librespot/connect/src/discovery.rs

use base64;
use sha1::{Sha1, Digest};
use hmac::{Hmac, Mac};
use aes_ctr::Aes128Ctr;
use aes_ctr::stream_cipher::{NewStreamCipher, SyncStreamCipher};
use aes_ctr::stream_cipher::generic_array::GenericArray;
use futures::sync::mpsc;
use futures::{Future, Poll, Stream};
use hyper::server::{Http, Request, Response, Service};
use hyper::{self, Get, Post, StatusCode};

#[cfg(feature = "with-dns-sd")]
use dns_sd::DNSService;

#[cfg(not(feature = "with-dns-sd"))]
use mdns;

use num_bigint::BigUint;
use rand;
use std::collections::BTreeMap;
use std::io;
use std::sync::Arc;
use tokio_core::reactor::Handle;
use url;

use librespot_core::authentication::Credentials;
use librespot_core::config::ConnectConfig;
use librespot_core::diffie_hellman::{DH_GENERATOR, DH_PRIME};
use librespot_core::util;

type HmacSha1 = Hmac<Sha1>;

#[derive(Clone)]
struct Discovery(Arc<DiscoveryInner>);
struct DiscoveryInner {
    config: ConnectConfig,
    device_id: String,
    private_key: BigUint,
    public_key: BigUint,
    tx: mpsc::UnboundedSender<Credentials>,
}

impl Discovery {
    fn new(
        config: ConnectConfig,
        device_id: String,
    ) -> (Discovery, mpsc::UnboundedReceiver<Credentials>) {
        let (tx, rx) = mpsc::unbounded();

        let key_data = util::rand_vec(&mut rand::thread_rng(), 95);
        let private_key = BigUint::from_bytes_be(&key_data);
        let public_key = util::powm(&DH_GENERATOR, &private_key, &DH_PRIME);

        let discovery = Discovery(Arc::new(DiscoveryInner {
            config: config,
            device_id: device_id,
            private_key: private_key,
            public_key: public_key,
            tx: tx,
        }));

        (discovery, rx)
    }
}

impl Discovery {
    fn handle_get_info(
        &self,
        _params: &BTreeMap<String, String>,
    ) -> ::futures::Finished<Response, hyper::Error> {
        let public_key = self.0.public_key.to_bytes_be();
        let public_key = base64::encode(&public_key);

        let result = json!({
            "status": 101,
            "statusString": "ERROR-OK",
            "spotifyError": 0,
            "version": "2.1.0",
            "deviceID": (self.0.device_id),
            "remoteName": (self.0.config.name),
            "activeUser": "",
            "publicKey": (public_key),
            "deviceType": (self.0.config.device_type.to_string().to_uppercase()),
            "libraryVersion": "0.1.0",
            "accountReq": "PREMIUM",
            "brandDisplayName": "librespot",
            "modelDisplayName": "librespot",
        });

        let body = result.to_string();
        ::futures::finished(Response::new().with_body(body))
    }

    fn handle_add_user(
        &self,
        params: &BTreeMap<String, String>,
    ) -> ::futures::Finished<Response, hyper::Error> {
        let username = params.get("userName").unwrap();
        let encrypted_blob = params.get("blob").unwrap();
        let client_key = params.get("clientKey").unwrap();

        let encrypted_blob = base64::decode(encrypted_blob).unwrap();

        let client_key = base64::decode(client_key).unwrap();
        let client_key = BigUint::from_bytes_be(&client_key);

        let shared_key = util::powm(&client_key, &self.0.private_key, &DH_PRIME);

        let iv = &encrypted_blob[0..16];
        let encrypted = &encrypted_blob[16..encrypted_blob.len() - 20];
        let cksum = &encrypted_blob[encrypted_blob.len() - 20..encrypted_blob.len()];

        let base_key = Sha1::digest(&shared_key.to_bytes_be());
        let base_key = &base_key[..16];

        let checksum_key = {
            let mut h = HmacSha1::new_varkey(base_key)
                .expect("HMAC can take key of any size");
            h.input(b"checksum");
            h.result().code()
        };

        let encryption_key = {
            let mut h = HmacSha1::new_varkey(&base_key)
                .expect("HMAC can take key of any size");
            h.input(b"encryption");
            h.result().code()
        };

        let mut h = HmacSha1::new_varkey(&checksum_key)
            .expect("HMAC can take key of any size");
        h.input(encrypted);
        if let Err(_) = h.verify(cksum) {
            warn!("Login error for user {:?}: MAC mismatch", username);
            let result = json!({
                "status": 102,
                "spotifyError": 1,
                "statusString": "ERROR-MAC"
            });

