This provides a means to pass in a PrecomputedTransactionData object to
the MutableTransactionSignatureCreator, allowing the prevout data to be
passed into the signature hashers. It is also more efficient.
725d7ae049 Use PrecomputedTransactionData in signet check (Pieter Wuille)
497718b467 Treat amount<0 also as missing data for P2WPKH/P2WSH (Pieter Wuille)
3820090bd6 Make all SignatureChecker explicit about missing data (Pieter Wuille)
b77b0cc507 Add MissingDataBehavior and make TransactionSignatureChecker handle it (Pieter Wuille)
Pull request description:
Currently we have 2 levels of potentially-missing data in the transaction signature hashes:
* P2WPKH/P2WSH hashes need the spent amount
* P2TR hashes need all spent outputs (amount + scriptPubKey)
Missing amounts are treated as -1 (thus leading to unexpected signature failures), while missing outputs in P2TR validation cause assertion failure. This is hard to extend for signing support, and also quite ugly in general.
In this PR, an explicit configuration option to {Mutable,}TransactionSignatureChecker is added (MissingDataBehavior enum class) to either select ASSERT_FAIL or FAIL. Validation code passes ASSERT_FAIL (as at validation time all data should always be passed, and anything else is a serious bug in the code), while signing code uses FAIL.
The existence of the ASSERT_FAIL option is really just an abundance of caution. Always using FAIL should be just fine, but if there were for some reason a code path in consensus code was introduced that misses certain data, I think we prefer as assertion failure over silently introducing a consensus change.
Potentially useful follow-ups (not for this PR, in my preference):
* Having an explicit script validation error code for missing data.
* Having a MissingDataBehavior::SUCCEED option as well, for use in script/sign.cpp DataFromTransaction (if a signature is present in a witness, and we don't have enough data to fully validate it, we should probably treat it as valid and not touch it).
ACKs for top commit:
sanket1729:
reACK 725d7ae049
Sjors:
ACK 725d7ae049
achow101:
re-ACK 725d7ae049
benthecarman:
ACK 725d7ae049
fjahr:
Code review ACK 725d7ae049
Tree-SHA512: d67dc51bae9ca7ef6eb9acccefd682529f397830f77d74cd305500a081ef55aede0e9fa380648c3a8dd4857aa7eeb1ab54fe808979d79db0784ac94ceb31b657
Historically lack of amount data has been treated as amount==-1. Change
this and treat it as missing data, as introduced in the previous commits.
To be minimally invasive, do this at SignatureHash() call sites rather
than inside SignatureHash() (which currently has no means or returning
a failure code).
Remove the implicit MissingDataBehavior::ASSERT_FAIL in the
*TransationSignatureChecker constructors, and instead specify
it explicit in all call sites:
* Test code uses ASSERT_FAIL
* Validation uses ASSERT_FAIL (through CachingTransactionSignatureChecker)
(including signet)
* libconsensus uses FAIL, matching the existing behavior of the
non-amount API (and the extended required data for taproot validation
is not available yet)
* Signing code uses FAIL
Introduces a DeferringSignatureChecker which simply takes a
BaseSignatureChecker and passes through everything.
SignatureExtractorChecker now subclasses DeferringSignatureChecker. This
allows for all BaseSignatureChecker functions to be implemented for
SignatureExtractorChecker, while allowing for future signature checkers
which opreate similarly to SignatureExtractorChecker.
fa650ca7f1 Use -Wswitch for TxoutType where possible (MarcoFalke)
fa59e0b5bd test: Add missing script_standard_Solver_success cases (MarcoFalke)
Pull request description:
This removes unused `default:` cases for all `switch` statements on `TxoutType` and adds the cases (`MULTISIG`, `NULL_DATA`, `NONSTANDARD`) to `ExtractDestination` for clarity.
Also, the compiler is now able to use `-Wswitch`.
ACKs for top commit:
practicalswift:
cr ACK fa650ca7f1: patch looks correct and `assert(false);` is better than UB :)
hebasto:
ACK fa650ca7f1, I have reviewed the code and it looks OK, I agree it can be merged.
Tree-SHA512: 282458b6523bd8923a0c0f5c423d1db2dce2a2d1b1d1dae455415c6fc995bb41ce82c1f9b0a1c0dcc6d874d171e04c30eca585f147582f52c7048c140358630a
This adds a `TxoutType::WITNESS_V1_TAPROOT` for P2TR outputs, and permits spending
them in standardness rules. No corresponding `CTxDestination` is added for it,
as that isn't needed until we want wallet integration. The taproot validation flags
are also enabled for mempool transactions, and standardness rules are added
(stack item size limit, no annexes).
