/* SPDX-License-Identifier: LGPL-2.1+ */ /*** This file is part of systemd. Copyright (C) 2013 Intel Corporation. All rights reserved. Copyright (C) 2014 Tom Gundersen systemd is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. systemd is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with systemd; If not, see . ***/ #include #include #include #include #include "dhcp-internal.h" #include "dhcp-protocol.h" #define DHCP_CLIENT_MIN_OPTIONS_SIZE 312 int dhcp_message_init(DHCPMessage *message, uint8_t op, uint32_t xid, uint8_t type, uint16_t arp_type, size_t optlen, size_t *optoffset) { size_t offset = 0; int r; assert(IN_SET(op, BOOTREQUEST, BOOTREPLY)); assert(IN_SET(arp_type, ARPHRD_ETHER, ARPHRD_INFINIBAND)); message->op = op; message->htype = arp_type; message->hlen = (arp_type == ARPHRD_ETHER) ? ETHER_ADDR_LEN : 0; message->xid = htobe32(xid); message->magic = htobe32(DHCP_MAGIC_COOKIE); r = dhcp_option_append(message, optlen, &offset, 0, SD_DHCP_OPTION_MESSAGE_TYPE, 1, &type); if (r < 0) return r; *optoffset = offset; return 0; } uint16_t dhcp_packet_checksum(uint8_t *buf, size_t len) { uint64_t *buf_64 = (uint64_t*)buf; uint64_t *end_64 = buf_64 + (len / sizeof(uint64_t)); uint64_t sum = 0; /* See RFC1071 */ while (buf_64 < end_64) { sum += *buf_64; if (sum < *buf_64) /* wrap around in one's complement */ sum++; buf_64++; } if (len % sizeof(uint64_t)) { /* If the buffer is not aligned to 64-bit, we need to zero-pad the last few bytes and add them in */ uint64_t buf_tail = 0; memcpy(&buf_tail, buf_64, len % sizeof(uint64_t)); sum += buf_tail; if (sum < buf_tail) /* wrap around */ sum++; } while (sum >> 16) sum = (sum & 0xffff) + (sum >> 16); return ~sum; } void dhcp_packet_append_ip_headers(DHCPPacket *packet, be32_t source_addr, uint16_t source_port, be32_t destination_addr, uint16_t destination_port, uint16_t len) { packet->ip.version = IPVERSION; packet->ip.ihl = DHCP_IP_SIZE / 4; packet->ip.tot_len = htobe16(len); packet->ip.tos = IPTOS_CLASS_CS6; packet->ip.protocol = IPPROTO_UDP; packet->ip.saddr = source_addr; packet->ip.daddr = destination_addr; packet->udp.source = htobe16(source_port); packet->udp.dest = htobe16(destination_port); packet->udp.len = htobe16(len - DHCP_IP_SIZE); packet->ip.check = packet->udp.len; packet->udp.check = dhcp_packet_checksum((uint8_t*)&packet->ip.ttl, len - 8); packet->ip.ttl = IPDEFTTL; packet->ip.check = 0; packet->ip.check = dhcp_packet_checksum((uint8_t*)&packet->ip, DHCP_IP_SIZE); } int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum, uint16_t port) { size_t hdrlen; assert(packet); /* IP */ if (packet->ip.version != IPVERSION) { log_debug("ignoring packet: not IPv4"); return -EINVAL; } if (packet->ip.ihl < 5) { log_debug("ignoring packet: IPv4 IHL (%u words) invalid", packet->ip.ihl); return -EINVAL; } hdrlen = packet->ip.ihl * 4; if (hdrlen < 20) { log_debug("ignoring packet: IPv4 IHL (%zu bytes) " "smaller than minimum (20 bytes)", hdrlen); return -EINVAL; } if (len < hdrlen) { log_debug("ignoring packet: packet (%zu bytes) " "smaller than expected (%zu) by IP header", len, hdrlen); return -EINVAL; } /* UDP */ if (packet->ip.protocol != IPPROTO_UDP) { log_debug("ignoring packet: not UDP"); return -EINVAL; } if (len < hdrlen + be16toh(packet->udp.len)) { log_debug("ignoring packet: packet (%zu bytes) " "smaller than expected (%zu) by UDP header", len, hdrlen + be16toh(packet->udp.len)); return -EINVAL; } if (be16toh(packet->udp.dest) != port) { log_debug("ignoring packet: to port %u, which " "is not the DHCP client port (%u)", be16toh(packet->udp.dest), port); return -EINVAL; } /* checksums - computing these is relatively expensive, so only do it if all the other checks have passed */ if (dhcp_packet_checksum((uint8_t*)&packet->ip, hdrlen)) { log_debug("ignoring packet: invalid IP checksum"); return -EINVAL; } if (checksum && packet->udp.check) { packet->ip.check = packet->udp.len; packet->ip.ttl = 0; if (dhcp_packet_checksum((uint8_t*)&packet->ip.ttl, be16toh(packet->udp.len) + 12)) { log_debug("ignoring packet: invalid UDP checksum"); return -EINVAL; } } return 0; }