tests/src/psa_exercise_key.c

/** Code to exercise a PSA key object, i.e. validate that it seems well-formed
 * and can do what it is supposed to do.
 */

/*
 *  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 <test/helpers.h>
#include <test/macros.h>
#include <test/psa_exercise_key.h>

#if defined(MBEDTLS_PSA_CRYPTO_C)

#include <mbedtls/asn1.h>
#include <psa/crypto.h>

#include <test/asn1_helpers.h>
#include <test/psa_crypto_helpers.h>

#if defined(MBEDTLS_PSA_CRYPTO_SE_C)
static int lifetime_is_dynamic_secure_element( psa_key_lifetime_t lifetime )
{
    return( PSA_KEY_LIFETIME_GET_LOCATION( lifetime ) !=
            PSA_KEY_LOCATION_LOCAL_STORAGE );
}
#endif

static int check_key_attributes_sanity( mbedtls_svc_key_id_t key )
{
    int ok = 0;
    psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
    psa_key_lifetime_t lifetime;
    mbedtls_svc_key_id_t id;
    psa_key_type_t type;
    size_t bits;

    PSA_ASSERT( psa_get_key_attributes( key, &attributes ) );
    lifetime = psa_get_key_lifetime( &attributes );
    id = psa_get_key_id( &attributes );
    type = psa_get_key_type( &attributes );
    bits = psa_get_key_bits( &attributes );

    /* Persistence */
    if( PSA_KEY_LIFETIME_IS_VOLATILE( lifetime ) )
    {
        TEST_ASSERT(
            ( PSA_KEY_ID_VOLATILE_MIN <=
              MBEDTLS_SVC_KEY_ID_GET_KEY_ID( id ) ) &&
            ( MBEDTLS_SVC_KEY_ID_GET_KEY_ID( id ) <=
              PSA_KEY_ID_VOLATILE_MAX ) );
    }
    else
    {
        TEST_ASSERT(
            ( PSA_KEY_ID_USER_MIN <= MBEDTLS_SVC_KEY_ID_GET_KEY_ID( id ) ) &&
            ( MBEDTLS_SVC_KEY_ID_GET_KEY_ID( id ) <= PSA_KEY_ID_USER_MAX ) );
    }
#if defined(MBEDTLS_PSA_CRYPTO_SE_C)
    /* randomly-generated 64-bit constant, should never appear in test data */
    psa_key_slot_number_t slot_number = 0xec94d4a5058a1a21;
    psa_status_t status = psa_get_key_slot_number( &attributes, &slot_number );
    if( lifetime_is_dynamic_secure_element( lifetime ) )
    {
        /* Mbed Crypto currently always exposes the slot number to
         * applications. This is not mandated by the PSA specification
         * and may change in future versions. */
        TEST_EQUAL( status, 0 );
        TEST_ASSERT( slot_number != 0xec94d4a5058a1a21 );
    }
    else
    {
        TEST_EQUAL( status, PSA_ERROR_INVALID_ARGUMENT );
    }
#endif

    /* Type and size */
    TEST_ASSERT( type != 0 );
    TEST_ASSERT( bits != 0 );
    TEST_ASSERT( bits <= PSA_MAX_KEY_BITS );
    if( PSA_KEY_TYPE_IS_UNSTRUCTURED( type ) )
        TEST_ASSERT( bits % 8 == 0 );

    /* MAX macros concerning specific key types */
    if( PSA_KEY_TYPE_IS_ECC( type ) )
        TEST_ASSERT( bits <= PSA_VENDOR_ECC_MAX_CURVE_BITS );
    else if( PSA_KEY_TYPE_IS_RSA( type ) )
        TEST_ASSERT( bits <= PSA_VENDOR_RSA_MAX_KEY_BITS );
    TEST_ASSERT( PSA_BLOCK_CIPHER_BLOCK_LENGTH( type ) <= PSA_BLOCK_CIPHER_BLOCK_MAX_SIZE );

    ok = 1;

exit:
    /*
     * Key attributes may have been returned by psa_get_key_attributes()
     * thus reset them as required.
     */
    psa_reset_key_attributes( &attributes );

    return( ok );
}

static int exercise_mac_key( mbedtls_svc_key_id_t key,
                             psa_key_usage_t usage,
                             psa_algorithm_t alg )
{
    psa_mac_operation_t operation = PSA_MAC_OPERATION_INIT;
    const unsigned char input[] = "foo";
    unsigned char mac[PSA_MAC_MAX_SIZE] = {0};
    size_t mac_length = sizeof( mac );

