crypto: sha256 - Use same state format as legacy drivers

Make the export and import functions for the sha224, sha256,
hmac(sha224), and hmac(sha256) shash algorithms use the same format as
the padlock-sha and nx-sha256 drivers, as required by Herbert.

Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250630160645.3198-11-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

crypto/sha256.c

@@ -13,6 +13,43 @@
 #include <linux/kernel.h>
 #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, except the value in bytecount must be block-aligned and
+ * the remainder must be stored in an extra u8 appended to the struct.
+ */
+
+#define SHA256_SHASH_STATE_SIZE 105
+static_assert(offsetof(struct __sha256_ctx, state) == 0);
+static_assert(offsetof(struct __sha256_ctx, bytecount) == 32);
+static_assert(offsetof(struct __sha256_ctx, buf) == 40);
+static_assert(sizeof(struct __sha256_ctx) + 1 == SHA256_SHASH_STATE_SIZE);
+
+static int __crypto_sha256_export(const struct __sha256_ctx *ctx0, void *out)
+{
+	struct __sha256_ctx ctx = *ctx0;
+	unsigned int partial;
+	u8 *p = out;
+
+	partial = ctx.bytecount % SHA256_BLOCK_SIZE;
+	ctx.bytecount -= partial;
+	memcpy(p, &ctx, sizeof(ctx));
+	p += sizeof(ctx);
+	*p = partial;
+	return 0;
+}
+
+static int __crypto_sha256_import(struct __sha256_ctx *ctx, const void *in)
+{
+	const u8 *p = in;
+
+	memcpy(ctx, p, sizeof(*ctx));
+	p += sizeof(*ctx);
+	ctx->bytecount += *p;
+	return 0;
+}
+
 /* SHA-224 */
 
 const u8 sha224_zero_message_hash[SHA224_DIGEST_SIZE] = {
@@ -51,6 +88,16 @@ static int crypto_sha224_digest(struct shash_desc *desc,
 	return 0;
 }
 
+static int crypto_sha224_export(struct shash_desc *desc, void *out)
+{
+	return __crypto_sha256_export(&SHA224_CTX(desc)->ctx, out);
+}
+
+static int crypto_sha224_import(struct shash_desc *desc, const void *in)
+{
+	return __crypto_sha256_import(&SHA224_CTX(desc)->ctx, in);
+}
+
 /* SHA-256 */
 
 const u8 sha256_zero_message_hash[SHA256_DIGEST_SIZE] = {
@@ -89,6 +136,16 @@ static int crypto_sha256_digest(struct shash_desc *desc,
 	return 0;
 }
 
+static int crypto_sha256_export(struct shash_desc *desc, void *out)
+{
+	return __crypto_sha256_export(&SHA256_CTX(desc)->ctx, out);
+}
+
+static int crypto_sha256_import(struct shash_desc *desc, const void *in)
+{
+	return __crypto_sha256_import(&SHA256_CTX(desc)->ctx, in);
+}
+
 /* HMAC-SHA224 */
 
 #define HMAC_SHA224_KEY(tfm) ((struct hmac_sha224_key *)crypto_shash_ctx(tfm))
@@ -128,6 +185,19 @@ static int crypto_hmac_sha224_digest(struct shash_desc *desc,
 	return 0;
 }
 
+static int crypto_hmac_sha224_export(struct shash_desc *desc, void *out)
+{
+	return __crypto_sha256_export(&HMAC_SHA224_CTX(desc)->ctx.sha_ctx, out);
+}
+
+static int crypto_hmac_sha224_import(struct shash_desc *desc, const void *in)
+{
+	struct hmac_sha224_ctx *ctx = HMAC_SHA224_CTX(desc);
+
+	ctx->ctx.ostate = HMAC_SHA224_KEY(desc->tfm)->key.ostate;
+	return __crypto_sha256_import(&ctx->ctx.sha_ctx, in);
+}
+
 /* HMAC-SHA256 */
 
 #define HMAC_SHA256_KEY(tfm) ((struct hmac_sha256_key *)crypto_shash_ctx(tfm))
@@ -167,6 +237,19 @@ static int crypto_hmac_sha256_digest(struct shash_desc *desc,
 	return 0;
 }
 
+static int crypto_hmac_sha256_export(struct shash_desc *desc, void *out)
+{
+	return __crypto_sha256_export(&HMAC_SHA256_CTX(desc)->ctx.sha_ctx, out);
+}
+
+static int crypto_hmac_sha256_import(struct shash_desc *desc, const void *in)
+{
+	struct hmac_sha256_ctx *ctx = HMAC_SHA256_CTX(desc);
+
+	ctx->ctx.ostate = HMAC_SHA256_KEY(desc->tfm)->key.ostate;
+	return __crypto_sha256_import(&ctx->ctx.sha_ctx, in);
+}
+
 /* Algorithm definitions */
 
 static struct shash_alg algs[] = {
@@ -181,7 +264,10 @@ static struct shash_alg algs[] = {
 		.update			= crypto_sha224_update,
 		.final			= crypto_sha224_final,
 		.digest			= crypto_sha224_digest,
+		.export			= crypto_sha224_export,
+		.import			= crypto_sha224_import,
 		.descsize		= sizeof(struct sha224_ctx),
+		.statesize		= SHA256_SHASH_STATE_SIZE,
 	},
 	{
 		.base.cra_name		= "sha256",
@@ -194,7 +280,10 @@ static struct shash_alg algs[] = {
 		.update			= crypto_sha256_update,
 		.final			= crypto_sha256_final,
 		.digest			= crypto_sha256_digest,
+		.export			= crypto_sha256_export,
+		.import			= crypto_sha256_import,
 		.descsize		= sizeof(struct sha256_ctx),
+		.statesize		= SHA256_SHASH_STATE_SIZE,
 	},
 	{
 		.base.cra_name		= "hmac(sha224)",
@@ -209,7 +298,10 @@ static struct shash_alg algs[] = {
 		.update			= crypto_hmac_sha224_update,
 		.final			= crypto_hmac_sha224_final,
 		.digest			= crypto_hmac_sha224_digest,
+		.export			= crypto_hmac_sha224_export,
+		.import			= crypto_hmac_sha224_import,
 		.descsize		= sizeof(struct hmac_sha224_ctx),
+		.statesize		= SHA256_SHASH_STATE_SIZE,
 	},
 	{
 		.base.cra_name		= "hmac(sha256)",
@@ -224,7 +316,10 @@ static struct shash_alg algs[] = {
 		.update			= crypto_hmac_sha256_update,
 		.final			= crypto_hmac_sha256_final,
 		.digest			= crypto_hmac_sha256_digest,
+		.export			= crypto_hmac_sha256_export,
+		.import			= crypto_hmac_sha256_import,
 		.descsize		= sizeof(struct hmac_sha256_ctx),
+		.statesize		= SHA256_SHASH_STATE_SIZE,
 	},
 };