This commit fixes an off-by-one error which is only manifested by the
new behavior of OP_CODESEPARATOR within sig hashes triggered by the
segwit behavior. The current behavior within the Script VM
(txscript.Engine) is known to be fully correct to the extent that it has
been verified. However, once segwit activates a consensus divergence
would emerge due to *when* the program counter was incremented in the
previous code (pre-this-commit).
Currently (pre-segwit) when calculating the pre-image to a transaction
sighash for signature verification, *all* instances of OP_CODESEPARATOR
are removed from the subScript being signed before generating the final
sighash. SegWit has additional nerfed the behavior of OP_CODESEPARATOR
by no longer removing them (and starting after the last instance), but
instead simply starting the subScript to be directly *after* the last
instance of an OP_CODESEPARATOR within the pkScript.
Due to this new behavior, without this commit, an off-by-one error
(which only matters post-segwit), would cause txscript to generate an
incorrect subScript since the instance of OP_CODESEPARATOR would remain
as part of the subScript instead of being sliced off as the new behavior
dictates. The off-by-one error itself is manifested due to a slight
divergence in txscript.Engine’s logic compared to Bitcoin Core. In
Bitcoin Core script verification is as follows: first the next op-code
is fetched, then program counter is incremented, and finally the op-code
itself is executed. Before this commit, btcd flipped the order
of the last two steps, executing the op-code *before* the program
counter was incremented.
This commit fixes the post-segwit consensus divergence by incrementing
the program-counter *before* the next op-code is executed. It is
important to note that this divergence is only significant post-segwit,
meaning that txscript.Engine is still consensus compliant independent of
this commit.
This commit introduces a series of internal and external helper
functions which enable the txscript package to be aware of the new
standard script templates introduced as part of BIP0141. The two new
standard script templates recognized are pay-to-witness-key-hash
(P2WKH) and pay-to-witness-script-hash (P2WSH).
This commit implements most of BIP0143 by adding logic to implement the
new sighash calculation, signing, and additionally introduces the
HashCache optimization which eliminates the O(N^2) computational
complexity for the SIGHASH_ALL sighash type.
The HashCache struct is the equivalent to the existing SigCache struct,
but for caching the reusable midstate for transactions which are
spending segwitty outputs.
The btclog package has been changed to defining its own logging
interface (rather than seelog's) and provides a default implementation
for callers to use.
There are two primary advantages to the new logger implementation.
First, all log messages are created before the call returns. Compared
to seelog, this prevents data races when mutable variables are logged.
Second, the new logger does not implement any kind of artifical rate
limiting (what seelog refers to as "adaptive logging"). Log messages
are outputted as soon as possible and the application will appear to
perform much better when watching standard output.
Because log rotation is not a feature of the btclog logging
implementation, it is handled by the main package by importing a file
rotation package that provides an io.Reader interface for creating
output to a rotating file output. The rotator has been configured
with the same defaults that btcd previously used in the seelog config
(10MB file limits with maximum of 3 rolls) but now compresses newly
created roll files. Due to the high compressibility of log text, the
compressed files typically reduce to around 15-30% of the original
10MB file.
The github markdown interpreter has been changed such that it no longer
allows spaces in between the brackets and parenthesis of links and now
requires a newline in between anchors and other formatting. This
updates all of the markdown files accordingly.
While here, it also corrects a couple of inconsistencies in some of the
README.md files.
Now that glide is used for version management and a specific commit of
the upstream repository can be locked it is no longer necessary to
maintain a fork of the package specifically to keep a stable dependency.
While here, update the glide dependency for btcutil as well since it was
switched to use the upstream path as well.
This simplifies the code based on the recommendations of the gosimple
lint tool.
Also, it increases the deadline for the linters to run to 10 minutes and
reduces the number of threads that is uses. This is being done because
the Travis environment has become increasingly slower and it also seems
to be hampered by too many threads running concurrently.
ScriptVerifyNullFail defines that signatures must be empty if a
CHECKSIG or CHECKMULTISIG operation fails.
This commit also enables ScriptVerifyNullFail at the mempool policy
level.
