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use std::net::{SocketAddr,UdpSocket};
use std::fs::File;
use std::path::Path;
use std::env;
use std::io;
use std::io::prelude::*;
fn handle_wrq(_cl: &SocketAddr, _buf: &[u8]) -> Result<(), io::Error> {
Ok(())
}
fn wait_for_ack(sock: &UdpSocket, expected_block: u16) -> Result<bool, io::Error> {
let mut buf = [0; 4];
sock.recv(&mut buf)?;
let opcode = u16::from_be_bytes([buf[0], buf[1]]);
let block_nr = u16::from_be_bytes([buf[2], buf[3]]);
if opcode == 4 && block_nr == expected_block {
return Ok(true)
}
Ok(false)
}
fn send_file(cl: &SocketAddr, filename: &str) -> Result<(), io::Error> {
let file = File::open(filename);
let mut file = match file {
Ok(f) => f,
Err(ref error) if error.kind() == io::ErrorKind::NotFound => {
handle_error(cl, 1, "File not found")?;
return Err(io::Error::new(io::ErrorKind::NotFound, "file not found"));
},
Err(_) => {
handle_error(cl, 2, "Permission denied")?;
return Err(io::Error::new(io::ErrorKind::PermissionDenied, "permission denied"));
}
};
if !file.metadata()?.is_file() {
handle_error(cl, 1, "File not found")?;
return Err(io::Error::new(io::ErrorKind::NotFound, "file not found"));
}
let socket = UdpSocket::bind("0.0.0.0:0")?;
socket.connect(cl)?;
let mut block_nr: u16 = 1;
loop {
let mut filebuf = [0; 512];
let len = file.read(&mut filebuf);
let len = match len {
Ok(n) => n,
Err(ref error) if error.kind() == io::ErrorKind::Interrupted => continue, /* retry */
Err(err) => {
handle_error(cl, 0, "File reading error")?;
return Err(err);
}
};
let mut sendbuf = vec![0x00, 0x03]; // opcode
sendbuf.extend(block_nr.to_be_bytes().iter());
sendbuf.extend(filebuf[0..len].iter());
socket.send(&sendbuf)?;
for _ in 1..5 {
match wait_for_ack(&socket, block_nr) {
Ok(true) => break,
Ok(false) => continue,
Err(e) => return Err(e),
};
}
if len < 512 {
/* this was the last block */
break;
}
/* increment with rollover on overflow */
block_nr = block_nr.wrapping_add(1);
}
Ok(())
}
fn file_allowed(filename: &str) -> bool {
let path = Path::new(".").join(&filename);
let path = match path.parent() {
Some(p) => p,
None => return false,
};
let path = match path.canonicalize() {
Ok(p) => p,
Err(_) => return false,
};
let cwd = match env::current_dir() {
Ok(p) => p,
Err(_) => return false,
};
return path.starts_with(cwd);
}
fn handle_rrq(cl: &SocketAddr, buf: &[u8]) -> Result<(), io::Error> {
let mut iter = buf.iter();
let dataerr = io::Error::new(io::ErrorKind::InvalidData, "invalid data received");
let fname_len = iter.position(|&x| x == 0);
let fname_len = match fname_len {
Some(len) => len,
None => return Err(dataerr),
};
let fname_begin = 0;
let fname_end = fname_begin + fname_len;
let filename = String::from_utf8(buf[fname_begin .. fname_end].to_vec());
let filename = match filename {
Ok(fname) => fname,
Err(_) => return Err(dataerr),
};
let mode_len = iter.position(|&x| x == 0);
let mode_len = match mode_len {
Some(len) => len,
None => return Err(dataerr),
};
let mode_begin = fname_end + 1;
let mode_end = mode_begin + mode_len;
let mode = String::from_utf8(buf[mode_begin .. mode_end].to_vec());
let mode = match mode {
Ok(m) => m.to_lowercase(),
Err(_) => return Err(dataerr),
};
match mode.as_ref() {
"octet" => (),
_ => handle_error(cl, 0, "Unsupported mode")?,
}
match file_allowed(&filename) {
true => (),
false => {
handle_error(cl, 2, "Permission denied")?;
return Err(io::Error::new(io::ErrorKind::PermissionDenied, "permission denied"));
}
}
match send_file(&cl, &filename) {
Ok(_) => println!("Sent {} to {}.", filename, cl),
Err(_) => println!("Sending {} to {} failed.", filename, cl),
}
Ok(())
}
fn handle_error(cl: &SocketAddr, code: u16, msg: &str) -> Result<(), io::Error> {
let socket = UdpSocket::bind("0.0.0.0:0")?;
socket.connect(cl)?;
let mut buf = vec![0x00, 0x05]; // opcode
buf.extend(code.to_be_bytes().iter());
buf.extend(msg.as_bytes());
socket.send(&buf)?;
Ok(())
}
fn handle_client(cl: &SocketAddr, buf: &[u8]) -> Result<(), io::Error> {
let opcode = u16::from_be_bytes([buf[0], buf[1]]);
match opcode {
1 /* RRQ */ => handle_rrq(&cl, &buf[2..])?,
2 /* WRQ */ => handle_wrq(&cl, &buf[2..])?,
5 /* ERROR */ => println!("Received ERROR from {}", cl),
_ => handle_error(cl, 4, "Unexpected opcode")?,
}
Ok(())
}
fn main() {
let socket = UdpSocket::bind("127.0.0.1:12345").expect("Binding a socket failed.");
loop {
let mut buf = [0; 2048];
let (n, src) = socket.recv_from(&mut buf).expect("Receiving from the socket failed.");
match handle_client(&src, &buf[0..n]) {
/* errors intentionally ignored */
_ => (),
}
}
}
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