* it uses RAW sockets, it must be installed SUID or run as 'root'.
* In order to keep the security risk of the resulting SUID binary
* minimal, the program ONLY opens the RAW socket with root
- * priviledges, then drops them and only then starts to process
+ * privileges, then drops them and only then starts to process
* command line arguments. The code also does not link against
* any shared libraries (except libc) and is strictly minimal
* (except for checking for errors). The following list of people
/**
* Must match IP given in the server.
*/
-#define DUMMY_IP "1.2.3.4"
+#define DUMMY_IP "192.0.2.86"
+
+#define NAT_TRAV_PORT 22225
struct ip_packet
{
uint8_t code;
uint16_t checksum;
uint32_t reserved;
+
};
-
+
+struct icmp_echo_packet
+{
+ uint8_t type;
+ uint8_t code;
+ uint16_t checksum;
+ uint32_t reserved;
+ uint32_t data;
+};
+
+struct udp_packet
+{
+ uint16_t src_port;
+
+ uint16_t dst_port;
+
+ uint32_t length;
+};
+
static int rawsock;
static struct in_addr dummy;
-static struct in_addr target;
-
+static uint32_t port;
static uint16_t
calc_checksum(const uint16_t *data,
static void
make_echo (const struct in_addr *src_ip,
- struct icmp_packet *echo)
+ struct icmp_echo_packet *echo, uint32_t num)
{
- memset(echo, 0, sizeof(struct icmp_packet));
+ memset(echo, 0, sizeof(struct icmp_echo_packet));
echo->type = ICMP_ECHO;
echo->code = 0;
echo->reserved = 0;
echo->checksum = 0;
+ echo->data = htons(num);
echo->checksum = htons(calc_checksum((uint16_t*)echo,
- sizeof (struct icmp_packet)));
+ sizeof (struct icmp_echo_packet)));
+}
+
+
+/**
+ * Send an ICMP message to the target.
+ *
+ * @param my_ip source address
+ * @param other target address
+ */
+static void
+send_icmp_udp (const struct in_addr *my_ip,
+ const struct in_addr *other)
+{
+ struct ip_packet ip_pkt;
+ struct icmp_packet icmp_pkt;
+ struct udp_packet udp_pkt;
+
+ struct sockaddr_in dst;
+ char packet[sizeof(ip_pkt) * 2 + sizeof(icmp_pkt) * 2 + sizeof(uint32_t)];
+
+ size_t off;
+ int err;
+
+ /* ip header: send to (known) ip address */
+ off = 0;
+ memset(&ip_pkt, 0, sizeof(ip_pkt));
+ ip_pkt.vers_ihl = 0x45;
+ ip_pkt.tos = 0;
+ ip_pkt.pkt_len = htons(sizeof (packet));
+ ip_pkt.id = htons(256);
+ ip_pkt.flags_frag_offset = 0;
+ ip_pkt.ttl = 128;
+ ip_pkt.proto = IPPROTO_ICMP;
+ ip_pkt.checksum = 0;
+ ip_pkt.src_ip = my_ip->s_addr;
+ ip_pkt.dst_ip = other->s_addr;
+ ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (ip_pkt)));
+ memcpy(&packet[off], &ip_pkt, sizeof(ip_pkt));
+ off += sizeof(ip_pkt);
+
+ /* ip header of the presumably 'lost' udp packet */
+ ip_pkt.vers_ihl = 0x45;
+ ip_pkt.tos = 0;
+ ip_pkt.pkt_len = (sizeof (struct ip_packet) + sizeof (struct icmp_echo_packet));
+
+ icmp_pkt.type = 11; /* TTL exceeded */
+ icmp_pkt.code = 0;
+ icmp_pkt.checksum = 0;
+ icmp_pkt.reserved = 0;
+ memcpy(&packet[off], &icmp_pkt, sizeof(icmp_pkt));
+ off += sizeof(icmp_pkt);
+
+ /* build inner IP header */
+ memset(&ip_pkt, 0, sizeof(ip_pkt));
+ ip_pkt.vers_ihl = 0x45;
+ ip_pkt.tos = 0;
+ ip_pkt.pkt_len = htons(sizeof (ip_pkt) + sizeof(udp_pkt));
+ ip_pkt.id = htons(0);
+ ip_pkt.flags_frag_offset = 0;
+ ip_pkt.ttl = 128;
+ ip_pkt.proto = IPPROTO_UDP;
+ ip_pkt.checksum = 0;
+ ip_pkt.src_ip = other->s_addr;
+ ip_pkt.dst_ip = dummy.s_addr;
+ ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (ip_pkt)));
+ memcpy(&packet[off], &ip_pkt, sizeof(ip_pkt));
+ off += sizeof(ip_pkt);
