[PATCH 03/18] crypto: sha512 - Use the correct legacy export format

Eric Biggers
2025-06-25T07:10:28Z

It appears the legacy export format is intended to have the value of the
bytecount field be block-aligned, so update __crypto_sha512_export() and
__crypto_sha512_import() to match.

Fixes: e62c2fe56418 ("crypto: sha512 - Use same state format as legacy drivers")
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
---
crypto/sha512.c | 22 +++++++++++++++++-----
1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/crypto/sha512.c b/crypto/sha512.c
index 0eed801346018..5bda259dd22fe 100644
--- a/crypto/sha512.c
+++ b/crypto/sha512.c
@@ -13,30 +13,42 @@
#include <linux/module.h>

/*
* Export and import functions. crypto_shash wants a particular format that
* matches that used by some legacy drivers. It currently is the same as the
- * library SHA context but with the partial block length as a u8 appended to it.
+ * library SHA context, except the value in bytecount_lo must be block-aligned
+ * and the remainder must be stored in an extra u8 appended to the struct.
*/

#define SHA512_SHASH_STATE_SIZE 209
static_assert(offsetof(struct __sha512_ctx, state) == 0);
static_assert(offsetof(struct __sha512_ctx, bytecount_lo) == 64);
static_assert(offsetof(struct __sha512_ctx, bytecount_hi) == 72);
static_assert(offsetof(struct __sha512_ctx, buf) == 80);
static_assert(sizeof(struct __sha512_ctx) + 1 == SHA512_SHASH_STATE_SIZE);

-static int __crypto_sha512_export(const struct __sha512_ctx *ctx, void *out)
+static int __crypto_sha512_export(const struct __sha512_ctx *ctx0, void *out)
{
- memcpy(out, ctx, sizeof(*ctx));
- *((u8 *)out + sizeof(*ctx)) = ctx->bytecount_lo % SHA512_BLOCK_SIZE;
+ struct __sha512_ctx ctx = *ctx0;
+ unsigned int partial;
+ u8 *p = out;
+
+ partial = ctx.bytecount_lo % SHA512_BLOCK_SIZE;
+ ctx.bytecount_lo -= partial;
+ memcpy(p, &ctx, sizeof(ctx));
+ p += sizeof(ctx);
+ *p = partial;
return 0;
}

static int __crypto_sha512_import(struct __sha512_ctx *ctx, const void *in)
{
- memcpy(ctx, in, sizeof(*ctx));
+ const u8 *p = in;
+
+ memcpy(ctx, p, sizeof(*ctx));
+ p += sizeof(*ctx);
+ ctx->bytecount_lo += *p;
return 0;
}

/* SHA-384 */

--
2.50.0