super.tab(5)
NAME
super.tab - database of restricted commands for super(1)
DESCRIPTION
The super.tab file contains the restrictions on who can execute commands with super(1). It may also contain options that modify the uid and/or gid under which a command is run; the list of environment variables that are discarded before executing a command, and so on. The reader is expected to be familiar with the super(1) man page. If you are trying to avoid reading this lengthy man page, you need to know a few simple rules. First, for a user to successfully execute a command by typing super commandName, the minimum entry in the super.tab is something like commandName FullPathToCommand userName For example, the entry cdmount /usr/local/bin/cdmount wally,dolly says that users wally and dolly may execute the /usr/local/bin/cdmount program by typing super cdmount. Second, when you define options in the super.tab file, remember that all options are orthogonal to each other, and it doesn't matter in what order they appear on a control line. Third, global options (defined on a :global or :global_options line) take effect immediately after the defining line, are valid until the end of the input or until there is a countermanding global option or pattern, and are overridden by local (per-command) options, which are defined on a regular control line. Although super has a great many options that you can set inside the super.tab file, none of them are required for security, so you don't have to be intimately familiar with this entire document in order to use super securely. The most important options that you will probably want to use are (a) a logging option like logfile=xxx or syslog=y; and (b) patterns=shell, so that the default regular-expression interpretation of wildcards is changed to the more convenient shell- style glob patterns. Unless modified with options in the super.tab file, super executes commands using effective uid root; unchanged real uid and gid; no supplementary groups; no open file descriptors save 0, 1, and 2; no environment variables except a few with safe values (see super(1)); and signal handling reset to the default. When super uses a command from a user-supplied super file (.supertab in the user's home directory) these rules are modified: the real and effective uid and gid are set to the owner of the .supertab file, and the supplementary groups are set to the user's login groups. If the special supplementary file named super.init exists, it is implictly include at the start of super.tab and every .supertab file. The file resides in the same directory as super.tab and must be owned by root, and should be world-readable. This provides a uniform configuration file applied to every super-executed command. Note that the configuration file should contain entries that are appropriate for use in both the super.tab file and any per-user supertab file. It is not a good idea to include commands in the super.init file. The variable IS_USERTAB is defined to be ``yes'' if super is processing a per-user .supertab file, and ``no'' otherwise. The following pair of entries could be used in a super.init file to allow different initialization for regular use and per-user use: :if $IS_USERTAB == yes :include /etc/super.init.per-user :if $IS_USERTAB != yes :include /etc/super.init.as-root (The use of variables and conditional expressions is explained below, in the sections Variables and Conditionally-included Control Lines, respectively.) The super.tab file is formatted as a series of control lines of the form CmdPat FullPath \ Options PermittedUsers PermittedTimes or CmdPat1::FullPath1 CmdPat2::FullPath2 ... \ Options PermittedUsers PermittedTimes or :BuiltinCmd arguments The Options, PermittedUsers, and PermittedTimes may be mixed together in any order. At least one PermittedUsers field is required, but neither Options nor PermittedTimes are required. For each control line, Super matches the following: * the user-entered command to a CmdPat; * the {user,group,host} triplet to a PermittedUsers entry; and * the current time to a PermittedTimes entry (the default permits any time). If these conditions are not satisfied, super ``falls through'' and tries the next control line. For example, the entry renice /etc/renice jack@hill jill@bucket time~8-17 specifies that between hours 8:00 and 17:00, user Jack can renice any process on host hill, and user Jill can do so on host bucket, by simply typing super renice <args> . Control lines begin in column 1, and the fields are whitespace- separated. Note that you can either use a single CmdPat and FullPath, separated by whitespace, or you can use a series of them in one control line by putting `::' between each CmdPat and FullPath pair. Whitespace may be included in a field by enclosing text in single- or double-quotes. The quoting is shell-like, in the sense that quotemarks don't have to surround the entire field, and you can switch between quotemark types in a single entry. For instance, X"a b"Y'd e' is equivalent to "Xa bYd e". Comments begin with a `#' and continue to the end of a line. There can also be blank or comment lines without any control data. A control line may be continued by preceding the newline with a backslash, and indenting the continuation line with whitespace. When the multiple-line entry is read, the text just before the backslash- newline is not modified (any whitespace before the backslash will be kept), and the backslash-newline-whitespace sequence is either eliminated entirely or treated as whitespace. The rule is simple: following a letter, digit, or underscore, it is treated as whitespace. Otherwise, it is eliminated. This means that Cmd File user1\ user2\ user3 is equivalent to Cmd File user1 user2 user3 On the other hand, Cmd File {user1,\ user2,\ user3} is equivalent to Cmd File {user1,user2,user3} That is, the sensible interpretation is done in both cases. The indentation requirement for continuation lines helps super catch typos. Comments may be placed before each backslash-newline pair, not just at the end of a continued control line.
The CmdPat Field
In response to the user typing
super cmd [ args ],
the cmd is searched for in the super.tab file. The cmd is matched
against each pattern CmdPat.
Basic Use: Simple Command Patterns without Wildcards.
Typically, a CmdPat just uses plain characters without any special
pattern-matching characters, so a cmd must be the same as the CmdPat
string. For example:
skill /usr/local/bin/skill user1 user2 user3
Here, any user in the list {user1, user2, user3} may type super skill
to execute /usr/local/bin/skill.
Advanced Use: Command Patterns with Wildcards.
