Once upon a time I was a very avid desktop user of Ubuntu Linux. As a software developer, I would usually need the standard build tools installed on my machine.
Installing build tools in Debian/Ubuntu
In Debian/Ubuntu, you can install the typical build tools by installing the package build-essentials, which is just a pseudo-package that downloads all the popular development packages:
# apt-get install build-essentials
Installing build tools in CentOS
Since I prefer CentOS as my server platform, I also occasionally need to install packages using yum.
To install the common build tools using yum in CentOS you’ll want to install the group package “Development Tools”, which is similar to build-essentials in Debian/Ubuntu flavors of linux. You’ll probably also want to install kernel-devel and kernel-headers if they’re not already installed:
I’ve been writing a lot of articles recently about compiling C and assembly programs on my 64-bit machine. But eventually I needed to compile a 32-bit program and I thought I would explain how I did that in case anyone else runs into trouble.
Using the -m32 flag
To compile a 32-bit program with gcc you can just use the m32 flag (which you’ll find under i386 and x86-64 Options on the gcc man page). But if you’re on a 64-bit machine, don’t be surprised if you see something like this:
# gcc -m32 -o example32bit example32bit.c
In file included from /usr/include/features.h:378,
/usr/include/gnu/stubs.h:7:27: error: gnu/stubs-32.h: No such file or directory
Installing the 32-bit glibc headers
You see that because you don’t have the 32-bit glibc headers installed. That’s not a problem though, since most package managers should have them available for installation. If you’re on a Debian or Ubuntu machine you can install them like this:
If you’re learning about buffer overflows and shellcode, chances are you’re exploiting some stack-based vulnerabilities. If you’re like me you might also find that when you compile your programs they have stack execution disabled by default. So instead of getting excited as you see your shellcode blissfully running after smashing the stack, you might just see this instead:
Program received signal SIGSEGV, Segmentation fault.
0x0000000000601018 in shellcode ()
“Noooo! You can’t do this to me! I want to write exploits!”
Ok.. calm down.. we just need to turn on stack execution when compiling.