Date: Thu, 1 Aug 2013 14:03:35 +0000 From: isis agora lovecruft <isis@...project.org> To: Donald Stufft <donald@...fft.io> Cc: kseifried@...hat.com, oss-security@...ts.openwall.com, isis@...project.org, cve-assign@...re.org Subject: Re: Requesting CVE-ID(s) for Python's pip Donald Stufft transcribed 14K bytes: > > On Jul 30, 2013, at 2:29 AM, Kurt Seifried <kseifried@...hat.com> wrote: > > > Signed PGP part > > On 07/26/2013 09:46 AM, Donald Stufft wrote: > > > > > > On Jul 26, 2013, at 8:03 AM, isis agora lovecruft > > > <isis@...project.org> wrote: > > > > > >> I would also like to request CVE assignment(s) for two issues in > > >> pip (https://github.com/pypa/pip/), related to Donald Stufft's. > > >> > > >> First issue: ------------ Python's pip versions 1.4.x and earlier > > >> are vulnerable to an Arbitrary Code Execution Attack due to > > >> incorrect regexp parsing of external download links in the > > >> following functions in pip/index.py: > > >> > > >> * PackageFinder._get_pages() > > >> https://github.com/pypa/pip/blob/1.3.X/pip/index.py#L232 * > > >> PackageFinder._sort_links() > > >> https://github.com/pypa/pip/blob/1.3.X/pip/index.py#L272 * > > >> PackageFinder._package_versions() > > >> https://github.com/pypa/pip/blob/1.3.X/pip/index.py#L285 * > > >> PackageFinder._link_package_versions() > > >> https://github.com/pypa/pip/blob/1.3.X/pip/index.py#L290 > > >> > > >> Which allow an attacker with the ability to Man-in-the-Middle > > >> external package URIs (which often include external HTTP URIs, > > >> and can include the module author's personal website, see > > >> https://github.com/pypa/pip/commit/a3584d176697bd4c83390de1857679d44389e00d#L0L265) > > >> > > >> > > to specify an arbitrarily high package version number and gain code > > >> execution. > > >> > > >> Uptream bugtracker reports: > > >> https://github.com/pypa/pip/issues/425#issuecomment-20639993 > > >> https://github.com/pypa/pip/issues/425#issuecomment-20640890 > > >> > > >> Other mentions: > > >> https://github.com/pypa/pip/commit/9ccd5f0bb37508f03e6a19be58af7384eede2157 > > >> > > >> > > https://paste.debian.net/7309/ > > >> > > >> This issue is fixed in pip>=1.5.x by Donald Stufft in the > > >> following commits: > > >> https://github.com/pypa/pip/commit/0e1da584f418ae0088b43d01248572e2ff53d3a1 > > >> > > >> > > https://github.com/pypa/pip/commit/9ccd5f0bb37508f03e6a19be58af7384eede2157 > > > > > > I'm not sure I understand this one. Is this just the external urls? > > > Technically it wasn't a problem with the regexp's they worked fine. > > > It was just bad behavior inherited from legacy systems. 1.4.x > > > defaults to allowing them but enables people to turn them off, > > > 1.5.x will disallow them by default. > > > > > > 1.3.x and earlier allowed them and offered no way to disable them. > > > > So it sounds like 1.3.x was definitely vulnerable to this with no way > > to disable it, 1.4 was vulnerable by default but could be made safe, > > and 1.5 is vulnerable but safe by default, is that correct? Yes, this is correct. > Yes, assuming this is the unverified external link problem which I believe > it is, except 1.5 is a future version that hasn't happened yet so it's "will" b > safe by default. As a pip developer, again assuming my understanding > of the request is correct, I do believe a CVE is warranted here. > > > >> Second issue: ------------- Python's pip versions 1.5.x and > > >> earlier use MD5 hashes for verification of package integrity > > >> against PyPI (which defaults to providing MD5). > > > > > > Strictly speaking pip doesn't default to any hash. It just uses the > > > hash given to it. Prior to 1.2 it only allowed MD5 but since the > > > release of 1.2 it has allowed any of the guaranteed hashes in > > > python's hash lib. > > > > > > See: https://github.com/pypa/pip/pull/467 > > > > > > Setuptools has also historically only allowed MD5 but has recently > > > with version 0.9+ enabled similar abilities to setuptools to enable > > > the use of any available hashes as well. Distribute (a fork of > > > setuptools which has now been merged back into setuptools) only > > > supports MD5 in it's older releases. > > > > I'm not sure in this case MD5 alone is a security vulnerability, I > > think previously it had been decided that just because it uses MD5 > > wasn't ernough to get a CVE, it had to have some specific use that > > made MD5 a problem. I wasn't sure if this warranted a CVE either. And, to be fair, Donald Stufft points out that pip can handle alternate ciphers just fine, it is pypi.python.org which uses MD5 by default. > > OTOH DES is at this point worthy of a CVE since > > you can crack it in a reasonable amount of time on AWS/etc for a few > > hundred bucks or less. Personally I would assign a CVE to everything > > using MD5 by default to try and help kill it off, but that would be a > > lot of CVEs. Marc Stevens recently published a paper on using probabilistic conditionals to control differential computation for two-block MD5 collisions, claiming that, on a 3GHz Pentium 4, "with a reasonable probability a collision is found within mere seconds, allowing for instance an attack during the execution of a protocol".  > This one is the one I'm not really sure about. Pip has supported any hash for > longer then they've offered verified downloads so it's certainly not a problem > there (or rather if it is a problem it's overshadowed by the fact that it wasn't > using TLS or if people manually configured it to do so it wouldn't' verify it). > > Setuptools did only support MD5 until recently (and has versions that both > support TLS verification and only MD5 as a hash) however that doesn't > really buy anything until the index server serves a different hash. Currently > PyPI (which I'm also an admin on) continues to serve MD5 and going by > the thread on that discussion list it appears it will continue to do in the future. References : Stevens, Marc. "Fast Collision Attack on MD5." IACR Cryptology ePrint Archive 2006 (2006): 104. http://crppit.epfl.ch/documentation/Hash_Function/Examples/Code_Project/Documentation/104.pdf -- ♥Ⓐ isis agora lovecruft _________________________________________________________ GPG: 4096R/A3ADB67A2CDB8B35 Current Keys: https://blog.patternsinthevoid.net/isis.txt Download attachment "signature.asc" of type "application/pgp-signature" (916 bytes)
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