More generally, a CmdPat can be either an ed-style pattern (``regex'' ---
the BSD 4.x syntax used in the re_comp()/re_exec() routines), POSIX
regular expressions, or a Bourne-shell-style pattern. You can set the
pattern style using the global option patterns (see below). The
default is ``regex'' for historical reasons; however, shell-style
patterns are easier to use without errors, and most sites should use
shell-style patterns. In all cases the patterns are extended to
support csh-style brace expansion. For instance, a{x,y,z}b stands for
the set of patterns axb ayb azb. Don't put any whitespace inside the
braces!
For convenience, there is always an implied set of braces around an
entire pattern. This means that any comma-separated list a,b,c is
interpreted as {a,b,c}, and is very helpful so that you don't have to
worry about getting braces just right when you build complex lists of
out of (say) variables containing other lists of users.
All pattern matching is ``anchored'': patterns are forced to match the
entire cmd string.
If the CmdPat is matched and the other conditions are met (such as the
user being in the PermittedUser list to execute this command), FullPath
gives the name of the actual command that will be executed with
execve(). If FullPath contains an asterisk, the asterisk is first
replaced by the user's cmd.
If you put special pattern-matching characters into the CmdPat, but
don't put an asterisk into FullPath, you have simply given more ways a
user can execute the same FullPath. This isn't useful, and in fact
isn't a good idea at all. The power of using patterns in the CmdPat
comes when FullPath includes an asterisk. For instance, a SysV-based
host might have an entry in the super.tab file that looks like:
/usr/bin/{lp,lpstat,disable,enable,cancel} * \
:operators uid=0
This would allow anybody in the "operators" group to have root access
to the line printer commands (the uid=0 tells super to set the real uid
to 0, not just the effective uid). For instance, if the user typed:
super /usr/bin/disable some_printer
then the FullPath (``*'') would be replaced by /usr/bin/disable, which
would be the command to exec.
More conveniently, the super.tab file could have a line like:
{lp,lpstat,disable,enable,cancel} /usr/bin/* \
:operators uid=0
In this case, the user can type
super disable some_printer
The asterisk-replacement ability also lets a user execute any of an
entire directory of commands, using a super.tab entry like the
following:
op/* /usr/local/super/scripts/* :operators uid=0
In this case, the user can type
super op/xyz
and super will execute /usr/local/super/scripts/op/xyz.
The asterisk-replacement capability is useful but potentially
dangerous, because it may unintentionally open the door to programs you
hadn't intended to give away. It is a sensible precaution to restrict
asterisk-replacement to entries where the valid-user list includes
trusted users only.
If you completely trust some users, but want logging of all actions
executed as root, you could use:
/* * ReallyReallyTrustedUsers
or
/.* * ReallyReallyTrustedUsers
(depending on whether patterns=shell, patterns=regex, or
patterns=posix).
The trusted users can now execute any command. Note that the pattern
begins with a slash, to ensure that the cmd must be an absolute path ---
this helps avoid accidental execs of the wrong program.
If you were really going to give everything away as shown above, you'd
probably want to exclude any public-area workstations, require the
trusted users to periodically give their passwords, and set the real
uid=root (instead of just the effective uid), so the entry might be
modified to read something like:
/* * TrustedUsers \
!{PatternsOfPublicWorkstations} \
password=y timeout=5 uid=0
The FullPath Field
The FullPath field gives the name of the actual command that will be
executed, and if it contains an asterisk, the asterisk is first
replaced by the user's cmd string. The FullPath can optionally contain
a list of initial arguments that precede any arguments passed by the
user. For example,
xyz "/usr/local/bin/blah -o1 -o2 -xrm 'a b c'" ...
specifies that when a valid user types super xyz, the command to
execute is /usr/local/bin/blah and its arguments will be
argv[1]: -o1
argv[2]: -o2
argv[3]: -xrm
argv[4]: a b c
followed by any arguments that the user put on the super command line.
Note: asterisk replacement is only done on the filename part of the
FullPath, not on the arguments. You can safely include asterisks in
the argument list. For security, the user's cmd may not contain any
whitespace or backslashes.
The FullPath string is parsed using rules similar to the Bourne shell
rules for backslashes in quoted strings, namely:
(a) backslash-newline is discarded;
(b) Otherwise, if outside a quoted substring, \x plain x,
which will not be treated as a delimiter, quotemark, or comment
character;
(c) Otherwise, inside a quoted substring of FullPath:
\\ \;
\q q, where q is the quote character that encloses the
FullPath string;
other backslashes are preserved: \x \x.
After writing a command with such backslash escapes, you should
certainly use ``super -d cmd'' to check that your args are being parsed
as expected before you offer this command to your users.
The same cmd can be listed several times in the super.tab file, in
which case the first entry that allows the user to execute the command
is chosen. The EXAMPLES section shows how this can be useful.
Permitted Users
Permitted users are those who may execute the specified Cmd's. Entries
for any number of permitted users are given after the CmdPat and
FullPath fields. Local options --- options that apply to this command
only --- may also appear anywhere after the FullPath. Options are
distinguished from permitted users because options all have the form
key=value, whereas permitted-user entries may not contain unescaped
equal signs. Each whitespace-separated word is a pattern in one of the
formats
* [user~]user[:][@host]
* [user~]:group[@host]
* [user~]user[:group][@host]
Note that the user~ part is optional. The user's login name must match
the user pattern; the user must belong to a group whose name matches
the group pattern; and the hostname must match the host pattern. If
the user, group, or host part is not given, there are no corresponding
restrictions.
