# Slither, the Solidity source analyzer
<img src="./logo.png" alt="Logo" width="500"/>

[![Build Status](https://img.shields.io/github/workflow/status/crytic/slither/CI/master)](https://github.com/crytic/slither/actions?query=workflow%3ACI)
[![Slack Status](https://empireslacking.herokuapp.com/badge.svg)](https://empireslacking.herokuapp.com)
[![PyPI version](https://badge.fury.io/py/slither-analyzer.svg)](https://badge.fury.io/py/slither-analyzer)

Slither is a Solidity static analysis framework written in Python 3. It runs a suite of vulnerability detectors, prints visual information about contract details, and provides an API to easily write custom analyses. Slither enables developers to find vulnerabilities, enhance their code comprehension, and quickly prototype custom analyses.

- [Features](#features)
- [Bugs and Optimizations Detection](#bugs-and-optimizations-detection)
- [Printers](#printers)
- [Tools](#tools)
- [How to Install](#how-to-install)
- [Getting Help](#getting-help)
- [Publications](#publications)

## Features

* Detects vulnerable Solidity code with low false positives (see the list of [trophies](./trophies.md))
* Identifies where the error condition occurs in the source code
* Easily integrates into continuous integration and Truffle builds
* Built-in 'printers' quickly report crucial contract information
* Detector API to write custom analyses in Python
* Ability to analyze contracts written with Solidity >= 0.4
* Intermediate representation ([SlithIR](https://github.com/trailofbits/slither/wiki/SlithIR)) enables simple, high-precision analyses
* Correctly parses 99.9% of all public Solidity code
* Average execution time of less than 1 second per contract


## Bugs and Optimizations Detection

Run Slither on a Truffle/Embark/Dapp/Etherlime/Hardhat application:
```bash
slither .
```

Run Slither on a single file:
```bash
slither tests/uninitialized.sol
```

For additional configuration, see the [usage](https://github.com/trailofbits/slither/wiki/Usage) documentation.

Use [solc-select](https://github.com/crytic/solc-select) if your contracts require older versions of solc.

