git.scottworley.com Git - voter/blob - src/main.rs

   1 use rand::prelude::*;
   2 use std::io::prelude::*;
   3 use std::path::{Path, PathBuf};
   4
   5 const DATA_PATH: &str = "/var/lib/voter";
   6 const COOKIE_NAME: &[u8] = b"__Secure-id";
   7 const COOKIE_LENGTH: usize = 32;
   8
   9 fn validate_path(path: &str) -> Result<PathBuf, cgi::Response> {
  10     let invalid_path = || cgi::text_response(404, "Invalid path");
  11     if path == "/" {
  12         return Err(cgi::text_response(404, "(This is the voting place.  You should have been given a more specific URL for the specific thing you've been invited to vote on.)"));
  13     }
  14     if path.contains("..") || !path.starts_with("/") {
  15         return Err(invalid_path());
  16     }
  17     let dir = Path::new(&format!("{DATA_PATH}{path}")).to_path_buf();
  18     if !dir
  19         .canonicalize()
  20         .map_err(|_| invalid_path())?
  21         .starts_with(DATA_PATH)
  22     {
  23         return Err(invalid_path());
  24     }
  25     if !dir.is_dir() {
  26         return Err(invalid_path());
  27     }
  28     Ok(dir)
  29 }
  30
  31 fn get_voter(request: &cgi::Request) -> Result<&[u8], cgi::Response> {
  32     // Expect exactly one cookie, exactly as we generate it.
  33     let cookie = request
  34         .headers()
  35         .get(cgi::http::header::COOKIE)
  36         .map(|c| c.as_bytes())
  37         .and_then(|c| c.strip_prefix(COOKIE_NAME))
  38         .and_then(|c| c.strip_prefix(b"="))
  39         .ok_or_else(|| cgi::text_response(400, "Invalid cookie"))?;
  40     if cookie.len() != COOKIE_LENGTH || cookie.contains(&b' ') || cookie.contains(&b';') {
  41         Err(cgi::text_response(400, "Invalid cookie"))
  42     } else {
  43         Ok(cookie)
  44     }
  45 }
  46
  47 fn make_random_id() -> [u8; COOKIE_LENGTH] {
  48     std::iter::from_fn(random)
  49         .filter(|c| {
  50             (b'A'..=b'Z').contains(c) || (b'a'..=b'z').contains(c) || (b'0'..=b'9').contains(c)
  51         })
  52         .take(COOKIE_LENGTH)
  53         .collect::<Vec<_>>()
  54         .try_into()
  55         .unwrap()
  56 }
  57
  58 fn set_cookie(mut response: cgi::Response, path: &str) -> Result<cgi::Response, cgi::Response> {
  59     response.headers_mut().append(
  60         cgi::http::header::SET_COOKIE,
  61         cgi::http::header::HeaderValue::from_bytes(
  62             &[
  63                 COOKIE_NAME,
  64                 b"=",
  65                 &make_random_id(),
  66                 b"; Secure HttpOnly SameSite=Strict Max-Age=30000000 Path=",
  67                 path.as_bytes(),
  68             ]
  69             .concat(),
  70         )
  71         .map_err(|_| cgi::text_response(503, "Couldn't make cookie"))?,
  72     );
  73     Ok(response)
  74 }
  75
  76 fn prompt_for_vote(dir: PathBuf, request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
  77     let voter = get_voter(&request);
  78     let mut response = cgi::html_response(200, "<html><body>You should vote</body></html>");
  79     if voter.is_err() {
  80         response = set_cookie(response, request.uri().path())?
  81     }
  82     Ok(response)
  83 }
  84
  85 fn write_vote(dir: PathBuf, voter: &[u8], vote: &[u8]) -> std::io::Result<()> {
  86     let datum = [voter, b" ", vote, b"\n"].concat();
  87     let vpath = dir.join("votes");
  88     let vfile = std::fs::File::options()
  89         .append(true)
  90         .create(true)
  91         .open(vpath)?;
  92     let mut vlock = fd_lock::RwLock::new(vfile);
  93     vlock.write()?.write(&datum)?;
  94     Ok(())
  95 }
  96
  97 fn record_vote(dir: PathBuf, request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
  98     let body = request.body();
  99     // Valid votes look like "0 foo" or "1 bar"
 100     if body.len() < 3
 101         || (body[0] != b'0' && body[0] != b'1')
 102         || body[1] != b' '
 103         || body.contains(&b'\n')
 104     {
 105         return Err(cgi::text_response(415, "Invalid vote"));
 106     }
 107     write_vote(dir, &get_voter(&request)?, body)
 108         .map_err(|_| cgi::text_response(503, "Couldn't record vote"))?;
 109     Ok(cgi::text_response(200, "Vote recorded"))
 110 }
 111
 112 fn strip_body(mut response: cgi::Response) -> cgi::Response {
 113     response.body_mut().clear();
 114     response
 115 }
 116
 117 fn respond(request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
 118     let dir = validate_path(request.uri().path())?;
 119     match request.method() {
 120         &cgi::http::Method::HEAD => prompt_for_vote(dir, request).map(strip_body),
 121         &cgi::http::Method::GET => prompt_for_vote(dir, request),
 122         &cgi::http::Method::PUT => record_vote(dir, request),
 123         _ => Err(cgi::text_response(405, "Huh?")),
 124     }
 125 }
 126
 127 fn respond_or_report_error(request: cgi::Request) -> cgi::Response {
 128     match respond(request) {
 129         Ok(result) => result,
 130         Err(error) => error,
 131     }
 132 }
 133
 134 cgi::cgi_main! { respond_or_report_error }