Add framework for simple key derivation

New key type PSA_KEY_TYPE_DERIVE. New usage flag PSA_KEY_USAGE_DERIVE.
New function psa_key_derivation.

No key derivation algorithm is implemented yet. The code may not
compile with -Wunused.

Write some unit test code for psa_key_derivation. Most of it cannot be
used yet due to the lack of a key derivation algorithm.

include/psa/crypto.h

@@ -366,6 +366,13 @@ typedef uint32_t psa_key_type_t;
  * \c alg is the HMAC algorithm or the underlying hash algorithm. */
 #define PSA_KEY_TYPE_HMAC                       ((psa_key_type_t)0x02000001)
 
+/** A secret for key derivation.
+ *
+ * The key policy determines which key derivation algorithm the key
+ * can be used for.
+ */
+#define PSA_KEY_TYPE_DERIVE                     ((psa_key_type_t)0x02000101)
+
 /** Key for an cipher, AEAD or MAC algorithm based on the AES block cipher.
  *
  * The size of the key can be 16 bytes (AES-128), 24 bytes (AES-192) or
@@ -1194,6 +1201,10 @@ typedef uint32_t psa_key_usage_t;
  */
 #define PSA_KEY_USAGE_VERIFY                    ((psa_key_usage_t)0x00000800)
 
+/** Whether the key may be used to derive other keys.
+ */
+#define PSA_KEY_USAGE_DERIVE                    ((psa_key_usage_t)0x00001000)
+
 /** The type of the key policy data structure.
  *
  * This is an implementation-defined \c struct. Applications should not
@@ -2615,6 +2626,57 @@ psa_status_t psa_generator_abort(psa_crypto_generator_t *generator);
 
 /**@}*/
 
+/** \defgroup derivation Key derivation
+ * @{
+ */
+
+/** Set up a key derivation operation.
+ *
+ * A key derivation algorithm takes three inputs: a secret input \p key and
+ * two non-secret inputs \p label and p salt.
+ * The result of this function is a byte generator which can
+ * be used to produce keys and other cryptographic material.
+ *
+ * The role of \p label and \p salt is as follows:
+ *
+ * \param[in,out] generator       The generator object to set up. It must
+ *                                have been initialized to .
+ * \param key                     Slot containing the secret key to use.
+ * \param alg                     The key derivation algorithm to compute
+ *                                (\c PSA_ALG_XXX value such that
+ *                                #PSA_ALG_IS_KEY_DERIVATION(\p alg) is true).
+ * \param[in] salt                Salt to use.
+ * \param salt_length             Size of the \p salt buffer in bytes.
+ * \param[in] label               Label to use.
+ * \param label_length            Size of the \p label buffer in bytes.
+ * \param capacity                The maximum number of bytes that the
+ *                                generator will be able to provide.
+ *
+ * \retval #PSA_SUCCESS
+ *         Success.
+ * \retval #PSA_ERROR_EMPTY_SLOT
+ * \retval #PSA_ERROR_NOT_PERMITTED
+ * \retval #PSA_ERROR_INVALID_ARGUMENT
+ *         \c key is not compatible with \c alg,
+ *         or \p capacity is too large for the specified algorithm and key.
+ * \retval #PSA_ERROR_NOT_SUPPORTED
+ *         \c alg is not supported or is not a key derivation algorithm.
+ * \retval #PSA_ERROR_INSUFFICIENT_MEMORY
+ * \retval #PSA_ERROR_COMMUNICATION_FAILURE
+ * \retval #PSA_ERROR_HARDWARE_FAILURE
+ * \retval #PSA_ERROR_TAMPERING_DETECTED
+ */
+psa_status_t psa_key_derivation(psa_crypto_generator_t *generator,
+                                psa_key_type_t key,
+                                psa_algorithm_t alg,
+                                const uint8_t *salt,
+                                size_t salt_length,
+                                const uint8_t *label,
+                                size_t label_length,
+                                size_t capacity);
+
+/**@}*/
+
 /** \defgroup generation Key generation
  * @{
  */

library/psa_crypto.c

@@ -498,8 +498,9 @@ static psa_status_t prepare_raw_data_slot( psa_key_type_t type,
             break;
 #if defined(MBEDTLS_MD_C)
         case PSA_KEY_TYPE_HMAC:
-            break;
 #endif
+        case PSA_KEY_TYPE_DERIVE:
+            break;
 #if defined(MBEDTLS_AES_C)
         case PSA_KEY_TYPE_AES:
             if( bits != 128 && bits != 192 && bits != 256 )
@@ -2651,7 +2652,8 @@ psa_status_t psa_set_key_policy( psa_key_slot_t key,
                              PSA_KEY_USAGE_ENCRYPT |
                              PSA_KEY_USAGE_DECRYPT |
                              PSA_KEY_USAGE_SIGN |
-                             PSA_KEY_USAGE_VERIFY ) ) != 0 )
+                             PSA_KEY_USAGE_VERIFY |
+                             PSA_KEY_USAGE_DERIVE ) ) != 0 )
         return( PSA_ERROR_INVALID_ARGUMENT );
 
     slot->policy = *policy;
@@ -3085,6 +3087,49 @@ exit:
 