### Detectors


Num | Detector | What it Detects | Impact | Confidence
--- | --- | --- | --- | ---
1 | `abiencoderv2-array` | [Storage abiencoderv2 array](https://github.com/crytic/slither/wiki/Detector-Documentation#storage-abiencoderv2-array) | High | High
2 | `array-by-reference` | [Modifying storage array by value](https://github.com/crytic/slither/wiki/Detector-Documentation#modifying-storage-array-by-value) | High | High
3 | `incorrect-shift` | [The order of parameters in a shift instruction is incorrect.](https://github.com/crytic/slither/wiki/Detector-Documentation#shift-parameter-mixup) | High | High
4 | `multiple-constructors` | [Multiple constructor schemes](https://github.com/crytic/slither/wiki/Detector-Documentation#multiple-constructor-schemes) | High | High
5 | `name-reused` | [Contract's name reused](https://github.com/crytic/slither/wiki/Detector-Documentation#name-reused) | High | High
6 | `public-mappings-nested` | [Public mappings with nested variables](https://github.com/crytic/slither/wiki/Detector-Documentation#public-mappings-with-nested-variables) | High | High
7 | `rtlo` | [Right-To-Left-Override control character is used](https://github.com/crytic/slither/wiki/Detector-Documentation#right-to-left-override-character) | High | High
8 | `shadowing-state` | [State variables shadowing](https://github.com/crytic/slither/wiki/Detector-Documentation#state-variable-shadowing) | High | High
9 | `suicidal` | [Functions allowing anyone to destruct the contract](https://github.com/crytic/slither/wiki/Detector-Documentation#suicidal) | High | High
10 | `uninitialized-state` | [Uninitialized state variables](https://github.com/crytic/slither/wiki/Detector-Documentation#uninitialized-state-variables) | High | High
11 | `uninitialized-storage` | [Uninitialized storage variables](https://github.com/crytic/slither/wiki/Detector-Documentation#uninitialized-storage-variables) | High | High
12 | `unprotected-upgrade` | [Unprotected upgradeable contract](https://github.com/crytic/slither/wiki/Detector-Documentation#unprotected-upgradeable-contract) | High | High
13 | `arbitrary-send` | [Functions that send Ether to arbitrary destinations](https://github.com/crytic/slither/wiki/Detector-Documentation#functions-that-send-ether-to-arbitrary-destinations) | High | Medium
14 | `controlled-array-length` | [Tainted array length assignment](https://github.com/crytic/slither/wiki/Detector-Documentation#array-length-assignment) | High | Medium
15 | `controlled-delegatecall` | [Controlled delegatecall destination](https://github.com/crytic/slither/wiki/Detector-Documentation#controlled-delegatecall) | High | Medium
16 | `reentrancy-eth` | [Reentrancy vulnerabilities (theft of ethers)](https://github.com/crytic/slither/wiki/Detector-Documentation#reentrancy-vulnerabilities) | High | Medium
17 | `storage-array` | [Signed storage integer array compiler bug](https://github.com/crytic/slither/wiki/Detector-Documentation#storage-signed-integer-array) | High | Medium
18 | `unchecked-transfer` | [Unchecked tokens transfer](https://github.com/crytic/slither/wiki/Detector-Documentation#unchecked-transfer) | High | Medium
19 | `weak-prng` | [Weak PRNG](https://github.com/crytic/slither/wiki/Detector-Documentation#weak-PRNG) | High | Medium
20 | `enum-conversion` | [Detect dangerous enum conversion](https://github.com/crytic/slither/wiki/Detector-Documentation#dangerous-enum-conversion) | Medium | High
21 | `erc20-interface` | [Incorrect ERC20 interfaces](https://github.com/crytic/slither/wiki/Detector-Documentation#incorrect-erc20-interface) | Medium | High
22 | `erc721-interface` | [Incorrect ERC721 interfaces](https://github.com/crytic/slither/wiki/Detector-Documentation#incorrect-erc721-interface) | Medium | High
23 | `incorrect-equality` | [Dangerous strict equalities](https://github.com/crytic/slither/wiki/Detector-Documentation#dangerous-strict-equalities) | Medium | High
24 | `locked-ether` | [Contracts that lock ether](https://github.com/crytic/slither/wiki/Detector-Documentation#contracts-that-lock-ether) | Medium | High
25 | `mapping-deletion` | [Deletion on mapping containing a structure](https://github.com/crytic/slither/wiki/Detector-Documentation#deletion-on-mapping-containing-a-structure) | Medium | High
26 | `shadowing-abstract` | [State variables shadowing from abstract contracts](https://github.com/crytic/slither/wiki/Detector-Documentation#state-variable-shadowing-from-abstract-contracts) | Medium | High
27 | `tautology` | [Tautology or contradiction](https://github.com/crytic/slither/wiki/Detector-Documentation#tautology-or-contradiction) | Medium | High
28 | `write-after-write` | [Unused write](https://github.com/crytic/slither/wiki/Detector-Documentation#write-after-write) | Medium | High
29 | `boolean-cst` | [Misuse of Boolean constant](https://github.com/crytic/slither/wiki/Detector-Documentation#misuse-of-a-boolean-constant) | Medium | Medium
30 | `constant-function-asm` | [Constant functions using assembly code](https://github.com/crytic/slither/wiki/Detector-Documentation#constant-functions-using-assembly-code) | Medium | Medium
31 | `constant-function-state` | [Constant functions changing the state](https://github.com/crytic/slither/wiki/Detector-Documentation#constant-functions-changing-the-state) | Medium | Medium
32 | `divide-before-multiply` | [Imprecise arithmetic operations order](https://github.com/crytic/slither/wiki/Detector-Documentation#divide-before-multiply) | Medium | Medium
33 | `reentrancy-no-eth` | [Reentrancy vulnerabilities (no theft of ethers)](https://github.com/crytic/slither/wiki/Detector-Documentation#reentrancy-vulnerabilities-1) | Medium | Medium
34 | `reused-constructor` | [Reused base constructor](https://github.com/crytic/slither/wiki/Detector-Documentation#reused-base-constructors) | Medium | Medium
35 | `tx-origin` | [Dangerous usage of `tx.origin`](https://github.com/crytic/slither/wiki/Detector-Documentation#dangerous-usage-of-txorigin) | Medium | Medium
36 | `unchecked-lowlevel` | [Unchecked low-level calls](https://github.com/crytic/slither/wiki/Detector-Documentation#unchecked-low-level-calls) | Medium | Medium
37 | `unchecked-send` | [Unchecked send](https://github.com/crytic/slither/wiki/Detector-Documentation#unchecked-send) | Medium | Medium
