# reFlutter | Flutter Reverse Engineering Framework

**URL:** <https://onehack.st/t/reflutter-flutter-reverse-engineering-framework/212615>\
**Category:** Tools & Scripts\
**Tags:** tools, programming, hacking\
**Created:** [January 20, 2022, 1:42pm UTC](https://onehack.st/t/reflutter-flutter-reverse-engineering-framework/212615 "2022-01-20T13:42:40Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Astrid](https://onehack.st/user_avatar/onehack.st/astrid/32/174869_2.png) [@Astrid](https://onehack.st/u/Astrid)\
**Post date:** [January 20, 2022, 1:42pm UTC](https://onehack.st/t/reflutter-flutter-reverse-engineering-framework/212615/1 "2022-01-20T13:42:40Z")

</div>

![image](https://onehack.st/uploads/default/original/3X/2/a/2aca4d69c99032d56982d7e66bee9483294f84b3.png)

This framework helps with Flutter apps reverse engineering using the patched version of the Flutter library which is already compiled and ready for app repacking. This library has snapshot deserialization process modified to allow you perform dynamic analysis in a convenient way.

Key features:

- `socket.cc` is patched for traffic monitoring and interception;
- `dart.cc` is modified to print classes, functions and some fields;
- contains minor changes for successfull compilation;
- if you would like to implement your own patches, there is manual Flutter code change is supported using specially crafted `Dockerfile`

### Supported engines

- Android: arm64, arm32;
- iOS: arm64;
- Release: Stable, Beta

### Install

```auto
# Linux, Windows, MacOS
pip3 install reflutter

```

### Usage

impact@f:~$ reflutter main.apk Please enter your Burp Suite IP: \<input\_ip\> SnapshotHash: 8ee4ef7a67df9845fba331734198a953 The resulting apk file: ./release.RE.apk Please sign the apk file Configure Burp Suite proxy server to listen on \*:8083 Proxy Tab → Options → Proxy Listeners → Edit → Binding Tab Then enable invisible proxying in Request Handling Tab Support Invisible Proxying → true impact@f:~$ reflutter main.ipa

### Traffic interception

You need to specify the IP of your Burp Suite Proxy Server located in the same network where the device with the flutter application is. Next, you should configure the Proxy in `BurpSuite -> Listener Proxy -> Options tab`

- Add port: `8083`
- Bind to address: `All interfaces`
- Request handling: Support invisible proxying = `True`

[![](https://user-images.githubusercontent.com/87244850/135753172-20489ef9-0759-432f-b2fa-220607e896b8.png)](https://user-images.githubusercontent.com/87244850/135753172-20489ef9-0759-432f-b2fa-220607e896b8.png)

You don’t need to install any certificates. On an Android device, you don’t need root access as well. reFlutter also allows to bypass some of the flutter certificate pinning implementations.

### Usage on Android

The resulting apk must be aligned and signed. I use [uber-apk-signer](https://github.com/patrickfav/uber-apk-signer/releases/tag/v1.2.1) `java -jar uber-apk-signer.jar --allowResign -a release.RE.apk`. To see which code is loaded through DartVM, you need to run the application on the device. reFlutter prints its output in logcat with the `reflutter` tag

impact@f:~$ adb logcat -e reflutter | sed ‘s/.\*DartVM//’ \>\> reflutter.txt

code output

### Usage on iOS

Use the IPA file created after the execution of `reflutter main.ipa` command. To see which code is loaded through DartVM, you need to run the application on the device. reFlutter prints its output in console logs in XCode with the `reflutter` tag.

[![](https://user-images.githubusercontent.com/87244850/135860648-a13ba3fd-93d2-4eab-bd38-9aa775c3178f.png)](https://user-images.githubusercontent.com/87244850/135860648-a13ba3fd-93d2-4eab-bd38-9aa775c3178f.png)

### To Do

- Display absolute code offset for functions;
- Extract more strings and fields;
- Add socket patch;
- Extend engine support to Debug using Fork and Github Actions;
- Improve detection of `App.framework` and `libapp.so` inside zip archive

### Build Engine

The engines are built using [reFlutter](https://github.com/ptswarm/reFlutter/blob/main/.github/workflows/main.yml) in [Github Actions](https://github.com/ptswarm/reFlutter/actions) to build the desired version, commits and snapshot hashes are used from this [table](https://github.com/ptswarm/reFlutter/blob/main/enginehash.csv). The hash of the snapshot is extracted from `storage.googleapis.com/flutter_infra_release/flutter/<hash>/android-arm64-release/linux-x64.zip`

release

### Custom Build

If you would like to implement your own patches, manual Flutter code change is supported using specially crafted [Docker](https://hub.docker.com/r/ptswarm/reflutter)

`sudo docker pull ptswarm/reflutter`

```auto
# Linux, Windows
EXAMPLE BUILD ANDROID ARM64:
    sudo docker run -e WAIT=300 -e x64=0 -e arm=0 -e HASH_PATCH=<Snapshot_Hash> -e COMMIT=<Engine_commit> --rm -iv${PWD}:/t ptswarm/reflutter

FLAGS:
    -e x64=0 <disables building for x64 archiitechture, use to reduce building time>
    -e arm=0 <disables building for arm archiitechture, use to reduce building time>
    -e WAIT=300 <the amount of time in seconds you need to edit source code>
    -e HASH_PATCH=[Snapshot_Hash] <here you need to specify snapshot hash which matches the engine_commit line of enginehash.csv table best. It is used for proper patch search in reFlutter and for successfull compilation>
    -e COMMIT=[Engine_commit] <here you specify commit for your engine version, take it from enginehash.csv table or from flutter/engine repo>

```

## GitHub:

> **[GitHub - ptswarm/reFlutter: Flutter Reverse Engineering Framework](https://github.com/ptswarm/reFlutter)**
>
> Flutter Reverse Engineering Framework