NOTE: This software is still in the early stages of development. If you are confused, find some bugs, or just want some help, please file an issue or come talk to us at https://dapphub.chat/channel/k-framework.
Klab is a tool for generating and debugging proofs in the K Framework, tailored for the formal verification of ethereum smart contracts. It includes a succinct specification language for expressing the behavior of ethereum contracts, and an interactive debugger.
See dependency installation instructions here
This project uses the GNU version of getopt and time. OSX and gnu have a complicated relationship but you can run:
export PATH=/usr/local/opt/gnu-getopt/bin:/usr/local/opt/gnu-time/libexec/gnubin:/usr/local/opt/coreutils/libexec/gnubin:$PATHto make them get along.
Clone the repo and install the latest stable version v0.4.0 with
git clone --branch v0.4.0 https://github.com/dapphub/klab.git
cd klab
make depsOPTIONAL: klab has some optional Haskell components, for which the recommended installation method is nix. If you have nix, you can install the Haskell components with
make deps-haskellTo make klab available from the terminal, you can either just export the path to the klab executable in bin/, or use:
make linkThis installs symlinks globally at /usr/local/bin and /usr/local/libexec (will require sudo on Linux machines). You can also specify a custom directory for installation by doing:
PREFIX=/path/to/custom/prefix make linkThe file env will setup the environment for you if sourced from the root directory of the repo.
source ./envIt sets three environment variables:
PATH: include theklabexecutable.KLAB_EVMS_PATH: the EVM semantics to use.
OPTIONAL: If you want to use a different version of K than what the KEVM ships with, you can set:
KLAB_K_PATH: override implementation of K.
OPTIONAL: You might also want to add the K tool binaries in evm-semantics/.build/k/k-distribution/bin to your $PATH, if you didn't already have K installed.
OPTIONAL: You can also use nix-shell for a more deterministic environment experience. If you have nix installed, run nix-shell in this repo to start a deterministic shell environment.
To see how klab is used, we can explore the project in examples/SafeAdd:
cd examples/SafeAdd/The file config.json tells klab where to look for both the specification and the implementation of our contract. In this case, our specification lives in src/, and our implementation lives in dapp/.
Note that this example includes dapp/out/SafeAdd.sol.json compiled from the solidity source. With solc installed, you can compile it yourself:
solc --combined-json=abi,bin,bin-runtime,srcmap,srcmap-runtime,ast dapp/src/SafeAdd.sol > dapp/out/SafeAdd.sol.jsonOur goal is to prove that our implementation satisfies our specification. To do so, we'll start by building a set of K modules from our spec:
klab buildThis will generate success and failure reachability rules for each act of our specification. We can find the results in the out/specs directory.
Now we're ready to prove each case, for example:
klab prove --dump SafeAdd_add_failThe --dump flag outputs a log to out/data/<hash>.log, which will be needed later for interactive debugging. We can also do klab prove-all to prove all outstanding claims.
Once the proof is complete, we can explore the generated symbolic execution trace using:
klab debug <hash>klab comes with a set of pre-defined K rewrite rules, additional to the ones
defined in evm-semantics. They
are located in resources/rules.k.tmpl.
Toggle different views by pressing any of the following keys:
View Commands:
t- display the (somewhat) pretty K term.c- display current constraints.k- display<k>cell.b- display behavior tree.s- diaplay source code.e- display evm specific module.m- display memory cell.d- display debug cells (see toggling debug cells below).r- display applied K rule.z- display z3 feedback from attempted rule application.Up/Dn- scroll view up and down.
Navigation Commands:
n- step to next opcodep- step to previous opcodeShift+n- step to next k termShift+p- step to previous k termCtrl+n- step to next branch pointCtrl+p- step to previous branch point
Toggling Debug Cells:
The following commands are prefixed with : (and are typed at the bottom of the interface).
It's possible to toggle the debug cells view for specific cells, which prints out the JSON representation of the given cells.
Remember, you must turn on the debug cells view to see these (above).
:show ethereum.evm.callState.gas- show the contents of the<gas>cell in the debug cells view.:hide ethereum.evm.callStack.pc- hide the contents of the<pc>cell in the debug cells view.:omit gas pc- omit the contents of the<gas>and<pc>cells in the term view.:unomit pc programBytes- unomit the contents of the<pc>and<programBytes>cells in the term view.