38 | `uninitialized-local` | [Uninitialized local variables](https://github.com/crytic/slither/wiki/Detector-Documentation#uninitialized-local-variables) | Medium | Medium
39 | `unused-return` | [Unused return values](https://github.com/crytic/slither/wiki/Detector-Documentation#unused-return) | Medium | Medium
40 | `incorrect-modifier` | [Modifiers that can return the default value](https://github.com/crytic/slither/wiki/Detector-Documentation#incorrect-modifier) | Low | High
41 | `shadowing-builtin` | [Built-in symbol shadowing](https://github.com/crytic/slither/wiki/Detector-Documentation#builtin-symbol-shadowing) | Low | High
42 | `shadowing-local` | [Local variables shadowing](https://github.com/crytic/slither/wiki/Detector-Documentation#local-variable-shadowing) | Low | High
43 | `uninitialized-fptr-cst` | [Uninitialized function pointer calls in constructors](https://github.com/crytic/slither/wiki/Detector-Documentation#uninitialized-function-pointers-in-constructors) | Low | High
44 | `variable-scope` | [Local variables used prior their declaration](https://github.com/crytic/slither/wiki/Detector-Documentation#pre-declaration-usage-of-local-variables) | Low | High
45 | `void-cst` | [Constructor called not implemented](https://github.com/crytic/slither/wiki/Detector-Documentation#void-constructor) | Low | High
46 | `calls-loop` | [Multiple calls in a loop](https://github.com/crytic/slither/wiki/Detector-Documentation/#calls-inside-a-loop) | Low | Medium
47 | `events-access` | [Missing Events Access Control](https://github.com/crytic/slither/wiki/Detector-Documentation#missing-events-access-control) | Low | Medium
48 | `events-maths` | [Missing Events Arithmetic](https://github.com/crytic/slither/wiki/Detector-Documentation#missing-events-arithmetic) | Low | Medium
49 | `incorrect-unary` | [Dangerous unary expressions](https://github.com/crytic/slither/wiki/Detector-Documentation#dangerous-unary-expressions) | Low | Medium
50 | `missing-zero-check` | [Missing Zero Address Validation](https://github.com/crytic/slither/wiki/Detector-Documentation#missing-zero-address-validation) | Low | Medium
51 | `reentrancy-benign` | [Benign reentrancy vulnerabilities](https://github.com/crytic/slither/wiki/Detector-Documentation#reentrancy-vulnerabilities-2) | Low | Medium
52 | `reentrancy-events` | [Reentrancy vulnerabilities leading to out-of-order Events](https://github.com/crytic/slither/wiki/Detector-Documentation#reentrancy-vulnerabilities-3) | Low | Medium
53 | `timestamp` | [Dangerous usage of `block.timestamp`](https://github.com/crytic/slither/wiki/Detector-Documentation#block-timestamp) | Low | Medium
54 | `assembly` | [Assembly usage](https://github.com/crytic/slither/wiki/Detector-Documentation#assembly-usage) | Informational | High
55 | `assert-state-change` | [Assert state change](https://github.com/crytic/slither/wiki/Detector-Documentation#assert-state-change) | Informational | High
56 | `boolean-equal` | [Comparison to boolean constant](https://github.com/crytic/slither/wiki/Detector-Documentation#boolean-equality) | Informational | High
57 | `deprecated-standards` | [Deprecated Solidity Standards](https://github.com/crytic/slither/wiki/Detector-Documentation#deprecated-standards) | Informational | High
58 | `erc20-indexed` | [Un-indexed ERC20 event parameters](https://github.com/crytic/slither/wiki/Detector-Documentation#unindexed-erc20-event-parameters) | Informational | High
59 | `function-init-state` | [Function initializing state variables](https://github.com/crytic/slither/wiki/Detector-Documentation#function-initializing-state-variables) | Informational | High
60 | `low-level-calls` | [Low level calls](https://github.com/crytic/slither/wiki/Detector-Documentation#low-level-calls) | Informational | High
61 | `missing-inheritance` | [Missing inheritance](https://github.com/crytic/slither/wiki/Detector-Documentation#missing-inheritance) | Informational | High
62 | `naming-convention` | [Conformity to Solidity naming conventions](https://github.com/crytic/slither/wiki/Detector-Documentation#conformance-to-solidity-naming-conventions) | Informational | High
63 | `pragma` | [If different pragma directives are used](https://github.com/crytic/slither/wiki/Detector-Documentation#different-pragma-directives-are-used) | Informational | High
64 | `redundant-statements` | [Redundant statements](https://github.com/crytic/slither/wiki/Detector-Documentation#redundant-statements) | Informational | High
65 | `solc-version` | [Incorrect Solidity version](https://github.com/crytic/slither/wiki/Detector-Documentation#incorrect-versions-of-solidity) | Informational | High
66 | `unimplemented-functions` | [Unimplemented functions](https://github.com/crytic/slither/wiki/Detector-Documentation#unimplemented-functions) | Informational | High
67 | `unused-state` | [Unused state variables](https://github.com/crytic/slither/wiki/Detector-Documentation#unused-state-variables) | Informational | High
68 | `costly-loop` | [Costly operations in a loop](https://github.com/crytic/slither/wiki/Detector-Documentation#costly-operations-inside-a-loop) | Informational | Medium
69 | `dead-code` | [Functions that are not used](https://github.com/crytic/slither/wiki/Detector-Documentation#dead-code) | Informational | Medium
70 | `reentrancy-unlimited-gas` | [Reentrancy vulnerabilities through send and transfer](https://github.com/crytic/slither/wiki/Detector-Documentation#reentrancy-vulnerabilities-4) | Informational | Medium
71 | `similar-names` | [Variable names are too similar](https://github.com/crytic/slither/wiki/Detector-Documentation#variable-names-are-too-similar) | Informational | Medium
72 | `too-many-digits` | [Conformance to numeric notation best practices](https://github.com/crytic/slither/wiki/Detector-Documentation#too-many-digits) | Informational | Medium
73 | `constable-states` | [State variables that could be declared constant](https://github.com/crytic/slither/wiki/Detector-Documentation#state-variables-that-could-be-declared-constant) | Optimization | High
74 | `external-function` | [Public function that could be declared external](https://github.com/crytic/slither/wiki/Detector-Documentation#public-function-that-could-be-declared-external) | Optimization | High