If the user is root, super acts as if all permitted-user patterns are
preceded by the pattern user~root --- that is, root's rule is default-
allow, instead of the default-deny rule that applies to all ordinary
users.
By default, the ``group'' field is first matched against named groups
to which the user belongs, and then against the user's decimal gid ---
this allows the user to be put in a group in the /etc/passwd file that
isn't given a name in the /etc/group file. (If you want to change the
rules for using decimal gid, see the use of MATCH_DECIMAL_UID and
MATCH_DECIMAL_GID in super.c for details.)
Since you can restrict users to particular hosts, a single super.tab
file can be shared among many different machines. If the host part is
of the form +xyz, then xyz is interpreted as a netgroup name and any
host in netgroup xyz is matched. In that case, xyz is taken literally,
and not interpreted as a pattern to be matched. Note: netgroup lookup
is only implemented if the function innetgr() is available.
If the host part doesn't match the hostname, it might be because the
pattern and actual hostnames contain two different (but both valid)
incomplete versions of the fully-qualified domain name (FQDN). By
default, if the host part fails to match the hostname, the FQDN is
looked up and all of the ways of naming the host are matched against
the pattern. For example, if the FQDN is spacely.sprockets.com, super
will first try spacely.sprockets.com, then spacely.sprockets, and
finally spacely. This can be turned off; see option gethostbyname.
(You might want to turn it off because using nameserver lookup can
reduce security a bit --- your host may query a nameserver on another
host to obtain the FQDN, and (a) that nameserver or an intermediate
host along the way could have been subverted, or (b) another host could
impersonate the nameserver. In either case your computer could receive
incorrect hostnames.)
The patterns for valid users, groups, and hosts follow the same rules
for the CmdPats, described above: they can be entered with either ed-
style or Bourne-shell-style patterns (depending on the setting of the
patterns global option); csh-style brace expansion is allowed; and all
pattern matching is ``anchored'': patterns are forced to match the
entire username, groupname, or hostname.
To make it easy to exclude some users/groups/hosts, any of these
patterns can be negated by prefixing the pattern with `!'. If a
negated pattern is matched, the user may not execute the command, even
if there was a previous non-negated pattern that the user matched. All
patterns are read left-to-right, and the last matched pattern ``wins''.
Thus if the user/group/host list is
j.* !jo
or
user~j.* !user~jo
then the first entry allows any username beginning with `j' to execute
the command, but the second entry disallows user `jo'. If entered in
the reverse order,
!jo j.*
then the second entry, `j.*', allows all users beginning `j', and
therefore the first entry has no effect.
Permitted Times
The time condition restricts the days and times during which this
command may be matched. If the execution time isn't acceptable, then
super ignores the control line, and ``falls through'' to inspect the
next entry, just as it does if the user/group/host aren't acceptable.
A time condition looks like:
time~pattern
with patterns that look like:
Pattern Example
hh[:mm]-hh[:mm][/dayname] 13:30-17/monday
{<,>,<=,>=}hh[:mm][/dayname] <17/tues
dayname Friday
The first form explicitly specifies an interval during which the
command may be used. Times may not go past midnight; to specify the
night between Monday and Tuesday, you must do something like:
time~{17:30-24:00/mon,0-8/tues}
The second form for time patterns allows you to use logical operators.
The Monday-night example could equally have been rendered as:
time~{>17:30/mon,<8/tues}
(There is a tiny difference in the two examples above: in the first
example, the time range includes 17:30 and 8:00; in the second example,
the time range is 17:31-07:59. Use time~{>=17:30/mon,<=8/tues} to make
the interpretation identical to the first example.)
If there are a series of time patterns, they are evaluated left-to-
right, and the rightmost matching pattern is used. To permit execution
between 17:30 Monday and 8:00 Tuesday, but exclude 0:00 to 1:00
Tuesday, use:
time~{>=17:30/mon,<=8/tues} !time~{0-1/tues}
By default, valid daynames are English, but if your system supports the
setlocale(3) function, the global option lang=zzz will set the valid
names to those of locale zzz. Valid daynames are either (a) the full
names of the chosen language; (b) an official abbreviated day name for
that language; (c) a 3-or-more character abbreviation of the full
weekday; or (d) *, meaning any day. (You can check on super's valid
daynames by executing super -d, which will show the default names of
the weekdays at or near the top of its debugging output, and show the
new weekday names that take effect when the lang=zzz option is
encountered.)
Time patterns have a special defaulting rule when the execution time is
not in one of the intervals in the time list:
* if all time patterns are negated, super permits execution at
any time not in one of the listed intervals;
* otherwise, there is at least one non-negated pattern, and
super defaults to deny execution at times outside the specified
acceptable intervals.
The reason is that the natural interpretation of a series of negated
conditions, such as
!time~{0-8,17-24} !time~{sat,sun}
is to infer that all other times are acceptable for execution. On the
other hand, if there are any ordinary, non-negated times, such as
time~8-17/{mon,tues,wed,thu,fri}
the natural interpretation is that any times not explicitly mentioned
are not acceptable.
Note that explicit braces are important in the above list. If they
were missing, the implied braces around the entire pattern would render
this equivalent to
time~8-17/mon time~tues time~wed time~thu time~fri
That is, the permitted times are 8-17h on Monday, and any time on
Tuesday through Friday.
Global Conditions
Global options and conditions affect the overall super processing. To
set them, you must use a line like
:global Global Options And Patterns
or
:global_options Global Options And Patterns
For backwards compatibility, you can alternatively use
/ / GlobalOptionsAndPatterns
but this use is discouraged.
