diff mbox series

crypto: ecdh - explicitly zeroize private_key

Message ID 20240320045106.61875-1-git@jvdsn.com (mailing list archive)
State Changes Requested
Delegated to: Herbert Xu
Headers show
Series crypto: ecdh - explicitly zeroize private_key | expand

Commit Message

Joachim Vandersmissen March 20, 2024, 4:51 a.m. UTC
private_key is overwritten with the key parameter passed in by the
caller (if present), or alternatively a newly generated private key.
However, it is possible that the caller provides a key (or the newly
generated key) which is shorter than the previous key. In that
scenario, some key material from the previous key would not be
overwritten. The easiest solution is to explicitly zeroize the entire
private_key array first.

Note that this patch slightly changes the behavior of this function:
previously, if the ecc_gen_privkey failed, the old private_key would
remain. Now, the private_key is always zeroized. This behavior is
consistent with the case where params.key is set and ecc_is_key_valid
fails.

Signed-off-by: Joachim Vandersmissen <git@jvdsn.com>
---
 crypto/ecdh.c | 2 ++
 1 file changed, 2 insertions(+)

Comments

Herbert Xu March 28, 2024, 10:17 a.m. UTC | #1
On Tue, Mar 19, 2024 at 11:51:06PM -0500, Joachim Vandersmissen wrote:
>
> diff --git a/crypto/ecdh.c b/crypto/ecdh.c
> index 80afee3234fb..ce332b39b705 100644
> --- a/crypto/ecdh.c
> +++ b/crypto/ecdh.c
> @@ -33,6 +33,8 @@ static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
>  	    params.key_size > sizeof(u64) * ctx->ndigits)
>  		return -EINVAL;
>  
> +	memzero_explicit(ctx->private_key, sizeof(ctx->private_key));

Please use memset instead of memzero_explicit unless it is actually
needed (which is not the case here).

I know there is another memzero_explicit in this function which should
also be memset so it's not your fault.

Thanks,
diff mbox series

Patch

diff --git a/crypto/ecdh.c b/crypto/ecdh.c
index 80afee3234fb..ce332b39b705 100644
--- a/crypto/ecdh.c
+++ b/crypto/ecdh.c
@@ -33,6 +33,8 @@  static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
 	    params.key_size > sizeof(u64) * ctx->ndigits)
 		return -EINVAL;
 
+	memzero_explicit(ctx->private_key, sizeof(ctx->private_key));
+
 	if (!params.key || !params.key_size)
 		return ecc_gen_privkey(ctx->curve_id, ctx->ndigits,
 				       ctx->private_key);