For more information, see
- The [Detector Documentation](https://github.com/crytic/slither/wiki/Detector-Documentation) for details on each detector
- The [Detection Selection](https://github.com/crytic/slither/wiki/Usage#detector-selection) to run only selected detectors. By default, all the detectors are run.
- The [Triage Mode](https://github.com/crytic/slither/wiki/Usage#triage-mode) to filter individual results

## Printers

### Quick Review Printers
- `human-summary`: [Print a human-readable summary of the contracts](https://github.com/trailofbits/slither/wiki/Printer-documentation#human-summary)
- `inheritance-graph`: [Export the inheritance graph of each contract to a dot file](https://github.com/trailofbits/slither/wiki/Printer-documentation#inheritance-graph)
- `contract-summary`: [Print a summary of the contracts](https://github.com/trailofbits/slither/wiki/Printer-documentation#contract-summary)

### In-Depth Review Printers
- `call-graph`: [Export the call-graph of the contracts to a dot file](https://github.com/trailofbits/slither/wiki/Printer-documentation#call-graph)
- `cfg`: [Export the CFG of each functions](https://github.com/trailofbits/slither/wiki/Printer-documentation#cfg)
- `function-summary`: [Print a summary of the functions](https://github.com/trailofbits/slither/wiki/Printer-documentation#function-summary)
- `vars-and-auth`: [Print the state variables written and the authorization of the functions](https://github.com/crytic/slither/wiki/Printer-documentation#variables-written-and-authorization)

To run a printer, use `--print` and a comma-separated list of printers.

See the [Printer documentation](https://github.com/crytic/slither/wiki/Printer-documentation) for the complete lists.

## Tools

- `slither-check-upgradeability`: [Review `delegatecall`-based upgradeability](https://github.com/crytic/slither/wiki/Upgradeability-Checks)
- `slither-prop`: [Automatic unit test and property generation](https://github.com/crytic/slither/wiki/Property-generation)
- `slither-flat`: [Flatten a codebase](https://github.com/crytic/slither/wiki/Contract-Flattening)
- `slither-check-erc`: [Check the ERC's conformance](https://github.com/crytic/slither/wiki/ERC-Conformance)
- `slither-format`: [Automatic patch generation](https://github.com/crytic/slither/wiki/Slither-format)

See the [Tool documentation](https://github.com/crytic/slither/wiki/Tool-Documentation) for additional tools.

