From: Daniel Kahn Gillmor Date: Sat, 1 Aug 2009 16:50:14 +0000 (-0400) Subject: added new perl script to check permissions. X-Git-Tag: monkeysphere_0.26~9 X-Git-Url: https://codewiz.org/gitweb?a=commitdiff_plain;h=3008df4948abb4b3eb6f6915f3d6b06b323a0097;p=monkeysphere.git added new perl script to check permissions. --- diff --git a/src/share/checkperms b/src/share/checkperms new file mode 100755 index 0000000..9247832 --- /dev/null +++ b/src/share/checkperms @@ -0,0 +1,101 @@ +#!/usr/bin/perl -T + +# checkperms: ensure as best we can that a given file can only be +# modified by the given user (or the superuser, naturally). This +# means checking file ownership and permissions all the way back to +# the root directory. Pass the file by its absolute path. + +# example invocation: + +# checkperms dkg /home/dkg/.monkeysphere/authorized_user_ids + +# return values: zero if we believe the file and path can only be +# modified by the user. non-zero otherwise. + +# see StrictModes in sshd_config(5) (and its implementation in +# OpenSSH's secure_filename() in auth.c) for the initial +# inspiration/rationale for this code. + +# Author: +# Daniel Kahn Gillmor + +# Started on: 2009-07-31 11:10:16-0400 + +# License: GPL v3 or later + +use strict; + +use Cwd qw(realpath); # found in debian in perl-base +use File::stat; # found in debian in perl-modules +use User::pwent; # found in debian in perl-modules +use Fcntl qw(:mode); # for S_IS* functions (in perl-base) +use File::Basename; # for dirname (in perl-modules) + +my $username = shift; +my $path = shift; + +defined($username) or die "You must pass a username and an absolute path."; +defined($path) or die "You must pass a username and an absolute path."; + +my $pw = getpwnam($username) or die "no such user $username"; +$path =~ m#^/# or die "path was not absolute (did not start with /)"; + +sub debug { + if ($ENV{MONKEYSPHERE_LOG_LEVEL} eq 'DEBUG') { + # FIXME: prefix with ms: + printf STDERR @_; + } +} + +## return undef if permissions are OK. otherwise return an error string +sub permissions_ok { + my $user = shift; + my $path = shift; + + # if we can't even stat the path, the permissions are not ok: + my $stat = lstat($path) or return "cannot stat '$path'\n"; + + while (S_ISLNK($stat->mode)) { + my $newpath = realpath($path) or return "cannot trace symlink '$path'\n"; + debug("tracing link %s to %s\n", $path, $newpath); + $path = $newpath; + $stat = lstat($path) or return "cannot stat '$path'\n"; + } + debug("checking '%s'\n", $path); + + if (($stat->uid != $user->uid) && + ($stat->uid != 0)) { + return sprintf("improper ownership on '%s':\nowner ID %d is neither %s (ID %d) nor the superuser\n", + $path, $stat->uid, $user->name, $user->uid); + } + + if (S_IWGRP & $stat->mode) { + return sprintf("improper group writability on '%s'\n", $path); + } + + if (S_IWGRP & $stat->mode) { + return sprintf("improper group writability on '%s'\n", $path); + } + + if (S_IWOTH & $stat->mode) { + return sprintf("improper other writability on '%s'\n", $path); + } + + my $nextlevel = dirname($path); + if ($path eq $nextlevel) { # we bottom out at the root (/ in UNIX) + return undef; + } + return permissions_ok($user, $nextlevel); +} + +my $err = permissions_ok($pw, $path); + +if (defined($err)) { + $err =~ s/^/ms: /; + printf(STDERR $err); + + exit(1); +} else { + exit(0); +} +