library/psa_crypto_mac.c

/*
 *  PSA MAC layer on top of Mbed TLS software crypto
 */
/*
 *  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.
 */

#include "common.h"

#if defined(MBEDTLS_PSA_CRYPTO_C)

#include <psa/crypto.h>
#include "psa_crypto_core.h"
#include "psa_crypto_cipher.h"
#include "psa_crypto_mac.h"
#include <mbedtls/md.h>

#include <mbedtls/error.h>
#include <string.h>

#if defined(MBEDTLS_PSA_BUILTIN_ALG_HMAC)
static psa_status_t psa_hmac_abort_internal(
    mbedtls_psa_hmac_operation_t *hmac )
{
    mbedtls_platform_zeroize( hmac->opad, sizeof( hmac->opad ) );
    return( psa_hash_abort( &hmac->hash_ctx ) );
}

static psa_status_t psa_hmac_setup_internal(
    mbedtls_psa_hmac_operation_t *hmac,
    const uint8_t *key,
    size_t key_length,
    psa_algorithm_t hash_alg )
{
    uint8_t ipad[PSA_HMAC_MAX_HASH_BLOCK_SIZE];
    size_t i;
    size_t hash_size = PSA_HASH_LENGTH( hash_alg );
    size_t block_size = PSA_HASH_BLOCK_LENGTH( hash_alg );
    psa_status_t status;

    hmac->alg = hash_alg;

    /* Sanity checks on block_size, to guarantee that there won't be a buffer
     * overflow below. This should never trigger if the hash algorithm
     * is implemented correctly. */
    /* The size checks against the ipad and opad buffers cannot be written
     * `block_size > sizeof( ipad ) || block_size > sizeof( hmac->opad )`
     * because that triggers -Wlogical-op on GCC 7.3. */
    if( block_size > sizeof( ipad ) )
        return( PSA_ERROR_NOT_SUPPORTED );
    if( block_size > sizeof( hmac->opad ) )
        return( PSA_ERROR_NOT_SUPPORTED );
    if( block_size < hash_size )
        return( PSA_ERROR_NOT_SUPPORTED );

    if( key_length > block_size )
    {
        status = psa_hash_compute( hash_alg, key, key_length,
                                   ipad, sizeof( ipad ), &key_length );
        if( status != PSA_SUCCESS )
            goto cleanup;
    }
    /* A 0-length key is not commonly used in HMAC when used as a MAC,
     * but it is permitted. It is common when HMAC is used in HKDF, for
     * example. Don't call `memcpy` in the 0-length because `key` could be
     * an invalid pointer which would make the behavior undefined. */
    else if( key_length != 0 )
        memcpy( ipad, key, key_length );

    /* ipad contains the key followed by garbage. Xor and fill with 0x36
     * to create the ipad value. */
    for( i = 0; i < key_length; i++ )
        ipad[i] ^= 0x36;
    memset( ipad + key_length, 0x36, block_size - key_length );

    /* Copy the key material from ipad to opad, flipping the requisite bits,
     * and filling the rest of opad with the requisite constant. */
    for( i = 0; i < key_length; i++ )
        hmac->opad[i] = ipad[i] ^ 0x36 ^ 0x5C;
    memset( hmac->opad + key_length, 0x5C, block_size - key_length );

    status = psa_hash_setup( &hmac->hash_ctx, hash_alg );
    if( status != PSA_SUCCESS )
        goto cleanup;

    status = psa_hash_update( &hmac->hash_ctx, ipad, block_size );

cleanup:
    mbedtls_platform_zeroize( ipad, sizeof( ipad ) );

    return( status );
}

static psa_status_t psa_hmac_update_internal(
    mbedtls_psa_hmac_operation_t *hmac,
    const uint8_t *data,
    size_t data_length )
{
    return( psa_hash_update( &hmac->hash_ctx, data, data_length ) );
}

static psa_status_t psa_hmac_finish_internal(
    mbedtls_psa_hmac_operation_t *hmac,
    uint8_t *mac,
    size_t mac_size )
{
    uint8_t tmp[PSA_HASH_MAX_SIZE];
    psa_algorithm_t hash_alg = hmac->alg;
    size_t hash_size = 0;
    size_t block_size = PSA_HASH_BLOCK_LENGTH( hash_alg );
    psa_status_t status;

    status = psa_hash_finish( &hmac->hash_ctx, tmp, sizeof( tmp ), &hash_size );
    if( status != PSA_SUCCESS )
        return( status );
    /* From here on, tmp needs to be wiped. */

