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

   1 use rand::prelude::*;
   2 use std::collections::{HashMap, HashSet};
   3 use std::io::prelude::*;
   4 use std::path::{Path, PathBuf};
   5
   6 const DATA_PATH: &str = "/var/lib/voter";
   7 const COOKIE_NAME: &[u8] = b"__Secure-id";
   8 const COOKIE_LENGTH: usize = 12;
   9
  10 fn validate_path(path: &str) -> Result<PathBuf, cgi::Response> {
  11     let invalid_path = || cgi::text_response(404, "Invalid path");
  12     if path == "/" {
  13         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.)"));
  14     }
  15     if path.contains("..") || !path.starts_with("/") {
  16         return Err(invalid_path());
  17     }
  18     let dir = Path::new(&format!("{DATA_PATH}{path}")).to_path_buf();
  19     if !dir
  20         .canonicalize()
  21         .map_err(|_| invalid_path())?
  22         .starts_with(DATA_PATH)
  23     {
  24         return Err(invalid_path());
  25     }
  26     if !dir.is_dir() {
  27         return Err(invalid_path());
  28     }
  29     Ok(dir)
  30 }
  31
  32 fn get_voter(request: &cgi::Request) -> Result<&[u8], cgi::Response> {
  33     // Expect exactly one cookie, exactly as we generate it.
  34     let cookie = request
  35         .headers()
  36         .get(cgi::http::header::COOKIE)
  37         .map(|c| c.as_bytes())
  38         .and_then(|c| c.strip_prefix(COOKIE_NAME))
  39         .and_then(|c| c.strip_prefix(b"="))
  40         .ok_or_else(|| cgi::text_response(400, "Invalid cookie"))?;
  41     if cookie.len() != COOKIE_LENGTH || cookie.contains(&b' ') || cookie.contains(&b';') {
  42         Err(cgi::text_response(400, "Invalid cookie"))
  43     } else {
  44         Ok(cookie)
  45     }
  46 }
  47
  48 fn tally_votes(dir: PathBuf) -> std::io::Result<HashMap<String, HashSet<String>>> {
  49     let mut tally: HashMap<String, HashSet<String>> = HashMap::new();
  50     let vfile = std::fs::File::open(dir.join("votes"))?;
  51     for liner in std::io::BufReader::new(vfile).lines() {
  52         let line = liner?;
  53         if let Some((voter, datum)) = line.split_once(' ') {
  54             if voter.len() == COOKIE_LENGTH {
  55                 if let Some((vote, candidate)) = datum.split_once(' ') {
  56                     if vote == "0" {
  57                         if let Some(entry) = tally.get_mut(candidate) {
  58                             entry.remove(voter);
  59                         }
  60                     } else if vote == "1" {
  61                         tally
  62                             .entry(candidate.to_owned())
  63                             .or_default()
  64                             .insert(voter.to_owned());
  65                     }
  66                 }
  67             }
  68         }
  69     }
  70     Ok(tally)
  71 }
  72
  73 fn make_random_id() -> [u8; COOKIE_LENGTH] {
  74     let mut id = [0; COOKIE_LENGTH];
  75     for i in 0..COOKIE_LENGTH {
  76         while !(b'A'..=b'Z').contains(&id[i])
  77             && !(b'a'..=b'z').contains(&id[i])
  78             && !(b'0'..=b'9').contains(&id[i])
  79         {
  80             id[i] = random()
  81         }
  82     }
  83     id
  84 }
  85
  86 fn set_cookie(mut response: cgi::Response, path: &str) -> Result<cgi::Response, cgi::Response> {
  87     response.headers_mut().append(
  88         cgi::http::header::SET_COOKIE,
  89         cgi::http::header::HeaderValue::from_bytes(
  90             &[
  91                 COOKIE_NAME,
  92                 b"=",
  93                 &make_random_id(),
  94                 b"; Secure HttpOnly SameSite=Strict Max-Age=30000000 Path=",
  95                 path.as_bytes(),
  96             ]
  97             .concat(),
  98         )
  99         .map_err(|_| cgi::text_response(503, "Couldn't make cookie"))?,
 100     );
 101     Ok(response)
 102 }
 103
 104 const HTML_HEADER: &str = "<!DOCTYPE html>
 105 <html>
 106   <head>
 107     <meta charset=\"utf-8\">
 108     <title>Vote!</title>
 109     <style>
 110       th { font-size: 70%; text-align: left }
 111       input { transform: scale(1.5) }
 112       div { animation: 2s infinite linear spin }
 113       @keyframes spin {
 114         from { transform:rotate(0) }
 115         to { transform:rotate(1turn) }
 116       }
 117     </style>
 118     <script>
 119       window.onload = function() {
 120         for (cb of document.getElementsByTagName('input')) {
 121           cb.addEventListener('click', (function(cb) {
 122             return function() {
 123               cb.style.display = 'none'
 124               const spin = document.createElement('div')
 125               spin.appendChild(document.createTextNode('⏳'))
 126               cb.parentElement.insertBefore(spin, cb)
