Subject: [PATCH v2 10/14] crypto: sha256 - Use same state format as legacy drivers

From: Eric Biggers <[email-masked]>
Date: Mon, 30 Jun 2025 09:06:41 -0700

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.

Signed-off-by: Eric Biggers <[email-masked]>
---
 crypto/sha256.c | 95 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)

diff --git a/crypto/sha256.c b/crypto/sha256.c
index d81166cbba953..052806559f06c 100644
--- a/crypto/sha256.c
+++ b/crypto/sha256.c
@@ -11,10 +11,47 @@
 #include <crypto/internal/hash.h>
 #include <crypto/sha2.h>
 #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] = {
 	0xd1, 0x4a, 0x02, 0x8c, 0x2a, 0x3a, 0x2b, 0xc9, 0x47,
 	0x61, 0x02, 0xbb, 0x28, 0x82, 0x34, 0xc4, 0x15, 0xa2,
@@ -49,10 +86,20 @@ static int crypto_sha224_digest(struct shash_desc *desc,
 {
 	sha224(data, len, out);
 	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] = {
 	0xe3, 0xb0, 0xc4, 0x42, 0x98, 0xfc, 0x1c, 0x14,
 	0x9a, 0xfb, 0xf4, 0xc8, 0x99, 0x6f, 0xb9, 0x24,
@@ -87,10 +134,20 @@ static int crypto_sha256_digest(struct shash_desc *desc,
 {
 	sha256(data, len, out);
 	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))
 #define HMAC_SHA224_CTX(desc) ((struct hmac_sha224_ctx *)shash_desc_ctx(desc))
 
@@ -126,10 +183,23 @@ static int crypto_hmac_sha224_digest(struct shash_desc *desc,
 {
 	hmac_sha224(HMAC_SHA224_KEY(desc->tfm), data, len, out);
 	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))
 #define HMAC_SHA256_CTX(desc) ((struct hmac_sha256_ctx *)shash_desc_ctx(desc))
 
@@ -165,10 +235,23 @@ static int crypto_hmac_sha256_digest(struct shash_desc *desc,
 {
 	hmac_sha256(HMAC_SHA256_KEY(desc->tfm), data, len, out);
 	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[] = {
 	{
 		.base.cra_name		= "sha224",
@@ -179,11 +262,14 @@ static struct shash_alg algs[] = {
 		.digestsize		= SHA224_DIGEST_SIZE,
 		.init			= crypto_sha224_init,
 		.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",
 		.base.cra_driver_name	= "sha256-lib",
 		.base.cra_priority	= 300,
@@ -192,11 +278,14 @@ static struct shash_alg algs[] = {
 		.digestsize		= SHA256_DIGEST_SIZE,
 		.init			= crypto_sha256_init,
 		.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)",
 		.base.cra_driver_name	= "hmac-sha224-lib",
 		.base.cra_priority	= 300,
@@ -207,11 +296,14 @@ static struct shash_alg algs[] = {
 		.setkey			= crypto_hmac_sha224_setkey,
 		.init			= crypto_hmac_sha224_init,
 		.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)",
 		.base.cra_driver_name	= "hmac-sha256-lib",
 		.base.cra_priority	= 300,
@@ -222,11 +314,14 @@ static struct shash_alg algs[] = {
 		.setkey			= crypto_hmac_sha256_setkey,
 		.init			= crypto_hmac_sha256_init,
 		.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,
 	},
 };
 
 static int __init crypto_sha256_mod_init(void)
 {
-- 
2.50.0