crypto: sig - Introduce sig_alg backend

Commit 6cb8815f41a9 ("crypto: sig - Add interface for sign/verify")
began a transition of asymmetric sign/verify operations from
crypto_akcipher to a new crypto_sig frontend.

Internally, the crypto_sig frontend still uses akcipher_alg as backend,
however:

   "The link between sig and akcipher is meant to be temporary.  The
    plan is to create a new low-level API for sig and then migrate
    the signature code over to that from akcipher."
    https://lore.kernel.org/r/ZrG6w9wsb-iiLZIF@gondor.apana.org.au/

   "having a separate alg for sig is definitely where we want to
    be since there is very little that the two types actually share."
    https://lore.kernel.org/r/ZrHlpz4qnre0zWJO@gondor.apana.org.au/

Take the next step of that migration and augment the crypto_sig frontend
with a sig_alg backend to which all algorithms can be moved.

During the migration, there will briefly be signature algorithms that
are still based on crypto_akcipher, whilst others are already based on
crypto_sig.  Allow for that by building a fork into crypto_sig_*() API
calls (i.e. crypto_sig_maxsize() and friends) such that one of the two
backends is selected based on the transform's cra_type.

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 61 insertions, 0 deletions

diff --git a/include/crypto/sig.h b/include/crypto/sig.h
index d25186bb2be3..f0f52a7c5ae7 100644
--- a/include/crypto/sig.h
+++ b/include/crypto/sig.h
@@ -20,6 +20,52 @@ struct crypto_sig {
 };
 
 /**
+ * struct sig_alg - generic public key signature algorithm
+ *
+ * @sign:	Function performs a sign operation as defined by public key
+ *		algorithm. Optional.
+ * @verify:	Function performs a complete verify operation as defined by
+ *		public key algorithm, returning verification status. Optional.
+ * @set_pub_key: Function invokes the algorithm specific set public key
+ *		function, which knows how to decode and interpret
+ *		the BER encoded public key and parameters. Mandatory.
+ * @set_priv_key: Function invokes the algorithm specific set private key
+ *		function, which knows how to decode and interpret
+ *		the BER encoded private key and parameters. Optional.
+ * @max_size:	Function returns key size. Mandatory.
+ * @init:	Initialize the cryptographic transformation object.
+ *		This function is used to initialize the cryptographic
+ *		transformation object. This function is called only once at
+ *		the instantiation time, right after the transformation context
+ *		was allocated. In case the cryptographic hardware has some
+ *		special requirements which need to be handled by software, this
+ *		function shall check for the precise requirement of the
+ *		transformation and put any software fallbacks in place.
+ * @exit:	Deinitialize the cryptographic transformation object. This is a
+ *		counterpart to @init, used to remove various changes set in
+ *		@init.
+ *
+ * @base:	Common crypto API algorithm data structure
+ */
+struct sig_alg {
+	int (*sign)(struct crypto_sig *tfm,
+		    const void *src, unsigned int slen,
+		    void *dst, unsigned int dlen);
+	int (*verify)(struct crypto_sig *tfm,
+		      const void *src, unsigned int slen,
+		      const void *digest, unsigned int dlen);
+	int (*set_pub_key)(struct crypto_sig *tfm,
+			   const void *key, unsigned int keylen);
+	int (*set_priv_key)(struct crypto_sig *tfm,
+			    const void *key, unsigned int keylen);
+	unsigned int (*max_size)(struct crypto_sig *tfm);
+	int (*init)(struct crypto_sig *tfm);
+	void (*exit)(struct crypto_sig *tfm);
+
+	struct crypto_alg base;
+};
+
+/**
  * DOC: Generic Public Key Signature API
  *
  * The Public Key Signature API is used with the algorithms of type
@@ -47,6 +93,21 @@ static inline struct crypto_tfm *crypto_sig_tfm(struct crypto_sig *tfm)
 	return &tfm->base;
 }
 
+static inline struct crypto_sig *__crypto_sig_tfm(struct crypto_tfm *tfm)
+{
+	return container_of(tfm, struct crypto_sig, base);
+}
+
+static inline struct sig_alg *__crypto_sig_alg(struct crypto_alg *alg)
+{
+	return container_of(alg, struct sig_alg, base);
+}
+
+static inline struct sig_alg *crypto_sig_alg(struct crypto_sig *tfm)
+{
+	return __crypto_sig_alg(crypto_sig_tfm(tfm)->__crt_alg);
+}
+
 /**
  * crypto_free_sig() - free signature tfm handle
  *