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In order to prevent memory DoS, we must ensure that we don't accept a new
header into memory until we've performed anti-DoS checks, such as verifying
that the header is part of a sufficiently high work chain. This commit adds a
new argument to AcceptBlockHeader() so that we can ensure that all call-sites
which might cause a new header to be accepted into memory have to grapple with
the question of whether the header is safe to accept, or needs further
validation.
This patch also fixes two places where low-difficulty-headers could have been
processed without such validation (processing an unrequested block from the
network, and processing a compact block).
Credit to Niklas Gögge for noticing this issue, and thanks to Sjors Provoost
for test code.
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To be used in the next commit
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uninitialized variables
c4c5b9ca6e98cf44309af73edf5559940a04d00f consensus/params: set default values for BIP9Deployment (Anthony Towns)
Pull request description:
Adds default values for `vDeployments` in `consensus/params.h` so that undefined behaviour is avoided if a deployment is not initialized. Also adds a check in the unit tests to alert if this is happening, since even if it doesn't invoke undefined behaviour it's probably a mistake.
ACKs for top commit:
laanwj:
Code review ACK c4c5b9ca6e98cf44309af73edf5559940a04d00f
Tree-SHA512: 22d7ff86a817d9e9e67c47301fc3b7e9d5821c13565d7706711f113dea220eea29b413a7c8d029691009159cebc85a108d77cb52418734091c196bafb2b12423
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Add sanity asserts for return value of `CBlockIndex::GetAncestor()` where appropriate.
In validation.cpp `CheckSequenceLocks`, check the return value of `tip->GetAncestor(maxInputHeight)` stored into `lp->maxInputBlock`. If it ever returns `nullptr` because the ancestor isn't found, it's going to be a bad bug to keep going, since a `LockPoints` object with the `maxInputBlock` member set to `nullptr` signifies no relative lock time.
In the other places, the added asserts would prevent accidental dereferencing of a null pointer which is undefined behavior.
Co-Authored-By: Aurèle Oulès <aurele@oules.com>
Co-Authored-By: danra <danra@users.noreply.github.com>
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While chainparams should explicilty set values for each possible
entry in vDeployments, in the past that has been missed resulting
in potential undefined behaviour due to accessing unitinitialized
data. Reduce the severity of future bugs of that nature by providing
benign default values. Adds a unit test to alert if the default value
is not overwritten for the real chains (NEVER_ACTIVE/NEVER_ACTIVE rather
than NEVER_ACTIVE/NO_TIMEOUT).
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is set
cccc1e70b8a14430cc94143da97936a60d6c83d3 Enforce Taproot script flags whenever WITNESS is set (MarcoFalke)
fa422994116a7a053789304d56159760081479eb Remove nullptr check in GetBlockScriptFlags (MarcoFalke)
faadc606c7644f2934de390e261d9d65a81a7592 refactor: Pass const reference instead of pointer to GetBlockScriptFlags (MarcoFalke)
Pull request description:
Now that Taproot is active, it makes sense to enforce its rules on all blocks, even historic ones, regardless of the deployment status.
### Benefits:
(With "script flags" I mean "taproot script verification flags".)
* Script flags are known ahead for all blocks (even blocks not yet created) and do not change. This may benefit static analysis, code review, and development of new script features that build on Taproot.
* Any future bugs introduced in the deployment code won't have any effect on the script flags, as they are independent of deployment.
* Enforcing the taproot rules regardless of the deployment status makes testing easier because invalid blocks after activation are also invalid before activation. So there is no need to differentiate the two cases.
* It gives belt-and-suspenders protection against a practically expensive and theoretically impossible IBD reorg attack where the node is eclipsed. While `nMinimumChainWork` already protects against this, the cost for a few months worth of POW might be lowered until a major version release of Bitcoin Core reaches EOL. The needed work for the attack is the difference between `nMinimumChainWork` and the work at block 709632.
For reference, previously the same was done for P2SH and WITNESS in commit 0a8b7b4b33c9d78574627fc606267e2d8955cd1c.
### Implementation:
I found one block which fails verification with the flags applied, so I added a `TaprootException`, similar to the `BIP16Exception`.
