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:

• How to write a detector
• How to write a printer

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.