source: web/old/remctl-2.14/docs/remctld.8 @ f6f3e91

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.\" ========================================================================
.\"
.IX Title "REMCTLD 8"
.TH REMCTLD 8 "2009-05-22" "2.14" "remctl"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
remctld \- Server for remctl, a remote command execution utility
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
remctld [\fB\-dFhmSv\fR] [\fB\-f\fR \fIconfig\fR] [\fB\-k\fR \fIkeytab\fR] [\fB\-P\fR \fIfile\fR]
[\fB\-p\fR \fIport\fR] [\fB\-s\fR \fIservice\fR]
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fBremctld\fR is the server for remctl.  It accepts a connection from remctl,
receives the command to execute and the arguments, verifies authorization
of the user and executes the command, returning the result back to the
client.  All connections are authenticated using GSS-API Kerberos v5, and
all transmissions are also encrypted using the GSS-API privacy layer.
.PP
\&\fBremctld\fR is normally started using \fBtcpserver\fR or from \fBinetd\fR, but it
may be run in stand-alone mode as a daemon using \fB\-m\fR.  Either \fB\-s\fR must
be given to use an alternate identity (which will require the same flag be
used for \fBremctl\fR client invocations), or it must be run as root to read
the host keytab file.  \fBremctld\fR logs its activity using syslog (the
daemon facility).
.PP
The location of the configuration file may be specified with the \fB\-f\fR
option.  The default location is \fI/usr/local/etc/remctl.conf\fR.  For
information on the format of the configuration file, see \*(L"\s-1CONFIGURATION\s0
\&\s-1FILE\s0\*(R" below.
.PP
When the command is run, several environment variables will be set
providing information about the remote connection.  See \s-1ENVIRONMENT\s0
below for more information.
.SH "OPTIONS"
.IX Header "OPTIONS"
.IP "\fB\-d\fR" 4
.IX Item "-d"
Enable verbose debug logging to syslog (or to standard output if \fB\-S\fR is
also given).
.IP "\fB\-F\fR" 4
.IX Item "-F"
Normally when running in stand-alone mode (\fB\-m\fR), \fBremctld\fR backgrounds
itself to run as a daemon, changes directory to \fI/\fR, and drops any
controlling terminal.  This flag suppresses this behavior, usually for
debugging or so that \fBremctld\fR can be monitored by other processes.
.IP "\fB\-f\fR \fIconfig\fR" 4
.IX Item "-f config"
The configuration file for \fBremctld\fR, overriding the default path.
.IP "\fB\-h\fR" 4
.IX Item "-h"
Show a brief usage message and then exit.
.IP "\fB\-k\fR \fIkeytab\fR" 4
.IX Item "-k keytab"
Use \fIkeytab\fR as the keytab for server credentials rather than the system
default or the value of the \s-1KRB5_KTNAME\s0 environment variable.  Using \fB\-k\fR
just sets the \s-1KRB5_KTNAME\s0 environment variable internally in the process.
.IP "\fB\-m\fR" 4
.IX Item "-m"
Enable stand-alone mode.  \fBremctld\fR will listen to its configured port
and fork a new child for each incoming connection.  By default, when this
option is used, \fBremctld\fR also changes directory to \fI/\fR, backgrounds
itself, and closes standard input, output, and error.  To not background,
pass \fB\-F\fR as well.  To not close standard output and error and continue
using them for logging, pass \fB\-S\fR as well.
.Sp
To determine the port, \fBremctld\fR attempts to look up the \f(CW\*(C`remctl\*(C'\fR
service in the local \fI/etc/services\fR file and uses the port defined
there.  If the \f(CW\*(C`remctl\*(C'\fR service could not be found, it uses 4373, the
registered remctl port.
.IP "\fB\-P\fR \fIfile\fR" 4
.IX Item "-P file"
When running in stand-alone mode (\fB\-m\fR), write the \s-1PID\s0 of \fBremctld\fR to
\&\fIfile\fR.  This option is ignored unless \fB\-m\fR is also given.
.IP "\fB\-p\fR \fIport\fR" 4
.IX Item "-p port"
When running in stand-alone mode, Listen on port \fIport\fR rather than the
default.  This option does nothing unless used with \fB\-m\fR.
.IP "\fB\-S\fR" 4
.IX Item "-S"
Rather than logging to syslog, log debug and routine connection messages
to standard output and error messages to standard error.  This option is
mostly useful for testing and debugging.
