[PATCH v5 5/8] crypto: AF_ALG: add user space interface for RNG

[Stephan Mueller <smueller@chronox.de>]

Allow user space to seed / reset the RNG via a setsockopt.

This patch reuses alg_setkey to copy data into the kernel. The
alg_setkey is now used for two mechanisms: setkey and seeding.
The function is extended by the providing the function pointer
to the function handling the copied data.

As the alg_setkey is now usable for more than just setkey, it is renamed
to alg_setop.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
---
 crypto/af_alg.c             | 29 +++++++++++++++++++----------
 include/crypto/if_alg.h     |  1 +
 include/uapi/linux/if_alg.h |  1 +
 3 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/crypto/af_alg.c b/crypto/af_alg.c
index 547c369..d1eb1e9 100644
--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -169,26 +169,27 @@ static int alg_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
 	return 0;
 }
 
-static int alg_setkey(struct sock *sk, char __user *ukey,
-		      unsigned int keylen)
+static int alg_setop(struct sock *sk, char __user *udata,
+		      unsigned int datalen,
+		      int (*handler)(void *private, const u8 *data,
+				     unsigned int datalen))
 {
 	struct alg_sock *ask = alg_sk(sk);
-	const struct af_alg_type *type = ask->type;
-	u8 *key;
+	u8 *data;
 	int err;
 
-	key = sock_kmalloc(sk, keylen, GFP_KERNEL);
-	if (!key)
+	data = sock_kmalloc(sk, datalen, GFP_KERNEL);
+	if (!data)
 		return -ENOMEM;
 
 	err = -EFAULT;
-	if (copy_from_user(key, ukey, keylen))
+	if (copy_from_user(data, udata, datalen))
 		goto out;
 
-	err = type->setkey(ask->private, key, keylen);
+	err = handler(ask->private, data, datalen);
 
 out:
-	sock_kfree_s(sk, key, keylen);
+	sock_kfree_s(sk, data, datalen);
 
 	return err;
 }
@@ -214,7 +215,7 @@ static int alg_setsockopt(struct socket *sock, int level, int optname,
 		if (!type->setkey)
 			goto unlock;
 
-		err = alg_setkey(sk, optval, optlen);
+		err = alg_setop(sk, optval, optlen, type->setkey);
 		break;
 	case ALG_SET_AEAD_AUTHSIZE:
 		if (sock->state == SS_CONNECTED)
@@ -222,6 +223,14 @@ static int alg_setsockopt(struct socket *sock, int level, int optname,
 		if (!type->setauthsize)
 			goto unlock;
 		err = type->setauthsize(ask->private, optlen);
+		break;
+	case ALG_SET_RNG_SEED:
+		if (sock->state == SS_CONNECTED)
+			goto unlock;
+		if (!type->setseed)
+			goto unlock;
+
+		err = alg_setop(sk, optval, optlen, type->setseed);
 	}
 
 unlock:
diff --git a/include/crypto/if_alg.h b/include/crypto/if_alg.h
index 5c7b6c5..0808ed1 100644
--- a/include/crypto/if_alg.h
+++ b/include/crypto/if_alg.h
@@ -51,6 +51,7 @@ struct af_alg_type {
 	int (*setkey)(void *private, const u8 *key, unsigned int keylen);
 	int (*accept)(void *private, struct sock *sk);
 	int (*setauthsize)(void *private, unsigned int authsize);
+	int (*setseed)(void *private, const u8 *seed, unsigned int seedlen);
 
 	struct proto_ops *ops;
 	struct module *owner;
diff --git a/include/uapi/linux/if_alg.h b/include/uapi/linux/if_alg.h
index f2acd2f..973dcca 100644
--- a/include/uapi/linux/if_alg.h
+++ b/include/uapi/linux/if_alg.h
@@ -34,6 +34,7 @@ struct af_alg_iv {
 #define ALG_SET_OP			3
 #define ALG_SET_AEAD_ASSOCLEN		4
 #define ALG_SET_AEAD_AUTHSIZE		5
+#define ALG_SET_RNG_SEED		6
 
 /* Operations */
 #define ALG_OP_DECRYPT			0
-- 
2.1.0