SECURITY [CAN-2005-0448]: Rewrite File::Path::rmtree to avoid race condition which allows an attacker with write permission on directories in the tree being removed to make files setuid or to remove arbitrary files (see http://bugs.debian.org/286905 and http://bugs.debian.org/286922). Revised for 5.8.8-7etch6 to avoid failure when rmtree removes the current directory. diff --git a/lib/File/Path.pm b/lib/File/Path.pm index 2e41ff3..fd32b96 100644 --- a/lib/File/Path.pm +++ b/lib/File/Path.pm @@ -72,33 +72,17 @@ or C to remove it, or that it's skipping it. =item * -a boolean value, which if TRUE will cause C to -skip any files to which you do not have delete access -(if running under VMS) or write access (if running -under another OS). This will change in the future when -a criterion for 'delete permission' under OSs other -than VMS is settled. (defaults to FALSE) +a boolean value, which if FALSE (the default for non-root users) will +cause C to adjust the mode of directories (if required) prior +to attempting to remove the contents. Note that on interruption or +failure of C, directories may be left with more permissive +modes for the owner. =back It returns the number of files successfully deleted. Symlinks are simply deleted and not followed. -B There are race conditions internal to the implementation of -C making it unsafe to use on directory trees which may be -altered or moved while C is running, and in particular on any -directory trees with any path components or subdirectories potentially -writable by untrusted users. - -Additionally, if the third parameter is not TRUE and C is -interrupted, it may leave files and directories with permissions altered -to allow deletion (and older versions of this module would even set -files and directories to world-read/writable!) - -Note also that the occurrence of errors in C can be determined I -by trapping diagnostic messages using C<$SIG{__WARN__}>; it is not apparent -from the return value. - =head1 DIAGNOSTICS =over 4 @@ -172,111 +156,127 @@ sub mkpath { @created; } -sub rmtree { - my($roots, $verbose, $safe) = @_; - my(@files); - my($count) = 0; - $verbose ||= 0; - $safe ||= 0; +sub _rmtree; +sub _rmtree +{ + my ($path, $prefix, $up, $up_dev, $up_ino, $verbose, $safe) = @_; + my $up_name = $up eq '..' ? 'parent' : 'initial'; + + my ($dev, $ino) = lstat $path or return 0; + unless (-d _) + { + print "unlink $prefix$path\n" if $verbose; + unless (unlink $path) + { + carp "Can't remove file $prefix$path ($!)"; + return 0; + } - if ( defined($roots) && length($roots) ) { - $roots = [$roots] unless ref $roots; + return 1; } - else { - carp "No root path(s) specified\n"; - return 0; + + unless (chdir $path) + { + carp "Can't chdir to $prefix$path ($!)"; + return 0; } - my($root); - foreach $root (@{$roots}) { - if ($Is_MacOS) { - $root = ":$root" if $root !~ /:/; - $root =~ s#([^:])\z#$1:#; - } else { - $root =~ s#/\z##; - } - (undef, undef, my $rp) = lstat $root or next; - $rp &= 07777; # don't forget setuid, setgid, sticky bits - if ( -d _ ) { - # notabene: 0700 is for making readable in the first place, - # it's also intended to change it to writable in case we have - # to recurse in which case we are better than rm -rf for - # subtrees with strange permissions - chmod($rp | 0700, ($Is_VMS ? VMS::Filespec::fileify($root) : $root)) - or carp "Can't make directory $root read+writeable: $!" - unless $safe; - - if (opendir my $d, $root) { - no strict 'refs'; - if (!defined ${"\cTAINT"} or ${"\cTAINT"}) { - # Blindly untaint dir names - @files = map { /^(.