    if( usage & PSA_KEY_USAGE_SIGN_HASH )
    {
        PSA_ASSERT( psa_mac_sign_setup( &operation, key, alg ) );
        PSA_ASSERT( psa_mac_update( &operation,
                                    input, sizeof( input ) ) );
        PSA_ASSERT( psa_mac_sign_finish( &operation,
                                         mac, sizeof( mac ),
                                         &mac_length ) );
    }

    if( usage & PSA_KEY_USAGE_VERIFY_HASH )
    {
        psa_status_t verify_status =
            ( usage & PSA_KEY_USAGE_SIGN_HASH ?
              PSA_SUCCESS :
              PSA_ERROR_INVALID_SIGNATURE );
        PSA_ASSERT( psa_mac_verify_setup( &operation, key, alg ) );
        PSA_ASSERT( psa_mac_update( &operation,
                                    input, sizeof( input ) ) );
        TEST_EQUAL( psa_mac_verify_finish( &operation, mac, mac_length ),
                    verify_status );
    }

    return( 1 );

exit:
    psa_mac_abort( &operation );
    return( 0 );
}

static int exercise_cipher_key( mbedtls_svc_key_id_t key,
                                psa_key_usage_t usage,
                                psa_algorithm_t alg )
{
    psa_cipher_operation_t operation = PSA_CIPHER_OPERATION_INIT;
    unsigned char iv[16] = {0};
    size_t iv_length = sizeof( iv );
    const unsigned char plaintext[16] = "Hello, world...";
    unsigned char ciphertext[32] = "(wabblewebblewibblewobblewubble)";
    size_t ciphertext_length = sizeof( ciphertext );
    unsigned char decrypted[sizeof( ciphertext )];
    size_t part_length;

    if( usage & PSA_KEY_USAGE_ENCRYPT )
    {
        PSA_ASSERT( psa_cipher_encrypt_setup( &operation, key, alg ) );
        PSA_ASSERT( psa_cipher_generate_iv( &operation,
                                            iv, sizeof( iv ),
                                            &iv_length ) );
        PSA_ASSERT( psa_cipher_update( &operation,
                                       plaintext, sizeof( plaintext ),
                                       ciphertext, sizeof( ciphertext ),
                                       &ciphertext_length ) );
        PSA_ASSERT( psa_cipher_finish( &operation,
                                       ciphertext + ciphertext_length,
                                       sizeof( ciphertext ) - ciphertext_length,
                                       &part_length ) );
        ciphertext_length += part_length;
    }

    if( usage & PSA_KEY_USAGE_DECRYPT )
    {
        psa_status_t status;
        int maybe_invalid_padding = 0;
        if( ! ( usage & PSA_KEY_USAGE_ENCRYPT ) )
        {
            psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
            PSA_ASSERT( psa_get_key_attributes( key, &attributes ) );
            /* This should be PSA_CIPHER_GET_IV_SIZE but the API doesn't
             * have this macro yet. */
            iv_length = PSA_BLOCK_CIPHER_BLOCK_LENGTH(
                psa_get_key_type( &attributes ) );
            maybe_invalid_padding = ! PSA_ALG_IS_STREAM_CIPHER( alg );
            psa_reset_key_attributes( &attributes );
        }
        PSA_ASSERT( psa_cipher_decrypt_setup( &operation, key, alg ) );
        PSA_ASSERT( psa_cipher_set_iv( &operation,
                                       iv, iv_length ) );
        PSA_ASSERT( psa_cipher_update( &operation,
                                       ciphertext, ciphertext_length,
                                       decrypted, sizeof( decrypted ),
                                       &part_length ) );
        status = psa_cipher_finish( &operation,
                                    decrypted + part_length,
                                    sizeof( decrypted ) - part_length,
                                    &part_length );
        /* For a stream cipher, all inputs are valid. For a block cipher,
         * if the input is some aribtrary data rather than an actual
         ciphertext, a padding error is likely.  */
        if( maybe_invalid_padding )
            TEST_ASSERT( status == PSA_SUCCESS ||
                         status == PSA_ERROR_INVALID_PADDING );
        else
            PSA_ASSERT( status );
    }

    return( 1 );

exit:
    psa_cipher_abort( &operation );
    return( 0 );
}

static int exercise_aead_key( mbedtls_svc_key_id_t key,
                              psa_key_usage_t usage,
                              psa_algorithm_t alg )
{
    unsigned char nonce[16] = {0};
    size_t nonce_length = sizeof( nonce );
    unsigned char plaintext[16] = "Hello, world...";
    unsigned char ciphertext[48] = "(wabblewebblewibblewobblewubble)";
    size_t ciphertext_length = sizeof( ciphertext );
    size_t plaintext_length = sizeof( ciphertext );