+
+ /* build UDP header */
+ udp_pkt.src_port = htons(NAT_TRAV_PORT); /* FIXME: does this port matter? */
+ udp_pkt.dst_port = htons(NAT_TRAV_PORT);
+
+ memset(&udp_pkt.length, 0, sizeof(uint32_t));
+ udp_pkt.length = htonl(port);
+ memcpy(&packet[off], &udp_pkt, sizeof(udp_pkt));
+ off += sizeof(udp_pkt);
+
+ /* set ICMP checksum */
+ icmp_pkt.checksum = htons(calc_checksum((uint16_t*)&packet[sizeof(ip_pkt)],
+ sizeof (icmp_pkt) + sizeof(ip_pkt) + sizeof(udp_pkt)));
+ memcpy (&packet[sizeof(ip_pkt)], &icmp_pkt, sizeof (icmp_pkt));
+
+
+ memset (&dst, 0, sizeof (dst));
+ dst.sin_family = AF_INET;
+ dst.sin_addr = *other;
+ err = sendto(rawsock,
+ packet,
+ off, 0,
+ (struct sockaddr*)&dst,
+ sizeof(dst));
+
+ if (err < 0)
+ {
+ fprintf(stderr,
+ "sendto failed: %s\n", strerror(errno));
+ }
+ else if (err != off)
+ {
+ fprintf(stderr,
+ "Error: partial send of ICMP message\n");
+ }
}
{
struct ip_packet ip_pkt;
struct icmp_packet *icmp_pkt;
- struct icmp_packet icmp_echo;
+ struct icmp_echo_packet icmp_echo;
struct sockaddr_in dst;
- char packet[sizeof (struct ip_packet)*2 + sizeof (struct icmp_packet)*2];
+ char packet[sizeof (struct ip_packet)*2 + sizeof (struct icmp_packet) + sizeof(struct icmp_echo_packet)];
+
size_t off;
int err;
icmp_pkt->code = 0;
icmp_pkt->reserved = 0;
icmp_pkt->checksum = 0;
+
off += sizeof (struct icmp_packet);
/* ip header of the presumably 'lost' udp packet */
ip_pkt.vers_ihl = 0x45;
ip_pkt.tos = 0;
- ip_pkt.pkt_len = (sizeof (struct ip_packet) + sizeof (struct icmp_packet));
+ ip_pkt.pkt_len = (sizeof (struct ip_packet) + sizeof (struct icmp_echo_packet));
+
ip_pkt.id = 1;
ip_pkt.flags_frag_offset = 0;
ip_pkt.ttl = 1; /* real TTL would be 1 on a time exceeded packet */
ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (struct ip_packet)));
memcpy (&packet[off], &ip_pkt, sizeof (struct ip_packet));
off += sizeof (struct ip_packet);
- make_echo (other, &icmp_echo);
- memcpy (&packet[off], &icmp_echo, sizeof(struct icmp_packet));
- off += sizeof (struct icmp_packet);
- icmp_pkt->checksum = htons(calc_checksum((uint16_t*)icmp_pkt,
- sizeof (struct icmp_packet)*2 + sizeof(struct ip_packet)));
+
+ make_echo (other, &icmp_echo, port);
+ memcpy (&packet[off], &icmp_echo, sizeof(struct icmp_echo_packet));
+ off += sizeof (struct icmp_echo_packet);
+
+ icmp_pkt->checksum = htons(calc_checksum((uint16_t*)icmp_pkt,
+ sizeof (struct icmp_packet) + sizeof(struct ip_packet) + sizeof(struct icmp_echo_packet)));
memset (&dst, 0, sizeof (dst));
dst.sin_family = AF_INET;
main (int argc, char *const *argv)
{
struct in_addr external;
+ struct in_addr target;
uid_t uid;
if (-1 == (rawsock = make_raw_socket()))
fprintf (stderr,
"Failed to setresuid: %s\n",
strerror (errno));
- if (argc != 3)
+
+ if (argc != 4)
{
fprintf (stderr,
- "This program must be started with our IP and the targets external IP as arguments.\n");
+ "This program must be started with our IP, the targets external IP, and our port as arguments.\n");
return 1;
}
+ port = atoi(argv[3]);
+
if ( (1 != inet_pton (AF_INET, argv[1], &external)) ||
(1 != inet_pton (AF_INET, argv[2], &target)) )
{
strerror (errno));
return 1;
}
- inet_pton (AF_INET, DUMMY_IP, &dummy);
+ if (1 != inet_pton (AF_INET, DUMMY_IP, &dummy)) abort ();
send_icmp (&external,
&target);
+ send_icmp_udp (&external,
+ &target);
close (rawsock);
return 0;
}
projects / oweals / gnunet.git / blobdiff