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sys/net/nanocoap: fix invalid RST messages

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An RST message has no token, so don't reply with a token when sending
RST.

This also adds unit tests to ensure this this exact bug does not sneak
back in.
This commit is contained in:
Marian Buschsieweke 2024-12-11 20:20:11 +01:00
parent fa011a8a1a
commit c7af4b25a6
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GPG Key ID: 758BD52517F79C41
2 changed files with 54 additions and 11 deletions
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22
sys/net/application_layer/nanocoap/nanocoap.c
View File

@ -656,23 +656,23 @@ ssize_t coap_build_reply(coap_pkt_t *pkt, unsigned code,
uint8_t *rbuf, unsigned rlen, unsigned payload_len) uint8_t *rbuf, unsigned rlen, unsigned payload_len)
{ {
unsigned tkl = coap_get_token_len(pkt); unsigned tkl = coap_get_token_len(pkt);
unsigned type = COAP_TYPE_NON;
if (!code) {
/* if code is COAP_CODE_EMPTY (zero), assume Reset (RST) type.
* RST message have no token */
type = COAP_TYPE_RST;
tkl = 0;
}
else if (coap_get_type(pkt) == COAP_TYPE_CON) {
type = COAP_TYPE_ACK;
}
unsigned len = sizeof(coap_hdr_t) + tkl; unsigned len = sizeof(coap_hdr_t) + tkl;
if ((len + payload_len) > rlen) { if ((len + payload_len) > rlen) {
return -ENOSPC; return -ENOSPC;
} }
/* if code is COAP_CODE_EMPTY (zero), assume Reset (RST) type */
unsigned type = COAP_TYPE_RST;
if (code) {
if (coap_get_type(pkt) == COAP_TYPE_CON) {
type = COAP_TYPE_ACK;
}
else {
type = COAP_TYPE_NON;
}
}
uint32_t no_response; uint32_t no_response;
if (coap_opt_get_uint(pkt, COAP_OPT_NO_RESPONSE, &no_response) == 0) { if (coap_opt_get_uint(pkt, COAP_OPT_NO_RESPONSE, &no_response) == 0) {

43
tests/unittests/tests-nanocoap/tests-nanocoap.c
View File

@ -1185,6 +1185,48 @@ static void test_nanocoap__token_length_ext_269(void)
TEST_ASSERT_EQUAL_INT(14, hdr->ver_t_tkl & 0xf); TEST_ASSERT_EQUAL_INT(14, hdr->ver_t_tkl & 0xf);
} }
/*
* Test that a RST message can be generated and parsed
*/
static void test_nanocoap___rst_message(void)
{
static const uint8_t rst_expected[4] = {
0x70, /* Version = 0b01, Type = 0b11 (RST), Token Length = 0b0000 */
0x00, /* Code = 0x00 */
0x13, 0x37 /* Message ID = 0x1337 */
};
uint8_t buf[16];
/* trivial case: build a reset message */
memset(buf, 0x55, sizeof(buf));
TEST_ASSERT_EQUAL_INT(sizeof(rst_expected),
coap_build_hdr((void *)buf, COAP_TYPE_RST, NULL, 0,
0, 0x1337));
TEST_ASSERT(0 == memcmp(rst_expected, buf, sizeof(rst_expected)));
/* did it write past the expected bytes? */
TEST_ASSERT_EQUAL_INT(0x55, buf[sizeof(rst_expected)]);
/* now check that parsing it back works */
coap_pkt_t pkt;
TEST_ASSERT_EQUAL_INT(0, coap_parse(&pkt, buf, sizeof(rst_expected)));
TEST_ASSERT_EQUAL_INT(COAP_TYPE_RST, coap_get_type(&pkt));
TEST_ASSERT_EQUAL_INT(0, coap_get_code_raw(&pkt));
TEST_ASSERT_EQUAL_INT(0, coap_get_token_len(&pkt));
/* now check that generating a RST reply works */
static uint8_t con_request[8] = {
0x44, /* Version = 0b01, Type = 0b00 (CON), Token Length = 0b0100 */
0x01, /* Code = 0.01 (GET) */
0x13, 0x37, /* Message ID = 0x1337 */
0xde, 0xed, 0xbe, 0xef, /* Token = 0xdeadbeef */
};
memset(buf, 0x55, sizeof(buf));
TEST_ASSERT_EQUAL_INT(0, coap_parse(&pkt, con_request, sizeof(con_request)));
TEST_ASSERT_EQUAL_INT(sizeof(rst_expected), coap_build_reply(&pkt, 0, buf, sizeof(buf), 0));
TEST_ASSERT(0 == memcmp(rst_expected, buf, sizeof(rst_expected)));
TEST_ASSERT_EQUAL_INT(0x55, buf[sizeof(rst_expected)]);
}
Test *tests_nanocoap_tests(void) Test *tests_nanocoap_tests(void)
{ {
EMB_UNIT_TESTFIXTURES(fixtures) { EMB_UNIT_TESTFIXTURES(fixtures) {
@ -1223,6 +1265,7 @@ Test *tests_nanocoap_tests(void)
new_TestFixture(test_nanocoap__token_length_over_limit), new_TestFixture(test_nanocoap__token_length_over_limit),
new_TestFixture(test_nanocoap__token_length_ext_16), new_TestFixture(test_nanocoap__token_length_ext_16),
new_TestFixture(test_nanocoap__token_length_ext_269), new_TestFixture(test_nanocoap__token_length_ext_269),
new_TestFixture(test_nanocoap___rst_message),
}; };
EMB_UNIT_TESTCALLER(nanocoap_tests, NULL, NULL, fixtures); EMB_UNIT_TESTCALLER(nanocoap_tests, NULL, NULL, fixtures);