Fix Blake2b for BigEndian (#1235)

* Fix Blake2b for BigEndian

* Use BLAKE2B256_DIGEST_LENGTH constant

* Use CRYPTO_store_u64_le

crypto/blake2/blake2.c

@@ -59,6 +59,16 @@ static uint64_t blake2b_load(const uint8_t block[BLAKE2B_CBLOCK], size_t i) {
   return CRYPTO_load_u64_le(block + 8 * i);
 }
 
+static void copy_digest_words_to_dest(uint8_t* dest, uint64_t* src, size_t word_count) {
+#ifdef OPENSSL_BIG_ENDIAN
+  for(size_t i = 0; i < word_count; i++) {
+    CRYPTO_store_u64_le(&dest[i * sizeof(uint64_t)], src[i]);
+  }
+#else
+  OPENSSL_memcpy(dest, src, word_count * sizeof(uint64_t));
+#endif
+}
+
 static void blake2b_transform(BLAKE2B_CTX *b2b,
                               const uint8_t block[BLAKE2B_CBLOCK],
                               size_t num_bytes, int is_final_block) {
@@ -158,7 +168,7 @@ void BLAKE2B256_Final(uint8_t out[BLAKE2B256_DIGEST_LENGTH], BLAKE2B_CTX *b2b) {
   blake2b_transform(b2b, b2b->block, b2b->block_used,
                     /*is_final_block=*/1);
   OPENSSL_STATIC_ASSERT(BLAKE2B256_DIGEST_LENGTH <= sizeof(b2b->h), _)
-  memcpy(out, b2b->h, BLAKE2B256_DIGEST_LENGTH);
+  copy_digest_words_to_dest(out, b2b->h, BLAKE2B256_DIGEST_LENGTH / 8);
 }
 
 void BLAKE2B256(const uint8_t *data, size_t len,