assumes that passwd(1) does not take multiple user names on
the command line. Note that on GNU systems, options to passwd(1) may be
specified after the user argument. As a result, this rule will also
allow:
passwd username --expire
which may not be desirable.
bob SPARC = (OP) ALL : SGI = (OP) ALL
The user bboobb may run anything on the SPARC and SGI machines as any user
listed in the OP Runas_Alias (rroooott and ooppeerraattoorr.)
jim +biglab = ALL
The user jjiimm may run any command on machines in the biglab 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 DB Runas_Alias (oorraaccllee
or ssyybbaassee) without giving a password.
john ALPHA = /usr/bin/su [!-]*, !/usr/bin/su *root*
On the ALPHA machines, user jjoohhnn may su to anyone except root but he is
not allowed to specify any options to the su(1) command.
jen ALL, !SERVERS = ALL
The user jjeenn may run any command on any machine except for those in the
SERVERS Host_Alias (master, mail, www and ns).
jill SERVERS = /usr/bin/, !SU, !SHELLS
For any machine in the SERVERS Host_Alias, jjiillll may run any commands in
the directory /usr/bin/ except for those commands belonging to the SU and
SHELLS Cmnd_Aliases. While not specifically mentioned in the rule, the
commands in the PAGERS Cmnd_Alias all reside in /usr/bin and have the
noexec option set.
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 WEBMASTERS User_Alias (will, wendy, and
wim), may run any command as user www (which owns the web pages) or
simply su(1) to www.
ALL CDROM = NOPASSWD: /sbin/umount /CDROM,\
/sbin/mount -o nosuid\,nodev /dev/cd0a /CDROM
Any user may mount or unmount a CD-ROM on the machines in the CDROM
Host_Alias (orion, perseus, hercules) without entering a password. This
is a bit tedious for users to type, so it is a prime candidate for
encapsulating in a shell script.
SSEECCUURRIITTYY NNOOTTEESS
LLiimmiittaattiioonnss ooff tthhee ``!!'' ooppeerraattoorr
It is generally not effective to ``subtract'' commands from AALLLL 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 SU or
SHELLS since he can simply copy those commands to a different name, or
use a shell escape from an editor or other program. Therefore, these
kind of restrictions should be considered advisory at best (and
reinforced by policy).
In general, if a user has sudo AALLLL there is nothing to prevent them from
creating their own program that gives them a root shell (or making their
own copy of a shell) regardless of any `!' elements in the user
specification.
SSeeccuurriittyy iimmpplliiccaattiioonnss ooff fast_glob
If the fast_glob 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 fnmatch(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 sudoers file 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 fast_glob is enabled by
changing to /usr/bin 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 is 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 noexec 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.
The noexec feature is known to work on SunOS, Solaris, *BSD,
Linux, IRIX, Tru64 UNIX, MacOS X, HP-UX 11.x and AIX 5.3 and
above. It should be supported 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.
On Solaris 10 and higher, noexec uses Solaris privileges
instead of the LD_PRELOAD environment variable.
To enable noexec for a command, use the NOEXEC tag as
documented in the User Specification section above. Here is
that example again:
aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
This allows user aaaarroonn to run /usr/bin/more and /usr/bin/vi
with noexec enabled. This will prevent those two commands from
executing other commands (such as a shell). If you are unsure
whether or not your system is capable of supporting noexec you
can always just try it out and check whether shell escapes work
when noexec is enabled.
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 (see below).
SSeeccuurree eeddiittiinngg
The ssuuddooeerrss plugin includes ssuuddooeeddiitt support which allows users to
securely edit files with the editor of their choice. As ssuuddooeeddiitt is a
built-in command, it must be specified in the sudoers file without a
leading path. However, it may take command line arguments just as a
normal command does. Wildcards used in sudoedit command line arguments
are expected to be path names, so a forward slash (`/') will not be
matched by a wildcard.
Unlike other ssuuddoo commands, the editor is run with the permissions of the
invoking user and with the environment unmodified. More information may
be found in the description of the --ee option in sudo(1m).
For example, to allow user operator to edit the ``message of the day''
file:
operator sudoedit /etc/motd
The operator user then runs ssuuddooeeddiitt as follows:
$ sudoedit /etc/motd
The editor will run as the operator user, not root, on a temporary copy
of /etc/motd. After the file has been edited, /etc/motd will be updated
with the contents of the temporary copy.
Users should never be granted ssuuddooeeddiitt permission to edit a file that
resides in a directory the user has write access to, either directly or
via a wildcard. If the user has write access to the directory it is
possible to replace the legitimate file with a link to another file,
allowing the editing of arbitrary files. To prevent this, starting with
version 1.8.16, symbolic links will not be followed in writable
directories and ssuuddooeeddiitt will refuse to edit a file located in a writable
directory unless the sudoedit_checkdir option has been disabled or the
invoking user is root. Additionally, in version 1.8.15 and higher,
ssuuddooeeddiitt will refuse to open a symbolic link unless either the
sudoedit_follow option is enabled or the sudoedit command is prefixed
with the FOLLOW tag in the sudoers file.
