0.54.2

[0.54.2] - 2024-12-12

Changed

• Improved printing of results. Should be more intuitive to understand what hevm found.
• More complete and precise array/mapping slot rewrite, along with a copySlice improvement
• Use a let expression in copySlice to decrease expression size
• The --debug flag now dumps the internal expressions as well
• hevm now uses the forge-std library's way of detecting failures, i.e. through
  reverting with a specific error code unless --assertion-type DSTest is passed
• Default max iterations is 5 now. --max-iters -1 now signals no bound. This change is to match other
  symbolic execution frameworks' default bound and to not go into an infinite loop by default when
  there could be other, interesting and reachable bugs in the code
• Update to GHC version 9.6.5
• Abstraction-refinement is no longer an option, it was never really useful and not well-tested

Added

• More POr and PAnd rules
• Array/Map slot decomposition can be turned off via a flag
• More PEq, PLEq, and PLT rules
• New label cheatcode.
• Updated Bitwuzla to newer version
• New cheatcodes startPrank() & stopPrank()
• ARM64 and x86_64 Mac along with Linux x86_64 static binaries for releases
• Tutorial for symbolic execution
• PAnd props are now recursively flattened
• Double negation in Prop are removed
• Updated forge to modern version, thereby fixing JSON parsing of new forge JSONs
• Fixed RPC fetching of contract data
• Symbolic ABI encoding for tuples, fuzzer for encoder
• Printing Addrs when running symbolic for counterexamples and reachable end states
• Improved symbolic execution tutorial
• More Mod, SMod, Div, and SDiv simplification rules
• Add freshAddresses field in VMOpts so that initial fresh address can be given as input
• Add documentation about limitations and workarounds
• More verbose error messages in case of symbolic arguments to opcode
• Tests to enforce that in Expr and Prop, constants are on the LHS whenever possible
• Support for MCOPY and TSTORE/TLOAD, i.e. EIP 5656 + 1153 + 4788
• All fuzz tests now run twice, once with expected SAT and once with expected UNSAT to check
  against incorrectly trivial UNSAT queries
• Allow --num-solvers option for equivalence checking, use num cores by default
• Preliminary support for multi-threaded Z3
• Skip over SMT generation issues due to e.g. CopySlice with symbolic arguments, and return
  partial results instead of erroring out
• Fix interpreter's MCOPY handling so that it doesn't error out on symbolic arguments
• More desciptive errors in case of a cheatcode issue
• Better and more pretty debug messages
• Many env* cheatcodes are now supported

Fixed

• vm.prank is now respected during calls to create
• concat is a 2-ary, not an n-ary function in SMT2LIB, declare-const does not exist in QF_AUFBV, replacing
  with declare-fun
• CVC5 needs --incremental flag to work properly in abstraction-refinement mode
• cli.hs now uses with-utf8 so no release binary will have locale issues anymore
• Took ideas for simplification rules from "Super-optimization of Smart Contracts" paper by Albert et al.
• Printing panic uint256 as hex, not as int
• Decomposition does not take place when entire states are compared, as that would necessitate
  a different approach.
• initial-storage option of hevm symbolic is respected
• caller option of hevm symbolic is now respected
• Thanks to the new simplification rules, we can now enable more conformance tests
• Multi-threaded running of Tracing.hs was not possible due to IO race. Fixed.
• Fixed multi-threading bug in symbolic interpretation
• Fixed simplification of concrete CopySlice with destination offset beyond destination size
• Fixed a bug in our SMT encoding of reading multiple consecutive bytes from concrete index
• Fixed bug in SMT encoding that caused empty and all-zero byte arrays to be considered equal
  and hence lead to false negatives through trivially UNSAT SMT expressions
• Respect --smt-timeout in equivalence checking
• Fixed the handling of returndata with an abstract size during transaction finalization
• Error handling for user-facing cli commands is much improved
• Fixed call signature generation for test cases
• Fixing prank so it doesn't override the sender address on lower call frames
• Fixed GitHub release action to upload release binaries

0.53.0

Changed

• Minimum distance requirements are now asserted for Keccak function calls. They assert that it's hard to generate two Keccak's that are less than 256 afar.
• Keccak concretization is now done only after all simplifications are performed. This helps with simplification pre-concretization
• Added an IllegalOverflow error in case the system tries to allocate a large amount of memory during
  abstract gas execution but concrete running. In these cases, the interpreter can out-of-heap
  as the only check is that the size allocated is less than $2**{64}$, but that is too large to fit in memory. Now,
  we check more stringently, and still return an IllegalOverflow
• Fixed --root option for the test subcommand