This updates the data driven transaction script tests to use the most
recent format and test data as implemented by Core so the test data can
more easily be updated and help prove cross-compatibility correctness.
In particular, the new format combines the previously separate valid and
invalid test data files into a single file and adds a field for the
expected result. This is a nice improvement since it means tests can
now ensure script failures are due to a specific expected reason as
opposed to only generically detecting failure as the previous format
required.
The btcd script engine typically returns more fine grained errors than
the test data expects, so the test adapter handles this by allowing
expected errors in the test data to be mapped to multiple txscript
errors.
It should also be noted that the tests related to segwit have been
stripped from the data since the segwit PR has not landed in master yet,
however the test adapter does recognize the new ability for optional
segwit data to be supplied, though it will need to properly construct
the transaction using that data when the time comes.
This converts the majority of script errors from generic errors created
via errors.New and fmt.Errorf to use a concrete type that implements the
error interface with an error code and description.
This allows callers to programmatically detect the type of error via
type assertions and an error code while still allowing the errors to
provide more context.
For example, instead of just having an error the reads "disabled opcode"
as would happen prior to these changes when a disabled opcode is
encountered, the error will now read "attempt to execute disabled opcode
OP_FOO".
While it was previously possible to programmatically detect many errors
due to them being exported, they provided no additional context and
there were also various instances that were just returning errors
created on the spot which callers could not reliably detect without
resorting to looking at the actual error message, which is nearly always
bad practice.
Also, while here, export the MaxStackSize and MaxScriptSize constants
since they can be useful for consumers of the package and perform some
minor cleanup of some of the tests.
The CSV consensus rules dictate that the opcode fails when the
transaction version is not at least version 2, however that only applies
if the disable flag is not set in the sequence.
This is not an issue at the current time because we do not yet enforce
CSV at a consensus level, however, I noticed this discrepancy when doing
a thorough audit of the CSV paths due to the ongoing work to add full
consensus-enforced CSV support.
As a result, this must be merged prior to enabling consensus enforcement
for CSV or it would open up the potential for a hard fork.
This modifies the NewMsgTx function to accept the transaction version as
a parameter and updates all callers.
The reason for this change is so the transaction version can be bumped
in wire without breaking existing tests and to provide the caller with
the flexibility to create the specific transaction version they desire.
This modifies the recently-added NullDataScript function in several
ways in an effort to make them more consistent with the tests in the
rest of the code base and improve/correct the logic:
- Use the hexToBytes and mustParseShortForm functions
- Consistently format the test errors
- Replace the valid bool flag with an expected error and test against it
- Ensure the returned script type is the expected type in all cases
This adds a new function named NullDataScript to the txscript package that returns a provably-pruneable OP_RETURN script with the provided data. The function will return an error if the provided data is larger than the maximum allowed length for a nulldata script to be be considered standard.
Putting the test code in the same package makes it easier for forks
since they don't have to change the import paths as much and it also
gets rid of the need for internal_test.go to bridge.
Also, do some light cleanup on a few tests while here.
This corrects the isNullData standard transaction type test to work
properly with canonically-encoded data pushes. In particular, single
byte data pushes that are small integers (0-16) are converted to the
equivalent numeric opcodes when canonically encoded and the code failed
to detect them properly.
It also adds several tests to ensure that both canonical and
non-canonical nulldata scripts are recognized properly and modifies the
test failure print to include the script that failed.
This does not affect consensus since it is just a standardness check.
This exposes a new function on the ScriptBuilder type named AddOps that
allows multiple opcodes to be added via a single call and adds tests to
exercise the new function.
Finally, it updates a couple of places in the signing code that were
abusing the interface by setting its private script directly to use the
new public function instead.
This is mostly a backport of some of the same modifications made in
Decred along with a few additional things cleaned up. In particular,
this updates the code to make use of the new chainhash package.
Also, since this required API changes anyways and the hash algorithm is
no longer tied specifically to SHA, all other functions throughout the
code base which had "Sha" in their name have been changed to Hash so
they are not incorrectly implying the hash algorithm.
