From 9f17d6c2e125598c27379ba1d5e7c1b35ffc4a6c Mon Sep 17 00:00:00 2001
From: William Brawner <me@wbrawner.com>
Date: Wed, 27 Jul 2022 21:18:25 -0600
Subject: [PATCH] Add telnet command

---
 Cargo.lock  |  7 +++++++
 Cargo.toml  |  1 +
 src/main.rs | 43 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 51 insertions(+)

diff --git a/Cargo.lock b/Cargo.lock
index 60d246d..c493a8a 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -25,6 +25,7 @@ name = "gsm-agent"
 version = "0.1.0"
 dependencies = [
  "minreq",
+ "telnet",
 ]
 
 [[package]]
@@ -148,6 +149,12 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "telnet"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "99f2cc260bea5219955ab4832c9600a41b87101d280939edae6dd10b3c68a4f3"
+
 [[package]]
 name = "unicode-ident"
 version = "1.0.2"
diff --git a/Cargo.toml b/Cargo.toml
index 10555ec..a5e0167 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -10,3 +10,4 @@ lto = true
 
 [dependencies]
 minreq = { version = "2.6.0", features = ["https"] }
+telnet = "0.2.1"
diff --git a/src/main.rs b/src/main.rs
index c0a0c62..1533095 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -8,8 +8,11 @@ use std::net::TcpListener;
 use std::net::TcpStream;
 use std::path::Path;
 use std::process::Command;
+use std::time::Duration;
 
 use gsm_agent::ThreadPool;
+use telnet::Event;
+use telnet::Telnet;
 
 fn main() {
     let listener = TcpListener::bind("127.0.0.1:4762").unwrap();
@@ -68,6 +71,38 @@ where
     String::from_utf8(Command::new(command).args(args).output().unwrap().stdout).unwrap()
 }
 
+fn telnet(stream: &mut TcpStream, host: &str, port: &u16) -> Result<String, std::io::Error> {
+    let mut telnet = Telnet::connect((host, *port), 4096)?;
+    let mut stream_buffer = [0; 4096];
+    stream.set_read_timeout(Some(Duration::new(1, 0)))?;
+    'main: loop {
+        match stream.read(&mut stream_buffer) {
+            Ok(read) => {
+                match String::from_utf8_lossy(&stream_buffer[0..read])
+                    .as_ref()
+                    .trim()
+                {
+                    "quit" => break 'main,
+                    _ => telnet.write(&stream_buffer[0..read]).unwrap(),
+                };
+            }
+            Err(_) => {}
+        };
+        match telnet.read_timeout(Duration::new(1, 0)) {
+            Ok(event) => {
+                if let Event::Data(buffer) = event {
+                    stream.write(&buffer).unwrap();
+                }
+            }
+            Err(e) => {
+                println!("telnet read error: {:?}\n", e);
+                break 'main;
+            }
+        }
+    }
+    Ok(String::from("Telnet connection closed"))
+}
+
 fn handle_connection(mut stream: TcpStream) {
     loop {
         let mut buffer = [0; 1024];
@@ -104,6 +139,14 @@ fn handle_connection(mut stream: TcpStream) {
                     "ping" => String::from("pong"),
                     "pwd" => pwd(),
                     "shell" => shell(command_iter.next().unwrap(), command_iter),
+                    "telnet" => {
+                        let host = command_iter.next().unwrap();
+                        let port = u16::from_str_radix(command_iter.next().unwrap(), 10).unwrap();
+                        match telnet(&mut stream, host, &port) {
+                            Ok(s) => s,
+                            Err(e) => e.to_string(),
+                        }
+                    }
                     _ => {
                         format!(
                             "unknown command: {:?}",