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https://github.com/cisco-open/camblet-driver

Linux Kernel module providing TLS, identity and running WASM
https://github.com/cisco-open/camblet-driver

camblet kernel tls

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Linux Kernel module providing TLS, identity and running WASM

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README 

        
# camblet-driver



[![Makefile CI](https://github.com/cisco-open/camblet-driver/actions/workflows/build.yml/badge.svg)](https://github.com/cisco-open/camblet-driver/actions/workflows/build.yml)



## Introduction



The *camblet-driver* is the supporting Linux kernel module for the [Camblet](https://github.com/cisco-open/camblet) system. It is capable of enhancing plain old TCP sockets in a frictionless way so that application developers can focus on their business logic instead of dealing with the complexity of TLS, mTLS, and other security-related concerns. It is doing this seamlessly, no code changes or re-compilations or re-deployments are required.



The features are the following:



- providing zero-trust identity for UNIX TCP sockets through mTLS

- access control, authorization and authentication (through OPA)

- providing frictionless TLS termination for those TCP sockets

- supporting every Linux-based machine (bare-metal, vanilla VM, Kubernetes, etc... you name it)



### Presentations



The early incarnation of this project was presented on KubeCon 2023 Amsterdam, Wasm Day, you can find the recording [here](https://www.youtube.com/watch?v=JSKNch6piyY). By that time the module was capable of running OPA -> Wasm compiled policies in the Kernel and those were exposed as an eBPF function from the kernel module.



## Which Wasm runtime?



The [wasm3](https://github.com/wasm3/wasm3) runtime was chosen since it is written in C and has minimal dependencies (except a C library) and it is extremely portable. In kernel space, there is no libc, but we maintain a fork of wasm3 which can run in kernel space as well (check the `third-party/wasm3/` submodule).



Current restrictions for kernel-space wasm3:



- no floating point support [can be soft-emulated if needed]

- no WASI support



## Development environment



Checkout the code before you start:



```bash

git clone --recurse-submodules https://github.com/cisco-open/camblet-driver.git

cd camblet-driver

```



### Lima



Our primary development environment is [Lima](https://lima-vm.io) since it supports x86_64 and ARM as well. The module was tested on Ubuntu and Arch Linux and requires kernel version 5.15 and upwards.



Install Lima itself, for example on macOS using `brew`:



```bash

brew install lima

```



Launch the default VM which is an Ubuntu and matches the host's architecture by default:



```bash

limactl start



# You may also start the VM with your user home mounted as writable with this one-liner:

limactl start --set '.mounts[0].writable=true' --tty=false

```



Setup the required dependencies in the VM:



```bash

lima # enter the VM

sudo apt update && sudo apt install make

make setup-vm

```



### Coding



We are using VSCode for development and the project ships with a `c_cpp_properties.json` file which contains the required paths for the kernel headers. The file is ARM specific from include path point-of-view so if you happen to run on x86_64 please replace the paths accordingly (arm64 -> x86, aarch64 -> x86_64).



We are respecting your `c_cpp_properties.json` file by not overriding it. Please copy the required parts to your file, if it is already present.



You will also need a Linux source bundle, to have full navigation in the source code. The easiest way is to run the `setup-dev-env` target after you already have created a working and configured VM in Lima (with `lima make setup-vm`). This target installs the necessary GCC cross-compilers for IntelliSense, clones the Linux repo, and configures the VSCode workspace accordingly:



```bash

# Start the VM if you haven't already

limactl start



# Setup the development environment

make setup-dev-env

```



## Build and run



*This assumes that you have created a development environment according to the previous section.*



Build the kernel modules(BearSSL and Camblet):



```bash

# Enter the VM

lima



# Build on all CPU cores parallelly

make -j$(nproc)

```



Load the kernel modules(BearSSL and Camblet):



```bash

make insmod

```



Unload the kernel modules(BearSSL and Camblet):



```bash

make rmmod

```



Follow the kernel logs:



```bash

make logs

```



Install the [CLI](https://github.com/cisco-open/camblet) for the kernel module:



```bash

# You can build the module on your workstation

git clone https://github.com/cisco-open/camblet.git

cd camblet

GOOS=linux make build



# But you need to run it in the VM, where the device is exposed

lima sudo build/camblet agent --policies-path $(pwd)/camblet.d/policies --services-path $(pwd)/camblet.d/services

```



Then follow the instructions [here](https://github.com/cisco-open/camblet#cli).



## TLS Termination



The kernel module can terminate TLS connections for ordinary TCP sockets (IPv4 or IPv6), and forward the plaintext traffic to a user space application.



