[voter] / src / main.rs

// voter: A simple CGI vote recorder, approval-voting-style
//
// This program is free software: you can redistribute it and/or modify it
// under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, version 3.

use rand::prelude::*;
use std::collections::{HashMap, HashSet};
use std::io::prelude::*;
use std::path::{Path, PathBuf};

const DATA_PATH: &str = "/var/lib/voter";
const COOKIE_NAME: &[u8] = b"__Secure-id";
const COOKIE_LENGTH: usize = 12;

fn validate_path(path: &str) -> Result<PathBuf, cgi::Response> {
    let invalid_path = || cgi::text_response(404, "Invalid path");
    if path == "/" {
        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.)"));
    }
    if path.contains("..") || !path.starts_with('/') {
        return Err(invalid_path());
    }
    let dir = Path::new(&format!("{DATA_PATH}{path}")).to_path_buf();
    if !dir
        .canonicalize()
        .map_err(|_| invalid_path())?
        .starts_with(DATA_PATH)
    {
        return Err(invalid_path());
    }
    if !dir.is_dir() {
        return Err(invalid_path());
    }
    Ok(dir)
}

fn get_voter(request: &cgi::Request) -> Result<&[u8], cgi::Response> {
    // Expect exactly one cookie, exactly as we generate it.
    let cookie = request
        .headers()
        .get(cgi::http::header::COOKIE)
        .map(cgi::http::HeaderValue::as_bytes)
        .and_then(|c| c.strip_prefix(COOKIE_NAME))
        .and_then(|c| c.strip_prefix(b"="))
        .ok_or_else(|| cgi::text_response(400, "Invalid cookie"))?;
    if cookie.len() != COOKIE_LENGTH || cookie.contains(&b' ') || cookie.contains(&b';') {
        Err(cgi::text_response(400, "Invalid cookie"))
    } else {
        Ok(cookie)
    }
}

fn tally_votes(dir: &Path) -> std::io::Result<HashMap<String, HashSet<String>>> {
    let mut tally: HashMap<String, HashSet<String>> = HashMap::new();
    if let Ok(vfile) = std::fs::File::open(dir.to_owned().join("votes")) {
        for liner in std::io::BufReader::new(vfile).lines() {
            let line = liner?;
            if let Some((voter, datum)) = line.split_once(' ') {
                if voter.len() == COOKIE_LENGTH {
                    if let Some((vote, candidate)) = datum.split_once(' ') {
                        if vote == "0" {
                            if let Some(entry) = tally.get_mut(candidate) {
                                entry.remove(voter);
                            }
                        } else if vote == "1" {
                            tally
                                .entry(candidate.to_owned())
                                .or_default()
                                .insert(voter.to_owned());
                        }
                    }
                }
            }
        }
    }
    Ok(tally)
}

fn valid_id_char(c: u8) -> bool {
    (b'A'..=b'Z').contains(&c) || (b'a'..=b'z').contains(&c) || (b'0'..=b'9').contains(&c)
}

fn make_random_id() -> [u8; COOKIE_LENGTH] {
    let mut id = [0; COOKIE_LENGTH];
    for c in &mut id {
        while !valid_id_char(*c) {
            *c = random();
        }
    }
    id
}

fn set_cookie(mut response: cgi::Response, path: &str) -> Result<cgi::Response, cgi::Response> {
    response.headers_mut().append(
        cgi::http::header::SET_COOKIE,
        cgi::http::header::HeaderValue::from_bytes(
            &[
                COOKIE_NAME,
                b"=",
                &make_random_id(),
                b"; Secure; HttpOnly; SameSite=Strict; Max-Age=30000000; Path=",
                path.as_bytes(),
            ]
            .concat(),
        )
        .map_err(|_| cgi::text_response(503, "Couldn't make cookie"))?,
    );
    Ok(response)
}

const HTML_HEADER: &str = "<!DOCTYPE html>
<html>
  <head>
    <meta charset=\"utf-8\">
    <title>Vote!</title>
    <style>
      th { font-size: 70%; text-align: left }
      input { transform: scale(1.5) }
      div { animation: 2s infinite linear spin }
      @keyframes spin {
        from { transform:rotate(0) }
        to { transform:rotate(1turn) }
      }
    </style>
    <script>
      window.onload = function() {
        for (cb of document.getElementsByTagName('input')) {
          cb.addEventListener('click', (function(cb) {
            return function() {
              cb.style.display = 'none'
              const spin = document.createElement('div')
              spin.appendChild(document.createTextNode('⏳'))
              cb.parentElement.insertBefore(spin, cb)

