How to convert PE(Portable Executable) format to E

Question

What's the best tool for converting PE binaries to ELF binaries?

Following is a brief motivation for this question:

1. Suppose I have a simple C program.
2. I compiled it using gcc for linux(this gives ELF), and using 'i586-mingw32msvc-gcc' for Windows(this gives a PE binary).
3. I want to analyze these two binaries for similarities, using Bitblaze's static analysis tool - vine(http://bitblaze.cs.berkeley.edu/vine.html)
4. Now vine doesn't have a good support for PE binaries, so I wanted to convert PE->ELF, and then carry on with my comparison/analysis.

Since all the analysis has to run on Linux, I would prefer a utility/tool that runs on Linux.

Thanks

Answer 1

I've found a simpler way to do this. Use the strip command.

Example

strip -O elf32-i386 -o myprogram.elf -N xxxxxxx myprogram.exe

The -N xxxxxxx option tells strip to only strip the symbol named xxxxxxx, which hopefully isn't in the file. The -O elf32-i386 has it write out the file in that format.

To see supported formats run

strip --info

I am using the strip command from mxe, which on my system is actually named /opt/mxe/usr/bin/i686-w64-mingw32.static-strip.

Answer 2

I don't know whether this totally fits your needs, but is it an option for you to cross-compile with your MinGW version of gcc?

I mean do say: does it suit your needs to have i586-mingw32msvc-gcc compile direct to ELF format binaries (instead of the PEs you're currently getting). A description of how to do things in the other direction can be found here - I imagine it will be a little hacky but entirely possible to make this work for you in the other direction (I must admit I haven't tried it).

Answer 3

It is possible to rebuild an EXE as an ELF binary, but the resulting binary will segfault very soon after loading, due to the missing operating system.

Here's one method of doing it.

Summary

1. Dump the section headers of the EXE file.
2. Extract the raw section data from the EXE.
3. Encapsulate the raw section data in GNU linker script snippets.
4. Write a linker script to build an ELF binary, including those scripts from the previous step.
5. Run ld with the linker script to produce the ELF file.
6. Run the new program, and watch it segfault as it's not running on Windows (and it tries to call functions in the Import Address Table, which doesn't exist).

Detailed Example

1. Dump the section headers of the EXE file. I'm using objdump from the mingw cross compiler package to do this.

   $ i686-pc-mingw32-objdump -h trek.exe
   
   trek.exe:         file format pei-i386
   
   Sections:
   Idx Name          Size      VMA       LMA       File off  Algn
     0 AUTO          00172600  00401000  00401000  00000400  2**2
                     CONTENTS, ALLOC, LOAD, READONLY, CODE
     1 .idata        00001400  00574000  00574000  00172a00  2**2
                     CONTENTS, ALLOC, LOAD, DATA
     2 DGROUP        0002b600  00576000  00576000  00173e00  2**2
                     CONTENTS, ALLOC, LOAD, DATA
     3 .bss          000e7800  005a2000  005a2000  00000000  2**2
                     ALLOC
     4 .reloc        00013000  0068a000  0068a000  0019f400  2**2
                     CONTENTS, ALLOC, LOAD, READONLY, DATA
     5 .rsrc         00000a00  0069d000  0069d000  001b2400  2**2
                     CONTENTS, ALLOC, LOAD, READONLY, DATA
   

2. Use dd (or a hex editor) to extract the raw section data from the EXE. Here, I'm just going to copy the code and data sections (named AUTO and DGROUP in this example). You may want to copy additional sections though.

   $ dd  bs=512  skip=2     count=2963  if=trek.exe  of=code.bin
   $ dd  bs=512  skip=2975  count=347   if=trek.exe  of=data.bin
   

   Note, I've converted the file offsets and section sizes from hex to decimal to use as skip and count, but I'm using a block size of 512 bytes in dd to speed up the process (example: 0x0400 = 1024 bytes = 2 blocks @ 512 bytes).

3. Encapsulate the raw section data in GNU ld linker scripts snippets (using the BYTE directive). This will be used to populate the sections.

   cat code.bin | hexdump -v -e '"BYTE(0x" 1/1 "%02X" ")\n"' >code.ld
   cat data.bin | hexdump -v -e '"BYTE(0x" 1/1 "%02X" ")\n"' >data.ld
   

4. Write a linker script to build an ELF binary, including those scripts from the previous step. Note I've also set aside space for the uninitialized data (.bss) section.

   start = 0x516DE8;
   ENTRY(start)
   OUTPUT_FORMAT("elf32-i386")
   SECTIONS {
       .text 0x401000 :
       {
           INCLUDE "code.ld";
       }
       .data 0x576000 :
       {
           INCLUDE "data.ld";
       }
       .bss 0x5A2000 :
       {
           . = . + 0x0E7800;
       }
   }
   

5. Run the linker script with GNU ld to produce the ELF file. Note I have to use an emulation mode elf_i386 since I'm using 64-bit Linux, otherwise a 64-bit ELF would be produced.

   $ ld -o elf_trek -m elf_i386 elf_trek.ld
   ld: warning: elf_trek.ld contains output sections; did you forget -T?
   $ file elf_trek
   elf_trek: ELF 32-bit LSB  executable, Intel 80386, version 1 (SYSV), 
             statically linked, not stripped
   

6. Run the new program, and watch it segfault as it's not running on Windows.

   $ gdb elf_trek
   (gdb) run
   Starting program: /home/quasar/src/games/botf/elf_trek 
   
   Program received signal SIGSEGV, Segmentation fault.
   0x0051d8e6 in ?? ()
   (gdb) bt
   \#0  0x0051d8e6 in ?? ()
   \#1  0x00000000 in ?? ()
   (gdb) x/i $eip
   => 0x51d8e6:    sub    (%edx),%eax
   (gdb) quit
   

   IDA Pro output for that location:

   0051D8DB ; size_t stackavail(void)
   0051D8DB proc    stackavail near
   0051D8DB         push    edx
   0051D8DC         call    [ds:off_5A0588]
   0051D8E2         mov     edx, eax
   0051D8E4         mov     eax, esp
   0051D8E6         sub     eax, [edx]
   0051D8E8         pop     edx
   0051D8E9         retn
   0051D8E9 endp    stackavail
   

For porting binaries to Linux, this is kind of pointless, given the Wine project. For situations like the OP's, it may be appropriate.