derive_basepoints: actually derive a separate HTLC key.

This means we'll find anywhere still using the payment key,
even though we still expose the private payment key to channeld.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

common/derive_basepoints.c

@@ -11,7 +11,7 @@ bool derive_basepoints(const struct privkey *seed,
 		       struct sha256 *shaseed)
 {
 	struct keys {
-		struct privkey f, r, p, d;
+		struct privkey f, r, h, p, d;
 		struct sha256 shaseed;
 	} keys;
 
@@ -22,8 +22,7 @@ bool derive_basepoints(const struct privkey *seed,
 		secrets->funding_privkey = keys.f;
 		secrets->revocation_basepoint_secret = keys.r.secret;
 		secrets->payment_basepoint_secret = keys.p.secret;
-		/* We currently make htlc_basepoint_secret the same */
-		secrets->htlc_basepoint_secret = keys.p.secret;
+		secrets->htlc_basepoint_secret = keys.h.secret;
 		secrets->delayed_payment_basepoint_secret = keys.d.secret;
 	}
 
@@ -34,8 +33,8 @@ bool derive_basepoints(const struct privkey *seed,
 
 	if (basepoints) {
 		if (!pubkey_from_privkey(&keys.r, &basepoints->revocation)
-		    || !pubkey_from_privkey(&keys.p, &basepoints->htlc)
 		    || !pubkey_from_privkey(&keys.p, &basepoints->payment)
+		    || !pubkey_from_privkey(&keys.h, &basepoints->htlc)
 		    || !pubkey_from_privkey(&keys.d, &basepoints->delayed_payment))
 			return false;
 	}