klab build- builds a set of K reachability claims inout/specsbased on the spec, lemmas and source code as specified in the projectsconfig.json.klab prove <hash> [--dump]- executes a K reachability claim specified as a hash to the K prover. If the--dumpflag is present, the proof can be explored usingklab debug.klab prove-all- builds and executes all proof objects in the project directory.klab debug <hash>- opens up the cli proof explorer of a particular proof execution. See key bindings above.klab focus <hash>- focus on a hash, allowing you to leave out it as an argument to other commands.klab hash- prints the hash of the focused proofklab get-gas <hash>- Traverses the execution trace of a proof object to fetch its gas usage, put inout/gas/<hash>gas.k.klab solve-gas <hash>- Constructs the gas condition necessary for an execution to succeed.klab evm <hash>- Shows opcodes and source code side-by-side (useful for extracting pc values).klab status <hash>- Shows whether a proof has been run, and whether it was accepted or rejected.klab status-js <hash>- Shows the behaviour tree for an executed proof.klab fetch <url>- Fetches the execution trace of a proof object at the url, preparing it for local debugging.klab compress <hash>- compresses an execution trace so you can share it with a friend (or enemy).klab storage <contractName>- Guesses what the storage layout of a given contract isklab report- Generates a html report of the current project state inout/report/index.html.klab help- Generates this view
The config.json file is used to configure klab.
Here's an example:
{
"name": "k-dss",
"url": "https://github.com/dapphub/k-dss",
"src": {
"specification": "./src/dss.md",
"smt_prelude": "./src/prelude.smt2.md",
"rules": [
"./src/storage.k.md",
"./src/lemmas.k.md"
],
"dirty_rules": [
"./src/dirty_lemmas.k.md"
]
},
"implementations": {
"Vat": {
"src": "src/vat.sol"
},
"Vow": {
"src": "src/vow.sol"
},
},
"timeouts": {
"Vat_grab_pass_rough": "16h",
},
"memory" : {
"Vat_frob-diff-nonzero_fail_rough": "25G",
},
"dapp_root": "./dss",
"solc_output_path": "out/dapp.sol.json",
"host": "127.0.0.1:8080"
}By default, klab-prove sets a timeout of 1 day. This can be changed by passing
the --timeout flag a value of the format [0-9]+[dhms].
klab-prove-all defaults to a per-proof timeout of 200m. This can be changed
by setting timeouts to a different value in config.json, as shown above.
By default, both klab-prove and klab-prove-all run the JVM with a maximum
heap size of 10GB.
This can be changed by setting the K_OPTS environment variable to something
like --Xmx4G. Refer to the JVM
docs
for more information.
klab-prove-all also reads the config.json file, and the maximum heap size
can be changed with the memory key, as shown above.
In rough specs, the amount of gas available defaults to 3,000,000. This can be
changed using the gas header.
Once a pass_rough spec has been proven, the gas used for each execution path is combined into a single expression, which is the upper gas bound for the stronger pass spec.
There are automatic tab completions for zsh that can be installed by adding the following to your .zshrc:
# completions for klab
fpath=(~/dapphub/klab/resources/zsh $fpath)
autoload -U compinit
compinitYou might have problems due to an outdated npm, in that case try updating it with:
npm install npm@latest -g
npm install -g n
n stableWhat it looks like:
$ klab server
18.07.30 14-46-50: exec dfc688db4cc98b5de315bdfaa2512b84d14c3aaf3e58581ae728247097ff300d/run.sh
18.07.30 14-47-32: out Debugg: dfc688db4cc98b5de315bdfaa2512b84d14c3aaf3e58581ae728247097ff300d
fs.js:119
throw err;
^
Error: ENOENT: no such file or directory, open '/tmp/klab/b042c99687ae5018744dc96107032b291e4a91f1ab38a6286b2aff9a78056665/abstract-semantics.k'
at Object.openSync (fs.js:443:3)
at Object.readFileSync (fs.js:348:35)
at getFileExcerpt (/home/dev/src/klab/lib/rule.js:5:4)
at Object.parseRule (/home/dev/src/klab/lib/rule.js:21:16)
at Object.getblob (/home/dev/src/klab/lib/driver/dbDriver.js:49:19)
at Object.next (/home/dev/src/klab/lib/driver/dbDriver.js:113:56)
at Stream._n (/home/dev/src/klab/node_modules/xstream/index.js:797:18)
at /home/dev/src/klab/node_modules/@cycle/run/lib/cjs/index.js:57:61
at process._tickCallback (internal/process/next_tick.js:61:11)
[1] [dev@arch-ehildenb klab]% klab server
fs.js:119
throw err;
Notice how it's requesting abstract-semantics.k from proof-hash b042... but we're actually running proof-hash dfc6....
This is a problem with how K caches compiled definitions, and must be fixed upstream.
To fix this, run:
make clean && make depsThis will remove and recompile the KEVM semantics.
All contributions to this repository are licensed under AGPL-3.0. Authors:
- Denis Erfurt
- Martin Lundfall
- Everett Hildenbrandt
- Lev Livnev
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