Framework for running BPF programs with rules on Linux as a daemon. Container aware.

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bpfd

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Framework for running BPF tracers with rules on Linux as a daemon. Container aware.

This is not just “yet another tool to trace”...

Since it uses BPF and allows for any implementation of the Tracer interface you can use it to do all sorts of things from modifying a file everytime a call to open is called on it, to hot patching an internal kernel function to prevent a known vulnerability without the need to upgrade your kernel.

More use cases with examples coming soon... for now see how it works.

Table of Contents

How it Works

Tracers retrieve the data... Rules filter the data... Actions perform actions on the data.

The tracers are in the tracer/ folder. The idea is that you can add any tracers you would like and then create rules for the data retrieved from the tracers. Any events with data that passes the filters will be passed on to the specified action.

Tracers

The tracers that exist today are based off a few bcc-tools tracers.

You could always add your own tracers in a fork if you worry people will reverse engineer the data you are collecting and alerting on.

The current compiled in tracers are:

  • bashreadline: trace commands being entered into the bash command line
  • exec: trace calls to exec binaries
  • open: trace calls to open files

These must implement the Tracer interface:

// Tracer defines the basic capabilities of a tracer.
type Tracer interface {
    // Load creates the bpf module and starts collecting the data for the tracer.
    Load() error
    // Unload closes the bpf module and all the probes that all attached to it.
    Unload()
    // WatchEvent defines the function to watch the events for the tracer.
    WatchEvent() (*grpc.Event, error)
    // Start starts the map for the tracer.
    Start()
    // String returns a string representation of this tracer.
    String() string
}

As you can see from above you could technically implement this interface with something other than BPF ;)

The Event type defines the data returned from the tracer. As you can see below, the Data is of type map[string]string meaning any key value pair can be returned for the data. The rules then filter using those key value pairs.

// Event defines the data struct for holding event data.
type Event struct {
    PID              uint32            // Process ID.
    TGID             uint32            // Task group ID.
    Data             map[string]string
    ContainerRuntime string            // Filled in after the tracer is run so you don't need to.
    ContainerID      string            // Filled in after the tracer is run so you don't need to.
    Tracer           string            // Filled in after the tracer is run so you don't need to.
}

Rules

These are toml files that hold some logic for what you would like to trace. You can search for anything returned by a Tracer in its map[string]string data struct.

You can also filter based off the container runtime you would like to alert on. The container runtime must be one of the strings defined here.

If you provide no rules for a tracer, then all the events will be passed to actions.

The example below describes a rule file to filter the data returned from the exec tracer. Events from exec will only be returned if the command matches one of those values AND the container runtime is docker or kube.

tracer = "exec"

actions = ["stdout"]

[filterEvents]
  [filterEvents.command]
  values = ["sshd", "dbus-daemon-lau", "ping", "ping6", "critical-stack-", "pmmcli", "filemng", "PassengerAgent", "bwrap", "osdetect", "nginxmng", "sw-engine-fpm", "start-stop-daem"]

containerRuntimes = ["docker","kube"]

If you are wondering where the command key comes from, it's defined in the exec tracer here.

Rules can be dynamically controlled via bpfd's gRPC interface. The cli tool can also be used for creating rules dynamically, see create usage.

The protobuf protocol definition is defined in api/grpc/api.proto

To interact with the gRPC api you can use the --gpc-addr flag or the default is a sock at /run/bpfd/bpfd.sock.

Actions

Actions do “something” on an event. This way you can send filtered events to Slack, email, or even run arbitrary code. You could kill a container, pause a container, or checkpoint a container to restore it elsewhere without even having to login to a computer.

The current compiled in actions are:

Actions implement the Actions interface:

// Action performs an action on an event.
type Action interface {
    // Do runs the action on an event.
    Do(event *grpc.Event) error
    // String returns a string representation of this tracer.
    String() string
}

Installation

To build, you need to have libbcc installed SEE INSTRUCTIONS HERE

Binaries

For installation instructions from binaries please visit the Releases Page.