    status = psa_hash_setup( &hmac->hash_ctx, hash_alg );
    if( status != PSA_SUCCESS )
        goto exit;

    status = psa_hash_update( &hmac->hash_ctx, hmac->opad, block_size );
    if( status != PSA_SUCCESS )
        goto exit;

    status = psa_hash_update( &hmac->hash_ctx, tmp, hash_size );
    if( status != PSA_SUCCESS )
        goto exit;

    status = psa_hash_finish( &hmac->hash_ctx, tmp, sizeof( tmp ), &hash_size );
    if( status != PSA_SUCCESS )
        goto exit;

    memcpy( mac, tmp, mac_size );

exit:
    mbedtls_platform_zeroize( tmp, hash_size );
    return( status );
}
#endif /* MBEDTLS_PSA_BUILTIN_ALG_HMAC */

#if defined(MBEDTLS_PSA_BUILTIN_ALG_CMAC)
static psa_status_t cmac_setup( mbedtls_psa_mac_operation_t *operation,
                                const psa_key_attributes_t *attributes,
                                const uint8_t *key_buffer )
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

#if defined(PSA_WANT_KEY_TYPE_DES)
    /* Mbed TLS CMAC does not accept 3DES with only two keys, nor does it accept
     * to do CMAC with pure DES, so return NOT_SUPPORTED here. */
    if( psa_get_key_type( attributes ) == PSA_KEY_TYPE_DES &&
        ( psa_get_key_bits( attributes ) == 64 ||
          psa_get_key_bits( attributes ) == 128 ) )
        return( PSA_ERROR_NOT_SUPPORTED );
#endif

    const mbedtls_cipher_info_t * cipher_info =
        mbedtls_cipher_info_from_psa(
            PSA_ALG_CMAC,
            psa_get_key_type( attributes ),
            psa_get_key_bits( attributes ),
            NULL );

    if( cipher_info == NULL )
        return( PSA_ERROR_NOT_SUPPORTED );

    ret = mbedtls_cipher_setup( &operation->ctx.cmac, cipher_info );
    if( ret != 0 )
        goto exit;

    ret = mbedtls_cipher_cmac_starts( &operation->ctx.cmac,
                                      key_buffer,
                                      psa_get_key_bits( attributes ) );
exit:
    return( mbedtls_to_psa_error( ret ) );
}
#endif /* MBEDTLS_PSA_BUILTIN_ALG_CMAC */

#if defined(MBEDTLS_PSA_BUILTIN_ALG_HMAC) || \
    defined(MBEDTLS_PSA_BUILTIN_ALG_CMAC)

/* Initialize this driver's MAC operation structure. Once this function has been
 * called, mbedtls_psa_mac_abort can run and will do the right thing. */
static psa_status_t mac_init(
    mbedtls_psa_mac_operation_t *operation,
    psa_algorithm_t alg )
{
    psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;

    operation->alg = alg;

#if defined(MBEDTLS_PSA_BUILTIN_ALG_CMAC)
    if( PSA_ALG_FULL_LENGTH_MAC( operation->alg ) == PSA_ALG_CMAC )
    {
        mbedtls_cipher_init( &operation->ctx.cmac );
        status = PSA_SUCCESS;
    }
    else
#endif /* MBEDTLS_PSA_BUILTIN_ALG_CMAC */
#if defined(MBEDTLS_PSA_BUILTIN_ALG_HMAC)
    if( PSA_ALG_IS_HMAC( operation->alg ) )
    {
        /* We'll set up the hash operation later in psa_hmac_setup_internal. */
        operation->ctx.hmac.alg = 0;
        status = PSA_SUCCESS;
    }
    else
#endif /* MBEDTLS_PSA_BUILTIN_ALG_HMAC */
    {
        (void) operation;
        status = PSA_ERROR_NOT_SUPPORTED;
    }

    if( status != PSA_SUCCESS )
        memset( operation, 0, sizeof( *operation ) );
    return( status );
}

