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(|c| c.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 id.iter_mut() {
  87         while !valid_id_char(c)
  88         {
  89             *c = random()
  90         }
  91     }
  92     id
  93 }
  94
  95 fn set_cookie(mut response: cgi::Response, path: &str) -> Result<cgi::Response, cgi::Response> {
  96     response.headers_mut().append(
  97         cgi::http::header::SET_COOKIE,
  98         cgi::http::header::HeaderValue::from_bytes(
  99             &[
 100                 COOKIE_NAME,
 101                 b"=",
 102                 &make_random_id(),
 103                 b"; Secure; HttpOnly; SameSite=Strict; Max-Age=30000000; Path=",
 104                 path.as_bytes(),
 105             ]
 106             .concat(),
 107         )
 108         .map_err(|_| cgi::text_response(503, "Couldn't make cookie"))?,
 109     );
 110     Ok(response)
 111 }
 112
 113 const HTML_HEADER: &str = "<!DOCTYPE html>
 114 <html>
 115   <head>
 116     <meta charset=\"utf-8\">
 117     <title>Vote!</title>
 118     <style>
 119       th { font-size: 70%; text-align: left }
 120       input { transform: scale(1.5) }
 121       div { animation: 2s infinite linear spin }
 122       @keyframes spin {
 123         from { transform:rotate(0) }
 124         to { transform:rotate(1turn) }
 125       }
 126     </style>
 127     <script>
 128       window.onload = function() {
 129         for (cb of document.getElementsByTagName('input')) {
 130           cb.addEventListener('click', (function(cb) {
 131             return function() {
 132               cb.style.display = 'none'
 133               const spin = document.createElement('div')
 134               spin.appendChild(document.createTextNode('⏳'))
 135               cb.parentElement.insertBefore(spin, cb)
 136
 137               const req = new XMLHttpRequest()
 138               req.addEventListener('load', function(e) {
 139                 cb.parentElement.removeChild(cb.previousElementSibling)
 140                 if (req.status == 200) {
 141                     cb.style.display = ''
 142                     const delta = cb.checked ? 1 : -1
 143                     const count_td = cb.parentElement.previousElementSibling
 144                     count_td.textContent = parseInt(count_td.textContent) + delta
 145                 } else {
 146                    cb.parentElement.insertBefore(document.createTextNode('❗'), cb)
 147                 }
 148               })
 149               req.open('PUT', window.location.href)
 150               req.send((cb.checked ? 1 : 0) + ' ' + cb.parentElement.nextElementSibling.innerHTML)
 151             }
 152           })(cb))
 153           cb.disabled = false
 154         }
 155       }
 156       function num_cmp(a, b) {
 157         return parseInt(b.textContent) - parseInt(a.textContent)
 158       }
 159       function str_cmp(a, b) {
 160         if (a.textContent < b.textContent) return -1
 161         if (a.textContent > b.textContent) return 1
 162         return 0
 163       }
 164       function checked_cmp(a, b) {
 165         vs = [a, b].map(x => {
 166           const v = x.children[0].checked + 0
 167           return isNaN(v) ? -1 : v
 168         })
 169         return vs[1] - vs[0]
 170       }
 171       function sort_table(col, cmp) {
 172         const rows = Array.from(document.getElementsByTagName('tr'))
 173         rows.shift()
 174         rows.sort((a, b) => cmp(a.children[col], b.children[col]))
 175         for (row of rows) {
 176           row.parentElement.appendChild(row)
 177         }
 178       }
 179     </script>
 180   </head>
 181   <body>
 182     <table>
 183       <tr>
 184         <th onclick='sort_table(0, num_cmp)'>Count</th>
 185         <th onclick='sort_table(1, checked_cmp)'>Vote</th>
 186         <th onclick='sort_table(2, str_cmp)'>Candidate</th>
 187       </tr>";
 188 const HTML_FOOTER: &str = "
 189     </table>
 190   </body>
 191 </html>";
 192