    /* Default IV length for AES-GCM is 12 bytes */
    if( PSA_ALG_AEAD_WITH_SHORTENED_TAG( alg, 0 ) ==
        PSA_ALG_AEAD_WITH_SHORTENED_TAG( PSA_ALG_GCM, 0 ) )
    {
        nonce_length = 12;
    }

    if( usage & PSA_KEY_USAGE_ENCRYPT )
    {
        PSA_ASSERT( psa_aead_encrypt( key, alg,
                                      nonce, nonce_length,
                                      NULL, 0,
                                      plaintext, sizeof( plaintext ),
                                      ciphertext, sizeof( ciphertext ),
                                      &ciphertext_length ) );
    }

    if( usage & PSA_KEY_USAGE_DECRYPT )
    {
        psa_status_t verify_status =
            ( usage & PSA_KEY_USAGE_ENCRYPT ?
              PSA_SUCCESS :
              PSA_ERROR_INVALID_SIGNATURE );
        TEST_EQUAL( psa_aead_decrypt( key, alg,
                                      nonce, nonce_length,
                                      NULL, 0,
                                      ciphertext, ciphertext_length,
                                      plaintext, sizeof( plaintext ),
                                      &plaintext_length ),
                    verify_status );
    }

    return( 1 );

exit:
    return( 0 );
}

static int exercise_signature_key( mbedtls_svc_key_id_t key,
                                   psa_key_usage_t usage,
                                   psa_algorithm_t alg )
{
    unsigned char payload[PSA_HASH_MAX_SIZE] = {1};
    size_t payload_length = 16;
    unsigned char signature[PSA_SIGNATURE_MAX_SIZE] = {0};
    size_t signature_length = sizeof( signature );
    psa_algorithm_t hash_alg = PSA_ALG_SIGN_GET_HASH( alg );

    /* If the policy allows signing with any hash, just pick one. */
    if( PSA_ALG_IS_HASH_AND_SIGN( alg ) && hash_alg == PSA_ALG_ANY_HASH )
    {
#if defined(KNOWN_SUPPORTED_HASH_ALG)
        hash_alg = KNOWN_SUPPORTED_HASH_ALG;
        alg ^= PSA_ALG_ANY_HASH ^ hash_alg;
#else
        TEST_ASSERT( ! "No hash algorithm for hash-and-sign testing" );
#endif
    }

    if( usage & PSA_KEY_USAGE_SIGN_HASH )
    {
        /* Some algorithms require the payload to have the size of
         * the hash encoded in the algorithm. Use this input size
         * even for algorithms that allow other input sizes. */
        if( hash_alg != 0 )
            payload_length = PSA_HASH_LENGTH( hash_alg );
        PSA_ASSERT( psa_sign_hash( key, alg,
                                   payload, payload_length,
                                   signature, sizeof( signature ),
                                   &signature_length ) );
    }

    if( usage & PSA_KEY_USAGE_VERIFY_HASH )
    {
        psa_status_t verify_status =
            ( usage & PSA_KEY_USAGE_SIGN_HASH ?
              PSA_SUCCESS :
              PSA_ERROR_INVALID_SIGNATURE );
        TEST_EQUAL( psa_verify_hash( key, alg,
                                     payload, payload_length,
                                     signature, signature_length ),
                    verify_status );
    }

    return( 1 );

exit:
    return( 0 );
}

static int exercise_asymmetric_encryption_key( mbedtls_svc_key_id_t key,
                                               psa_key_usage_t usage,
                                               psa_algorithm_t alg )
{
    unsigned char plaintext[256] = "Hello, world...";
    unsigned char ciphertext[256] = "(wabblewebblewibblewobblewubble)";
    size_t ciphertext_length = sizeof( ciphertext );
    size_t plaintext_length = 16;

    if( usage & PSA_KEY_USAGE_ENCRYPT )
    {
        PSA_ASSERT( psa_asymmetric_encrypt( key, alg,
                                            plaintext, plaintext_length,
                                            NULL, 0,
                                            ciphertext, sizeof( ciphertext ),
                                            &ciphertext_length ) );
    }

