rev-struct

rev-struct - Structure Recovery

Recover data structure definitions by analyzing memory access patterns in functions and their call chains.

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

Function File Format (decompile/*.c)

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

Structure Recovery Steps

Step 1: Read Target Function

1. Based on the user-provided address, read decompile/<address>.c
2. Parse function metadata, extract callers and callees lists
3. Identify pointer parameters in the function (potential structure pointers)

Step 2: Collect Memory Access Patterns

Search for the following patterns in the target function:

Direct offset access:

Array access:

Nested structures:

Record format:

Step 3: Traverse Callers for Analysis

Read each caller function and analyze:

1. Parameter passing: What is passed when calling?

   sub_401000(v1);        // v1 might be a struct pointer
   sub_401000(&v2);       // v2 is a struct
   sub_401000(malloc(64)); // struct size is ~64 bytes

2. Operations before/after the call:

   v1 = malloc(0x40);     // allocate 0x40 bytes
   *v1 = 0;               // offset 0x00 initialization
   *(v1 + 8) = callback;  // offset 0x08 is a function pointer
   sub_401000(v1);

3. Collect more offset accesses

Step 4: Traverse Callees for Analysis

Read each callee function and analyze:

1. How parameters are used:

   // In callee
   int callee(void *a1) {
       return *(a1 + 0x18);  // accesses offset 0x18
   }

2. Passed to other functions:

   another_func(a1 + 0x20);  // offset 0x20 might be a nested struct

Step 5: Aggregate and Infer

1. Merge all offset information, sort by offset
2. Calculate struct size: max(offset) + last_field_size
3. Infer field types:
   • Called as function pointer → function pointer
   • Passed to strlen/printf → string pointer
   • Compared with constants → enum/flags
   • Increment/decrement operations → counter/index
4. Identify common patterns:
   • Offset 0 is a function pointer table → vtable (C++ object)
   • next/prev pointers → linked list node
   • refcount field → reference counted object

Output Format

/*
 * Structure Recovery Analysis
 * Source function: <func_address>
 * Analysis scope: <number of callers/callees analyzed>
 * 
 * Functions using this struct:
 *   - 0x401000 (initialization)
 *   - 0x401100 (field access)
 *   - 0x401200 (destruction)
 */
 
// Estimated size: 0x48 bytes
// Confidence: High / Medium / Low
 
struct suggested_name {
    /* 0x00 */ void *vtable;           // vtable pointer, called: (*(*this))()
    /* 0x08 */ int refcount;           // reference count, has ++/-- operations
    /* 0x0C */ int flags;              // flags, AND with 0x1, 0x2
    /* 0x10 */ char *name;             // string, passed to strlen/printf
    /* 0x18 */ void *data;             // data pointer
    /* 0x20 */ size_t size;            // size field
    /* 0x28 */ struct node *next;      // linked list next pointer
    /* 0x30 */ struct node *prev;      // linked list prev pointer
    /* 0x38 */ callback_fn handler;    // callback function
    /* 0x40 */ void *user_data;        // user data
};
 
// Field access examples:
// 0x401000: *(this + 0x08) += 1;     // refcount++
// 0x401100: printf("%s", *(this + 0x10));  // print name
```*