            let body = result.to_string();
            return ::futures::finished(Response::new().with_body(body))
        }

        let decrypted = {
            let mut data = encrypted.to_vec();
            let mut cipher = Aes128Ctr::new(
                &GenericArray::from_slice(&encryption_key[0..16]),
                &GenericArray::from_slice(iv),
            );
            cipher.apply_keystream(&mut data);
            String::from_utf8(data).unwrap()
        };

        let credentials = Credentials::with_blob(username.to_owned(), &decrypted, &self.0.device_id);

        self.0.tx.unbounded_send(credentials).unwrap();

        let result = json!({
            "status": 101,
            "spotifyError": 0,
            "statusString": "ERROR-OK"
        });

        let body = result.to_string();
        ::futures::finished(Response::new().with_body(body))
    }

    fn not_found(&self) -> ::futures::Finished<Response, hyper::Error> {
        ::futures::finished(Response::new().with_status(StatusCode::NotFound))
    }
}

impl Service for Discovery {
    type Request = Request;
    type Response = Response;
    type Error = hyper::Error;
    type Future = Box<Future<Item = Response, Error = hyper::Error>>;

    fn call(&self, request: Request) -> Self::Future {
        let mut params = BTreeMap::new();

        let (method, uri, _, _, body) = request.deconstruct();
        if let Some(query) = uri.query() {
            params.extend(url::form_urlencoded::parse(query.as_bytes()).into_owned());
        }

        if method != Get {
            debug!("{:?} {:?} {:?}", method, uri.path(), params);
        }

        let this = self.clone();
        Box::new(
            body.fold(Vec::new(), |mut acc, chunk| {
                acc.extend_from_slice(chunk.as_ref());
                Ok::<_, hyper::Error>(acc)
            }).map(move |body| {
                    params.extend(url::form_urlencoded::parse(&body).into_owned());
                    params
                })
                .and_then(
                    move |params| match (method, params.get("action").map(AsRef::as_ref)) {
                        (Get, Some("getInfo")) => this.handle_get_info(&params),
                        (Post, Some("addUser")) => this.handle_add_user(&params),
                        _ => this.not_found(),
                    },
                ),
        )
    }
}

#[cfg(feature = "with-dns-sd")]
pub struct DiscoveryStream {
    credentials: mpsc::UnboundedReceiver<Credentials>,
    _svc: DNSService,
}

#[cfg(not(feature = "with-dns-sd"))]
pub struct DiscoveryStream {
    credentials: mpsc::UnboundedReceiver<Credentials>,
    _svc: mdns::Service,
}

pub fn discovery(
    handle: &Handle,
    config: ConnectConfig,
    device_id: String,
    port: u16,
) -> io::Result<DiscoveryStream> {
    let (discovery, creds_rx) = Discovery::new(config.clone(), device_id);

    let serve = {
        let http = Http::new();
        http.serve_addr_handle(
            &format!("0.0.0.0:{}", port).parse().unwrap(),
            &handle,
            move || Ok(discovery.clone()),
        ).unwrap()
    };

    let s_port = serve.incoming_ref().local_addr().port();
    debug!("Zeroconf server listening on 0.0.0.0:{}", s_port);

    let server_future = {
        let handle = handle.clone();
        serve
            .for_each(move |connection| {
                handle.spawn(connection.then(|_| Ok(())));
                Ok(())
            })
            .then(|_| Ok(()))
    };
    handle.spawn(server_future);

    #[cfg(feature = "with-dns-sd")]
    let svc = DNSService::register(
        Some(&*config.name),
        "_spotify-connect._tcp",
        None,
        None,
        s_port,
        &["VERSION=1.0", "CPath=/"],
    ).unwrap();

    #[cfg(not(feature = "with-dns-sd"))]
    let responder = mdns::Responder::spawn(&handle)?;

    #[cfg(not(feature = "with-dns-sd"))]
    let svc = responder.register(
        "_spotify-connect._tcp".to_owned(),
        config.name,
        s_port,
        &["VERSION=1.0", "CPath=/"],
    );

    Ok(DiscoveryStream {
        credentials: creds_rx,
        _svc: svc,
    })
}

impl Stream for DiscoveryStream {
    type Item = Credentials;
    type Error = ();

    fn poll(&mut self) -> Poll<Option<Self::Item>, Self::Error> {
        self.credentials.poll()
    }
}