Manual Pages for UNIX Darwin command on man sudoers

SUDOERS(5) MAINTENANCE COMMANDS SUDOERS(5)

NAME

sudoers - list of which users may execute what

DESCRIPTION

The sudoers file is composed of two types of entries: aliases (basi-

cally variables) and user specifications (which specify who may run what). When multiple entries match for a user, they are applied in order. Where there are conflicting values, the last match is used (which is not necessarily the most specific match).

The sudoers grammar will be described below in Extended Backus-Naur

Form (EBNF). Don't despair if you don't know what EBNF is; it is fairly simple, and the definitions below are annotated. QQuuiicckk gguuiiddee ttoo EEBBNNFF

EBNF is a concise and exact way of describing the grammar of a lan-

guage. 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, con-

fuse them with "wildcard" characters, which have different meanings. ? Means that the preceding symbol (or group of symbols) is optional. That is, it may appear once or not at all. * Means that the preceding symbol (or group of symbols) may appear zero or more times. + Means that the preceding symbol (or group of symbols) may appear one or more times. Parentheses may be used to group symbols together. For clarity, we will use single quotes ('') to designate what is a verbatim character string (as opposed to a symbol name). AAlliiaasseess There are four kinds of aliases: UserAlias, RunasAlias, HostAlias and CmndAlias. Alias ::= 'UserAlias' UserAlias (':' UserAlias)* | 'RunasAlias' RunasAlias (':' RunasAlias)* | 'HostAlias' HostAlias (':' HostAlias)* | 'CmndAlias' CmndAlias (':' CmndAlias)*

UserAlias ::= NAME '=' UserList

RunasAlias ::= NAME '=' RunasList

HostAlias ::= NAME '=' HostList

CmndAlias ::= NAME '=' CmndList

NAME ::= [A-Z]([A-Z][0-9])*

Each alias definition is of the form

AliasType NAME = item1, item2, ...

where AliasType is one of UserAlias, RunasAlias, HostAlias, or

CmndAlias. A NAME is a string of uppercase letters, numbers, and

underscore characters (''). A NAME mmuusstt start with an uppercase let-

ter. It is possible to put several alias definitions of the same type on a single line, joined by a colon (':'). E.g.,

AliasType NAME = item1, item2, item3 : NAME = item4, item5

The definitions of what constitutes a valid alias member follow. UserList ::= User | User ',' UserList User ::= '!'* username |

'!'* '%'group |

'!'* '+'netgroup | '!'* UserAlias

A UserList is made up of one or more usernames, system groups (pre-

fixed with '%'), netgroups (prefixed with '+') and other aliases. Each

list item may be prefixed with one or more '!' operators. An odd num-

ber of '!' operators negate the value of the item; an even number just cancel each other out. RunasList ::= RunasUser | RunasUser ',' RunasList RunasUser ::= '!'* username |

'!'* '#'uid |

'!'* '%'group |

'!'* +netgroup | '!'* RunasAlias A RunasList is similar to a UserList except that it can also contain

uids (prefixed with '#') and instead of UserAliases it can contain

RunasAliases. Note that usernames and groups are matched as strings.

In other words, two users (groups) with the same uid (gid) are consid-

ered to be distinct. If you wish to match all usernames with the same

uid (e.g. root and toor), you can use a uid instead (#0 in the example

given). HostList ::= Host | Host ',' HostList Host ::= '!'* hostname | '!'* ipaddr | '!'* network(/netmask)? | '!'* '+'netgroup | '!'* HostAlias A HostList is made up of one or more hostnames, IP addresses, network numbers, netgroups (prefixed with '+') and other aliases. Again, the value of an item may be negated with the '!' operator. If you do not

specify a netmask with a network number, the netmask of the host's eth-

ernet interface(s) will be used when matching. The netmask may be specified either in dotted quad notation (e.g. 255.255.255.0) or CIDR

notation (number of bits, e.g. 24). A hostname may include shell-style

wildcards (see the Wildcards section below), but unless the hostname command on your machine returns the fully qualified hostname, you'll need to use the fqdn option for wildcards to be useful. CmndList ::= Cmnd | Cmnd ',' CmndList commandname ::= filename | filename args | filename '""' Cmnd ::= '!'* commandname | '!'* directory | '!'* "sudoedit" | '!'* CmndAlias A CmndList is a list of one or more commandnames, directories, and other aliases. A commandname is a fully qualified filename which may

