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Restore any missing psbt metadata that resource constrained signers strip #6767

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merged 1 commit into from
Oct 25, 2023
Merged

Restore any missing psbt metadata that resource constrained signers strip #6767

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16 changes: 16 additions & 0 deletions bitcoin/psbt.c
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Original file line number Diff line number Diff line change
Expand Up @@ -86,6 +86,22 @@ struct wally_psbt *new_psbt(const tal_t *ctx, const struct wally_tx *wtx)
return psbt;
}

struct wally_psbt *combine_psbt(const tal_t *ctx,
const struct wally_psbt *psbt0,
const struct wally_psbt *psbt1)
{
struct wally_psbt *combined_psbt;
tal_wally_start();
if (wally_psbt_clone_alloc(psbt0, 0, &combined_psbt) != WALLY_OK)
abort();
if (wally_psbt_combine(combined_psbt, psbt1) != WALLY_OK) {
tal_wally_end_onto(ctx, combined_psbt, struct wally_psbt);
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Is this the right thing to do here? Should we free the memory immediately instead?

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I think this is right, because from the docs of tal_wally_end_onto I found that
this method iterates over an object allocated by libwally. So I guess it is the safe way to delete an object that wally worked on?

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This works, but leaks the combined_psbt. You should return tal_free(combined_psbt); after this (of course, this code shouldn't happen at all, since the HSM said the PSBT was good!).

return tal_free(combined_psbt);
}
tal_wally_end_onto(ctx, combined_psbt, struct wally_psbt);
return combined_psbt;
}

bool psbt_is_finalized(const struct wally_psbt *psbt)
{
size_t is_finalized;
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11 changes: 11 additions & 0 deletions bitcoin/psbt.h
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Expand Up @@ -50,6 +50,17 @@ struct wally_psbt *new_psbt(const tal_t *ctx,
*/
struct wally_psbt *clone_psbt(const tal_t *ctx, struct wally_psbt *psbt);

/**
* combine_psbt - Combine two PSBT into a cloned copy
*
* @ctx - allocation context
* @psbt0 - one psbt
* @psbt1 - other psbt
*/
struct wally_psbt *combine_psbt(const tal_t *ctx,
const struct wally_psbt *psbt0,
const struct wally_psbt *psbt1);

/**
* psbt_is_finalized - Check if tx is ready to be extracted
*
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19 changes: 16 additions & 3 deletions wallet/walletrpc.c
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Expand Up @@ -799,15 +799,28 @@ static struct command_result *json_signpsbt(struct command *cmd,
"HSM gave bad sign_withdrawal_reply %s",
tal_hex(tmpctx, msg));

if (!psbt_set_version(signed_psbt, psbt_version)) {
/* Some signers (VLS) prune the input.utxo data as it's used
* because it is too large to store in the signer. We can
* restore this metadata by combining the signed psbt back
* into a clone of the original psbt. */
struct wally_psbt *combined_psbt;
combined_psbt = combine_psbt(cmd, psbt, signed_psbt);
if (!combined_psbt) {
return command_fail(cmd, LIGHTNINGD,
"Unable to combine signed psbt: %s",
type_to_string(tmpctx, struct wally_psbt,
signed_psbt));
}

if (!psbt_set_version(combined_psbt, psbt_version)) {
return command_fail(cmd, LIGHTNINGD,
"Signed PSBT unable to have version set: %s",
type_to_string(tmpctx, struct wally_psbt,
psbt));
combined_psbt));
}

response = json_stream_success(cmd);
json_add_psbt(response, "signed_psbt", signed_psbt);
json_add_psbt(response, "signed_psbt", combined_psbt);
return command_success(cmd, response);
}

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