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Merged
maheshbhatiya73 merged 1 commit into from
Jul 10, 2025
Merged

feat(ssh-fail-monitor): add kprobe-based sshd detection #11

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1 change: 1 addition & 0 deletions .gitignore
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# Binaries and object files
bin/
*.o
*.elf

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Binary file modified bin/ssh_monitor.o
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21 changes: 21 additions & 0 deletions cmd/ssh_fail.go
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package cmd

import (
"fmt"
"netbarrier/core"

"github.com/spf13/cobra"
)

var sshFailCmd = &cobra.Command{
Use: "ssh-fail-monitor",
Short: "Run SSH failed login monitor using eBPF",
Run: func(cmd *cobra.Command, args []string) {
fmt.Println("Running SSH Fail Monitor")
core.RunSSHFailMonitor()
},
}

func init() {
rootCmd.AddCommand(sshFailCmd)
}
155 changes: 155 additions & 0 deletions core/ssh_fail_monitor.go
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package core

import (
"bytes"
"encoding/binary"
"fmt"
"log"
"os"
"os/signal"
"os/user"
"strings"
"sync"

"github.com/cilium/ebpf"
"github.com/cilium/ebpf/link"
"github.com/cilium/ebpf/ringbuf"
)

type sshFailEvent struct {
Pid uint32
Uid uint32
TimestampNs uint64
Comm [16]byte
FailReason uint8
_ [7]byte // padding
}

var attemptCount = struct {
sync.Mutex
data map[uint32]int // map[PID] -> count
}{
data: make(map[uint32]int),
}

func RunSSHFailMonitor() {
spec, err := ebpf.LoadCollectionSpec("bin/ssh_fail_monitor.o")
if err != nil {
log.Fatalf("Failed to load eBPF spec: %v", err)
}

objs := struct {
SshFailMonitor *ebpf.Program `ebpf:"ssh_fail_monitor"`
SshFailRingbuf *ebpf.Map `ebpf:"SSH_FAIL_RINGBUF"`
}{}

if err := spec.LoadAndAssign(&objs, nil); err != nil {
log.Fatalf("Failed to load eBPF objects: %v", err)
}
defer func() {
_ = objs.SshFailMonitor.Close()
_ = objs.SshFailRingbuf.Close()
}()

libpamPath := findLibPam()
if libpamPath == "" {
log.Fatal("libpam.so not found")
}
log.Printf("Using libpam at: %s", libpamPath)

up, err := link.OpenExecutable(libpamPath)
if err != nil {
log.Fatalf("OpenExecutable failed: %v", err)
}

attached, err := up.Uretprobe("pam_authenticate", objs.SshFailMonitor, nil)
if err != nil {
log.Fatalf("Failed to attach uretprobe: %v", err)
}
defer attached.Close()

log.Println("Successfully attached uretprobe to pam_authenticate")

rd, err := ringbuf.NewReader(objs.SshFailRingbuf)
if err != nil {
log.Fatalf("Failed to open ringbuf reader: %v", err)
}
defer rd.Close()

log.Println("SSH fail monitor started. Press Ctrl+C to stop.")
sig := make(chan os.Signal, 1)
done := make(chan struct{})
signal.Notify(sig, os.Interrupt)

go func() {
for {
select {
case <-done:
return
default:
record, err := rd.Read()
if err != nil {
if !strings.Contains(err.Error(), "closed") {
log.Printf("ringbuf read failed: %v", err)
}
continue
}

var event sshFailEvent
if err := binary.Read(bytes.NewBuffer(record.RawSample), binary.LittleEndian, &event); err != nil {
log.Printf("binary read failed: %v", err)
continue
}

username := lookupUsername(event.Uid)
processName := strings.TrimRight(string(event.Comm[:]), "\x00")
reason := "unknown"
switch event.FailReason {
case 1:
reason = "invalid password"
case 2:
reason = "invalid user"
}

attemptCount.Lock()
attemptCount.data[event.Pid]++
count := attemptCount.data[event.Pid]
attemptCount.Unlock()

fmt.Printf(
"%s (PID %d, UID %d, user: %s) → Failed SSH login: %s [Attempt #%d]\n",
processName, event.Pid, event.Uid, username, reason, count,
)
}
}
}()