These so-called ``global'' options and conditions actually take effect
immediately after the line on which they appear, and are valid until
the end of the input or until there is a countermanding global option
or pattern. To have a global option or pattern affect the entire file,
you must place it as the first non-comment line of the super.tab file.
If there are any PermittedUser or PermittedTime conditions on the
global settings line, they are applied to each following command in the
super.tab file. The conditions look like
:global cond cond ... <> cond cond ...
PermittedUser and PermittedTime conditions to the left of ``<>'' are
processed before the local (per-command) conditions; conditions to the
right of ``<>'' are processed after the per-command conditions. If
``<>'' is missing, all conditions are processed after the local
conditions. Example 1:
:global jan <> !@+badhosts
says that user jan can usually execute any command, but under no
circumstances will a user on any host in netgroup badhosts be allowed
to execute any command. (User jan will not be allowed to execute a
command if the per-command conditions disallow it, or if jan is on one
of the badhosts computers).
Example 2:
:global !root <>
changes root's default setting from default-allow to default-deny, just
like ordinary users. Root will only be given execute permission for
entries that explicitly allow root on the per-entry line.
Global PermittedUser (PermittedTime) conditions take effect on the line
on which they are defined, and are good until another set of global
PermittedUser (PermittedTime) conditions is entered on another
:global_option line. That is, a new global condition line replaces any
previous global conditions.
One sensible approach to using global conditions is to put conditions
that allow users to execute commands before the per-command conditions
are processed, and to put negating patterns (for users/groups/hosts
that are never to be allowed to execute anything) after the per-command
conditions.
(Global options are discussed below, together with local options).
Conditionally-included Control Lines
Control lines can be conditionally included by using the :if control
line. This can be helpful when using a single super.tab file for hosts
with different architectures, or hosts in different NIS domains, etc.
The syntax is:
:if left op right moreText
The expression left op right is evaluated, and if true, moreText is
evaluated as an ordinary control line. The valid comparison operators
are:
* == string equality
* != string inequality
* ~ glob match string left against pattern right
* !~ negated glob-match.
For example, you could include a file of commands only valid on
Sun4-type machines as follows:
:if $UNAME_MACHINE ~ sun* \
:include /Path/To/Sun4/File
(UNAME_MACHINE is a variable automatically defined by super; see the
following section on variables.)
If you wanted to exclude Sun4c-type machines from using the file, you
could modify this to be:
:if $UNAME_MACHINE ~ sun* \
:if $UNAME_MACHINE != sun4c \
:include /Path/To/Sun4/File
There are no boolean operators provided, but note that there is an
implicit boolean and available by concatenating :if commands, as shown
in the second example above.
Variables
Super offers variables to make it easier to handle entries that are
duplicated or are constructed out of other entries. Variables are
defined by typing
:define VariableName VariableDefinition
or they may be imported from the environment by using
:getenv [EnvVarName...]
If you use the :getenv command, then the values of any imported
environment variables may only contain the following ``safe''
characters: -/:+._a-zA-Z0-9. If ``bad'' characters are found in a
value, the entire value is replaced with an empty string. Note that
these imported variables do not enter the environment of any executed
command; they simply become part of the super.tab variable set.
The VariableName should be made up only of letters, digits, and/or
underscore. (You can actually use any characters you wish, but super
doesn't promise to work correctly if you use characters outside the
standard set.)
The VariableDefinition begins at the first non-whitespace character
after the VariableName and continues up to but not including the final
newline. Comments embedded on the variable definition line(s) are
deleted before the variable definition is stored. A variable
definition may be continued across multiple lines by preceding each
newline with a backslash, and indenting the continuation line with
whitespace. Just as for regular control lines, the backslash-newline-
whitespace sequence is treated as whitespace if it follows a letter,
digit, or underscore; otherwise, it is eliminated. For example,
:define Users user1,\
user2,\
user3
and
:define Users user1,user2,user3
are equivalent definitions.
Unlike Makefiles, the variable definitions are not scanned first and
then the file re-scanned. Instead, variables take effect at the point
they are defined, and remain in effect until they are re-defined or end
of file --- thus variables definitions must precede their first use in
the file.
Variables may contain other variables (which must have already been
defined). Variable substitution is done when a line is first read. A
line is never re-scanned after variable substitution.
Variables are used in a file by typing
$VariableName
or
$(VariableName)
The special variable $$ is replaced by a single ``$''. Any other name
$X (where X is not a letter, digit, or underscore) is an error.
Because a line is never re-scanned after variable substitution, the
following sequence:
:define A $$
:define B A
:define C $B $$B
$C
defines C to be simply ``A $B''.
Variables can be helpful in grouping users or hosts together. For
example, you might restrict access to a command so that it can't be run
from a public-access workstation:
:define Room103_WS hosta,hostb,hostc,hostd
:define Room105_WS hoste,hostf,hostg,hosth
:define Room106_WS +nonprivate
:define PublicWorkstations $Room103_WS,$Room105_WS,$Room106_WS
SomeCmd FullPathHere !@$(PublicWorkstations)
In the above example, we have taken advantage of the implied braces
that are always placed around any pattern, so that the comma-separated
list of workstations is brace-expanded into !@hosta !@hostb ... !@hoste
!@hostf ... !@+nonprivate.
Some variables are automatically defined by super.
After super determines whether it is processing a per-user .supertab
(see super(1)), it defines IS_USERTAB to be ``yes'' if super is
processing a per-user .supertab file, and ``no'' otherwise. The allows
the super.init to act differently depending on how it is being invoked.
