sigmatcher 1.3.4

Write signatures to automatically match java classes and methods between version

sigmatcher

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Sigmatcher is a powerful tool designed to automate the process of matching Java classes and methods across different versions of an application. It leverages signature on the smali (disassembled java code) to identify and correlate code elements, making it an invaluable resource for long-running reverse engineering projects.

Table of Contents

• Installation
• Quick Usage
• Creating Signature Files
• License

Installation

Before installing sigmatcher, ensure you have the following prerequisites installed:

• ripgrep: A command-line search tool that recursively searches your current directory for a regex pattern. Install ripgrep by following the instructions on its GitHub page.
• apktool: A tool for reverse engineering and disassembling Android apk files. Install apktool by following the instructions on its official website.

git clone https://github.com/oriori1703/sigmatcher.git
pip install ./sigmatcher

Quick Usage

To get started with sigmatcher, follow these steps:

1. Create a Signature File: Signature files (.yaml) define the patterns and signatures that Sigmatcher will use to analyze the APK files. These files should specify the classes, methods, and fields you're interested in, along with any version-specific information. See the Creating Signature Files section example for the format.
2. Analyze an APK: With your signature file ready, you can now analyze an APK to find matches for your signatures. Use the sigmatcher analyze command, specifying the path to the APK and the signature file(s):

   sigmatcher analyze --apk path/to/your/app.apk --signatures path/to/your/signature_file.yaml
   

   This command will decode the APK, apply the signatures, and output the analysis results, highlighting matched classes, methods and fields.

Creating Signature Files

Signature files are YAML formatted documents that sigmatcher uses to identify and match Java classes, methods, and fields in APK files. These files allow you to specify the elements you're interested in tracking across different versions of an application.

Signature File JSON Schema

To help you create a signature file sigmatcher provides a JSON schema that you can use to validate your signature, and get autocompletion and intellisense from your IDE. You can get it by running the following command:

sigmatcher schema > definitions.schema.json

To use the schema in your IDE, you can add the following comment to the top of your signature file:

# $schema: ./definitions.schema.json

Structure of a Signature File

A signature file consists of a list of definitions, where each definition represents a class, method, or field you want to match. Each definition can include one or more signatures, which are patterns sigmatcher will use to find matches in the smali code.

Here's a basic example of what a signature file looks like:

# $schema: ./definitions.schema.json
- name: "ConnectionManager"
  package: "com.example.package.network"
  signatures:
    - signature: 'ConnectionManager/openConnection: could not open connection due to a DNS error'
      type: regex
      count: 1
  methods:
    - name: "read"
      signatures:
        - signature: 'const-string v\d+, "Failed to read data from the server"'
          type: regex
          count: 1
          version_range: ">=1.0.0, <1.3.7"
        - signature: 'const-string v\d+, "Failed to read data because of a network error"'
          type: regex
          count: 1
          version_range: ">=1.3.7"
  fields:
    - name: "socket"
      signatures:
        - signature: '^\.field private final (?P<match>.+:Ljava/net/Socket;)'
          type: regex
          count: 1

Key Components

• name: The name of the class, method, or field.
• methods: A list of method definitions within a class. Follows a similar structure to the class definition.
• fields: A list of field definitions within a class. Follows a similar structure to the class definition.
• exports: A list of export definitions within a class. Exports can be any string in the code. They are mainly used in combination with macros to create more complex signatures.
• signatures: A list of signatures for the class, method, or field. Each signature includes:
  • type: The type of signature (for now only regex and glob).
  • signature: The pattern to match, depending on the signature type. For classes and methods they just need to match anywhere within the class/method. For fields and exports, they need to match the full field expression/export string, i.e. using the match capture group for regex signatures.
  • count: The number of times the signature should appear to be considered a match.
  • version_range: Optional. Specifies the application versions this signature applies to, using version specifiers like those used by pip and described in PEP-440.

Most of those fields are optional, and you can use them as needed.

License

sigmatcher is distributed under the terms of the MIT license.