lib/crypto: sha1: Add HMAC support

Add HMAC support to the SHA-1 library, again following what was done for
SHA-2.  Besides providing the basis for a more streamlined "hmac(sha1)"
shash, this will also be useful for multiple in-kernel users such as
net/sctp/auth.c, net/ipv6/seg6_hmac.c, and
security/keys/trusted-keys/trusted_tpm1.c.  Those are currently using
crypto_shash, but using the library functions would be much simpler.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250712232329.818226-5-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

1 files changed, 118 insertions, 0 deletions

diff --git a/include/crypto/sha1.h b/include/crypto/sha1.h
index 387f6123a05e..162a529ec841 100644
--- a/include/crypto/sha1.h
+++ b/include/crypto/sha1.h
@@ -96,4 +96,122 @@ void sha1_final(struct sha1_ctx *ctx, u8 out[SHA1_DIGEST_SIZE]);
  */
 void sha1(const u8 *data, size_t len, u8 out[SHA1_DIGEST_SIZE]);
 
+/**
+ * struct hmac_sha1_key - Prepared key for HMAC-SHA1
+ * @istate: private
+ * @ostate: private
+ */
+struct hmac_sha1_key {
+	struct sha1_block_state istate;
+	struct sha1_block_state ostate;
+};
+
+/**
+ * struct hmac_sha1_ctx - Context for computing HMAC-SHA1 of a message
+ * @sha_ctx: private
+ * @ostate: private
+ */
+struct hmac_sha1_ctx {
+	struct sha1_ctx sha_ctx;
+	struct sha1_block_state ostate;
+};
+
+/**
+ * hmac_sha1_preparekey() - Prepare a key for HMAC-SHA1
+ * @key: (output) the key structure to initialize
+ * @raw_key: the raw HMAC-SHA1 key
+ * @raw_key_len: the key length in bytes.  All key lengths are supported.
+ *
+ * Note: the caller is responsible for zeroizing both the struct hmac_sha1_key
+ * and the raw key once they are no longer needed.
+ *
+ * Context: Any context.
+ */
+void hmac_sha1_preparekey(struct hmac_sha1_key *key,
+			  const u8 *raw_key, size_t raw_key_len);
+
+/**
+ * hmac_sha1_init() - Initialize an HMAC-SHA1 context for a new message
+ * @ctx: (output) the HMAC context to initialize
+ * @key: the prepared HMAC key
+ *
+ * If you don't need incremental computation, consider hmac_sha1() instead.
+ *
+ * Context: Any context.
+ */
+void hmac_sha1_init(struct hmac_sha1_ctx *ctx, const struct hmac_sha1_key *key);
+
+/**
+ * hmac_sha1_init_usingrawkey() - Initialize an HMAC-SHA1 context for a new
+ *				  message, using a raw key
+ * @ctx: (output) the HMAC context to initialize
+ * @raw_key: the raw HMAC-SHA1 key
+ * @raw_key_len: the key length in bytes.  All key lengths are supported.
+ *
+ * If you don't need incremental computation, consider hmac_sha1_usingrawkey()
+ * instead.
+ *
+ * Context: Any context.
+ */
+void hmac_sha1_init_usingrawkey(struct hmac_sha1_ctx *ctx,
+				const u8 *raw_key, size_t raw_key_len);
+
+/**
+ * hmac_sha1_update() - Update an HMAC-SHA1 context with message data
+ * @ctx: the HMAC context to update; must have been initialized
+ * @data: the message data
+ * @data_len: the data length in bytes
+ *
+ * This can be called any number of times.
+ *
+ * Context: Any context.
+ */
+static inline void hmac_sha1_update(struct hmac_sha1_ctx *ctx,
+				    const u8 *data, size_t data_len)
+{
+	sha1_update(&ctx->sha_ctx, data, data_len);
+}
+
+/**
+ * hmac_sha1_final() - Finish computing an HMAC-SHA1 value
+ * @ctx: the HMAC context to finalize; must have been initialized
+ * @out: (output) the resulting HMAC-SHA1 value
+ *
+ * After finishing, this zeroizes @ctx.  So the caller does not need to do it.
+ *
+ * Context: Any context.
+ */
+void hmac_sha1_final(struct hmac_sha1_ctx *ctx, u8 out[SHA1_DIGEST_SIZE]);
+
+/**
+ * hmac_sha1() - Compute HMAC-SHA1 in one shot, using a prepared key
+ * @key: the prepared HMAC key
+ * @data: the message data
+ * @data_len: the data length in bytes
+ * @out: (output) the resulting HMAC-SHA1 value
+ *
+ * If you're using the key only once, consider using hmac_sha1_usingrawkey().
+ *
+ * Context: Any context.
+ */
+void hmac_sha1(const struct hmac_sha1_key *key,
+	       const u8 *data, size_t data_len, u8 out[SHA1_DIGEST_SIZE]);
+
+/**
+ * hmac_sha1_usingrawkey() - Compute HMAC-SHA1 in one shot, using a raw key
+ * @raw_key: the raw HMAC-SHA1 key
+ * @raw_key_len: the key length in bytes.  All key lengths are supported.
+ * @data: the message data
+ * @data_len: the data length in bytes
+ * @out: (output) the resulting HMAC-SHA1 value
+ *
+ * If you're using the key multiple times, prefer to use hmac_sha1_preparekey()
+ * followed by multiple calls to hmac_sha1() instead.
+ *
+ * Context: Any context.
+ */
+void hmac_sha1_usingrawkey(const u8 *raw_key, size_t raw_key_len,
+			   const u8 *data, size_t data_len,
+			   u8 out[SHA1_DIGEST_SIZE]);
+
 #endif /* _CRYPTO_SHA1_H */