# 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)
- [FAQ](#faq)
- [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
```

### Integration
- For GitHub action integration, use [slither-action](https://github.com/marketplace/actions/slither-action).
- To generate a Markdown report, use `slither [target] --checklist`.
- To generate a Markdown with GitHub source code highlighting, use `slither [target] --checklist --markdown-root https://github.com/ORG/REPO/blob/COMMIT/` (replace `ORG`, `REPO`, `COMMIT`)

Use [solc-select](https://github.com/crytic/solc-select) if your contracts require older versions of solc. For additional configuration, see the [usage](https://github.com/trailofbits/slither/wiki/Usage) documentation.

### 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 | `arbitrary-send-erc20` | [transferFrom uses arbitrary `from`](https://github.com/trailofbits/slither/wiki/Detector-Documentation#arbitrary-send-erc20) | High | High
3 | `array-by-reference` | [Modifying storage array by value](https://github.com/crytic/slither/wiki/Detector-Documentation#modifying-storage-array-by-value) | High | High
4 | `incorrect-shift` | [The order of parameters in a shift instruction is incorrect.](https://github.com/crytic/slither/wiki/Detector-Documentation#incorrect-shift-in-assembly) | High | High
5 | `multiple-constructors` | [Multiple constructor schemes](https://github.com/crytic/slither/wiki/Detector-Documentation#multiple-constructor-schemes) | High | High
6 | `name-reused` | [Contract's name reused](https://github.com/crytic/slither/wiki/Detector-Documentation#name-reused) | High | High
7 | `protected-vars` | [Detected unprotected variables](https://github.com/crytic/slither/wiki/Detector-Documentation#protected-variables) | High | High
8 | `public-mappings-nested` | [Public mappings with nested variables](https://github.com/crytic/slither/wiki/Detector-Documentation#public-mappings-with-nested-variables) | High | High
9 | `rtlo` | [Right-To-Left-Override control character is used](https://github.com/crytic/slither/wiki/Detector-Documentation#right-to-left-override-character) | High | High
10 | `shadowing-state` | [State variables shadowing](https://github.com/crytic/slither/wiki/Detector-Documentation#state-variable-shadowing) | High | High
11 | `suicidal` | [Functions allowing anyone to destruct the contract](https://github.com/crytic/slither/wiki/Detector-Documentation#suicidal) | High | High
12 | `uninitialized-state` | [Uninitialized state variables](https://github.com/crytic/slither/wiki/Detector-Documentation#uninitialized-state-variables) | High | High
13 | `uninitialized-storage` | [Uninitialized storage variables](https://github.com/crytic/slither/wiki/Detector-Documentation#uninitialized-storage-variables) | High | High
14 | `unprotected-upgrade` | [Unprotected upgradeable contract](https://github.com/crytic/slither/wiki/Detector-Documentation#unprotected-upgradeable-contract) | High | High
15 | `arbitrary-send-erc20-permit` | [transferFrom uses arbitrary from with permit](https://github.com/trailofbits/slither/wiki/Detector-Documentation#arbitrary-send-erc20-permit) | High | Medium
16 | `arbitrary-send-eth` | [Functions that send Ether to arbitrary destinations](https://github.com/crytic/slither/wiki/Detector-Documentation#functions-that-send-ether-to-arbitrary-destinations) | High | Medium
17 | `controlled-array-length` | [Tainted array length assignment](https://github.com/crytic/slither/wiki/Detector-Documentation#array-length-assignment) | High | Medium
18 | `controlled-delegatecall` | [Controlled delegatecall destination](https://github.com/crytic/slither/wiki/Detector-Documentation#controlled-delegatecall) | High | Medium
19 | `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
20 | `msg-value-loop` | [msg.value inside a loop](https://github.com/crytic/slither/wiki/Detector-Documentation/#msgvalue-inside-a-loop) | High | Medium