    if( usage & PSA_KEY_USAGE_DECRYPT )
    {
        psa_status_t status =
            psa_asymmetric_decrypt( key, alg,
                                    ciphertext, ciphertext_length,
                                    NULL, 0,
                                    plaintext, sizeof( plaintext ),
                                    &plaintext_length );
        TEST_ASSERT( status == PSA_SUCCESS ||
                     ( ( usage & PSA_KEY_USAGE_ENCRYPT ) == 0 &&
                       ( status == PSA_ERROR_INVALID_ARGUMENT ||
                         status == PSA_ERROR_INVALID_PADDING ) ) );
    }

    return( 1 );

exit:
    return( 0 );
}

int mbedtls_test_psa_setup_key_derivation_wrap(
    psa_key_derivation_operation_t* operation,
    mbedtls_svc_key_id_t key,
    psa_algorithm_t alg,
    const unsigned char* input1, size_t input1_length,
    const unsigned char* input2, size_t input2_length,
    size_t capacity )
{
    PSA_ASSERT( psa_key_derivation_setup( operation, alg ) );
    if( PSA_ALG_IS_HKDF( alg ) )
    {
        PSA_ASSERT( psa_key_derivation_input_bytes( operation,
                                                    PSA_KEY_DERIVATION_INPUT_SALT,
                                                    input1, input1_length ) );
        PSA_ASSERT( psa_key_derivation_input_key( operation,
                                                  PSA_KEY_DERIVATION_INPUT_SECRET,
                                                  key ) );
        PSA_ASSERT( psa_key_derivation_input_bytes( operation,
                                                    PSA_KEY_DERIVATION_INPUT_INFO,
                                                    input2,
                                                    input2_length ) );
    }
    else if( PSA_ALG_IS_TLS12_PRF( alg ) ||
             PSA_ALG_IS_TLS12_PSK_TO_MS( alg ) )
    {
        PSA_ASSERT( psa_key_derivation_input_bytes( operation,
                                                    PSA_KEY_DERIVATION_INPUT_SEED,
                                                    input1, input1_length ) );
        PSA_ASSERT( psa_key_derivation_input_key( operation,
                                                  PSA_KEY_DERIVATION_INPUT_SECRET,
                                                  key ) );
        PSA_ASSERT( psa_key_derivation_input_bytes( operation,
                                                    PSA_KEY_DERIVATION_INPUT_LABEL,
                                                    input2, input2_length ) );
    }
    else
    {
        TEST_ASSERT( ! "Key derivation algorithm not supported" );
    }

    if( capacity != SIZE_MAX )
        PSA_ASSERT( psa_key_derivation_set_capacity( operation, capacity ) );

    return( 1 );

exit:
    return( 0 );
}


static int exercise_key_derivation_key( mbedtls_svc_key_id_t key,
                                        psa_key_usage_t usage,
                                        psa_algorithm_t alg )
{
    psa_key_derivation_operation_t operation = PSA_KEY_DERIVATION_OPERATION_INIT;
    unsigned char input1[] = "Input 1";
    size_t input1_length = sizeof( input1 );
    unsigned char input2[] = "Input 2";
    size_t input2_length = sizeof( input2 );
    unsigned char output[1];
    size_t capacity = sizeof( output );

    if( usage & PSA_KEY_USAGE_DERIVE )
    {
        if( !mbedtls_test_psa_setup_key_derivation_wrap( &operation, key, alg,
                                                         input1, input1_length,
                                                         input2, input2_length,
                                                         capacity ) )
            goto exit;

        PSA_ASSERT( psa_key_derivation_output_bytes( &operation,
                                                     output,
                                                     capacity ) );
        PSA_ASSERT( psa_key_derivation_abort( &operation ) );
    }

    return( 1 );

exit:
    return( 0 );
}

/* We need two keys to exercise key agreement. Exercise the
 * private key against its own public key. */
psa_status_t mbedtls_test_psa_key_agreement_with_self(
    psa_key_derivation_operation_t *operation,
    mbedtls_svc_key_id_t key )
{
    psa_key_type_t private_key_type;
    psa_key_type_t public_key_type;
    size_t key_bits;
    uint8_t *public_key = NULL;
    size_t public_key_length;
    /* Return GENERIC_ERROR if something other than the final call to
     * psa_key_derivation_key_agreement fails. This isn't fully satisfactory,
     * but it's good enough: callers will report it as a failed test anyway. */
    psa_status_t status = PSA_ERROR_GENERIC_ERROR;
    psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;