include shell-style wildcards (see the Wildcards section below). A

simple filename allows the user to run the command with any arguments he/she wishes. However, you may also specify command line arguments (including wildcards). Alternately, you can specify "" to indicate that the command may only be run wwiitthhoouutt command line arguments. A directory is a fully qualified pathname ending in a '/'. When you specify a directory in a CmndList, the user will be able to run any file within that directory (but not in any subdirectories therein). If a Cmnd has associated command line arguments, then the arguments in the Cmnd must match exactly those given by the user on the command line (or match the wildcards if there are any). Note that the following

characters must be escaped with a '\' if they are used in command argu-

ments: ',', ':', '=', '\'. The special command "sudoedit" is used to

permit a user to run ssuuddoo with the -ee flag (or as ssuuddooeeddiitt). It may

take command line arguments just as a normal command does. DDeeffaauullttss Certain configuration options may be changed from their default values at runtime via one or more DefaultEntry lines. These may affect all users on any host, all users on a specific host, a specific user, or commands being run as a specific user. DefaultType ::= 'Defaults' | 'Defaults' '@' Host | 'Defaults' ':' User | 'Defaults' '>' RunasUser DefaultEntry ::= DefaultType ParameterList ParameterList ::= Parameter | Parameter ',' ParameterList 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 con-

text 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 oper-

ators are used to add to and delete from a list respectively. It is

not an error to use the -= operator to remove an element that does not

exist in a list. FFllaaggss: longotpprompt When validating with a One Time Password scheme (SS//KKeeyy or

OOPPIIEE), a two-line prompt is used to make it easier to cut

and paste the challenge to a local window. It's not as

pretty as the default but some people find it more conve-

nient. This flag is off by default. ignoredot If set, ssuuddoo will ignore '.' or '' (current dir) in the PATH environment variable; the PATH itself is not modified.

This flag is off by default. Currently, while it is possi-

ble to set ignoredot in sudoers, its value is not used.

This option should be considered read-only (it will be

fixed in a future version of ssuuddoo). mailalways Send mail to the mailto user every time a users runs ssuuddoo. This flag is off by default. mailbadpass Send mail to the mailto user if the user running sudo does not enter the correct password. This flag is off by default. mailnouser

If set, mail will be sent to the mailto user if the invok-

ing user is not in the sudoers file. This flag is on by

default. mailnohost

If set, mail will be sent to the mailto user if the invok-

ing user exists in the sudoers file, but is not allowed to

run commands on the current host. This flag is off by default. mailnoperms

If set, mail will be sent to the mailto user if the invok-

ing 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.

ttytickets If set, users must authenticate on a per-tty basis. Nor-

mally, ssuuddoo uses a directory in the ticket dir with the same name as the user running it. With this flag enabled, ssuuddoo will use a file named for the tty the user is logged in on in that directory. This flag is off by default. authenticate If set, users must authenticate themselves via a password

(or other means of authentication) before they may run com-

mands. This default may be overridden via the PASSWD and NOPASSWD tags. This flag is on by default. rootsudo 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 rootsudo will also prevent root and from running ssuuddooeeddiitt. Disabling rootsudo provides no real additional security; it exists purely for historical reasons. This flag is on by default.

loghost If set, the hostname will be logged in the (non-syslog)

ssuuddoo log file. This flag is off by default.

logyear If set, the four-digit year will be logged in the (non-sys-

log) ssuuddoo log file. This flag is off by default. shellnoargs If set and ssuuddoo is invoked with no arguments it acts as if

the -ss flag had been given. That is, it runs a shell as

root (the shell is determined by the SHELL environment variable if it is set, falling back on the shell listed in the invoking user's /etc/passwd entry if not). This flag is off by default.

sethome If set and ssuuddoo is invoked with the -ss flag the HOME envi-

ronment variable will be set to the home directory of the

target user (which is root unless the -uu option is used).

