307 lines
8.3 KiB
C
307 lines
8.3 KiB
C
/* $OpenBSD: packet.c,v 1.4 2021/06/16 16:55:02 dv Exp $ */
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/* Packet assembly code, originally contributed by Archie Cobbs. */
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/*
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* Copyright (c) 1995, 1996, 1999 The Internet Software Consortium.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of The Internet Software Consortium nor the names
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* of its contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
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* CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* This software has been written for the Internet Software Consortium
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* by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
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* Enterprises. To learn more about the Internet Software Consortium,
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* see ``http://www.vix.com/isc''. To learn more about Vixie
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* Enterprises, see ``http://www.vix.com''.
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*/
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <arpa/inet.h>
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#include <net/if.h>
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#include <net/if_enc.h>
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#include <netinet/in.h>
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#include <netinet/ip.h>
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#include <netinet/udp.h>
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#include <netinet/if_ether.h>
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#include <string.h>
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#include "dhcp.h"
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#include "vmd.h"
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u_int32_t checksum(unsigned char *, u_int32_t, u_int32_t);
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u_int32_t wrapsum(u_int32_t);
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u_int32_t
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checksum(unsigned char *buf, u_int32_t nbytes, u_int32_t sum)
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{
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u_int32_t i;
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/* Checksum all the pairs of bytes first... */
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for (i = 0; i < (nbytes & ~1U); i += 2) {
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sum += (u_int16_t)ntohs(*((u_int16_t *)(buf + i)));
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if (sum > 0xFFFF)
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sum -= 0xFFFF;
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}
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/*
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* If there's a single byte left over, checksum it, too.
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* Network byte order is big-endian, so the remaining byte is
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* the high byte.
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*/
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if (i < nbytes) {
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sum += buf[i] << 8;
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if (sum > 0xFFFF)
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sum -= 0xFFFF;
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}
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return (sum);
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}
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u_int32_t
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wrapsum(u_int32_t sum)
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{
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sum = ~sum & 0xFFFF;
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return (htons(sum));
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}
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ssize_t
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assemble_hw_header(unsigned char *buf, size_t buflen,
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size_t offset, struct packet_ctx *pc, unsigned int intfhtype)
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{
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struct ether_header eh;
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switch (intfhtype) {
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case HTYPE_ETHER:
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if (buflen < offset + ETHER_HDR_LEN)
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return (-1);
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/* Use the supplied address or let the kernel fill it. */
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memcpy(eh.ether_shost, pc->pc_smac, ETHER_ADDR_LEN);
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memcpy(eh.ether_dhost, pc->pc_dmac, ETHER_ADDR_LEN);
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eh.ether_type = htons(ETHERTYPE_IP);
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memcpy(&buf[offset], &eh, ETHER_HDR_LEN);
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offset += ETHER_HDR_LEN;
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break;
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default:
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return (-1);
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}
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return (offset);
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}
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ssize_t
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assemble_udp_ip_header(unsigned char *buf, size_t buflen, size_t offset,
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struct packet_ctx *pc, unsigned char *data, size_t datalen)
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{
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struct ip ip;
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struct udphdr udp;
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if (buflen < offset + sizeof(ip) + sizeof(udp))
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return (-1);
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ip.ip_v = 4;
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ip.ip_hl = 5;
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ip.ip_tos = IPTOS_LOWDELAY;
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ip.ip_len = htons(sizeof(ip) + sizeof(udp) + datalen);
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ip.ip_id = 0;
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ip.ip_off = 0;
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ip.ip_ttl = 16;
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ip.ip_p = IPPROTO_UDP;
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ip.ip_sum = 0;
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ip.ip_src.s_addr = ss2sin(&pc->pc_src)->sin_addr.s_addr;
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ip.ip_dst.s_addr = ss2sin(&pc->pc_dst)->sin_addr.s_addr;
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ip.ip_sum = wrapsum(checksum((unsigned char *)&ip, sizeof(ip), 0));
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memcpy(&buf[offset], &ip, sizeof(ip));
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offset += sizeof(ip);
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udp.uh_sport = ss2sin(&pc->pc_src)->sin_port;
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udp.uh_dport = ss2sin(&pc->pc_dst)->sin_port;
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udp.uh_ulen = htons(sizeof(udp) + datalen);
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memset(&udp.uh_sum, 0, sizeof(udp.uh_sum));
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udp.uh_sum = wrapsum(checksum((unsigned char *)&udp, sizeof(udp),
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checksum(data, datalen, checksum((unsigned char *)&ip.ip_src,
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2 * sizeof(ip.ip_src),
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IPPROTO_UDP + (u_int32_t)ntohs(udp.uh_ulen)))));
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memcpy(&buf[offset], &udp, sizeof(udp));
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offset += sizeof(udp);
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return (offset);
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}
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ssize_t
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decode_hw_header(unsigned char *buf, size_t buflen,
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size_t offset, struct packet_ctx *pc, unsigned int intfhtype)
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{
