radare2 plugin - converts asm to pseudo-C code

Nytro · September 19, 2018

r2dec

Converts asm to pseudo-C code.

Software Requirements

Requires radare2 version 2.9.0 or newer.

Install

Follow the following steps to install r2dec via r2pm

r2pm init
r2pm install r2dec

done

Usage

open with radare2 your file
analize the function you want to disassemble (af)
run the plugin via pdd
done.

Arguments

[0x00000000]> pdd?
Usage: pdd [args] - core plugin for r2dec
 pdd   - decompile current function
 pdd?  - show this help
 pdda  - decompile current function with side assembly
 pddb  - decompile current function but shows only scopes
 pddu  - install/upgrade r2dec via r2pm
 pddi  - generates the issue data
Environment
 R2DEC_HOME  defaults to the root directory of the r2dec repo
[0x00000000]> pdd --help

r2dec [options]
       --help       | this help message
       --assembly   | shows pseudo next to the assembly
       --blocks     | shows only scopes blocks
       --colors     | enables syntax colors
       --casts      | shows all casts in the pseudo code
       --debug      | do not catch exceptions
       --html       | outputs html data instead of text
       --issue      | generates the json used for the test suite
       --paddr      | all xrefs uses physical addresses instead of virtual addresses
       --xrefs      | shows also instruction xrefs in the pseudo code

Radare2 Evaluable vars

You can use these in your .radare2rc file.

r2dec.casts         | if false, hides all casts in the pseudo code.
r2dec.asm           | if true, shows pseudo next to the assembly.
r2dec.blocks        | if true, shows only scopes blocks.
r2dec.paddr         | if true, all xrefs uses physical addresses compare.
r2dec.xrefs         | if true, shows all xrefs in the pseudo code.
r2dec.theme         | defines the color theme to be used on r2dec.
e scr.html          | outputs html data instead of text.
e scr.color         | enables syntax colors.

Report an Issue

open with radare2 your file
analize the function you want to disassemble (af)
give the data to the plugin via pddi or pdd --issue
insert the JSON returned by the previous command into the issue (you can also upload the output)
done.

Supported Arch

arm
avr
m68k (experimental)
mips
ppc
sparc
v850
wasm (partial)
x86-64 (intel syntax)

Developing on r2dec

Read DEVELOPERS.md

Example

This example shows a possible dump of the plugin.

Source Code

#include <stdio.h>

int main(int argc, char const *argv[]) {
    int var = 0;
    while(var < 0x90) {
        if(var < 0x10) {
            var += 0x50;
        }
        var += 0x10;
    }
    return 0;
}

radare2 view

╭ (fcn) main 50
│   main (int arg1, int arg2);
│           ; var int local_20h @ rbp-0x20
│           ; var int local_14h @ rbp-0x14
│           ; var signed int local_4h @ rbp-0x4
│           ; DATA XREF from entry0 (0x1041)
│           0x00001119      55             push rbp
│           0x0000111a      4889e5         mov rbp, rsp
│           0x0000111d      897dec         mov dword [local_14h], edi  ; arg1
│           0x00001120      488975e0       mov qword [local_20h], rsi  ; arg2
│           0x00001124      c745fc000000.  mov dword [local_4h], 0
│       ╭─< 0x0000112b      eb0e           jmp 0x113b
│       │   ; CODE XREF from main (0x1142)
│      ╭──> 0x0000112d      837dfc0f       cmp dword [local_4h], 0xf   ; [0xf:4]=0x3e000300
│     ╭───< 0x00001131      7f04           jg 0x1137
│     │⋮│   0x00001133      8345fc50       add dword [local_4h], 0x50  ; 'P'
│     │⋮│   ; CODE XREF from main (0x1131)
│     ╰───> 0x00001137      8345fc10       add dword [local_4h], 0x10
│      ⋮│   ; CODE XREF from main (0x112b)
│      ⋮╰─> 0x0000113b      817dfc8f0000.  cmp dword [local_4h], 0x8f  ; [0x8f:4]=0x2a800
│      ╰──< 0x00001142      7ee9           jle 0x112d
│           0x00001144      b800000000     mov eax, 0
│           0x00001149      5d             pop rbp
╰           0x0000114a      c3             ret

r2dec pseudo-C code

/* r2dec pseudo C output */
#include <stdint.h>
 
int32_t main (int32_t argc, char ** argv) {
    char ** local_20h;
    int32_t local_14h;
    int32_t local_4h;
    local_14h = edi;
    local_20h = rsi;
    local_4h = 0;
    while (local_4h <= 0x8f) {
        if (local_4h <= 0xf) {
            local_4h += 0x50;
        }
        local_4h += 0x10;
    }
    eax = 0;
    return eax;
}

Sursa: https://github.com/wargio/r2dec-js

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