    PSA_ASSERT( psa_get_key_attributes( key, &attributes ) );
    private_key_type = psa_get_key_type( &attributes );
    key_bits = psa_get_key_bits( &attributes );
    public_key_type = PSA_KEY_TYPE_PUBLIC_KEY_OF_KEY_PAIR( private_key_type );
    public_key_length = PSA_EXPORT_PUBLIC_KEY_OUTPUT_SIZE( public_key_type, key_bits );
    ASSERT_ALLOC( public_key, public_key_length );
    PSA_ASSERT( psa_export_public_key( key, public_key, public_key_length,
                                       &public_key_length ) );

    status = psa_key_derivation_key_agreement(
        operation, PSA_KEY_DERIVATION_INPUT_SECRET, key,
        public_key, public_key_length );
exit:
    /*
     * Key attributes may have been returned by psa_get_key_attributes()
     * thus reset them as required.
     */
    psa_reset_key_attributes( &attributes );

    mbedtls_free( public_key );
    return( status );
}

/* We need two keys to exercise key agreement. Exercise the
 * private key against its own public key. */
psa_status_t mbedtls_test_psa_raw_key_agreement_with_self(
    psa_algorithm_t alg,
    mbedtls_svc_key_id_t key )
{
    psa_key_type_t private_key_type;
    psa_key_type_t public_key_type;
    size_t key_bits;
    uint8_t *public_key = NULL;
    size_t public_key_length;
    uint8_t output[1024];
    size_t output_length;
    /* Return GENERIC_ERROR if something other than the final call to
     * psa_key_derivation_key_agreement fails. This isn't fully satisfactory,
     * but it's good enough: callers will report it as a failed test anyway. */
    psa_status_t status = PSA_ERROR_GENERIC_ERROR;
    psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;

    PSA_ASSERT( psa_get_key_attributes( key, &attributes ) );
    private_key_type = psa_get_key_type( &attributes );
    key_bits = psa_get_key_bits( &attributes );
    public_key_type = PSA_KEY_TYPE_PUBLIC_KEY_OF_KEY_PAIR( private_key_type );
    public_key_length = PSA_EXPORT_PUBLIC_KEY_OUTPUT_SIZE( public_key_type, key_bits );
    ASSERT_ALLOC( public_key, public_key_length );
    PSA_ASSERT( psa_export_public_key( key,
                                       public_key, public_key_length,
                                       &public_key_length ) );

    status = psa_raw_key_agreement( alg, key,
                                    public_key, public_key_length,
                                    output, sizeof( output ), &output_length );
    if ( status == PSA_SUCCESS )
    {
        TEST_ASSERT( output_length <=
                     PSA_RAW_KEY_AGREEMENT_OUTPUT_SIZE( private_key_type,
                                                        key_bits ) );
        TEST_ASSERT( output_length <=
                     PSA_RAW_KEY_AGREEMENT_OUTPUT_MAX_SIZE );
    }

exit:
    /*
     * Key attributes may have been returned by psa_get_key_attributes()
     * thus reset them as required.
     */
    psa_reset_key_attributes( &attributes );

    mbedtls_free( public_key );
    return( status );
}

static int exercise_raw_key_agreement_key( mbedtls_svc_key_id_t key,
                                           psa_key_usage_t usage,
                                           psa_algorithm_t alg )
{
    int ok = 0;

    if( usage & PSA_KEY_USAGE_DERIVE )
    {
        /* We need two keys to exercise key agreement. Exercise the
         * private key against its own public key. */
        PSA_ASSERT( mbedtls_test_psa_raw_key_agreement_with_self( alg, key ) );
    }
    ok = 1;

exit:
    return( ok );
}

static int exercise_key_agreement_key( mbedtls_svc_key_id_t key,
                                       psa_key_usage_t usage,
                                       psa_algorithm_t alg )
{
    psa_key_derivation_operation_t operation = PSA_KEY_DERIVATION_OPERATION_INIT;
    unsigned char output[1];
    int ok = 0;

    if( usage & PSA_KEY_USAGE_DERIVE )
    {
        /* We need two keys to exercise key agreement. Exercise the
         * private key against its own public key. */
        PSA_ASSERT( psa_key_derivation_setup( &operation, alg ) );
        PSA_ASSERT( mbedtls_test_psa_key_agreement_with_self( &operation, key ) );
        PSA_ASSERT( psa_key_derivation_output_bytes( &operation,
                                                     output,
                                                     sizeof( output ) ) );
        PSA_ASSERT( psa_key_derivation_abort( &operation ) );
    }
    ok = 1;

exit:
    return( ok );
}

int mbedtls_test_psa_exported_key_sanity_check(
    psa_key_type_t type, size_t bits,
    const uint8_t *exported, size_t exported_length )
{
    TEST_ASSERT( exported_length <= PSA_EXPORT_KEY_OUTPUT_SIZE( type, bits ) );

    if( PSA_KEY_TYPE_IS_UNSTRUCTURED( type ) )
        TEST_EQUAL( exported_length, PSA_BITS_TO_BYTES( bits ) );
    else

