Memory Error Primer

Code snippets and virtual machine that I use for teaching purposes.

Getting Started

Step 1: Clone this repository

$ git clone https://github.com/phretor/memory-errors-lab.git

Step 2: Install VirtualBox according to your host operating system's recommended procedure.

Step 3: Install Vagrant (instructions here).

Step 4: Start the virtual machine:

$ cd memory-errors-lab/linux64
$ vagrant plugin install vagrant-vbguest
$ vagrant up

If you want to skip the vbguest plugin installation, you'll have to setup the VirtualBox guest additions yourself.

Step 5: Start hacking:

$ vagrant up
$ vagrant ssh

GCC Options

When compiling, the following options are recommended:

-fno-stack-protector           # disables stack-smashing protection
-z execstack                   # enables executable stack
-mpreferred-stack-boundary=2   # aligns memory allocation to 2^2 bytes
-m32                           # compile as 32-bitx86 elf file

Since the -mpreferred-stack-boundary=2 option affects how the machine allocates memory on the stack, it also affects the displacement calculation when preparing format string exploits. Therefore, disabling this option is recommended when practicing with format string bugs.