21 | `reentrancy-eth` | [Reentrancy vulnerabilities (theft of ethers)](https://github.com/crytic/slither/wiki/Detector-Documentation#reentrancy-vulnerabilities) | High | Medium
22 | `storage-array` | [Signed storage integer array compiler bug](https://github.com/crytic/slither/wiki/Detector-Documentation#storage-signed-integer-array) | High | Medium
23 | `unchecked-transfer` | [Unchecked tokens transfer](https://github.com/crytic/slither/wiki/Detector-Documentation#unchecked-transfer) | High | Medium
24 | `weak-prng` | [Weak PRNG](https://github.com/crytic/slither/wiki/Detector-Documentation#weak-PRNG) | High | Medium
25 | `domain-separator-collision` | [Detects ERC20 tokens that have a function whose signature collides with EIP-2612's DOMAIN_SEPARATOR()](https://github.com/crytic/slither/wiki/Detector-Documentation#domain-separator-collision) | Medium | High
26 | `enum-conversion` | [Detect dangerous enum conversion](https://github.com/crytic/slither/wiki/Detector-Documentation#dangerous-enum-conversion) | Medium | High
27 | `erc20-interface` | [Incorrect ERC20 interfaces](https://github.com/crytic/slither/wiki/Detector-Documentation#incorrect-erc20-interface) | Medium | High
28 | `erc721-interface` | [Incorrect ERC721 interfaces](https://github.com/crytic/slither/wiki/Detector-Documentation#incorrect-erc721-interface) | Medium | High
29 | `incorrect-equality` | [Dangerous strict equalities](https://github.com/crytic/slither/wiki/Detector-Documentation#dangerous-strict-equalities) | Medium | High
30 | `locked-ether` | [Contracts that lock ether](https://github.com/crytic/slither/wiki/Detector-Documentation#contracts-that-lock-ether) | Medium | High
31 | `mapping-deletion` | [Deletion on mapping containing a structure](https://github.com/crytic/slither/wiki/Detector-Documentation#deletion-on-mapping-containing-a-structure) | Medium | High
32 | `shadowing-abstract` | [State variables shadowing from abstract contracts](https://github.com/crytic/slither/wiki/Detector-Documentation#state-variable-shadowing-from-abstract-contracts) | Medium | High
33 | `tautology` | [Tautology or contradiction](https://github.com/crytic/slither/wiki/Detector-Documentation#tautology-or-contradiction) | Medium | High
34 | `write-after-write` | [Unused write](https://github.com/crytic/slither/wiki/Detector-Documentation#write-after-write) | Medium | High
35 | `boolean-cst` | [Misuse of Boolean constant](https://github.com/crytic/slither/wiki/Detector-Documentation#misuse-of-a-boolean-constant) | Medium | Medium
36 | `constant-function-asm` | [Constant functions using assembly code](https://github.com/crytic/slither/wiki/Detector-Documentation#constant-functions-using-assembly-code) | Medium | Medium
37 | `constant-function-state` | [Constant functions changing the state](https://github.com/crytic/slither/wiki/Detector-Documentation#constant-functions-changing-the-state) | Medium | Medium
38 | `divide-before-multiply` | [Imprecise arithmetic operations order](https://github.com/crytic/slither/wiki/Detector-Documentation#divide-before-multiply) | Medium | Medium
39 | `reentrancy-no-eth` | [Reentrancy vulnerabilities (no theft of ethers)](https://github.com/crytic/slither/wiki/Detector-Documentation#reentrancy-vulnerabilities-1) | Medium | Medium
40 | `reused-constructor` | [Reused base constructor](https://github.com/crytic/slither/wiki/Detector-Documentation#reused-base-constructors) | Medium | Medium
41 | `tx-origin` | [Dangerous usage of `tx.origin`](https://github.com/crytic/slither/wiki/Detector-Documentation#dangerous-usage-of-txorigin) | Medium | Medium
42 | `unchecked-lowlevel` | [Unchecked low-level calls](https://github.com/crytic/slither/wiki/Detector-Documentation#unchecked-low-level-calls) | Medium | Medium
43 | `unchecked-send` | [Unchecked send](https://github.com/crytic/slither/wiki/Detector-Documentation#unchecked-send) | Medium | Medium
44 | `uninitialized-local` | [Uninitialized local variables](https://github.com/crytic/slither/wiki/Detector-Documentation#uninitialized-local-variables) | Medium | Medium