In preparation for adding Schnorr versions of `CheckSig`, `VerifySignature`, and
`ComputeEntry`, give them an ECDSA specific name.
-BEGIN VERIFY SCRIPT-
sed -i 's/CheckSig(/CheckECDSASignature(/g' $(git grep -l CheckSig ./src)
sed -i 's/VerifySignature(/VerifyECDSASignature(/g' $(git grep -l VerifySignature ./src)
sed -i 's/ComputeEntry(/ComputeEntryECDSA(/g' $(git grep -l ComputeEntry ./src)
-END VERIFY SCRIPT-
-BEGIN VERIFY SCRIPT-
# General rename helper: $1 -> $2
rename_global() { sed -i "s/\<$1\>/$2/g" $(git grep -l "$1"); }
# Helper to rename TxoutType $1
rename_value() {
sed -i "s/ TX_$1,/ $1,/g" src/script/standard.h; # First strip the prefix in the definition (header)
rename_global TX_$1 "TxoutType::$1"; # Then replace globally
}
# Change the type globally to bring it in line with the style-guide
# (clsses are UpperCamelCase)
rename_global 'enum txnouttype' 'enum class TxoutType'
rename_global 'txnouttype' 'TxoutType'
# Now rename each enum value
rename_value 'NONSTANDARD'
rename_value 'PUBKEY'
rename_value 'PUBKEYHASH'
rename_value 'SCRIPTHASH'
rename_value 'MULTISIG'
rename_value 'NULL_DATA'
rename_value 'WITNESS_V0_KEYHASH'
rename_value 'WITNESS_V0_SCRIPTHASH'
rename_value 'WITNESS_UNKNOWN'
-END VERIFY SCRIPT-
Make sure that there are no errors set for an input after it is signed.
This is useful for when there are multiple ScriptPubKeyMans. Some may
fail to sign, but one may be able to sign, and after it does, we don't
want there to be any more errors there.
73aaf4ecf8 Make SignatureExtractorChecker private to its own file (Ben Woosley)
Pull request description:
~If we add a CTxIn constructor to SignatureData, then constructing the
SignatureData directly is no more verbose than calling DataFromTransaction,
and grants the caller additional flexibiliy in how to provide the CTxIn.~
A simple change to enhance encapsulation.
ACKs for top commit:
MarcoFalke:
utACK 73aaf4ecf8
laanwj:
ACK 73aaf4ecf8
Tree-SHA512: f7eafbce22b0e9917a8487e88d1f5a1061f2a0959ae1a097cbd9c8ea0d774edfb807da56813cb5fb26f6ca98499a0604a8ff024c198a7c8dc755164de66d972a
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'
This is not a pure refactor; additional functionality is added in
IsSegWitOutput which lets it recurse into P2SH when a
SigningProvider is provided that knows about the inner script.
When signing an input, figure out what was requested for but was unable
to be found and store it in a SignatureData.
Return this information in SignPSBTInput.
Move non-wallet PSBT code to src/psbt.{h,cpp}, and PSBT wallet code to
src/wallet/psbtwallet.{h,cpp}. This commit contains only code movement (and
adjustments to includes and Makefile.am.)
This commit makes the minimal changes necessary to fix compilation once CTransaction(const CMutableTransaction &tx) is made explicit. In each case an explicit call `CTransaction(...)` was added. Shouldn't affect behaviour or performance.
b81a186056 GetPubKey: make sigdata const (Gregory Sanders)
f7beb95a1f remove redundant KeyOriginInfo access, already done in CreateSig (Gregory Sanders)
Pull request description:
This redundancy is confusing as it looks like pubkeyhashes are special in some way based on where it's called.
Tree-SHA512: a980b7c774c6d69322945227a2b156489fb1991ebf57fe6f26096d5f8047f246a133debc241b05af67810f604b040079add3ab3d30d9e2928095905a2afe17eb
6b8d86ddb8 Require a public key to be retrieved when signing a P2PKH input (Andrew Chow)
Pull request description:
If we do not have the public key for a P2PKH input, we should not continue to attempt to sign for it.
This fixes a problem where a PSBT with a P2PKH output would include invalid BIP 32 derivation paths that are missing the public key.
