When estimating the maximum size of an input, we were assuming the
number of elements on the witness stack could be encode in a single
byte. This is a valid approximation for all the descriptors we support
(including P2WSH Miniscript ones), but may not hold anymore once we
support Miniscript within Taproot descriptors (since the max standard
witness stack size of 100 gets lifted).
It's a low-hanging fruit to account for it correctly, so just do it now.
In the wallet code, we are currently estimating the size of a signed
input by doing a dry run of the signing logic. This is unnecessary as
all outputs we are able to sign for can be represented by a descriptor,
and we can derive the size of a satisfaction ("signature") from the
descriptor itself directly.
In addition, this approach does not scale: getting the size of a
satisfaction through a dry run of the signing logic is only possible for
the most basic scripts.
This commit introduces the computation of the size of satisfaction per
descriptor. It's a bit intricate for 2 main reasons:
- We want to conserve the behaviour of the current dry-run logic used by
the wallet that sometimes assumes ECDSA signatures will be low-r,
sometimes not (when we don't create them).
- We need to account for the witness discount. A single descriptor may
sometimes benefit of it, sometimes not (for instance `pk()` if used as
top-level versus if used inside `wsh()`).
As we update the descriptor's db record every time that
the wallet is loaded (at `TopUp` time), if the spkm ID differs
from the one in db, the wallet will enter in an unrecoverable
corruption state, and no soft version will be able to open
it anymore.
Because we cannot change the past, to stay compatible between
releases, we need to always use the apostrophe version for the
spkm IDs.
This allows us to verify the descriptor ID on the descriptors
unit tests in different software versions without requiring to
use the entire DescriptorScriptPubKeyMan machinery.
Note:
The unit test changes are introduced after the bugfix commit
but this commit + the unit test commit can be cherry-picked
on top of the v25 branch to verify IDs correctness. IDs must
be the same for v25 and after the bugfix commit.
Instead of having a large blob of cache merging code in TopUp, refactor
this into DescriptorCache so that it can merge and provide a diff
(another DescriptorCache containing just the items that were added).
Then TopUp can just write everything that was in the diff.
Have Expand, ExpandFromCache, and ExpandHelper take additional DescriptorCache
parameters. These are then passed into PubkeyProvider::GetPubKey which
also takes them as arguments.
Reading and writing to the cache is pushed down into GetPubKey. The old cache where
pubkeys are serialized to a vector is completely removed and instead xpubs are being
cached in DescriptorCache.
Identified via -Wdocumentation, e.g.:
./rpc/rawtransaction_util.h:31:13: error: parameter 'prevTxs' not found in the function declaration [-Werror,-Wdocumentation]
* @param prevTxs Array of previous txns outputs that tx depends on but may not yet be in the block chain
^~~~~~~
./rpc/rawtransaction_util.h:31:13: note: did you mean 'prevTxsUnival'?
* @param prevTxs Array of previous txns outputs that tx depends on but may not yet be in the block chain
^~~~~~~
prevTxsUnival
netbase.cpp:766:11: error: parameter 'outProxyConnectionFailed[out]' not found in the function declaration [-Werror,-Wdocumentation]
* @param outProxyConnectionFailed[out] Whether or not the connection to the
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
netbase.cpp:766:11: note: did you mean 'outProxyConnectionFailed'?
* @param outProxyConnectionFailed[out] Whether or not the connection to the
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
outProxyConnectionFailed
2e68ffaf20 [doc] descriptor: explain GetPubKey() usage with cached public key (Sjors Provoost)
2290269759 scripted-diff: rename DescriptorImpl m_script_arg to m_subdescriptor_arg (Sjors Provoost)
Pull request description:
I found the name `m_script_arg` to be confusing while reviewing https://github.com/bitcoin/bitcoin/pull/14646#discussion_r240677238. @sipa let me know if `m_subdescriptor_arg` is completely wrong.
I also added an explanation of why we call `GetPubKey` when we don't ask it for a public key.
ACKs for top commit:
laanwj:
ACK 2e68ffaf20
Tree-SHA512: 06698e9a91cdda93c043a82732793f0ad3cd91daa2513565953e9fa048d5573322fb534e9d0ea9ab736e6366be5921e2b8699c4f4b3693edab48039aaae06f78
Moves all of the various SigningProviders out of sign.{cpp,h} and
keystore.{cpp,h}. As such, keystore.{cpp,h} is also removed.
Includes and the Makefile are updated to reflect this. Includes were largely
changed using:
git grep -l "keystore.h" | xargs sed -i -e 's;keystore.h;script/signingprovider.h;g'
