'\" t
.\"     Title: ssh_filter_btrbk
.\"    Author: [see the "AUTHOR(S)" section]
.\" Generator: Asciidoctor 2.0.18
.\"      Date: 2023-03-25
.\"    Manual: Btrbk Manual
.\"    Source: Btrbk 0.32.6
.\"  Language: English
.\"
.TH "SSH_FILTER_BTRBK" "1" "2023-03-25" "Btrbk 0.32.6" "Btrbk Manual"
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.\}
.SH "NAME"
ssh_filter_btrbk \- ssh command filter script for btrbk
.SH "SYNOPSIS"
.sp
.nf
ssh_filter_btrbk.sh [\-s|\-\-source] [\-t|\-\-target] [\-d|\-\-delete]
    [\-i|\-\-info] [\-\-snapshot] [\-\-send] [\-\-receive]
    [\-p|\-\-restrict\-path <path>] [\-l|\-\-log] [\-\-sudo]
.fi
.br
.SH "DESCRIPTION"
.sp
\fBssh_filter_btrbk.sh\fP restricts SSH commands to commands used by
\fIbtrbk\fP. It examines the SSH_ORIGINAL_COMMAND environment variable
(set by sshd) and executes it only if it contains commands used by
\fIbtrbk\fP.
.sp
The accepted commands are specified by the "\-\-source", "\-\-target",
"\-\-delete" and "\-\-info" options.
.sp
The following commands are always allowed:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.  sp -1
.  IP \(bu 2.3
.\}
"btrfs subvolume show" (not affected by "\-\-restrict\-path")
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.  sp -1
.  IP \(bu 2.3
.\}
"btrfs subvolume list" (not affected by "\-\-restrict\-path")
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.  sp -1
.  IP \(bu 2.3
.\}
"readlink"
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.  sp -1
.  IP \(bu 2.3
.\}
"test \-d" (only if "compat busybox" configuration option is set)
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.  sp -1
.  IP \(bu 2.3
.\}
"cat /proc/self/mountinfo"
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.  sp -1
.  IP \(bu 2.3
.\}
pipes through "gzip", "pigz", "bzip2", "pbzip2", "bzip3", "xz",
"lzop", "lz4", "zstd" (stream_compress)
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.  sp -1
.  IP \(bu 2.3
.\}
pipes through "mbuffer" (stream_buffer, rate_limit)
.RE
.sp
Example line in /root/.ssh/authorized_keys on a backup target host:
.sp
.if n .RS 4
.nf
.fam C
command="ssh_filter_btrbk.sh \-\-target \-\-delete \-\-restrict\-path /mnt/btr_backup",restrict ssh\-rsa AAAAB3NzaC1...hwumXFRQBL btrbk@example.org
.fam
.fi
.if n .RE
.SH "OPTIONS"
.sp
\-s, \-\-source
.RS 4
Allow commands for backup source: "btrfs subvolume snapshot",
"btrfs send". Equivalent to "\-\-snapshot \-\-send".
.RE
.sp
\-t, \-\-target
.RS 4
Allow commands for backup and archive target: "btrfs receive",
"mkdir".
.RE
.sp
\-d, \-\-delete
.RS 4
Allow commands for subvolume deletion: "btrfs subvolume
delete". This is used for backup source if
\fIsnapshot_preserve_daily\fP is not set to \(lqall\(rq, and for backup
targets if \fItarget_preserve_daily\fP is not set to \(lqall\(rq.
.RE
.sp
\-i, \-\-info
.RS 4
Allow informative commands: "btrfs subvolume find\-new", "btrfs
filesystem usage". This is used by btrbk \fIinfo\fP and \fIdiff\fP
commands.
.RE
.sp
\-\-snapshot
.RS 4
Allow btrfs snapshot command: "btrfs subvolume snapshot".
.RE
.sp
\-\-send
.RS 4
Allow btrfs send command: "btrfs send".
.RE
.sp
\-\-receive
.RS 4
Allow btrfs receive command: "btrfs receive".
.RE
.sp
\-p, \-\-restrict\-path <path>
.RS 4
Restrict commands to <path>. Note that "btrfs subvolume show",
"btrfs subvolume list" are NOT affected by this option.
.sp
It is not possible to restrict commands to exact subvolume names, as
btrfs\-receive(8) takes a <path> as argument (directory, not including
the subvolume file name to be created, this is encoded in the
send\-stream).
.RE
.sp
\-l, \-\-log
.RS 4
Log ACCEPT and REJECT messages to the system log.
.RE
.sp
\-\-sudo
.RS 4
Allow btrfs commands to be called via sudo. Enable this if you
have "backend btrfs\-progs\-sudo" in your btrbk configuration file.
.RE
.SH "AVAILABILITY"
.sp
Please refer to the btrbk project page \fB\c
.URL "https://digint.ch/btrbk/" "" "\fP"
for further details.
.SH "SEE ALSO"
.sp
\fBbtrbk\fP(1),
\fBbtrbk.conf\fP(5),
\fBbtrfs\fP(8)
.SH "AUTHOR"
.sp
Axel Burri \c
.MTO "axel\(attty0.ch" "" ""