.IP "\fB\-s\fR \fIservice\fR" 4
.IX Item "-s service"
Specifies which principal is used as the server identity for client
authentication.  The client must also use the same identity as the server
identity for authentication to succeed.  By default, \fBremctld\fR accepts
any principal with a key in the default keytab file (which can be changed
with the \fB\-k\fR option).  This is normally the most desirable behavior.
.IP "\fB\-v\fR" 4
.IX Item "-v"
Print the version of \fBremctld\fR and exit.
.SH "CONFIGURATION FILE"
.IX Header "CONFIGURATION FILE"
The configuration file defines the allowed commands and specifies access
control information.  The configuration file format is lines of space\- or
tab-separated strings, where each line is:
.PP
.Vb 1
\&    command subcommand executable [option=value ...] acl [acl ...]
.Ve
.PP
Each command consists of a command, a subcommand, and zero or more
arguments.  Each configuration line defines an acceptable command and
subcommand (or, if \f(CW\*(C`ALL\*(C'\fR is used as mentioned below under \fIservice\fR, a
set of commands).  The first configuration line matching the received
command is used, so list more specific entries before more general
entries.
.PP
Blank lines and lines beginning with \f(CW\*(C`#\*(C'\fR are ignored.  Lines can be
continued on the next line by ending them with a backslash (\f(CW\*(C`\e\*(C'\fR).  Be
aware that comments can be continued with a backslash as well.
.PP
As a special case, a line like:
.PP
.Vb 1
\&    include file
.Ve
.PP
will include \fIfile\fR as if its contents were pasted verbatim into the
configuration file at that point.  \fIfile\fR may be a directory, in which
case all files whose names do not contain a period found in that directory
will be included (in no particular order).  \fIfile\fR should be a fully
qualified path.
.PP
The meaning of these fields is:
.IP "\fIcommand\fR" 4
.IX Item "command"
The command being issued.  Normally, related commands (such as all
commands for managing a particular service) are grouped together as
subcommands under one command.
.IP "\fIsubcommand\fR" 4
.IX Item "subcommand"
The subcommand within the command being requested, such as \f(CW\*(C`release\*(C'\fR for
the release function of the \s-1AFS\s0 volume backend.  If the keyword \f(CW\*(C`ALL\*(C'\fR is
used instead of a specific subcommand, this line matches all subcommands
with the given command and can be used to dispatch all subcommands under
that command to the same executable with the same ACLs.  Since the first
matching entry is used, list entries for specific services first (if any)
and then the \f(CW\*(C`ALL\*(C'\fR catch-all.
.Sp
\&\fBremctld\fR accepts commands with no subcommand argument.  Such commands
will only match lines in the configuration file with \f(CW\*(C`ALL\*(C'\fR for the
service.  (The \fBremctl\fR client will not send such commands, but they can
be sent using the client library or via another implementation.)
.Sp
The subcommand is always passed as the first argument to the executable
program that is listed for that service unless no subcommand was given.
.IP "\fIexecutable\fR" 4
.IX Item "executable"
The full path to the command executable to run for this command and
subcommand combination.  (See examples below.)
.IP "\fIoption\fR=\fIvalue\fR" 4
.IX Item "option=value"
An option setting that applies to this command.  Supported option settings
are:
.RS 4
.IP "\fIlogmask\fR=\fIn\fR[,...]" 4
.IX Item "logmask=n[,...]"
Limit logging of command arguments.  Any argument listed in the logmask
list will have its value logged as \*(L"**MASKED**\*(R".  This is to avoid logging
the arguments of commands that take private information such as passwords.
The logmask list should contain argument numbers separated by commas, with
the \fIsubcommand\fR considered argument 1.  The \fIcommand\fR argument cannot
be masked.
.Sp
For example, if the command is \f(CW\*(C`admin passwd \f(CIusername\f(CW \f(CIpassword\f(CW\*(C'\fR,
then you'd want to set logmask to \f(CW3\fR, so the password argument gets
logged as \f(CW\*(C`**MASKED**\*(C'\fR.  If the command is \f(CW\*(C`user passwd \f(CIusername\f(CW
\&\f(CIold\-password\f(CW \f(CInew\-password\f(CW\*(C'\fR, you'd want to set logmask to \f(CW\*(C`3,4\*(C'\fR.
.ie n .IP "\fIstdin\fR=(\fIn\fR | ""last"")" 4
.el .IP "\fIstdin\fR=(\fIn\fR | \f(CWlast\fR)" 4
.IX Item "stdin=(n | last)"
Specifies that the \fIn\fRth or last argument to the command be passed on
standard input instead of on the command line.  The value of this option
must either be the number of argument to pass on standard input (with the
\&\fIsubcommand\fR considered argument 1) or the special value \f(CW\*(C`last\*(C'\fR, which
indicates that the final argument (no matter how many there are) be passed
on standard input.
