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Message-ID: <CAHJtQJ7W8kgJ20s_uwt6TfGYprRr4rfM-i3CeM1FqedQXoYO7w@mail.gmail.com>
Date: Fri, 28 Nov 2014 07:45:50 -0800
From: Ingy dot Net <ingy@...y.net>
To: John Haxby <john.haxby@...cle.com>
Cc: oss-security@...ts.openwall.com, Kirill Simonov <xi@...olvent.net>,
Ingy döt Net <ingy@...n.org>
Subject: Re: libyaml / YAML-LibYAML DoS
Taking a look at this now. Please let me know if you've already found a
patch.
Ingy
On Fri, Nov 28, 2014 at 2:20 AM, John Haxby <john.haxby@...cle.com> wrote:
> On 28/11/14 05:57, Jonathan Gray wrote:
> > libyaml and the perl YAML-LibYAML (aka YAML-XS) module based
> > on the same code have an "impossible" assert that can be
> > triggered with the following yaml. This is a reduced testcase
> > of a crash found with the afl fuzzer.
> >
> > a: "
> > " b: true
> >
> > In other words a crash/denial of service with untrusted yaml input.
> > The libyaml author was contacted on the 21st and 27th of November.
> > No response has been received but the issue has independently been
> > reported publically since:
> >
> https://bitbucket.org/xi/libyaml/issue/10/wrapped-strings-cause-assert-failure
> >
> > [1] Parsing 'test.yaml': assertion "parser->simple_key_allowed ||
> !required" failed: file "scanner.c", line 1113, function
> "yaml_parser_save_simple_key"
> >
> > assert(parser->simple_key_allowed || !required); /* Impossible. */
>
> For what it's worth PyYAML 3.10 and 3.11 have exactly the same assertion:
>
> >>> import yaml
> >>> yaml.load("""
> ... abc:
> ... def: 'xxx
> ... ' ghi: 'yyy'
> ... """)
> Traceback (most recent call last):
>
> [...]
>
> assert self.allow_simple_key or not required
> AssertionError
>
> jch
>
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