[PATCH] crypto: Add support for ALG_SET_KEY_ID for skcipher

[Marcel Holtmann]

This adds support for a new socket options called ALG_SET_KEY_ID that
allows providing the symmetric key via a key serial from the keys
subsystem.

NOTE: Currently we do not have a dedicated symmetric key type and using
the user key type is not optional. Also lookup_user_key() is currently
private to the keys subsystem and might need to be exposed to usage by
the crypto subystem first. This is just a RFC and not for merging !!!

Signed-off-by: Marcel Holtmann 
---
 crypto/af_alg.c | 14 ++
 crypto/algif_skcipher.c | 25 +
 include/crypto/if_alg.h |  2 ++
 include/uapi/linux/if_alg.h |  1 +
 4 files changed, 42 insertions(+)

diff --git a/crypto/af_alg.c b/crypto/af_alg.c
index a8e7aa3e257b..48ddbb4063aa 100644
--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -203,6 +203,7 @@ static int alg_setsockopt(struct socket *sock, int level, 
int optname,
struct alg_sock *ask = alg_sk(sk);
const struct af_alg_type *type;
int err = -ENOPROTOOPT;
+   key_serial_t keyid;
 
lock_sock(sk);
type = ask->type;
@@ -225,6 +226,19 @@ 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_KEY_ID:
+   if (sock->state == SS_CONNECTED)
+   goto unlock;
+   if (!type->setkeyid)
+   goto unlock;
+
+   err = -EFAULT;
+   if (get_user(keyid, (key_serial_t __user *) optval))
+   goto unlock;
+
+   err = type->setkeyid(ask->private, keyid);
+   break;
}
 
 unlock:
diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c
index 945075292bc9..5dfae3cb6e20 100644
--- a/crypto/algif_skcipher.c
+++ b/crypto/algif_skcipher.c
@@ -22,6 +22,8 @@
 #include 
 #include 
 #include 
+#include 
+#include "../security/keys/internal.h"
 
 struct skcipher_sg_list {
struct list_head list;
@@ -764,6 +766,28 @@ static int skcipher_setkey(void *private, const u8 *key, 
unsigned int keylen)
return crypto_ablkcipher_setkey(private, key, keylen);
 }
 
+static int skcipher_setkeyid(void *private, key_serial_t id)
+{
+   key_ref_t key_ref;
+   int err = -EPROTOTYPE;
+
+   key_ref = lookup_user_key(id, 0, KEY_NEED_READ);
+   if (IS_ERR(key_ref))
+   return PTR_ERR(key_ref);
+
+   if (key_ref_to_ptr(key_ref)->type == _type_user) {
+   struct user_key_payload *upayload;
+
+   upayload = rcu_dereference_key(key_ref_to_ptr(key_ref));
+
+   err = crypto_ablkcipher_setkey(private, upayload->data,
+  upayload->datalen);
+   }
+
+   key_ref_put(key_ref);
+   return err;
+}
+
 static void skcipher_wait(struct sock *sk)
 {
struct alg_sock *ask = alg_sk(sk);
@@ -832,6 +856,7 @@ static const struct af_alg_type algif_type_skcipher = {
.bind   =   skcipher_bind,
.release=   skcipher_release,
.setkey =   skcipher_setkey,
+   .setkeyid   =   skcipher_setkeyid,
.accept =   skcipher_accept_parent,
.ops=   _skcipher_ops,
.name   =   "skcipher",
diff --git a/include/crypto/if_alg.h b/include/crypto/if_alg.h
index 018afb264ac2..f71d88162326 100644
--- a/include/crypto/if_alg.h
+++ b/include/crypto/if_alg.h
@@ -17,6 +17,7 @@
 #include 
 #include 
 #include 
+#include 
 #include 
 #include 
 
@@ -51,6 +52,7 @@ 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 (*setkeyid)(void *private, key_serial_t id);
 
struct proto_ops *ops;
struct module *owner;
diff --git a/include/uapi/linux/if_alg.h b/include/uapi/linux/if_alg.h
index d81dcca5bdd7..28cdc05695c0 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_KEY_ID 6
 
 /* Operations */
 #define ALG_OP_DECRYPT 0
-- 
2.4.3

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Re: [PATCH] crypto: Add support for ALG_SET_KEY_ID for skcipher

[Marcel Holtmann]

Hi Stephan,

>> This adds support for a new socket options called ALG_SET_KEY_ID that
>> allows providing the symmetric key via a key serial from the keys
>> subsystem.
>> 
>> NOTE: Currently we do not have a dedicated symmetric key type and using
>> the user key type is not optional. Also lookup_user_key() is currently
>> private to the keys subsystem and might need to be exposed to usage by
>> the crypto subystem first. This is just a RFC and not for merging !!!
> 
> First, thanks for sharing.
> 
> Albeit I have not had a deep look into that code, but I think your patch is 
> incomplete: you have to tie the kernel crypto API to the key retention system 
> in the Kconfig.
> 
> I guess that is one of the concerns that Herbert may have? See my other email 
> regarding this.

of course we have to tie this together. And I need to deal with Kconfig once we 
have symmetric key type support.

However I am not too much worried since reality is that the keys subsystem is 
pretty much mandatory if you use module signing (or firmware signing in the 
future). And with moving the keys subsystem to use akcipher and consolidate on 
a single RSA implementation in the kernel, I am not convinced that this is 
actually a real problem.

Also it is perfectly valid to return EOPNOTSUPP when using ALG_SET_KEY_ID and 
you do not have the keys subsystem configured. I do not see that as a problem.

Regards

Marcel

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