              const req = new XMLHttpRequest()
              req.addEventListener('load', function(e) {
                cb.parentElement.removeChild(cb.previousElementSibling)
                if (req.status == 200) {
                    cb.style.display = ''
                    const delta = cb.checked ? 1 : -1
                    const count_td = cb.parentElement.previousElementSibling
                    count_td.textContent = parseInt(count_td.textContent) + delta
                } else {
                   cb.parentElement.insertBefore(document.createTextNode('❗'), cb)
                }
              })
              req.open('PUT', window.location.href)
              req.send((cb.checked ? 1 : 0) + ' ' + cb.parentElement.nextElementSibling.innerHTML)
            }
          })(cb))
          cb.disabled = false
        }
      }
      function num_cmp(a, b) {
        return parseInt(b.textContent) - parseInt(a.textContent)
      }
      function str_cmp(a, b) {
        if (a.textContent < b.textContent) return -1
        if (a.textContent > b.textContent) return 1
        return 0
      }
      function checked_cmp(a, b) {
        vs = [a, b].map(x => {
          const v = x.children[0].checked + 0
          return isNaN(v) ? -1 : v
        })
        return vs[1] - vs[0]
      }
      function sort_table(col, cmp) {
        const rows = Array.from(document.getElementsByTagName('tr'))
        rows.shift()
        rows.sort((a, b) => cmp(a.children[col], b.children[col]))
        for (row of rows) {
          row.parentElement.appendChild(row)
        }
      }
    </script>
  </head>
  <body>
    <table>
      <tr>
        <th onclick='sort_table(0, num_cmp)'>Count</th>
        <th onclick='sort_table(1, checked_cmp)'>Vote</th>
        <th onclick='sort_table(2, str_cmp)'>Candidate</th>
      </tr>";
const HTML_FOOTER: &str = "
    </table>
  </body>
</html>";

fn supports(tally: &HashMap<String, HashSet<String>>, me: &str, candidate: &str) -> bool {
    tally
        .get(candidate)
        .map_or(false, |supporters| supporters.contains(me))
}

fn prompt_for_vote(dir: &Path, request: &cgi::Request) -> Result<cgi::Response, cgi::Response> {
    let voter = get_voter(request);
    let me = if let Ok(id) = voter {
        std::str::from_utf8(id).ok()
    } else {
        None
    };
    let tally = tally_votes(dir).map_err(|_| cgi::text_response(503, "Couldn't tally votes"))?;
    let cfile = std::fs::File::open(dir.join("candidates"))
        .map_err(|_| cgi::text_response(503, "No candidates"))?;
    let mut response = cgi::html_response(
        200,
        std::iter::once(Ok(HTML_HEADER.to_owned()))
            .chain(std::io::BufReader::new(cfile).lines().map(|rc| {
                rc.map(|c| {
                    let count = tally.get(&c).map_or(0, std::collections::HashSet::len);
                    let checked = if me.map_or(false, |me| supports(&tally, me, &c)) {
                        "checked"
                    } else {
                        ""
                    };
                    format!(
                        "<tr>
                        <td>{count}</td>
                        <td><input type=\"checkbox\" autocomplete=\"off\" {checked} disabled></td>
                        <td>{c}</td>
                        </tr>"
                    )
                })
            }))
            .chain(std::iter::once(Ok(HTML_FOOTER.to_owned())))
            .collect::<std::io::Result<String>>()
            .map_err(|_| cgi::text_response(503, "Missing candidates"))?,
    );
    if voter.is_err() {
        response = set_cookie(response, request.uri().path())?;
    }
    Ok(response)
}

fn write_vote(dir: &Path, voter: &[u8], vote: &[u8]) -> std::io::Result<()> {
    let datum = [voter, b" ", vote, b"\n"].concat();
    let vpath = dir.join("votes");
    let vfile = std::fs::File::options()
        .append(true)
        .create(true)
        .open(vpath)?;
    let mut vlock = fd_lock::RwLock::new(vfile);
    vlock.write()?.write_all(&datum)?;
    Ok(())
}

fn record_vote(dir: &Path, request: &cgi::Request) -> Result<cgi::Response, cgi::Response> {
    let body = request.body();
    // Valid votes look like "0 foo" or "1 bar"
    if body.len() < 3
        || (body[0] != b'0' && body[0] != b'1')
        || body[1] != b' '
        || body.contains(&b'\n')
    {
        return Err(cgi::text_response(415, "Invalid vote"));
    }
    write_vote(dir, get_voter(request)?, body)
        .map_err(|_| cgi::text_response(503, "Couldn't record vote"))?;
    Ok(cgi::text_response(200, "Vote recorded"))
}

fn strip_body(mut response: cgi::Response) -> cgi::Response {
    response.body_mut().clear();
    response
}

fn respond(request: &cgi::Request) -> Result<cgi::Response, cgi::Response> {
    let dir = validate_path(request.uri().path())?;
    match *request.method() {
        cgi::http::Method::HEAD => prompt_for_vote(&dir, request).map(strip_body),
        cgi::http::Method::GET => prompt_for_vote(&dir, request),
        cgi::http::Method::PUT => record_vote(&dir, request),
        _ => Err(cgi::text_response(405, "Huh?")),
    }
}

