IRSSI-SA-2016 Irssi Security Advisory [1]
=========================================
heap corruption and missing boundary checks
CVE-2016-7044, CVE-2016-7045

Description
-----------

Gabriel Campana and Adrien Guinet from Quarkslab reported two remote
crash and heap corruption vulnerabilites in Irssi's format parsing code.

They also provided us with proof of concept exploit code and patches to
fix those issues.

(a) Remote crash and heap corruption in format parsing code found by
    Gabriel Campana and Adrien Guinet from Quarkslab. (CWE-20, CWE-823,
    CWE-126, CWE-122)

    CVE-2016-7044 [2] was assigned to this issue.

(b) Remote crash and heap corruption in format parsing code found by
    Gabriel Campana and Adrien Guinet from Quarkslab. (CWE-20, CWE-823,
    CWE-126, CWE-122)

    CVE-2016-7045 [3] was assigned to this issue.


Impact
------

Remote crash and heap corruption. Remote code execution seems difficult
since only Nuls are written.


Affected versions
-----------------

(a) Irssi 0.8.17 and later, only when compiled with true-color enabled.

(b) Irssi 0.8.17 and later


Fixed in
--------

Irssi 0.8.20


Recommended action
------------------

Upgrade to Irssi 0.8.20. Irssi 0.8.20 is a maintenance release without
any new features.

After installing the updated packages, one can issue the /upgrade
command to load the new binary. TLS connections will require /reconnect.


Fallback action
---------------

Distributions which need to remain on Irssi 0.8.17 are strongly urged
to apply the patch and provide updated packages.

Those who cannot upgrade right now, but with Perl support enabled in
their Irssi, can load the following script and add it to
~/.irssi/scripts/autorun as a first aid to mitigating these issues:

https://irssi.org/security/sa_patch.pl


Patch
-----

https://github.com/irssi/irssi/commit/295a4b77f07f14602eeaa371f00ddbf09910c82b


Discussion
----------

Based on analysis Provided by Gabriel Campana and Adrien Guinet from
Quarkslab.

(a) Bug 1

    The unformat_24bit_color() function is called by
    format_send_to_gui() to decode 24bit color codes into their
    components. The pointer is advanced unconditionally without checking
    if a complete code was supplied.

    Thus, after the return of unformat_24bit_color(), ptr might be
    invalid and point out of the buffer.

(b) Bug 2

    The format_send_to_gui() function does not validate the length of
    the string before incrementing the `ptr' pointer in all cases.

    If that happens, the pointer `ptr' can be incremented twice and
    thus end past the boundaries of the original `dup' buffer.


References
----------

[1] https://irssi.org/security/irssi_sa_2016.txt
[2] https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-7044
[3] https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-7045