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#include <bitcoin/preimage.h>
#include <ccan/array_size/array_size.h>
#include <ccan/tal/str/str.h>
#include <plugins/libplugin.h>
#include <wire/gen_onion_wire.h>
#define PREIMAGE_TLV_TYPE 5482373484
#define KEYSEND_FEATUREBIT 55
static void init(struct plugin *p, const char *buf UNUSED,
const jsmntok_t *config UNUSED)
{
}
static const struct plugin_command commands[] = {
};
static struct command_result *
htlc_accepted_continue(struct command *cmd, struct tlv_tlv_payload *payload)
{
struct json_stream *response;
response = jsonrpc_stream_success(cmd);
json_add_string(response, "result", "continue");
if (payload) {
u8 *binpayload = tal_arr(cmd, u8, 0);
towire_tlvstream_raw(&binpayload, payload->fields);
json_add_string(response, "payload", tal_hex(cmd, binpayload));
}
return command_finished(cmd, response);
}
/* Struct wrapping the information we extract from an incoming keysend
* payment */
struct keysend_in {
struct sha256 payment_hash;
struct preimage payment_preimage;
char *label;
struct tlv_tlv_payload *payload;
struct tlv_field *preimage_field;
};
static struct command_result *
htlc_accepted_invoice_created(struct command *cmd, const char *buf UNUSED,
const jsmntok_t *result UNUSED,
struct keysend_in *ki)
{
int preimage_field_idx = ki->preimage_field - ki->payload->fields;
/* Remove the preimage field so `lightningd` knows how to handle
* this. */
tal_arr_remove(&ki->payload->fields, preimage_field_idx);
/* Finally we can resolve the payment with the preimage. */
plugin_log(cmd->plugin, LOG_INFORM,
"Resolving incoming HTLC with preimage for payment_hash %s "
"provided in the onion payload.",
tal_hexstr(tmpctx, &ki->payment_hash, sizeof(struct sha256)));
return htlc_accepted_continue(cmd, ki->payload);
}
static struct command_result *htlc_accepted_call(struct command *cmd,
const char *buf,
const jsmntok_t *params)
{
const jsmntok_t *payloadt = json_delve(buf, params, ".onion.payload");
const jsmntok_t *payment_hash_tok = json_delve(buf, params, ".htlc.payment_hash");
const u8 *rawpayload;
size_t max;
struct tlv_tlv_payload *payload;
struct tlv_field *preimage_field = NULL;
char *hexpreimage, *hexpaymenthash;
bigsize_t s;
bool unknown_even_type = false;
struct tlv_field *field;
struct keysend_in *ki;
struct out_req *req;
struct timeabs now = time_now();
if (!payloadt)
return htlc_accepted_continue(cmd, NULL);
rawpayload = json_tok_bin_from_hex(cmd, buf, payloadt);
max = tal_bytelen(rawpayload);
payload = tlv_tlv_payload_new(cmd);
s = fromwire_varint(&rawpayload, &max);
if (s != max) {
return htlc_accepted_continue(cmd, NULL);
}
if (!fromwire_tlv_payload(&rawpayload, &max, payload)) {
plugin_log(
cmd->plugin, LOG_UNUSUAL, "Malformed TLV payload %.*s",
payloadt->end - payloadt->start, buf + payloadt->start);
return htlc_accepted_continue(cmd, NULL);
}
/* Try looking for the field that contains the preimage */
for (int i=0; i<tal_count(payload->fields); i++) {
field = &payload->fields[i];
if (field->numtype == PREIMAGE_TLV_TYPE) {
preimage_field = field;
break;
} else if (field->numtype % 2 == 0 && field->meta == NULL) {
unknown_even_type = true;
break;
}
}
/* If we don't have a preimage field then this is not a keysend, let
* someone else take care of it. */
if (preimage_field == NULL)
return htlc_accepted_continue(cmd, NULL);
if (unknown_even_type) {
plugin_log(cmd->plugin, LOG_UNUSUAL,
"Payload contains unknown even TLV-type %" PRIu64
", can't safely accept the keysend. Deferring to "
"other plugins.",
preimage_field->numtype);
return htlc_accepted_continue(cmd, NULL);
}
/* If the preimage is not 32 bytes long then we can't accept the
* payment. */
if (preimage_field->length != 32) {
plugin_log(cmd->plugin, LOG_UNUSUAL,
"Sender specified a preimage that is %zu bytes long, "
"we expected 32 bytes. Ignoring this HTLC.",
preimage_field->length);
return htlc_accepted_continue(cmd, NULL);
}
ki = tal(cmd, struct keysend_in);
memcpy(&ki->payment_preimage, preimage_field->value, 32);
ki->label = tal_fmt(ki, "keysend-%lu.%09lu", (unsigned long)now.ts.tv_sec, now.ts.tv_nsec);
ki->payload = tal_steal(ki, payload);
ki->preimage_field = preimage_field;
hexpreimage = tal_hex(cmd, preimage_field->value);
/* If the preimage doesn't hash to the payment_hash we must continue,
* maybe someone else knows how to handle these. */
sha256(&ki->payment_hash, preimage_field->value, preimage_field->length);
hexpaymenthash = tal_hexstr(cmd, &ki->payment_hash, sizeof(ki->payment_hash));
if (!json_tok_streq(buf, payment_hash_tok, hexpaymenthash)) {
plugin_log(
cmd->plugin, LOG_UNUSUAL,
"Preimage provided by the sender does not match the "
"payment_hash: SHA256(%s)=%s != %.*s. Ignoring keysend.",
hexpreimage, hexpaymenthash,
payment_hash_tok->end - payment_hash_tok->start,
buf + payment_hash_tok->start);
tal_free(ki);
return htlc_accepted_continue(cmd, NULL);
}
/* Now we can call `invoice` RPC to backfill an invoce matching this
* spontaneous payment, thus leaving us with an accounting
* trace. Creating the invoice is best effort: it may fail if the
* `payment_hash` is already attached to an existing invoice, and the
* label could collide (unlikely since we use the nanosecond time). If
* the call to `invoice` fails we will just continue, and `lightningd`
* will be nice and reject the payment. */
req = jsonrpc_request_start(cmd->plugin, cmd, "invoice",
&htlc_accepted_invoice_created,
&htlc_accepted_invoice_created,
ki);
plugin_log(cmd->plugin, LOG_INFORM, "Inserting a new invoice for keysend with payment_hash %s", hexpaymenthash);
json_add_string(req->js, "msatoshi", "any");
json_add_string(req->js, "label", ki->label);
json_add_string(req->js, "description", "Spontaneous incoming payment through keysend");
json_add_preimage(req->js, "preimage", &ki->payment_preimage);
return send_outreq(cmd->plugin, req);
}
static const struct plugin_hook hooks[] = {
{
"htlc_accepted",
htlc_accepted_call
},
};
int main(int argc, char *argv[])
{
struct feature_set features;
setup_locale();
for (int i=0; i<ARRAY_SIZE(features.bits); i++)
features.bits[i] = tal_arr(NULL, u8, 0);
set_feature_bit(&features.bits[NODE_ANNOUNCE_FEATURE], KEYSEND_FEATUREBIT);
plugin_main(argv, init, PLUGIN_STATIC, &features, commands,
ARRAY_SIZE(commands), NULL, 0, hooks, ARRAY_SIZE(hooks),
NULL);
}