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Date: Tue, 11 Nov 2014 10:34:18 +0100
From: Daniel Borkmann <dborkman@...hat.com>
To: Stephan Mueller <smueller@...onox.de>
CC: Herbert Xu <herbert@...dor.apana.org.au>,
"'Sandy Harris'" <sandyinchina@...il.com>,
linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] crypto: AF_ALG - zeroize message digest buffer
Hi Stephan,
On 11/11/2014 05:37 AM, Stephan Mueller wrote:
> Zeroize the buffer holding the message digest calculated for the
> consumer before the buffer is released by the hash AF_ALG interface
> handler.
>
> Signed-off-by: Stephan Mueller <smueller@...onox.de>
> ---
> crypto/algif_hash.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/crypto/algif_hash.c b/crypto/algif_hash.c
> index 8502462..f75db4c 100644
> --- a/crypto/algif_hash.c
> +++ b/crypto/algif_hash.c
> @@ -258,6 +258,8 @@ static void hash_sock_destruct(struct sock *sk)
> struct alg_sock *ask = alg_sk(sk);
> struct hash_ctx *ctx = ask->private;
>
> + memzero_explicit(ctx->result,
> + crypto_ahash_digestsize(crypto_ahash_reqtfm(&ctx->req)));
> sock_kfree_s(sk, ctx->result,
Perhaps something like this (alternatively kzfree() would work, too) ...
static void __sock_kfree_s(struct sock *sk, void *mem, int size,
bool clear_mem)
{
if (WARN_ON_ONCE(!mem))
return;
if (clear_mem)
memzero_explicit(mem, size);
kfree(mem);
atomic_sub(size, &sk->sk_omem_alloc);
}
void sock_kfree_s(struct sock *sk, void *mem, int size)
{
__sock_kfree_s(sk, mem, size, false);
}
EXPORT_SYMBOL(sock_kfree_s);
void sock_kzfree_s(struct sock *sk, void *mem, int size)
{
__sock_kfree_s(sk, mem, size, true);
}
EXPORT_SYMBOL(sock_kzfree_s);
... so you could then just use it as drop-in in various places:
sock_kzfree_s(sk, ctx->result, ...);
> crypto_ahash_digestsize(crypto_ahash_reqtfm(&ctx->req)));
> sock_kfree_s(sk, ctx, ctx->len);
>
Thanks,
Daniel
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