reverse-engineer

 
## 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"

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

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