diff options
Diffstat (limited to 'src/libsystemd-network/dhcp-packet.c')
| -rw-r--r-- | src/libsystemd-network/dhcp-packet.c | 191 |
1 files changed, 191 insertions, 0 deletions
diff --git a/src/libsystemd-network/dhcp-packet.c b/src/libsystemd-network/dhcp-packet.c new file mode 100644 index 0000000000..95c4277f8c --- /dev/null +++ b/src/libsystemd-network/dhcp-packet.c @@ -0,0 +1,191 @@ +/*** + 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 <http://www.gnu.org/licenses/>. +***/ + +#include <stdlib.h> +#include <errno.h> +#include <string.h> +#include <stdio.h> +#include <net/ethernet.h> +#include <net/if_arp.h> +#include <sys/param.h> + +#include "util.h" +#include "list.h" + +#include "dhcp-protocol.h" +#include "dhcp-lease-internal.h" +#include "dhcp-internal.h" +#include "sd-dhcp-lease.h" +#include "sd-dhcp-client.h" + +#define DHCP_CLIENT_MIN_OPTIONS_SIZE 312 + +int dhcp_message_init(DHCPMessage *message, uint8_t op, uint32_t xid, + uint8_t type, uint8_t **opt, size_t *optlen) { + int err; + + assert(op == BOOTREQUEST || op == BOOTREPLY); + + *opt = (uint8_t *)(message + 1); + + if (*optlen < 4) + return -ENOBUFS; + *optlen -= 4; + + message->op = op; + message->htype = ARPHRD_ETHER; + message->hlen = ETHER_ADDR_LEN; + message->xid = htobe32(xid); + + (*opt)[0] = 0x63; + (*opt)[1] = 0x82; + (*opt)[2] = 0x53; + (*opt)[3] = 0x63; + + *opt += 4; + + err = dhcp_option_append(opt, optlen, DHCP_OPTION_MESSAGE_TYPE, 1, + &type); + if (err < 0) + return err; + + return 0; +} + +static uint16_t dhcp_checksum(void *buf, int len) { + uint32_t sum; + uint16_t *check; + int i; + uint8_t *odd; + + sum = 0; + check = buf; + + for (i = 0; i < len / 2 ; i++) + sum += check[i]; + + if (len & 0x01) { + odd = buf; + sum += odd[len - 1]; + } + + while (sum >> 16) + sum = (sum & 0xffff) + (sum >> 16); + + return ~sum; +} + +void dhcp_packet_append_ip_headers(DHCPPacket *packet, uint16_t len) { + packet->ip.version = IPVERSION; + packet->ip.ihl = DHCP_IP_SIZE / 4; + packet->ip.tot_len = htobe16(len); + + packet->ip.protocol = IPPROTO_UDP; + packet->ip.saddr = INADDR_ANY; + packet->ip.daddr = INADDR_BROADCAST; + + packet->udp.source = htobe16(DHCP_PORT_CLIENT); + packet->udp.dest = htobe16(DHCP_PORT_SERVER); + + packet->udp.len = htobe16(len - DHCP_IP_SIZE); + + packet->ip.check = packet->udp.len; + packet->udp.check = dhcp_checksum(&packet->ip.ttl, len - 8); + + packet->ip.ttl = IPDEFTTL; + packet->ip.check = 0; + packet->ip.check = dhcp_checksum(&packet->ip, DHCP_IP_SIZE); +} + +int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum) { + size_t hdrlen; + + assert(packet); + + /* IP */ + + if (len < DHCP_IP_SIZE) { + log_dhcp_client(client, "ignoring packet: packet (%zu bytes) " + " smaller than IP header (%u bytes)", len, + DHCP_IP_SIZE); + return -EINVAL; + } + + if (packet->ip.ihl < 5) { + log_dhcp_client(client, "ignoring packet: IPv4 IHL (%u words) invalid", + packet->ip.ihl); + return -EINVAL; + } + + hdrlen = packet->ip.ihl * 4; + if (hdrlen < 20) { + log_dhcp_client(client, "ignoring packet: IPv4 IHL (%zu bytes) " + "smaller than minimum (20 bytes)", hdrlen); + return -EINVAL; + } + + if (len < hdrlen) { + log_dhcp_client(client, "ignoring packet: packet (%zu bytes) " + "smaller than expected (%zu) by IP header", len, + hdrlen); + return -EINVAL; + } + + if (dhcp_checksum(&packet->ip, hdrlen)) { + log_dhcp_client(client, "ignoring packet: invalid IP checksum"); + return -EINVAL; + } + + /* UDP */ + + if (len < DHCP_IP_UDP_SIZE) { + log_dhcp_client(client, "ignoring packet: packet (%zu bytes) " + " smaller than IP+UDP header (%u bytes)", len, + DHCP_IP_UDP_SIZE); + return -EINVAL; + } + + if (len < hdrlen + be16toh(packet->udp.len)) { + log_dhcp_client(client, "ignoring packet: packet (%zu bytes) " + "smaller than expected (%zu) by UDP header", len, + hdrlen + be16toh(packet->udp.len)); + return -EINVAL; + } + + if (checksum && packet->udp.check) { + packet->ip.check = packet->udp.len; + packet->ip.ttl = 0; + + if (dhcp_checksum(&packet->ip.ttl, + be16toh(packet->udp.len) + 12)) { + log_dhcp_client(client, "ignoring packet: invalid UDP checksum"); + return -EINVAL; + } + } + + if (be16toh(packet->udp.dest) != DHCP_PORT_CLIENT) { + log_dhcp_client(client, "ignoring packet: to port %u, which " + "is not the DHCP client port (%u)", + be16toh(packet->udp.dest), DHCP_PORT_CLIENT); + return -EINVAL; + } + + return 0; +} |