 
 
+/****************************************************************/
+/* Key derivation */
+/****************************************************************/
+
+psa_status_t psa_key_derivation( psa_crypto_generator_t *generator,
+                                 psa_key_type_t key,
+                                 psa_algorithm_t alg,
+                                 const uint8_t *salt,
+                                 size_t salt_length,
+                                 const uint8_t *label,
+                                 size_t label_length,
+                                 size_t capacity )
+{
+    key_slot_t *slot;
+    psa_status_t status;
+
+    if( generator->alg != 0 )
+        return( PSA_ERROR_BAD_STATE );
+
+    status = psa_get_key_from_slot( key, &slot, PSA_KEY_USAGE_DERIVE, alg );
+    if( status != PSA_SUCCESS )
+        return( status );
+    if( slot->type != PSA_KEY_TYPE_DERIVE )
+        return( PSA_ERROR_INVALID_ARGUMENT );
+
+    if( ! PSA_ALG_IS_KEY_DERIVATION( alg ) )
+        return( PSA_ERROR_INVALID_ARGUMENT );
+
+    {
+        return( PSA_ERROR_NOT_SUPPORTED );
+    }
+
+    /* Set generator->alg even on failure so that abort knows what to do. */
+    generator->alg = alg;
+    if( status == PSA_SUCCESS )
+        generator->capacity = capacity;
+    else
+        psa_generator_abort( generator );
+    return( status );
+}
+
+
+
 /****************************************************************/
 /* Random generation */
 /****************************************************************/

tests/suites/test_suite_psa_crypto.data

@@ -745,6 +745,10 @@ PSA decrypt: RSA PKCS#1 v1.5, input too large
 depends_on:MBEDTLS_PK_PARSE_C:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15
 asymmetric_decrypt_fail:PSA_KEY_TYPE_RSA_KEYPAIR:"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":PSA_ALG_RSA_PKCS1V15_CRYPT:"0099ffde2fcc00c9cc01972ebfa7779b298dbbaf7f50707a7405296dd2783456fc792002f462e760500e02afa25a859ace8701cb5d3b0262116431c43af8eb08f5a88301057cf1c156a2a5193c143e7a5b03fac132b7e89e6dcd8f4c82c9b28452329c260d30bc39b3816b7c46b41b37b4850d2ae74e729f99c6621fbbe2e46872":PSA_ERROR_INVALID_ARGUMENT
 
+
+PSA key derivation: not a key derivation algorithm
+depends_on:MBEDTLS_MD_C:MBEDTLS_SHA256_C
+derive_setup:PSA_KEY_TYPE_DERIVE:"0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b":PSA_ALG_HMAC(PSA_ALG_SHA_256):"":"":42:PSA_ERROR_INVALID_ARGUMENT
 PSA generate random: 0 bytes
 generate_random:0
 

