Re: [PATCH v2 03/18] crypto: dh - optimize domain parameter serialization for well-known groups

Hannes Reinecke [off-list ref] writes:

On 12/9/21 10:03 AM, Nicolai Stange wrote:

quoted

diff --git a/crypto/dh_helper.c b/crypto/dh_helper.c
index aabc91e4f63f..9f21204e5dee 100644
--- a/crypto/dh_helper.c
+++ b/crypto/dh_helper.c

@@ -45,18 +72,24 @@ int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params)
 		.type = CRYPTO_KPP_SECRET_TYPE_DH,
 		.len = len
 	};
+	int group_id;
 
 	if (unlikely(!len))
 		return -EINVAL;
 
 	ptr = dh_pack_data(ptr, end, &secret, sizeof(secret));
+	group_id = (int)params->group_id;
+	ptr = dh_pack_data(ptr, end, &group_id, sizeof(group_id));

Me being picky again.
To my knowledge, 'int' doesn't have a fixed width, but is rather only
guaranteed to hold certain values.
So as soon as one relies on any fixed size (as this one does) I tend to
use fixed size type like 'u32' to make it absolutely clear what is to be
expected here.

But the I don't know the conventions in the crypto code; if an 'int' is
assumed to be 32 bits throughout the crypto code I guess we should be fine.

Yes, I thought about this, too. However, the other, already existing
fields like ->key_size and ->p_size are getting serialized as unsigned
ints and I decided to stick to that for ->group_id as well. Except for
the testmgr vectors, the encoding is internal to the
crypto_dh_encode_key() and crypto_dh_decode_key() pair anyway -- all
that would happen if sizeof(int) != 4 is that the tests would fail.

So, IMO, making the serialization of struct dh to use u32 throughout is
not really in scope for this series and would probably deserve a patch
on its own, if desired.

Thanks,

Nicolai

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