#!/usr/bin/perl
# Name: /usr/local/bin/rrsync (should also have a symlink in /usr/bin)
# Purpose: Restricts rsync to subdirectory declared in .ssh/authorized_keys
# Author: Joe Smith <js-cgi@inwap.com> 30-Sep-2004
# Modified by: Wayne Davison <wayned@samba.org>
use strict;

use Socket;
use Cwd 'abs_path';
use File::Glob ':glob';
use constant RSYNC => 'rsync'; # Optionally set the path of rsync here.
use constant LOGFILE => 'rrsync.log';
my $Usage = <<EOM;
Use 'command="$0 [-ro] SUBDIR"'
	in front of lines in $ENV{HOME}/.ssh/authorized_keys
EOM

our $ro = (@ARGV && $ARGV[0] eq '-ro') ? shift : '';	# -ro = Read-Only
our $subdir = shift;
die "$0: No subdirectory specified\n$Usage" unless defined $subdir;
$subdir = abs_path($subdir);
die "$0: Restricted subdirectory does not exist!\n" if $subdir ne '/' && !-d $subdir;

# The client uses "rsync -av -e ssh src/ server:dir/", and sshd on the server
# executes this program when .ssh/authorized_keys has 'command="..."'.
# For example:
# command="rrsync logs/client" ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAIEAzGhEeNlPr...
# command="rrsync -ro results" ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAIEAmkHG1WCjC...
#
# Format of the envrionment variables set by sshd:
# SSH_ORIGINAL_COMMAND=rsync --server          -vlogDtpr --partial . ARG # push
# SSH_ORIGINAL_COMMAND=rsync --server --sender -vlogDtpr --partial . ARGS # pull
# SSH_CONNECTION=client_addr client_port server_port

my $command = $ENV{SSH_ORIGINAL_COMMAND};
die "$0: Not invoked via sshd\n$Usage"	unless defined $command;
die "$0: SSH_ORIGINAL_COMMAND='$command' is not rsync\n" unless $command =~ s/^rsync\s+//;
our $am_sender = $command =~ /\s--sender\s/;
die "$0 -ro: sending to read-only server not allowed\n" if $ro && !$am_sender;

# These options are only the options that rsync might send to the
# server, and only in the arg format that the stock rsync uses.
### START of options data output by the cull-options script. ###
our $short_no_arg = 'CDHIKLORSWbcdglnoprtuvxz';
our $short_with_num = 'B';
# To disable a short-named option, add its letter to this string:
our $short_disabled = '';
# To disable a long-named option, change its value to a 0.  A value of -1
# means the arg doesn't need checking, a 2 means only check when receiving.
our %long_no_arg = (
  'copy-unsafe-links' => -1,
  'daemon' => -1,
  'delay-updates' => -1,
  'delete' => -1,
  'delete-after' => -1,
  'delete-before' => -1,
  'delete-during' => -1,
  'delete-excluded' => -1,
  'existing' => -1,
  'force' => -1,
  'from0' => -1,
  'fuzzy' => -1,
  'ignore-errors' => -1,
  'ignore-existing' => -1,
  'inplace' => -1,
  'list-only' => -1,
  'no-implied-dirs' => -1,
  'no-relative' => -1,
  'numeric-ids' => -1,
  'partial' => -1,
  'remove-sent-files' => $ro ? 0 : -1,
  'safe-links' => -1,
  'sender' => -1,
  'server' => -1,
  'size-only' => -1,
);
our %long_with_arg = (
  'bwlimit' => -1,
  'checksum-seed' => -1,
  'files-from' => 1,
  'log-format' => -1,
  'max-delete' => -1,
  'modify-window' => -1,
  'only-write-batch' => -1,
  'suffix' => -1,
  'timeout' => -1,
);
our %long_before_arg = (
  'backup-dir' => 2,
  'files-from' => 1,
  'max-size' => -1,
  'partial-dir' => 2,
  'temp-dir' => 2,
);
### END of options data output by the cull-options script. ###

