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fix DHCP decode of data after the END option #402

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Merged
GIC-de merged 1 commit into from
Oct 3, 2026
Merged

fix DHCP decode of data after the END option #402

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6 changes: 3 additions & 3 deletions code/bngblaster/src/bbl_protocols.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3077,15 +3077,15 @@ decode_dhcp(uint8_t *buf, uint16_t len,
if(option == DHCP_OPTION_PAD) {
continue;
}
if(option == DHCP_OPTION_END) {
break;
}
option_len = *buf;
BUMP_BUFFER(buf, len, sizeof(uint8_t));
if(option_len > len) {
return DECODE_ERROR;
}
switch(option) {
case DHCP_OPTION_END:
option_len = len;
break;
case DHCP_OPTION_DHCP_MESSAGE_TYPE:
if(option_len != 1) {
return DECODE_ERROR;
Expand Down
50 changes: 50 additions & 0 deletions code/bngblaster/test/protocols.c
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Original file line number Diff line number Diff line change
Expand Up @@ -346,6 +346,55 @@ test_protocols_lcp_chap(void **unused) {
free(sp);
}

/* DHCP Offer with non-zero bytes after the END option. RFC 2132 3.2: END marks
* the end of valid information, so the trailing bytes must be ignored. */
static void
test_protocols_dhcp_end_option(void **unused) {
(void) unused;

uint8_t *sp = calloc(1, SCRATCHPAD_LEN);
uint8_t buf[512] = {0};
uint8_t options[] = {
0x63, 0x82, 0x53, 0x63, /* magic cookie */
0x35, 0x01, 0x02, /* message type offer */
0x36, 0x04, 0x0a, 0x00, 0x00, 0x01, /* server identifier */
0x33, 0x04, 0x00, 0x00, 0x0e, 0x10, /* lease time 3600 */
0xff, /* end */
0x10, 0x00, 0x00, 0x1c, 0xa8, 0x0b, 0x01, 0x01 /* trailing data */
};
uint16_t udp_len = UDP_HDR_LEN + sizeof(struct dhcp_header) + sizeof(options);
uint16_t ip_len = 20 + udp_len;
uint32_t server;

bbl_ethernet_header_s *eth;
bbl_ipv4_s *ipv4;
bbl_udp_s *udp;
bbl_dhcp_s *dhcp;

buf[12] = 0x08; /* ethertype IPv4 */
buf[14] = 0x45;
buf[16] = ip_len >> 8;
buf[17] = ip_len & 0xff;
buf[22] = 64;
buf[23] = PROTOCOL_IPV4_UDP;
buf[35] = DHCP_UDP_SERVER;
buf[37] = DHCP_UDP_CLIENT;
buf[38] = udp_len >> 8;
buf[39] = udp_len & 0xff;
buf[42] = 2; /* BOOTREPLY */
memcpy(buf + 42 + sizeof(struct dhcp_header), options, sizeof(options));
inet_pton(AF_INET, "10.0.0.1", &server);

assert_int_equal(decode_ethernet(buf, 14 + ip_len, sp, SCRATCHPAD_LEN, &eth), PROTOCOL_SUCCESS);
ipv4 = (bbl_ipv4_s*)eth->next;
udp = (bbl_udp_s*)ipv4->next;
dhcp = (bbl_dhcp_s*)udp->next;
assert_int_equal(dhcp->type, DHCP_MESSAGE_OFFER);
assert_int_equal(dhcp->server_identifier, server);
assert_int_equal(dhcp->lease_time, 3600);
free(sp);
}

int main() {
const struct CMUnitTest tests[] = {
cmocka_unit_test(test_protocols_decode_pppoe_ipcp_conf_request),
Expand All @@ -354,6 +403,7 @@ int main() {
cmocka_unit_test(test_protocols_arp_over_mpls_all),
cmocka_unit_test(test_protocols_bbl_flow_id),
cmocka_unit_test(test_protocols_lcp_chap),
cmocka_unit_test(test_protocols_dhcp_end_option),
};
return cmocka_run_group_tests(tests, NULL, NULL);
}