[PATCH] lib/crypto: sha1: use put_unaligned_be64() for length encoding

[Mohamad Raizudeen]

The SHA1 final code in __sha1_final() and hmac_sha1_final() writes the
64-bit message bit length of the SHA1 padding using direct access
pointer casts:

`*(__be64 *)&ctx->buf[SHA1_BLOCK_SIZE - 8] = cpu_to_be64(bitcount);`
`*(__be32 *)&ctx->sha_ctx.buf[SHA1_BLOCK_SIZE - 4] =
	 cpu_to_be32(8 * (SHA1_BLOCK_SIZE + SHA1_DIGEST_SIZE));`

The rest of this file already uses the unaligned access helpers like
get_unaligned_be32() for reading input and put_unaligned_be32() for writing
the digest, for all structured buffer accesses. Replace both casts with
put_unaligned_be64() for consistency.

In hmac_sha1_final(), this also writes the full 64-bit length field
explicitly rather than writing only 32 bits and relying on a preceding
memset() to zero the upper 32 bits. The resulting bytes are identical,
nothing changes functionally.

Signed-off-by: Mohamad Raizudeen <raizudeen.kerneldev@xxxxxxxxx>
---
 lib/crypto/sha1.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/crypto/sha1.c b/lib/crypto/sha1.c
index b687b89d97cb..17d97160d578 100644
--- a/lib/crypto/sha1.c
+++ b/lib/crypto/sha1.c
@@ -183,7 +183,7 @@ static void __sha1_final(struct sha1_ctx *ctx, u8 out[SHA1_DIGEST_SIZE])
 		partial = 0;
 	}
 	memset(&ctx->buf[partial], 0, SHA1_BLOCK_SIZE - 8 - partial);
-	*(__be64 *)&ctx->buf[SHA1_BLOCK_SIZE - 8] = cpu_to_be64(bitcount);
+	put_unaligned_be64(bitcount, &ctx->buf[SHA1_BLOCK_SIZE - 8]);
 	sha1_blocks(&ctx->state, ctx->buf, 1);
 
 	for (size_t i = 0; i < SHA1_DIGEST_SIZE; i += 4)
@@ -267,8 +267,8 @@ void hmac_sha1_final(struct hmac_sha1_ctx *ctx, u8 out[SHA1_DIGEST_SIZE])
 	memset(&ctx->sha_ctx.buf[SHA1_DIGEST_SIZE], 0,
 	       SHA1_BLOCK_SIZE - SHA1_DIGEST_SIZE);
 	ctx->sha_ctx.buf[SHA1_DIGEST_SIZE] = 0x80;
-	*(__be32 *)&ctx->sha_ctx.buf[SHA1_BLOCK_SIZE - 4] =
-		cpu_to_be32(8 * (SHA1_BLOCK_SIZE + SHA1_DIGEST_SIZE));
+	put_unaligned_be64((u64)8 * (SHA1_BLOCK_SIZE + SHA1_DIGEST_SIZE),
+			&ctx->sha_ctx.buf[SHA1_BLOCK_SIZE - 8]);
 
 	/* Compute the outer hash, which gives the HMAC value. */
 	sha1_blocks(&ctx->ostate, ctx->sha_ctx.buf, 1);
-- 
2.53.0