Attachment 14648 Details for Bug 11879 – rrysnc patch to avoid following symlinks out of the restricted dir

[patch] rrysnc patch to avoid following symlinks out of the restricted dir

rrsync.patch (text/plain), 2.28 KB, created by Nick Cleaton on 2018-11-13 06:23:43 UTC

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Creator: Nick Cleaton

Created: 2018-11-13 06:23:43 UTC

Size: 2.28 KB

patch

obsolete

>diff --git a/support/rrsync b/support/rrsync
>old mode 100644
>new mode 100755
>index 9195aa2..0d55474
>--- a/support/rrsync
>+++ b/support/rrsync
>@@ -8,11 +8,13 @@ use strict;
> use Socket;
> use Cwd 'abs_path';
> use File::Glob ':glob';
>+use Fcntl ':flock';
> 
> # You may configure these values to your liking.  See also the section
> # of options if you want to disable any options that rsync accepts.
> use constant RSYNC => '/usr/bin/rsync';
> use constant LOGFILE => 'rrsync.log';
>+use constant LOCKFILE => '.rrsync.lock';
> 
> my $Usage = <<EOM;
> Use 'command="$0 [-ro|-wo] SUBDIR"'
>@@ -54,6 +56,12 @@ our $am_sender = $command =~ /^--server\s+--sender\s/; # Restrictive on purpose!
> die "$0 sending to read-only server not allowed\n" if $only eq 'r' && !$am_sender;
> die "$0 reading from write-only server not allowed\n" if $only eq 'w' && $am_sender;
> 
>+# A lock file prevents an attacker from using one rrsync instance to make
>+# filesystem changes underneath another running instance, tricking it into
>+# leaving the restricted dir.
>+open(LOCK_FH, '>>', LOCKFILE) or die "open lockfile: $!";
>+flock LOCK_FH, ($am_sender ? LOCK_SH : LOCK_EX) or die "lock lockfile: $!";
>+
> ### START of options data produced by the cull_options script. ###
> 
> # These options are the only options that rsync might send to the server,
>@@ -216,6 +224,11 @@ die "$0: invalid rsync-command syntax or options\n" if $in_options;
> 
> @args = ( '.' ) if !@args;
> 
>+for (@args) {
>+  die "$0: do not use .. in any path!\n" if m{(^|/)\.\.(/|$)};
>+  die "$0: arg not under subdir\n" unless relpath_abs_is_under($_, $subdir);
>+}
>+
> if ($write_log) {
>   my ($mm,$hh) = (localtime)[1,2];
>   my $host = $ENV{SSH_CONNECTION} || 'unknown';
>@@ -227,7 +240,20 @@ if ($write_log) {
> }
> 
> # Note: This assumes that the rsync protocol will not be maliciously hijacked.
>-exec(RSYNC, @opts, @args) or die "exec(rsync @opts @args) failed: $? $!";
>+exit system(RSYNC, @opts, '--', @args);
>+
>+sub relpath_abs_is_under {
>+  my ($relpath, $under_abspath) = @_;
>+  die "relpath must be a relative path" if $relpath =~ m{^/};
>+  for (;;) {
>+    my $a = abs_path($relpath);
>+    if (defined $a) {
>+      return $a =~ m{^\Q$under_abspath\E(/|$)};
>+    }
>+    die "abs_path failed on .: $!" if $relpath eq '.';
>+    $relpath =~ s{/[^/]*$}{} or $relpath = '.';
>+  }
>+}
> 
> sub check_arg
> {

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Attachments on bug 11879: 12132 | 14648 | 14658 | 14662