fn respond_or_report_error(request: cgi::Request) -> cgi::Response {
    match respond(&request) {
        Ok(result) => result,
        Err(error) => error,
    }
}

cgi::cgi_main! { respond_or_report_error }
Commit	Line	Data
302f399b SW	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
dd0a1246	7	use rand::prelude::*;
75cfd491	8	use std::collections::{HashMap, HashSet};
fbcdf3ed	9	use std::io::prelude::*;
c8402f1c	10	use std::path::{Path, PathBuf};
d1df2e73	11
c8402f1c	12	const DATA_PATH: &str = "/var/lib/voter";
fbcdf3ed	13	const COOKIE_NAME: &[u8] = b"__Secure-id";
ae9be1b6	14	const COOKIE_LENGTH: usize = 12;
c8402f1c SW	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	}
81333308	21	if path.contains("..") \|\| !path.starts_with('/') {
c8402f1c SW	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
fbcdf3ed SW	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)
518c108c	43	.map(cgi::http::HeaderValue::as_bytes)
fbcdf3ed SW	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
971d76c7	54	fn tally_votes(dir: &Path) -> std::io::Result<HashMap<String, HashSet<String>>> {
75cfd491	55	let mut tally: HashMap<String, HashSet<String>> = HashMap::new();
971d76c7	56	if let Ok(vfile) = std::fs::File::open(dir.to_owned().join("votes")) {
6f4c1824 SW	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());
75cfd491	71	}
75cfd491 SW	72	}
	73	}
	74	}
	75	}
	76	}
	77	Ok(tally)
	78	}
	79
971d76c7 SW	80	fn valid_id_char(c: u8) -> bool {
971d76c7 SW	81	(b'A'..=b'Z').contains(&c) \|\| (b'a'..=b'z').contains(&c) \|\| (b'0'..=b'9').contains(&c)
81333308 SW	82	}
81333308 SW	83
dd0a1246	84	fn make_random_id() -> [u8; COOKIE_LENGTH] {
5a0934fa	85	let mut id = [0; COOKIE_LENGTH];
518c108c	86	for c in &mut id {
971d76c7 SW	87	while !valid_id_char(*c) {
971d76c7 SW	88	*c = random();
5a0934fa SW	89	}
	90	}
	91	id
dd0a1246 SW	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(),
cf23c41d	102	b"; Secure; HttpOnly; SameSite=Strict; Max-Age=30000000; Path=",
dd0a1246 SW	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
3a28e771	112	const HTML_HEADER: &str = "<!DOCTYPE html>
f5e90a7e SW	113	<html>
f5e90a7e SW	114	<head>
3a28e771	115	<meta charset=\"utf-8\">
9e49b3f0	116	<title>Vote!</title>
f5e90a7e	117	<style>
3a49148b	118	th { font-size: 70%; text-align: left }
9d82c13f	119	input { transform: scale(1.5) }
95432069 SW	120	div { animation: 2s infinite linear spin }
	121	@keyframes spin {
	122	from { transform:rotate(0) }
	123	to { transform:rotate(1turn) }
	124	}
f5e90a7e	125	</style>
9d82c13f SW	126	<script>
	127	window.onload = function() {
	128	for (cb of document.getElementsByTagName('input')) {
95432069 SW	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)
f724d95f SW	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 = ''
6ae24e6d SW	141	const delta = cb.checked ? 1 : -1
	142	const count_td = cb.parentElement.previousElementSibling
	143	count_td.textContent = parseInt(count_td.textContent) + delta
f724d95f SW	144	} else {
	145	cb.parentElement.insertBefore(document.createTextNode('❗'), cb)
	146	}
	147	})
	148	req.open('PUT', window.location.href)
75cfd491	149	req.send((cb.checked ? 1 : 0) + ' ' + cb.parentElement.nextElementSibling.innerHTML)
95432069 SW	150	}
95432069 SW	151	})(cb))
9d82c13f SW	152	cb.disabled = false
	153	}
	154	}
ea1ace7d SW	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	}
9d82c13f	178	</script>
f5e90a7e SW	179	</head>
f5e90a7e SW	180	<body>
3a49148b SW	181	<table>
3a49148b SW	182	<tr>
ea1ace7d SW	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>
3a49148b	186	</tr>";
f5e90a7e SW	187	const HTML_FOOTER: &str = "
	188	</table>
	189	</body>
	190	</html>";
	191