The following is an overview of the changes:
- Remove the wire.ShaHash type
- Update all references to wire.ShaHash to the new chainhash.Hash type
- Rename the following functions and update all references:
- wire.BlockHeader.BlockSha -> BlockHash
- wire.MsgBlock.BlockSha -> BlockHash
- wire.MsgBlock.TxShas -> TxHashes
- wire.MsgTx.TxSha -> TxHash
- blockchain.ShaHashToBig -> HashToBig
- peer.ShaFunc -> peer.HashFunc
- Rename all variables that included sha in their name to include hash
instead
- Update for function name changes in other dependent packages such as
btcutil
- Update copyright dates on all modified files
- Update glide.lock file to use the required version of btcutil
This changes the script template parsing function to use a pointer into
the constant global opcode array for parsed opcodes as opposed to making
a copy of the opcode entries which causes unnecessary allocations.
Profiling showed that after roughly 48 hours of operation, this
copy was the culprit of 207 million unnecessary allocations.
Profiles discovered that lookups into the signature cache included an
expensive comparison to the stored `sigInfo` struct. This lookup had the
potential to be more expensive than directly verifying the signature
itself!
In addition, evictions were rather expensive because they involved
reading from /dev/urandom, or equivalent, for each eviction once the
signature cache was full as well as potentially iterating over every
item in the cache in the worst-case.
To remedy this poor performance several changes have been made:
* Change the lookup key to the fixed sized 32-byte signature hash
* Perform a full equality check only if there is a cache hit which
results in a significant speed up for both insertions and existence
checks
* Override entries in the case of a colliding hash on insert Add an
* .IsEqual() method to the Signature and PublicKey types in the
btcec package to facilitate easy equivalence testing
* Allocate the signature cache map with the max number of entries in
order to avoid unnecessary map re-sizes/allocations
* Optimize evictions from the signature cache Delete the first entry
* seen which is safe from manipulation due to
the pre image resistance of the hash function
* Double the default maximum number of entries within the signature
cache due to the reduction in the size of a cache entry
* With this eviction scheme, removals are effectively O(1)
Fixes#575.
This modifies the conversion of the output index from the JSON-based
test data for valid and invalid transactions as well as the signature
hash type for signature hash tests to first convert to a signed int and
then to an unsigned int. This is necessary because the result of a
direct conversion of a float to an unsigned int is implementation
dependent and doesn't result in the expected value on all platforms.
Also, while here, change the function names in the error prints to match
the actual names.
Fixes#600.
500 tests with various transactions and scripts, verifying that
calcSignatureHash generates the expected hash in each case.
This requires changing SigHashType to uint32; that won't affect the
standard use-cases, but will make calcSignatureHash behave more like the
Core counterpart for non-standard SigHashType settings, like those in
some of these tests.
First, it removes the documentation section from all the README.md files
and instead puts a web-based godoc badge and link at the top with the
other badges. This is being done since the local godoc tool no longer
ships with Go by default, so the instructions no longer work without
first installing godoc. Due to this, pretty much everyone uses the
web-based godoc these days anyways. Anyone who has manually installed
godoc won't need instructions.
Second, it makes sure the ISC license badge is at the top with the other
badges and removes the textual reference in the overview section.
Finally, it's modifies the Installation section to Installation and
Updating and adds a '-u' to the 'go get' command since it works for both
and thus is simpler.
isMultiSig was not verifying the number of pubkeys specified matched
the number of pubkeys provided. This caused certain non-standard
scripts to be considered multisig scripts.
However, the script still would have failed during execution.
NOTE: This only affects whether or not the script is considered
standard and does NOT affect consensus.
Also, add a test for this check.
See https://github.com/bitcoin/bips/blob/master/bip-0065.mediawiki for
more information.
This commit mimics Bitcoin Core commit bc60b2b4b401f0adff5b8b9678903ff8feb5867b
and includes additional tests from Bitcoin Core commit
cb54d17355864fa08826d6511a0d7692b21ef2c9
We've already been generating lowS sigs for quite a while. This removes
the malleability vector.