Tree-SHA512: 850d5e74c06833da937d5bf0348bd134180be7167b6f9b9cecbf09f75e3543fbad60d0abbc0b9afdfa51ce165aa36168849f24a7c5abf1e75f37ce8f9a13d127
Refactor the process of PSBTInput signing to enforce the invariant that
a PSBTInput always has _either_ a witness_utxo or a non_witness_utxo,
never both.
This simplifies the logic of SignPSBTInput slightly, since it no longer
has to deal with the "both" case. When calling it, we now give it, in
order of preference: (1) whichever of the utxo fields was already
present in the PSBT we received, or (2) if neither, the
non_witness_utxo field, which is just a copy of the input transaction,
which we get from the wallet.
SignPSBTInput no longer has to remove one of the two fields; instead, it
will check if we have a witness signature, and if so, it will replace
the non_witness_utxo with the witness_utxo (which is smaller, as it is
just a copy of the output being spent.)
Add PSBTInput::IsSane checks in two more places, which checks for
both utxo fields being present; we will now give an RPC error early on
if we are supplied such a malformed PSBT to fill in.
Also add a check to FillPSBT, to avoid touching any input that is
already signed. (This is now redundant, since we should no longer
potentially harm an already-signed input, but it's harmless.)
fixes#14473
Remove redundant arguments to SignPSBTInput -- since it needs several
bits of the PartiallySignedTransaction, pass in a reference instead of
doing it piecemeal. This saves us having to pass in both a PSBTInput and
its index, as well as having to pass in the CTransaction. Also avoid
redundantly passing the sighash_type, which is contained in the
PSBTInput already.
862d159d63 Add test for conversion from non-witness to witness UTXO (Pieter Wuille)
f8c1714634 Convert non-witness UTXOs to witness if witness sig created (Andrew Chow)
Pull request description:
If a witness signature was created when a non-witness UTXO is used, convert the non-witness UTXO to a witness one.
Port of #14196 to master.
Tree-SHA512: 2235eeb008ffa48e821628032d689e4a83bff6c29b93fa050ab2ee492b0e67b3a30f29a680d4a0e574e05c3a2f9edf0005e161fbe25b7aef2acd034a2424e2f2
917353c8b0 Make SignPSBTInput operate on a private SignatureData object (Pieter Wuille)
cad5dd2368 Pass HD path data through SignatureData (Pieter Wuille)
03a99586a3 Implement key origin lookup in CWallet (Pieter Wuille)
3b01efa0d1 [MOVEONLY] Move ParseHDKeypath to utilstrencodings (Pieter Wuille)
81e1dd5ce1 Generalize PublicOnlySigningProvider into HidingSigningProvider (Pieter Wuille)
84f1f1bfdf Make SigningProvider expose key origin information (Pieter Wuille)
611ab307fb Introduce KeyOriginInfo for fingerprint + path (Pieter Wuille)
Pull request description:
This PR adds "key origin" (master fingeprint + key path) information to what is exposed from `SigningProvider`s, allowing this information to be used by the generic PSBT code instead of having the RPC pull it directly from the wallet.
This is also a preparation to having PSBT interact with output descriptors, which can then directly expose key origin information for the scripts they generate.
Tree-SHA512: c718382ba8ba2d6fc9a32c062bd4cff08b6f39b133838aa03115c39aeca0f654c7cc3ec72d87005bf8306e550824cd8eb9d60f0bd41784a3e22e17b2afcfe833
984d72ec65 Return the script type from Solver (Ben Woosley)
Pull request description:
Because false is synonymous with TX_NONSTANDARD, this conveys the same
information and makes the handling explicitly based on script type,
simplifying each call site.
Prior to this change it was common for the return value to be ignored, or for the
return value and TX_NONSTANDARD to be redundantly handled.
Tree-SHA512: 31864f856b8cb75f4b782d12678070e8b1cfe9665c6f57cfb25e7ac8bcea8a22f9a78d7c8cf0101c841f2a612400666fb91798bffe88de856e98b873703b0965
6ad0328f1c Don't assert(foo()) where foo has side effects (practicalswift)
Pull request description:
Don't `assert(foo())` where `foo` has side effects.
From `assert(3)`:
> If the macro `NDEBUG` is defined at the moment `<assert.h>` was last included, the macro `assert()` generates no code, and hence does nothing at all.
Bitcoin currently cannot be compiled without assertions, but we shouldn't rely on that.
