debugging a 32bit binary on a 64bit machine with GDB, file not found

Question

I understand from other SO threads that gdb can debug both 32bit and 64bit binaries on a 64bit architecture, but when I run it I have the following issue :

Starting program: /root/crackme-01 
/bin/bash: /root/crackme-01: No such file or directory
During startup program exited with code 127.

Here is the result of file on the program :

crackme-01: ELF 32-bit LSB  executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.32, BuildID[sha1]=9feb70a8647779984dc69b1e5c90bd757343fb29, stripped

Is there anything else I should do to debug it?

Thanks for your help.

Answer 1

GDB can only debug a program that can start by itself. In your case, the program couldn't start at all (not a single instruction was executed in user space for your process, the execve system call failed). This:

/bin/bash: /root/crackme-01: No such file or directory

is almost always caused by missing program interpreter. You can see the interpreter like so:

readelf -l /root/crackme-01 | grep interpreter

In your case, the interpreter is almost certainly /lib/ld-linux.so.2.

I was just missing the libraries

You were missing libc6:i386, which ld-linux.so.2 is part of.

Answer 2

I was just missing the libraries as explained here

I needed to install the 32bit libs with :

sudo dpkg --add-architecture i386
sudo apt-get update
sudo apt-get install libc6:i386 libncurses5:i386 libstdc++6:i386