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htlc: Add a checker function tellung us whether we can continue

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This function ensures we have all the infos we need to continue if the
htlc_accepted hook tells us to. It also enforces well-formedness of the TLV
payload if we have a TLV payload.

Suggested-by: List Neigut <@niftynei>
Signed-off-by: Christian Decker <@cdecker>
This commit is contained in:
Christian Decker 2019-11-21 17:26:30 +01:00 committed by Rusty Russell
parent e46f423ae9
commit d1df4d6959
1 changed files with 43 additions and 22 deletions
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65
lightningd/peer_htlcs.c
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@ -31,6 +31,10 @@
#include <wallet/wallet.h>
#include <wire/gen_onion_wire.h>
#ifndef SUPERVERBOSE
#define SUPERVERBOSE(...)
#endif
static bool state_update_ok(struct channel *channel,
enum htlc_state oldstate, enum htlc_state newstate,
u64 htlc_id, const char *dir)
@ -763,6 +767,44 @@ static void htlc_accepted_hook_serialize(struct htlc_accepted_hook_payload *p,
json_object_end(s);
}
/* Make sure that we can continue with a default action if the htlc_accepted
* hook tells us to. This means enforcing that we have the necessary
* information to forward, fail or accept, and that the TVL payload is encoded
* correctly. */
static bool htlc_accepted_can_continue(struct route_step *rs)
{
if (rs->type == SPHINX_TLV_PAYLOAD && !tlv_payload_is_valid(rs->payload.tlv)) {
SUPERVERBOSE("Encoding of TLV payload is invalid");
return false;
}
/* BOLT #4:
*
* The writer:
* - MUST include `amt_to_forward` and `outgoing_cltv_value` for every node.
* - MUST include `short_channel_id` for every non-final node.
* - MUST NOT include `short_channel_id` for the final node.
*
* The reader:
* - MUST return an error if `amt_to_forward` or `outgoing_cltv_value` are not present.
*/
if (rs->amt_to_forward == NULL) {
SUPERVERBOSE("Missing amt_to_forward in payload");
return false;
}
if (rs->outgoing_cltv == NULL) {
SUPERVERBOSE("Missing outgoing_cltv_value in payload");
return false;
}
if (rs->nextcase && rs->forward_channel == NULL) {
SUPERVERBOSE("Missing short_channel_id in payload");
return false;
}
return true;
}
/**
* Callback when a plugin answers to the htlc_accepted hook
*/
@ -779,32 +821,11 @@ htlc_accepted_hook_callback(struct htlc_accepted_hook_payload *request,
enum htlc_accepted_result result;
enum onion_type failure_code;
u8 *channel_update;
bool valid;
result = htlc_accepted_hook_deserialize(buffer, toks, &payment_preimage, &failure_code, &channel_update);
/* BOLT #4:
*
* The writer:
* - MUST include `amt_to_forward` and `outgoing_cltv_value` for every node.
* - MUST include `short_channel_id` for every non-final node.
* - MUST NOT include `short_channel_id` for the final node.
*
* The reader:
* - MUST return an error if `amt_to_forward` or `outgoing_cltv_value` are not present.
*/
valid = rs->amt_to_forward != NULL && rs->outgoing_cltv != NULL &&
(rs->nextcase == ONION_END ||
(rs->nextcase == ONION_FORWARD && rs->forward_channel != NULL));
/* In addition we also enforce the TLV validity rules:
* - No unknown even types
* - Types in monotonical non-repeating order
*/
valid = valid && (rs->type == SPHINX_V0_PAYLOAD || tlv_payload_is_valid(rs->payload.tlv));
switch (result) {
case htlc_accepted_continue:
if (!valid) {
if (!htlc_accepted_can_continue(rs)) {
log_debug(channel->log, "Failing HTLC because of an invalid payload");
failure_code = WIRE_INVALID_ONION_PAYLOAD;
fail_in_htlc(hin, failure_code, NULL, NULL);