.Sp
The \fIsubcommand\fR cannot be passed on standard input, so \fIn\fR must be at
least \f(CW2\fR.  If this option is set to \f(CW\*(C`last\*(C'\fR and no arguments are given
except the \fIcommand\fR and possibly the \fIsubcommand\fR, nothing will be
passed on standard input.
.Sp
This option is used primarily for passing large amounts of data that may
not fit on the command line or data that contains \s-1NUL\s0 characters.  It can
also be used for arguments like passwords that shouldn't be exposed on the
command line.  Only at most one argument may be passed on standard input
to the command.
.RE
.RS 4
.RE
.IP "\fIacl\fR" 4
.IX Item "acl"
One or more entries of the form [\fImethod\fR:]\fIdata\fR, where \fImethod\fR
specifies an access control method to be used, and \fIdata\fR contains
parameters whose meaning depends on the method.  If the method is omitted,
the data is processed as described for the \f(CW\*(C`file\*(C'\fR method.
.Sp
If \fImethod\fR is omitted, \fIacl\fR must either begin with \f(CW\*(C`/\*(C'\fR or must not
contain \f(CW\*(C`=\*(C'\fR.  Otherwise, it will be parsed as an option instead.  If
there is any ambiguity, prepend the \fImethod\fR.
.Sp
Each entry is checked in order, and access is granted as soon as an
entry matches.  If no entry matches, access is denied.  The following
methods are supported:
.RS 4
.IP "file" 4
.IX Item "file"
The data is the full path of an \s-1ACL\s0 file or to a directory containing \s-1ACL\s0
files.  Directories are handled as described for the include directive in
configuration files.  An \s-1ACL\s0 file contains one entry per line, in the
[\fImethod\fR:]\fIdata\fR form described above.  Entries are handled exactly as
if they had appeared in the configuration file except that the default
method is \f(CW\*(C`princ\*(C'\fR instead of \f(CW\*(C`file\*(C'\fR.  Blank lines and lines beginning
with \f(CW\*(C`#\*(C'\fR are ignored in the \s-1ACL\s0 files.
.Sp
For backward compatibility, a line like:
.Sp
.Vb 1
\&    include [<method>:]<data>
.Ve
.Sp
in an \s-1ACL\s0 file behaves exactly as if the \f(CW\*(C`include\*(C'\fR directive had been
omitted, except that the default method is \f(CW\*(C`file\*(C'\fR.  Thus, writing:
.Sp
.Vb 1
\&    include <path>
.Ve
.Sp
in an \s-1ACL\s0 file is the same as writing:
.Sp
.Vb 1
\&    file:<path>
.Ve
.Sp
and is handled identically to the include directive in configuration
files.
.IP "princ" 4
.IX Item "princ"
The data is the name of a Kerberos v5 principal which is to be granted
access, such as \f(CW\*(C`username@EXAMPLE.ORG\*(C'\fR.
.IP "deny" 4
.IX Item "deny"
This method is used to selectively deny access.  The data is parsed as a
[\fImethod\fR:]\fIdata\fR and evaluated as described above, with the default
scheme being \f(CW\*(C`princ\*(C'\fR.  If it matches, access is denied immediately
without examining any further entries.  Otherwise, processing continues.
.Sp
Remember that access is granted as soon as an entry matches.  For \f(CW\*(C`deny\*(C'\fR
rules to be effective, they therefore must come before any ACLs they are
intended to override.  Be careful when using \f(CW\*(C`deny\*(C'\fR when including a
directory of \s-1ACL\s0 files, since the files in that directory are read in an
undefined order (not in alphabetical order by filename).  It's best to
explicitly include the file containing \f(CW\*(C`deny\*(C'\fR \s-1ACL\s0 rules first.
.Sp
Note that \f(CW\*(C`deny\*(C'\fR only denies access; it never grants it.  Thus, deny
alone does not grant access to anyone, and using deny on itself as in
\&\f(CW\*(C`deny:deny:foo\*(C'\fR neither denies nor grants access to anyone.
.IP "gput" 4
.IX Item "gput"
This method is used to grant access based on the \s-1CMU\s0 \s-1GPUT\s0 (Global
Privileged User Table \*(-- see \fIgput\fR\|(5)).  The data is either a \s-1GPUT\s0 role
name or a string of the form \fIgroup\fR[\fIxform\fR], where \fIgroup\fR is a \s-1GPUT\s0
role name and \fIxform\fR is a \s-1GPUT\s0 transform string.  Access is granted if
the user is a member of the specified \s-1GPUT\s0 group, after applying either
the optional \fIxform\fR or the default transform.