For reference, the debug log:
```
ERROR: ConnectBlock(): CheckInputScripts on b10c007c60e14f9d087e0291d4d0c7869697c6681d979c6639dbd960792b4d41 failed with non-mandatory-script-verify-flag (Witness program was passed an empty witness)
BlockChecked: block hash=0000000000000000000f14c35b2d841e986ab5441de8c585d5ffe55ea1e395ad state=non-mandatory-script-verify-flag (Witness program was passed an empty witness)
InvalidChainFound: invalid block=0000000000000000000f14c35b2d841e986ab5441de8c585d5ffe55ea1e395ad height=692261 log2_work=92.988459 date=2021-07-23T08:24:20Z
InvalidChainFound: current best=0000000000000000000067b17a4c0ffd77c29941b15ad356ca8f980af137a25d height=692260 log2_work=92.988450 date=2021-07-23T07:47:31Z
ERROR: ConnectTip: ConnectBlock 0000000000000000000f14c35b2d841e986ab5441de8c585d5ffe55ea1e395ad failed, non-mandatory-script-verify-flag (Witness program was passed an empty witness)
```
Hint for testing, make sure to set `-noassumevalid`.
### Considerations
Obviously this change can lead to consensus splits on the network in light of massive reorgs. Currently the last block before Taproot activation, that is the last block without the Taproot script flags set, is only buried by a few days of POW. However, when and if this patch is included in the next major release, it will be buried by a few months of POW. BIP90 considerations apply when looking at reorgs this large.
ACKs for top commit:
Sjors:
tACK cccc1e70b8a14430cc94143da97936a60d6c83d3
achow101:
ACK cccc1e70b8a14430cc94143da97936a60d6c83d3
laanwj:
Code review ACK cccc1e70b8a14430cc94143da97936a60d6c83d3
ajtowns:
ACK cccc1e70b8a14430cc94143da97936a60d6c83d3 ; code review; wrote a "getblockscriptflags" rpc to quickly check that blocks just had bit 17 (taproot) added; review of earlier revisions had established non-exception blocks do validate with taproot rules enabled.
jamesob:
ACK cccc1e70b8a14430cc94143da97936a60d6c83d3 ([`jamesob/ackr/23536.1.MarcoFalke.enforce_taproot_script_f`](https://github.com/jamesob/bitcoin/tree/ackr/23536.1.MarcoFalke.enforce_taproot_script_f))
Tree-SHA512: 00044de68939caef6420ffd588c1291c041a8b397c80a3df1e3e3487fbeae1821d23975c51c95e44e774558db76f943b00b4e27cbd0213f64a9253116dc6edde
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-BEGIN VERIFY SCRIPT-
./contrib/devtools/copyright_header.py update ./
-END VERIFY SCRIPT-
Commits of previous years:
* 2020: fa0074e2d82928016a43ca408717154a1c70a4db
* 2019: aaaaad6ac95b402fe18d019d67897ced6b316ee0
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This just calls through to AcceptToMemoryPool() internally, and is currently unused.
Also add a new transaction validation failure reason TX_NO_MEMPOOL to
indicate that there is no mempool.
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The COIN constant is critical in understanding Bitcoin's supply, but what it represents isn't clear from the name of the constant. Adding a comment clarifies the meaning of the constant for future readers.
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Move amount.h to consensus/amount.h.
Renames, adds missing and removes uneeded includes.
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instead of signed int
fa621ededdfe31a200b77a8787de7e3d2e667aec refactor: Pass script verify flags as uint32_t (MarcoFalke)
Pull request description:
The flags are cast to unsigned in the interpreter anyway, so avoid the confusion (and fuzz crashes) by just passing them as unsigned from the beginning.
Also, the flags are often inverted bit-wise with the `~` operator, which also works on signed integers, but might cause confusion as the sign bit is flipped.
Fixes #22233
ACKs for top commit:
theStack:
Concept and code review ACK fa621ededdfe31a200b77a8787de7e3d2e667aec
kristapsk:
ACK fa621ededdfe31a200b77a8787de7e3d2e667aec
jonatack:
ACK fa621ededdfe31a200b77a8787de7e3d2e667aec
Tree-SHA512: ea0720f32f823fa7f075309978672aa39773c6019d12b6c1c9d611fc1983a76115b7fe2a28d50814673bb6415c311ccc05b99d6e871575fb6900faf75ed17769
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This is more visible than a comment hidden in an RPC helper function.