This effectively makes the -ss flag imply -HH. This flag is

off by default. alwayssethome If set, ssuuddoo will set the HOME environment variable to the home directory of the target user (which is root unless the

-uu option is used). This effectively means that the -HH

flag is always implied. This flag is off by default. pathinfo 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 off by default. preservegroups By default ssuuddoo will initialize the group vector to the list of groups the target user is in. When preservegroups 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. fqdn Set this flag if you want to put fully qualified hostnames

in the sudoers file. I.e., instead of myhost you would use

myhost.mydomain.edu. You may still use the short form if you wish (and even mix the two). Beware that turning on fqdn requires ssuuddoo to make DNS lookups which may make ssuuddoo unusable if DNS stops working (for example if the machine is not plugged into the network). Also note that you must use the host's official name as DNS knows it. That is, you

may not use a host alias (CNAME entry) due to performance

issues and the fact that there is no way to get all aliases from DNS. If your machine's hostname (as returned by the hostname command) is already fully qualified you shouldn't need to set fqdn. 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. requiretty If set, ssuuddoo will only run when the user is logged in to a real tty. This will disallow things like "rsh somehost sudo ls" since rsh(1) does not allocate a tty. Because it is not possible to turn off echo when there is no tty present, some sites may wish to set this flag to prevent a user from entering a visible password. This flag is off by default. enveditor If set, vviissuuddoo will use the value of the EDITOR or VISUAL environment variables before falling back on the default editor list. Note that this may create a security hole as it allows the user to run any arbitrary command as root

without logging. A safer alternative is to place a colon-

separated list of editors in the editor variable. vviissuuddoo will then only use the EDITOR or VISUAL if they match a value specified in editor. This flag is on by default. rootpw If set, ssuuddoo will prompt for the root password instead of the password of the invoking user. This flag is off by default. runaspw If set, ssuuddoo will prompt for the password of the user defined by the runasdefault option (defaults to root) instead of the password of the invoking user. This flag is off by default.

targetpw If set, ssuuddoo will prompt for the password of the user spec-

ified by the -uu flag (defaults to root) instead of the

password of the invoking user. Note that this precludes the use of a uid not listed in the passwd database as an

argument to the -uu flag. This flag is off by default.

setlogname Normally, ssuuddoo will set the LOGNAME and USER environment

variables to the name of the target user (usually root

unless the -uu flag 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 desir-

able to change this behavior. This can be done by negating the setlogname option.

staysetuid Normally, when ssuuddoo executes a command the real and effec-

tive 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 functional-

ity when a program is run setuid. Note, however, that this means that sudo will run with the real uid of the invoking user which may allow that user to kill ssuuddoo before it can

log a failure, depending on how your OS defines the inter-

action between signals and setuid processes. envreset If set, ssuuddoo will reset the environment to only contain the

following variables: HOME, LOGNAME, PATH, SHELL, TERM, and

USER (in addition to the SUDO* variables). Of these, only TERM is copied unaltered from the old environment. The

other variables are set to default values (possibly modi-

fied by the value of the setlogname option). If ssuuddoo was compiled with the SECUREPATH option, its value will be used for the PATH environment variable. Other variables may be preserved with the envkeep option. useloginclass

If set, ssuuddoo will apply the defaults specified for the tar-

get user's login class if one exists. Only available if

ssuuddoo is configured with the -with-logincap option. This

flag is off by default. noexec If set, all commands run via sudo will behave as if the NOEXEC tag has been set, unless overridden by a EXEC tag. See the description of NOEXEC and EXEC below as well as the

"PREVENTING SHELL ESCAPES" section at the end of this man-

ual. This flag is off by default.

ignorelocalsudoers

If set via LDAP, parsing of @sysconfdir@/sudoers will be

skipped. This is intended for an Enterprises that wish to

prevent the usage of local sudoers files so that only LDAP

is used. This thwarts the efforts of rogue operators who

would attempt to add roles to @sysconfdir@/sudoers. When

this option is present, @sysconfdir@/sudoers does not even

need to exist. Since this options tells sudo how to behave when no specific LDAP entries have been matched, this sudoOption is only meaningful for the cn=defaults section. This flag is off by default. IInntteeggeerrss: passwdtries 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 dis-

able word wrap). timestamptimeout Number of minutes that can elapse before ssuuddoo will ask for a passwd again. The default is 5. Set this to 0 to always prompt for a password. If set to a value less than 0 the user's timestamp will never expire. This can be used to allow users to create or delete their own timestamps via

sudo -v and sudo -k respectively.