.Sp
This method is supported only if \fBremctld\fR was compiled with \s-1GPUT\s0 support
by using the \f(CW\*(C`\-\-with\-gput\*(C'\fR configure option.
.RE
.RS 4
.Sp
The keyword \s-1ANYUSER\s0 may be used instead of the ACLs to allow access to all
users.  The user still needs to authenticate to \fBremctld\fR; this only
affects authorization.  This can be used for backend programs that want to
check ACLs themselves and will retrieve the authenticated principal from
the \s-1REMOTE_USER\s0 environment variable.  Note that \s-1ANYUSER\s0 accepts \fBany\fR
authenticated user, including cross-realm users from foreign Kerberos
realms.
.Sp
Support for \s-1ACL\s0 schemes is new in remctl 2.13.  Prior versions of
\&\fBremctld\fR expected only files in the main \fBremctld\fR configuration file,
and only principals or lines starting with \f(CW\*(C`include\*(C'\fR in those files,
without any \fImethod\fR: prefixes.
.RE
.SH "ENVIRONMENT"
.IX Header "ENVIRONMENT"
The following environment variables will be set for any commands run via
\&\fBremctld\fR:
.IP "\s-1REMOTE_USER\s0" 4
.IX Item "REMOTE_USER"
.PD 0
.IP "\s-1REMUSER\s0" 4
.IX Item "REMUSER"
.PD
Set to the Kerberos principal of the authenticated client.  \s-1REMUSER\s0 has
always been set by \fBremctld\fR; \s-1REMOTE_USER\s0 is also set (to the same value)
starting with remctl 2.1.
.IP "\s-1REMOTE_ADDR\s0" 4
.IX Item "REMOTE_ADDR"
The \s-1IP\s0 address of the remote host.  Currently, this is always an IPv4
address, but in the future it may be set to an IPv6 address.  This
environment variable was added in remctl 2.1.
.IP "\s-1REMOTE_HOST\s0" 4
.IX Item "REMOTE_HOST"
The hostname of the remote host, if it was available.  If reverse name
resolution failed, this environment variable will not be set.  This
variable was added in remctl 2.1.
.PP
\&\fBremctld\fR also used to set \s-1SCPRINCIPAL\s0 for (partial) backward
compatibility with \fBsysctld\fR, but stopped doing so as of remctl 2.1.
.PP
If the \fB\-k\fR flag is used, \fBremctld\fR will also set \s-1KRB5_KTNAME\s0 to the
provided keytab path.  This is primarily for communication with the
GSS-API library, but this setting will also be inherited by any commands
run by \fBremctld\fR.
.SH "EXAMPLES"
.IX Header "EXAMPLES"
Typically \fBremctld\fR is to be started as follows, where \*(L"hostname\*(R" is the
machine where remctld will run, and 4373 is the port:
.PP
.Vb 1
\&    tcpserver hostname 4373 remctld
.Ve
.PP
The equivalent line for \fI/etc/inetd.conf\fR is:
.PP
.Vb 1
\&    4373 stream tcp nowait root /usr/sbin/tcpd /usr/sbin/remctld
.Ve
.PP
or:
.PP
.Vb 1
\&    remctl stream tcp nowait root /usr/sbin/tcpd /usr/sbin/remctld
.Ve
.PP
if the \f(CW\*(C`remctl\*(C'\fR service is listed in your \fI/etc/services\fR file.
.PP
To start \fBremctld\fR in stand-alone mode instead, run:
.PP
.Vb 1
\&    remctld \-m
.Ve
.PP
Example configuration file:
.PP
.Vb 7
\& # Comments can be used like this.
\& accounts create /usr/local/bin/doaccount  /etc/acl/group1 \e
\&     /etc/acl/group2
\& accounts delete /usr/local/bin/doaccount  /etc/acl/group3
\& accounts view   /usr/local/bin/doaccount  ANYUSER
\& accounts passwd /usr/local/bin/dopasswd   logmask=3 /etc/acl/group1
\& printing ALL    /usr/local/bin/printthing /etc/acl/group2
.Ve
.PP
The commands \f(CW\*(C`accounts create\*(C'\fR, \f(CW\*(C`accounts delete\*(C'\fR, and so forth will all
be passed to /usr/local/bin/doaccount with the first argument being the
specific subcommand, with the exception of \f(CW\*(C`accounts passwd\*(C'\fR.  That
command will be passed to /usr/local/bin/dopasswd instead, but it will
still get \f(CW\*(C`passwd\*(C'\fR as its first argument.  The third argument to
\&\f(CW\*(C`accounts passwd\*(C'\fR (presumably the password) will not be logged to syslog.
