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Caracal

Caracal is a static analyzer tool over the SIERRA representation for Starknet smart contracts.

Features

  • Detectors to detect vulnerable Cairo code
  • Printers to report information
  • Taint analysis
  • Data flow analysis framework
  • Easy to run in Scarb projects

Installation

Precompiled binaries

Precompiled binaries are available on our releases page. If you are using Cairo compiler 1.x.x uses the binary v0.1.x otherwise if you are using the Cairo compiler 2.x.x uses v0.2.x.

Building from source

You need the Rust compiler and Cargo. Building from git:

cargo install --git https://github.com/crytic/caracal --profile release --force

Building from a local copy:

git clone https://github.com/crytic/caracal
cd caracal
cargo install --path . --profile release --force

Usage

List detectors:

caracal detectors

List printers:

caracal printers

Standalone

To use with a standalone cairo file and you have a local cairo compiler binary it's enough to point it to the file. Otherwise otherwise a bundled compiler is used and you need to pass the path to the corelib library either with the --corelib cli option or by setting the CORELIB_PATH environment variable.
Run detectors:

caracal detect path/file/to/analyze
caracal detect path/file/to/analyze --corelib path/to/corelib/src

Run printers:

caracal print path/file/to/analyze --printer printer_to_use --corelib path/to/corelib/src

Cairo project

If you have a cairo project with multiple files and contracts you may need to specify which contracts with --contract-path. The local cairo compiler binary is used if available otherwise a bundled compiler is used. In the latter case you also need to specify the corelib as explained above for the standalone case. The path is the directory where cairo_project.toml resides.
Run detectors:

caracal detect path/to/dir
caracal detect path/to/dir --contract-path token::myerc20::... token::myerc721::...

Run printers:

caracal print path/to/dir --printer printer_to_use

Scarb

If you have a project that uses Scarb you need to add the following in Scarb.toml:

[[target.starknet-contract]]
sierra = true

[cairo]
sierra-replace-ids = true

Then pass the path to the directory where Scarb.toml resides. Run detectors:

caracal detect path/to/dir

Run printers:

caracal print path/to/dir --printer printer_to_use

Detectors

Num Detector What it Detects Impact Confidence Cairo
1 controlled-library-call Library calls with a user controlled class hash High Medium 1 & 2
2 unchecked-l1-handler-from Detect L1 handlers without from address check High Medium 1 & 2
3 felt252-unsafe-arithmetic Detect user controlled operations with felt252 type, which is not overflow/underflow safe Medium Medium 1 & 2
4 reentrancy Detect when a storage variable is read before an external call and written after Medium Medium 1 & 2
5 read-only-reentrancy Detect when a view function read a storage variable written after an external call Medium Medium 1 & 2
6 unused-events Events defined but not emitted Medium Medium 1 & 2
7 unused-return Unused return values Medium Medium 1 & 2
8 unenforced-view Function has view decorator but modifies state Medium Medium 1
9 tx-origin Detect usage of the transaction origin address as access control Medium Medium 2
10 unused-arguments Unused arguments Low Medium 1 & 2
11 reentrancy-benign Detect when a storage variable is written after an external call but not read before Low Medium 1 & 2
12 reentrancy-events Detect when an event is emitted after an external call leading to out-of-order events Low Medium 1 & 2
13 dead-code Private functions never used Low Medium 1 & 2
14 use-after-pop-front Detect use of an array or a span after removing element(s) Low Medium 1 & 2

The Cairo column represent the compiler version(s) for which the detector is valid.

Printers

  • cfg: Export the CFG of each function to a .dot file
  • callgraph: Export function call graph to a .dot file

How to contribute

Check the wiki on the following topics:

Limitations

  • Inlined functions are not handled correctly.
  • Since it's working over the SIERRA representation it's not possible to report where an error is in the source code but we can only report SIERRA instructions/what's available in a SIERRA program.