aslr [Doku Wiki]

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===== Overview =====

ASLR (Address Space Layout Randomization) stuff (exec shield?).

Links:

  * [[https://lwn.net/Articles/569635/|Kernel address space layout randomization (LWN, 2013)]]
  * [[https://linux-audit.com/linux-aslr-and-kernelrandomize_va_space-setting/|Linux and ASLR: kernel/randomize_va_space]]
  * [[https://securityetalii.es/2013/02/03/how-effective-is-aslr-on-linux-systems/|How Effective is ASLR on Linux Systems? (2013)]]

Questions:

  * What about kernel ASLR (KASLR)? Look for ''RANDOMIZE'' options.

===== Basics =====

Binaries must be position-independent executables, so worthless on statically-compiled binaries. Possible settings:

  * 0 – No randomization. Everything is static.
  * 1 – Conservative randomization. Shared libraries, stack, mmap(), VDSO and heap are randomized.
  * 2 – Full randomization. In addition to elements listed in the previous point, memory managed through brk() is also randomized.


===== Checking and changing =====

Checking:

<code>
$ sysctl -a --pattern randomize
kernel.randomize_va_space = 2
$
</code>

Changing:

<code>
# echo 2 > /proc/sys/kernel/randomize_va_space
# sysctl -w kernel.randomize_va_space=2
</code>