mirror of
https://github.com/sheumann/hush.git
synced 2024-08-20 04:28:57 +00:00
202 lines
5.2 KiB
C
202 lines
5.2 KiB
C
#include <unistd.h>
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#include <string.h>
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#include <netinet/in.h>
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <features.h>
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#if __GLIBC__ >=2 && __GLIBC_MINOR >= 1
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#include <netpacket/packet.h>
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#include <net/ethernet.h>
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#else
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#include <asm/types.h>
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#include <linux/if_packet.h>
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#include <linux/if_ether.h>
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#endif
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#include <errno.h>
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#include "dhcpd.h"
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#include "options.h"
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#include "common.h"
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void init_header(struct dhcpMessage *packet, char type)
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{
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memset(packet, 0, sizeof(struct dhcpMessage));
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switch (type) {
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case DHCPDISCOVER:
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case DHCPREQUEST:
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case DHCPRELEASE:
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case DHCPINFORM:
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packet->op = BOOTREQUEST;
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break;
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case DHCPOFFER:
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case DHCPACK:
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case DHCPNAK:
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packet->op = BOOTREPLY;
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}
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packet->htype = ETH_10MB;
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packet->hlen = ETH_10MB_LEN;
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packet->cookie = htonl(DHCP_MAGIC);
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packet->options[0] = DHCP_END;
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add_simple_option(packet->options, DHCP_MESSAGE_TYPE, type);
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}
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/* read a packet from socket fd, return -1 on read error, -2 on packet error */
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int get_packet(struct dhcpMessage *packet, int fd)
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{
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int bytes;
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int i;
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const char broken_vendors[][8] = {
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"MSFT 98",
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""
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};
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char unsigned *vendor;
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memset(packet, 0, sizeof(struct dhcpMessage));
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bytes = read(fd, packet, sizeof(struct dhcpMessage));
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if (bytes < 0) {
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DEBUG(LOG_INFO, "couldn't read on listening socket, ignoring");
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return -1;
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}
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if (ntohl(packet->cookie) != DHCP_MAGIC) {
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LOG(LOG_ERR, "received bogus message, ignoring");
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return -2;
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}
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DEBUG(LOG_INFO, "Received a packet");
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if (packet->op == BOOTREQUEST && (vendor = get_option(packet, DHCP_VENDOR))) {
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for (i = 0; broken_vendors[i][0]; i++) {
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if (vendor[OPT_LEN - 2] == (unsigned char) strlen(broken_vendors[i]) &&
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!strncmp(vendor, broken_vendors[i], vendor[OPT_LEN - 2])) {
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DEBUG(LOG_INFO, "broken client (%s), forcing broadcast",
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broken_vendors[i]);
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packet->flags |= htons(BROADCAST_FLAG);
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}
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}
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}
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return bytes;
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}
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u_int16_t checksum(void *addr, int count)
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{
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/* Compute Internet Checksum for "count" bytes
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* beginning at location "addr".
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*/
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register int32_t sum = 0;
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u_int16_t *source = (u_int16_t *) addr;
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while (count > 1) {
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/* This is the inner loop */
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sum += *source++;
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count -= 2;
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}
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/* Add left-over byte, if any */
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if (count > 0) {
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/* Make sure that the left-over byte is added correctly both
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* with little and big endian hosts */
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u_int16_t tmp = 0;
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*(unsigned char *) (&tmp) = * (unsigned char *) source;
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sum += tmp;
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}
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/* Fold 32-bit sum to 16 bits */
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while (sum >> 16)
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sum = (sum & 0xffff) + (sum >> 16);
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return ~sum;
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}
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/* Constuct a ip/udp header for a packet, and specify the source and dest hardware address */
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int raw_packet(struct dhcpMessage *payload, u_int32_t source_ip, int source_port,
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u_int32_t dest_ip, int dest_port, unsigned char *dest_arp, int ifindex)
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{
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int fd;
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int result;
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struct sockaddr_ll dest;
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struct udp_dhcp_packet packet;
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if ((fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP))) < 0) {
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DEBUG(LOG_ERR, "socket call failed: %m");
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return -1;
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}
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memset(&dest, 0, sizeof(dest));
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memset(&packet, 0, sizeof(packet));
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dest.sll_family = AF_PACKET;
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dest.sll_protocol = htons(ETH_P_IP);
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dest.sll_ifindex = ifindex;
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dest.sll_halen = 6;
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memcpy(dest.sll_addr, dest_arp, 6);
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if (bind(fd, (struct sockaddr *)&dest, sizeof(struct sockaddr_ll)) < 0) {
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DEBUG(LOG_ERR, "bind call failed: %m");
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close(fd);
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return -1;
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}
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packet.ip.protocol = IPPROTO_UDP;
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packet.ip.saddr = source_ip;
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packet.ip.daddr = dest_ip;
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packet.udp.source = htons(source_port);
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packet.udp.dest = htons(dest_port);
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packet.udp.len = htons(sizeof(packet.udp) + sizeof(struct dhcpMessage)); /* cheat on the psuedo-header */
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packet.ip.tot_len = packet.udp.len;
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memcpy(&(packet.data), payload, sizeof(struct dhcpMessage));
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packet.udp.check = checksum(&packet, sizeof(struct udp_dhcp_packet));
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packet.ip.tot_len = htons(sizeof(struct udp_dhcp_packet));
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packet.ip.ihl = sizeof(packet.ip) >> 2;
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packet.ip.version = IPVERSION;
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packet.ip.ttl = IPDEFTTL;
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packet.ip.check = checksum(&(packet.ip), sizeof(packet.ip));
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result = sendto(fd, &packet, sizeof(struct udp_dhcp_packet), 0, (struct sockaddr *) &dest, sizeof(dest));
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if (result <= 0) {
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DEBUG(LOG_ERR, "write on socket failed: %m");
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}
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close(fd);
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return result;
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}
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/* Let the kernel do all the work for packet generation */
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int kernel_packet(struct dhcpMessage *payload, u_int32_t source_ip, int source_port,
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u_int32_t dest_ip, int dest_port)
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{
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int n = 1;
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int fd, result;
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struct sockaddr_in client;
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if ((fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
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return -1;
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if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (char *) &n, sizeof(n)) == -1)
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return -1;
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memset(&client, 0, sizeof(client));
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client.sin_family = AF_INET;
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client.sin_port = htons(source_port);
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client.sin_addr.s_addr = source_ip;
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if (bind(fd, (struct sockaddr *)&client, sizeof(struct sockaddr)) == -1)
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return -1;
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memset(&client, 0, sizeof(client));
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client.sin_family = AF_INET;
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client.sin_port = htons(dest_port);
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client.sin_addr.s_addr = dest_ip;
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if (connect(fd, (struct sockaddr *)&client, sizeof(struct sockaddr)) == -1)
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return -1;
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result = write(fd, payload, sizeof(struct dhcpMessage));
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close(fd);
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return result;
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}
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