This mimics Bitcoin Core commit 49dd5c629df0a08cf3b1ea8085c03312d1a81696
Introduce an ECDSA signature verification into btcd in order to
mitigate a certain DoS attack and as a performance optimization.
The benefits of SigCache are two fold. Firstly, usage of SigCache
mitigates a DoS attack wherein an attacker causes a victim's client to
hang due to worst-case behavior triggered while processing attacker
crafted invalid transactions. A detailed description of the mitigated
DoS attack can be found here: https://bitslog.wordpress.com/2013/01/23/fixed-bitcoin-vulnerability-explanation-why-the-signature-cache-is-a-dos-protection/
Secondly, usage of the SigCache introduces a signature verification
optimization which speeds up the validation of transactions within a
block, if they've already been seen and verified within the mempool.
The server itself manages the sigCache instance. The blockManager and
txMempool respectively now receive pointers to the created sigCache
instance. All read (sig triplet existence) operations on the sigCache
will not block unless a separate goroutine is adding an entry (writing)
to the sigCache. GetBlockTemplate generation now also utilizes the
sigCache in order to avoid unnecessarily double checking signatures
when generating a template after previously accepting a txn to the
mempool. Consequently, the CPU miner now also employs the same
optimization.
The maximum number of entries for the sigCache has been introduced as a
config parameter in order to allow users to configure the amount of
memory consumed by this new additional caching.
While current existing numeric opcodes are limited to 4 bytes, new
opcodes may need different limits.
This mimics Bitcoin Core commit 99088d60d8a7747c6d1a7fd5d8cd388be1b3e138
This commit modifies the DisasmString function to use a bytes buffer for
constructing the disassembled string instead of naive string
concatenation. This makes a huge difference when disassembling scripts
with large numbers of opcodes.
IsUnspendable takes a public key script and returns whether it is
spendable.
Additionally, hook this into the mempool isDust function, since
unspendable outputs can't be spent.
This mimics Bitcoin Core commit 0aad1f13b2430165062bf9436036c1222a8724da
This change moves IsFinalizedTransaction to txscript and also changes
the first argument to take a wire.MsgTx instead of btcutil.Tx. This
is needed for an upcoming diff in which txscript will require
IsFinalizedTransaction and we do not want to import the btcd/blockchain.
This commit contains fixes from the results of a thorough audit of
txscript to find any cases of script evaluation which doesn't match the
required consensus behavior. These conditions are fairly obscure and
highly unlikely to happen in any real scripts, but they could have
nevertheless been used by a clever attacker with malicious intent to
cause a fork.
Test cases which exercise these conditions have been added to the
reference tests and will contributed upstream to improve the quality for
the entire ecosystem.
Unlike OP_IF and OP_NOTIF which interpret the top stack item as a
number, OP_IFDUP interprets it as a boolean. This has important
consequences because numbers are imited to int32s while booleans can be
an arbitrary number of bytes.
The offending script was found and reported by Jonas Nick through the
use of fuzzing.
- Move reference tests to test package since they are intended to
exercise the engine as callers would
- Improve the short form script parsing to allow additional opcodes:
DATA_#, OP_#, FALSE, TRUE
- Make use of a function to decode hex strings rather than manually
defining byte slices
- Update the tests to make use of the short form script parsing logic
rather than manually defining byte slices
- Consistently replace all []byte{} and [][]byte{} with nil
- Define tests only used in a specific function inside that func
- Move invalid flag combination test to engine_test since that is what
it is testing
- Remove all redundant script tests in favor of the JSON-based tests in
the data directory.
- Move several functions from internal_test.go to the test files
associated with what the tests are checking
This commit moves all code related to standard scripts into a separate
file named standard.go as well as the associated tests into
standard_test.go. Since the code in address.go and address_test.go is
only related to standard scripts, it has been combined into the new
files and the old files deleted.
The intent here is to make it clear that the code in standard.go is not
related to consensus.
This commit implements a new type, named scriptNum, for handling all
numeric values used in scripts and converts the code over to make use of
it. This is being done for a few of reasons.
