linux-kernel - Re: [PATCH v2 3/5] crypto: AF_ALG -- add setpubkey setsockopt call

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Date:	Fri, 30 Oct 2015 09:42:27 +0100
From:	Stephan Mueller <smueller@...onox.de>
To:	Marcel Holtmann <marcel@...tmann.org>
Cc:	Herbert Xu <herbert@...dor.apana.org.au>,
	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-api@...r.kernel.org
Subject: Re: [PATCH v2 3/5] crypto: AF_ALG -- add setpubkey setsockopt call

Am Freitag, 30. Oktober 2015, 17:16:47 schrieb Marcel Holtmann:

Hi Marcel,

>Hi Stephan,
>
>> For supporting asymmetric ciphers, user space must be able to set the
>> public key. The patch adds a new setsockopt call for setting the public
>> key.
>> 
>> Signed-off-by: Stephan Mueller <smueller@...onox.de>
>> ---
>> crypto/af_alg.c         | 14 +++++++++++---
>> include/crypto/if_alg.h |  1 +
>> 2 files changed, 12 insertions(+), 3 deletions(-)
>> 
>> diff --git a/crypto/af_alg.c b/crypto/af_alg.c
>> index a8e7aa3..bf6528e 100644
>> --- a/crypto/af_alg.c
>> +++ b/crypto/af_alg.c
>> @@ -173,13 +173,16 @@ static int alg_bind(struct socket *sock, struct
>> sockaddr *uaddr, int addr_len) }
>> 
>> static int alg_setkey(struct sock *sk, char __user *ukey,
>> -		      unsigned int keylen)
>> +		      unsigned int keylen, bool pubkey)
>> {
>> 
>> 	struct alg_sock *ask = alg_sk(sk);
>> 	const struct af_alg_type *type = ask->type;
>> 	u8 *key;
>> 	int err;
>> 
>> +	if (pubkey && !type->setpubkey)
>> +		return -EOPNOTSUPP;
>> +
>> 
>> 	key = sock_kmalloc(sk, keylen, GFP_KERNEL);
>> 	if (!key)
>> 	
>> 		return -ENOMEM;
>> 
>> @@ -188,7 +191,10 @@ static int alg_setkey(struct sock *sk, char __user
>> *ukey,> 
>> 	if (copy_from_user(key, ukey, keylen))
>> 	
>> 		goto out;
>> 
>> -	err = type->setkey(ask->private, key, keylen);
>> +	if (pubkey)
>> +		err = type->setpubkey(ask->private, key, keylen);
>> +	else
>> +		err = type->setkey(ask->private, key, keyless);
>
>why is this kind of hackery needed? Why not just introduce alg_setpubkey to
>keep this a lot cleaner.

You are fully correct. I wanted to spare a re-implementation of the setkey 
function. But instead of that hack, having something like the following would 
be much cleaner:

setkey_common() {
...
	heavy lifting
...
}

setpubkey() {
	setkey_common(type->setpubkey)
}

setkey() {
	setkey_common(type->setkey)
}

>> out:
>> 	sock_kzfree_s(sk, key, keylen);
>> 
>> @@ -212,12 +218,14 @@ static int alg_setsockopt(struct socket *sock, int
>> level, int optname,> 
>> 	switch (optname) {
>> 
>> 	case ALG_SET_KEY:
>> +	case ALG_SET_PUBKEY:
>> 		if (sock->state == SS_CONNECTED)
>> 		
>> 			goto unlock;
>> 		
>> 		if (!type->setkey)
>> 		
>> 			goto unlock;
>> 
>> -		err = alg_setkey(sk, optval, optlen);
>> +		err = alg_setkey(sk, optval, optlen,
>> +				 (optname == ALG_SET_PUBKEY) ? true : false);
>> 
>> 		break;
>
>Same here. Why not give ALG_SET_PUBKEY a separate case statement. Especially
>since you have to check type->setkey vs type->setpubkey.

Same here.

>> 	case ALG_SET_AEAD_AUTHSIZE:
>> 		if (sock->state == SS_CONNECTED)
>> 
>> diff --git a/include/crypto/if_alg.h b/include/crypto/if_alg.h
>> index 018afb2..ca4dc72 100644
>> --- a/include/crypto/if_alg.h
>> +++ b/include/crypto/if_alg.h
>> @@ -49,6 +49,7 @@ struct af_alg_type {
>> 
>> 	void *(*bind)(const char *name, u32 type, u32 mask);
>> 	void (*release)(void *private);
>> 	int (*setkey)(void *private, const u8 *key, unsigned int keylen);
>> 
>> +	int (*setpubkey)(void *private, const u8 *key, unsigned int keylen);
>> 
>> 	int (*accept)(void *private, struct sock *sk);
>> 	int (*setauthsize)(void *private, unsigned int authorize);
>
>Regards
>
>Marcel

Thanks.

Ciao
Stephan
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