45 | `unused-return` | [Unused return values](https://github.com/crytic/slither/wiki/Detector-Documentation#unused-return) | Medium | Medium
46 | `incorrect-modifier` | [Modifiers that can return the default value](https://github.com/crytic/slither/wiki/Detector-Documentation#incorrect-modifier) | Low | High
47 | `shadowing-builtin` | [Built-in symbol shadowing](https://github.com/crytic/slither/wiki/Detector-Documentation#builtin-symbol-shadowing) | Low | High
48 | `shadowing-local` | [Local variables shadowing](https://github.com/crytic/slither/wiki/Detector-Documentation#local-variable-shadowing) | Low | High
49 | `uninitialized-fptr-cst` | [Uninitialized function pointer calls in constructors](https://github.com/crytic/slither/wiki/Detector-Documentation#uninitialized-function-pointers-in-constructors) | Low | High
50 | `variable-scope` | [Local variables used prior their declaration](https://github.com/crytic/slither/wiki/Detector-Documentation#pre-declaration-usage-of-local-variables) | Low | High
51 | `void-cst` | [Constructor called not implemented](https://github.com/crytic/slither/wiki/Detector-Documentation#void-constructor) | Low | High
52 | `calls-loop` | [Multiple calls in a loop](https://github.com/crytic/slither/wiki/Detector-Documentation/#calls-inside-a-loop) | Low | Medium
53 | `events-access` | [Missing Events Access Control](https://github.com/crytic/slither/wiki/Detector-Documentation#missing-events-access-control) | Low | Medium
54 | `events-maths` | [Missing Events Arithmetic](https://github.com/crytic/slither/wiki/Detector-Documentation#missing-events-arithmetic) | Low | Medium
55 | `incorrect-unary` | [Dangerous unary expressions](https://github.com/crytic/slither/wiki/Detector-Documentation#dangerous-unary-expressions) | Low | Medium
56 | `missing-zero-check` | [Missing Zero Address Validation](https://github.com/crytic/slither/wiki/Detector-Documentation#missing-zero-address-validation) | Low | Medium
57 | `reentrancy-benign` | [Benign reentrancy vulnerabilities](https://github.com/crytic/slither/wiki/Detector-Documentation#reentrancy-vulnerabilities-2) | Low | Medium
58 | `reentrancy-events` | [Reentrancy vulnerabilities leading to out-of-order Events](https://github.com/crytic/slither/wiki/Detector-Documentation#reentrancy-vulnerabilities-3) | Low | Medium
59 | `timestamp` | [Dangerous usage of `block.timestamp`](https://github.com/crytic/slither/wiki/Detector-Documentation#block-timestamp) | Low | Medium
60 | `assembly` | [Assembly usage](https://github.com/crytic/slither/wiki/Detector-Documentation#assembly-usage) | Informational | High
61 | `assert-state-change` | [Assert state change](https://github.com/crytic/slither/wiki/Detector-Documentation#assert-state-change) | Informational | High
62 | `boolean-equal` | [Comparison to boolean constant](https://github.com/crytic/slither/wiki/Detector-Documentation#boolean-equality) | Informational | High
63 | `deprecated-standards` | [Deprecated Solidity Standards](https://github.com/crytic/slither/wiki/Detector-Documentation#deprecated-standards) | Informational | High
64 | `erc20-indexed` | [Un-indexed ERC20 event parameters](https://github.com/crytic/slither/wiki/Detector-Documentation#unindexed-erc20-event-parameters) | Informational | High
65 | `function-init-state` | [Function initializing state variables](https://github.com/crytic/slither/wiki/Detector-Documentation#function-initializing-state) | Informational | High
66 | `low-level-calls` | [Low level calls](https://github.com/crytic/slither/wiki/Detector-Documentation#low-level-calls) | Informational | High
67 | `missing-inheritance` | [Missing inheritance](https://github.com/crytic/slither/wiki/Detector-Documentation#missing-inheritance) | Informational | High
68 | `naming-convention` | [Conformity to Solidity naming conventions](https://github.com/crytic/slither/wiki/Detector-Documentation#conformance-to-solidity-naming-conventions) | Informational | High
