crypto: gcm - helper functions for assoclen/authsize check

Added inline helper functions to check authsize and assoclen for
gcm, rfc4106 and rfc4543.
These are used in the generic implementation of gcm, rfc4106 and
rfc4543.

Signed-off-by: Iuliana Prodan <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>

crypto/gcm.c

···
 static int crypto_gcm_setauthsize(struct crypto_aead *tfm,
 				  unsigned int authsize)
 {
-	switch (authsize) {
-	case 4:
-	case 8:
-	case 12:
-	case 13:
-	case 14:
-	case 15:
-	case 16:
-		break;
-	default:
-		return -EINVAL;
-	}
-
-	return 0;
+	return crypto_gcm_check_authsize(authsize);
 }
 
 static void crypto_gcm_init_common(struct aead_request *req)
···
 				      unsigned int authsize)
 {
 	struct crypto_rfc4106_ctx *ctx = crypto_aead_ctx(parent);
+	int err;
 
-	switch (authsize) {
-	case 8:
-	case 12:
-	case 16:
-		break;
-	default:
-		return -EINVAL;
-	}
+	err = crypto_rfc4106_check_authsize(authsize);
+	if (err)
+		return err;
 
 	return crypto_aead_setauthsize(ctx->child, authsize);
 }
···
 
 static int crypto_rfc4106_encrypt(struct aead_request *req)
 {
-	if (req->assoclen != 16 && req->assoclen != 20)
-		return -EINVAL;
+	int err;
+
+	err = crypto_ipsec_check_assoclen(req->assoclen);
+	if (err)
+		return err;
 
 	req = crypto_rfc4106_crypt(req);
 
···
 
 static int crypto_rfc4106_decrypt(struct aead_request *req)
 {
-	if (req->assoclen != 16 && req->assoclen != 20)
-		return -EINVAL;
+	int err;
+
+	err = crypto_ipsec_check_assoclen(req->assoclen);
+	if (err)
+		return err;
 
 	req = crypto_rfc4106_crypt(req);
 

include/crypto/gcm.h

···
 #ifndef _CRYPTO_GCM_H
 #define _CRYPTO_GCM_H
 
+#include <linux/errno.h>
+
 #define GCM_AES_IV_SIZE 12
 #define GCM_RFC4106_IV_SIZE 8
 #define GCM_RFC4543_IV_SIZE 8
 
+/*
+ * validate authentication tag for GCM
+ */
+static inline int crypto_gcm_check_authsize(unsigned int authsize)
+{
+	switch (authsize) {
+	case 4:
+	case 8:
+	case 12:
+	case 13:
+	case 14:
+	case 15:
+	case 16:
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/*
+ * validate authentication tag for RFC4106
+ */
+static inline int crypto_rfc4106_check_authsize(unsigned int authsize)
+{
+	switch (authsize) {
+	case 8:
+	case 12:
+	case 16:
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/*
+ * validate assoclen for RFC4106/RFC4543
+ */
+static inline int crypto_ipsec_check_assoclen(unsigned int assoclen)
+{
+	switch (assoclen) {
+	case 16:
+	case 20:
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
 #endif