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-rw-r--r--src/libsystemd-network/dhcp-packet.c193
1 files changed, 193 insertions, 0 deletions
diff --git a/src/libsystemd-network/dhcp-packet.c b/src/libsystemd-network/dhcp-packet.c
new file mode 100644
index 0000000..75b1d7e
--- /dev/null
+++ b/src/libsystemd-network/dhcp-packet.c
@@ -0,0 +1,193 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+ Copyright © 2013 Intel Corporation. All rights reserved.
+***/
+
+#include <errno.h>
+#include <net/ethernet.h>
+#include <net/if_arp.h>
+#include <string.h>
+
+#include "dhcp-option.h"
+#include "dhcp-packet.h"
+#include "memory-util.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,
+ uint8_t hlen,
+ const uint8_t *chaddr,
+ size_t optlen,
+ size_t *optoffset) {
+
+ size_t offset = 0;
+ int r;
+
+ assert(IN_SET(op, BOOTREQUEST, BOOTREPLY));
+ assert(chaddr || hlen == 0);
+
+ message->op = op;
+ message->htype = arp_type;
+
+ /* RFC2131 section 4.1.1:
+ The client MUST include its hardware address in the ’chaddr’ field, if
+ necessary for delivery of DHCP reply messages.
+
+ RFC 4390 section 2.1:
+ A DHCP client, when working over an IPoIB interface, MUST follow the
+ following rules:
+ "htype" (hardware address type) MUST be 32 [ARPPARAM].
+ "hlen" (hardware address length) MUST be 0.
+ "chaddr" (client hardware address) field MUST be zeroed.
+ */
+ message->hlen = arp_type == ARPHRD_INFINIBAND ? 0 : hlen;
+ memcpy_safe(message->chaddr, chaddr, message->hlen);
+
+ 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, int ip_service_type) {
+ packet->ip.version = IPVERSION;
+ packet->ip.ihl = DHCP_IP_SIZE / 4;
+ packet->ip.tot_len = htobe16(len);
+
+ if (ip_service_type >= 0)
+ packet->ip.tos = ip_service_type;
+ else
+ 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);
+
+ if (len < sizeof(DHCPPacket))
+ return 0;
+
+ /* IP */
+
+ if (packet->ip.version != IPVERSION)
+ return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+ "ignoring packet: not IPv4");
+
+ if (packet->ip.ihl < 5)
+ return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+ "ignoring packet: IPv4 IHL (%i words) invalid",
+ packet->ip.ihl);
+
+ hdrlen = packet->ip.ihl * 4;
+ if (hdrlen < 20)
+ return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+ "ignoring packet: IPv4 IHL (%zu bytes) smaller than minimum (20 bytes)",
+ hdrlen);
+
+ if (len < hdrlen)
+ return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+ "ignoring packet: packet (%zu bytes) smaller than expected (%zu) by IP header",
+ len, hdrlen);
+
+ /* UDP */
+
+ if (packet->ip.protocol != IPPROTO_UDP)
+ return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+ "ignoring packet: not UDP");
+
+ if (len < hdrlen + be16toh(packet->udp.len))
+ return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+ "ignoring packet: packet (%zu bytes) smaller than expected (%zu) by UDP header",
+ len, hdrlen + be16toh(packet->udp.len));
+
+ if (be16toh(packet->udp.dest) != port)
+ return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+ "ignoring packet: to port %u, which is not the DHCP client port (%u)",
+ be16toh(packet->udp.dest), port);
+
+ /* 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))
+ return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+ "ignoring packet: invalid IP checksum");
+
+ 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))
+ return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+ "ignoring packet: invalid UDP checksum");
+ }
+
+ return 0;
+}