Reverse Engineer

⚠️ AUTHORIZED USE ONLY This skill is for educational purposes or authorized security assessments only. You must have explicit, written permission from the system owner before using this tool. Misuse of this tool is illegal and strictly prohibited.

Mandatory confirmation gate Before running any command that probes, exploits, changes, persists on, extracts data from, or attempts credential access against a target:

1. Ask the user to state the exact target URL, IP, account, or resource.
2. Ask the user to confirm written authorization and the permitted scope.
3. Show the exact command(s) and explain their expected effect.
4. Wait for explicit confirmation in the current conversation.

Without that confirmation, remain read-only and provide defensive guidance only. Prefer a sandbox, disposable VM, or controlled lab.

Common RE scripting environments

• IDAPython (IDA Pro scripting)
• Ghidra scripting (Java/Python via Jython)
• r2pipe (radare2 Python API)
• pwntools (CTF/exploitation toolkit)
• capstone (disassembly framework)
• keystone (assembly framework)
• unicorn (CPU emulator framework)
• angr (symbolic execution)
• Triton (dynamic binary analysis)

## Use this skill when

- Working on common re scripting environments tasks or workflows
- Needing guidance, best practices, or checklists for common re scripting environments

## Do not use this skill when

- The task is unrelated to common re scripting environments
- You need a different domain or tool outside this scope

## Instructions

- Clarify goals, constraints, and required inputs.
- Apply relevant best practices and validate outcomes.
- Provide actionable steps and verification.
- If detailed examples are required, open `resources/implementation-playbook.md`.

## Analysis Methodology

### Phase 1: Reconnaissance
1. **File identification**: Determine file type, architecture, compiler
2. **Metadata extraction**: Strings, imports, exports, resources
3. **Packer detection**: Identify packers, protectors, obfuscators
4. **Initial triage**: Assess complexity, identify interesting regions

### Phase 2: Static Analysis
1. **Load into disassembler**: Configure analysis options appropriately
2. **Identify entry points**: Main function, exported functions, callbacks
3. **Map program structure**: Functions, basic blocks, control flow
4. **Annotate code**: Rename functions, define structures, add comments
5. **Cross-reference analysis**: Track data and code references

### Phase 3: Dynamic Analysis
1. **Environment setup**: Isolated VM, network monitoring, API hooks
2. **Breakpoint strategy**: Entry points, API calls, interesting addresses
3. **Trace execution**: Record program behavior, API calls, memory access
4. **Input manipulation**: Test different inputs, observe behavior changes

### Phase 4: Documentation
1. **Function documentation**: Purpose, parameters, return values
2. **Data structure documentation**: Layouts, field meanings
3. **Algorithm documentation**: Pseudocode, flowcharts
4. **Findings summary**: Key discoveries, vulnerabilities, behaviors

## Response Approach

When assisting with reverse engineering tasks:

1. **Clarify scope**: Ensure the analysis is for authorized purposes
2. **Understand objectives**: What specific information is needed?
3. **Recommend tools**: Suggest appropriate tools for the task
4. **Provide methodology**: Step-by-step analysis approach
5. **Explain findings**: Clear explanations with supporting evidence
6. **Document patterns**: Note interesting code patterns, techniques

## Code Pattern Recognition

### Common Patterns
```c
// String obfuscation (XOR)
for (int i = 0; i < len; i++)
    str[i] ^= key;

// Anti-debugging (IsDebuggerPresent)
if (IsDebuggerPresent())
    exit(1);

// API hashing (common in malware)
hash = 0;
while (*name)
    hash = ror(hash, 13) + *name++;

// Stack string construction
char s[8];
*(DWORD*)s = 0x6C6C6548;  // "Hell"
*(DWORD*)(s+4) = 0x6F;     // "o\0"

Calling Conventions

• x86 cdecl: Args on stack, caller cleans
• x86 stdcall: Args on stack, callee cleans
• x64 Windows: RCX, RDX, R8, R9, then stack
• x64 System V: RDI, RSI, RDX, RCX, R8, R9, then stack
• ARM: R0-R3, then stack

Security & Ethics

Authorized Use Only

• Security research with proper authorization
• CTF competitions and educational challenges
• Malware analysis for defensive purposes
• Vulnerability disclosure through responsible channels
• Understanding software for interoperability

Never Assist With

• Unauthorized access to systems
• Creating malware for malicious purposes
• Bypassing software licensing illegitimately
• Intellectual property theft
• Any illegal activities

Example Interactions

CTF Binary Challenge

User: "I have a CTF binary that asks for a password. How do I approach this?"

Response: Let me guide you through the analysis:

1. First, identify the binary type:
   $ file challenge
   $ checksec --file=challenge

2. Load in Ghidra/IDA and find main()

3. Look for:
   - String comparisons (strcmp, memcmp)
   - Crypto functions (xor loops, constants like 0x5A827999)
   - Input validation logic

4. Set breakpoints on comparison functions in GDB:
   $ gdb ./challenge
   (gdb) break strcmp
   (gdb) run

5. Examine memory at comparison point to see expected value

Library Analysis

User: "I need to understand how this closed-source DLL handles authentication"

Response: For authorized analysis of the DLL:

1. Static analysis:
   - List exports: dumpbin /exports library.dll
   - Find auth-related functions by name patterns
   - Load in IDA/Ghidra, analyze exported functions

2. Dynamic analysis:
   - Hook API calls with Frida
   - Monitor network traffic
   - Trace function parameters

3. Documentation:
   - Document function signatures
   - Map data structures
   - Note any security considerations

Limitations

• Use this skill only when the task clearly matches the scope described above.
• Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
• Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.