Fix SHA256 bug due to strict aliasing violations with newer GCC optim…

…izations (#4).
archiecobbs · Jun 7, 2023 · 864c1cf · 864c1cf
1 parent 16ceccd
commit 864c1cf
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Showing 2 changed files with 8 additions and 3 deletions.
diff --git a/CHANGES b/CHANGES
@@ -1,3 +1,8 @@
+Version Next
+
+    - Fixed SHA256 bug due to strict aliasing violations with newer GCC optimizations (#4).
+    - Add hash test vectors (contributed by Aleksa Sarai)
+
 Version 1.0.1 released August 29, 2020
 
     - Avoid defining PACKAGE, etc. in installed header files

diff --git a/sha2.c b/sha2.c
@@ -567,7 +567,7 @@ void SHA256_Final(sha2_byte digest[SHA256_DIGEST_LENGTH], SHA256_CTX* context) {
 			*context->buffer = 0x80;
 		}
 		/* Set the bit count: */
-		*(sha2_word64*)(void *)&context->buffer[SHA256_SHORT_BLOCK_LENGTH] = context->bitcount;
+		memcpy(&context->buffer[SHA256_SHORT_BLOCK_LENGTH], &context->bitcount, sizeof(context->bitcount));
 
 		/* Final transform: */
 		SHA256_Transform(context, (sha2_word32*)(void *)context->buffer);
@@ -870,8 +870,8 @@ static void SHA512_Last(SHA512_CTX* context) {
 		*context->buffer = 0x80;
 	}
 	/* Store the length of input data (in bits): */
-	*(sha2_word64*)(void *)&context->buffer[SHA512_SHORT_BLOCK_LENGTH] = context->bitcount[1];
-	*(sha2_word64*)(void *)&context->buffer[SHA512_SHORT_BLOCK_LENGTH+8] = context->bitcount[0];
+	memcpy(&context->buffer[SHA512_SHORT_BLOCK_LENGTH], &context->bitcount[1], sizeof(context->bitcount[1]));
+	memcpy(&context->buffer[SHA512_SHORT_BLOCK_LENGTH+8], &context->bitcount[0], sizeof(context->bitcount[0]));
 
 	/* Final transform: */
 	SHA512_Transform(context, (sha2_word64*)(void *)context->buffer);