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From 393d5c41284292f72f2dd2a3c8e246e972ac718c Mon Sep 17 00:00:00 2001
From: Sam James <sam@gentoo.org>
Date: Thu, 11 Apr 2024 21:39:36 +0100
Subject: [PATCH] sha2: fix aliasing violation
`&context->buffer` is `uint8_t*`, but we try to access it as `sha2_word64*`, which
is an aliasing violation (undefined behaviour).
Use memcpy instead to avoid being miscompiled by e.g. >= GCC 12. This is
just as fast with any modern compiler.
Bug: https://gcc.gnu.org/PR114698
Bug: https://github.com/NetBSD/pkgsrc/issues/122
Bug: https://github.com/archiecobbs/libnbcompat/issues/4
Bug: https://bugs.launchpad.net/ubuntu-power-systems/+bug/2033405
Signed-off-by: Sam James <sam@gentoo.org>
---
src/sha2.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/src/sha2.c b/src/sha2.c
index bea1708..3925b97 100644
--- a/src/sha2.c
+++ b/src/sha2.c
@@ -604,7 +604,7 @@ void SHA256_Final(SHA256_CTX* context, sha2_byte digest[]) {
*context->buffer = 0x80;
}
/* Set the bit count: */
- *(sha2_word64*)&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*)context->buffer);
@@ -921,8 +921,8 @@ void SHA512_Last(SHA512_CTX* context) {
*context->buffer = 0x80;
}
/* Store the length of input data (in bits): */
- *(sha2_word64*)&context->buffer[SHA512_SHORT_BLOCK_LENGTH] = context->bitcount[1];
- *(sha2_word64*)&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*)context->buffer);
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