1abbae65eb
71d1d13627ccd27319f347e2d8167c8fe8a433f4 test: add unit test for AvailableCoins (josibake) da03cb41a4ce15ebceee7fa4a4fdd2d3602fe284 test: functional test for new coin selection logic (josibake) 438e04845bf3302b7f459a50e88a1b772527f1e6 wallet: run coin selection by `OutputType` (josibake) 77b07072061c59f50c69be29fbcddf0d433e1077 refactor: use CoinsResult struct in SelectCoins (josibake) 2e67291ca3ab2d8f498fa910738ca655fde11c5e refactor: store by OutputType in CoinsResult (josibake) Pull request description: # Concept Following https://github.com/bitcoin/bitcoin/pull/23789, Bitcoin Core wallet will now generate a change address that matches the payment address type. This improves privacy by not revealing which of the outputs is the change at the time of the transaction in scenarios where the input address types differ from the payment address type. However, information about the change can be leaked in a later transaction. This proposal attempts to address that concern. ## Leaking information in a later transaction Consider the following scenario:  1. Alice has a wallet with bech32 type UTXOs and pays Bob, who gives her a P2SH address 2. Alice's wallet generates a P2SH change output, preserving her privacy in `txid: a` 3. Alice then pays Carol, who gives her a bech32 address 4. Alice's wallet combines the P2SH UTXO with a bech32 UTXO and `txid: b` has two bech32 outputs From a chain analysis perspective, it is reasonable to infer that the P2SH input in `txid: b` was the change from `txid: a`. To avoid leaking information in this scenario, Alice's wallet should avoid picking the P2SH output and instead fund the transaction with only bech32 Outputs. If the payment to Carol can be funded with just the P2SH output, it should be preferred over the bech32 outputs as this will convert the P2SH UTXO to bech32 UTXOs via the payment and change outputs of the new transaction. **TLDR;** Avoid mixing output types, spend non-default `OutputTypes` when it is economical to do so. # Approach `AvailableCoins` now populates a struct, which makes it easier to access coins by `OutputType`. Coin selection tries to find a funding solution by each output type and chooses the most economical by waste metric. If a solution can't be found without mixing, coin selection runs over the entire wallet, allowing mixing, which is the same as the current behavior. I've also added a functional test (`test/functional/wallet_avoid_mixing_output_types.py`) and unit test (`src/wallet/test/availablecoins_tests.cpp`. ACKs for top commit: achow101: re-ACK 71d1d13627ccd27319f347e2d8167c8fe8a433f4 aureleoules: ACK 71d1d13627ccd27319f347e2d8167c8fe8a433f4. Xekyo: reACK 71d1d13627ccd27319f347e2d8167c8fe8a433f4 via `git range-diff master 6530d19 71d1d13` LarryRuane: ACK 71d1d13627ccd27319f347e2d8167c8fe8a433f4 Tree-SHA512: 2e0716efdae5adf5479446fabc731ae81d595131d3b8bade98b64ba323d0e0c6d964a67f8c14c89c428998bda47993fa924f3cfca1529e2bd49eaa4e31b7e426
Bitcoin Core integration/staging tree
For an immediately usable, binary version of the Bitcoin Core software, see https://bitcoincore.org/en/download/.
What is Bitcoin Core?
Bitcoin Core connects to the Bitcoin peer-to-peer network to download and fully validate blocks and transactions. It also includes a wallet and graphical user interface, which can be optionally built.
Further information about Bitcoin Core is available in the doc folder.
License
Bitcoin Core is released under the terms of the MIT license. See COPYING for more information or see https://opensource.org/licenses/MIT.
Development Process
The master branch is regularly built (see doc/build-*.md for instructions) and tested, but it is not guaranteed to be
completely stable. Tags are created
regularly from release branches to indicate new official, stable release versions of Bitcoin Core.
The https://github.com/bitcoin-core/gui repository is used exclusively for the development of the GUI. Its master branch is identical in all monotree repositories. Release branches and tags do not exist, so please do not fork that repository unless it is for development reasons.
The contribution workflow is described in CONTRIBUTING.md and useful hints for developers can be found in doc/developer-notes.md.
Testing
Testing and code review is the bottleneck for development; we get more pull requests than we can review and test on short notice. Please be patient and help out by testing other people's pull requests, and remember this is a security-critical project where any mistake might cost people lots of money.
Automated Testing
Developers are strongly encouraged to write unit tests for new code, and to
submit new unit tests for old code. Unit tests can be compiled and run
(assuming they weren't disabled in configure) with: make check. Further details on running
and extending unit tests can be found in /src/test/README.md.
There are also regression and integration tests, written
in Python.
These tests can be run (if the test dependencies are installed) with: test/functional/test_runner.py
The CI (Continuous Integration) systems make sure that every pull request is built for Windows, Linux, and macOS, and that unit/sanity tests are run automatically.
Manual Quality Assurance (QA) Testing
Changes should be tested by somebody other than the developer who wrote the code. This is especially important for large or high-risk changes. It is useful to add a test plan to the pull request description if testing the changes is not straightforward.
Translations
Changes to translations as well as new translations can be submitted to Bitcoin Core's Transifex page.
Translations are periodically pulled from Transifex and merged into the git repository. See the translation process for details on how this works.
Important: We do not accept translation changes as GitHub pull requests because the next pull from Transifex would automatically overwrite them again.