psa_status_t mbedtls_psa_mac_abort( mbedtls_psa_mac_operation_t *operation )
{
    if( operation->alg == 0 )
    {
        /* The object has (apparently) been initialized but it is not
         * in use. It's ok to call abort on such an object, and there's
         * nothing to do. */
        return( PSA_SUCCESS );
    }
    else
#if defined(MBEDTLS_PSA_BUILTIN_ALG_CMAC)
    if( PSA_ALG_FULL_LENGTH_MAC( operation->alg ) == PSA_ALG_CMAC )
    {
        mbedtls_cipher_free( &operation->ctx.cmac );
    }
    else
#endif /* MBEDTLS_PSA_BUILTIN_ALG_CMAC */
#if defined(MBEDTLS_PSA_BUILTIN_ALG_HMAC)
    if( PSA_ALG_IS_HMAC( operation->alg ) )
    {
        psa_hmac_abort_internal( &operation->ctx.hmac );
    }
    else
#endif /* MBEDTLS_PSA_BUILTIN_ALG_HMAC */
    {
        /* Sanity check (shouldn't happen: operation->alg should
         * always have been initialized to a valid value). */
        goto bad_state;
    }

    operation->alg = 0;

    return( PSA_SUCCESS );

bad_state:
    /* If abort is called on an uninitialized object, we can't trust
     * anything. Wipe the object in case it contains confidential data.
     * This may result in a memory leak if a pointer gets overwritten,
     * but it's too late to do anything about this. */
    memset( operation, 0, sizeof( *operation ) );
    return( PSA_ERROR_BAD_STATE );
}

static psa_status_t psa_mac_setup( mbedtls_psa_mac_operation_t *operation,
                                   const psa_key_attributes_t *attributes,
                                   const uint8_t *key_buffer,
                                   size_t key_buffer_size,
                                   psa_algorithm_t alg )
{
    psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;

    /* A context must be freshly initialized before it can be set up. */
    if( operation->alg != 0 )
        return( PSA_ERROR_BAD_STATE );

    status = mac_init( operation, alg );
    if( status != PSA_SUCCESS )
        return( status );

#if defined(MBEDTLS_PSA_BUILTIN_ALG_CMAC)
    if( PSA_ALG_FULL_LENGTH_MAC( alg ) == PSA_ALG_CMAC )
    {
        /* Key buffer size for CMAC is dictated by the key bits set on the
         * attributes, and previously validated by the core on key import. */
        (void) key_buffer_size;
        status = cmac_setup( operation, attributes, key_buffer );
    }
    else
#endif /* MBEDTLS_PSA_BUILTIN_ALG_CMAC */
#if defined(MBEDTLS_PSA_BUILTIN_ALG_HMAC)
    if( PSA_ALG_IS_HMAC( alg ) )
    {
        status = psa_hmac_setup_internal( &operation->ctx.hmac,
                                          key_buffer,
                                          key_buffer_size,
                                          PSA_ALG_HMAC_GET_HASH( alg ) );
    }
    else
#endif /* MBEDTLS_PSA_BUILTIN_ALG_HMAC */
    {
        (void) attributes;
        (void) key_buffer;
        (void) key_buffer_size;
        status = PSA_ERROR_NOT_SUPPORTED;
    }

    if( status != PSA_SUCCESS )
        mbedtls_psa_mac_abort( operation );

    return( status );
}

psa_status_t mbedtls_psa_mac_sign_setup(
    mbedtls_psa_mac_operation_t *operation,
    const psa_key_attributes_t *attributes,
    const uint8_t *key_buffer,
    size_t key_buffer_size,
    psa_algorithm_t alg )
{
    return( psa_mac_setup( operation, attributes,
                           key_buffer, key_buffer_size, alg ) );
}

psa_status_t mbedtls_psa_mac_verify_setup(
    mbedtls_psa_mac_operation_t *operation,
    const psa_key_attributes_t *attributes,
    const uint8_t *key_buffer,
    size_t key_buffer_size,
    psa_algorithm_t alg )
{
    return( psa_mac_setup( operation, attributes,
                           key_buffer, key_buffer_size, alg ) );
}

psa_status_t mbedtls_psa_mac_update(
    mbedtls_psa_mac_operation_t *operation,
    const uint8_t *input,
    size_t input_length )
{
    if( operation->alg == 0 )
        return( PSA_ERROR_BAD_STATE );

#if defined(MBEDTLS_PSA_BUILTIN_ALG_CMAC)
    if( PSA_ALG_FULL_LENGTH_MAC( operation->alg ) == PSA_ALG_CMAC )
    {
        return( mbedtls_to_psa_error(
                    mbedtls_cipher_cmac_update( &operation->ctx.cmac,
                                                input, input_length ) ) );
    }
    else
#endif /* MBEDTLS_PSA_BUILTIN_ALG_CMAC */
#if defined(MBEDTLS_PSA_BUILTIN_ALG_HMAC)
    if( PSA_ALG_IS_HMAC( operation->alg ) )
    {
        return( psa_hmac_update_internal( &operation->ctx.hmac,
                                          input, input_length ) );
    }
    else
#endif /* MBEDTLS_PSA_BUILTIN_ALG_HMAC */
    {
        /* This shouldn't happen if `operation` was initialized by
         * a setup function. */
        (void) input;
        (void) input_length;
        return( PSA_ERROR_BAD_STATE );
    }
}

