crypto: rsa-pkcs1pad - Deduplicate set_{pub,priv}_key callbacks

pkcs1pad_set_pub_key() and pkcs1pad_set_priv_key() are almost identical.

The upcoming migration of sign/verify operations from rsa-pkcs1pad.c
into a separate crypto_template will require another copy of the exact
same functions. When RSASSA-PSS and RSAES-OAEP are introduced, each
will need yet another copy.

Deduplicate the functions into a single one which lives in a common
header file for reuse by RSASSA-PKCS1-v1_5, RSASSA-PSS and RSAES-OAEP.

Signed-off-by: Lukas Wunner <[e-mail]>
Reviewed-by: Stefan Berger <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>

crypto/rsa-pkcs1pad.c

···
 		unsigned int keylen)
 {
 	struct pkcs1pad_ctx *ctx = akcipher_tfm_ctx(tfm);
-	int err;
 
-	ctx->key_size = 0;
-
-	err = crypto_akcipher_set_pub_key(ctx->child, key, keylen);
-	if (err)
-		return err;
-
-	/* Find out new modulus size from rsa implementation */
-	err = crypto_akcipher_maxsize(ctx->child);
-	if (err > PAGE_SIZE)
-		return -ENOTSUPP;
-
-	ctx->key_size = err;
-	return 0;
+	return rsa_set_key(ctx->child, &ctx->key_size, RSA_PUB, key, keylen);
 }
 
 static int pkcs1pad_set_priv_key(struct crypto_akcipher *tfm, const void *key,
 		unsigned int keylen)
 {
 	struct pkcs1pad_ctx *ctx = akcipher_tfm_ctx(tfm);
-	int err;
 
-	ctx->key_size = 0;
-
-	err = crypto_akcipher_set_priv_key(ctx->child, key, keylen);
-	if (err)
-		return err;
-
-	/* Find out new modulus size from rsa implementation */
-	err = crypto_akcipher_maxsize(ctx->child);
-	if (err > PAGE_SIZE)
-		return -ENOTSUPP;
-
-	ctx->key_size = err;
-	return 0;
+	return rsa_set_key(ctx->child, &ctx->key_size, RSA_PRIV, key, keylen);
 }
 
 static unsigned int pkcs1pad_get_max_size(struct crypto_akcipher *tfm)

include/crypto/internal/rsa.h

···
 #ifndef _RSA_HELPER_
 #define _RSA_HELPER_
 #include <linux/types.h>
+#include <crypto/akcipher.h>
 
 /**
  * rsa_key - RSA key structure
···
 
 int rsa_parse_priv_key(struct rsa_key *rsa_key, const void *key,
 		       unsigned int key_len);
+
+#define RSA_PUB (true)
+#define RSA_PRIV (false)
+
+static inline int rsa_set_key(struct crypto_akcipher *child,
+			      unsigned int *key_size, bool is_pubkey,
+			      const void *key, unsigned int keylen)
+{
+	int err;
+
+	*key_size = 0;
+
+	if (is_pubkey)
+		err = crypto_akcipher_set_pub_key(child, key, keylen);
+	else
+		err = crypto_akcipher_set_priv_key(child, key, keylen);
+	if (err)
+		return err;
+
+	/* Find out new modulus size from rsa implementation */
+	err = crypto_akcipher_maxsize(child);
+	if (err > PAGE_SIZE)
+		return -ENOTSUPP;
+
+	*key_size = err;
+	return 0;
+}
 
 extern struct crypto_template rsa_pkcs1pad_tmpl;
 #endif