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nanocoap: Added token length validation.

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Implemented a check in coap_parse() to verify if TKL value is within valid range as specified by RFC7252. The token length must be within 0-8 range, any other value should be considered as invalid and the packet should produce message format error.
A test case was added to tests-nanocoap.c to verify correct behavior in case of TKL in range and out of range.

Update sys/net/application_layer/nanocoap/nanocoap.c

Prefixed debug message with module name and abbreviations expanded.

Co-authored-by: Martine Lenders <mail@martine-lenders.eu>

Update sys/net/application_layer/nanocoap/nanocoap.c

Prefixed debug message with module name and abbreviations expanded.

Co-authored-by: Martine Lenders <mail@martine-lenders.eu>
This commit is contained in:
Maciej Jurczak 2020-05-21 16:30:15 +02:00
parent 3be2c51c42
commit edf016a6cb
3 changed files with 49 additions and 3 deletions
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7
sys/include/net/coap.h
View File

@ -161,6 +161,13 @@ extern "C" {
#define COAP_OBS_DEREGISTER (1)
/** @} */
/**
* @name CoAP message format constants
* @{
*/
#define COAP_TOKEN_LENGTH_MAX (8)
/** @} */
/**
* @defgroup net_coap_conf CoAP compile configurations
* @ingroup net_coap

10
sys/net/application_layer/nanocoap/nanocoap.c
View File

@ -79,13 +79,17 @@ int coap_parse(coap_pkt_t *pkt, uint8_t *buf, size_t len)
}
/* token value (tkl bytes) */
if (coap_get_token_len(pkt)) {
if (coap_get_token_len(pkt) == 0) {
pkt->token = NULL;
}
else if (coap_get_token_len(pkt) <= COAP_TOKEN_LENGTH_MAX) {
pkt->token = pkt_pos;
/* pkt_pos range is validated after options parsing loop below */
pkt_pos += coap_get_token_len(pkt);
}
else {
pkt->token = NULL;
DEBUG("nanocoap: token length invalid\n");
return -EBADMSG;
}
coap_optpos_t *optpos = pkt->options;
@ -134,7 +138,7 @@ int coap_parse(coap_pkt_t *pkt, uint8_t *buf, size_t len)
}
if (pkt_pos > pkt_end) {
DEBUG("bad pkt len\n");
DEBUG("nanocoap: bad packet length\n");
return -EBADMSG;
}

35
tests/unittests/tests-nanocoap/tests-nanocoap.c
View File

@ -802,6 +802,40 @@ static void test_nanocoap__add_get_proxy_uri(void)
TEST_ASSERT_EQUAL_INT(0, strncmp((char *) proxy_uri, (char *) uri, len));
}
/*
* Verifies that coap_parse() recognizes token length bigger than allowed.
*/
static void test_nanocoap__token_length_over_limit(void)
{
/* RFC7252 states that TKL must be within 0-8:
* "Lengths 9-15 are reserved, MUST NOT be sent,
* and MUST be processed as a message format error."
*/
uint16_t msgid = 0xABCD;
uint8_t buf_invalid[] = {
0x49, 0x01, 0xAB, 0xCD,
0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99
};
uint8_t buf_valid[] = {
0x48, 0x01, 0xAB, 0xCD,
0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88
};
coap_pkt_t pkt;
/* Valid packet (TKL = 8) */
int res = coap_parse(&pkt, buf_valid, sizeof(buf_valid));
TEST_ASSERT_EQUAL_INT(0, res);
TEST_ASSERT_EQUAL_INT(1, coap_get_code_raw(&pkt));
TEST_ASSERT_EQUAL_INT(msgid, coap_get_id(&pkt));
TEST_ASSERT_EQUAL_INT(8, coap_get_token_len(&pkt));
TEST_ASSERT_EQUAL_INT(0, pkt.payload_len);
/* Invalid packet (TKL = 9) */
res = coap_parse(&pkt, buf_invalid, sizeof(buf_invalid));
TEST_ASSERT_EQUAL_INT(-EBADMSG, res);
}
Test *tests_nanocoap_tests(void)
{
EMB_UNIT_TESTFIXTURES(fixtures) {
@ -828,6 +862,7 @@ Test *tests_nanocoap_tests(void)
new_TestFixture(test_nanocoap__empty),
new_TestFixture(test_nanocoap__add_path_unterminated_string),
new_TestFixture(test_nanocoap__add_get_proxy_uri),
new_TestFixture(test_nanocoap__token_length_over_limit),
};
EMB_UNIT_TESTCALLER(nanocoap_tests, NULL, NULL, fixtures);