#if defined(MBEDTLS_RSA_C) && defined(MBEDTLS_PK_PARSE_C)
    if( type == PSA_KEY_TYPE_RSA_KEY_PAIR )
    {
        uint8_t *p = (uint8_t*) exported;
        const uint8_t *end = exported + exported_length;
        size_t len;
        /*   RSAPrivateKey ::= SEQUENCE {
         *       version             INTEGER,  -- must be 0
         *       modulus             INTEGER,  -- n
         *       publicExponent      INTEGER,  -- e
         *       privateExponent     INTEGER,  -- d
         *       prime1              INTEGER,  -- p
         *       prime2              INTEGER,  -- q
         *       exponent1           INTEGER,  -- d mod (p-1)
         *       exponent2           INTEGER,  -- d mod (q-1)
         *       coefficient         INTEGER,  -- (inverse of q) mod p
         *   }
         */
        TEST_EQUAL( mbedtls_asn1_get_tag( &p, end, &len,
                                          MBEDTLS_ASN1_SEQUENCE |
                                          MBEDTLS_ASN1_CONSTRUCTED ), 0 );
        TEST_EQUAL( p + len, end );
        if( ! mbedtls_test_asn1_skip_integer( &p, end, 0, 0, 0 ) )
            goto exit;
        if( ! mbedtls_test_asn1_skip_integer( &p, end, bits, bits, 1 ) )
            goto exit;
        if( ! mbedtls_test_asn1_skip_integer( &p, end, 2, bits, 1 ) )
            goto exit;
        /* Require d to be at least half the size of n. */
        if( ! mbedtls_test_asn1_skip_integer( &p, end, bits / 2, bits, 1 ) )
            goto exit;
        /* Require p and q to be at most half the size of n, rounded up. */
        if( ! mbedtls_test_asn1_skip_integer( &p, end, bits / 2, bits / 2 + 1, 1 ) )
            goto exit;
        if( ! mbedtls_test_asn1_skip_integer( &p, end, bits / 2, bits / 2 + 1, 1 ) )
            goto exit;
        if( ! mbedtls_test_asn1_skip_integer( &p, end, 1, bits / 2 + 1, 0 ) )
            goto exit;
        if( ! mbedtls_test_asn1_skip_integer( &p, end, 1, bits / 2 + 1, 0 ) )
            goto exit;
        if( ! mbedtls_test_asn1_skip_integer( &p, end, 1, bits / 2 + 1, 0 ) )
            goto exit;
        TEST_EQUAL( p, end );

        TEST_ASSERT( exported_length <= PSA_EXPORT_KEY_PAIR_MAX_SIZE );
    }
    else
#endif /* MBEDTLS_RSA_C */

#if defined(MBEDTLS_ECP_C)
    if( PSA_KEY_TYPE_IS_ECC_KEY_PAIR( type ) )
    {
        /* Just the secret value */
        TEST_EQUAL( exported_length, PSA_BITS_TO_BYTES( bits ) );

        TEST_ASSERT( exported_length <= PSA_EXPORT_KEY_PAIR_MAX_SIZE );
    }
    else
#endif /* MBEDTLS_ECP_C */

#if defined(MBEDTLS_RSA_C)
    if( type == PSA_KEY_TYPE_RSA_PUBLIC_KEY )
    {
        uint8_t *p = (uint8_t*) exported;
        const uint8_t *end = exported + exported_length;
        size_t len;
        /*   RSAPublicKey ::= SEQUENCE {
         *      modulus            INTEGER,    -- n
         *      publicExponent     INTEGER  }  -- e
         */
        TEST_EQUAL( mbedtls_asn1_get_tag( &p, end, &len,
                                          MBEDTLS_ASN1_SEQUENCE |
                                          MBEDTLS_ASN1_CONSTRUCTED ),
                    0 );
        TEST_EQUAL( p + len, end );
        if( ! mbedtls_test_asn1_skip_integer( &p, end, bits, bits, 1 ) )
            goto exit;
        if( ! mbedtls_test_asn1_skip_integer( &p, end, 2, bits, 1 ) )
            goto exit;
        TEST_EQUAL( p, end );