First, the consensus rules for handling numeric values in the scripts
require special handling with subtle semantics. By encapsulating those
details into a type specifically dedicated to that purpose, it
simplifies the code and generally helps prevent improper usage.
Second, the new type is quite a bit more efficient than big.Ints which
are designed to be arbitrarily large and thus involve a lot of heap
allocations and additional multi-precision bookkeeping. Because this
new type is based on an int64, it allows the numbers to be stack
allocated thereby eliminating a lot of GC and also eliminates the extra
multi-precision arithmetic bookkeeping.
The use of an int64 is possible because the consensus rules dictate that
when data is interpreted as a number, it is limited to an int32 even
though results outside of this range are allowed so long as they are not
interpreted as integers again themselves. Thus, the maximum possible
result comes from multiplying a max int32 by itself which safely fits
into an int64 and can then still appropriately provide the serialization
of the larger number as required by consensus.
Finally, it more closely resembles the implementation used by Bitcoin
Core and thus makes is easier to compare the behavior between the two
implementations.
This commit also includes a full suite of tests with 100% coverage of
the semantics of the new type.
This commit contains a lot of cleanup on the txscript code to make it
more consistent with the code throughout the rest of the project. It
doesn't change any operational logic.
The following is an overview of the changes:
- Add a significant number of comments throughout in order to better
explain what the code is doing
- Fix several comment typos
- Move a couple of constants only used by the engine to engine.go
- Move a variable only used by the engine to engine.go
- Fix a couple of format specifiers in the test prints
- Reorder functions so they're defined before/closer to use
- Make the code lint clean with the exception of the opcode definitions
- Remove all redundant opcode tests in favor of the JSON-based tests
in the data directory.
- Remove duplicate stack nip test
- Add new tests to data/script_invalid.json to exercise additional
negative error paths
- Remove old unneeded pubkey trace code from opcodeCheckSig
- Simplify and improve the disassembly print function
- Add new tests to directly test all individual opcode disassembly
- Add new tests to directly test opcode disabled function which does not
get invoked during ordinary execution
- Improve test coverage of opcode.go
This commit moves the opcode execution logic from the opcode type to the
engine type because execution of an opcode modifies the engine state
(primarily the main and alternate data stacks) as opposed to the state
of the opcode. Making the engine the receiver more clearly indicates
this fact.
This commit very slightly optimizes the cryptographic hashing performed
by the script opcodes by calling the hash sum routines directly (for
those that support it) rather than allocating a new generic hash.Hash
hasher instance for them.
This commit unexports the Stack type since it is only intended to be
used internally during script execution. Further, the engine exposes
the {G,S}etStack and {G,S}etAltStack functions which return the items as
a slice of byte slices ([][]byte) for caller access while stepping.
This commit improves the way the conditional execution stack is handled in
a few ways.
First, the current execution state is now pushed onto the end of the slice
rather than the front of it. This has been done because it results in
fewer allocations and is therefore more efficient.
Second, the need for allocating and setting an initial true in the
conditional stack has been eliminated. The vast majority of scripts don't
contain any conditionals, so there is no reason to allocate a slice when
it isn't needed.
Third, a new function has been added to the engine to determine if the
current conditional branch is executing named isBranchExecuting which
handles the fact the conditional execution stack can now be empty and
improves the readability of the code.
Finally, it removes a couple of TODOs which I have verified do not apply.
This commit exports a new map named OpcodeByName which can be used to
lookup an opcode value given a human-readable opcode name.
It also modifies the test function which does short form parsing to use
the new map instead of the internal array.
Closes#267.
This commit converts the opcode map to an array to improve performance.
Benchmark of executing a standard p2pk transaction:
New: BenchmarkExecute 2000 784349 ns/op
Old: BenchmarkExecute 2000 792600 ns/op
The time is dominated by the signature checking as expected, however there
is still an increase in speed.