Added

• Optimized smt queries that significantly improve performance when dealing with solidity mappings and arrays
• Support for using Bitwuzla as a solver
• More efficient encoding for failure in ds-test style tests
• Symbolic tests now support statically sized arrays as parameters
• hevm test now has a num-solvers parameter that controls how many solver instances to spawn
• New solc-specific simplification rules that should make the final Props a lot more readable
• Prop is now correctly ordered, better BufLength and Max simplifications of Expr,
  and further solc-specific simplifications of Expr
• Simplify earlier and don't check reachability for things statically determined to be FALSE
• New concrete fuzzer that can be controlled via --num-cex-fuzz
• Partial support for dynamic jumps when the jump destination can be computed
  given already available information
• Added three forking cheatcodes: createFork, selectFork, and activeFork

Fixed

• Traces now correctly perform source mapping to display contract details
• Event traces now correctly display indexed arguments and argument names
• JSON reading of foundry JSONs was dependent on locale and did not work with many locales.
• CVC5 needs --incremental flag to work properly in abstraction-refinement mode

0.52.0

This is a major breaking release that removes several user facing features and includes non trivial breakage for library users. These changes mean the code is significantly simpler, more performant, and allow support for new features like fully symbolic addresses.

In addition to the changes below, this release includes significant work on performance optimization for symbolic execution.

Added

The major new user facing feature in this release is support for fully symbolic addresses (including fully symbolic addresses for deployed contracts). This allows tests to be writen that call vm.prank with a symbolic value, making some tests (e.g. access control, token transfer logic) much more comprehensive.

Some restrictions around reading balances from and transfering value between symbolic addresses are currently in place. Currently, if the address is symbolic, then you will only be able to read it's balance, or transfer value to/from it, if it is the address of a contract that is actually deployed. This is required to ensure soundness in the face of aliasing between symbolic addresses. We intend to lift this restriction in a future release.

Other

• Support for vm.deal
• Support for vm.assume (this is semantically identical to using require, but does simplify the
  process of porting exisitng fuzz tests to be symbolic)
• the check prefix now recognized for symbolic tests
• hevm test now takes a --number argument to specify which block should be used when making rpc queries

Changed

Revert Semantics in Solidity Tests

solidity tests no longer consider reverts to be a failure, and check only for the ds-test failed bit
or user defined assertion failures (i.e. Panic(0x01)). This makes writing tests much easier as users no longer have to consider trivial reverts (e.g. arithmetic overflow).

A positive (i.e. prove/check) test with no reachable assertion violations that does not have any successful branches will still be considered a failure.

Removed

hevm has been around for a while, and over time has accumulated many features. We decided to remove some of these features in the interest of focusing our attention, increasing our iteration speed and simplifying maintenance. The following user facing features have been removed from this release:

• The visual debugger has been removed
• All concrete ds-test executors have been removed (i.e. plain, fuzzer, invariant)
• Rpc caching and state serialization has been removed (i.e. all --cache / --state flags)
• The various DAPP_TEST variables are no longer observed
• The --initial-storage flag no longer accepts a concrete prestore (valid values are now Empty or Abstract)

Fixed

This release also includes many small bugfixes:

• CopySlice wraparound issue especially during CopyCallBytesToMemory
• Contracts deployed during symbolic execution are created with an empty storage (instead of abstract in previous versions)
• EVM.Solidity.toCode to include contractName in error string
• Better cex reconstruction in cases where branches do not refer to all input variables in calldata
• Correctly handle empty bytestring compiled contracts' JSON
• No more false positives when keccak is called with inputs of different sizes
• test now falls back to displaying an unecoded bytestring for calldata when the model returned by the solver has a different length the length of the arguments in the test signature.
• we now generate correct counterexamples for branches where only a subset of input variables are referenced by the path conditions
• vm.prank now works correctly when passed a symbolic address
• storage layout information will now be parsed from the output of forge build if it is available

API Changes

Reworked Storage Model / Symbolic Addresses

Adding symbolic addresses required some fairly significant changes to the way that we model storage. We introduced a new address type to Expr (Expr EAddr), that allows us to model fully symbolic addresses. Instead of modelling storage as a global symbolic 2D map (address -> word -> word) in
vm.env, each contract now has it's own symbolic 1D map (word -> word), that is stored in the vm.contracts mapping. vm.contracts is now keyed on Expr EAddr instead of Addr. Addresses that are keys to the vm.contracts mapping are asserted to be distinct in our smt encoding. This allows us to support symbolic addresses in a fully static manner (i.e. we do not currently need to make any extra smt queries when looking up storage for a symbolic address).

