Bug 915962 (CVE-2013-1769) - CVE-2013-1769 telepathy-gabble: NULL pointer dereference when trying to hash caps containing pathological data forms
Summary: CVE-2013-1769 telepathy-gabble: NULL pointer dereference when trying to hash ...
Alias: CVE-2013-1769
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
Depends On: 915963 915966 917769
Blocks: 916244
TreeView+ depends on / blocked
Reported: 2013-02-26 21:21 UTC by Kurt Seifried
Modified: 2021-02-17 08:00 UTC (History)
5 users (show)

Fixed In Version: telepathy-gabble 0.16.5, telepathy-gabble 0.17.3
Doc Type: Bug Fix
Doc Text:
Clone Of:
Last Closed: 2013-07-25 20:48:12 UTC

Attachments (Terms of Use)

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Description Kurt Seifried 2013-02-26 21:21:16 UTC
Will Thompson (will.thompson@collabora.co.uk) reports:

Calculating a XEP-0115 hash involves sorting the fields of data forms in the 
contact's capabilities according to their field name. 
wocky_caps_hash_compute_from_lists() does this using this function:

  wocky_data_form_field_cmp (const WockyDataFormField *left,
      const WockyDataFormField *right)
    return strcmp (left->var, right->var);

This will obviously crash if either ->var is NULL, but WockyDataForm validates 
forms it parses so this shouldn't happen, right? Unfortunately, 
http://xmpp.org/extensions/xep-0004.html#protocol-field says:

> If the <field/> element type is anything other than "fixed" (see below), it
> MUST possess a 'var' attribute that uniquely identifies the field in the 
> context of the form (if it is "fixed", it MAY possess a 'var' attribute).

And WockyDataForm implements this correctly:

  var = wocky_node_get_attribute (node, "var");
  if (var == NULL && type != WOCKY_DATA_FORM_FIELD_TYPE_FIXED)
      DEBUG ("field node doesn't have a 'var' attribute; ignoring");
      return FALSE;

So we have a remotely-triggered DoS: send Gabble a <presence> with a caps hash;
include a form with an anonymous fixed field in the reply; boom. Since anyone 
can send presence to anyone else, and Gabble always looks up any caps it sees 
in any presences it receives. (Note that this is a presence leak, too; another 
bug, I think.)

I have some fixes; patches to follow. I will also suggest that 
http://xmpp.org/extensions/xep-0115.html be updated to mention this.

External references:


Comment 1 Kurt Seifried 2013-02-26 21:22:15 UTC
Created telepathy-gabble tracking bugs for this issue

Affects: fedora-all [bug 915963]

Comment 2 Kurt Seifried 2013-02-26 21:23:04 UTC
Created telepathy-gabble tracking bugs for this issue

Affects: epel-6 [bug 915966]

Comment 4 Fedora Update System 2013-03-19 19:59:33 UTC
telepathy-gabble-0.16.5-1.fc18 has been pushed to the Fedora 18 stable repository.  If problems still persist, please make note of it in this bug report.

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