Subject: [ASA-201701-21] libgit2: multiple issues

Arch Linux Security Advisory ASA-201701-21
==========================================

Severity: High
Date    : 2017-01-15
CVE-ID  : CVE-2016-10128 CVE-2016-10129 CVE-2016-10130
Package : libgit2
Type    : multiple issues
Remote  : Yes
Link    : https://security.archlinux.org/AVG-131

Summary
=======

The package libgit2 before version 1:0.24.6-1 is vulnerable to multiple
issues including arbitrary code execution, insufficient validation and
denial of service.

Resolution
==========

Upgrade to 1:0.24.6-1.

# pacman -Syu "libgit2>=1:0.24.6-1"

The problems have been fixed upstream in version 0.24.6.

Workaround
==========

None.

Description
===========

- CVE-2016-10128 (arbitrary code execution)

Each packet line in the Git protocol is prefixed by a four-byte length
of how much data will follow, which we parse in `git_pkt_parse_line`.
The transmitted length can either be equal to zero in case of a flush
packet or has to be at least of length four, as it also includes the
encoded length itself. Not checking this may result in a buffer
overflow as it directly passes the length to functions which accept a
`size_t` length as parameter.
The issue is fixed by verifying that non-flush packets have at least a
length of `PKT_LEN_SIZE`.

- CVE-2016-10129 (denial of service)

The Git protocol does not specify what should happen in the case of an
empty packet line (that is a packet line "0004"). currently it
indicates success, but does not return a packet in the case where an
empty line is hit. The smart protocol was not prepared to handle such
packets in all cases, though, resulting in a `NULL` pointer
dereference. The issue is fixed by returning an error instead.

- CVE-2016-10130 (insufficient validation)

An issue has been discovered when checking certificate validity before
clobbering the error variable. A valid parameter is provided to
indicate whether the native cryptographic library considered the
certificate to be correct. This parameter is always 1/true before the
fix leading to a possible man-in-the-middle (MITM).

Impact
======

A remote attacker is able to perform a man-in-the-middle attack, crash
the application or possibly execute arbitrary code on the affected
host.

References
==========

http://www.openwall.com/lists/oss-security/2017/01/11/6
https://github.com/libgit2/libgit2/commit/66e3774d279672ee51c3b54545a79d20d1ada834
https://github.com/libgit2/libgit2/commit/2fdef641fd0dd2828bd948234ae86de75221a11a
https://github.com/libgit2/libgit2/commit/9a64e62f0f20c9cf9b2e1609f037060eb2d8eb22
https://security.archlinux.org/CVE-2016-10128
https://security.archlinux.org/CVE-2016-10129
https://security.archlinux.org/CVE-2016-10130