When the top-level super.tab file is opened, SUPER_OWNER is set to the
login name of the owner, and SUPER_HOME is set to the home directory of
the owner. This can be useful in per-user .supertab files, especially
when they include files shared among several accounts. For example,
each person's .supertab file could be simply
:include /opt/proj/common.supertab owner=cristy
Then, the /opt/proj/common.supertab file can use entries like the
following:
:global logfile=$SUPER_HOME/.superlog
* /project/tools/$SUPER_OWNER/* :toolgroup
Because the SUPER_HOME and SUPER_OWNER variables apply to the top-level
per-user files, they always refer to per-user locations.
Super defines the built-in variable CALLER to be the the login name of
the of account invoking super, and CALLER_HOME is the home directory of
$CALLER. Sample use:
sam /usr/sbin/sam group~operator uid=0 \
env=DISPLAY \
setenv=XAUTHORITY=$CALLER_HOME/.Xauthority
Here, the operator group can execute sam as root, and the GUI will
display at the caller's display (due to the use of env=DISPLAY). Since
the XAUTHORITY environment variable is set to the caller's .Xauthority
file, this will give the caller access to the same display(s) to which
s/he already has access.
The following variables are defined when super starts up. They can be
useful in conditionally-included lines (:if lines). If your host
doesn't supply these functions, or doesn't support some of the values
that super tries to fetch, the corresponding variable will be
initialized to an empty string. (Use super -b to print the names and
values of all builtin variables. This makes it simple to see what
variable values to check in :if lines.)
From the gethostname() or sysinfo() function:
* HOSTNAME Hostname, possibly canonicalized.
* HOST Hostname, short (unqualified).
From the getdomainname() function:
* NIS_DOMAIN domain set for NIS purposes.
From the sysinfo() function:
* SI_SYSNAME Name of operating system.
* SI_HOSTNAME Name of node.
* SI_RELEASE Release of operating system.
* SI_VERSION Version field of utsname.
* SI_MACHINE Kind of machine.
* SI_ARCHITECTURE Instruction set arch.
* SI_HW_SERIAL Hardware serial number.
* SI_HW_PROVIDER Hardware manufacturer.
* SI_SRPC_DOMAIN Secure RPC domain.
*
From the uname() function:
* UNAME_SYSNAME Operating system name.
* UNAME_NODENAME The nodename.
* UNAME_RELEASE Operating system release.
* UNAME_VERSION Operating system version.
* UNAME_MACHINE Machine hardware name (class).
Options
The configuration file can specify a wide variety of options, such as
requiring the user's password before executing some commands, or
restricting the command-line arguments to match certain patterns.
Options are handled very differently from conditions (conditions
include user, group, host, and time). If a control line's conditions
aren't met, super falls through and tries the next control line in the
file. After finding an acceptable control line, super will execute the
command if the options are satisfied; otherwise, it stops and doesn't
search the super.tab file any further.
Options can be divided into (a) local options, which are defined on a
regular control line, and apply only to that control line; and (b)
global options, which are defined on a :global or :global_options line,
take effect immediately after the line, and are valid until the end of
the input or until there is a countermanding global option or pattern.
All options are orthogonal to each other. It doesn't matter in what
order they appear on a control line.
Some options can be given as either local or global options. If both
are used, the local setting overrides the global one.
Two special names can be used with any of the options that take user or
group ids as arguments: owner=xxx, uid=xxx, euid=xxx, gid=xxx,
egid=xxx, u+g=xxx, groups=xxx, addgroups=xxx. These names are <owner>,
meaning the owner of the file to be executed (or the owner's group,
whichever is appropriate in the context); and <caller>, meaning the
owner or group of the user calling super. The angle brackets are
literally part of the name. These have the same values as the built-in
variables CALLER and OWNER (see the Variables section, above). For
example, the options
gid=Foo uid=<caller>
would change the group to Foo, but leave the uid unchanged.
The recognized options are:
Group 1. Options Affecting How Superfiles Are Read and Processed.
patterns=xxx
(Global) Specifies the pattern-matching type for conditions and
options. The string xxx must be one of:
posix --- patterns are POSIX regular expressions. You can use
``posix/extended'' for extended regular expressions;
``posix/icase'' for case-insensitive regular expressions;
or ``posix/extended/icase'' for both. See your regular-
expression man pages for details.
regex --- patterns are ed-style regular expressions, using the
rules embodied in the BSD 4.x routines
re_comp()/re_exec(), with the addition of csh-style brace
expansion. This is the default for historical reasons,
but most people prefer to use shell-style patterns here,
and it is recommended that you put patterns=shell (see
below) in your global options list.
shell --- patterns are approximately Bourne-shell style, with the
addition of csh-style brace expansion and the special
[[chars]] pattern. The patterns are formed from:
\x force x to be a plain character;
? matches any single character;
* matches any sequence of 0 or more chars;
[chars] matches any single character in the set;
[^chars] matches any single char NOT in the set;
[[chars]] When the pattern begins with [[, and ends with
]], then each and every character in the string
must match the ordinary square-bracket pattern
[chars] (or [^chars]).
