[PATCH v2 15/18] crypto: dh - store group id in dh-generic's dh_ctx

[Nicolai Stange]

A subsequent patch will make the crypto/dh's dh_is_pubkey_valid() to
calculate the Q value from the P domain parameter for safe-prime groups,
for which by definition Q = (P - 1)/2. However, dh_is_pubkey_valid() will
need to check first whether the group in question is actually a safe-prime
group. In order to make this information available, introduce a new
->group_id member to struct dh_ctx and let dh_set_params() set it to the
value found in the struct dh as deserialized via crypto_dh_decode_key().

Signed-off-by: Nicolai Stange <nstange@xxxxxxx>
Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
---
 crypto/dh.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/crypto/dh.c b/crypto/dh.c
index 2e49b114e038..38547c5301da 100644
--- a/crypto/dh.c
+++ b/crypto/dh.c
@@ -13,6 +13,7 @@
 #include <linux/mpi.h>
 
 struct dh_ctx {
+	enum dh_group_id group_id;
 	MPI p;	/* Value is guaranteed to be set. */
 	MPI q;	/* Value is optional. */
 	MPI g;	/* Value is guaranteed to be set. */
@@ -55,6 +56,8 @@ static int dh_set_params(struct dh_ctx *ctx, struct dh *params)
 	if (dh_check_params_length(params->p_size << 3))
 		return -EINVAL;
 
+	ctx->group_id = params->group_id;
+
 	ctx->p = mpi_read_raw_data(params->p, params->p_size);
 	if (!ctx->p)
 		return -EINVAL;
-- 
2.26.2