We comment out a newly-added assert from the Bitcoin
side, because it's unclear how to replicate it
correctly in Elements.
Co-authored-by: Glenn Willen <gwillen@nerdnet.org>
For all spelling lints, either fix them in place, or add them to the
ignore list.
I don't understand how these have gotten in here without ever
triggering the linter until now. I'm not sure if it's something about
my test environment or what. But fixing them can't hurt.
Prior to coin selection we need to indicate that the issuances will take
extra space, otherwise we may fail to select enough coins to cover our
fees, triggering the new "fee needed exceeds fees available" assertion.
The Elements 22 blinding logic has an edge case where when we drop change,
leaving only a single blinded output, we recompute a bunch of blinding
data to handle the potential for us to have 0 inputs and 1 output to blind.
(BlindTransaction will fail in this case because it cannot make the
transaction balance with only one output to mess with.)
In this recomputation, we dropped more data than we meant to, causing us
to incorrectly blind an output.
First, this reverts commit ca2d72ae8b to reinstate
an assertion that was added in Bitcoin #22686. It did not compile because our
`change_and_fee` variable is a map rather than number; I changed it to use
`map_change_and_fee.at(policyAsset)` to match the equivalent change 2 lines down
from a5d97b363b (merge of Bitcoin #22008).
Then fix the following bugs:
1. Change the new test in rpc_fundrawtransaction.py to bump the -maxtxfee value,
which we'd otherwise exceed, failing the test and masking actual failures.
(This was just caused by the extreme fee settings of the test combined with
Elements' large transactions.)
2. Change the fee-output size estimation for `tx_noinputs_size` to be 46 rather
than 44 bytes; we forgot that even null surjection/rangeproofs need a 0 byte
when output witnesses are present. This mistake triggered the new assertion.
3. Correct the logic in which change outputs are sometimes dropped even when
they are the only blinded output in a transaction with blinded inputs. This
would cause the new test to fail with `bad-txn-inputs-ne-outputs`; I'm very
surprised that no existing tests hit this.
(I have an existing comment block in this code where I "promise" that I had
a good reason for doing something mysterious related to blinding. I was not
able to reverse-engineer my intention here, though I think it is related to
this, but since I couldn't understand it I just left this block intact and
worked around it.)
4. This then triggered the assertion again since the coin selection code
assumes that sufficiently-small change will always be dropped. If we prevent
this drop we will have under-funded the transaction.
To fix this we add Yet Another Flag `may_need_blinded_dummy` in which we add
extra weight to `tx_noinputs_size` in the case that we're doing a blinded tx
but have no blind destinations. We turn this off after coin selection if it
turns out that we don't have any blinded inputs, though ofc at that point
much of the damage/inefficiency has already been done..
5. Fix some constants in other functional tests which assumed precise fee
calculations; these precise values changed because of fixes (2) and (4).
There is one new FIXME, which is that the "dummy change" value will now be a
zero-valued OP_RETURN but we still put a full-size rangeproof and surjection
proof on it. There is some plausible privacy benefit to this but not much,
and wasting 5000+ bytes rather than the ~65 needed for an exact-value proof
is not worth it. We will fix this in the future when we overhaul the wallet
blinding logic.
Modifies the getnewblockhex json rpc call to accept an array of
commitments instead of a single commitment.
Backwards compatibility is maintained by first attempting to parse as a
string for a singular commitment.
A single 0x00 byte indicates a zero length field; we must skip parsing
that field otherwise the length will be expected to be read again for
the vector that is passed in to revieve the value.
This allows PSBT_ELEMENTS_GLOBAL_SCALAR to be parsed when it is
serialized according to the spec, i.e. both of the following cases
will correctly parse to the same representation:
$cli decodepsbt 'cHNldP8B+wQCAAAAAQIEAgAAAAEEAQABBQEAJ/wEcHNldAABAgMEBQYHCAkKCwwNDg8QERITFBUWFxgZGhscHR4fIAEAAA=='
and
$cli decodepsbt 'cHNldP8B+wQCAAAAAQIEAgAAAAEEAQABBQEAJ/wEcHNldAABAgMEBQYHCAkKCwwNDg8QERITFBUWFxgZGhscHR4fIAAA'
PSBT_ELEMENTS_GLOBAL_SCALAR is the only PSBT/PSET field that contains
key data but no value data and so is the only field that currently hits
this special case.
This facilitates the following workflow:
1) Obtain an updated psbt with in_witness_utxo and in_utxo_rangeproof
2) Get the blinding key from the input utxo address obtained from input
script pubkey without revealing master blinding key
3) Rewind the proof to obtain blinding factors and implement stateless
blinding
Conflicts were mostly obvious, except for those in CreateTransactionInternal.
(This function was moved from wallet.cpp to spend.cpp, and substantially
rewritten, between 0.21 and 22.0.) For those I manually applied the changes
from the diff, which wound up taking a slightly different form.
Also had to update the new test because the `addresses` field of the RPC
output was removed.
a67a2df330 pset: remove one more intermediate-zero check from the blinding logic (Andrew Poelstra)
9eb285c19d test: add test for confidential non-wallet-owned change (Andrew Poelstra)
185d473fe8 walletcreatefundedpsbt: add functional test for blinding edge cases (Andrew Poelstra)
533da12c2c wallet: make sure extra OP_RETURN output is blinded when called from fundraw (Andrew Poelstra)
b09b63bd1b pset: allow input blinding factors to sum to zero, or value to be 0 (Andrew Poelstra)
9afcb83baf wallet: correctly handle blinding of manually-set change addresses (Andrew Poelstra)
9813c3e74a wallet: fix "cannot unblind IsMine output" check in SignPSBT (Andrew Poelstra)
7103471fd5 walletcreatefundedpsbt: signal blinding data correctly to `FundTransaction` (Andrew Poelstra)
Pull request description:
Fixes#1049
Needs backport to 0.21 (and a new rc).
Although there are several bugs here, none affect the functionaries. There is a more thorough summary in the second-to-last commit message.
ACKs for top commit:
achow101:
ACK a67a2df330
Tree-SHA512: 25066c29f080e43cd00c5b33c60a986a8cb5bbf4ca01ceb3b4182c5b8f61979a1d6d946b8f28fa871ec90f44bdb6fc22014b5c11280cf081181db102cd588cdf
