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

   1 // voter: A simple CGI vote recorder, approval-voting-style
   2 //
   3 // This program is free software: you can redistribute it and/or modify it
   4 // under the terms of the GNU Affero General Public License as published
   5 // by the Free Software Foundation, version 3.
   6
   7 use rand::prelude::*;
   8 use std::collections::{HashMap, HashSet};
   9 use std::io::prelude::*;
  10 use std::path::{Path, PathBuf};
  11
  12 const DATA_PATH: &str = "/var/lib/voter";
  13 const COOKIE_NAME: &[u8] = b"__Secure-id";
  14 const COOKIE_LENGTH: usize = 12;
  15
  16 fn validate_path(path: &str) -> Result<PathBuf, cgi::Response> {
  17     let invalid_path = || cgi::text_response(404, "Invalid path");
  18     if path == "/" {
  19         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.)"));
  20     }
  21     if path.contains("..") || !path.starts_with('/') {
  22         return Err(invalid_path());
  23     }
  24     let dir = Path::new(&format!("{DATA_PATH}{path}")).to_path_buf();
  25     if !dir
  26         .canonicalize()
  27         .map_err(|_| invalid_path())?
  28         .starts_with(DATA_PATH)
  29     {
  30         return Err(invalid_path());
  31     }
  32     if !dir.is_dir() {
  33         return Err(invalid_path());
  34     }
  35     Ok(dir)
  36 }
  37
  38 fn get_voter(request: &cgi::Request) -> Result<&[u8], cgi::Response> {
  39     // Expect exactly one cookie, exactly as we generate it.
  40     let cookie = request
  41         .headers()
  42         .get(cgi::http::header::COOKIE)
  43         .map(cgi::http::HeaderValue::as_bytes)
  44         .and_then(|c| c.strip_prefix(COOKIE_NAME))
  45         .and_then(|c| c.strip_prefix(b"="))
  46         .ok_or_else(|| cgi::text_response(400, "Invalid cookie"))?;
  47     if cookie.len() != COOKIE_LENGTH || cookie.contains(&b' ') || cookie.contains(&b';') {
  48         Err(cgi::text_response(400, "Invalid cookie"))
  49     } else {
  50         Ok(cookie)
  51     }
  52 }
  53
  54 fn tally_votes(dir: PathBuf) -> std::io::Result<HashMap<String, HashSet<String>>> {
  55     let mut tally: HashMap<String, HashSet<String>> = HashMap::new();
  56     if let Ok(vfile) = std::fs::File::open(dir.join("votes")) {
  57         for liner in std::io::BufReader::new(vfile).lines() {
  58             let line = liner?;
  59             if let Some((voter, datum)) = line.split_once(' ') {
  60                 if voter.len() == COOKIE_LENGTH {
  61                     if let Some((vote, candidate)) = datum.split_once(' ') {
  62                         if vote == "0" {
  63                             if let Some(entry) = tally.get_mut(candidate) {
  64                                 entry.remove(voter);
  65                             }
  66                         } else if vote == "1" {
  67                             tally
  68                                 .entry(candidate.to_owned())
  69                                 .or_default()
  70                                 .insert(voter.to_owned());
  71                         }
  72                     }
  73                 }
  74             }
  75         }
  76     }
  77     Ok(tally)
  78 }
  79
  80 fn valid_id_char(c: &u8) -> bool {
  81     (b'A'..=b'Z').contains(c) || (b'a'..=b'z').contains(c) || (b'0'..=b'9').contains(c)
  82 }
  83
  84 fn make_random_id() -> [u8; COOKIE_LENGTH] {
  85     let mut id = [0; COOKIE_LENGTH];
  86     for c in &mut id {
  87         while !valid_id_char(c) {
  88             *c = random()
  89         }
  90     }
  91     id
  92 }
  93
  94 fn set_cookie(mut response: cgi::Response, path: &str) -> Result<cgi::Response, cgi::Response> {
  95     response.headers_mut().append(
  96         cgi::http::header::SET_COOKIE,
  97         cgi::http::header::HeaderValue::from_bytes(
  98             &[
  99                 COOKIE_NAME,
 100                 b"=",
 101                 &make_random_id(),
 102                 b"; Secure; HttpOnly; SameSite=Strict; Max-Age=30000000; Path=",
 103                 path.as_bytes(),
 104             ]
 105             .concat(),
 106         )
 107         .map_err(|_| cgi::text_response(503, "Couldn't make cookie"))?,
 108     );
 109     Ok(response)
 110 }
 111
 112 const HTML_HEADER: &str = "<!DOCTYPE html>
 113 <html>
 114   <head>
 115     <meta charset=\"utf-8\">
 116     <title>Vote!</title>
 117     <style>
 118       th { font-size: 70%; text-align: left }
 119       input { transform: scale(1.5) }
 120       div { animation: 2s infinite linear spin }
 121       @keyframes spin {
 122         from { transform:rotate(0) }
 123         to { transform:rotate(1turn) }
 124       }
 125     </style>
 126     <script>
 127       window.onload = function() {
 128         for (cb of document.getElementsByTagName('input')) {
 129           cb.addEventListener('click', (function(cb) {
 130             return function() {
 131               cb.style.display = 'none'
 132               const spin = document.createElement('div')
 133               spin.appendChild(document.createTextNode('⏳'))
 134               cb.parentElement.insertBefore(spin, cb)
 135
 136               const req = new XMLHttpRequest()
 137               req.addEventListener('load', function(e) {
 138                 cb.parentElement.removeChild(cb.previousElementSibling)
 139                 if (req.status == 200) {
 140                     cb.style.display = ''
 141                     const delta = cb.checked ? 1 : -1
 142                     const count_td = cb.parentElement.previousElementSibling