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e48826ad87b4f92261f7433e84f48dac9bd9e5c3 tests: remove ComputeBlockVersion shortcut from versionbits tests (Anthony Towns)
c5f36725e877d8eb492383844f8ef7535466b366 [refactor] Move ComputeBlockVersion into VersionBitsCache (Anthony Towns)
4a69b4dbe0d7f504811b67c399da7e6d11e4f805 [move-only] Move ComputeBlockVersion from validation to versionbits (Anthony Towns)
0cfd6c6a8f929d5567ac41f95c21548f115efee5 [refactor] versionbits: make VersionBitsCache a full class (Anthony Towns)
8ee3e0bed5bf2cd3c7a68ca6ba6c65f7b9a72cca [refactor] rpc/blockchain.cpp: SoftForkPushBack (Anthony Towns)
92f48f360da5f425428b761219301f509826bec4 deploymentinfo: Add DeploymentName() (Anthony Towns)
ea68b3a5729f5d240e968388c4f88acffeb27228 [move-only] Rename versionbitsinfo to deploymentinfo (Anthony Towns)
c64b2c6a0f79369624ae96b2e3d579d50aae4de6 scripted-diff: rename versionbitscache (Anthony Towns)
de55304f6e7a8b607e6b3fc7436de50910747b0c [refactor] Add versionbits deployments to deploymentstatus.h (Anthony Towns)
2b0d291da8f479739ff394dd92801da8c40b9f8e [refactor] Add deploymentstatus.h (Anthony Towns)
eccd736f3dc231ac0306ca763c3b72cf8247230a versionbits: Use dedicated lock instead of cs_main (Anthony Towns)
36a4ba0aaaa9b35185d7178994e36bc02cca9887 versionbits: correct doxygen comments (Anthony Towns)
Pull request description:
Introduces helper functions to make it easy to bury future deployments, along the lines of the suggestion from [11398](https://github.com/bitcoin/bitcoin/pull/11398#issuecomment-335599326) "I would prefer it if a buried deployment wouldn't require all code paths that check the BIP9 status to require changing".
This provides three functions: `DeploymentEnabled()` which tests if a deployment can ever be active, `DeploymentActiveAt()` which checks if a deployment should be enforced in the given block, and `DeploymentActiveAfter()` which checks if a deployment should be enforced in the block following the given block, and overloads all three to work both with buried deployments and versionbits deployments.
This adds a dedicated lock for the versionbits cache, which is acquired internally by the versionbits functions, rather than relying on `cs_main`. It also moves moves versionbitscache into deploymentstatus to avoid a circular dependency with validation.
ACKs for top commit:
jnewbery:
ACK e48826ad87b4f92261f7433e84f48dac9bd9e5c3
gruve-p:
ACK https://github.com/bitcoin/bitcoin/pull/19438/commits/e48826ad87b4f92261f7433e84f48dac9bd9e5c3
MarcoFalke:
re-ACK e48826ad87b4f92261f7433e84f48dac9bd9e5c3 🥈
Tree-SHA512: c846ba64436d36f8180046ad551d8b0d9e20509b9bc185aa2639055fc28803dd8ec2d6771ab337e80da0b40009ad959590d5772f84a0bf6199b65190d4155bed
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f9e37f33ce2d8b463a0bcbe7189c9bc5b36530b7 doc: IsFinalTx comment about nSequence & OP_CLTV (Yuval Kogman)
Pull request description:
It's somewhat surprising that a transaction's `nLockTime` field is ignored
when all `nSequence` fields are final, so this change aims to clarify this
behavior and cross reference relevant details of `OP_CHECKLOCKTIMEVERIFY`.
ACKs for top commit:
MarcoFalke:
ACK f9e37f33ce2d8b463a0bcbe7189c9bc5b36530b7
Tree-SHA512: 88460dacbe4b8115fb1948715f09b21d4f34ba1da9e88d52f0b774a969f845e9eddc5940e7fee66eacdd3062dc40d6d44c3f282b0e5144411fd47eb2320b44f5
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Adds support for versionbits deployments to DeploymentEnabled,
DeploymentActiveAfter and DeploymentActiveAt. Also moves versionbitscache
from validation to deploymentstatus.
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Provides DeploymentEnabled, DeploymentActiveAt, and DeploymentActiveAfter
helpers for checking the status of buried deployments. Can be overloaded
so the same syntax works for non-buried deployments, allowing future
soft forks to be changed from signalled to buried deployments without
having to touch the implementation code.
Replaces IsWitnessEnabled and IsScriptWitnessEnabled.
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They are cast to unsigned anyway when calling VerifyScript,
bitcoinconsensus_verify_script*, or CountWitnessSigOps.