passwdtimeout Number of minutes before the ssuuddoo password prompt times

out. The default is 0, set this to 0 for no password time-

out. umask Umask to use when running the command. Negate this option or set it to 0777 to preserve the user's umask. The default is 0022. SSttrriinnggss:

mailsub Subject of the mail sent to the mailto user. The escape %h

will expand to the hostname of the machine. Default is ***

SECURITY information for %h ***.

badpassmessage Message that is displayed if a user enters an incorrect password. The default is Sorry, try again. unless insults are enabled. timestampdir The directory in which ssuuddoo stores its timestamp files. The default is /var/db/sudo. timestampowner The owner of the timestamp directory and the timestamps stored therein. The default is root. passprompt The default prompt to use when asking for a password; can

be overridden via the -pp option or the SUDOPROMPT environ-

ment variable. The following percent (`%') escapes are

supported:

%u expanded to the invoking user's login name

%U expanded to the login name of the user the command

will be run as (defaults to root)

%h expanded to the local hostname without the domain

name

%H expanded to the local hostname including the domain

name (on if the machine's hostname is fully quali-

fied or the fqdn option is set)

%% two consecutive % characters are collaped into a

single % character

The default value is Password:. runasdefault

The default user to run commands as if the -uu flag is not

specified on the command line. This defaults to root. Note that if runasdefault is set it mmuusstt occur before any RunasAlias specifications. sysloggoodpri

Syslog priority to use when user authenticates success-

fully. Defaults to notice. syslogbadpri

Syslog priority to use when user authenticates unsuccess-

fully. Defaults to alert. editor A colon (':') separated list of editors allowed to be used with vviissuuddoo. vviissuuddoo will choose the editor that matches the user's USER environment variable if possible, or the first editor in the list that exists and is executable. The default is the path to vi on your system. noexecfile Path to a shared library containing dummy versions of the execv(), execve() and fexecve() library functions that just return an error. This is used to implement the noexec functionality on systems that support LDPRELOAD or its equivalent. Defaults to . SSttrriinnggss tthhaatt ccaann bbee uusseedd iinn aa bboooolleeaann ccoonntteexxtt: lecture This option controls when a short lecture will be printed

along with the password prompt. It has the following pos-

sible values: never Never lecture the user. once Only lecture the user the first time they run ssuuddoo. always Always lecture the user. If no value is specified, a value of once is implied. Negating the option results in a value of never being used. The default value is once. lecturefile Path to a file containing an alternate sudo lecture that will be used in place of the standard lecture if the named file exists.

logfile Path to the ssuuddoo log file (not the syslog log file). Set-

ting a path turns on logging to a file; negating this option turns it off. syslog Syslog facility if syslog is being used for logging (negate to disable syslog logging). Defaults to local2. mailerpath Path to mail program used to send warning mail. Defaults to the path to sendmail found at configure time.

mailerflags Flags to use when invoking mailer. Defaults to -tt.

mailto Address to send warning and error mail to. The address should be enclosed in double quotes (") to protect against sudo interpreting the @ sign. Defaults to root. exemptgroup Users in this group are exempt from password and PATH requirements. This is not set by default. verifypw This option controls when a password will be required when

a user runs ssuuddoo with the -vv flag. It has the following

possible values:

all All the user's sudoers entries for the current host

must have the NOPASSWD flag set to avoid entering a password.

any At least one of the user's sudoers entries for the

current host must have the NOPASSWD flag set to avoid entering a password.

never The user need never enter a password to use the -vv

flag.

always The user must always enter a password to use the -vv

flag. 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. listpw This option controls when a password will be required when

a user runs ssuuddoo with the -ll flag. It has the following

possible values:

all All the user's sudoers entries for the current host

must have the NOPASSWD flag set to avoid entering a password.

any At least one of the user's sudoers entries for the

current host must have the NOPASSWD flag set to avoid entering a password.

never The user need never enter a password to use the -ll

flag.

always The user must always enter a password to use the -ll

flag. 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. LLiissttss tthhaatt ccaann bbee uusseedd iinn aa bboooolleeaann ccoonntteexxtt:

envcheck Environment variables to be removed from the user's envi-

ronment if the variable's value contains % or / characters.

