This documentation contains instructions to use hardened_malloc memory allocator as the system's default memory allocator. These instructions apply to both musl and glibc C libraries on Unix-based and Unix-like systems.
hardened_malloc can also be used per-application and/or per-user, in which case root permissions are not required; this documentation focuses on system-wide usage of hardened_malloc, assumes root privileges, and assumes the compiled library will be located in a path readable and executable by all users of the system.
For the complete hardened_malloc documentation, visit its official documentation.
This documentation is also available in portable AsciiDoc format in my documentation source code repository.
Add vm.max_map_count = 1048576
to /etc/sysctl.conf
to accommodate
hardened_malloc's large amount of guard pages.
$ git clone https://github.com/GrapheneOS/hardened_malloc.git
$ cd hardened_malloc/
$ make <arguments>
CONFIG_N_ARENA=n
can be adjusted to increase parallel performance at the
expense of memory usage, or decrease memory usage at the expense of parallel performance, where
n
is a non-negative integer. Higher values prefer parallel performance,
whereas lower values prefer lower memory usage. Note that having too many arenas may cause memory
fragmentation and decrease system performance. The number of arenas has no impact on the security
properties of hardened_malloc.
Minimum | Maximum | Default |
---|---|---|
1 | 256 | 4 |
For extra security, CONFIG_SEAL_METADATA=true
can be used in order to control
whether
Memory Protection Keys
are used to disable access to all writable allocator state outside of the memory allocator code.
It's currently disabled by default due to a significant performance cost for this use case on
current-generation hardware. Whether or not this feature is enabled, the metadata is all contained
within an isolated memory region with high-entropy random guard regions around it.
For low-memory systems, VARIANT=light
can be used to compile the light variant of
hardened_malloc, which sacrifices some security for much less memory usage. This option still
produces a more hardened memory allocator than both the default musl and glibc allocators, despite
the security sacrifices over the full variant.
For all compile-time options, see the configuration section of hardened_malloc's extensive official documentation.
# cp out/libhardened_malloc.so <target path>
musl-based systems: Add LD_PRELOAD=<hardened_malloc path>
to
/etc/environment
glibc-based systems: Add <hardened_malloc path>
to
/etc/ld.so.preload