*)$/s ; $1 } readdir $d; - } else { - @files = readdir $d; - } - closedir $d; - } - else { - carp "Can't read $root: $!"; - @files = (); - } + # avoid a race condition where a directory may be replaced by a + # symlink between the lstat and the chdir + my ($new_dev, $new_ino, $perm) = stat '.'; + unless ("$new_dev:$new_ino" eq "$dev:$ino") + { + croak "Directory $prefix$path changed before chdir, aborting"; + } - # Deleting large numbers of files from VMS Files-11 filesystems - # is faster if done in reverse ASCIIbetical order - @files = reverse @files if $Is_VMS; - ($root = VMS::Filespec::unixify($root)) =~ s#\.dir\z## if $Is_VMS; - if ($Is_MacOS) { - @files = map("$root$_", @files); - } else { - @files = map("$root/$_", grep $_!~/^\.{1,2}\z/s,@files); - } - $count += rmtree(\@files,$verbose,$safe); - if ($safe && - ($Is_VMS ? !&VMS::Filespec::candelete($root) : !-w $root)) { - print "skipped $root\n" if $verbose; - next; - } - chmod $rp | 0700, $root - or carp "Can't make directory $root writeable: $!" - if $force_writeable; - print "rmdir $root\n" if $verbose; - if (rmdir $root) { - ++$count; - } - else { - carp "Can't remove directory $root: $!"; - chmod($rp, ($Is_VMS ? VMS::Filespec::fileify($root) : $root)) - or carp("and can't restore permissions to " - . sprintf("0%o",$rp) . "\n"); - } - } - else { - if ($safe && - ($Is_VMS ? !&VMS::Filespec::candelete($root) - : !(-l $root || -w $root))) - { - print "skipped $root\n" if $verbose; - next; - } - chmod $rp | 0600, $root - or carp "Can't make file $root writeable: $!" - if $force_writeable; - print "unlink $root\n" if $verbose; - # delete all versions under VMS - for (;;) { - unless (unlink $root) { - carp "Can't unlink file $root: $!"; - if ($force_writeable) { - chmod $rp, $root - or carp("and can't restore permissions to " - . sprintf("0%o",$rp) . "\n"); - } - last; - } - ++$count; - last unless $Is_VMS && lstat $root; - } + $perm &= 07777; + my $nperm = $perm | 0700; + unless ($safe or $nperm == $perm or chmod $nperm, '.') + { + carp "Can't make directory $prefix$path read+writeable ($!)"; + $nperm = $perm; + } + + my $count = 0; + if (opendir my $dir, '.') + { + my $entry; + while (defined ($entry = readdir $dir)) + { + next if $entry =~ /^\.\.?$/; + $entry =~ /^(.*)$/s; $entry = $1; # untaint + $count += _rmtree $entry, "$prefix$path/", '..', $dev, $ino, + $verbose, $safe; } + + closedir $dir; + } + + # restore directory permissions if required (in case the rmdir + # below fails) now, while we're still in the directory and may do + # so without a race via '.' + unless ($nperm == $perm or chmod $perm, '.') + { + carp "Can't restore permissions on directory $prefix$path ($!)"; + } + + # don't leave the caller in an unexpected directory + unless (chdir $up) + { + croak "Can't return to $up_name directory from $prefix$path ($!)"; + } + + # ensure that a chdir .. didn't take us somewhere other than + # where we expected (see CVE-2002-0435) + unless (($new_dev, $new_ino) = stat '.' + and "$new_dev:$new_ino" eq "$up_dev:$up_ino") + { + croak "\u$up_name directory changed since entering $prefix$path"; + } + + print "rmdir $prefix$path\n" if $verbose; + if (rmdir $path) + { + $count++; + } + else + { + carp "Can't remove directory $prefix$path ($!)"; + } + + return $count; +} + +sub rmtree +{ + my ($p, $verbose, $safe) = @_; + $p = [] unless defined $p and length $p; + $p = [ $p ] unless ref $p; + my @paths = grep defined && length, @$p; + + # default to "unsafe" for non-root (will chmod dirs) + $safe = $> ? 0 : 1 unless defined $safe; + + unless (@paths) + { + carp "No root path(s) specified"; + return; + } + + opendir my $oldpwd, '.' or do { + carp "Can't fetch initial working directory"; + return; + }; + + my ($dev, $ino) = stat '.' or do { + carp "Can't stat initial working directory"; + return; + }; + + my $count = 0; + for my $path (@paths) + { + $count += _rmtree $path, '', $oldpwd, $dev, $ino, $verbose, $safe; } $count;