Between two applications - both of them intercepted by this module - the traffic is always encrypted by [kTLS](https://docs.kernel.org/networking/tls-offload.html). If one of them is not intercepted by the module but supports the ChaCha20-Poly1305 AEAD - kTLS is used. Otherwise, the traffic is encrypted by BearSSL.



## Debugging



### Logging



Most of the logs of this module are on the debug level and can be shown using the [dynamic debug](https://www.kernel.org/doc/html/latest/admin-guide/dynamic-debug-howto.html) feature of the Linux kernel.



Use the following command to turn on debug-level logging for the module:



```bash

echo -n '-p; module camblet file opa.c  +pftl' | sudo tee /proc/dynamic_debug/control > /dev/null

```



### Kernel debugging environment



The kernel module can be traced for memory leaks and other issues with the help of fine tools, like [KASAN](https://www.kernel.org/doc/html/latest/dev-tools/kasan.html) and [Kmemleak](https://www.kernel.org/doc/html/latest/dev-tools/kmemleak.html).



To create a kernel debugging environment on Fedora, follow these steps:



```bash

limactl start --name fedora-debug template://fedora --vm-type vz --set '.mounts[0].writable=true'



# Enter the VM

limactl shell fedora-debug



sudo dnf update

sudo dnf install kernel-debug kernel-debug-devel



# Check the current debug kernel version, and set it as default (ls /boot/)

CURRENT_DEBUG_KERNEL=vmlinuz-6.8.7-200.fc39.aarch64+debug



sudo grubby --set-default ${CURRENT_DEBUG_KERNEL}

sudo grubby --update-kernel=${CURRENT_DEBUG_KERNEL} --args kmemleak=on kasan=on

sudo reboot

```



### Test mTLS



The kernel module offers TLS termination on certain ports selected by an [OPA](https://www.openpolicyagent.org) rule-set:



```bash

# Edit the rule-set

vim socket.rego



# Build and insert the module, then follow the logs

make

make insmod

make logs



# In another terminal start a server

lima python3 -m http.server --protocol HTTP/1.1



# In another terminal connect to the server (over plaintext, will be TLS terminated by the kernel)

lima curl -v http://localhost:8000

```



## Installation



It is also possible to manually install the kernel module with [DKMS](https://github.com/dell/dkms).



### DKMS Support



Linux kernel modules need to be built against a specified kernel version, this is when dynamic kernel module support, [DKMS](https://github.com/dell/dkms) comes in handy. The DKMS framework enables you to automatically re-build kernel modules into the current kernel tree as you upgrade your kernel, so you don't need to re-build them manually every time.



#### Install DKMS



Ensure that DKMS is installed on your system. You can typically install it using your distribution's package manager.



For example, on Debian-based systems:



```bash

sudo apt install dkms

```



On Red Hat compatible systems:



```bash

sudo dnf install --enablerepo epel dkms

```



On Amazon Linux:



```bash

sudo dnf install dkms

```



#### Prepare the Camblet kernel module



The Camblet can be installed with DKMS in the following way currently:



```bash

sudo git clone --recurse-submodule https://github.com/cisco-open/camblet-driver.git /usr/src/camblet-0.8.0/



# Add the kernel module to the DKMS source control

sudo dkms add -m camblet -v 0.8.0



# Build and install the kernel module against the current kernel version

sudo dkms install -m camblet -v 0.8.0



# Load the kernel module

sudo modprobe camblet



# Check the logs that the module got loaded

sudo dmesg -T

```



Un-installation is very simple as well:



```bash

# Unload the kernel module

sudo modprobe -r camblet



# Remove the kernel module from DKMS source control

sudo dkms uninstall -m camblet -v 0.8.0

sudo dkms remove -m camblet -v 0.8.0

```



### Debian package



The kernel module can be packaged into a Debian package with DKMS support, so kernel module re-builds are handled automatically.



#### Building the package for yourself



Prepare the build environment, if you want to build the package on your workstation:



```bash

sudo apt install debhelper

```



The package can be built with the following command:



```bash

make deb

```



The package can be installed with the following command:



```bash

sudo apt install ../camblet-driver_0.7.1-1_all.deb

```



### RPM package



The kernel module can be packaged into an RPM package with DKMS support, so kernel module re-builds are handled automatically.



#### Building the package for yourself



Prepare the build environment, if you want to build the package on your workstation:



```bash

sudo dnf install rpm-build

```



The package can be built with the following command:



```bash

make rpm

```



The package can be installed with the following command:



```bash

sudo dnf install ../camblet-driver-0.7.1-1.noarch.rpm

```



## Testing



We are using [bats-core](https://bats-core.readthedocs.io/en/stable/index.html) for running our tests.



```bash

make tests

```