Function force_payer_secret

plugins/fetchinvoice.c:1060–1116

If they hand us the payer secret, we sign it directly, bypassing checks * about periods etc. */

/* If they hand us the payer secret, we sign it directly, bypassing checks
 * about periods etc. */
static struct command_result *
force_payer_secret(struct command *cmd,
		   struct sent *sent,
		   struct tlv_invoice_request *invreq,
		   const struct secret *payer_secret)
{
	struct sha256 merkle, sha;
	enum nodeid_parity parity;
	secp256k1_keypair kp;
	u8 *msg;
	const u8 *p;
	size_t len;

	if (secp256k1_keypair_create(secp256k1_ctx, &kp, payer_secret->data) != 1)
		return command_fail(cmd, LIGHTNINGD, "Bad payer_secret");

	invreq->payer_key = tal(invreq, struct point32);
	/* Docs say this only happens if arguments are invalid! */
	if (secp256k1_keypair_xonly_pub(secp256k1_ctx,
					&invreq->payer_key->pubkey, NULL,
					&kp) != 1)
		plugin_err(cmd->plugin,
			   "secp256k1_keypair_pub failed on %s?",
			   type_to_string(tmpctx, struct secret, payer_secret));

	/* Linearize populates ->fields */
	msg = tal_arr(tmpctx, u8, 0);
	towire_tlv_invoice_request(&msg, invreq);
	p = msg;
	len = tal_bytelen(msg);
	sent->invreq = fromwire_tlv_invoice_request(cmd, &p, &len);
	if (!sent->invreq)
		plugin_err(cmd->plugin,
			   "Could not remarshall invreq %s", tal_hex(tmpctx, msg));

	merkle_tlv(sent->invreq->fields, &merkle);
	sighash_from_merkle("invoice_request", "signature", &merkle, &sha);

	sent->invreq->signature = tal(invreq, struct bip340sig);
	if (!secp256k1_schnorrsig_sign32(secp256k1_ctx,
				       sent->invreq->signature->u8,
				       sha.u.u8,
				       &kp,
				       NULL)) {
		return command_fail(cmd, LIGHTNINGD,
				    "Failed to sign with payer_secret");
	}

	sent->path = path_to_node(sent, cmd->plugin,
				  sent->offer->node_id,
				  &parity);
	if (!sent->path)
		return connect_direct(cmd, sent->offer->node_id, parity,
				      sendinvreq_after_connect, sent);

	return sendinvreq_after_connect(cmd, NULL, NULL, sent);
}