Resolve PR review comments

Address review comments:
1. add `mbedtls_cipher_init()` after freeing context, in test code
2. style comments
3. set `ctx->iv_size = 0` in case `IV == NULL && iv_len == 0`

Author: Ron Eldor

library/cipher.c

@@ -242,6 +242,9 @@ int mbedtls_cipher_set_iv( mbedtls_cipher_context_t *ctx,
     else if( NULL == iv && iv_len != 0  )
         return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
 
+    if( NULL == iv && iv_len == 0 )
+        ctx->iv_size = 0;
+
     /* avoid buffer overflow in ctx->iv */
     if( iv_len > MBEDTLS_MAX_IV_LENGTH )
         return( MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE );
@@ -269,7 +272,7 @@ int mbedtls_cipher_set_iv( mbedtls_cipher_context_t *ctx,
     }
 #endif
 
-    if ( actual_iv_size )
+    if ( actual_iv_size != 0 )
     {
         memcpy( ctx->iv, iv, actual_iv_size );
         ctx->iv_size = actual_iv_size;

tests/suites/test_suite_cipher.function

@@ -106,7 +106,7 @@ void cipher_special_behaviours( )
     mbedtls_cipher_init( &ctx );
     memset( input, 0, sizeof( input ) );
     memset( output, 0, sizeof( output ) );
-#if defined (MBEDTLS_CIPHER_MODE_CBC)
+#if defined(MBEDTLS_CIPHER_MODE_CBC)
     memset( iv, 0, sizeof( iv ) );
 
     /* Check and get info structures */
@@ -124,6 +124,7 @@ void cipher_special_behaviours( )
                  == MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
 
     mbedtls_cipher_free( &ctx );
+    mbedtls_cipher_init( &ctx );
 #endif /* MBEDTLS_CIPHER_MODE_CBC */
     cipher_info = mbedtls_cipher_info_from_type( MBEDTLS_CIPHER_AES_128_ECB );
     TEST_ASSERT( NULL != cipher_info );