Introduction

Tauri is a popular framework for building desktop applications using Rust and web technologies. This guide will walk you through the process of reverse engineering Tauri applications, focusing on key areas such as WebSocket communication and cryptographic operations.

Tauri is a framework for creating desktop applications with Rust and web technologies. It’s known for its high performance and low memory usage, making it a favorite among developers. However, due to its unique architecture, reverse engineering Tauri applications can be a bit challenging. The process becomes especially tricky for those unfamiliar with Rust or similar frameworks.

Difficulty Analysis

The difficulty of reverse engineering Tauri applications mainly lies in the following aspects:

  1. Rust-Compiled Binaries: Rust-compiled binaries are typically highly optimized and contain fewer debugging symbols, which makes reverse engineering more complex. Compared to applications generated by other languages, Rust-compiled programs tend to be more “invisible,” meaning they are harder to read and understand directly.

  2. Encryption and Obfuscation: Tauri applications may involve a series of encryption operations and code obfuscation techniques aimed at protecting sensitive data and logic. These encryption algorithms, such as Ring and AES, are often implemented in a low-level way, which makes reverse engineering more challenging.

  3. WebSocket and IPC: Many Tauri applications interact with the frontend or other services through WebSocket or other inter-process communication (IPC) mechanisms. These communications are often protected by encryption or other protocols, making reverse engineering these communications and interfaces require a bit of expertise.

However, despite these challenges, with the right tools and techniques, you can gain enough insights to understand how Tauri applications work.

Tools for Reverse Engineering

Dynamic Analysis Tools

  • Frida: A dynamic instrumentation toolkit that allows you to monitor and manipulate the behavior of a running application. It is especially useful for capturing WebSocket communication and cryptographic functions.
  • HTTP Traffic Interceptor: Used for monitoring network requests, particularly useful when dealing with WebSocket or HTTP-based communication.

Static Analysis Tools

  • IDA Pro / Ghidra: Two classic tools for static analysis, useful for disassembling and inspecting the binary code of the application.

With these tools, you can deep dive into backend modules, WebSocket communication, cryptographic operations, and IPC mechanisms, among other things.

Basic Frida Script

function monitorGrass() {
    console.log("[*] Starting Grass module monitor...");
    
    const grassModule = Process.enumerateModules()
        .find(m => m.name.toLowerCase().includes('grass'));
    
    if (!grassModule) {
        console.log('[!] Grass module not found');
        return;
    }
    
    const patterns = [
        /websocket/i,     // WebSocket related
        /ring.*encrypt/i, // Ring encryption related
        /ring.*decrypt/i, // Ring decryption related
        /aes/i,           // AES encryption related
        /grass/i,         // Grass related
        /hyper/i,         // Hyper related
        /ws.*connect/i,   // WebSocket connection
        /ws.*message/i,   // WebSocket message
    ];

    const ignorePatterns = [
        /__rust_dealloc/,
        /__rust_alloc/,
        /drop/i,
        /clone/i,
        /debug/i,
        /TokioSleep/,
        /poll/,
    ];

    const exports = grassModule.enumerateExports();
    exports.forEach(exp => {
        if (ignorePatterns.some(pattern => pattern.test(exp.name))) {
            return;
        }

        const isInteresting = patterns.some(pattern => pattern.test(exp.name));
        
        if (exp.type === 'function' && isInteresting) {
            try {
                Interceptor.attach(exp.address, {
                    onEnter: function(args) {
                        console.log(`\n[CALL] ${exp.name}`);
                        
                        try {
                            for (let i = 0; i < 4; i++) { // Read the first 4 arguments
                                if (args[i]) {
                                    try {
                                        const argStr = args[i].readUtf8String();
                                        if (argStr && argStr.length > 0 && argStr.length < 1000) {
                                            console.log(`\tArg${i}:`, argStr);
                                        }
                                    } catch(e) {
                                        console.log(`\tArg${i}: 0x${args[i].toString(16)}`);
                                    }
                                }
                            }
                        } catch(e) {}
                        
                        const stack = Thread.backtrace(this.context, Backtracer.ACCURATE)
                            .map(DebugSymbol.fromAddress)
                            .filter(symbol => !ignorePatterns.some(p => p.test(symbol.toString())));
                        if (stack.length > 0) {
                            console.log("\tBacktrace:");
                            console.log("\t" + stack.join("\n\t"));
                        }
                    },
                    onLeave: function(retval) {
                        try {
                            const ret = retval.readUtf8String();
                            if (ret && ret.length > 0 && ret.length < 1000) {
                                console.log("\tReturn:", ret);
                            }
                        } catch(e) {}
                    }
                });
                
                console.log(`[+] Hooked ${exp.name}`);
            } catch(e) {
                console.log(`[-] Failed to hook ${exp.name}: ${e}`);
            }
        }
    });
    
    console.log("[*] Monitoring setup completed");
}

setImmediate(monitorGrass);