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1use rand::prelude::*;
2use std::io::prelude::*;
3use std::path::{Path, PathBuf};
4
5const DATA_PATH: &str = "/var/lib/voter";
6const COOKIE_NAME: &[u8] = b"__Secure-id";
7const COOKIE_LENGTH: usize = 12;
8
9fn 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
31fn 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
47fn make_random_id() -> [u8; COOKIE_LENGTH] {
48 let mut id = [0; COOKIE_LENGTH];
49 for i in 0..COOKIE_LENGTH {
50 while !(b'A'..=b'Z').contains(&id[i])
51 && !(b'a'..=b'z').contains(&id[i])
52 && !(b'0'..=b'9').contains(&id[i])
53 {
54 id[i] = random()
55 }
56 }
57 id
58}
59
60fn set_cookie(mut response: cgi::Response, path: &str) -> Result<cgi::Response, cgi::Response> {
61 response.headers_mut().append(
62 cgi::http::header::SET_COOKIE,
63 cgi::http::header::HeaderValue::from_bytes(
64 &[
65 COOKIE_NAME,
66 b"=",
67 &make_random_id(),
68 b"; Secure HttpOnly SameSite=Strict Max-Age=30000000 Path=",
69 path.as_bytes(),
70 ]
71 .concat(),
72 )
73 .map_err(|_| cgi::text_response(503, "Couldn't make cookie"))?,
74 );
75 Ok(response)
76}
77
78const HTML_HEADER: &str = "<!DOCTYPE html>
79<html>
80 <head>
81 <meta charset=\"utf-8\">
82 <title>Vote!</title>
83 <style>
84 input { transform: scale(1.5); }
85 </style>
86 </head>
87 <body>
88 <table>";
89const HTML_FOOTER: &str = "
90 </table>
91 </body>
92</html>";
93
94fn prompt_for_vote(dir: PathBuf, request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
95 let voter = get_voter(&request);
96 let cfile = std::fs::File::open(dir.join("candidates"))
97 .map_err(|_| cgi::text_response(503, "No candidates"))?;
98 let mut response = cgi::html_response(
99 200,
100 std::iter::once(Ok(HTML_HEADER.to_owned()))
101 .chain(std::io::BufReader::new(cfile).lines().map(|rc| {
102 rc.map(|c| format!("<tr><td><input type=\"checkbox\"></td><td>{c}</td></tr>"))
103 }))
104 .chain(std::iter::once(Ok(HTML_FOOTER.to_owned())))
105 .collect::<std::io::Result<String>>()
106 .map_err(|_| cgi::text_response(503, "Missing candidates"))?,
107 );
108 if voter.is_err() {
109 response = set_cookie(response, request.uri().path())?
110 }
111 Ok(response)
112}
113
114fn write_vote(dir: PathBuf, voter: &[u8], vote: &[u8]) -> std::io::Result<()> {
115 let datum = [voter, b" ", vote, b"\n"].concat();
116 let vpath = dir.join("votes");
117 let vfile = std::fs::File::options()
118 .append(true)
119 .create(true)
120 .open(vpath)?;
121 let mut vlock = fd_lock::RwLock::new(vfile);
122 vlock.write()?.write(&datum)?;
123 Ok(())
124}
125
126fn record_vote(dir: PathBuf, request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
127 let body = request.body();
128 // Valid votes look like "0 foo" or "1 bar"
129 if body.len() < 3
130 || (body[0] != b'0' && body[0] != b'1')
131 || body[1] != b' '
132 || body.contains(&b'\n')
133 {
134 return Err(cgi::text_response(415, "Invalid vote"));
135 }
136 write_vote(dir, &get_voter(&request)?, body)
137 .map_err(|_| cgi::text_response(503, "Couldn't record vote"))?;
138 Ok(cgi::text_response(200, "Vote recorded"))
139}
140
141fn strip_body(mut response: cgi::Response) -> cgi::Response {
142 response.body_mut().clear();
143 response
144}
145
146fn respond(request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
147 let dir = validate_path(request.uri().path())?;
148 match request.method() {
149 &cgi::http::Method::HEAD => prompt_for_vote(dir, request).map(strip_body),
150 &cgi::http::Method::GET => prompt_for_vote(dir, request),
151 &cgi::http::Method::PUT => record_vote(dir, request),
152 _ => Err(cgi::text_response(405, "Huh?")),
153 }
154}
155
156fn respond_or_report_error(request: cgi::Request) -> cgi::Response {
157 match respond(request) {
158 Ok(result) => result,
159 Err(error) => error,
160 }
161}
162
163cgi::cgi_main! { respond_or_report_error }