lib/crypto: sha2: Add hmac_sha*_init_usingrawkey()

While the HMAC library functions support both incremental and one-shot
computation and both prepared and raw keys, the combination of raw key
+ incremental was missing.  It turns out that several potential users of
the HMAC library functions (tpm2-sessions.c, smb2transport.c,
trusted_tpm1.c) want exactly that.

Therefore, add the missing functions hmac_sha*_init_usingrawkey().

Implement them in an optimized way that directly initializes the HMAC
context without a separate key preparation step.

Reimplement the one-shot raw key functions hmac_sha*_usingrawkey() on
top of the new functions, which makes them a bit more efficient.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250711215844.41715-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

1 files changed, 36 insertions, 17 deletions

diff --git a/lib/crypto/sha256.c b/lib/crypto/sha256.c
index 808438d4f427..8fa15165d23e 100644
--- a/lib/crypto/sha256.c
+++ b/lib/crypto/sha256.c
@@ -263,7 +263,8 @@ EXPORT_SYMBOL(sha256);
 
 /* pre-boot environment (as indicated by __DISABLE_EXPORTS) doesn't need HMAC */
 #ifndef __DISABLE_EXPORTS
-static void __hmac_sha256_preparekey(struct __hmac_sha256_key *key,
+static void __hmac_sha256_preparekey(struct sha256_block_state *istate,
+				     struct sha256_block_state *ostate,
 				     const u8 *raw_key, size_t raw_key_len,
 				     const struct sha256_block_state *iv)
 {
@@ -283,14 +284,14 @@ static void __hmac_sha256_preparekey(struct __hmac_sha256_key *key,
 
 	for (size_t i = 0; i < ARRAY_SIZE(derived_key.w); i++)
 		derived_key.w[i] ^= REPEAT_BYTE(HMAC_IPAD_VALUE);
-	key->istate = *iv;
-	sha256_blocks(&key->istate, derived_key.b, 1);
+	*istate = *iv;
+	sha256_blocks(istate, derived_key.b, 1);
 
 	for (size_t i = 0; i < ARRAY_SIZE(derived_key.w); i++)
 		derived_key.w[i] ^= REPEAT_BYTE(HMAC_OPAD_VALUE ^
 						HMAC_IPAD_VALUE);
-	key->ostate = *iv;
-	sha256_blocks(&key->ostate, derived_key.b, 1);
+	*ostate = *iv;
+	sha256_blocks(ostate, derived_key.b, 1);
 
 	memzero_explicit(&derived_key, sizeof(derived_key));
 }
@@ -298,14 +299,16 @@ static void __hmac_sha256_preparekey(struct __hmac_sha256_key *key,
 void hmac_sha224_preparekey(struct hmac_sha224_key *key,
 			    const u8 *raw_key, size_t raw_key_len)
 {
-	__hmac_sha256_preparekey(&key->key, raw_key, raw_key_len, &sha224_iv);
+	__hmac_sha256_preparekey(&key->key.istate, &key->key.ostate,
+				 raw_key, raw_key_len, &sha224_iv);
 }
 EXPORT_SYMBOL_GPL(hmac_sha224_preparekey);
 
 void hmac_sha256_preparekey(struct hmac_sha256_key *key,
 			    const u8 *raw_key, size_t raw_key_len)
 {
-	__hmac_sha256_preparekey(&key->key, raw_key, raw_key_len, &sha256_iv);
+	__hmac_sha256_preparekey(&key->key.istate, &key->key.ostate,
+				 raw_key, raw_key_len, &sha256_iv);
 }
 EXPORT_SYMBOL_GPL(hmac_sha256_preparekey);
 
@@ -317,6 +320,24 @@ void __hmac_sha256_init(struct __hmac_sha256_ctx *ctx,
 }
 EXPORT_SYMBOL_GPL(__hmac_sha256_init);
 
+void hmac_sha224_init_usingrawkey(struct hmac_sha224_ctx *ctx,
+				  const u8 *raw_key, size_t raw_key_len)
+{
+	__hmac_sha256_preparekey(&ctx->ctx.sha_ctx.state, &ctx->ctx.ostate,
+				 raw_key, raw_key_len, &sha224_iv);
+	ctx->ctx.sha_ctx.bytecount = SHA256_BLOCK_SIZE;
+}
+EXPORT_SYMBOL_GPL(hmac_sha224_init_usingrawkey);
+
+void hmac_sha256_init_usingrawkey(struct hmac_sha256_ctx *ctx,
+				  const u8 *raw_key, size_t raw_key_len)
+{
+	__hmac_sha256_preparekey(&ctx->ctx.sha_ctx.state, &ctx->ctx.ostate,
+				 raw_key, raw_key_len, &sha256_iv);
+	ctx->ctx.sha_ctx.bytecount = SHA256_BLOCK_SIZE;
+}
+EXPORT_SYMBOL_GPL(hmac_sha256_init_usingrawkey);
+
 static void __hmac_sha256_final(struct __hmac_sha256_ctx *ctx,
 				u8 *out, size_t digest_size)
 {
@@ -376,12 +397,11 @@ void hmac_sha224_usingrawkey(const u8 *raw_key, size_t raw_key_len,
 			     const u8 *data, size_t data_len,
 			     u8 out[SHA224_DIGEST_SIZE])
 {
-	struct hmac_sha224_key key;
-
-	hmac_sha224_preparekey(&key, raw_key, raw_key_len);
-	hmac_sha224(&key, data, data_len, out);
+	struct hmac_sha224_ctx ctx;
 
-	memzero_explicit(&key, sizeof(key));
+	hmac_sha224_init_usingrawkey(&ctx, raw_key, raw_key_len);
+	hmac_sha224_update(&ctx, data, data_len);
+	hmac_sha224_final(&ctx, out);
 }
 EXPORT_SYMBOL_GPL(hmac_sha224_usingrawkey);
 
@@ -389,12 +409,11 @@ void hmac_sha256_usingrawkey(const u8 *raw_key, size_t raw_key_len,
 			     const u8 *data, size_t data_len,
 			     u8 out[SHA256_DIGEST_SIZE])
 {
-	struct hmac_sha256_key key;
-
-	hmac_sha256_preparekey(&key, raw_key, raw_key_len);
-	hmac_sha256(&key, data, data_len, out);
+	struct hmac_sha256_ctx ctx;
 
-	memzero_explicit(&key, sizeof(key));
+	hmac_sha256_init_usingrawkey(&ctx, raw_key, raw_key_len);
+	hmac_sha256_update(&ctx, data, data_len);
+	hmac_sha256_final(&ctx, out);
 }
 EXPORT_SYMBOL_GPL(hmac_sha256_usingrawkey);
 #endif /* !__DISABLE_EXPORTS */