Tree-SHA512: 28cff0c6d1c2fb612ca58c9c94142ed01c5cfd0a2fecb8e59cdb6c270374b215d952ed3491d921d84dc1b439fa49da4f0e75e080f6adcbc6b0e08be14e54c170
e306be7429 Use 72 byte dummy signatures when watching only inputs may be used (Andrew Chow)
48b1473c89 Use 71 byte signature for DUMMY_SIGNATURE_CREATOR (Andrew Chow)
18dfea0dd0 Always create 70 byte signatures with low R values (Andrew Chow)
Pull request description:
When creating signatures for transactions, always make one which has a 32 byte or smaller R and 32 byte or smaller S value. This results in signatures that are always less than 71 bytes (32 byte R + 32 byte S + 6 bytes DER + 1 byte sighash) with low R values. In most cases, the signature will be 71 bytes.
Because R is not mutable in the same way that S is, a low R value can only be found by trying different nonces. RFC 6979 for deterministic nonce generation has the option to specify additional entropy, so we simply use that and add a uin32_t counter which we increment in order to try different nonces. Nonces are sill deterministically generated as the nonce used will the be the first one where the counter results in a nonce that results in a low R value. Because different nonces need to be tried, time to produce a signature does increase. On average, it takes twice as long to make a signature as two signatures need to be created, on average, to find one with a low R.
Having a fixed size signature makes size calculations easier and also saves half a byte of transaction size, on average.
DUMMY_SIGNATURE_CREATOR has been modified to produce 71 byte dummy signatures instead of 72 byte signatures.
Tree-SHA512: 3cd791505126ce92da7c631856a97ba0b59e87d9c132feff6e0eef1dc47768e81fbb38bfbe970371bedf9714b7f61a13a5fe9f30f962c81734092a4d19a4ef33
With watching only inputs, we do not know how large the signatures
for those inputs will be as their signers may not have implemented
71 byte signatures. Thus we estimate their fees using the 72 byte
dummy signature to ensure that we pay enough fees.
This only effects fundrawtransaction when includeWatching is true.
3fc20632a3 qt: Set BLOCK_CHAIN_SIZE = 220 (DrahtBot)
2b6a2f4a28 Regenerate manpages (DrahtBot)
eb7daf4d60 Update copyright headers to 2018 (DrahtBot)
Pull request description:
Some trivial maintenance to avoid having to do it again after the 0.17 branch off.
(The scripts to do this are in `./contrib/`)
Tree-SHA512: 16b2af45e0351b1c691c5311d48025dc6828079e98c2aa2e600dc5910ee8aa01858ca6c356538150dc46fe14c8819ed8ec8e4ec9a0f682b9950dd41bc50518fa
fad231ad41 Fix merging of global unknown data in PSBTs (Andrew Chow)
41df035ee1 Check that PSBT keys are the correct length (Andrew Chow)
Pull request description:
This PR fixes a few bugs that were found and adds tests checking for these errors.
Specifically:
- Single byte keys are checked to actually be one byte.
- Unknown global data must be merged when combining two PSBTs.
Tree-SHA512: c0e7b4bc607d510cc005aaa7c0813ee58c5467ab7ce4adce485522dfeee92b1af3d29fe89df778b0ea812bb3827e085b30e04d4f4ebcefd8364d809573991332
Because false is synonymous with TX_NONSTANDARD, this conveys the same
information and makes the handling explicitly based on script type,
simplifying each call site.
Prior to this change it was common for the return value to be ignored,
or for the return value and TX_NONSTANDARD to be redundantly handled.
5617840392 Drop dead code from Stacks (Ben Woosley)
Pull request description:
Stacks is local to this file, and only used in DataFromTransaction, so
it's easy to confirm this code is unused.
Tree-SHA512: cc680c99f9b31cb56db70f453087d642f83906ce594c07a6bf3e61427cfbee41441495d440b240419ba3386582cf0670c0999b2f51e7fd56b00e0a0f3f618845
walletprocesspsbt takes a PSBT format transaction, updates the
PSBT with any inputs related to this wallet, signs, and finalizes
the transaction. There is also an option to not sign and just
update.
walletcreatefundedpsbt creates a PSBT from user provided data
in the same form as createrawtransaction. It also funds the transaction
and takes an options argument in the same form as fundrawtransaction.
The resulting PSBT is blank with no input or output data filled
in.
