We were not deleting DNS entries from the hash map, so when it reached
the maximum capacity (12k entries), we couldn't allocate new entries,
resulting in events not being sent to userspace.
- Don't rename libbpf's bpf_map_def struct, and distribute the needed bpf
headers.
The bpf_map_def struct has been deprecated for quite some time now,
and it was been removed on >= 6.2 anyway.
We still need it, because we use gobpf.
- Improved compilation behaviour:
- We don't require the kernel sources anymore. We can just use the
kernel headers from the distribution.
- There's no need to copy the sources to the kernel tree, the modules
can be compiled from the ebpf_prog/ dir.
- Compiling against kernels 6.x seems to solve the problem we had with
VPNs, where connections were not intercepted with modules compiled
against 5.8, on kernels >= 5.19.
The modules has been tested on kernels 4.17, 5.4, 5.10, 5.15, 6.1 and
6.2 (kernel connections included).
Closes: #939
BPF_MAP_TYPE_PERCPU_ARRAY was introduced in kernel version 4.6, so with
latest changes to intercept processes we lost support for older kernels
< 4.6.
Now we work again for example on kernels 4.4.
Make use of kernel macros to decide for what architectures we compile
the modules.
On armv7l the connections module was failing due to iptunnel_xmit, so
exclude it from being compiled.
One can export ARCH=arm, ARCH=i386 or ARCH=arm64 to compile the modules
for these architectures, instead of hacing to edit the source files.
- Get cmdline arguments from kernel along with the absolute path to the
binary.
If the cmdline has more than 20 arguments, or one of the arguments is
longer than 256 bytes, get it from ProcFS.
- Improved stopping ebpf monitor method.
Improved process detections by monitoring new processes execution.
It allow us to know the path of a process before a socket is opened.
Closes#617
Other improvements:
- If we fail to retrieve the path of a process, then we'll use the comm
name of the connection/process.
- Better kernel connections detection.
- If debugfs is not loaded, we'll try to mount it, to allow to use
eBPF monitor method.
Future work (help wanted):
- Extract command line arguments from the kernel (sys_execve, or mm
struct).
- Monitor other functions (execveat, clone*, fork, etc).
- Send these events to the server (GUI), and display all the commands
an application has executed.
When using DoT or DoH opensnitch cannot intercept the dns packets.
Therefore the UI always shows IP addresses instead of hostnames. To fix
this issue an ebpf (uprobe) filter was created to hook getaddrinfo and
gethostbyname calls.
In order to be independent of libbcc an additional module was added to
ebpf_prog. Without libbcc the libc function offsets must be resolved
manually. In order to find the loaded glibc version some cgo code was
added.
* Allow to intercept some kernel connections
Some connections are initiated from kernel space, like WireGuard
VPNs (#454), NFS or SMB connections (#502) and ip tunnels (#500).
Note: This feature is complete for x86_64, WIP for aarch64, and not supported for armhf and i386
https://github.com/evilsocket/opensnitch/pull/513#issuecomment-924400824
More information regarding this change: #493
* Use ebpf program to find PID of new connections.
before running the branch you have to compile ebpf_prog/opensnitch.c
opensnitch.c is an eBPF program. Compilation requires getting kernel source.
cd opensnitch
wget https://github.com/torvalds/linux/archive/v5.8.tar.gz
tar -xf v5.8.tar.gz
patch linux-5.8/tools/lib/bpf/bpf_helpers.h < ebpf_prog/file.patch
cp ebpf_prog/opensnitch.c ebpf_prog/Makefile linux-5.8/samples/bpf
cd linux-5.8 && yes "" | make oldconfig && make prepare && make headers_install # (1 min)
cd samples/bpf && make
objdump -h opensnitch.o #you should see many section, number 1 should be called kprobe/tcp_v4_connect
llvm-strip -g opensnitch.o #remove debug info
sudo cp opensnitch.o /etc/opensnitchd
cd ../../../daemon
--opensnitchd expects to find opensnitch.o in /etc/opensnitchd/
--start opensnitchd with:
opensnitchd -rules-path /etc/opensnitchd/rules -process-monitor-method ebpf
Co-authored-by: themighty1 <you@example.com>
Co-authored-by: Gustavo Iñiguez Goia <gooffy1@gmail.com>
