oss-sec mailing list archives
Re: CVE request: python-gnupg before 0.3.5 shell injection
From: Florian Weimer <fweimer () redhat com>
Date: Tue, 04 Feb 2014 11:19:25 +0100
On 02/04/2014 11:04 AM, Henri Salo wrote:
On Tue, Feb 04, 2014 at 10:35:46AM +0100, Hanno Böck wrote:python-gnupg 0.3.5 lists in the changelog: "Added improved shell quoting to guard against shell injection." Sounds like a severe security issue, but further info is lacking.Diff attached. New function shell_quote() seems to represent major changes to shell input quoting against unsafe input. +# We use the test below because it works for Jython as well as CPython +if os.path.__name__ == 'ntpath': + # On Windows, we don't need shell quoting, other than worrying about + # paths with spaces in them. + def shell_quote(s): + return '"%s"' % s +else: + # Section copied from sarge + + # This regex determines which shell input needs quoting + # because it may be unsafe + UNSAFE = re.compile(r'[^\w%+,./:=@-]') + + def shell_quote(s): + """ + Quote text so that it is safe for Posix command shells. + + For example, "*.py" would be converted to "'*.py'". If the text is + considered safe it is returned unquoted. + + :param s: The value to quote + :type s: str (or unicode on 2.x) + :return: A safe version of the input, from the point of view of Posix + command shells + :rtype: The passed-in type + """ + if not isinstance(s, string_types): + raise TypeError('Expected string type, got %s' % type(s)) + if not s: + result = "''" + elif len(s) >= 2 and (s[0], s[-1]) == ("'", "'"): + result = '"%s"' % s.replace('"', r'\"') + elif not UNSAFE.search(s): + result = s + else: + result = "'%s'" % s.replace("'", "'\"'\"'") + return result + + # end of sarge code
This fix appears to be incomplete: >>> print shell_quote("'$(touch /tmp/I_was_here'") "'$(touch /tmp/I_was_here'" [fweimer@oldenburg ~]$ echo "'$(touch /tmp/I_was_here)'" '' [fweimer@oldenburg ~]$ ls -l /tmp/I_was_here -rw-rw-r--. 1 fweimer fweimer 0 Feb 4 11:12 /tmp/I_was_hereThe proper way (at least if your shell runs in a UTF-8 or ISO-8859 locale) to escape shell arguments is to wrap them in '', after replacing embedded ' characters with the four character sequence '\''. However, using the subprocess module with shell=False (the default) is strongly preferred.
In both cases, you need to make sure that you prevent option injection through positional arguments. With a GNU getopt-derived command line parser, option processing can be terminated with a -- argument. (Warning: GnuPG does not strictly follow GNU command line processing conventions.)
Is anyone in touch with the python-gpg folks and can rely this information? Thanks.
-- Florian Weimer / Red Hat Product Security Team
Current thread:
- CVE request: python-gnupg before 0.3.5 shell injection Hanno Böck (Feb 04)
- Re: CVE request: python-gnupg before 0.3.5 shell injection Henri Salo (Feb 04)
- Re: CVE request: python-gnupg before 0.3.5 shell injection Florian Weimer (Feb 04)
- Re: CVE request: python-gnupg before 0.3.5 shell injection Henri Salo (Feb 04)
- Re: CVE request: python-gnupg before 0.3.5 shell injection Henri Salo (Feb 04)
- Re: CVE request: python-gnupg before 0.3.5 shell injection Florian Weimer (Feb 04)
- Re: CVE request: python-gnupg before 0.3.5 shell injection Vinay Sajip (Feb 05)
- Re: Re: CVE request: python-gnupg before 0.3.5 shell injection Florian Weimer (Feb 05)
- Re: CVE request: python-gnupg before 0.3.5 shell injection Vinay Sajip (Feb 05)
- Re: CVE request: python-gnupg before 0.3.5 shell injection Florian Weimer (Feb 04)
- Re: CVE request: python-gnupg before 0.3.5 shell injection Henri Salo (Feb 04)
- Re: CVE request: python-gnupg before 0.3.5 shell injection cve-assign (Feb 09)
- Re: Re: CVE request: python-gnupg before 0.3.5 shell injection Simon McVittie (Feb 10)