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Simplify mbedtls_ssl_tls13_exporter

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RFC 8446 made it look like we can't use Derive-Secret for the second
step, but actually, Transcript-Hash and Hash are the same thing, so we
can.

Signed-off-by: Max Fillinger <maximilian.fillinger@foxcrypto.com>
This commit is contained in:
Max Fillinger 2024-08-12 11:20:39 +02:00
parent c7986427d4
commit 334c367052
1 changed files with 4 additions and 13 deletions
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17
library/ssl_tls13_keys.c
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@ -1832,26 +1832,17 @@ int mbedtls_ssl_tls13_exporter(const psa_algorithm_t hash_alg,
{ {
size_t hash_len = PSA_HASH_LENGTH(hash_alg); size_t hash_len = PSA_HASH_LENGTH(hash_alg);
unsigned char hkdf_secret[MBEDTLS_TLS1_3_MD_MAX_SIZE]; unsigned char hkdf_secret[MBEDTLS_TLS1_3_MD_MAX_SIZE];
unsigned char hashed_context[PSA_HASH_MAX_SIZE];
size_t hashed_context_len = 0;
int ret = 0; int ret = 0;
psa_status_t status = 0;
ret = mbedtls_ssl_tls13_derive_secret(hash_alg, secret, secret_len, label, label_len, NULL, 0, ret = mbedtls_ssl_tls13_derive_secret(hash_alg, secret, secret_len, label, label_len, NULL, 0,
MBEDTLS_SSL_TLS1_3_CONTEXT_UNHASHED, hkdf_secret, hash_len); MBEDTLS_SSL_TLS1_3_CONTEXT_UNHASHED, hkdf_secret, hash_len);
if (ret != 0) { if (ret != 0) {
goto exit; goto exit;
} }
ret = mbedtls_ssl_tls13_derive_secret(hash_alg, hkdf_secret, hash_len,
status = psa_hash_compute(hash_alg, context_value, context_len, hashed_context, hash_len, &hashed_context_len); MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN(exporter),
if (status != PSA_SUCCESS) { context_value, context_len, MBEDTLS_SSL_TLS1_3_CONTEXT_UNHASHED,
ret = PSA_TO_MBEDTLS_ERR(status); out, out_len);
goto exit;
}
ret = mbedtls_ssl_tls13_hkdf_expand_label(hash_alg, hkdf_secret, hash_len,
MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN(exporter),
hashed_context, hashed_context_len,
out, out_len);
exit: exit:
mbedtls_platform_zeroize(hkdf_secret, sizeof(hkdf_secret)); mbedtls_platform_zeroize(hkdf_secret, sizeof(hkdf_secret));