TTiimmee ssttaammpp ffiillee cchheecckkss
ssuuddooeerrss will check the ownership of its time stamp directory
(/var/run/sudo/ts by default) and ignore the directory's contents if it
is not owned by root or if it is writable by a user other than root.
Older versions of ssuuddoo stored time stamp files in /tmp; this is no longer
recommended as it may be possible for a user to create the time stamp
themselves on systems that allow unprivileged users to change the
ownership of files they create.
While the time stamp directory should be cleared at reboot time, not all
systems contain a /var/run directory. To avoid potential problems,
ssuuddooeerrss will ignore time stamp files that date from before the machine
booted on systems where the boot time is available.
Some systems with graphical desktop environments allow unprivileged users
to change the system clock. Since ssuuddooeerrss relies on the system clock for
time stamp validation, it may be possible on such systems for a user to
run ssuuddoo for longer than timestamp_timeout by setting the clock back. To
combat this, ssuuddooeerrss uses a monotonic clock (which never moves backwards)
for its time stamps if the system supports it.
ssuuddooeerrss will not honor time stamps set far in the future. Time stamps
with a date greater than current_time + 2 * TIMEOUT will be ignored and
ssuuddooeerrss will log and complain.
Since time stamp files live in the file system, they can outlive a user's
login session. As a result, a user may be able to login, run a command
with ssuuddoo after authenticating, logout, login again, and run ssuuddoo without
authenticating so long as the record's time stamp is within 5 minutes (or
whatever value the timeout is set to in the sudoers file). When the
tty_tickets option is enabled, the time stamp record includes the device
number of the terminal the user authenticated with. This provides per-
tty granularity but time stamp records still may outlive the user's
session. The time stamp record also includes the session ID of the
process that last authenticated. This prevents processes in different
terminal sessions from using the same time stamp record. It also helps
reduce the chance that a user will be able to run ssuuddoo without entering a
password when logging out and back in again on the same terminal.
DDEEBBUUGGGGIINNGG
Versions 1.8.4 and higher of the ssuuddooeerrss plugin support a flexible
debugging framework that can help track down what the plugin is doing
internally if there is a problem. This can be configured in the
sudo.conf(4) file.
The ssuuddooeerrss plugin uses the same debug flag format as the ssuuddoo front-end:
subsystem@priority.
The priorities used by ssuuddooeerrss, in order of decreasing severity, are:
crit, err, warn, notice, diag, info, trace and debug. Each priority,
when specified, also includes all priorities higher than it. For
example, a priority of notice would include debug messages logged at
notice and higher.
The following subsystems are used by the ssuuddooeerrss plugin:
alias User_Alias, Runas_Alias, Host_Alias and Cmnd_Alias processing
all matches every subsystem
audit BSM and Linux audit code
auth user authentication
defaults sudoers file Defaults settings
env environment handling
ldap LDAP-based sudoers
logging logging support
match matching of users, groups, hosts and netgroups in the sudoers
file
netif network interface handling
nss network service switch handling in ssuuddooeerrss
parser sudoers file parsing
perms permission setting
plugin The equivalent of main for the plugin.
pty pseudo-tty related code
rbtree redblack tree internals
sssd SSSD-based sudoers
util utility functions
For example:
Debug sudo /var/log/sudo_debug match@info,nss@info
For more information, see the sudo.conf(4) manual.
SSEEEE AALLSSOO
ssh(1), su(1), fnmatch(3), glob(3), mktemp(3), strftime(3), sudo.conf(4),
sudoers.ldap(4), sudo(1m), sudo_plugin(1m), visudo(1m)
AAUUTTHHOORRSS
Many people have worked on ssuuddoo over the years; this version consists of
code written primarily by:
Todd C. Miller
See the CONTRIBUTORS file in the ssuuddoo distribution
(https://www.sudo.ws/contributors.html) for an exhaustive list of people
who have contributed to ssuuddoo.
CCAAVVEEAATTSS
The sudoers file should aallwwaayyss be edited by the vviissuuddoo command which
locks the file and does grammatical checking. It is imperative that the
sudoers file be free of syntax errors since ssuuddoo will not run with a
syntactically incorrect sudoers 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 fqdn option in sudoers.
BBUUGGSS
If you feel you have found a bug in ssuuddoo, please submit a bug report at
https://bugzilla.sudo.ws/
SSUUPPPPOORRTT
Limited free support is available via the sudo-users mailing list, see
https://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search
the archives.
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 https://www.sudo.ws/license.html for
complete details.
Sudo 1.8.17 January 20, 2016 Sudo 1.8.17