The SignPSBTInput function takes a PSBTInput, SignatureData, SigningProvider,
and other data necessary for signing. It fills the SignatureData with data from
the PSBTInput, retrieves the UTXO from the PSBTInput, signs and finalizes the
input if possible, and then extracts the results from the SignatureData and
puts them back into the PSBTInput.
Added methods which move data to/from SignaturData objects to
PSBTInput and PSBTOutput objects.
Added sanity checks for PSBTs as a whole which are done immediately
after deserialization.
Added Merge methods to merge a PSBT into another one.
Instead of using CombineSignatures to create the final scriptSig or
scriptWitness of an input, use ProduceSignature itself.
To allow for ProduceSignature to place signatures, pubkeys, and scripts
that it does not know about, we pass down the SignatureData to SignStep
which pulls out the information that it needs from the SignatureData.
In addition to having the scriptSig and scriptWitness, have SignatureData
also be able to store just the signatures (pubkeys mapped to sigs) and
scripts (script ids mapped to scripts).
Also have DataFromTransaction be able to extract signatures and scripts
from the scriptSig and scriptWitness of an input to put them in SignatureData.
Adds a new SignatureChecker which takes a SignatureData and puts pubkeys
and signatures into it when it successfully verifies a signature.
Adds a new field in SignatureData which stores whether the SignatureData
was complete. This allows us to also update the scriptSig and
scriptWitness to the final one when updating a SignatureData with another
one.
6aa33feadb Drop UpdateTransaction in favor of UpdateInput (Ben Woosley)
Pull request description:
Updating the input explicitly requires the caller to present a mutable
input, which more clearly communicates the effects and intent of the call
(and, often, the enclosing loop).
In most cases, this input is already immediately available and need not be
looked up.
Tree-SHA512: 8c7914a8b7ae975d8ad0e9d760e3c5da65776a5f79d060b8ffb6b3ff7a32235f71ad705f2185b368d9263742d7796bb562395d22b806d90e8502d8c496011e57
Templated version so that no copying of CMutableTransaction into a CTransaction is
necessary. This speeds up the test case transaction_tests/test_big_witness_transaction
from 7.9 seconds to 3.1 seconds on my machine.
Updating the input explicitly requires the caller to present a mutable
input, which more clearly communicates the effects and intent of the method.
In most cases, this input is already immediately available and need not be
looked up.
d40f06a Introduce interface for signing providers (Pieter Wuille)
Pull request description:
`CKeyStore` is a rich interface that provides many features, including knowledge of scripts and pubkeys for solving, private keys for signing, in addition to watch-only keys and scripts, and distinguishing lack of keys from them just being encrypted.
The signing logic in script/sign does not actually need most of these features. Here we introduce a simpler interface (`SigningProvider`) which *only* provides keys and scripts. This is actually sufficient for signing.
In addtion, we swap the dependency between keystore and script/sign (keystore now depends on script/script with `CKeyStore` deriving from `SigningProvider`, rather than `CKeyStore` being the interface that signing relies on).
This is a very early step towards the design in https://gist.github.com/sipa/125cfa1615946d0c3f3eec2ad7f250a2, separating the concern between deciding what outputs are ours and signing.
Tree-SHA512: d511b7b03eec0e513530db1d9ae5aacf6d0bfa1d3e1c03d06c5bde396bafb5824c4491b227d32bcda9288530caf49835da18e846ccf66538d6c0cc6ae27291c9
1f45e21 scripted-diff: Convert 11 enums into scoped enums (C++11) (practicalswift)
Pull request description:
Rationale (from Bjarne Stroustrup's ["C++11 FAQ"](http://www.stroustrup.com/C++11FAQ.html#enum)):
>
> The enum classes ("new enums", "strong enums") address three problems with traditional C++ enumerations:
>
> * conventional enums implicitly convert to int, causing errors when someone does not want an enumeration to act as an integer.
> * conventional enums export their enumerators to the surrounding scope, causing name clashes.
> * the underlying type of an enum cannot be specified, causing confusion, compatibility problems, and makes forward declaration impossible.
>
> The new enums are "enum class" because they combine aspects of traditional enumerations (names values) with aspects of classes (scoped members and absence of conversions).
Tree-SHA512: 9656e1cf4c3cabd4378c7a38d0c2eaf79e4a54d204a3c5762330840e55ee7e141e188a3efb2b4daf0ef3110bbaff80d8b9253abf2a9b015cdc4d60b49ac2b914
CKeyStore is a rich interface that provides many features, including knowledge
of scripts and pubkeys for solving, private keys for signing, in addition to
watch-only keys and scripts, and distinguishing lack of keys from them just
being encrypted.