Mutable Memory & ST

We now use a mutable representation of memory if it is currently completely concrete. This is a significant performance improvement, and fixed a particulary egregious memory leak. It does entail the use of the ST monad, and introduces a new type parameter to the VM type that tags a given instance with it's thread local state. Library users will now need to either use the ST moand and runST or stToIO to compose and sequence vm executions.

GHC 9.4

Hevm is now built with ghc9.4. While earlier compiler versions may continue to work for now, they are no longer explicitly tested or supported.

Other

• Contract balances can now be fully symbolic
• Contract code can now be fully abstract. Calls into contracts with unknown code will fail with UnexpectedSymbolicArg.
• Run expression simplification on branch conditions
• SLoad/SStore simplifications based on assumptions regarding Keccak non-collision&preimage
• Improved Prop simplification
• CopySlice+WriteWord+ConcreteBuf now truncates ConcreteBuf in special cases
• Better simplification of Eq IR elements
• Run a toplevel constant folding reasoning system on branch conditions
• evalProp is renamed to simplifyProp for consistency
• Mem explosion in writeWord function was possible in case offset was close to 2^256. Fixed.
• BufLength was not simplified via bufLength function. Fixed.
• VMOpts no longer takes an initial store, and instead takes a baseState
  which can be either EmptyBase or AbstractBase. This controls whether
  storage should be inialized as empty or fully abstract. Regardless of this
  setting contracts that are deployed at runtime via a call to
  CREATE/CREATE2 have zero initialized storage.

0.51.3

Fixed

• Path joining on Windows
• Fixed overflow issue in stripWrites
• Automatic tests are now more reproducible

Changed

• Removed sha3Crack which has been deprecated for keccakEqs

Added

• Added flag -f debug to add debug flags to cabal/GHC

0.51.2

Fixed

• SMT encoding of Expr now has assertions for the range of environment values that are less than word size (256 bits).
• Trace now contains the cheat code calls
• More consistent error messages

Changed

• SMT2 scripts are now being reprocessed to put one sexpr per line. Having sepxrs that span across multiple lines trigers a bug in CVC5.
• Removing long-running tests so we can finish all unit tests in approx 10 minutes on a current-gen laptop CPU
• Added git revision to hevm version

Added

• execution traces are now shown for failed prove_ tests

0.51.1

Fixed

• hevm now gracefully handles missing out directories
• Constraints are correctly propogated to the final output expression during symbolic execution

Changed

• HEVM is now fully compliant with the Shanghai hard fork

0.51.0

Added

• hevm can now execute unit tests in foundry projects. Just run hevm test from the root of a foundry repo, and all unit tests will be executed (including prove tests).
• A new stack based loop detection heuristic
• Analysis of partial execution traces is now supported
• Stack traces are displayed for counterexamples from prove tests

Changed

• hevm dapp-test has been replaced with hevm test --project-type DappTools.
• hevm test no longer supports parsing solidity output in the combined json format.
• The default value for --ask-smt-iterations has been changed to 1
• The SMT solver is never queried for branch conditions that do not occur in a loop (as determined by the loop detection heuristic)

Fixed

• --max-iterations is respected in cases where path conditions have become inconsistent
• --max-iterations is now respected for loops with a concrete branch condition
• Fixed a bug where underflow was possible when transfering eth

0.50.5

Changed

• The --storage-model parameter has been replaced with --initial-storage
• The --smttimeout argument now expects a value in seconds not milliseconds
• The default smt timeout has been set to 5 minutes
• hevm symbolic now searches only for user defined assertions by default

Fixed

• The prank cheatcode now transfers value from the correct address
• Fixed an off-by-one error in EVM.Debug.srcMapCodePos

0.50.4

Fixed

• The --solvers cli option is now respected (previously we always used Z3)
• The equivalence command now fails with the correct status code when counterexamples are found
• The equivalence command now respects the given --sig argument
• Correct symbolic execution for the SGT opcode

Changed

• The equivalence command now pretty prints discovered counterexamples

Added

• Implemented a shrinking algorithm for counterexamples
• A new differential fuzzing test harness that compares the concrete semantics, as well as parts of the symbolic semantics against the geth evm implementation
• The hevm library can now be built on Windows systems.
• Support for function pointers in ABI
• equivalence can now be checked for fully or partially concrete calldata

release/0.50.3

Fixed

• hevm symbolic exits with status code 1 if counterexamples or timeouts are found

Added

• New cheatcode prank(address) that sets msg.sender to the specified address for the next call.
• Improved equivalence checker that avoids checking similar branches more than once.
• Improved simplification for arithmetic expressions
• Construction of storage counterexamples based on the model returned by the SMT solver.
• Static binaries for macos