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successful). Avoid UUM in fuzzing harness `coins_view`.
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It's somewhat surprising that a transaction's nLockTime field is ignored
when all nSequence fields are final, so this change aims to clarify this
behavior and cross reference relevant details of OP_CHECKLOCKTIMEVERIFY.
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Previously we used deployments that would timeout prior to Bitcoin's
invention, which allowed the deployment to still be activated in unit
tests. This switches those deployments to be truly never active.
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-BEGIN VERIFY SCRIPT-
./contrib/devtools/copyright_header.py update ./
-END VERIFY SCRIPT-
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Define a versionbits-based activation for the new consensus rules on regtest.
No activation or activation mechanism is defined for testnet or mainnet.
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Co-authored-by: Anthony Towns <aj@erisian.com.au>
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Our policy checks for non-standard inputs depend only on the non-witness
portion of a transaction: we look up the scriptPubKey of the input being
spent from our UTXO set (which is covered by the input txid), and the p2sh
checks only rely on the scriptSig portion of the input.
Consequently it's safe to add txids of transactions that fail these checks to
the reject filter, as the witness is irrelevant to the failure. This is helpful
for any situation where we might request the transaction again via txid (either
from txid-relay peers, or if we might fetch the transaction via txid due to
parent-fetching of orphans).
Further, in preparation for future witness versions being deployed on the
network, ensure that WITNESS_UNKNOWN transactions are rejected in
AreInputsStandard(), so that transactions spending v1 (or greater) witness
outputs will fall into this category of having their txid added to the reject
filter.
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0a4f1422cd1c20e12a05d7ff1a2ef1d5e7c654bb Further improve comments around recentRejects (Suhas Daftuar)
0e20cfedb704c1f76bb727e2009867d3d503a03d Disconnect peers sending wtxidrelay message after VERACK (Suhas Daftuar)
cacd85209e20fc0fd08f86eed23b6ef93484ffcf test: Use wtxid relay generally in functional tests (Fabian Jahr)
8d8099e97ab8af2126f6fbd223fbd82c52f2e85e test: Add tests for wtxid tx relay in segwit test (Fabian Jahr)
9a5392fdf67f1c5c90f52d3cdb3dea4f35d1609f test: Update test framework p2p protocol version to 70016 (Fabian Jahr)
dd78d1d641178b473ab1156b71a837b9e686792b Rename AddInventoryKnown() to AddKnownTx() (Suhas Daftuar)
4eb515574e1012bc8ea5dafc3042dcdf4c766f26 Make TX_WITNESS_STRIPPED its own rejection reason (Suhas Daftuar)
97141ca442daea8fc9c307cf81a02b38dcc28fd8 Delay getdata requests from peers using txid-based relay (Suhas Daftuar)
46d78d47dea345329ba094310eec56ab00a02ddc Add p2p message "wtxidrelay" (Suhas Daftuar)
2d282e0cba9761574b6b43d134ca95f3052d7fd2 ignore non-wtxidrelay compliant invs (Anthony Towns)
ac88e2eb619821ad7ae1d45d4b40be69051d3999 Add support for tx-relay via wtxid (Suhas Daftuar)
8e68fc246d09f1e6c6dfa8c676969d97c2eb4334 Add wtxids to recentRejects instead of txids (Suhas Daftuar)
144c38582042c3b9ec53bb97ba0644fc0114f8fb Add wtxids of confirmed transactions to bloom filter (Suhas Daftuar)
85c78d54af462996a0bca6cf97f91e1aa8778ae8 Add wtxid-index to orphan map (Suhas Daftuar)
08b39955ec7f84e835ab0b1366f0dd28dfd6ce03 Add a wtxid-index to mapRelay (Suhas Daftuar)
60f0acda713e7b9dc188aef54ef93981a93f4e44 Just pass a hash to AddInventoryKnown (Suhas Daftuar)
c7eb6b4f1fe5bd76388a023529977674534334a7 Add wtxid to mempool unbroadcast tracking (Amiti Uttarwar)
2b4b90aa8f0440deacefb5997d7bd1f9f5c591b3 Add a wtxid-index to the mempool (Suhas Daftuar)
Pull request description:
Using txids (a transaction's hash, without witness) for transaction relay is problematic, post-segwit -- if a peer gives us a segwit transaction that fails policy checks, it could be because the txid associated with the transaction is definitely unacceptable to our node (regardless of the witness), or it could be that the transaction was malleated and with a different witness, the txid could be accepted to our mempool.
