Function create_onionpacket

common/sphinx.c:526–638

}

struct onionpacket *create_onionpacket(
	const tal_t *ctx,
	struct sphinx_path *sp,
	size_t fixed_size,
	struct secret **path_secrets
	)
{
	struct onionpacket *packet = talz(ctx, struct onionpacket);
	int i, num_hops = tal_count(sp->hops);
	size_t fillerSize = sphinx_path_payloads_size(sp) -
			      sphinx_hop_size(&sp->hops[num_hops - 1]);
	u8 *filler;
	struct secret padkey;
	struct hmac nexthmac;
	struct hop_params *params;
	struct secret *secrets = tal_arr(ctx, struct secret, num_hops);
	size_t payloads_size = sphinx_path_payloads_size(sp);
	size_t max_prefill = fixed_size - payloads_size;

	if (sphinx_path_payloads_size(sp) > fixed_size) {
		tal_free(packet);
		tal_free(secrets);
		return NULL;
	}
	packet->routinginfo = tal_arr(packet, u8, fixed_size);

	if (sp->session_key == NULL) {
		sp->session_key = tal(sp, struct secret);
		randbytes(sp->session_key, sizeof(struct secret));
	}

	params = generate_hop_params(ctx, sp->session_key->data, sp);
	if (!params) {
		tal_free(packet);
		tal_free(secrets);
		return NULL;
	}
	packet->version = 0;
	memset(nexthmac.bytes, 0, sizeof(nexthmac.bytes));

	/* BOLT #4:
	 *
	 * The packet is initialized with 1300 _random_ bytes derived from a
	 * CSPRNG
	 */
	/* Note that this is just hop_payloads: the rest of the packet is
	 * overwritten below or above anyway. */
	subkey_from_hmac("pad", sp->session_key, &padkey);
	generate_cipher_stream(packet->routinginfo, &padkey, fixed_size);

	filler = tal_arr(tmpctx, u8, fillerSize);
	generate_header_padding(filler, tal_bytelen(filler), fixed_size, sp, params);

	if (sp->rendezvous_id != NULL)
		/* FIXME: Fuzz this or expose to the caller to hide encoded
		 * route length. */
		sphinx_prefill(packet->routinginfo, sp, max_prefill, params,
			       fixed_size);