WINDOWS PORT MAP WINDOWSWhen Windows NFS responds to an NLM call in an asynchronous manner, the NlmGetClientAddressAndConnection() function is called. More specifically, the vulnerability is due to incorrect handling of the Universal Address field returned in GETADDR RPC replies. The format for the returned Universal Address is XDR_String, which has the following format:Ī stack buffer overflow vulnerability exists in Windows Network File System. The reply to this RPC call contains the Universal Address associated with the callee. One of the procedures supported by the RPCBIND program when Program Version is set to 3 or 4, is GETADDR, which is procedure number 3. It supports multiple RPC procedures, which can be specified in the Procedure field in the RPC message. Windows implements the RPCBIND protocol via RPC with Program type set to 100000. Only the portmapper service and NFS service have standard ports of 1 respectively. Standard RPC program numbers have been defined and maintained by IANA and they include portmapper (100000), nfs (100003), mount daemon (100005) and hundreds of other less commonly used programs. to obtain a port on which the RPC service is available, and connects to the desired RPC service. A client that wishes to issue RPC calls connects to the Port Mapper, uses various RPC calls such as GETPORT, GETADDR etc. Briefly, the way it works is that when a program wishes to use RPC, it registers its ports with the host's Port Mapper. The RPCBIND program converts RPC program numbers into universal addresses, which can then be used by programs to communicate over UDP or TCP. Microsoft Windows runs the RPCBIND RPC program, which implements the Port Mapper protocol, documented in RFC 1833. The Fragment itself contains the XDR packet. The most significant bit of the Fragment header indicates whether the packet is the last fragment, and the remaining 31 bits are the length of the Fragment that follows. Over TCP, XDR packets are preceded by a Fragment header (as illustrated in the following table). Over UDP, the XDR packet is contained within the UDP payload. ONC RPC uses XDR packets, which can be transmitted over UDP or TCP. Similar to NFS, NLM also uses ONC RPC to exchange control messages. The NLM protocol supports both synchronous and asynchronous procedures to implement locking and file-sharing functionality. Since NFS versions 2 and 3 are stateless protocols, the NLM protocol was developed to manage the state of locks on files stored on NFS shares. The Network Lock Manager ( NLM) protocol is an extension of NFS versions 2 and 3, which provides a System V style of advisory file and record locking over the network. ONC RPC was originally developed by Sun Microsystems and can also be referred to as Sun RPC. NFS uses Open Network Computing (ONC) Remote Procedure Call (RPC) to exchange control messages. Additionally, IP/UID/GID/Kerberos security can be used. Different access levels and permissions can be set on the share, such as read-write and read-only. NFS allows users to access remote file shares in the same way that the local file system is accessed. Version 4 was developed by the IETF and is documented in RFC 3010 (released December 2000) and revised in RFC 3530 (released April 2003) and RFC 7530 (released March 2015). NFS is a network file system protocol originally developed by Sun Microsystems in 1984. One of these modules is called Network File System (NFS). Microsoft Windows ships with several network features designed to communicate and interact with non-Windows files shares. Unsuccessful exploitation results in a crash of the target system. WINDOWS PORT MAP CODESuccessful exploitation may result in arbitrary code execution under the context of SYSTEM. The vulnerability is due to improper handling of crafted RPC responses to Portmap requests made by the Network Lock Manager (NLM) RPC program.Ī remote attacker can exploit this vulnerability by sending malicious RPC calls to a target server. A stack buffer overflow vulnerability exists in Windows Network File System.
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