The signing logic in script/sign does not actually need most of these features.
Here we introduce a simpler interface (SigningProvider) which *only* provides
keys and scripts. This is actually sufficient for signing.
In addtion, we swap the dependency between keystore and script/sign
(keystore now depends on script/script with CKeyStore deriving from
SigningProvider, rather than CKeyStore being the interface that signing
relies on).
9360f5032 Drop extra script variable in ProduceSignature (Russell Yanofsky)
Pull request description:
Was slightly confusing.
Tree-SHA512: 1d18f92c133772ffc8eb71826c8d778988839a14bcefc50f9c591111b0a5f81ebc12bca0f1ab25d5fdd02d3d50c2325c04cbfcbdcd18a7b80ca112d049c2327d
b224a47a1 Add address_types test (Pieter Wuille)
7ee54fd7c Support downgrading after recovered keypool witness keys (Pieter Wuille)
940a21932 SegWit wallet support (Pieter Wuille)
f37c64e47 Implicitly know about P2WPKH redeemscripts (Pieter Wuille)
57273f2b3 [test] Serialize CTransaction with witness by default (Pieter Wuille)
cf2c0b6f5 Support P2WPKH and P2SH-P2WPKH in dumpprivkey (Pieter Wuille)
37c03d3e0 Support P2WPKH addresses in create/addmultisig (Pieter Wuille)
3eaa003c8 Extend validateaddress information for P2SH-embedded witness (Pieter Wuille)
30a27dc5b Expose method to find key for a single-key destination (Pieter Wuille)
985c79552 Improve witness destination types and use them more (Pieter Wuille)
cbe197470 [refactor] GetAccount{PubKey,Address} -> GetAccountDestination (Pieter Wuille)
0c8ea6380 Abstract out IsSolvable from Witnessifier (Pieter Wuille)
Pull request description:
This implements a minimum viable implementation of SegWit wallet support, based on top of #11389, and includes part of the functionality from #11089.
Two new configuration options are added:
* `-addresstype`, with options `legacy`, `p2sh`, and `bech32`. It controls what kind of addresses are produced by `getnewaddress`, `getaccountaddress`, and `createmultisigaddress`.
* `-changetype`, with the same options, and by default equal to `-addresstype`, that controls what kind of change is used.
All wallet private and public keys can be used for any type of address. Support for address types dependent on different derivation paths will need a major overhaul of how our internal detection of outputs work. I expect that that will happen for a next major version.
The above also applies to imported keys, as having a distinction there but not for normal operations is a disaster for testing, and probably for comprehension of users. This has some ugly effects, like needing to associate the provided label to `importprivkey` with each style address for the corresponding key.
To deal with witness outputs requiring a corresponding redeemscript in wallet, three approaches are used:
* All SegWit addresses created through `getnewaddress` or multisig RPCs explicitly get their redeemscripts added to the wallet file. This means that downgrading after creating a witness address will work, as long as the wallet file is up to date.
* All SegWit keys in the wallet get an _implicit_ redeemscript added, without it being written to the file. This means recovery of an old backup will work, as long as you use new software.
* All keypool keys that are seen used in transactions explicitly get their redeemscripts added to the wallet files. This means that downgrading after recovering from a backup that includes a witness address will work.
These approaches correspond to solutions 3a, 1a, and 5a respectively from https://gist.github.com/sipa/125cfa1615946d0c3f3eec2ad7f250a2. As argued there, there is no full solution for dealing with the case where you both downgrade and restore a backup, so that's also not implemented.
`dumpwallet`, `importwallet`, `importmulti`, `signmessage` and `verifymessage` don't work with SegWit addresses yet. They're remaining TODOs, for this PR or a follow-up. Because of that, several tests unexpectedly run with `-addresstype=legacy` for now.
Tree-SHA512: d425dbe517c0422061ab8dacdc3a6ae47da071450932ed992c79559d922dff7b2574a31a8c94feccd3761c1dffb6422c50055e6dca8e3cf94a169bc95e39e959
5a9b508 [trivial] Add end of namespace comments (practicalswift)
Tree-SHA512: 92b0fcae4d1d3f4da9e97569ae84ef2d6e09625a5815cd0e5f0eb6dd2ecba9852fa85c184c5ae9de5117050330ce995e9867b451fa8cd5512169025990541a2b
