.\" Automatically generated by Pod::Man 4.09 (Pod::Simple 3.35) .\" .\" Standard preamble: .\" ======================================================================== .de Sp \" Vertical space (when we can't use .PP) .if t .sp .5v .if n .sp .. .de Vb \" Begin verbatim text .ft CW .nf .ne \\$1 .. .de Ve \" End verbatim text .ft R .fi .. .\" Set up some character translations and predefined strings. \*(-- will .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left .\" double quote, and \*(R" will give a right double quote. \*(C+ will .\" give a nicer C++. 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No user-serviceable parts. . \" fudge factors for nroff and troff .if n \{\ . ds #H 0 . ds #V .8m . ds #F .3m . ds #[ \f1 . ds #] \fP .\} .if t \{\ . ds #H ((1u-(\\\\n(.fu%2u))*.13m) . ds #V .6m . ds #F 0 . ds #[ \& . ds #] \& .\} . \" simple accents for nroff and troff .if n \{\ . ds ' \& . ds ` \& . ds ^ \& . ds , \& . ds ~ ~ . ds / .\} .if t \{\ . ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u" . ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u' . ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u' . ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u' . ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u' . ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u' .\} . \" troff and (daisy-wheel) nroff accents .ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V' .ds 8 \h'\*(#H'\(*b\h'-\*(#H' .ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#] .ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H' .ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u' .ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#] .ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#] .ds ae a\h'-(\w'a'u*4/10)'e .ds Ae A\h'-(\w'A'u*4/10)'E . \" corrections for vroff .if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u' .if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u' . \" for low resolution devices (crt and lpr) .if \n(.H>23 .if \n(.V>19 \ \{\ . ds : e . ds 8 ss . ds o a . ds d- d\h'-1'\(ga . ds D- D\h'-1'\(hy . ds th \o'bp' . ds Th \o'LP' . ds ae ae . ds Ae AE .\} .rm #[ #] #H #V #F C .\" ======================================================================== .\" .IX Title "RESTRICTED-SSH-COMMANDS 1" .TH RESTRICTED-SSH-COMMANDS 1 "2017-09-29" "restricted-ssh-commands" " " .\" 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" restricted\-ssh\-commands \- Restrict SSH users to a predefined set of commands .SH "SYNOPSIS" .IX Header "SYNOPSIS" \&\fB/usr/lib/restricted\-ssh\-commands\fR [\fIconfig\fR] .SH "DESCRIPTION" .IX Header "DESCRIPTION" restricted-ssh-commands is intended to be called by \s-1SSH\s0 to restrict a user to only run specific commands. A list of allowed regular expressions can be configured in \fI/etc/restricted\-ssh\-commands/\fR. The requested command has to match at least one regular expression. Otherwise it will be rejected. .PP restricted-ssh-commands is useful to grant restricted access via \s-1SSH\s0 to do only certain task. For example, it could allow a user to upload a Debian packages via scp and run reprepro processincoming. .PP The optional \fIconfig\fR parameter is the name of the configuration inside \&\fI/etc/restricted\-ssh\-commands/\fR that should be used. If \fIconfig\fR is omitted, the user name will be used. .SH "USAGE" .IX Header "USAGE" Create a configuration file in \fI/etc/restricted\-ssh\-commands/$config\fR and add following line to \fI~/.ssh/authorized_keys\fR to use it .PP .Vb 2 \& command="/usr/lib/restricted\-ssh\-commands",no\-port\-forwarding,\e \& no\-X11\-forwarding,no\-agent\-forwarding,no\-pty ssh\-rsa [...] .Ve .PP To enable debug output, set the \s-1RSC_VERBOSE\s0 environment variable to a nonzero value, e.g. by adding it to authorized_keys: .PP .Vb 1 \& command="RSC_VERBOSE=1 /usr/lib/restricted\-ssh\-commands" .Ve .SH "EXIT STATUS" .IX Header "EXIT STATUS" \&\fBrestricted-ssh-commands\fR will exit with the exit status from the called command if the command is allowed and therefore executed. If the command is rejected, \fBrestricted-ssh-commands\fR will exit with one of the following exit codes. .ie n .IP "124" 8 .el .IP "\f(CW124\fR" 8 .IX Item "124" A configuration file was found and contains at least one regular expression, but the requested command does not match any of those regular expressions. .ie n .IP "125" 8 .el .IP "\f(CW125\fR" 8 .IX Item "125" The configuration file is missing or does not contain any regular expressions. Thus all commands are rejected. .SH "EXAMPLES" .IX Header "EXAMPLES" Imagine you have a Debian package repository on a host using reprepro and you want to allow package upload to it. Assuming the user is reprepro and the package configuration is stored in \fI/srv/reprepro\fR, you would create the configuration file \fI/etc/restricted\-ssh\-commands/reprepro\fR containing these three regular expressions: .PP .Vb 3 \& ^scp \-p( \-d)? \-t( \-\-)? /srv/reprepro/incoming(/[\-a\-z0\-9+~_.]*[\-a\-z0\-9+~_])?$ \& ^chmod 0644( /srv/reprepro/incoming/[\-a\-z0\-9+~_.]*[\-a\-z0\-9+~_])+$ \& ^reprepro ( \-V)? \-b /srv/reprepro processincoming foobar$ .Ve .SH "SECURITY NOTES" .IX Header "SECURITY NOTES" It is dangerous and not recommended to use negative bracket expressions (like [^ /]). Characters like \s-1CR LF $ &\s0 ; ( ) and so on can be abused to execute arbitrary commands. For example, the rule .PP .Vb 1 \& ^echo [^ /]$ .Ve .PP can be abused to execute these commands .PP .Vb 2 \& echo foo&echo owned \& echo foo&rm \-rf $(printf "\ex2f") .Ve .PP where a \s-1TAB\s0 is used instead of spaces after the first ampersand. Therefore only use positive bracked expressions (like [a\-z]). .SH "FILES" .IX Header "FILES" The configuration files are placed in \fI/etc/restricted\-ssh\-commands/\fR. Each line in the configuration file represents one \s-1POSIX\s0 extended regular expression (\s-1ERE\s0). Lines starting with # are considered as comments and are ignored. Empty lines (containing only whitespaces) are ignored, too. .SH "SEE ALSO" .IX Header "SEE ALSO" Regular expressions on http://tldp.org/LDP/Bash\-Beginners\-Guide/html/sect_04_01.html .PP Section 9.4 Extended Regular Expressions (\s-1ERE\s0) on http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html .SH "AUTHOR" .IX Header "AUTHOR" \&\fBrestricted-ssh-commands\fR and this manpage have been written by Benjamin Drung .