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-rw-r--r--src/libsystemd-dhcp/dhcp-internal.h4
-rw-r--r--src/libsystemd-dhcp/dhcp-packet.c86
-rw-r--r--src/libsystemd-dhcp/sd-dhcp-client.c28
3 files changed, 68 insertions, 50 deletions
diff --git a/src/libsystemd-dhcp/dhcp-internal.h b/src/libsystemd-dhcp/dhcp-internal.h
index efb8ea5411..9a997c10c4 100644
--- a/src/libsystemd-dhcp/dhcp-internal.h
+++ b/src/libsystemd-dhcp/dhcp-internal.h
@@ -48,8 +48,8 @@ int dhcp_option_parse(DHCPMessage *message, size_t len,
int dhcp_message_init(DHCPMessage *message, uint8_t op, uint32_t xid, uint8_t type,
uint16_t secs, uint8_t **opt, size_t *optlen);
-void dhcp_packet_append_ip_headers(DHCPPacket *packet, uint8_t op, uint16_t len);
+void dhcp_packet_append_ip_headers(DHCPPacket *packet, uint16_t len);
-int dhcp_packet_verify_headers(DHCPPacket *packet, uint8_t op, size_t len);
+int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len);
#define log_dhcp_client(client, fmt, ...) log_meta(LOG_DEBUG, __FILE__, __LINE__, __func__, "DHCP CLIENT: " fmt, ##__VA_ARGS__)
diff --git a/src/libsystemd-dhcp/dhcp-packet.c b/src/libsystemd-dhcp/dhcp-packet.c
index 4501d27571..7c209fa658 100644
--- a/src/libsystemd-dhcp/dhcp-packet.c
+++ b/src/libsystemd-dhcp/dhcp-packet.c
@@ -94,10 +94,7 @@ static uint16_t dhcp_checksum(void *buf, int len) {
return ~sum;
}
-void dhcp_packet_append_ip_headers(DHCPPacket *packet, uint8_t op,
- uint16_t len) {
- assert(op == BOOTREQUEST || op == BOOTREPLY);
-
+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);
@@ -106,16 +103,8 @@ void dhcp_packet_append_ip_headers(DHCPPacket *packet, uint8_t op,
packet->ip.saddr = INADDR_ANY;
packet->ip.daddr = INADDR_BROADCAST;
- switch (op) {
- case BOOTREQUEST:
- packet->udp.source = htobe16(DHCP_PORT_CLIENT);
- packet->udp.dest = htobe16(DHCP_PORT_SERVER);
- break;
- case BOOTREPLY:
- packet->udp.source = htobe16(DHCP_PORT_SERVER);
- packet->udp.dest = htobe16(DHCP_PORT_CLIENT);
- break;
- }
+ packet->udp.source = htobe16(DHCP_PORT_CLIENT);
+ packet->udp.dest = htobe16(DHCP_PORT_SERVER);
packet->udp.len = htobe16(len - DHCP_IP_SIZE);
@@ -127,30 +116,56 @@ void dhcp_packet_append_ip_headers(DHCPPacket *packet, uint8_t op,
packet->ip.check = dhcp_checksum(&packet->ip, DHCP_IP_SIZE);
}
-int dhcp_packet_verify_headers(DHCPPacket *packet, uint8_t op, size_t len) {
+int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len) {
size_t hdrlen;
- assert(op == BOOTREQUEST || op == BOOTREPLY);
+ /* IP */
- if (len < (DHCP_IP_UDP_SIZE + DHCP_MESSAGE_SIZE)) {
- log_dhcp_client(client, "ignoring packet: packet too small");
+ 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 || hdrlen > len) {
- log_dhcp_client(client, "ignoring packet: header with wrong size");
+ 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");
+ 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 (hdrlen + be16toh(packet->udp.len) > len) {
- log_dhcp_client(client, "ignoring packet: packet too small (udp.len=%u)",
- 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;
}
@@ -160,32 +175,17 @@ int dhcp_packet_verify_headers(DHCPPacket *packet, uint8_t op, size_t len) {
