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Use fewer magic numbers in TLS-Exporter functions

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Signed-off-by: Max Fillinger <maximilian.fillinger@foxcrypto.com>
This commit is contained in:
Max Fillinger 2024-10-23 16:32:54 +02:00
parent f2dda15ce8
commit 155cea0900
1 changed files with 32 additions and 21 deletions
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53
library/ssl_tls.c
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@ -8942,36 +8942,43 @@ static int mbedtls_ssl_tls12_export_keying_material(const mbedtls_ssl_context *s
const int use_context)
{
int ret = 0;
size_t prf_input_len = use_context ? 64 + 2 + context_len : 64;
unsigned char *prf_input = NULL;
if (use_context && context_len >= (1 << 16)) {
ret = MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
goto exit;
}
prf_input = mbedtls_calloc(prf_input_len, sizeof(unsigned char));
if (prf_input == NULL) {
ret = MBEDTLS_ERR_SSL_ALLOC_FAILED;
goto exit;
}
/* The input to the PRF is client_random, then server_random.
* If a context is provided, this is then followed by the context length
* as a 16-bit big-endian integer, and then the context itself. */
memcpy(prf_input, ssl->transform->randbytes + 32, 32);
memcpy(prf_input + 32, ssl->transform->randbytes, 32);
const size_t randbytes_len = MBEDTLS_CLIENT_HELLO_RANDOM_LEN + MBEDTLS_SERVER_HELLO_RANDOM_LEN;
size_t prf_input_len = randbytes_len;
if (use_context) {
prf_input[64] = (unsigned char) ((context_len >> 8) & 0xff);
prf_input[65] = (unsigned char) (context_len & 0xff);
memcpy(prf_input + 66, context, context_len);
if (context_len > UINT16_MAX) {
return MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
}
ret = tls_prf_generic(hash_alg, ssl->session->master, 48,
/* This does not overflow a 32-bit size_t because the current value of
* prf_input_len is 64 (length of client_random + server_random) and
* context_len fits into two bytes (checked above). */
prf_input_len += sizeof(uint16_t) + context_len;
}
prf_input = mbedtls_calloc(prf_input_len, sizeof(unsigned char));
if (prf_input == NULL) {
return MBEDTLS_ERR_SSL_ALLOC_FAILED;
}
memcpy(prf_input,
ssl->transform->randbytes + MBEDTLS_SERVER_HELLO_RANDOM_LEN,
MBEDTLS_CLIENT_HELLO_RANDOM_LEN);
memcpy(prf_input + MBEDTLS_CLIENT_HELLO_RANDOM_LEN,
ssl->transform->randbytes,
MBEDTLS_SERVER_HELLO_RANDOM_LEN);
if (use_context) {
MBEDTLS_PUT_UINT16_BE(context_len, prf_input, randbytes_len);
memcpy(prf_input + randbytes_len + sizeof(uint16_t), context, context_len);
}
ret = tls_prf_generic(hash_alg, ssl->session->master, sizeof(ssl->session->master),
label, label_len,
prf_input, prf_input_len,
out, key_len);
exit:
mbedtls_free(prf_input);
return ret;
}
@ -8991,7 +8998,11 @@ static int mbedtls_ssl_tls13_export_keying_material(mbedtls_ssl_context *ssl,
const size_t hash_len = PSA_HASH_LENGTH(hash_alg);
const unsigned char *secret = ssl->session->app_secrets.exporter_master_secret;
if (key_len > 0xffff || label_len > 250) {
/* Check that the label and key_len fit into the HkdfLabel struct as defined
* in RFC 8446, Section 7.1. key_len must fit into an uint16 and the label
* must be at most 250 bytes long. (The struct allows up to 256 bytes for
* the label, but it is prefixed with "tls13 ".) */
if (key_len > UINT16_MAX || label_len > 250) {
return MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
}