This can be used to guard against printf-style format vul-

nerabilities in poorly-written programs. The argument may

be a double-quoted, space-separated list or a single value

without double-quotes. The list can be replaced, added to,

deleted from, or disabled by using the =, +=, -=, and !

operators respectively. The default list of environment variables to check is printed when ssuuddoo is run by root with

the -V option.

envdelete Environment variables to be removed from the user's envi-

ronment. The argument may be a double-quoted, space-sepa-

rated list or a single value without double-quotes. The

list can be replaced, added to, deleted from, or disabled

by using the =, +=, -=, and ! operators respectively. The

default list of environment variables to remove is printed

when ssuuddoo is run by root with the -V option. Note that

many operating systems will remove potentially dangerous variables from the environment of any setuid process (such as ssuuddoo).

envkeep Environment variables to be preserved in the user's envi-

ronment when the envreset 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 with-

out double-quotes. The list can be replaced, added to,

deleted from, or disabled by using the =, +=, -=, and !

operators respectively. This list has no default members. When logging via syslog(3), ssuuddoo accepts the following values for the syslog facility (the value of the ssyysslloogg Parameter): aauutthhpprriivv (if your OS supports it), aauutthh, ddaaeemmoonn, uusseerr, llooccaall00, llooccaall11, llooccaall22, llooccaall33, llooccaall44, llooccaall55, llooccaall66, and llooccaall77. The following syslog priorities

are supported: aalleerrtt, ccrriitt, ddeebbuugg, eemmeerrgg, eerrrr, iinnffoo, nnoottiiccee, and wwaarrnn-

iinngg. UUsseerr SSppeecciiffiiccaattiioonn UserSpec ::= UserList HostList '=' CmndSpecList \ (':' HostList '=' CmndSpecList)* CmndSpecList ::= CmndSpec | CmndSpec ',' CmndSpecList CmndSpec ::= RunasSpec? TagSpec* Cmnd RunasSpec ::= '(' RunasList ')' TagSpec ::= ('NOPASSWD:' | 'PASSWD:' | 'NOEXEC:' | 'EXEC:') A uusseerr ssppeecciiffiiccaattiioonn determines which commands a user may run (and as what user) on specified hosts. By default, commands are run as rroooott,

but this can be changed on a per-command basis.

Let's break that down into its constituent parts: RRuunnaassSSppeecc A RunasSpec is simply a RunasList (as defined above) enclosed in a set of parentheses. If you do not specify a RunasSpec in the user specification, a default RunasSpec of rroooott will be used. A RunasSpec sets the default for commands that follow it. What this means is that for the entry: dgb boulder = (operator) /bin/ls, /bin/kill, /usr/bin/lprm

The user ddggbb may run /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 RunasSpec 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. TTaaggSSppeecc A command may have zero or more tags associated with it. There are four possible tag values, NOPASSWD, PASSWD, NOEXEC, EXEC. Once a tag is set on a Cmnd, subsequent Cmnds in the CmndSpecList, inherit the tag unless it is overridden by the opposite tag (ie: PASSWD overrides NOPASSWD and EXEC overrides NOEXEC). NOPASSWD and PASSWD 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 RunasSpec, the NOPASSWD tag sets a default for the commands that follow it in the CmndSpecList. 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 root on the machine rushmore as rroooott 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 exemptgroup 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 pass-

word if the NOPASSWD tag is present for all a user's entries that per-

tain to the current host. This behavior may be overridden via the ver-

ifypw and listpw options. NOEXEC and EXEC

If sudo has been compiled with noexec support and the underlying oper-

ating system support it, the NOEXEC tag can be used to prevent a dynam-

ically-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. WWiillddccaarrddss

ssuuddoo allows shell-style wildcards (aka meta or glob characters) to be

used in pathnames as well as command line arguments in the sudoers

file. Wildcard matching is done via the PPOOSSIIXX fnmatch(3) routine. Note that these are not regular expressions. * Matches any set of zero or more characters. ? Matches any single character. [...] Matches any character in the specified range. [!...] Matches any character nnoott in the specified range. \x For any character "x", evaluates to "x". This is used to escape special characters such as: "*", "?", "[", and "}". Note that a forward slash ('/') will nnoott be matched by wildcards used in the pathname. When matching the command line arguments, however, a slash ddooeess get matched by wildcards. This is to make a path like: /usr/bin/* match /usr/bin/who but not /usr/bin/X11/xterm. WARNING: a pathname with wildcards will nnoott match a user command that

consists of a relative path. In other words, given the following sudo-

ers entry: billy workstation = /usr/bin/* user billy will be able to run any command in /usr/bin as root, such as /usr/bin/w. The following two command will be allowed (the first assumes that /usr/bin is in the user's path):

