rev-symbol - Symbol Recovery

Analyze function code characteristics to recover/identify function symbols and names.

Pre-check

Determine which IDA access method is available:

Option A — IDA Pro MCP (preferred if connected): Check if the IDA Pro MCP server is connected (look for an active ida-pro or equivalent MCP connection). If connected, you can query IDA directly via MCP tools — no exported files needed. Proceed with the analysis using MCP.

Option B — IDA-NO-MCP exported data: If MCP is not connected, check if IDA-NO-MCP exported data exists in the current directory:

1. Check if decompile/ directory exists
2. Check if there are .c files inside

If neither MCP nor exported data is available, prompt the user:

No IDA access method detected. Choose one of the following:

Option A — IDA Pro MCP (recommended):
  Connect the IDA Pro MCP server so Claude can query IDA directly.

Option B — IDA-NO-MCP export:
  1. Download plugin: https://github.com/P4nda0s/IDA-NO-MCP
  2. Copy INP.py to IDA plugins directory
  3. Press Ctrl-Shift-E in IDA to export
  4. Open the exported directory with Claude Code

Export Directory Structure

./
├── decompile/              # Decompiled C code directory
│   ├── 0x401000.c          # One file per function, named by hex address
│   ├── 0x401234.c
│   └── ...
├── decompile_failed.txt    # Failed decompilation list
├── decompile_skipped.txt   # Skipped functions list
├── strings.txt             # String table (address, length, type, content)
├── imports.txt             # Import table (address:function_name)
├── exports.txt             # Export table (address:function_name)
└── memory/                 # Memory hexdump (1MB chunks)

Function File Format (decompile/*.c)

Each .c file contains function metadata comments and decompiled code:

/*
 * func-name: sub_401000
 * func-address: 0x401000
 * callers: 0x402000, 0x403000    // List of functions that call this function
 * callees: 0x404000, 0x405000    // List of functions called by this function
 */

int __fastcall sub_401000(int a1, int a2)
{
    // Decompiled code...
}

Symbol Recovery Steps

Step 1: Analyze Internal Characteristics

Carefully examine the target function for:

• String constants: Strings used in the function may reveal its purpose
• Numeric constants / Magic Numbers:

- MD5: 0x67452301, 0xEFCDAB89, 0x98BADCFE, 0x10325476 - CRC32: 0xEDB88320 - Base64 charset: ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ - AES S-Box: 0x63, 0x7C, 0x77, 0x7B... - Zlib: 0x78, 0x9C (compression header) - other constants/magic numbers...

• Code structure: Loop patterns, bitwise operations, specific algorithm flows

If you can identify a known algorithm through constants/structure, tell the user directly.

Step 2: Analyze Cross-References

Analyze Callees (called functions):

• Read functions in the callees list
• For each callee, check if its address exists in imports.txt
• Recognize call patterns even when symbols are missing:

Paired function patterns (identify by matching call pairs): ```c // malloc/free, new/delete, alloc/dealloc xx = subA(0x100); // alloc: takes size, returns pointer ... subB(xx); // free: takes the same pointer

// mutexlock/mutexunlock, pthreadmutexlock/unlock subA(lockptr); // lock ... // critical section subB(lockptr); // unlock (same lock object)

// open/close, fopen/fclose, CreateFile/CloseHandle fd = subA("/path", 0); // open: path + flags, returns handle ... subB(fd); // close: takes the handle

// pthreadcreate/pthreadjoin subA(&tid, 0, func, arg); // create: out param, attr, func, arg ... subB(tid, &ret); // join: tid, out param

Argument pattern recognition: ```c // socket(AFINET, SOCKSTREAM, 0) - fixed constants sub_XXX(2, 1, 0); // socket: domain=2, type=1, protocol=0

// connect/bind(sockfd, addr, addrlen) sub_XXX(fd, &var, 16); // addr struct, len=16 for IPv4

// memcpy/memmove(dst, src, size) sub_XXX(dst, src, n); // 3 params: dst, src, count

// memset(ptr, value, size) sub_XXX(ptr, 0, 0x100); // 3 params: ptr, byte value, count

// read/write(fd, buf, count) ret = sub_XXX(fd, buf, n); // returns bytes read/written

// strcmp/strncmp(s1, s2) or (s1, s2, n) if (sub_XXX(s1, s2) == 0) // returns 0 on equal ```

Return value patterns: ```c // file/socket operations: -1 on error if ((fd = sub_XXX(...)) == -1) goto error;

// allocation: NULL on failure if (!(ptr = sub_XXX(size))) goto error;

// success/error: 0 = success if (sub_XXX(...) != 0) goto error;

// strlen: returns sizet len = subXXX(str); sub_YYY(dst, src, len); // len used in memcpy ```

Analyze Callers (calling functions):

• Read functions in the callers list
• If a caller has a symbol (check exports.txt), infer the callee's purpose from context
• Recursive check: trace up the call chain until you find a function with a symbol
• Analyze how the return value is used by callers

Step 3: Information Gathering and Search

Collect the following information:

• Strings in the function (check strings.txt for addresses used in the function)
• Magic Numbers / constants
• Known imports called (cross-reference callees with imports.txt)
• Caller/callee symbols from exports.txt
• Paired function patterns identified

Based on collected information:

1. First attempt local reasoning based on:

- Function signature (number and types of parameters) - Paired call patterns (alloc/free, lock/unlock) - Known imports in the call chain - Code structure similarity to known algorithms

1. If uncertain, use Web Search to search:

- Search Magic Numbers: 0x67452301 0xEFCDAB89 algorithm - Search code patterns: rotate left xor constant algorithm - Search unique strings found in the function - Search parameter patterns: function(int, int, 0) socket

Output Format

## Symbol Recovery Analysis: <function_address>

### Function Characteristics
- Strings: <list discovered strings>
- Constants: <list key constants>
- Called imports: <list>

### Cross-Reference Analysis
- Callers: <callers and their symbols>
- Callees: <callees and their symbols>

### Inference Result
- **Suggested symbol name**: <suggested_name>
- **Confidence**: High / Medium / Low
- **Reasoning**: <explain why this name is suggested>

### Similar Open Source Implementation
- <if similar open source code is found, provide link>