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Implement HKDF expand in TLS 1.3 based on PSA HMAC

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Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
This commit is contained in:
Gabor Mezei 2022-02-09 16:57:26 +01:00
parent 748ab4ae77
commit a3eecd242c
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GPG key ID: 106F5A41ECC305BD
2 changed files with 185 additions and 0 deletions
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63
library/ssl_tls13_invasive.h Normal file
View file

@ -0,0 +1,63 @@
/*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef MBEDTLS_SSL_TLS13_INVASIVE_H
#define MBEDTLS_SSL_TLS13_INVASIVE_H
#include "common.h"
#if defined(MBEDTLS_PSA_CRYPTO_C)
#include "psa/crypto.h"
#endif
#if defined(MBEDTLS_TEST_HOOKS)
#if defined(MBEDTLS_PSA_CRYPTO_C)
/**
* \brief Expand the supplied \p prk into several additional pseudorandom
* keys, which is the output of the HKDF.
*
* \param alg The HMAC algorithm to use (\c #PSA_ALG_HMAC( PSA_ALG_XXX )
* value such that PSA_ALG_XXX is a hash algorithm and
* #PSA_ALG_IS_HMAC(\p alg) is true).
* \param prk A pseudorandom key of \p prk_len bytes. \p prk is
* usually the output from the HKDF extract step.
* \param prk_len The length in bytes of \p prk.
* \param info An optional context and application specific information
* string. This can be a zero-length string.
* \param info_len The length of \p info in bytes.
* \param okm The output keying material of \p okm_len bytes.
* \param okm_len The length of the output keying material in bytes. This
* must be less than or equal to
* 255 * #PSA_HASH_LENGTH( \p alg ) bytes.
*
* \return 0 on success.
* \return #PSA_ERROR_INVALID_ARGUMENT when the parameters are invalid.
* \return An PSA_ERROR_* error for errors returned from the underlying
* PSA layer.
*/
psa_status_t mbedtls_psa_hkdf_expand( psa_algorithm_t alg,
const unsigned char *prk, size_t prk_len,
const unsigned char *info, size_t info_len,
unsigned char *okm, size_t okm_len );
#endif /* MBEDTLS_PSA_CRYPTO_C */
#endif /* MBEDTLS_TEST_HOOKS */
#endif /* MBEDTLS_SSL_TLS13_INVASIVE_H */

122
library/ssl_tls13_keys.c
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@ -30,6 +30,9 @@
#include "ssl_misc.h"
#include "ssl_tls13_keys.h"
#include "ssl_tls13_invasive.h"
#include "psa/crypto.h"
#define MBEDTLS_SSL_TLS1_3_LABEL( name, string ) \
.name = string,
@ -133,6 +136,125 @@ static void ssl_tls13_hkdf_encode_label(
*dst_len = total_hkdf_lbl_len;
}
MBEDTLS_STATIC_TESTABLE
psa_status_t mbedtls_psa_hkdf_expand( psa_algorithm_t alg,
const unsigned char *prk, size_t prk_len,
const unsigned char *info, size_t info_len,
unsigned char *okm, size_t okm_len )
{
size_t hash_len;
size_t where = 0;
size_t n;
size_t t_len = 0;
size_t i;
mbedtls_svc_key_id_t key = MBEDTLS_SVC_KEY_ID_INIT;
psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
psa_mac_operation_t operation = PSA_MAC_OPERATION_INIT;
psa_status_t ret = PSA_ERROR_CORRUPTION_DETECTED;
unsigned char t[PSA_MAC_MAX_SIZE];
if( okm == NULL )
{
return( PSA_ERROR_INVALID_ARGUMENT );
}
hash_len = PSA_HASH_LENGTH( alg );
if( prk_len < hash_len || hash_len == 0 )
{
return( PSA_ERROR_INVALID_ARGUMENT );
}
if( info == NULL )
{
info = (const unsigned char *) "";
info_len = 0;
}
n = okm_len / hash_len;
if( okm_len % hash_len != 0 )
{
n++;
}
/*
* Per RFC 5869 Section 2.3, okm_len must not exceed
* 255 times the hash length
*/
if( n > 255 )
{
return( PSA_ERROR_INVALID_ARGUMENT );
}
psa_set_key_usage_flags( &attributes, PSA_KEY_USAGE_SIGN_MESSAGE );
psa_set_key_algorithm( &attributes, alg );
psa_set_key_type( &attributes, PSA_KEY_TYPE_HMAC );
ret = psa_import_key( &attributes, prk, prk_len, &key );
if( PSA_SUCCESS != ret )
{
goto cleanup;
}
memset( t, 0, hash_len );
/*
* Compute T = T(1) | T(2) | T(3) | ... | T(N)
* Where T(N) is defined in RFC 5869 Section 2.3
*/
for( i = 1; i <= n; i++ )
{
size_t num_to_copy;
unsigned char c = i & 0xff;
size_t len;
ret = psa_mac_sign_setup( &operation, key, alg );
if( PSA_SUCCESS != ret )
{
goto cleanup;
}
ret = psa_mac_update( &operation, t, t_len );
if( PSA_SUCCESS != ret )
{
goto cleanup;
}
ret = psa_mac_update( &operation, info, info_len );
if( PSA_SUCCESS != ret )
{
goto cleanup;
}
/* The constant concatenated to the end of each T(n) is a single octet.
* */
ret = psa_mac_update( &operation, &c, 1 );
if( PSA_SUCCESS != ret )
{
goto cleanup;
}
ret = psa_mac_sign_finish( &operation, t, PSA_MAC_MAX_SIZE, &len );
if( PSA_SUCCESS != ret )
{
goto cleanup;
}
num_to_copy = i != n ? hash_len : okm_len - where;
memcpy( okm + where, t, num_to_copy );
where += hash_len;
t_len = hash_len;
}
cleanup:
psa_destroy_key( key );
mbedtls_platform_zeroize( t, sizeof( t ) );
psa_mac_abort( &operation );
return( ret );
}
int mbedtls_ssl_tls13_hkdf_expand_label(
mbedtls_md_type_t hash_alg,
const unsigned char *secret, size_t secret_len,