$ sudo w

$ sudo /usr/bin/w

However, this will not:

$ cd /usr/bin

$ sudo ./w

For this reason you should only ggrraanntt access to commands using wild-

cards and never rreessttrriicctt access using them. This limitation will be removed in a future version of ssuuddoo. EExxcceeppttiioonnss ttoo wwiillddccaarrdd rruulleess The following exceptions apply to the above rules: "" If the empty string "" is the only command line argument in the

sudoers entry it means that command is not allowed to be run

with aannyy arguments. OOtthheerr ssppeecciiaall cchhaarraacctteerrss aanndd rreesseerrvveedd wwoorrddss

The pound sign ('#') is used to indicate a comment (unless it occurs in

the context of a user name and is followed by one or more digits, in which case it is treated as a uid). Both the comment character and any text after it, up to the end of the line, are ignored.

The reserved word AALLLL is a built-in alias that always causes a match to

succeed. It can be used wherever one might otherwise use a CmndAlias, UserAlias, RunasAlias, or HostAlias. You should not try to define

your own alias called AALLLL as the built-in alias will be used in prefer-

ence to your own. Please note that using AALLLL can be dangerous since in a command context, it allows the user to run aannyy command on the system. An exclamation point ('!') can be used as a logical not operator both in an alias and in front of a Cmnd. This allows one to exclude certain

values. Note, however, that using a ! in conjunction with the built-in

ALL alias to allow a user to run "all but a few" commands rarely works

as intended (see SECURITY NOTES below).

Long lines can be continued with a backslash ('\') as the last charac-

ter on the line. Whitespace between elements in a list as well as special syntactic characters in a User Specification ('=', ':', '(', ')') is optional. The following characters must be escaped with a backslash ('\') when used as part of a word (e.g. a username or hostname): '@', '!', '=', ':', ',', '(', ')', '\'. FILES

/private/etc/sudoers List of who can run what

/etc/group Local groups file /etc/netgroup List of network groups EEXXAAMMPPLLEESS

Since the sudoers file is parsed in a single pass, order is important.

In general, you should structure sudoers such that the HostAlias,

UserAlias, and CmndAlias specifications come first, followed by any

DefaultEntry lines, and finally the RunasAlias and user specifica-

tions. The basic rule of thumb is you cannot reference an Alias that has not already been defined.

Below are example sudoers entries. Admittedly, some of these are a bit

contrived. First, we define our aliases:

# User alias specification

UserAlias FULLTIMERS = millert, mikef, dowdy UserAlias PARTTIMERS = bostley, jwfox, crawl UserAlias WEBMASTERS = will, wendy, wim

# Runas alias specification

RunasAlias OP = root, operator RunasAlias DB = oracle, sybase

# Host alias specification

HostAlias SPARC = bigtime, eclipse, moet, anchor :\ SGI = grolsch, dandelion, black :\ ALPHA = widget, thalamus, foobar :\ HPPA = boa, nag, python HostAlias CUNETS = 128.138.0.0/255.255.0.0 HostAlias CSNETS = 128.138.243.0, 128.138.204.0/24, 128.138.242.0 HostAlias SERVERS = master, mail, www, ns HostAlias CDROM = orion, perseus, hercules

# Cmnd alias specification

CmndAlias DUMPS = /usr/bin/mt, /usr/sbin/dump, /usr/sbin/rdump,\ /usr/sbin/restore, /usr/sbin/rrestore CmndAlias KILL = /usr/bin/kill CmndAlias PRINTING = /usr/sbin/lpc, /usr/bin/lprm CmndAlias SHUTDOWN = /usr/sbin/shutdown CmndAlias HALT = /usr/sbin/halt CmndAlias REBOOT = /usr/sbin/reboot CmndAlias SHELLS = /usr/bin/sh, /usr/bin/csh, /usr/bin/ksh, \ /usr/local/bin/tcsh, /usr/bin/rsh, \ /usr/local/bin/zsh CmndAlias SU = /usr/bin/su 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 or

USER environment variables when running commands as root. Addition-

ally, on the machines in the SERVERS HostAlias, we keep an additional local log file and make sure we log the year in each log line since the log entries will be kept around for several years.