<-sig
fmt.Println("\nExiting SSH monitor.")
close(done)
}

func lookupUsername(uid uint32) string {
userObj, err := user.LookupId(fmt.Sprintf("%d", uid))
if err != nil {
return "unknown"
}
return userObj.Username
}

func findLibPam() string {
possiblePaths := []string{
"/lib/x86_64-linux-gnu/libpam.so.0",
"/lib64/libpam.so.0",
"/usr/lib/libpam.so.0",
"/usr/lib64/libpam.so.0",
"/lib/libpam.so.0",
}

for _, path := range possiblePaths {
if _, err := os.Stat(path); err == nil {
return path
}
}
return ""
}
18 changes: 18 additions & 0 deletions ebpf-programs/ssh_fail_monitor/Cargo.toml
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[package]
name = "ssh_fail_monitor"
version = "0.1.0"
edition = "2021"

[lib]
crate-type = ["staticlib"]
name = "ssh_fail_monitor"

[dependencies]
aya-ebpf = { version = "0.1.1", default-features = false }

[profile.release]
opt-level = "z"
lto = true
panic = "abort"
codegen-units = 1
strip = "debuginfo"
4 changes: 4 additions & 0 deletions ebpf-programs/ssh_fail_monitor/rust-toolchain.toml
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[toolchain]
channel = "nightly"
components = ["rust-src"]
targets = ["bpfel-unknown-none"]
96 changes: 96 additions & 0 deletions ebpf-programs/ssh_fail_monitor/src/lib.rs
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#![no_std]
#![no_main]

use aya_ebpf::{
macros::map,
maps::{HashMap, RingBuf},
programs::ProbeContext,
helpers::{
bpf_get_current_pid_tgid,
bpf_get_current_uid_gid,
bpf_get_current_comm,
bpf_ktime_get_ns,
},
EbpfContext,
cty::c_int,
};
use aya_ebpf::bpf_printk;

#[repr(C)]
#[derive(Clone, Copy)]
pub struct SshFailEvent {
pub pid: u32,
pub uid: u32,
pub timestamp_ns: u64,
pub comm: [u8; 16],
pub ret_code: i32,
_padding: [u8; 3],
}

#[map(name = "SSH_FAIL_RINGBUF")]
static mut SSH_FAIL_RINGBUF: RingBuf = RingBuf::with_byte_size(4096, 0);

#[map(name = "SSH_FAIL_COUNTS")]
static mut SSH_FAIL_COUNTS: HashMap<u32, u32> =
HashMap::<u32, u32>::with_max_entries(1024, 0);

#[no_mangle]
#[link_section = "uretprobe/pam_authenticate"]
pub fn ssh_fail_monitor(ctx: ProbeContext) -> u32 {
let _ = try_monitor(ctx);
0
}

fn try_monitor(ctx: ProbeContext) -> Result<(), ()> {
// SAFELY extract return value from `ctx`

let ret_val = unsafe { *(ctx.as_ptr() as *const c_int) };
unsafe {
bpf_printk!(b"ssh_fail_monitor: ret_val seen\n");
}
if ret_val == 0 {
return Ok(());
}

let pid = (bpf_get_current_pid_tgid() >> 32) as u32;
let uid = (bpf_get_current_uid_gid() >> 32) as u32;


unsafe {
bpf_printk!(b"[ssh_fail] processing event\n");
}

let mut comm = [0u8; 16];
if let Ok(val) = bpf_get_current_comm() {
comm.copy_from_slice(&val);
}

let ts = unsafe { bpf_ktime_get_ns() };

let event = SshFailEvent {
pid,
uid,
timestamp_ns: ts,
comm,
ret_code: ret_val,
_padding: [0; 3],
};

unsafe {
let count = SSH_FAIL_COUNTS.get(&pid).copied().unwrap_or(0);
SSH_FAIL_COUNTS.insert(&pid, &(count + 1), 0).ok();
SSH_FAIL_RINGBUF.output(&event, 0);
bpf_printk!(b"[ssh_fail] event emitted\n");
}

Ok(())
}

#[panic_handler]
fn panic(_: &core::panic::PanicInfo) -> ! {
loop {}
}

#[no_mangle]
#[link_section = "license"]
pub static LICENSE: [u8; 4] = *b"GPL\0";
4 changes: 2 additions & 2 deletions ebpf-programs/ssh_monitor/Cargo.toml
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[package]
name = "ssh_monitor_ebpf"
name = "ssh_monitor"
version = "0.1.0"
edition = "2021"

[lib]
crate-type = ["staticlib"]
name = "ssh_monitor_ebpf"
name = "ssh_monitor"

[dependencies]
aya-ebpf = { version = "0.1.1", default-features = false }
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