slither/README.md

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

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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 GitHub action integration, see [slither-action](https://github.com/marketplace/actions/slither-action). 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 | `delegatecall-loop` | [Payable functions using `delegatecall` inside a loop](https://github.com/crytic/slither/wiki/Detector-Documentation/#payable-functions-using-delegatecall-inside-a-loop) | High | Medium
17 | `msg-value-loop` | [msg.value inside a loop](https://github.com/crytic/slither/wiki/Detector-Documentation/#msgvalue-inside-a-loop) | High | Medium
18 | `reentrancy-eth` | [Reentrancy vulnerabilities (theft of ethers)](https://github.com/crytic/slither/wiki/Detector-Documentation#reentrancy-vulnerabilities) | High | Medium
19 | `storage-array` | [Signed storage integer array compiler bug](https://github.com/crytic/slither/wiki/Detector-Documentation#storage-signed-integer-array) | High | Medium
20 | `unchecked-transfer` | [Unchecked tokens transfer](https://github.com/crytic/slither/wiki/Detector-Documentation#unchecked-transfer) | High | Medium
21 | `weak-prng` | [Weak PRNG](https://github.com/crytic/slither/wiki/Detector-Documentation#weak-PRNG) | High | Medium
22 | `enum-conversion` | [Detect dangerous enum conversion](https://github.com/crytic/slither/wiki/Detector-Documentation#dangerous-enum-conversion) | Medium | High
23 | `erc20-interface` | [Incorrect ERC20 interfaces](https://github.com/crytic/slither/wiki/Detector-Documentation#incorrect-erc20-interface) | Medium | High
24 | `erc721-interface` | [Incorrect ERC721 interfaces](https://github.com/crytic/slither/wiki/Detector-Documentation#incorrect-erc721-interface) | Medium | High
25 | `incorrect-equality` | [Dangerous strict equalities](https://github.com/crytic/slither/wiki/Detector-Documentation#dangerous-strict-equalities) | Medium | High
26 | `locked-ether` | [Contracts that lock ether](https://github.com/crytic/slither/wiki/Detector-Documentation#contracts-that-lock-ether) | Medium | High
27 | `mapping-deletion` | [Deletion on mapping containing a structure](https://github.com/crytic/slither/wiki/Detector-Documentation#deletion-on-mapping-containing-a-structure) | Medium | High
28 | `shadowing-abstract` | [State variables shadowing from abstract contracts](https://github.com/crytic/slither/wiki/Detector-Documentation#state-variable-shadowing-from-abstract-contracts) | Medium | High
29 | `tautology` | [Tautology or contradiction](https://github.com/crytic/slither/wiki/Detector-Documentation#tautology-or-contradiction) | Medium | High
30 | `write-after-write` | [Unused write](https://github.com/crytic/slither/wiki/Detector-Documentation#write-after-write) | Medium | High
31 | `boolean-cst` | [Misuse of Boolean constant](https://github.com/crytic/slither/wiki/Detector-Documentation#misuse-of-a-boolean-constant) | Medium | Medium
32 | `constant-function-asm` | [Constant functions using assembly code](https://github.com/crytic/slither/wiki/Detector-Documentation#constant-functions-using-assembly-code) | Medium | Medium
33 | `constant-function-state` | [Constant functions changing the state](https://github.com/crytic/slither/wiki/Detector-Documentation#constant-functions-changing-the-state) | Medium | Medium
34 | `divide-before-multiply` | [Imprecise arithmetic operations order](https://github.com/crytic/slither/wiki/Detector-Documentation#divide-before-multiply) | Medium | Medium
35 | `reentrancy-no-eth` | [Reentrancy vulnerabilities (no theft of ethers)](https://github.com/crytic/slither/wiki/Detector-Documentation#reentrancy-vulnerabilities-1) | Medium | Medium
36 | `reused-constructor` | [Reused base constructor](https://github.com/crytic/slither/wiki/Detector-Documentation#reused-base-constructors) | Medium | Medium
37 | `tx-origin` | [Dangerous usage of `tx.origin`](https://github.com/crytic/slither/wiki/Detector-Documentation#dangerous-usage-of-txorigin) | Medium | Medium
38 | `unchecked-lowlevel` | [Unchecked low-level calls](https://github.com/crytic/slither/wiki/Detector-Documentation#unchecked-low-level-calls) | Medium | Medium
39 | `unchecked-send` | [Unchecked send](https://github.com/crytic/slither/wiki/Detector-Documentation#unchecked-send) | Medium | Medium
40 | `uninitialized-local` | [Uninitialized local variables](https://github.com/crytic/slither/wiki/Detector-Documentation#uninitialized-local-variables) | Medium | Medium
41 | `unused-return` | [Unused return values](https://github.com/crytic/slither/wiki/Detector-Documentation#unused-return) | Medium | Medium
42 | `incorrect-modifier` | [Modifiers that can return the default value](https://github.com/crytic/slither/wiki/Detector-Documentation#incorrect-modifier) | Low | High
43 | `shadowing-builtin` | [Built-in symbol shadowing](https://github.com/crytic/slither/wiki/Detector-Documentation#builtin-symbol-shadowing) | Low | High
44 | `shadowing-local` | [Local variables shadowing](https://github.com/crytic/slither/wiki/Detector-Documentation#local-variable-shadowing) | Low | High
45 | `uninitialized-fptr-cst` | [Uninitialized function pointer calls in constructors](https://github.com/crytic/slither/wiki/Detector-Documentation#uninitialized-function-pointers-in-constructors) | Low | High
46 | `variable-scope` | [Local variables used prior their declaration](https://github.com/crytic/slither/wiki/Detector-Documentation#pre-declaration-usage-of-local-variables) | Low | High
47 | `void-cst` | [Constructor called not implemented](https://github.com/crytic/slither/wiki/Detector-Documentation#void-constructor) | Low | High