Via Go

$ go get github.com/jessfraz/bpfd

Via Docker

$ docker run --rm -it \
    --name bpfd \
    -v /lib/modules:/lib/modules:ro \
    -v /usr/src:/usr/src:ro \
    --privileged \
    r.j3ss.co/bpfd daemon

Usage

$ bpfd -h
bpfd -  Framework for running BPF tracers with rules on Linux as a daemon.

Usage: bpfd <command>

Flags:

  -d, --debug  enable debug logging (default: false)
  --grpc-addr  Address for gRPC api communication (default: /run/bpfd/bpfd.sock)

Commands:

  create   Create one or more rules.
  daemon   Start the daemon.
  ls       List rules.
  rm       Remove one or more rules.
  trace    Live trace the events returned after filtering.
  version  Show the version information.

Run the daemon

You can preload rules by passing --rules-dir to the command or placing rules in the default directory: /etc/bpfd/rules.

$ bpfd daemon -h
Usage: bpfd daemon [OPTIONS]

Start the daemon.

Flags:

  -d, --debug  enable debug logging (default: false)
  --grpc-addr  Address for gRPC api communication (default: /run/bpfd/bpfd.sock)
  --rules-dir  Directory that stores the rules files (default: /etc/bpfd/rules)

Create rules dynamically

You can create rules on the fly with the create command. You can pass more than one file at a time.

Usage: bpfd create [OPTIONS] RULE_FILE [RULE_FILE...]

Create one or more rules.

Flags:

  -d, --debug  enable debug logging (default: false)
  --grpc-addr  Address for gRPC api communication (default: /run/bpfd/bpfd.sock)

Remove rules dynamically

You can delete rules with the rm command. You can pass more than one rule name at a time.

$ bpfd rm -h
Usage: bpfd rm [OPTIONS] RULE_NAME [RULE_NAME...]

Remove one or more rules.

Flags:

  -d, --debug  enable debug logging (default: false)
  --grpc-addr  Address for gRPC api communication (default: /run/bpfd/bpfd.sock)

List active rules

You can list the rules that the daemon is filtering with by using the ls command.

$ bpfd ls
NAME                TRACER
bashreadline        bashreadline
password_files      open
setuid_binaries     exec

Live tracing events

You can live trace the events returned after filtering with the trace command.

This does not include past events. Consider it like a tail.

$ bpfd trace
INFO[0000] map[string]string{"filename":"/etc/shadow", "command":"sudo", "returnval":"4"}  container_id= container_runtime=not-found pid=12893 tracer=open tgid=0
INFO[0000] map[string]string{"command":"sudo", "returnval":"4", "filename":"/etc/sudoers.d/README"}  container_id= container_runtime=not-found pid=12893 tracer=open tgid=0
INFO[0000] map[string]string{"command":"sudo", "returnval":"4", "filename":"/etc/sudoers.d"}  container_id= container_runtime=not-found pid=12893 tracer=open tgid=0
INFO[0000] map[string]string{"filename":"/etc/sudoers", "command":"sudo", "returnval":"3"}  container_id= container_runtime=not-found pid=12893 tracer=open tgid=0
INFO[0000] map[string]string{"command":"sudo bpfd trace"}  container_id= container_runtime=not-found pid=23751 tracer=bashreadline tgid=0
INFO[0000] map[string]string{"command":"vim README.md"}  container_id= container_runtime=not-found pid=23751 tracer=bashreadline tgid=0
INFO[0000] map[string]string{"filename":"/etc/shadow", "command":"sudo", "returnval":"4"}  container_id= container_runtime=not-found pid=12786 tracer=open tgid=0
INFO[0000] map[string]string{"command":"sudo", "returnval":"4", "filename":"/etc/sudoers.d/README"}  container_id= container_runtime=not-found pid=12786 tracer=open tgid=0
INFO[0000] map[string]string{"filename":"/etc/sudoers.d", "command":"sudo", "returnval":"4"}  container_id= container_runtime=not-found pid=12786 tracer=open tgid=0
INFO[0000] map[string]string{"filename":"/etc/sudoers", "command":"sudo", "returnval":"3"}  container_id= container_runtime=not-found pid=12786 tracer=open tgid=0