        TEST_ASSERT( exported_length <=
                     PSA_EXPORT_PUBLIC_KEY_OUTPUT_SIZE( type, bits ) );
        TEST_ASSERT( exported_length <=
                     PSA_EXPORT_PUBLIC_KEY_MAX_SIZE );
    }
    else
#endif /* MBEDTLS_RSA_C */

#if defined(MBEDTLS_ECP_C)
    if( PSA_KEY_TYPE_IS_ECC_PUBLIC_KEY( type ) )
    {

        TEST_ASSERT( exported_length <=
                     PSA_EXPORT_PUBLIC_KEY_OUTPUT_SIZE( type, bits ) );
        TEST_ASSERT( exported_length <=
                     PSA_EXPORT_PUBLIC_KEY_MAX_SIZE );

        if( PSA_KEY_TYPE_ECC_GET_FAMILY( type ) == PSA_ECC_FAMILY_MONTGOMERY )
        {
            /* The representation of an ECC Montgomery public key is
             * the raw compressed point */
             TEST_EQUAL( PSA_BITS_TO_BYTES( bits ), exported_length );
        }
        else
        {
            /* The representation of an ECC Weierstrass public key is:
             *      - The byte 0x04;
             *      - `x_P` as a `ceiling(m/8)`-byte string, big-endian;
             *      - `y_P` as a `ceiling(m/8)`-byte string, big-endian;
             *      - where m is the bit size associated with the curve.
             */
            TEST_EQUAL( 1 + 2 * PSA_BITS_TO_BYTES( bits ), exported_length );
            TEST_EQUAL( exported[0], 4 );
        }
    }
    else
#endif /* MBEDTLS_ECP_C */

    {
        TEST_ASSERT( ! "Sanity check not implemented for this key type" );
    }

#if defined(MBEDTLS_DES_C)
    if( type == PSA_KEY_TYPE_DES )
    {
        /* Check the parity bits. */
        unsigned i;
        for( i = 0; i < bits / 8; i++ )
        {
            unsigned bit_count = 0;
            unsigned m;
            for( m = 1; m <= 0x100; m <<= 1 )
            {
                if( exported[i] & m )
                    ++bit_count;
            }
            TEST_ASSERT( bit_count % 2 != 0 );
        }
    }
#endif

    return( 1 );

exit:
    return( 0 );
}

static int exercise_export_key( mbedtls_svc_key_id_t key,
                                psa_key_usage_t usage )
{
    psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
    uint8_t *exported = NULL;
    size_t exported_size = 0;
    size_t exported_length = 0;
    int ok = 0;

    PSA_ASSERT( psa_get_key_attributes( key, &attributes ) );

    exported_size = PSA_EXPORT_KEY_OUTPUT_SIZE(
                        psa_get_key_type( &attributes ),
                        psa_get_key_bits( &attributes ) );
    ASSERT_ALLOC( exported, exported_size );

    if( ( usage & PSA_KEY_USAGE_EXPORT ) == 0 &&
        ! PSA_KEY_TYPE_IS_PUBLIC_KEY( psa_get_key_type( &attributes ) ) )
    {
        TEST_EQUAL( psa_export_key( key, exported,
                                    exported_size, &exported_length ),
                    PSA_ERROR_NOT_PERMITTED );
        ok = 1;
        goto exit;
    }

    PSA_ASSERT( psa_export_key( key,
                                exported, exported_size,
                                &exported_length ) );
    ok = mbedtls_test_psa_exported_key_sanity_check(
        psa_get_key_type( &attributes ), psa_get_key_bits( &attributes ),
        exported, exported_length );

exit:
    /*
     * Key attributes may have been returned by psa_get_key_attributes()
     * thus reset them as required.
     */
    psa_reset_key_attributes( &attributes );

    mbedtls_free( exported );
    return( ok );
}

static int exercise_export_public_key( mbedtls_svc_key_id_t key )
{
    psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
    psa_key_type_t public_type;
    uint8_t *exported = NULL;
    size_t exported_size = 0;
    size_t exported_length = 0;
    int ok = 0;

