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[voter] / 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 }