dragonfly: Disable use of groups using Brainpool curves

Disable groups that use Brainpool curves for now since they leak more
timing information due to the prime not being close to a power of two.
This removes use of groups 28, 29, and 30 from SAE and EAP-pwd.

Signed-off-by: Jouni Malinen <j@w1.fi>

src/common/dragonfly.c

@@ -21,9 +21,11 @@ int dragonfly_suitable_group(int group, int ecc_only)
 	 * purposes: FFC groups whose prime is >= 3072 bits and ECC groups
 	 * defined over a prime field whose prime is >= 256 bits. Furthermore,
 	 * ECC groups defined over a characteristic 2 finite field and ECC
-	 * groups with a co-factor greater than 1 are not suitable. */
+	 * groups with a co-factor greater than 1 are not suitable. Disable
+	 * groups that use Brainpool curves as well for now since they leak more
+	 * timing information due to the prime not being close to a power of
+	 * two. */
 	return group == 19 || group == 20 || group == 21 ||
-		group == 28 || group == 29 || group == 30 ||
 		(!ecc_only &&
 		 (group == 15 || group == 16 || group == 17 || group == 18));
 }