All commands starting with \f(CW\*(C`printing\*(C'\fR will be passed to
/usr/local/bin/printthing.
.PP
Example \s-1ACL\s0 file using the scheme support new in remctl 2.13:
.PP
.Vb 5
\&    # This is a comment.
\&    deny:baduser@EXAMPLE.ORG
\&    file:/etc/remctl/acl/admins
\&    principal:service/admin@EXAMPLE.ORG
\&    service/other@EXAMPLE.ORG
.Ve
.PP
This \s-1ACL\s0 file will reject \f(CW\*(C`baduser@EXAMPLE.ORG\*(C'\fR even if that user would
have been allowed by one of the other \s-1ACL\s0 rules.  It will then grant
access according to the \s-1ACL\s0 entries in \fI/etc/remctl/acl/admins\fR and the
specific principals \f(CW\*(C`service/admin@EXAMPLE.ORG\*(C'\fR and
\&\f(CW\*(C`service/other@EXAMPLE.ORG\*(C'\fR.  The last line takes advantage of the
default \s-1ACL\s0 method of \f(CW\*(C`principal\*(C'\fR when processing an \s-1ACL\s0 file.
.SH "CAVEATS"
.IX Header "CAVEATS"
When using Heimdal with triple-DES keys and talking to old clients that
only speak version one of the remctl protocol, \fBremctld\fR may have
problems with \s-1MIC\s0 verification.  This doesn't affect new clients and
servers since the version two protocol doesn't use MICs.  If you are using
Heimdal and run into \s-1MIC\s0 verification problems, see the \s-1COMPATIBILITY\s0
section of \fIgssapi\fR\|(3).
.PP
\&\fBremctld\fR does not itself impose any limits on the number of child
processes or other system resources.  You may want to set resource limits
in your inetd server or with \fBulimit\fR when running it as a standalone
daemon or under \fBtcpserver\fR.
.PP
Command arguments may not contain \s-1NUL\s0 characters and must be shorter than
the operating system limit on the length of a command line since they're
passed to the command as command-line arguments.  The exception is an
argument passed via standard input using the \f(CW\*(C`stdin=\*(C'\fR option in the
configuration file.  At most one argument may be passed that way.
.SH "NOTES"
.IX Header "NOTES"
The remctl port number, 4373, was derived by tracing the diagonals of a
\&\s-1QWERTY\s0 keyboard up from the letters \f(CW\*(C`remc\*(C'\fR to the number row.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fIremctl\fR\|(1), \fIsyslog\fR\|(3), \fItcpserver\fR\|(1)
.PP
The current version of this program is available from its web page at
<http://www.eyrie.org/~eagle/software/remctl/>.
.SH "AUTHOR"
.IX Header "AUTHOR"
Anton Ushakov <antonu@stanford.edu> is the original author.  Updates and
current maintenance are done by Russ Allbery <rra@stanford.edu>.
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
Copyright 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Board of
Trustees, Leland Stanford Jr. University.  All rights reserved.
.PP
Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted, provided
that the above copyright notice appear in all copies and that both that
copyright notice and this permission notice appear in supporting
documentation, and that the name of Stanford University not be used in
advertising or publicity pertaining to distribution of the software
without specific, written prior permission.  Stanford University makes no
representations about the suitability of this software for any purpose.
It is provided \*(L"as is\*(R" without express or implied warranty.
.PP
\&\s-1THIS\s0 \s-1SOFTWARE\s0 \s-1IS\s0 \s-1PROVIDED\s0 \*(L"\s-1AS\s0 \s-1IS\s0\*(R" \s-1AND\s0 \s-1WITHOUT\s0 \s-1ANY\s0 \s-1EXPRESS\s0 \s-1OR\s0 \s-1IMPLIED\s0
\&\s-1WARRANTIES\s0, \s-1INCLUDING\s0, \s-1WITHOUT\s0 \s-1LIMITATION\s0, \s-1THE\s0 \s-1IMPLIED\s0 \s-1WARRANTIES\s0 \s-1OF\s0
\&\s-1MERCHANTABILITY\s0 \s-1AND\s0 \s-1FITNESS\s0 \s-1FOR\s0 A \s-1PARTICULAR\s0 \s-1PURPOSE\s0.