tests/suites/test_suite_psa_crypto.function

@@ -357,6 +357,36 @@ exit:
     return( 0 );
 }
 
+static int exercise_key_derivation_key( psa_key_slot_t key,
+                                        psa_key_usage_t usage,
+                                        psa_algorithm_t alg )
+{
+    psa_crypto_generator_t generator = PSA_CRYPTO_GENERATOR_INIT;
+    unsigned char label[16] = "This is a label.";
+    size_t label_length = sizeof( label );
+    unsigned char seed[16] = "abcdefghijklmnop";
+    size_t seed_length = sizeof( seed );
+    unsigned char output[1];
+
+    if( usage & PSA_KEY_USAGE_DERIVE )
+    {
+        TEST_ASSERT( psa_key_derivation( &generator,
+                                         key, alg,
+                                         label, label_length,
+                                         seed, seed_length,
+                                         sizeof( output ) ) == PSA_SUCCESS );
+        TEST_ASSERT( psa_generator_read( &generator,
+                                         output,
+                                         sizeof( output ) ) == PSA_SUCCESS );
+        TEST_ASSERT( psa_generator_abort( &generator ) == PSA_SUCCESS );
+    }
+
+    return( 1 );
+
+exit:
+    return( 0 );
+}
+
 static int exercise_key( psa_key_slot_t slot,
                          psa_key_usage_t usage,
                          psa_algorithm_t alg )
@@ -374,6 +404,8 @@ static int exercise_key( psa_key_slot_t slot,
         ok = exercise_signature_key( slot, usage, alg );
     else if( PSA_ALG_IS_ASYMMETRIC_ENCRYPTION( alg ) )
         ok = exercise_asymmetric_encryption_key( slot, usage, alg );
+    else if( PSA_ALG_IS_KEY_DERIVATION( alg ) )
+        ok = exercise_key_derivation_key( slot, usage, alg );
     else
     {
         char message[40];
@@ -657,6 +689,7 @@ void import_and_exercise_key( data_t *data,
           ( PSA_KEY_TYPE_IS_PUBLIC_KEY( type ) ?
             PSA_KEY_USAGE_ENCRYPT :
             PSA_KEY_USAGE_ENCRYPT | PSA_KEY_USAGE_DECRYPT ) :
+          PSA_ALG_IS_KEY_DERIVATION( alg ) ? PSA_KEY_USAGE_DERIVE :
           0 );
     psa_key_policy_t policy;
     psa_key_type_t got_type;
@@ -991,6 +1024,45 @@ exit:
 }
 /* END_CASE */
 
+/* BEGIN_CASE */
+void derive_key_policy( int policy_usage,
+                        int policy_alg,
+                        int key_type,
+                        data_t *key_data,
+                        int exercise_alg )
+{
+    int key_slot = 1;
+    psa_key_policy_t policy;
+    psa_crypto_generator_t generator = PSA_CRYPTO_GENERATOR_INIT;
+    psa_status_t status;
+
+    TEST_ASSERT( psa_crypto_init( ) == PSA_SUCCESS );
+
+    psa_key_policy_init( &policy );
+    psa_key_policy_set_usage( &policy, policy_usage, policy_alg );
+    TEST_ASSERT( psa_set_key_policy( key_slot, &policy ) == PSA_SUCCESS );
+
+    TEST_ASSERT( psa_import_key( key_slot, key_type,
+                                 key_data->x, key_data->len ) == PSA_SUCCESS );
+
+    status = psa_key_derivation( &generator, key_slot,
+                                 exercise_alg,
+                                 NULL, 0,
+                                 NULL, 0,
+                                 1 );
+    if( policy_alg == exercise_alg &&
+        ( policy_usage & PSA_KEY_USAGE_DERIVE ) != 0 )
+        TEST_ASSERT( status == PSA_SUCCESS );
+    else
+        TEST_ASSERT( status == PSA_ERROR_NOT_PERMITTED );
+
+exit:
+    psa_generator_abort( &generator );
+    psa_destroy_key( key_slot );
+    mbedtls_psa_crypto_free( );
+}
+/* END_CASE */
+
 /* BEGIN_CASE */
 void key_lifetime( int lifetime_arg )
 {
@@ -2372,6 +2444,45 @@ exit:
 }
 /* END_CASE */
 
+/* BEGIN_CASE */
+void derive_setup( int key_type_arg,
+                   data_t *key_data,
+                   int alg_arg,
+                   data_t *salt,
+                   data_t *label,
+                   int requested_capacity_arg,
+                   int expected_status_arg )
+{
+    psa_key_slot_t slot = 1;
+    size_t key_type = key_type_arg;
+    psa_algorithm_t alg = alg_arg;
+    size_t requested_capacity = requested_capacity_arg;
+    psa_status_t expected_status = expected_status_arg;
+    psa_crypto_generator_t generator = PSA_CRYPTO_GENERATOR_INIT;
+    psa_key_policy_t policy;
+
+    TEST_ASSERT( psa_crypto_init( ) == PSA_SUCCESS );
+
+    psa_key_policy_init( &policy );
+    psa_key_policy_set_usage( &policy, PSA_KEY_USAGE_DERIVE, alg );
+    TEST_ASSERT( psa_set_key_policy( slot, &policy ) == PSA_SUCCESS );
+
+    TEST_ASSERT( psa_import_key( slot, key_type,
+                                 key_data->x,
+                                 key_data->len ) == PSA_SUCCESS );
+
+    TEST_ASSERT( psa_key_derivation( &generator, slot, alg,
+                                     salt->x, salt->len,
+                                     label->x, label->len,
+                                     requested_capacity ) == expected_status );
+
+exit:
+    psa_generator_abort( &generator );
+    psa_destroy_key( slot );
+    mbedtls_psa_crypto_free( );
+}
+/* END_CASE */
+
 /* BEGIN_CASE */
 void generate_random( int bytes_arg )
 {