Extra package: hardened_malloc

EL9

• Version hardened_malloc-12-3.el9_2.security
• Based on upstream version 12
• No plans to support older Rocky Linux versions due to glibc being too old

Package summary

This package ships the "normal" and "light" configurations of the GrapheneOS hardened_malloc project. The official README.md in the upstream project documents security properties and explains the differences between the regular and light variants.

Usage in Rocky Linux

It is strongly reccomended to read all documentation here before deploying this package on your infrastructure.

In order to support the large amount of mappings caused by guard slabs and large allocation guard regions, the vm.max_map_count sysctl is increased as part of package installation to 1048576 in /etc/sysctl.d/hardened_malloc.conf. You'll need to run sysctl -p /etc/sysctl.d/hardened_malloc.conf for this change to take effect without a reboot. Incidentally, Fedora 39 made the same change, so it's not an exotic configuration.

The package ships 2 builds of hardened_malloc, the regular variant, which is located at /usr/lib64/libhardened_malloc.so and can be preloaded using the hardened_malloc_preload.sh script, and the light variant, which is located at /usr/lib64/libhardened_malloc-light.so and can be preloaded using the hardened_malloc_light_preload.sh script. The preload scripts add the relevant library to LD_PRELOAD and then load the desired binary, as shown in the following example: hardened_malloc_preload.sh cat /proc/self/maps.

Users may choose to set an OS-wide LD_PRELOAD with hardened_malloc. This can be done by adding the desired library, for example, /usr/lib64/libhardened_malloc.so, into your /etc/ld.so.preload. Be aware that for applications where AT_SECURE is set, this approach will not work.

It is suggested that if you wish to deploy hardened_malloc systemwide, that you deploy it in your LD_PRELOAD with the normal variant globally, and then for applications which are performance sensitive, or which fail with the normal variant, try them individually with the light variant using the preload script or by setting LD_PRELOAD within a systemd service namespace. If that does not resolve your issue, try disabling hardened_malloc by running the program in its own systemd service namespace.

Bugs uncovered by hardened_malloc

As with all infrastructure changes, ensure you test in your staging environment extensively before deploying into production. Many packages and projects suffer from memory corruption bugs, which when running under glibc are not encountered during operation, but which hardened_malloc uncovers. Some applications may crash during usage, completely break, or break when running with certain configurations. Bugs in packages are typically a result of upstream project bugs, and should be reported there. In some cases these bugs are fixed in later versions in the upstream project, in which case the bug is an issue with Rocky Linux, and should be reported to Rocky Linux and its upstream distribution, so that the patch may be included.

Package name	Latest version tested	Normal variant	Light variant
php	php-8.0.30-1.el9_2.x86_64	Broken	Broken
php	php-8.1.14-1.module+el9.2.0+15232+36037ab0.x86_64	Broken	Broken
sssd	sssd-2.8.2-3.el9_2.x86_64	Broken	Broken

Potential for issues with EDR

By nature of relying on LD_PRELOAD, if you have EDR software on your server, it may falsely send alerts when using hardened_malloc. If it doesn't, your EDR is probably terrible or misconfigured.

Change log

* Tue Nov 14 2023 Solar Designer <solar@openwall.com> 12-3
- Package hardened_malloc_light_preload.sh
- Disable arm64 building for now (fix didn't work)

* Wed Nov  8 2023 flawedworld <flawedworld@flawed.world> 12-2
- Set CONFIG_NATIVE to false
- Mark libraries as executable (change to 755 permissions)
- Add hardened_malloc_light_preload.sh
- Fix arm64 building

* Sat Oct 28 2023 flawedworld <flawedworld@flawed.world> 12-1
- Initial packaging for hardened_malloc version 12, co-authored-by
  Scott Shinn (atomicturtle) and Solar Designer