[voter] / src / main.rs

use rand::prelude::*;
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(|c| c.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 make_random_id() -> [u8; COOKIE_LENGTH] {
    let mut id = [0; COOKIE_LENGTH];
    for i in 0..COOKIE_LENGTH {
        while !(b'A'..=b'Z').contains(&id[i])
            && !(b'a'..=b'z').contains(&id[i])
            && !(b'0'..=b'9').contains(&id[i])
        {
            id[i] = 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)
}

fn prompt_for_vote(dir: PathBuf, request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
    let voter = get_voter(&request);
    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><body><table>".to_owned()))
            .chain(
                std::io::BufReader::new(cfile)
                    .lines()
                    .map(|rc| rc.map(|c| format!("<tr><td>{c}</td></tr>"))),
            )
            .chain(std::iter::once(Ok("</table></body></html>".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: PathBuf, 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(&datum)?;
    Ok(())
}

fn record_vote(dir: PathBuf, 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
dd0a1246	1	use rand::prelude::*;
fbcdf3ed	2	use std::io::prelude::*;
c8402f1c	3	use std::path::{Path, PathBuf};
d1df2e73	4
c8402f1c	5	const DATA_PATH: &str = "/var/lib/voter";
fbcdf3ed	6	const COOKIE_NAME: &[u8] = b"__Secure-id";
ae9be1b6	7	const COOKIE_LENGTH: usize = 12;
c8402f1c SW	8
	9	fn 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
fbcdf3ed SW	31	fn 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
dd0a1246	47	fn make_random_id() -> [u8; COOKIE_LENGTH] {
5a0934fa SW	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
dd0a1246 SW	58	}
	59
	60	fn 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
c8402f1c	78	fn prompt_for_vote(dir: PathBuf, request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
dd0a1246	79	let voter = get_voter(&request);
381eeda5 SW	80	let cfile = std::fs::File::open(dir.join("candidates"))
	81	.map_err(\|_\| cgi::text_response(503, "No candidates"))?;
	82	let mut response = cgi::html_response(
	83	200,
	84	std::iter::once(Ok("<html><body><table>".to_owned()))
	85	.chain(
	86	std::io::BufReader::new(cfile)
	87	.lines()
	88	.map(\|rc\| rc.map(\|c\| format!("<tr><td>{c}</td></tr>"))),
	89	)
	90	.chain(std::iter::once(Ok("</table></body></html>".to_owned())))
	91	.collect::<std::io::Result<String>>()
	92	.map_err(\|_\| cgi::text_response(503, "Missing candidates"))?,
	93	);
dd0a1246 SW	94	if voter.is_err() {
	95	response = set_cookie(response, request.uri().path())?
	96	}
	97	Ok(response)
c8402f1c SW	98	}
c8402f1c SW	99
fbcdf3ed SW	100	fn write_vote(dir: PathBuf, voter: &[u8], vote: &[u8]) -> std::io::Result<()> {
	101	let datum = [voter, b" ", vote, b"\n"].concat();
	102	let vpath = dir.join("votes");
	103	let vfile = std::fs::File::options()
	104	.append(true)
	105	.create(true)
	106	.open(vpath)?;
	107	let mut vlock = fd_lock::RwLock::new(vfile);
	108	vlock.write()?.write(&datum)?;
	109	Ok(())
	110	}
	111
c8402f1c	112	fn record_vote(dir: PathBuf, request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
fbcdf3ed SW	113	let body = request.body();
	114	// Valid votes look like "0 foo" or "1 bar"
	115	if body.len() < 3
	116	\|\| (body[0] != b'0' && body[0] != b'1')
	117	\|\| body[1] != b' '
	118	\|\| body.contains(&b'\n')
	119	{
	120	return Err(cgi::text_response(415, "Invalid vote"));
	121	}
	122	write_vote(dir, &get_voter(&request)?, body)
	123	.map_err(\|_\| cgi::text_response(503, "Couldn't record vote"))?;
	124	Ok(cgi::text_response(200, "Vote recorded"))
	125	}
	126
	127	fn strip_body(mut response: cgi::Response) -> cgi::Response {
	128	response.body_mut().clear();
	129	response
c8402f1c SW	130	}
	131
	132	fn respond(request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
	133	let dir = validate_path(request.uri().path())?;
	134	match request.method() {
fbcdf3ed	135	&cgi::http::Method::HEAD => prompt_for_vote(dir, request).map(strip_body),
c8402f1c	136	&cgi::http::Method::GET => prompt_for_vote(dir, request),
fbcdf3ed	137	&cgi::http::Method::PUT => record_vote(dir, request),
c8402f1c SW	138	_ => Err(cgi::text_response(405, "Huh?")),
	139	}
	140	}
	141
	142	fn respond_or_report_error(request: cgi::Request) -> cgi::Response {
	143	match respond(request) {
	144	Ok(result) => result,
	145	Err(error) => error,
	146	}
d1df2e73 SW	147	}
d1df2e73 SW	148
c8402f1c	149	cgi::cgi_main! { respond_or_report_error }