[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] {
    std::iter::from_fn(random)
        .filter(|c| {
            (b'A'..=b'Z').contains(c) || (b'a'..=b'z').contains(c) || (b'0'..=b'9').contains(c)
        })
        .take(COOKIE_LENGTH)
        .collect::<Vec<_>>()
        .try_into()
        .unwrap()
}

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 SW	47	fn make_random_id() -> [u8; COOKIE_LENGTH] {
	48	std::iter::from_fn(random)
	49	.filter(\|c\| {
	50	(b'A'..=b'Z').contains(c) \|\| (b'a'..=b'z').contains(c) \|\| (b'0'..=b'9').contains(c)
	51	})
	52	.take(COOKIE_LENGTH)
	53	.collect::<Vec<_>>()
	54	.try_into()
	55	.unwrap()
	56	}
	57
	58	fn set_cookie(mut response: cgi::Response, path: &str) -> Result<cgi::Response, cgi::Response> {
	59	response.headers_mut().append(
	60	cgi::http::header::SET_COOKIE,
	61	cgi::http::header::HeaderValue::from_bytes(
	62	&[
	63	COOKIE_NAME,
	64	b"=",
	65	&make_random_id(),
	66	b"; Secure HttpOnly SameSite=Strict Max-Age=30000000 Path=",
	67	path.as_bytes(),
	68	]
	69	.concat(),
	70	)
	71	.map_err(\|_\| cgi::text_response(503, "Couldn't make cookie"))?,
	72	);
	73	Ok(response)
	74	}
	75
c8402f1c	76	fn prompt_for_vote(dir: PathBuf, request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
dd0a1246	77	let voter = get_voter(&request);
381eeda5 SW	78	let cfile = std::fs::File::open(dir.join("candidates"))
	79	.map_err(\|_\| cgi::text_response(503, "No candidates"))?;
	80	let mut response = cgi::html_response(
	81	200,
	82	std::iter::once(Ok("<html><body><table>".to_owned()))
	83	.chain(
	84	std::io::BufReader::new(cfile)
	85	.lines()
	86	.map(\|rc\| rc.map(\|c\| format!("<tr><td>{c}</td></tr>"))),
	87	)
	88	.chain(std::iter::once(Ok("</table></body></html>".to_owned())))
	89	.collect::<std::io::Result<String>>()
	90	.map_err(\|_\| cgi::text_response(503, "Missing candidates"))?,
	91	);
dd0a1246 SW	92	if voter.is_err() {
	93	response = set_cookie(response, request.uri().path())?
	94	}
	95	Ok(response)
c8402f1c SW	96	}
c8402f1c SW	97
fbcdf3ed SW	98	fn write_vote(dir: PathBuf, voter: &[u8], vote: &[u8]) -> std::io::Result<()> {
	99	let datum = [voter, b" ", vote, b"\n"].concat();
	100	let vpath = dir.join("votes");
	101	let vfile = std::fs::File::options()
	102	.append(true)
	103	.create(true)
	104	.open(vpath)?;
	105	let mut vlock = fd_lock::RwLock::new(vfile);
	106	vlock.write()?.write(&datum)?;
	107	Ok(())
	108	}
	109
c8402f1c	110	fn record_vote(dir: PathBuf, request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
fbcdf3ed SW	111	let body = request.body();
	112	// Valid votes look like "0 foo" or "1 bar"
	113	if body.len() < 3
	114	\|\| (body[0] != b'0' && body[0] != b'1')
	115	\|\| body[1] != b' '
	116	\|\| body.contains(&b'\n')
	117	{
	118	return Err(cgi::text_response(415, "Invalid vote"));
	119	}
	120	write_vote(dir, &get_voter(&request)?, body)
	121	.map_err(\|_\| cgi::text_response(503, "Couldn't record vote"))?;
	122	Ok(cgi::text_response(200, "Vote recorded"))
	123	}
	124
	125	fn strip_body(mut response: cgi::Response) -> cgi::Response {
	126	response.body_mut().clear();
	127	response
c8402f1c SW	128	}
	129
	130	fn respond(request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
	131	let dir = validate_path(request.uri().path())?;
	132	match request.method() {
fbcdf3ed	133	&cgi::http::Method::HEAD => prompt_for_vote(dir, request).map(strip_body),
c8402f1c	134	&cgi::http::Method::GET => prompt_for_vote(dir, request),
fbcdf3ed	135	&cgi::http::Method::PUT => record_vote(dir, request),
c8402f1c SW	136	_ => Err(cgi::text_response(405, "Huh?")),
	137	}
	138	}
	139
	140	fn respond_or_report_error(request: cgi::Request) -> cgi::Response {
	141	match respond(request) {
	142	Ok(result) => result,
	143	Err(error) => error,
	144	}
d1df2e73 SW	145	}
d1df2e73 SW	146
c8402f1c	147	cgi::cgi_main! { respond_or_report_error }