We have a bloom filter of recently rejected transactions, whose purpose is to help us avoid redownloading and revalidating transactions that fail to be accepted, but because of this potential for witness malleability to interfere with relay of valid transactions, we do not use the filter for segwit transactions. This issue is discussed at some length in #8279. The effect of this is that whenever a segwit transaction that fails policy checks is relayed, a node would download that transaction from every peer announcing it, because it has no way presently to cache failure. Historically this hasn't been a big problem, but if/when policy for accepting segwit transactions were to change (eg taproot, or any other change), we could expect older nodes talking to newer nodes to be wasting bandwidth because of this.
As discussed in that issue, switching to wtxid-based relay solves this problem -- by using an identifier for a transaction that commits to all the data in our relay protocol, we can be certain if a transaction that a peer is announcing is one that we've already tried to process, or if it's something new. This PR introduces support for wtxid-based relay with peers that support it (and remains backwards compatible with peers that use txids for relay, of course).
Apart from code correctness, one issue to be aware of is that by downloading from old and new peers alike, we should expect there to be some bandwidth wasted, because sometimes we might download the same transaction via txid-relay as well as wtxid-relay. The last commit in this PR implements a heuristic I want to analyze, which is to just delay relay from txid-relay peers by 2 seconds, if we have at least 1 wtxid-based peer. I've just started running a couple nodes with this heuristic so I can measure how well it works, but I'm open to other ideas for minimizing that issue. In the long run, I think this will be essentially a non-issue, so I don't think it's too big a concern, we just need to bite the bullet and deal with it during upgrade.
Finally, this proposal would need a simple BIP describing the changes, which I haven't yet drafted. However, review and testing of this code in the interim would be welcome.
To do items:
- [x] Write BIP explaining the spec here (1 new p2p message for negotiating wtxid-based relay, along with a new INV type)
- [ ] Measure and evaluate a heuristic for minimizing how often a node downloads the same transaction twice, when connected to old and new nodes.
ACKs for top commit:
naumenkogs:
utACK 0a4f1422cd1c20e12a05d7ff1a2ef1d5e7c654bb
laanwj:
utACK 0a4f1422cd1c20e12a05d7ff1a2ef1d5e7c654bb
Tree-SHA512: d8eb8f0688cf0cbe9507bf738e143edab1f595551fdfeddc2b6734686ea26e7f156b6bfde38bad8bbbe8bec1857c7223e1687f8f018de7463dde8ecaa8f450df
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Previously, TX_WITNESS_MUTATED could be returned during transaction validation
for either transactions that had a witness that was non-standard, or for
transactions that had no witness but were invalid due to segwit validation
rules.
However, for txid/wtxid-relay considerations, net_processing distinguishes the
witness stripped case separately, because it affects whether a wtxid should be
able to be added to the reject filter. It is safe to add the wtxid of a
witness-mutated transaction to the filter (as that wtxid shouldn't collide with
the txid, and hence it wouldn't interfere with transaction relay from
txid-relay peers), but it is not safe to add the wtxid (== txid) of a
witness-stripped transaction to the filter, because that would interfere with
relay of another transaction with the same txid (but different wtxid) when
relaying from txid-relay peers.
Also updates the comment explaining this logic, and explaining that we can get
rid of this complexity once there's a sufficient deployment of wtxid-relaying
peers on the network.
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affects "prevHeights" parameter of the functions
- CalculateSequenceLocks()
- SequenceLocks()
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-BEGIN VERIFY SCRIPT-
./contrib/devtools/copyright_header.py update ./
-END VERIFY SCRIPT-
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Change comment from `The reason is that if the number of hashes in the list at a given time
is odd`, to ` The reason is that if the number of hashes in the list at a given level
is odd` (to be a bit more precise)
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This removes boilerplate code in the subclasses which otherwise only
differ by the result type.
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-BEGIN VERIFY SCRIPT-
./contrib/devtools/copyright_header.py update ./
-END VERIFY SCRIPT-
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Handle this failure in the same way as all other failures: call Invalid()
with the reasons for the failure.
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ValidationState::Invalid() takes a parameter `ret` which is returned to
the caller. All call sites set this to false. Remove the `ret` parameter
and just return false always.
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Minor style fixups and comment updates.
This is purely a style change. There is no change in behavior.
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Split CValidationState into TxValidationState and BlockValidationState
to store validation results for transactions and blocks respectively.
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