[Contact us](https://www.trailofbits.com/contact/) to get help on building custom tools.

## How to install

Slither requires Python 3.6+ and [solc](https://github.com/ethereum/solidity/), the Solidity compiler.

### Using Pip

```bash
pip3 install slither-analyzer
```

### Using Git

```bash
git clone https://github.com/crytic/slither.git && cd slither
python3 setup.py install
```

We recommend using an Python virtual environment, as detailed in the [Developer Installation Instructions](https://github.com/trailofbits/slither/wiki/Developer-installation), if you prefer to install Slither via git.

### Using Docker

Use the [`eth-security-toolbox`](https://github.com/trailofbits/eth-security-toolbox/) docker image. It includes all of our security tools and every major version of Solidity in a single image. `/home/share` will be mounted to `/share`  in the container.

```bash
docker pull trailofbits/eth-security-toolbox
```

To share a directory in the container:

```bash
docker run -it -v /home/share:/share trailofbits/eth-security-toolbox
```

## Getting Help

Feel free to stop by our [Slack channel](https://empireslacking.herokuapp.com) (#ethereum) for help using or extending Slither.

* The [Printer documentation](https://github.com/trailofbits/slither/wiki/Printer-documentation) describes the information Slither is capable of visualizing for each contract.

* The [Detector documentation](https://github.com/trailofbits/slither/wiki/Adding-a-new-detector) describes how to write a new vulnerability analyses.

* The [API documentation](https://github.com/trailofbits/slither/wiki/API-examples) describes the methods and objects available for custom analyses.

* The [SlithIR documentation](https://github.com/trailofbits/slither/wiki/SlithIR) describes the SlithIR intermediate representation.

## License

Slither is licensed and distributed under the AGPLv3 license. [Contact us](mailto:opensource@trailofbits.com) if you're looking for an exception to the terms.


## Publications

### Trail of Bits publication
- [Slither: A Static Analysis Framework For Smart Contracts](https://arxiv.org/abs/1908.09878), Josselin Feist, Gustavo Grieco, Alex Groce - WETSEB '19

### External publications
- [ReJection: A AST-Based Reentrancy Vulnerability Detection Method](https://www.researchgate.net/publication/339354823_ReJection_A_AST-Based_Reentrancy_Vulnerability_Detection_Method), Rui Ma, Zefeng Jian, Guangyuan Chen, Ke Ma, Yujia Chen - CTCIS 19
- [MPro: Combining Static and Symbolic Analysis forScalable Testing of Smart Contract](https://arxiv.org/pdf/1911.00570.pdf), William Zhang, Sebastian Banescu, Leodardo Pasos, Steven Stewart, Vijay Ganesh - ISSRE 2019
- [ETHPLOIT: From Fuzzing to Efficient Exploit Generation against Smart Contracts](https://wcventure.github.io/FuzzingPaper/Paper/SANER20_ETHPLOIT.pdf), Qingzhao Zhang, Yizhuo Wang, Juanru Li, Siqi Ma - SANER 20
- [Verification of Ethereum Smart Contracts: A Model Checking Approach](http://www.ijmlc.org/vol10/977-AM0059.pdf), Tam Bang, Hoang H Nguyen, Dung Nguyen, Toan Trieu, Tho Quan - IJMLC 20
- [Smart Contract Repair](https://arxiv.org/pdf/1912.05823.pdf), Xiao Liang Yu, Omar Al-Bataineh, David Lo, Abhik Roychoudhury - TOSEM 20
- [Demystifying Loops in Smart Contracts](https://www.microsoft.com/en-us/research/uploads/prod/2020/08/loops_solidity__camera_ready-5f3fec3f15c69.pdf), Ben Mariano, Yanju Chen, Yu Feng, Shuvendu Lahiri, Isil Dillig - ASE 20
- [Trace-Based Dynamic Gas Estimation of Loops in Smart Contracts](https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=9268144), Chunmiao Li, Shijie Nie, Yang Cao, Yijun Yu, Zhenjiang Hu -  IEEE Open J. Comput. Soc. 1 (2020)

If you are using Slither on an academic work, consider applying to the [Crytic $10k Research Prize](https://blog.trailofbits.com/2019/11/13/announcing-the-crytic-10k-research-prize/).