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Linux Kernel Runtime Integrity With eBPF

Table of Contents

KRIe is a research project that aims to detect Linux Kernel exploits with eBPF. KRIe is far from being a bulletproof strategy: from eBPF related limitations to post exploitation detections that might rely on a compromised kernel to emit security events, it is clear that a motivated attacker will eventually be able to bypass it. That being said, the goal of the project is to make attackers’ lives harder and ultimately prevent out-of-the-box exploits from working on a vulnerable kernel.

KRIe has been developed using CO-RE (Compile Once – Run Everywhere) so that it is compatible with a large range of kernel versions. If your kernel doesn’t export its BTF debug information, KRIe will try to download it automatically from BTFHub. If your kernel isn’t available on BTFHub, but you have been able to manually generate your kernel’s BTF data, you can provide it in the configuration file (see below).

System requirements

This project was developed on Ubuntu Focal 20.04 (Linux Kernel 5.15) and has been tested on older releases down to Ubuntu Bionic 18.04 (Linux Kernel 4.15).

  • golang 1.18+
  • (optional) Kernel headers are expected to be installed in lib/modules/$(uname -r), update the Makefile with their location otherwise.
  • (optional) clang & llvm 14.0.6+

Optional fields are required to recompile the eBPF programs.

Build

  1. Since KRIe was built using CORE, you shouldn’t need to rebuild the eBPF programs. That said, if you want still want to rebuild the eBPF programs, you can use the following command:
  1. To build KRIE, run:
  1. To install KRIE (copy to /usr/bin/krie) run:

Getting started

KRIe needs to run as root. Run sudo krie -h to get help.

# ~ krie -h
Usage:
krie [flags]

Flags:
--config string KRIe config file (default "./cmd/krie/run/config/default_config.yaml")
-h, --help help for krie

Configuration

## Log level, options are: panic, fatal, error, warn, info, debug or trace
log_level: debug

## JSON output file, leave empty to disable JSON output.
output: "/tmp/krie.json"

## BTF information for the current kernel in .tar.xz format (required only if KRIE isn't able to locate it by itself)
vmlinux: ""

## events configuration
events:
## action taken when an init_module event is detected
init_module: log

## action taken when an delete_module event is detected
delete_module: log

## action taken when a bpf event is detected
bpf: log

## action taken when a bpf_filter event is detected
bpf_filter: log

## action taken when a ptrace event is detected
ptrace: log

## action taken when a kprobe event is detected
kprobe: log

## action taken when a sysctl event is detected
sysctl:
action: log

## Default settings for sysctl programs (kernel 5.2+ only)
sysctl_default:
block_read_access: false
block_write_access: false

## Custom settings for sysctl programs (kernel 5.2+ only)
sysctl_parameters:
kernel/yama/ptrace_scope:
block_write_access: true
kernel/ftrace_enabled:
override_input_value_with: "1\n"

## action taken when a hooked_syscall_table event is detected
hooked_syscall_table: log

## action taken when a hooked_syscall event is detected
hooked_syscall: log

## kernel_parameter event configuration
kernel_parameter:
action: log
periodic_action: log
ticker: 1 # sends at most one event every [ticker] second(s)
list:
- symbol: system/kprobes_all_disarmed
expected_value: 0
size: 4
# - symbol: system/selinux_state
# expecte d_value: 256
# size: 2

# sysctl
- symbol: system/ftrace_dump_on_oops
expected_value: 0
size: 4
- symbol: system/kptr_restrict
expected_value: 0
size: 4
- symbol: system/randomize_va_space
expected_value: 2
size: 4
- symbol: system/stack_tracer_enabled
expected_value: 0
size: 4
- symbol: system/unprivileged_userns_clone
expected_value: 0
size: 4
- symbol: system/unprivileged_userns_apparmor_policy
expected_value: 1
size: 4
- symbol: system/sysctl_unprivileged_bpf_disabled
expected_value: 1
size: 4
- symbol: system/ptrace_scope
expected_value: 2
size: 4
- symbol: system/sysctl_perf_event_paranoid
expected_value: 2
size: 4
- symbol: system/kexe c_load_disabled
expected_value: 1
size: 4
- symbol: system/dmesg_restrict
expected_value: 1
size: 4
- symbol: system/modules_disabled
expected_value: 0
size: 4
- symbol: system/ftrace_enabled
expected_value: 1
size: 4
- symbol: system/ftrace_disabled
expected_value: 0
size: 4
- symbol: system/sysctl_protected_fifos
expected_value: 1
size: 4
- symbol: system/sysctl_protected_hardlinks
expected_value: 1
size: 4
- symbol: system/sysctl_protected_regular
expected_value: 2
size: 4
- symbol: system/sysctl_protected_symlinks
expected_value: 1
size: 4
- symbol: system/sysctl_unprivileged_userfaultfd
expected_value: 0
size: 4

## action to check when a regis ter_check fails on a sensitive kernel space hook point
register_check: log

Documentation

License

  • The golang code is under Apache 2.0 License.
  • The eBPF programs are under the GPL v2 License.

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