48 | `calls-loop` | [Multiple calls in a loop](https://github.com/crytic/slither/wiki/Detector-Documentation/#calls-inside-a-loop) | Low | Medium
49 | `events-access` | [Missing Events Access Control](https://github.com/crytic/slither/wiki/Detector-Documentation#missing-events-access-control) | Low | Medium
50 | `events-maths` | [Missing Events Arithmetic](https://github.com/crytic/slither/wiki/Detector-Documentation#missing-events-arithmetic) | Low | Medium
51 | `incorrect-unary` | [Dangerous unary expressions](https://github.com/crytic/slither/wiki/Detector-Documentation#dangerous-unary-expressions) | Low | Medium
52 | `missing-zero-check` | [Missing Zero Address Validation](https://github.com/crytic/slither/wiki/Detector-Documentation#missing-zero-address-validation) | Low | Medium
53 | `reentrancy-benign` | [Benign reentrancy vulnerabilities](https://github.com/crytic/slither/wiki/Detector-Documentation#reentrancy-vulnerabilities-2) | Low | Medium
54 | `reentrancy-events` | [Reentrancy vulnerabilities leading to out-of-order Events](https://github.com/crytic/slither/wiki/Detector-Documentation#reentrancy-vulnerabilities-3) | Low | Medium
55 | `timestamp` | [Dangerous usage of `block.timestamp`](https://github.com/crytic/slither/wiki/Detector-Documentation#block-timestamp) | Low | Medium
56 | `assembly` | [Assembly usage](https://github.com/crytic/slither/wiki/Detector-Documentation#assembly-usage) | Informational | High
57 | `assert-state-change` | [Assert state change](https://github.com/crytic/slither/wiki/Detector-Documentation#assert-state-change) | Informational | High
58 | `boolean-equal` | [Comparison to boolean constant](https://github.com/crytic/slither/wiki/Detector-Documentation#boolean-equality) | Informational | High
59 | `deprecated-standards` | [Deprecated Solidity Standards](https://github.com/crytic/slither/wiki/Detector-Documentation#deprecated-standards) | Informational | High
60 | `erc20-indexed` | [Un-indexed ERC20 event parameters](https://github.com/crytic/slither/wiki/Detector-Documentation#unindexed-erc20-event-parameters) | Informational | High
61 | `function-init-state` | [Function initializing state variables](https://github.com/crytic/slither/wiki/Detector-Documentation#function-initializing-state) | Informational | High
62 | `low-level-calls` | [Low level calls](https://github.com/crytic/slither/wiki/Detector-Documentation#low-level-calls) | Informational | High
63 | `missing-inheritance` | [Missing inheritance](https://github.com/crytic/slither/wiki/Detector-Documentation#missing-inheritance) | Informational | High
64 | `naming-convention` | [Conformity to Solidity naming conventions](https://github.com/crytic/slither/wiki/Detector-Documentation#conformance-to-solidity-naming-conventions) | Informational | High
65 | `pragma` | [If different pragma directives are used](https://github.com/crytic/slither/wiki/Detector-Documentation#different-pragma-directives-are-used) | Informational | High
66 | `redundant-statements` | [Redundant statements](https://github.com/crytic/slither/wiki/Detector-Documentation#redundant-statements) | Informational | High
67 | `solc-version` | [Incorrect Solidity version](https://github.com/crytic/slither/wiki/Detector-Documentation#incorrect-versions-of-solidity) | Informational | High
68 | `unimplemented-functions` | [Unimplemented functions](https://github.com/crytic/slither/wiki/Detector-Documentation#unimplemented-functions) | Informational | High
69 | `unused-state` | [Unused state variables](https://github.com/crytic/slither/wiki/Detector-Documentation#unused-state-variable) | Informational | High
70 | `costly-loop` | [Costly operations in a loop](https://github.com/crytic/slither/wiki/Detector-Documentation#costly-operations-inside-a-loop) | Informational | Medium
71 | `dead-code` | [Functions that are not used](https://github.com/crytic/slither/wiki/Detector-Documentation#dead-code) | Informational | Medium
72 | `reentrancy-unlimited-gas` | [Reentrancy vulnerabilities through send and transfer](https://github.com/crytic/slither/wiki/Detector-Documentation#reentrancy-vulnerabilities-4) | Informational | Medium
73 | `similar-names` | [Variable names are too similar](https://github.com/crytic/slither/wiki/Detector-Documentation#variable-names-are-too-similar) | Informational | Medium
74 | `too-many-digits` | [Conformance to numeric notation best practices](https://github.com/crytic/slither/wiki/Detector-Documentation#too-many-digits) | Informational | Medium
75 | `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
76 | `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 a 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/crytic/slither/wiki/Python-API) 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
Title | Usage | Authors | Venue
--- | --- | --- | ---
[ReJection: A AST-Based Reentrancy Vulnerability Detection Method](https://www.researchgate.net/publication/339354823_ReJection_A_AST-Based_Reentrancy_Vulnerability_Detection_Method) | AST-based analysis built on top of Slither | 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) | Leverage data dependency through Slither | 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) | Leverage data dependency through Slither | 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) | Symbolic execution built on top of Slither’s CFG | Tam Bang, Hoang H Nguyen, Dung Nguyen, Toan Trieu, Tho Quan | IJMLC 20
[Smart Contract Repair](https://arxiv.org/pdf/1912.05823.pdf) | Rely on Slither’s vulnerabilities detectors | 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) | Leverage data dependency through Slither | 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) | Use Slither’s CFG to detect loops | 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/).