SAE: Increment the Sc counter before generating each Confirm

This changes the Send-Confirm value for the first SAE Confirm message to
be 1 instead of 0 for all cases to match the design shown in IEEE Std
802.11-2020, Figure 12-4 (SAE finite state machine).

Sc is defined to be "the number of SAE Confirm messages that have been
sent" which is a bit vague on whether the current frame is included in
the count or not. However, the state machine is showing inc(Sc)
operation in all cases before the "2" event to build the Confirm.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>

src/common/sae.c

@@ -2268,10 +2268,10 @@ int sae_write_confirm(struct sae_data *sae, struct wpabuf *buf)
 	hash_len = sae->tmp->kck_len;
 
 	/* Send-Confirm */
-	sc = wpabuf_put(buf, 0);
-	wpabuf_put_le16(buf, sae->send_confirm);
 	if (sae->send_confirm < 0xffff)
 		sae->send_confirm++;
+	sc = wpabuf_put(buf, 0);
+	wpabuf_put_le16(buf, sae->send_confirm);
 
 	if (sae->tmp->ec)
 		res = sae_cn_confirm_ecc(sae, sc, sae->tmp->own_commit_scalar,