^pat inverts the sense of the match --- the string must NOT
match the pattern.
lang=zzz
(Global) This option sets the language used for weekdays (in
time conditions). Here, zzz may be any locale available on your
host. For example, lang=de would typically cause super to use
German names. The default is the C locale, hence English names.
relative_path=y|n
(Global) If y, FullPathNames can be relative instead of
absolute. By default this is disallowed, because it is almost
always a very foolish (unsafe) thing to do.
group_slash=y|n
(Global) If y, group names can contain a slash. By default this
is disallowed, so that super can catch certain typos in the
super.tab file. (Namely, super can catch errors in which an
entry is of the form Cmd:File instead of the required Cmd::File.
The trouble is that Cmd:File looks syntactically like
user:group, and can therefore be mistaken for a valid part of a
control line. But the filename will contain a slash --- unless
you have unwisely enabled the relative_path option --- so
disallowing slashes allows super to flag the line as
syntactically invalid.)
gethostbyname=y|n
(Global) Enables or disables the use of gethostbyname() to find
the fully-qualified domain name (see the discussion in the
Permitted Users section, which describes the security issues
associated with enabling this option.) Default: enabled (if
your host supports gethostbyname()).
Group 2. Logging Options.
logfile=fname
(Global) Enables logging to a local file. Each invocation of
super (aside from ones for help) generates an entry in file
fname.
loguid=xxx
(Global) If logging is enabled with logfile=fname, the logfile
will be opened for writing using uid=xxx (can be either a
username or numeric uid). This option allows you to have the
file created/opened under another uid that does have cross-host
access, such as the uid of a system manager. (See
timestampuid=xxx for additional comments). Default: loguid=0.
mail="mail-command"
(Local|Global) Notices of super failures are piped to the shell
command mail-command. This is independent of the setting of the
logfile and syslog options. For instance, mail="mail -s Super
joeblow" will cause error messages to be mailed to user joeblow
(on some systems you may need to substitute mailx for mail).
Note: the mail-command is executed by passing it as an argument
to popen(3). This is safe to execute because of the clean
environment assured by super.
mailany="mail-command"
(Local|Global) This is identical to the mail option, except that
mailany sends notification of successful invocations as well as
errors.
rlog_host=hostname
(Global) Tells super which host's syslog daemon is to receive
log messages when option syslog=y is enabled. The option has no
effect if used after the first message is logged: once the
logger has been opened, it is not re-opened if the rlog_host is
changed. Default: the local host. Note: One could instead
configure the syslog.conf file to forward the messages to a
central machine.
syslog=y|n
(Global) Logging information is passed to the logs maintained by
the syslogd daemon. This is independent of the setting of the
logfile option (above). Error messages are by default logged at
priority LOG_ERR and successful attempts to run programs are
logged at priority LOG_INFO. (See options syslog_error and
syslog_success to change these levels.)
syslog_error=xxx
(Global) If syslog is enabled (see the syslog option), then by
default super logs error messages using syslog(3) code LOG_ERR.
This option changes the code to xxx, where xxx is any of the
usual syslog(3) priority and/or facility codes, such as
LOG_WARNING or LOG_LOCAL7|LOG_ERR. The LOG_xxx words can be
separated by whitespace, dot, and/or ``|'', but of course you
must use quotes if whitespace is included. The leading "LOG_"
is optional, and the value is case-insensitive. For example,
LOG_LOCAL7|LOG_ERR can alternatively be written as local7.err.
Super doesn't know what are sensible codes --- it's up to the
super.tab writer to choose meaningful values. For instance, if
you put
syslog_error="LOG_INFO | LOG_ERR" (bad!)
then you will get both those values or'd together and passed to
syslog().
syslog_success=xxx
(Global) This option is just like syslog_error, except that it
applies to successful-execution messages instead of error
messages. Default: LOG_INFO .
Group 3. Extra Help Information for Users.
info=xxx
(Local) The string xxx is printed when giving help to users. It
should be set to a helpful one-line description of the command.
Group 4. Password and Other Restrictions Before Approval.
maxlen=[mmm,]nnn
(Local|Global) Each argument must be no more than mmm characters
long (including the terminating null), and the sum length of all
arguments must not exceed nnn characters. A negative value
means that no limit is applied. The defaults for mmm and nnn
are set by the compile-time manifest constants MAXLEN1ARG and
MAXLENARGS, which are usually 1000 and 10,000 characters,
respectively.
nargs=[mmm-]nnn
(Local|Global) The user is required to enter mmm - nnn arguments
to the command. If just nnn is given, the user must enter
exactly nnn arguments. These arguments are in addition to any
arguments entered in the command part of the super.tab file.
The default is to allow the user to enter any number of
arguments.
arg[mmm-]nnn=sss
(Local|Global) This means that the nnn'th or mmm-nnn'th
arguments must match pattern sss. (Arguments are numbered
from 1.) The pattern must be enclosed in quotes if it contains
whitespace. Note that this option does not require that there
be mmm-nnn arguments; it only says what those arguments must
look like, if entered. You can use this option several times on
one line, with different mmm-nnn values each time, to apply
different patterns to different arguments. If more than one
pattern applies to a given argument, all of those patterns must
be matched. An empty pattern ("") is special: it has the effect
of unsetting (removing) any previous patterns for the matching
[mmm-]nnn. This can be useful if you want to change :global
settings, instead of adding to them. If there are local
arg[mmm-]nnn option(s), they completely replace all global
arg[mmm-]nnn values, even if the local mmm-nnn values do not
overlap with the global values.
owner=xxx
(Local|Global) This option specifies that the FullPath (after
asterisk-substitution) must be owned by user (or uid) xxx, or
else it won't be executed.
auth=y|n
(Local|Global) If y, user authentication is required before the
command is executed. The default authentication method is Unix
password authentication. See also the options authprompt,
authtype, authuser, timeout, and renewtime, and be sure to read
the warning under timestampbyhost.