 127
 128               const req = new XMLHttpRequest()
 129               req.addEventListener('load', function(e) {
 130                 cb.parentElement.removeChild(cb.previousElementSibling)
 131                 if (req.status == 200) {
 132                     cb.style.display = ''
 133                 } else {
 134                    cb.parentElement.insertBefore(document.createTextNode('❗'), cb)
 135                 }
 136               })
 137               req.open('PUT', window.location.href)
 138               req.send((cb.checked ? 1 : 0) + ' ' + cb.parentElement.nextElementSibling.innerHTML)
 139             }
 140           })(cb))
 141           cb.disabled = false
 142         }
 143       }
 144     </script>
 145   </head>
 146   <body>
 147     <table>
 148       <tr>
 149         <th>Vote</th>
 150         <th>Candidate</th>
 151       </tr>";
 152 const HTML_FOOTER: &str = "
 153     </table>
 154   </body>
 155 </html>";
 156
 157 fn supports(tally: &HashMap<String, HashSet<String>>, me: &str, candidate: &str) -> bool {
 158     tally
 159         .get(candidate)
 160         .map(|supporters| supporters.contains(me))
 161         .unwrap_or(false)
 162 }
 163
 164 fn prompt_for_vote(dir: PathBuf, request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
 165     let voter = get_voter(&request);
 166     let me = if let Ok(id) = voter {
 167         std::str::from_utf8(id).ok()
 168     } else {
 169         None
 170     };
 171     let tally =
 172         tally_votes(dir.clone()).map_err(|_| cgi::text_response(503, "Couldn't tally votes"))?;
 173     let cfile = std::fs::File::open(dir.join("candidates"))
 174         .map_err(|_| cgi::text_response(503, "No candidates"))?;
 175     let mut response = cgi::html_response(
 176         200,
 177         std::iter::once(Ok(HTML_HEADER.to_owned()))
 178             .chain(std::io::BufReader::new(cfile).lines().map(|rc| {
 179                 rc.map(|c| {
 180                     let checked = if me.map(|me| supports(&tally, me, &c)).unwrap_or(false) {
 181                         "checked"
 182                     } else {
 183                         ""
 184                     };
 185                     format!(
 186                         "<tr>
 187                         <td><input type=\"checkbox\" autocomplete=\"off\" {checked} disabled></td>
 188                         <td>{c}</td>
 189                         </tr>"
 190                     )
 191                 })
 192             }))
 193             .chain(std::iter::once(Ok(HTML_FOOTER.to_owned())))
 194             .collect::<std::io::Result<String>>()
 195             .map_err(|_| cgi::text_response(503, "Missing candidates"))?,
 196     );
 197     if voter.is_err() {
 198         response = set_cookie(response, request.uri().path())?
 199     }
 200     Ok(response)
 201 }
 202
 203 fn write_vote(dir: PathBuf, voter: &[u8], vote: &[u8]) -> std::io::Result<()> {
 204     let datum = [voter, b" ", vote, b"\n"].concat();
 205     let vpath = dir.join("votes");
 206     let vfile = std::fs::File::options()
 207         .append(true)
 208         .create(true)
 209         .open(vpath)?;
 210     let mut vlock = fd_lock::RwLock::new(vfile);
 211     vlock.write()?.write(&datum)?;
 212     Ok(())
 213 }
 214
 215 fn record_vote(dir: PathBuf, request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
 216     let body = request.body();
 217     // Valid votes look like "0 foo" or "1 bar"
 218     if body.len() < 3
 219         || (body[0] != b'0' && body[0] != b'1')
 220         || body[1] != b' '
 221         || body.contains(&b'\n')
 222     {
 223         return Err(cgi::text_response(415, "Invalid vote"));
 224     }
 225     write_vote(dir, &get_voter(&request)?, body)
 226         .map_err(|_| cgi::text_response(503, "Couldn't record vote"))?;
 227     Ok(cgi::text_response(200, "Vote recorded"))
 228 }
 229
 230 fn strip_body(mut response: cgi::Response) -> cgi::Response {
 231     response.body_mut().clear();
 232     response
 233 }
 234
 235 fn respond(request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
 236     let dir = validate_path(request.uri().path())?;
 237     match request.method() {
 238         &cgi::http::Method::HEAD => prompt_for_vote(dir, request).map(strip_body),
 239         &cgi::http::Method::GET => prompt_for_vote(dir, request),
 240         &cgi::http::Method::PUT => record_vote(dir, request),
 241         _ => Err(cgi::text_response(405, "Huh?")),
 242     }
 243 }
 244
 245 fn respond_or_report_error(request: cgi::Request) -> cgi::Response {
 246     match respond(request) {
 247         Ok(result) => result,
 248         Err(error) => error,
 249     }
 250 }
 251
 252 cgi::cgi_main! { respond_or_report_error }