 193 fn supports(tally: &HashMap<String, HashSet<String>>, me: &str, candidate: &str) -> bool {
 194     tally
 195         .get(candidate)
 196         .map(|supporters| supporters.contains(me))
 197         .unwrap_or(false)
 198 }
 199
 200 fn prompt_for_vote(dir: PathBuf, request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
 201     let voter = get_voter(&request);
 202     let me = if let Ok(id) = voter {
 203         std::str::from_utf8(id).ok()
 204     } else {
 205         None
 206     };
 207     let tally =
 208         tally_votes(dir.clone()).map_err(|_| cgi::text_response(503, "Couldn't tally votes"))?;
 209     let cfile = std::fs::File::open(dir.join("candidates"))
 210         .map_err(|_| cgi::text_response(503, "No candidates"))?;
 211     let mut response = cgi::html_response(
 212         200,
 213         std::iter::once(Ok(HTML_HEADER.to_owned()))
 214             .chain(std::io::BufReader::new(cfile).lines().map(|rc| {
 215                 rc.map(|c| {
 216                     let count = tally
 217                         .get(&c)
 218                         .map(|supporters| supporters.len())
 219                         .unwrap_or(0);
 220                     let checked = if me.map(|me| supports(&tally, me, &c)).unwrap_or(false) {
 221                         "checked"
 222                     } else {
 223                         ""
 224                     };
 225                     format!(
 226                         "<tr>
 227                         <td>{count}</td>
 228                         <td><input type=\"checkbox\" autocomplete=\"off\" {checked} disabled></td>
 229                         <td>{c}</td>
 230                         </tr>"
 231                     )
 232                 })
 233             }))
 234             .chain(std::iter::once(Ok(HTML_FOOTER.to_owned())))
 235             .collect::<std::io::Result<String>>()
 236             .map_err(|_| cgi::text_response(503, "Missing candidates"))?,
 237     );
 238     if voter.is_err() {
 239         response = set_cookie(response, request.uri().path())?
 240     }
 241     Ok(response)
 242 }
 243
 244 fn write_vote(dir: PathBuf, voter: &[u8], vote: &[u8]) -> std::io::Result<()> {
 245     let datum = [voter, b" ", vote, b"\n"].concat();
 246     let vpath = dir.join("votes");
 247     let vfile = std::fs::File::options()
 248         .append(true)
 249         .create(true)
 250         .open(vpath)?;
 251     let mut vlock = fd_lock::RwLock::new(vfile);
 252     vlock.write()?.write_all(&datum)?;
 253     Ok(())
 254 }
 255
 256 fn record_vote(dir: PathBuf, request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
 257     let body = request.body();
 258     // Valid votes look like "0 foo" or "1 bar"
 259     if body.len() < 3
 260         || (body[0] != b'0' && body[0] != b'1')
 261         || body[1] != b' '
 262         || body.contains(&b'\n')
 263     {
 264         return Err(cgi::text_response(415, "Invalid vote"));
 265     }
 266     write_vote(dir, get_voter(&request)?, body)
 267         .map_err(|_| cgi::text_response(503, "Couldn't record vote"))?;
 268     Ok(cgi::text_response(200, "Vote recorded"))
 269 }
 270
 271 fn strip_body(mut response: cgi::Response) -> cgi::Response {
 272     response.body_mut().clear();
 273     response
 274 }
 275
 276 fn respond(request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
 277     let dir = validate_path(request.uri().path())?;
 278     match *request.method() {
 279         cgi::http::Method::HEAD => prompt_for_vote(dir, request).map(strip_body),
 280         cgi::http::Method::GET => prompt_for_vote(dir, request),
 281         cgi::http::Method::PUT => record_vote(dir, request),
 282         _ => Err(cgi::text_response(405, "Huh?")),
 283     }
 284 }
 285
 286 fn respond_or_report_error(request: cgi::Request) -> cgi::Response {
 287     match respond(request) {
 288         Ok(result) => result,
 289         Err(error) => error,
 290     }
 291 }
 292
 293 cgi::cgi_main! { respond_or_report_error }