authprompt=message
(Local|Global) Specifies the prompt used when authenticating the
user (usually the default prompt is fine). Variable
substitution is done on the prompt before printing.
authtype=type
(Local|Global) Specifies the type of authentication used when
auth=y. The type can be password or pam (if PAM is supported on
your system). The default is password. If PAM authentication
is used, super uses the service name ``super'' when looking for
authentication in your system PAM configuration files.
authuser=username
(Local|Global) Specifies the user whose authentication is
required when auth=y. The default is the password (or other
authentication) for the user who invoked super.
password=y|n
(Local|Global) This is a deprecated option; it has been replaced
by the auth and authtype options. Password=y is equivalent to
auth=y authtype=password ; and Password=n is equivalent to
auth=n.
renewtime=y|n
(Global) If y, the user's timestamp file is updated to the
current time whenever an authentication-requiring command is
executed. The result is that a user who frequently executes
authentication-requiring commands won't need to re-authenticate
until more than timeout minutes elapse since the last such
command. Otherwise, the user will need to re-authenticate
timeout minutes after last entering the password. The default
is n.
timeout=m
(Local|Global) User authentication is good for m minutes; that
is, the command may be executed without re-authenticating for m
minutes after the previous authentication (for any command).
After m minutes, user authentication will be required again
before the command can be executed. If timeout is zero or
negative, authentication is required every time the command is
used. The timestamp for user usr is recorded in the file
TIMESTAMP_DIR directory (see timestampbyhost and the FILES
section, below).
timestampbyhost=y|n
(Global) If y (default), the timestamp files are given names
that are unique on each host. For instance, jouser@somehost
will be given a timestamp file named
TIMESTAMP_DIR/somehost/jouser, where TIMESTAMP_DIR is defined in
the FILES section. If timestmapbyhost=n, the timestamp files
are given names that are unique to each user, but not unique per
host. For instance, jouser on any host will be given a
timestamp file named TIMESTAMP_DIR/jouser.
WARNING: The hostname used is that from gethostname(). Note
that this is not necessarily unique across internet domains,
since it is frequently not a fully-qualified domain name.
Therefore you should not share timestamp directories with hosts
outside the local domain. (Generally such connections don't
exist, but one could crossmount the timestamp directory disk...)
timestampuid=xxx
If a password is required, the time at which it was entered is
recorded as the mtime of a timestamp file. The timestamp file
is normally created with owner=root; however, this option causes
it to be created/modified using uid=xxx (xxx can be either a
username or numeric uid). This option is useful when a network
of hosts are sharing a cross-mounted timestamp directory. Note
that networks are typically configured to not allow root on one
host to have root access to files on another host, which will
forbid root on other hosts from creating the timestamp file
unless it's world-writable. This option allows you to have the
file created/opened under another uid that does have cross-host
access, such as the uid of a system manager. Default:
timestampuid=0.
checkvar=name[,...]
(Local) Each name in the comma-separated list is a super.tab
variable which the user must enter at a prompt from super. For
example, you might have a super shutdown command which halts the
computer. If you execute this on the wrong host there may be
some very annoyed users! So, you can include checkvar=HOST, and
the user will have to type the correct hostname in response to a
prompt from super.
Group 5. Modifications to Environment Before Executing Command.
uid=xxx
(Local) Sets the real uid to xxx just before executing the
command. If option euid isn't used, also sets the effective uid
to xxx. The uid xxx is first tried as a login name and then as
a number. If the options uid=xxx and u+g=yyy (see below) are
used together, then the u+g option only sets the group id, and
not the user id.
euid=xxx
(Local) Sets the effective uid to xxx just before executing the
command. The uid xxx is first tried as a login name and then as
a number.
gid=yyy
(Local) Sets the real gid to yyy just before executing the
command. If option egid isn't used, also sets the effective gid
to yyy. The gid yyy is first tried as a group name and then as
a number.
egid=yyy
(Local) Sets the effective gid to yyy just before executing the
command. The gid yyy is first tried as a group name and then as
a number.
u+g=zzz
(Local) Sets the real uid to zzz, the real gid to zzz's login
gid, and the supplementary groups list to zzz's supplementary
groups just before executing the command. If the euid and/or
egid option aren't given, the effective uid and/or gid are also
set. The options u+g and gid=yyy conflict with each other, and
may not be used together.
groups=name[,...]
(Local|Global) By default, the user's supplementary groups list
is deleted before executing a command (unless the option u+g is
used). This option instead sets the group list to name[,...]
addgroups=name[,...]
(Local|Global) This option adds the listed groups to the
supplementary groups list. Since the default is to provide an
empty supplementary groups list, this option usually has the
same effect as the plain groups option. However, if the options
u+g=foo addgroups=a,b,c are used, then the supplementary groups
list is composed of user foo's supplementary groups plus a, b,
and c.
argv0=name
(Local) Execute the command will execute with its first argument
(that is, the argument conventionally denoted as argv[0]), set
to name. As a convenient shorthand, the value <path> (the angle
brackets are literally part of the name) means to use the
FullPath specified in the super.tab file. By default, argv[0]
is set to Cmd, the name of the super command invoked by the
user, regardless of the actual path being invoked. However,
some programs will not run properly unless argv[0] has a
particular value. For example, suppose you want to permit users
to safely mount zip disks, and you use something like:
zipmount "/etc/mount -o nosuid /dev/xz10 /zip"
This command will fail if /etc/mount requires that it be invoked
with argv[0] set to [.../]mount, because super will use the name
zipmount. However, you can put argv0=<path> into your super.tab
file, and then the mount command will work properly.
env=name[,...]