    PSA_ASSERT( psa_get_key_attributes( key, &attributes ) );
    if( ! PSA_KEY_TYPE_IS_ASYMMETRIC( psa_get_key_type( &attributes ) ) )
    {
        exported_size = PSA_EXPORT_KEY_OUTPUT_SIZE(
                            psa_get_key_type( &attributes ),
                            psa_get_key_bits( &attributes ) );
        ASSERT_ALLOC( exported, exported_size );

        TEST_EQUAL( psa_export_public_key( key, exported,
                                           exported_size, &exported_length ),
                    PSA_ERROR_INVALID_ARGUMENT );
        ok = 1;
        goto exit;
    }

    public_type = PSA_KEY_TYPE_PUBLIC_KEY_OF_KEY_PAIR(
        psa_get_key_type( &attributes ) );
    exported_size = PSA_EXPORT_PUBLIC_KEY_OUTPUT_SIZE( public_type,
                                                       psa_get_key_bits( &attributes ) );
    ASSERT_ALLOC( exported, exported_size );

    PSA_ASSERT( psa_export_public_key( key,
                                       exported, exported_size,
                                       &exported_length ) );
    ok = mbedtls_test_psa_exported_key_sanity_check(
        public_type, psa_get_key_bits( &attributes ),
        exported, exported_length );

exit:
    /*
     * Key attributes may have been returned by psa_get_key_attributes()
     * thus reset them as required.
     */
    psa_reset_key_attributes( &attributes );

    mbedtls_free( exported );
    return( ok );
}

int mbedtls_test_psa_exercise_key( mbedtls_svc_key_id_t key,
                                   psa_key_usage_t usage,
                                   psa_algorithm_t alg )
{
    int ok = 0;

    if( ! check_key_attributes_sanity( key ) )
        return( 0 );

    if( alg == 0 )
        ok = 1; /* If no algorihm, do nothing (used for raw data "keys"). */
    else if( PSA_ALG_IS_MAC( alg ) )
        ok = exercise_mac_key( key, usage, alg );
    else if( PSA_ALG_IS_CIPHER( alg ) )
        ok = exercise_cipher_key( key, usage, alg );
    else if( PSA_ALG_IS_AEAD( alg ) )
        ok = exercise_aead_key( key, usage, alg );
    else if( PSA_ALG_IS_SIGN( alg ) )
        ok = exercise_signature_key( key, usage, alg );
    else if( PSA_ALG_IS_ASYMMETRIC_ENCRYPTION( alg ) )
        ok = exercise_asymmetric_encryption_key( key, usage, alg );
    else if( PSA_ALG_IS_KEY_DERIVATION( alg ) )
        ok = exercise_key_derivation_key( key, usage, alg );
    else if( PSA_ALG_IS_RAW_KEY_AGREEMENT( alg ) )
        ok = exercise_raw_key_agreement_key( key, usage, alg );
    else if( PSA_ALG_IS_KEY_AGREEMENT( alg ) )
        ok = exercise_key_agreement_key( key, usage, alg );
    else
        TEST_ASSERT( ! "No code to exercise this category of algorithm" );

    ok = ok && exercise_export_key( key, usage );
    ok = ok && exercise_export_public_key( key );

exit:
    return( ok );
}

psa_key_usage_t mbedtls_test_psa_usage_to_exercise( psa_key_type_t type,
                                                    psa_algorithm_t alg )
{
    if( PSA_ALG_IS_MAC( alg ) || PSA_ALG_IS_SIGN( alg ) )
    {
        return( PSA_KEY_TYPE_IS_PUBLIC_KEY( type ) ?
                PSA_KEY_USAGE_VERIFY_HASH :
                PSA_KEY_USAGE_SIGN_HASH | PSA_KEY_USAGE_VERIFY_HASH );
    }
    else if( PSA_ALG_IS_CIPHER( alg ) || PSA_ALG_IS_AEAD( alg ) ||
             PSA_ALG_IS_ASYMMETRIC_ENCRYPTION( alg ) )
    {
        return( PSA_KEY_TYPE_IS_PUBLIC_KEY( type ) ?
                PSA_KEY_USAGE_ENCRYPT :
                PSA_KEY_USAGE_ENCRYPT | PSA_KEY_USAGE_DECRYPT );
    }
    else if( PSA_ALG_IS_KEY_DERIVATION( alg ) ||
             PSA_ALG_IS_KEY_AGREEMENT( alg ) )
    {
        return( PSA_KEY_USAGE_DERIVE );
    }
    else
    {
        return( 0 );
    }

}

#endif /* MBEDTLS_PSA_CRYPTO_C */