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u_int32_t ip_len;
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u_int16_t ether_type;
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struct ether_header *eh;
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struct ip *ip;
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switch (intfhtype) {
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case HTYPE_IPSEC_TUNNEL:
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if (buflen < offset + ENC_HDRLEN + sizeof(*ip))
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return (-1);
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offset += ENC_HDRLEN;
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ip_len = (buf[offset] & 0xf) << 2;
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if (buflen < offset + ip_len)
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return (-1);
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ip = (struct ip *)(buf + offset);
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/* Encapsulated IP */
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if (ip->ip_p != IPPROTO_IPIP)
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return (-1);
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memset(pc->pc_dmac, 0xff, ETHER_ADDR_LEN);
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offset += ip_len;
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pc->pc_htype = ARPHRD_ETHER;
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pc->pc_hlen = ETHER_ADDR_LEN;
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break;
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case HTYPE_ETHER:
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if (buflen < offset + ETHER_HDR_LEN)
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return (-1);
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eh = (struct ether_header *)(buf + offset);
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memcpy(pc->pc_dmac, eh->ether_dhost, ETHER_ADDR_LEN);
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memcpy(pc->pc_smac, eh->ether_shost, ETHER_ADDR_LEN);
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memcpy(ðer_type, &eh->ether_type, sizeof(ether_type));
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if (ether_type != htons(ETHERTYPE_IP))
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return (-1);
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offset += ETHER_HDR_LEN;
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pc->pc_htype = ARPHRD_ETHER;
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pc->pc_hlen = ETHER_ADDR_LEN;
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break;
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default:
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return (-1);
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}
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return (offset);
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}
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ssize_t
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decode_udp_ip_header(unsigned char *buf, size_t buflen,
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size_t offset, struct packet_ctx *pc)
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{
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struct ip *ip;
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struct udphdr *udp;
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unsigned char *data;
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u_int32_t ip_len;
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u_int32_t sum, usum;
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int len;
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/* Assure that an entire IP header is within the buffer. */
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if (buflen < offset + sizeof(*ip))
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return (-1);
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ip = (struct ip *)(buf + offset);
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if (ip->ip_v != IPVERSION)
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return (-1);
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ip_len = ip->ip_hl << 2;
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if (ip_len < sizeof(struct ip) ||
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buflen < offset + ip_len)
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return (-1);
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if (ip->ip_p != IPPROTO_UDP)
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return (-1);
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/* Check the IP header checksum - it should be zero. */
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if (wrapsum(checksum(buf + offset, ip_len, 0)) != 0)
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return (-1);
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pc->pc_src.ss_len = sizeof(struct sockaddr_in);
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pc->pc_src.ss_family = AF_INET;
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memcpy(&ss2sin(&pc->pc_src)->sin_addr, &ip->ip_src,
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sizeof(ss2sin(&pc->pc_src)->sin_addr));
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pc->pc_dst.ss_len = sizeof(struct sockaddr_in);
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pc->pc_dst.ss_family = AF_INET;
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memcpy(&ss2sin(&pc->pc_dst)->sin_addr, &ip->ip_dst,
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sizeof(ss2sin(&pc->pc_dst)->sin_addr));
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#ifdef DEBUG
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if (buflen != offset + ntohs(ip->ip_len))
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log_debug("ip length %d disagrees with bytes received %zd.",
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ntohs(ip->ip_len), buflen - offset);
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#endif
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/* Assure that the entire IP packet is within the buffer. */
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if (buflen < offset + ntohs(ip->ip_len))
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return (-1);
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/* Assure that the UDP header is within the buffer. */
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if (buflen < offset + ip_len + sizeof(*udp))
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return (-1);
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udp = (struct udphdr *)(buf + offset + ip_len);
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/* Assure that the entire UDP packet is within the buffer. */
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if (buflen < offset + ip_len + ntohs(udp->uh_ulen))
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return (-1);
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data = buf + offset + ip_len + sizeof(*udp);
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/*
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* Compute UDP checksums, including the ``pseudo-header'', the
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* UDP header and the data. If the UDP checksum field is zero,
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* we're not supposed to do a checksum.
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*/
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len = ntohs(udp->uh_ulen) - sizeof(*udp);
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if ((len < 0) || (len + data > buf + buflen)) {
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return (-1);
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}
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if (len + data != buf + buflen)
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log_debug("accepting packet with data after udp payload.");
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usum = udp->uh_sum;
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udp->uh_sum = 0;
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sum = wrapsum(checksum((unsigned char *)udp, sizeof(*udp),
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checksum(data, len, checksum((unsigned char *)&ip->ip_src,
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2 * sizeof(ip->ip_src),
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IPPROTO_UDP + (u_int32_t)ntohs(udp->uh_ulen)))));
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if (usum && usum != sum)
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return (-1);
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ss2sin(&pc->pc_src)->sin_port = udp->uh_sport;
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ss2sin(&pc->pc_dst)->sin_port = udp->uh_dport;
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return (offset + ip_len + sizeof(*udp));
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}
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