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A place to store my toy linux-security modules.
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README.md

README.md

Linux Security Modules

This repository contains a simple collection of linux security modules, which were written as a learning/experimentation-process.

Modules

There are three modules contained within this repository, two of which are simple tests and one of which is more "real".

These are test-modules:

  • whitelist
    • Only allow execution of binaries which have a specific xattr present.
  • hashcheck
    • Only allow execution of commands with xattr containing valid SHA1sum of binaries.
    • This builds upon the previous module.

This is the only "real" module:

  • can-exec
    • The the user-space helper /sbin/can-exec is invoked to determine whether a user can execute a specific command.
    • Because user-space controls execution policies can be written/updated dynamically.

Linux Compatibility & Compilation

The code has been tested upon kernels as recent as 5.1

Copy the contents of security/ into your local Kernel-tree, and run make menuconfig to enable the appropriate options.

NOTE: Over time the two files security/Kconfig & security/Makefile might need resyncing with the base versions installed with the Linux source-tree, you can look for mentions of CAN_EXEC, HASH_CHECK, & WHITELIST to see what I've done to add the modules.

For a Debian GNU/Linux host, building a recent kernel, these are the dependencies you'll need to install:

  # apt-get install flex bison bc libelf-dev libssl-dev \
                    build-essential make libncurses5-dev \
                    git-core

Documentation

I wrote a couple of blog posts which might provide more background, and they are listed below (in order oldest to most recent):

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