(Global|Local) Each name in the comma-separated list is an
environment variable which should not be deleted before
executing the Cmd; these variables are in addition to the normal
variables created or passed by super (TERM, IFS, PATH, USER,
LOGNAME, HOME, ORIG_USER, ORIG_LOGNAME, ORIG_HOME, LINES,
COLUMNS, SUPERCMD). Be careful here; environment variables can
sometimes be abused to create security holes. If you use the
option more than once, the later instance overrides the earlier
one, instead of adding to it. Similarly, using it as a local
option completely overrides any global setting.
maxenvlen=nnn
(Global|Local) Specifies the maximum length of an environment
variable definition (including name, equal sign, value, and
trailing null character). The default is given by the compile-
time manifest constant MAXENVLEN, usually 1000 characters. A
negative value means no limit.
cd=dir
(Local|Global) Just before executing the command, super changes
the working directory to dir.
setenv=var=xxx
(Local|Global) The environment variable var is defined to have
the value xxx, and is passed on when executing the Cmd. You can
add several environment variable definitions by using the option
more than once.
fd=n[,...]
(Local) Each file descriptor n in the comma-separated list
should not be closed before executing the Cmd. These
descriptors are added to the usual set of descriptors kept open,
namely 0, 1, 2.
nice=n
(Local|Global) changes the ``nice'' value of the executed
command by an amount n from the default level. (Positive
increments reduce the command's priority; negative increments
increase it.)
umask=nnn
(Local|Global) sets the umask of any executed command to n. A
leading 0x or 0X in nnn means a hexadecimal value; otherwise, a
leading 0 means octal; otherwise it's decimal.
Group 6. Other Options
print=message
(Local) If the rest of the line is matched, then super prints
the specified message just before executing the command.
die=message
(Local) If the rest of the line is matched, then super does
variable-substitution on the specified message message, prints
it, and exits. This lets you conveniently set up some ``stop''
conditions, and use the die option to prevent super from looking
at any line past the stop conditions. Otherwise, you'd have to
individually attach the stop conditions to every control line.
Include Files
A super.tab file can include other files by means of an entry like
:include filename [ owner=xxx ] [ group=yyy ]
or
:optinclude file [ owner=xxx ] [ group=yyy ]
If the file isn't an absolute path, it is taken to be relative to the
directory containing the super.tab file. Include files may be nested
up to the system limit on the number of simultaneously-open file
descriptors.
The owner=xxx option specifies that the file must be owned by user xxx;
the group=yyy options specifies that the file must belong to group yyy.
If group=yyy is specified, then the file can be group-writable; by
default, the file must be writable only by owner. This can be useful
for a collection of accounts that are operated together as part of a
single project --- the several of accounts can share .supertab files by
:include-ing files belonging to the trusted user xxx and/or group yyy.
Notes:
1. The regular root-owned super.tab file can also use the
owner= or group= constructs, but it's not a good idea. Don't do
it.
2. Beware of the transitive nature of this trust: the file
owned by xxx can in turn include a file owned by yet another
user. You might wind up trusting a user you didn't intend to
trust!
The difference between :include and :optinclude is that the former
generates an error if the named file doesn't exist, whereas the latter
(optional-include) silently ignores files that don't exist.
WARNING: You should use :optinclude with great caution, and be sure not
to depend on that file being present. It is easy to imagine a scenario
in which an administrator carelessly changes an entry so that the wrong
permission is granted if an :optinclude'd file was missing.
FILES
/etc/super.tab
The location of the super.tab file on your system.
/etc/super.init
The location of the super.init file on your system.
/run/superstamps/username
Default location of the file whose mtime is used as the
timestamp for the last time the user entered his or her password
for password-requiring commands. Check your installation for
the directory used on your system.
EXAMPLES
Example 1. The control line
doit /usr/local/bin/doit \
me \
you@{h1,h32} \
ja.*:ok_j \
:goodguys
allows /usr/local/bin/doit to be run setuid-root by
* user me on any host,
* user you on hosts h1 and h32;
* any users named ja.* in group ok_j;
* and anybody in group goodguys.
Example 2. The pair of control lines
doit /usr/local/bin/doit \
u+g=smith env=TZ,TAPE \
password=y timeout=0 \
jo@PublicWorkstation
doit /usr/local/bin/doit \
u+g=smith env=TZ,TAPE \
jo
allows user jo to run /usr/local/bin/doit with uid = smith,
gid = smith's login gid, and keeping the environment variables
TZ and TAPE in addition to the standard set. If user jo is at
PublicWorkstation, the first entry will match, requiring jo's
password every time the command is used; otherwise, super will
match at the second entry, and no password is needed to run the
command.
Example 3. Here is an entry restricting CD-ROM mounting on different
hosts: tas is the only user who may mount CD's on elgar; anybody
in group xyz may mount CD's on alpha or delta; and anybody on a
host in the netgroup india may mount a CD on the india hosts.
However, user jo may never run cdmount, regardless of his or her
group or host (assuming that there is no overriding global
pattern that permits jo to use the command). Note that shell-
style patterns are used, not regex-style patterns.
cdmount /usr/local/bin/cdmount \
tas@elgar \
:xyz@{alpha,delta} \
*@+india \
!jo
SEE ALSO
super(1). local SUPER.TAB(5)
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