This commit modifies the definition of the opcodes to their hex
counterparts rather than decimal since it is far more common to see
scripts in hex. This makes it easier when manually looking at script
dumps to correlate opcodes. However, since there are also cases where it
is useful to see the decimal value of the opcode, the decimal value has
been left as a comment. Obviously converting the numbers is trivial, but
it is handy when looking at the opcode definitions to already have it
there.
In addition, it syncs the opcodes with the latest Bitcoin Core internal
opcodes for completeness and modifies the tests accordingly.
Rather than storing a separate bool for whether or not each flag is set in
every script engine instance, store the flags and check if the relevant
flag is set from each specific location.
This reduces the memory needed by each script engine instance and means
future flags will not require new fields.
This commit renames the Script type to Engine to better reflect its
purpose. It also renames the NewScript function to NewEngine to match.
This is being done because name Script for the engine is confusing since
it implies it is an actual script rather than the execution environment
for the script. It also paves the way for eventually supplying a
ParsedScript type which will be less likely to be confused with the
execution environment.
While moving the code, some additional variable names and comments have
been updated to better match the style used throughout the rest of the
code base. In addition, an attempt has been made to use consistent naming
of the engine as 'vm' instead of using different variables names as it was
previously.
Finally, the relevant engine code has been moved into a new file named
engine.go and related tests moved to engine_test.go.
This commit separates the test functions and associated helper functions
which are used to execute the reference transaction and script tests from
Bitcoin Core into a separate file named reference_test.go.
Also, add a few comments and fix a couple of typos along the way.
This commit removes the unnecessary sigScript parameter from the
txscript.NewScript function. This has bothered me for a while because it
can and really should be obtained from the provided transaction and input
index. The way it was, the passed script could technically be different
than what is in the transaction. Obviously that would be an improper use
of the API, but it's safer and more convenient to simply pull it from the
provided transaction and index.
Also, since the function signature is changing anyways, make the input
index parameter come after the transaction which it references.
This commit removes the error returns from the BlockHeader.BlockSha,
MsgBlock.BlockSha, and MsgTx.TxSha functions since they can never fail and
end up causing a lot of unneeded error checking throughout the code base.
It also updates all call sites for the change.
The ScriptVerifyLowS flag defines that script signatures must
comply with the DER format as well as have an S value less than
or equal to the half order.
The ScriptVerifyCleanStack flag requires that only a single
stack element remains after evaluation and that when interpreted
as a bool, it must be true. This is BIP0062, rule 6.
This mimics Bitcoin Core commit b6e03cc59208305681745ad06f2056ffe6690597
This change increases the maximum allowed bytes allowed in pushed
data to be considered a nulldata transaction. This matches the current
value the reference implementation uses by default.
By exporting StandardVerifyFlags, clients can ensure they create
transactions that btcd will accept into its mempool.
This flag doesn't belong in txscript. It belongs in a
policy package. However, this is currently the least worse place.
The ScriptVerifyMinimalData enforces that all push operations use the
minimal data push required. This is part of BIP0062.
This commit mimics Bitcoin Core commit
698c6abb25c1fbbc7fa4ba46b60e9f17d97332ef
Remove ScriptCanonicalSignatures and use the new
ScriptVerifyDERSignatures flag. The ScriptVerifyDERSignatures
flag accomplishes the same functionality.
This commit adds two new verification flags to txscript named
ScriptVerifyStrictEncoding and ScriptVerifyDerSignatures.
The ScriptVerifyStrictEncoding flag enforces signature scripts
and public keys to follow the strict encoding requirements.
The ScriptVerifyDerSignatures flag enforces signature scripts
to follow the strict encoding requirements.
These flags mimic Bitcoin Core's SCRIPT_VERIFY_STRICTENC and
SCRIPT_VERIFY_DERSIG flags and brings the Bitcoin Core test scripts up
to date.
This commit corrects a case in the OP_CHECKMULTISIG handling where it was
possible to improperly validate a transaction that had a combination of
valid and malformed signatures.
It also adds a new test to ensure this case is properly handled and nukes
a superfluous comment.
Fixes#293.
This commit adds a new example to the txscript package that demonstrates
creating a new transaction which redeems funds and signing the referenced
transaction output the SignTxOutput function.
