hsmd: refactor hsmd_init

Remove preapprove_check capabilities by selecting
WIRE_HSMD_PREAPPROVE_INCOICE_CHECK and
WIRE_HSMD_PREAPPROVE_KEYSEND_CHECK from capabilities array instead of
assuming those occupy the last two slots in the array.

Changelog-None

Signed-off-by: Lagrang3 <lagrang3@protonmail.com>

Author: Lagrang3

hsmd/libhsmd.c

@@ -2337,7 +2337,7 @@ u8 *hsmd_init(struct secret hsm_secret, const u64 hsmd_version,
 		WIRE_HSMD_PREAPPROVE_INVOICE_CHECK,
 		WIRE_HSMD_PREAPPROVE_KEYSEND_CHECK,
 	};
-	const u32 *caps;
+	u32 *caps;
 
 	/*~ Don't swap this. */
 	sodium_mlock(secretstuff.hsm_secret.data,
@@ -2460,14 +2460,18 @@ u8 *hsmd_init(struct secret hsm_secret, const u64 hsmd_version,
 		    "derived secrets", strlen("derived secrets"));
 
 	/* Capabilities arg needs to be a tal array */
-	if (dev_no_preapprove_check) {
-		/* Skip preapprove capabilities */
-		caps = tal_dup_arr(tmpctx, u32,
-				   capabilities, ARRAY_SIZE(capabilities) - 2,
-				   0);
-	} else {
-		caps = tal_dup_arr(tmpctx, u32,
-				   capabilities, ARRAY_SIZE(capabilities), 0);
+	caps = tal_arr(tmpctx, u32, 0);
+	for (size_t i = 0; i < ARRAY_SIZE(capabilities); i++) {
+		switch (capabilities[i]) {
+		case WIRE_HSMD_PREAPPROVE_INVOICE_CHECK:
+		case WIRE_HSMD_PREAPPROVE_KEYSEND_CHECK:
+			if (!dev_no_preapprove_check)
+				tal_arr_expand(&caps, capabilities[i]);
+			/* else: Skip preapprove capabilities */
+			break;
+		default:
+			tal_arr_expand(&caps, capabilities[i]);
+		}
 	}
 
 	/*~ Note: marshalling a bip32 tree only marshals the public side,