[Python-Dev] Need help to fix HTTP Header Injection vulnerability (original) (raw)

Victor Stinner vstinner at redhat.com
Wed Apr 10 06:51:50 EDT 2019

Hi,

I dig into Python code history and the bug tracker. I would like to say that this issue is a work-in-progress since 2004. Different fixes have been pushed, but there are A LOT of open issues: https://bugs.python.org/issue30458#msg339846

I would suggest to discuss on https://bugs.python.org/issue30458 rather than here, just to avoid to duplicate discussions ;-)

Note: the whole class of issue (HTTP Header Injection) got at least 3 CVE: CVE-2016-5699, CVE-2019-9740, CVE-2019-9947. I changed bpo-30458 title to "[security][CVE-2019-9740][CVE-2019-9947] HTTP Header Injection (follow-up of CVE-2016-5699)".

Victor

Le mer. 10 avr. 2019 à 12:20, Wes Turner <wes.turner at gmail.com> a écrit :

1. Is there a library of URL / Header injection tests e.g. for fuzzing that we could generate additional test cases with or from? 2. Are requests.get() and requests.post() also vulnerable? 3. Despite the much-heralded UNIX pipe protocols' utility, filenames containing newlines (the de-facto line record delimiter) are possible: "file"$'\n'"name" Should filenames containing newlines and control characters require a kwarg to be non-None in order to be passed through unescaped to the HTTP request? On Wednesday, April 10, 2019, Karthikeyan <tir.karthi at gmail.com> wrote:

Thanks Gregory. I think it's a good tradeoff to ensure this validation only for URLs of http scheme. I also agree handling newline is little problematic over the years and the discussion over the level at which validation should occur also prolongs some of the patches. https://bugs.python.org/issue35906 is another similar case where splitlines is used but it's better to raise an error and the proposed fix could be used there too. Victor seemed to wrote a similar PR like linked one for other urllib functions only to fix similar attack in ftplib to reject newlines that was eventually fixed only in ftplib * https://bugs.python.org/issue30713 * https://bugs.python.org/issue29606 Search also brings multiple issues with one duplicate over another that makes these attacks scattered over the tracker and some edge case missing. Slightly off topic, the last time I reported a cookie related issue where the policy can be overriden by third party library I was asked to fix it in stdlib itself since adding fixes to libraries causes maintenance burden to downstream libraries to keep up upstream. With urllib being a heavily used module across ecosystem it's good to have a fix landing in stdlib that secures downstream libraries encouraging users to upgrade Python too. Regards, Karthikeyan S

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