if ($short_disabled ne '') {
    $short_no_arg =~ s/[$short_disabled]//go;
    $short_with_num =~ s/[$short_disabled]//go;
}

my(@opts, @args);
my $in_options = 1;
my $last_opt = '';
my $check_type;
foreach (split(/(?<!\\)\s+/, $command)) {
  if ($check_type) {
    s/\\(.)/$1/g;
    push(@opts, check_arg($last_opt, $_, $check_type));
    $check_type = 0;
  } elsif ($in_options) {
    s/\\(.)/$1/g;
    push(@opts, $_);
    if ($_ eq '.') {
      $in_options = 0;
    } else {
      next if /^-[$short_no_arg]+$/o || /^-[$short_with_num]\d+$/o;

      my($opt,$arg) = /^--([^=]+)(?:=(.*))?$/;
      my $disabled;
      if (defined $arg) {
	my $ct = $long_with_arg{$opt};
	if ($ct) {
	  $arg = check_arg($opt, $arg, $ct);
	  $opts[-1] =~ s/=.*/=$arg/;
	  next;
	}
	$disabled = defined $long_with_arg{$opt};
	$opt = "--$opt";
      } elsif (defined $opt) {
	if (defined $long_no_arg{$opt}) {
	  next if $long_no_arg{$opt};
	  $disabled = 1;
	} else {
	  $check_type = $long_before_arg{$opt};
	  if ($check_type) {
	    $last_opt = $opt;
	    next;
	  }
	  $disabled = defined $check_type;
	}
	$opt = "--$opt";
      } elsif ($short_disabled ne '') {
	$disabled = /^-[$short_no_arg]*([$short_disabled])/o;
	$opt = "-$1" if $disabled;
      }

      die "$0: option $opt has been disabled on this server.\n" if $disabled;
      die "$0: invalid rsync-command syntax or options\n";
    }
  } else {
    push(@args, $_);
  }
}

my $write_log = -f LOGFILE && open(LOG, '>>', LOGFILE);

chdir($subdir) or die "$0: Unable to chdir to $subdir: $!\n";

# Validate args to ensure they don't try to leave our restricted dir.
if ($subdir ne '/') {
  my @new;
  foreach (@args) {
    s#//+#/#g;			# Turn multiple slashes into a single slash
    s#^/##;			# Don't allow absolute paths
    s#^$#.#;			# Turn empty arg into "."
    die "Do not use .. in any path!\n" if m#(^|/)\.\.(/|$)#;
    push(@new, bsd_glob($_, GLOB_LIMIT | GLOB_NOCHECK | GLOB_BRACE | GLOB_QUOTE));
  }
  @args = @new;
}

@args = ( '.' ) if !@args;

if ($write_log) {
  my ($mm,$hh) = (localtime)[1,2];
  my $host = $ENV{SSH_CONNECTION} || 'unknown';
  $host =~ s/ .*//;			# Keep only the client's IP addr
  $host =~ s/^::ffff://;
  $host = gethostbyaddr(inet_aton($host),AF_INET) || $host;
  printf LOG "%02d:%02d %-13s [%s]\n", $hh, $mm, $host, "@opts @args";
  close LOG;
}

# Note: This assumes that the rsync protocol will not be maliciously hijacked.
exec(RSYNC, @opts, @args) or die "exec(rsync @opts @args) failed: $? $!";

sub check_arg
{
  my($opt, $arg, $type) = @_;
  if ($subdir ne '/' && $type > 0 && ($type < 2 || !$am_sender)) {
    $arg =~ s#//#/#g;
    die "Do not use .. in --$opt; anchor the path at the root of your restricted dir.\n"
      if $arg =~ m#(^|/)\.\.(/|$)#;
    $arg =~ s#^/#$subdir/#;
  }
  $arg;
}