static psa_status_t psa_mac_finish_internal(
    mbedtls_psa_mac_operation_t *operation,
    uint8_t *mac, size_t mac_size )
{
#if defined(MBEDTLS_PSA_BUILTIN_ALG_CMAC)
    if( PSA_ALG_FULL_LENGTH_MAC( operation->alg ) == PSA_ALG_CMAC )
    {
        uint8_t tmp[PSA_BLOCK_CIPHER_BLOCK_MAX_SIZE];
        int ret = mbedtls_cipher_cmac_finish( &operation->ctx.cmac, tmp );
        if( ret == 0 )
            memcpy( mac, tmp, mac_size );
        mbedtls_platform_zeroize( tmp, sizeof( tmp ) );
        return( mbedtls_to_psa_error( ret ) );
    }
    else
#endif /* MBEDTLS_PSA_BUILTIN_ALG_CMAC */
#if defined(MBEDTLS_PSA_BUILTIN_ALG_HMAC)
    if( PSA_ALG_IS_HMAC( operation->alg ) )
    {
        return( psa_hmac_finish_internal( &operation->ctx.hmac,
                                          mac, mac_size ) );
    }
    else
#endif /* MBEDTLS_PSA_BUILTIN_ALG_HMAC */
    {
        /* This shouldn't happen if `operation` was initialized by
         * a setup function. */
        (void) operation;
        (void) mac;
        (void) mac_size;
        return( PSA_ERROR_BAD_STATE );
    }
}

psa_status_t mbedtls_psa_mac_sign_finish(
    mbedtls_psa_mac_operation_t *operation,
    uint8_t *mac,
    size_t mac_size,
    size_t *mac_length )
{
    psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;

    if( operation->alg == 0 )
        return( PSA_ERROR_BAD_STATE );

    status = psa_mac_finish_internal( operation, mac, mac_size );
    if( status == PSA_SUCCESS )
        *mac_length = mac_size;

    return( status );
}

psa_status_t mbedtls_psa_mac_verify_finish(
    mbedtls_psa_mac_operation_t *operation,
    const uint8_t *mac,
    size_t mac_length )
{
    uint8_t actual_mac[PSA_MAC_MAX_SIZE];
    psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;

    if( operation->alg == 0 )
        return( PSA_ERROR_BAD_STATE );

    /* Consistency check: requested MAC length fits our local buffer */
    if( mac_length > sizeof( actual_mac ) )
        return( PSA_ERROR_INVALID_ARGUMENT );

    status = psa_mac_finish_internal( operation, actual_mac, mac_length );
    if( status != PSA_SUCCESS )
        goto cleanup;

    if( mbedtls_psa_safer_memcmp( mac, actual_mac, mac_length ) != 0 )
        status = PSA_ERROR_INVALID_SIGNATURE;

cleanup:
    mbedtls_platform_zeroize( actual_mac, sizeof( actual_mac ) );

    return( status );
}

psa_status_t mbedtls_psa_mac_compute(
    const psa_key_attributes_t *attributes,
    const uint8_t *key_buffer,
    size_t key_buffer_size,
    psa_algorithm_t alg,
    const uint8_t *input,
    size_t input_length,
    uint8_t *mac,
    size_t mac_size,
    size_t *mac_length )
{
    psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
    mbedtls_psa_mac_operation_t operation = MBEDTLS_PSA_MAC_OPERATION_INIT;

    status = psa_mac_setup( &operation,
                            attributes, key_buffer, key_buffer_size,
                            alg );
    if( status != PSA_SUCCESS )
        goto exit;

    if( input_length > 0 )
    {
        status = mbedtls_psa_mac_update( &operation, input, input_length );
        if( status != PSA_SUCCESS )
            goto exit;
    }

    status = psa_mac_finish_internal( &operation, mac, mac_size );
    if( status == PSA_SUCCESS )
        *mac_length = mac_size;

exit:
    mbedtls_psa_mac_abort( &operation );

    return( status );
}

#endif /* MBEDTLS_PSA_BUILTIN_ALG_HMAC || MBEDTLS_PSA_BUILTIN_ALG_CMAC */

#endif /* MBEDTLS_PSA_CRYPTO_C */