if (dhcp_checksum(&packet->ip.ttl,
be16toh(packet->udp.len) + 12)) {
- log_dhcp_client(client, "ignoring packet: invalid udp checksum");
+ log_dhcp_client(client, "ignoring packet: invalid UDP checksum");
return -EINVAL;
}
}
- if (packet->dhcp.op != op) {
- log_dhcp_client(client, "ignoring packet: wrong operation");
+ if (be16toh(packet->udp.source) != DHCP_PORT_SERVER ||
+ be16toh(packet->udp.dest) != DHCP_PORT_CLIENT) {
+ log_dhcp_client(client, "ignoring packet: wrong ports (source: %u, destination: %u)",
+ be16toh(packet->udp.source), be16toh(packet->udp.dest));
return -EINVAL;
}
- switch (op) {
- case BOOTREQUEST:
- if (be16toh(packet->udp.source) != DHCP_PORT_CLIENT ||
- be16toh(packet->udp.dest) != DHCP_PORT_SERVER) {
- log_dhcp_client(client, "ignoring packet: wrong ports");
- return -EINVAL;
- }
- break;
- case BOOTREPLY:
- if (be16toh(packet->udp.source) != DHCP_PORT_SERVER ||
- be16toh(packet->udp.dest) != DHCP_PORT_CLIENT) {
- log_dhcp_client(client, "ignoring packet: wrong ports");
- return -EINVAL;
- }
- break;
- }
-
return 0;
}
diff --git a/src/libsystemd-dhcp/sd-dhcp-client.c b/src/libsystemd-dhcp/sd-dhcp-client.c
index 7f86d92fb5..54bc19511d 100644
--- a/src/libsystemd-dhcp/sd-dhcp-client.c
+++ b/src/libsystemd-dhcp/sd-dhcp-client.c
@@ -279,7 +279,7 @@ static int client_send_discover(sd_dhcp_client *client, uint16_t secs) {
if (err < 0)
return err;
- dhcp_packet_append_ip_headers(discover, BOOTREQUEST, len);
+ dhcp_packet_append_ip_headers(discover, len);
err = dhcp_network_send_raw_socket(client->fd, &client->link,
discover, len);
@@ -332,7 +332,7 @@ static int client_send_request(sd_dhcp_client *client, uint16_t secs) {
&request->dhcp,
len - DHCP_IP_UDP_SIZE);
} else {
- dhcp_packet_append_ip_headers(request, BOOTREQUEST, len);
+ dhcp_packet_append_ip_headers(request, len);
err = dhcp_network_send_raw_socket(client->fd, &client->link,
request, len);
@@ -736,12 +736,30 @@ static int client_handle_message(sd_dhcp_client *client, DHCPMessage *message,
assert(client->event);
assert(message);
- if (be32toh(message->xid) != client->xid)
+ if (len < DHCP_MESSAGE_SIZE) {
+ log_dhcp_client(client, "message too small (%d bytes): "
+ "ignoring", len);
return 0;
+ }
+
+ if (message->op != BOOTREPLY) {
+ log_dhcp_client(client, "not a BOOTREPLY message: ignoring");
+ return 0;
+ }
+
+ if (be32toh(message->xid) != client->xid) {
+ log_dhcp_client(client, "received xid (%u) does not match "
+ "expected (%u): ignoring",
+ be32toh(message->xid), client->xid);
+ return 0;
+ }
if (memcmp(&message->chaddr[0], &client->mac_addr.ether_addr_octet,
- ETHER_ADDR_LEN))
+ ETHER_ADDR_LEN)) {
+ log_dhcp_client(client, "received chaddr does not match "
+ "expected: ignoring");
return 0;
+ }
switch (client->state) {
case DHCP_STATE_SELECTING:
@@ -869,7 +887,7 @@ static int client_receive_message_raw(sd_event_source *s, int fd,
packet = (DHCPPacket *) buf;
- r = dhcp_packet_verify_headers(packet, BOOTREPLY, len);
+ r = dhcp_packet_verify_headers(packet, len);
if (r < 0)
return 0;
generated by cgit v1.2.3-54-g00ecf (git 2.45.2) at 2024-11-24 00:07:58 +0000