# Override built-in defaults

Defaults syslog=auth Defaults>root !setlogname Defaults:FULLTIMERS !lecture Defaults:millert !authenticate Defaults@SERVERS logyear, logfile=/var/log/sudo.log 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/. joe ALL = /usr/bin/su operator The user jjooee may only su(1) to operator.

pete HPPA = /usr/bin/passwd [A-z]*, !/usr/bin/passwd root

The user ppeettee is allowed to change anyone's password except for root on

the HPPA machines. Note that this assumes passwd(1) does not take mul-

tiple usernames on the command line. 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 RunasAlias (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 RunasAlias (oorraa-

ccllee 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 give su(1) any flags. jen ALL, !SERVERS = ALL The user jjeenn may run any command on any machine except for those in the SERVERS HostAlias (master, mail, www and ns). jill SERVERS = /usr/bin/, !SU, !SHELLS For any machine in the SERVERS HostAlias, jjiillll may run any commands in the directory /usr/bin/ except for those commands belonging to the SU and SHELLS CmndAliases. steve CSNETS = (operator) /usr/local/opcommands/

The user sstteevvee may run any command in the directory /usr/local/opcom-

mands/ 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 UserAlias (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

HostAlias (orion, perseus, hercules) without entering a password. This is a bit tedious for users to type, so it is a prime candidate for encapsulating in a shell script. SSEECCUURRIITTYY NNOOTTEESS It is generally not effective to "subtract" commands from ALL using the '!' operator. A user can trivially circumvent this by copying the

desired command to a different name and then executing that. For exam-

ple: 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 rein-

forced by policy). PPRREEVVEENNTTIINNGG SSHHEELLLL EESSCCAAPPEESS Once ssuuddoo executes a program, that program is free to do whatever it pleases, including run other programs. This can be a security issue since it is not uncommon for a program to allow shell escapes, which lets a user bypass ssuuddoo's restrictions. Common programs that permit shell escapes include shells (obviously), editors, paginators, mail and terminal programs. Many systems that support shared libraries have the ability to override default library functions by pointing an environment variable (usually LDPRELOAD) to an alternate shared library. On such systems, ssuuddoo's noexec functionality can be used to prevent a program run by sudo from executing any other programs. Note, however, that this applies only to

native dynamically-linked executables. Statically-linked executables

and foreign executables running under binary emulation are not affected. To tell whether or not ssuuddoo supports noexec, you can run the following as root:

sudo -V | grep "dummy exec"

If the resulting output contains a line that begins with: File containing dummy exec functions: then ssuuddoo may be able to replace the exec family of functions in the

standard library with its own that simply return an error. Unfortu-

nately, there is no foolproof way to know whether or not noexec will

work at compile-time. Noexec should work on SunOS, Solaris, *BSD,

Linux, IRIX, Tru64 UNIX, MacOS X, and HP-UX 11.x. It is known nnoott to

work on AIX and UnixWare. Noexec is expected to work on most operating systems that support the LDPRELOAD 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 LDPRELOAD is sup-

ported. 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 sys-

tem is capable of supporting noexec you can always just try it out and see if it works. Note that disabling 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.

The sudoers file should aallwwaayyss be edited by the vviissuuddoo command which

locks the file and does grammatical checking. It is imperative that

sudoers be free of syntax errors since ssuuddoo will not run with a syntac-

tically incorrect sudoers file.

When using netgroups of machines (as opposed to users), if you store fully qualified hostnames in the netgroup (as is usually the case), you either need to have the machine's hostname be fully qualified as

returned by the hostname command or use the fqdn option in sudoers.

BUGS

If you feel you have found a bug in ssuuddoo, please submit a bug report at http://www.sudo.ws/sudo/bugs/ SSUUPPPPOORRTT Commercial support is available for ssuuddoo, see http://www.sudo.ws/sudo/support.html for details.

Limited free support is available via the sudo-users mailing list, see

http://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 merchantabil-

ity and fitness for a particular purpose are disclaimed. See the LICENSE file distributed with ssuuddoo or http://www.sudo.ws/sudo/license.html for complete details. 1.6.8p12 June 20, 2005 SUDOERS(5)