69 | `pragma` | [If different pragma directives are used](https://github.com/crytic/slither/wiki/Detector-Documentation#different-pragma-directives-are-used) | Informational | High
70 | `redundant-statements` | [Redundant statements](https://github.com/crytic/slither/wiki/Detector-Documentation#redundant-statements) | Informational | High
71 | `solc-version` | [Incorrect Solidity version](https://github.com/crytic/slither/wiki/Detector-Documentation#incorrect-versions-of-solidity) | Informational | High
72 | `unimplemented-functions` | [Unimplemented functions](https://github.com/crytic/slither/wiki/Detector-Documentation#unimplemented-functions) | Informational | High
73 | `unused-state` | [Unused state variables](https://github.com/crytic/slither/wiki/Detector-Documentation#unused-state-variable) | Informational | High
74 | `costly-loop` | [Costly operations in a loop](https://github.com/crytic/slither/wiki/Detector-Documentation#costly-operations-inside-a-loop) | Informational | Medium
75 | `dead-code` | [Functions that are not used](https://github.com/crytic/slither/wiki/Detector-Documentation#dead-code) | Informational | Medium
76 | `reentrancy-unlimited-gas` | [Reentrancy vulnerabilities through send and transfer](https://github.com/crytic/slither/wiki/Detector-Documentation#reentrancy-vulnerabilities-4) | Informational | Medium
77 | `similar-names` | [Variable names are too similar](https://github.com/crytic/slither/wiki/Detector-Documentation#variable-names-too-similar) | Informational | Medium
78 | `too-many-digits` | [Conformance to numeric notation best practices](https://github.com/crytic/slither/wiki/Detector-Documentation#too-many-digits) | Informational | Medium
79 | `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
80 | `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)
- `when-not-paused`: [Print functions that do not use `whenNotPaused` modifier](https://github.com/trailofbits/slither/wiki/Printer-documentation#when-not-paused).

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)
- `slither-read-storage`: [Read storage values from contracts](./slither/tools/read_storage/README.md)

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 3.8+ 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.

## FAQ

How do I exclude mocks or tests?
- View our documentation on [path filtering](https://github.com/crytic/slither/wiki/Usage#path-filtering).

How do I fix "unknown file" or compilation issues?
- Because slither requires the solc AST, it must have all dependencies available.
If a contract has dependencies, `slither contract.sol` will fail.
Instead, use `slither .` in the parent directory of `contracts/` (you should see `contracts/` when you run `ls`).
If you have a `node_modules/` folder, it must be in the same directory as `contracts/`. To verify that this issue is related to slither,
run the compilation command for the framework you are using e.g `npx hardhat compile`. That must work successfully;
otherwise, slither's compilation engine, crytic-compile, cannot generate the AST.

## 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)
[SAILFISH: Vetting Smart Contract State-Inconsistency Bugs in Seconds](https://arxiv.org/pdf/2104.08638.pdf) | Rely on SlithIR to build a *storage dependency graph* | Priyanka Bose, Dipanjan Das, Yanju Chen, Yu Feng, Christopher Kruegel, and Giovanni Vigna | S&P 22
[SolType: Refinement Types for Arithmetic Overflow in Solidity](https://arxiv.org/abs/2110.00677) | Use Slither as frontend to build refinement type system | Bryan Tan, Benjamin Mariano, Shuvendu K. Lahiri, Isil Dillig, Yu Feng | POPL 22
[Do Not Rug on Me: Leveraging Machine Learning Techniques for Automated Scam Detection](https://www.mdpi.com/2227-7390/10/6/949) | Use Slither to extract tokens' features (mintable, pausable, ..) | Mazorra, Bruno, Victor Adan, and Vanesa Daza | Mathematics 10.6 (2022)

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/).