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crypto: dh - allow for passing NULL to the ffdheXYZ(dh)s' ->set_secret()

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Ephemeral key generation can be requested from any of the ffdheXYZ(dh)
variants' common ->set_secret() by passing it an (encoded) struct dh
with the key parameter being unset, i.e. with ->key_size == 0. As the
whole purpose of the ffdheXYZ(dh) templates is to fill in the group
parameters as appropriate, they expect ->p and ->g to be unset in any
input struct dh as well. This means that a user would have to encode an
all-zeroes struct dh instance via crypto_dh_encode_key() when requesting
ephemeral key generation from a ffdheXYZ(dh) instance, which is kind of
pointless.

Make dh_safe_prime_set_secret() to decode a struct dh from the supplied
buffer only if the latter is non-NULL and initialize it with all zeroes
otherwise.

That is, it is now possible to call

  crypto_kpp_set_secret(tfm, NULL, 0);

on any ffdheXYZ(dh) tfm for requesting ephemeral key generation.

Signed-off-by: Nicolai Stange <nstange@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Nicolai Stange 2022-02-21 13:10:57 +01:00 committed by Herbert Xu
parent 209b7fc9c9
commit c8e8236cf7
1 changed files with 8 additions and 7 deletions
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15
crypto/dh.c
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@ -444,17 +444,18 @@ static int dh_safe_prime_set_secret(struct crypto_kpp *tfm, const void *buffer,
struct dh_safe_prime_instance_ctx *inst_ctx = struct dh_safe_prime_instance_ctx *inst_ctx =
dh_safe_prime_instance_ctx(tfm); dh_safe_prime_instance_ctx(tfm);
struct dh_safe_prime_tfm_ctx *tfm_ctx = kpp_tfm_ctx(tfm); struct dh_safe_prime_tfm_ctx *tfm_ctx = kpp_tfm_ctx(tfm);
struct dh params; struct dh params = {};
void *buf = NULL, *key = NULL; void *buf = NULL, *key = NULL;
unsigned int buf_size; unsigned int buf_size;
int err; int err;
err = __crypto_dh_decode_key(buffer, len, &params); if (buffer) {
if (err) err = __crypto_dh_decode_key(buffer, len, &params);
return err; if (err)
return err;
if (params.p_size || params.g_size) if (params.p_size || params.g_size)
return -EINVAL; return -EINVAL;
}
params.p = inst_ctx->safe_prime->p; params.p = inst_ctx->safe_prime->p;
params.p_size = inst_ctx->safe_prime->p_size; params.p_size = inst_ctx->safe_prime->p_size;