75cfd491 SW	192	fn supports(tally: &HashMap<String, HashSet<String>>, me: &str, candidate: &str) -> bool {
	193	tally
	194	.get(candidate)
518c108c	195	.map_or(false, \|supporters\| supporters.contains(me))
75cfd491 SW	196	}
75cfd491 SW	197
971d76c7 SW	198	fn prompt_for_vote(dir: &Path, request: &cgi::Request) -> Result<cgi::Response, cgi::Response> {
971d76c7 SW	199	let voter = get_voter(request);
75cfd491 SW	200	let me = if let Ok(id) = voter {
	201	std::str::from_utf8(id).ok()
	202	} else {
	203	None
	204	};
971d76c7	205	let tally = tally_votes(dir).map_err(\|_\| cgi::text_response(503, "Couldn't tally votes"))?;
381eeda5 SW	206	let cfile = std::fs::File::open(dir.join("candidates"))
	207	.map_err(\|_\| cgi::text_response(503, "No candidates"))?;
	208	let mut response = cgi::html_response(
	209	200,
f5e90a7e SW	210	std::iter::once(Ok(HTML_HEADER.to_owned()))
f5e90a7e SW	211	.chain(std::io::BufReader::new(cfile).lines().map(\|rc\| {
9d82c13f	212	rc.map(\|c\| {
518c108c SW	213	let count = tally.get(&c).map_or(0, std::collections::HashSet::len);
518c108c SW	214	let checked = if me.map_or(false, \|me\| supports(&tally, me, &c)) {
75cfd491 SW	215	"checked"
	216	} else {
	217	""
	218	};
	219	format!(
	220	"<tr>
05232d49	221	<td>{count}</td>
75cfd491 SW	222	<td><input type=\"checkbox\" autocomplete=\"off\" {checked} disabled></td>
	223	<td>{c}</td>
	224	</tr>"
	225	)
9d82c13f	226	})
f5e90a7e SW	227	}))
f5e90a7e SW	228	.chain(std::iter::once(Ok(HTML_FOOTER.to_owned())))
381eeda5 SW	229	.collect::<std::io::Result<String>>()
	230	.map_err(\|_\| cgi::text_response(503, "Missing candidates"))?,
	231	);
dd0a1246	232	if voter.is_err() {
971d76c7	233	response = set_cookie(response, request.uri().path())?;
dd0a1246 SW	234	}
dd0a1246 SW	235	Ok(response)
c8402f1c SW	236	}
c8402f1c SW	237
971d76c7	238	fn write_vote(dir: &Path, voter: &[u8], vote: &[u8]) -> std::io::Result<()> {
fbcdf3ed SW	239	let datum = [voter, b" ", vote, b"\n"].concat();
	240	let vpath = dir.join("votes");
	241	let vfile = std::fs::File::options()
	242	.append(true)
	243	.create(true)
	244	.open(vpath)?;
	245	let mut vlock = fd_lock::RwLock::new(vfile);
81333308	246	vlock.write()?.write_all(&datum)?;
fbcdf3ed SW	247	Ok(())
	248	}
	249
971d76c7	250	fn record_vote(dir: &Path, request: &cgi::Request) -> Result<cgi::Response, cgi::Response> {
fbcdf3ed SW	251	let body = request.body();
	252	// Valid votes look like "0 foo" or "1 bar"
	253	if body.len() < 3
	254	\|\| (body[0] != b'0' && body[0] != b'1')
	255	\|\| body[1] != b' '
	256	\|\| body.contains(&b'\n')
	257	{
	258	return Err(cgi::text_response(415, "Invalid vote"));
	259	}
971d76c7	260	write_vote(dir, get_voter(request)?, body)
fbcdf3ed SW	261	.map_err(\|_\| cgi::text_response(503, "Couldn't record vote"))?;
	262	Ok(cgi::text_response(200, "Vote recorded"))
	263	}
	264
	265	fn strip_body(mut response: cgi::Response) -> cgi::Response {
	266	response.body_mut().clear();
	267	response
c8402f1c SW	268	}
c8402f1c SW	269
971d76c7	270	fn respond(request: &cgi::Request) -> Result<cgi::Response, cgi::Response> {
c8402f1c	271	let dir = validate_path(request.uri().path())?;
81333308	272	match *request.method() {
971d76c7 SW	273	cgi::http::Method::HEAD => prompt_for_vote(&dir, request).map(strip_body),
	274	cgi::http::Method::GET => prompt_for_vote(&dir, request),
	275	cgi::http::Method::PUT => record_vote(&dir, request),
c8402f1c SW	276	_ => Err(cgi::text_response(405, "Huh?")),
	277	}
	278	}
	279
	280	fn respond_or_report_error(request: cgi::Request) -> cgi::Response {
971d76c7	281	match respond(&request) {
c8402f1c SW	282	Ok(result) => result,
	283	Err(error) => error,
	284	}
d1df2e73 SW	285	}
d1df2e73 SW	286
c8402f1c	287	cgi::cgi_main! { respond_or_report_error }