falcosecurity/libs

As per the OSS Libraries Contribution Plan, this repository has been chosen to be the new home for libsinsp, libscap, the kernel module and the eBPF probe sources.
Refer to https://falco.org/blog/contribution-drivers-kmod-ebpf-libraries/ for more information.

These components are at the foundation of Falco and other projects that work with the same kind of data.

This component stack mainly operates on a data source: system calls. This data source is collected using either a kernel module or an eBPF probe, which we call drivers. On top of the drivers, libscap manages the data capture process, libsinsp enriches the data, and provides a rich set of API to consume the data. Furthermore, these two libraries also implement a plugin framework that extends this stack to potentially any other data sources.

An image is worth a thousand words, they say:

Project Layout

• driver/ contains kernel module and eBPF probe source code, so-called drivers.
• userspace/ contains libscap and libsinsp libraries code, plus chisels related code and common utilities.
  • libscap (aka lib for System CAPture) is the userspace library that directly communicates with the drivers, reading syscall events from the ring buffer (where drivers place them), and forwarding them up to libsinsp. Moreover, libscap implements OS state collection and supports reading/writing to scap files.
  • libsinsp (aka lib for System INSPection) receives events from libscap and enriches them with machine state: moreover, it performs events filtering with rule evaluation through its internal rule engine. Finally, it manages outputs.
  • chisels are just little Lua scripts to analyze an event stream and perform useful actions. In this subfolder, the backend code for chisels support can be found.
• proposals/ unexpectedly contains the list of proposals.
• cmake/modules/ contains modules to build external dependencies, plus the libscap and libsinsp ones; consumers (like Falco) use those modules to build the libs in their projects.

Versioning

This project uses two different versioning schemes for the libs and driver components. In particular, the driver versions are suffixed with +driver to distinguish them from the libs ones. Both adhere to the Semantic Versioning 2.0.0. You can find more detail about how we version those components in our release process documentation.

If you build this project from a git working directory, the main CMakeLists.txt will automatically compute the appropriate version for all components. Otherwise, if you use a source code copy with no the git information or pull the sources of the libs or the drivers directly in your project, it's up to you to correctly set the appropriate cmake variables (for example, -DFALCOSECURITY_LIBS_VERSION=x.y.z -DDRIVER_VERSION=a.b.c+driver).

Drivers officially supported architectures

Right now our drivers officially support the following architectures:

	Kernel module	eBPF probe	Modern eBPF probe
x86_64	>= 2.6	>= 4.14	WIP 👷
aarch64	>= 3.16	>= 4.17	WIP 👷
s390x	>= 2.6	>= 5.5	WIP 👷

For a list of supported syscalls through specific events, please refer to report.

Build

Libs relies upon cmake build system.
Lots of make targets will be available; the most important ones are:

• driver -> to build the kmod
• bpf -> to build the eBPF probe
• scap -> to build libscap
• sinsp -> to build libsinsp (depends upon scap target)
• scap-open -> to build a small libscap example to quickly test drivers (depends upon scap)

To start, first create and move inside build/ folder:

mkdir build && cd build

Bundled deps

The easiest way to build the project is to use BUNDLED_DEPS option, meaning that most of the dependencies will be fetched and compiled during the process:

cmake -DUSE_BUNDLED_DEPS=true -DCREATE_TEST_TARGETS=OFF ../
make sinsp

NOTE: take a break as this will take quite a bit of time (around 15 mins, dependent on the hardware obviously).

System deps

To build using the system deps instead, first, make sure to have all the needed packages installed.
Refer to https://falco.org/docs/getting-started/source/ for the list of dependencies.

Then, simply issue:

cmake ../
make sinsp

NOTE: using system libraries is useful to cut compile times down, as this way it will only build libs, and not all deps.
On the other hand, system deps version may have an impact, and we cannot guarantee everything goes smoothly while using them.

Build kmod

To build the kmod driver, you need your kernel headers installed. Again, check out the Falco documentation for this step.
Then it will be just a matter of running:

make driver

Build eBPF probe

To build the eBPF probe, you need clang and llvm packages.
Then, issue:

cmake -DBUILD_BPF=true ../
make bpf

WARNING: clang-7 is the oldest supported version to build our BPF probe, since it is the one used by our infrastructure.

Build modern eBPF probe

To build the modern eBPF probe, you need:

• a recent clang version (>=12).

• a recent bpftool version, typing bpftool gen you should see at least these features:

  Usage: bpftool gen object OUTPUT_FILE INPUT_FILE [INPUT_FILE...]    <---
         bpftool gen skeleton FILE [name OBJECT_NAME]                 <---
         bpftool gen help
  

  If you want to use the bpftool mirror repo, version 6.7 should be enough.

  If you want to compile it directly from the kernel tree you should pick at least the 5.13 tag.

• BTF exposed by your kernel, you can check it through ls /sys/kernel/btf/vmlinux. You should see this line:

  /sys/kernel/btf/vmlinux
  

• A kernel version >=5.8.

Then, issue:

cmake -DUSE_BUNDLED_DEPS=ON -DBUILD_LIBSCAP_MODERN_BPF=ON -DBUILD_LIBSCAP_GVISOR=OFF .. 
make ProbeSkeleton

Please note: these are not the requirements to use the BPF probe but to build it from source!

As you have seen the modern bpf probe has strict requirements to be built that maybe are not easy to satisfy on old machines. The workaround you can use is to build the probe skeleton on a recent machine and than link it during the building phase on an older machine. To do that you have to use the cmake variable MODERN_BPF_SKEL_DIR. Supposing you have built the skeleton under the directory /tmp/skel-dir, you should use the option in this way:

cmake -DUSE_BUNDLED_DEPS=ON -DBUILD_LIBSCAP_MODERN_BPF=ON -DMODERN_BPF_SKEL_DIR="/tmp/skel-dir" -DBUILD_LIBSCAP_GVISOR=OFF .. 

gVisor support

Libscap contains additional library functions to allow integration with system call events coming from gVisor. Compilation of this functionality can be disabled with -DBUILD_LIBSCAP_GVISOR=Off.

Test drivers

Libscap ships a small example that is quite handy to quickly check that drivers are working fine. Look at the scap-open program documentation.

Contribute

Any contribution is incredibly helpful and warmly accepted; be it code, documentation, or just ideas, please feel free to share it!
For a contribution guideline, refer to: https://github.com/falcosecurity/.github/blob/master/CONTRIBUTING.md.

Adding syscalls

Implementing new syscalls is surely one of the highest frequency requests.
While it is indeed important for libs to support as many syscalls as possible, most of the time it is not a high priority task.
But you can speed up things by opening a PR for it!
Luckily enough, a Falco blog post explains the process very thoroughly: https://falco.org/blog/falco-monitoring-new-syscalls/.

License

This project is licensed to you under the Apache 2.0 open source license. Some subcomponents might be licensed separately. You can find licensing notices here.