 143                     count_td.textContent = parseInt(count_td.textContent) + delta
 144                 } else {
 145                    cb.parentElement.insertBefore(document.createTextNode('❗'), cb)
 146                 }
 147               })
 148               req.open('PUT', window.location.href)
 149               req.send((cb.checked ? 1 : 0) + ' ' + cb.parentElement.nextElementSibling.innerHTML)
 150             }
 151           })(cb))
 152           cb.disabled = false
 153         }
 154       }
 155       function num_cmp(a, b) {
 156         return parseInt(b.textContent) - parseInt(a.textContent)
 157       }
 158       function str_cmp(a, b) {
 159         if (a.textContent < b.textContent) return -1
 160         if (a.textContent > b.textContent) return 1
 161         return 0
 162       }
 163       function checked_cmp(a, b) {
 164         vs = [a, b].map(x => {
 165           const v = x.children[0].checked + 0
 166           return isNaN(v) ? -1 : v
 167         })
 168         return vs[1] - vs[0]
 169       }
 170       function sort_table(col, cmp) {
 171         const rows = Array.from(document.getElementsByTagName('tr'))
 172         rows.shift()
 173         rows.sort((a, b) => cmp(a.children[col], b.children[col]))
 174         for (row of rows) {
 175           row.parentElement.appendChild(row)
 176         }
 177       }
 178     </script>
 179   </head>
 180   <body>
 181     <table>
 182       <tr>
 183         <th onclick='sort_table(0, num_cmp)'>Count</th>
 184         <th onclick='sort_table(1, checked_cmp)'>Vote</th>
 185         <th onclick='sort_table(2, str_cmp)'>Candidate</th>
 186       </tr>";
 187 const HTML_FOOTER: &str = "
 188     </table>
 189   </body>
 190 </html>";
 191
 192 fn supports(tally: &HashMap<String, HashSet<String>>, me: &str, candidate: &str) -> bool {
 193     tally
 194         .get(candidate)
 195         .map_or(false, |supporters| supporters.contains(me))
 196 }
 197
 198 fn prompt_for_vote(dir: PathBuf, request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
 199     let voter = get_voter(&request);
 200     let me = if let Ok(id) = voter {
 201         std::str::from_utf8(id).ok()
 202     } else {
 203         None
 204     };
 205     let tally =
 206         tally_votes(dir.clone()).map_err(|_| cgi::text_response(503, "Couldn't tally votes"))?;
 207     let cfile = std::fs::File::open(dir.join("candidates"))
 208         .map_err(|_| cgi::text_response(503, "No candidates"))?;
 209     let mut response = cgi::html_response(
 210         200,
 211         std::iter::once(Ok(HTML_HEADER.to_owned()))
 212             .chain(std::io::BufReader::new(cfile).lines().map(|rc| {
 213                 rc.map(|c| {
 214                     let count = tally.get(&c).map_or(0, std::collections::HashSet::len);
 215                     let checked = if me.map_or(false, |me| supports(&tally, me, &c)) {
 216                         "checked"
 217                     } else {
 218                         ""
 219                     };
 220                     format!(
 221                         "<tr>
 222                         <td>{count}</td>
 223                         <td><input type=\"checkbox\" autocomplete=\"off\" {checked} disabled></td>
 224                         <td>{c}</td>
 225                         </tr>"
 226                     )
 227                 })
 228             }))
 229             .chain(std::iter::once(Ok(HTML_FOOTER.to_owned())))
 230             .collect::<std::io::Result<String>>()
 231             .map_err(|_| cgi::text_response(503, "Missing candidates"))?,
 232     );
 233     if voter.is_err() {
 234         response = set_cookie(response, request.uri().path())?
 235     }
 236     Ok(response)
 237 }
 238
 239 fn write_vote(dir: PathBuf, voter: &[u8], vote: &[u8]) -> std::io::Result<()> {
 240     let datum = [voter, b" ", vote, b"\n"].concat();
 241     let vpath = dir.join("votes");
 242     let vfile = std::fs::File::options()
 243         .append(true)
 244         .create(true)
 245         .open(vpath)?;
 246     let mut vlock = fd_lock::RwLock::new(vfile);
 247     vlock.write()?.write_all(&datum)?;
 248     Ok(())
 249 }
 250
 251 fn record_vote(dir: PathBuf, request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
 252     let body = request.body();
 253     // Valid votes look like "0 foo" or "1 bar"
 254     if body.len() < 3
 255         || (body[0] != b'0' && body[0] != b'1')
 256         || body[1] != b' '
 257         || body.contains(&b'\n')
 258     {
 259         return Err(cgi::text_response(415, "Invalid vote"));
 260     }
 261     write_vote(dir, get_voter(&request)?, body)
 262         .map_err(|_| cgi::text_response(503, "Couldn't record vote"))?;
 263     Ok(cgi::text_response(200, "Vote recorded"))
 264 }
 265
 266 fn strip_body(mut response: cgi::Response) -> cgi::Response {
 267     response.body_mut().clear();
 268     response
 269 }
 270
 271 fn respond(request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
 272     let dir = validate_path(request.uri().path())?;
 273     match *request.method() {
 274         cgi::http::Method::HEAD => prompt_for_vote(dir, request).map(strip_body),
 275         cgi::http::Method::GET => prompt_for_vote(dir, request),
 276         cgi::http::Method::PUT => record_vote(dir, request),
 277         _ => Err(cgi::text_response(405, "Huh?")),
 278     }
 279 }
 280
 281 fn respond_or_report_error(request: cgi::Request) -> cgi::Response {
 282     match respond(request) {
 283         Ok(result) => result,
 284         Err(error) => error,
 285     }
 286 }
 287
 288 cgi::cgi_main! { respond_or_report_error }