psa: Disallow repeated setup

Calling psa_*_setup() twice on a MAC, cipher, or hash context should
result in a PSA_ERROR_BAD_STATE error because the operation has already
been set up.

Fixes #10

Author: Patater

library/psa_crypto.c

@@ -1379,7 +1379,12 @@ psa_status_t psa_hash_setup( psa_hash_operation_t *operation,
                              psa_algorithm_t alg )
 {
     int ret;
-    operation->alg = 0;
+
+    /* A context must be freshly initialized before it can be set up. */
+    if (operation->alg != 0) {
+        return( PSA_ERROR_BAD_STATE );
+    }
+
     switch( alg )
     {
 #if defined(MBEDTLS_MD2_C)
@@ -2000,6 +2005,11 @@ static psa_status_t psa_mac_setup( psa_mac_operation_t *operation,
     unsigned char truncated = PSA_MAC_TRUNCATED_LENGTH( alg );
     psa_algorithm_t full_length_alg = PSA_ALG_FULL_LENGTH_MAC( alg );
 
+    /* A context must be freshly initialized before it can be set up. */
+    if (operation->alg != 0) {
+        return( PSA_ERROR_BAD_STATE );
+    }
+
     status = psa_mac_init( operation, full_length_alg );
     if( status != PSA_SUCCESS )
         return( status );
@@ -2913,6 +2923,11 @@ static psa_status_t psa_cipher_setup( psa_cipher_operation_t *operation,
                               PSA_KEY_USAGE_ENCRYPT :
                               PSA_KEY_USAGE_DECRYPT );
 
+    /* A context must be freshly initialized before it can be set up. */
+    if (operation->alg != 0) {
+        return( PSA_ERROR_BAD_STATE );
+    }
+
     status = psa_cipher_init( operation, alg );
     if( status != PSA_SUCCESS )
         return( status );

tests/suites/test_suite_psa_crypto.function

@@ -2012,6 +2012,12 @@ void hash_bad_order( )
 
     PSA_ASSERT( psa_crypto_init( ) );
 
+    /* Call setup twice in a row. */
+    memset( &operation, 0, sizeof( operation ) );
+    PSA_ASSERT( psa_hash_setup( &operation, alg ) );
+    TEST_EQUAL( psa_hash_setup( &operation, alg ),
+                PSA_ERROR_BAD_STATE );
+
     /* Call update without calling setup beforehand. */
     memset( &operation, 0, sizeof( operation ) );
     TEST_EQUAL( psa_hash_update( &operation, input, sizeof( input ) ),
@@ -2333,6 +2339,14 @@ void mac_bad_order( )
                                        verify_mac, sizeof( verify_mac ) ),
                 PSA_ERROR_BAD_STATE );
 
+    /* Call setup twice in a row. */
+    memset( &operation, 0, sizeof( operation ) );
+    PSA_ASSERT( psa_mac_sign_setup( &operation,
+                                    handle, alg ) );
+    TEST_EQUAL( psa_mac_sign_setup( &operation,
+                                    handle, alg ),
+                PSA_ERROR_BAD_STATE );
+
     /* Call update after sign finish. */
     memset( &operation, 0, sizeof( operation ) );
     PSA_ASSERT( psa_mac_sign_setup( &operation,
@@ -2606,6 +2620,17 @@ void cipher_bad_order( )
                                 key, sizeof(key) ) );
 
 
+    /* Call encrypt setup twice in a row. */
+    PSA_ASSERT( psa_cipher_encrypt_setup( &operation, handle, alg ) );
+    TEST_EQUAL( psa_cipher_encrypt_setup( &operation, handle, alg ),
+                PSA_ERROR_BAD_STATE );
+
+    /* Call decrypt setup twice in a row. */
+    memset( &operation, 0, sizeof( operation ) );
+    PSA_ASSERT( psa_cipher_decrypt_setup( &operation, handle, alg ) );
+    TEST_EQUAL( psa_cipher_decrypt_setup( &operation, handle, alg ),
+                PSA_ERROR_BAD_STATE );
+
     /* Generate an IV without calling setup beforehand. */
     memset( &operation, 0, sizeof( operation ) );
     TEST_EQUAL( psa_cipher_generate_iv( &operation,