librespot/discovery/src/server.rs

use std::borrow::Cow;
use std::collections::BTreeMap;
use std::convert::Infallible;
use std::net::{Ipv4Addr, SocketAddr};
use std::pin::Pin;
use std::sync::Arc;
use std::task::{Context, Poll};

use aes_ctr::cipher::generic_array::GenericArray;
use aes_ctr::cipher::{NewStreamCipher, SyncStreamCipher};
use aes_ctr::Aes128Ctr;
use futures_core::Stream;
use hmac::{Hmac, Mac, NewMac};
use hyper::service::{make_service_fn, service_fn};
use hyper::{Body, Method, Request, Response, StatusCode};
use log::{debug, warn};
use serde_json::json;
use sha1::{Digest, Sha1};
use tokio::sync::{mpsc, oneshot};

use crate::core::authentication::Credentials;
use crate::core::config::DeviceType;
use crate::core::diffie_hellman::DhLocalKeys;

type Params<'a> = BTreeMap<Cow<'a, str>, Cow<'a, str>>;

pub struct Config {
    pub name: Cow<'static, str>,
    pub device_type: DeviceType,
    pub device_id: String,
}

struct RequestHandler {
    config: Config,
    keys: DhLocalKeys,
    tx: mpsc::UnboundedSender<Credentials>,
}

impl RequestHandler {
    fn new(config: Config) -> (Self, mpsc::UnboundedReceiver<Credentials>) {
        let (tx, rx) = mpsc::unbounded_channel();

        let discovery = Self {
            config,
            keys: DhLocalKeys::random(&mut rand::thread_rng()),
            tx,
        };

        (discovery, rx)
    }

    fn handle_get_info(&self) -> Response<hyper::Body> {
        let public_key = base64::encode(&self.keys.public_key());
        let device_type: &str = self.config.device_type.into();

        let body = json!({
            "status": 101,
            "statusString": "ERROR-OK",
            "spotifyError": 0,
            "version": "2.7.1",
            "deviceID": (self.config.device_id),
            "remoteName": (self.config.name),
            "activeUser": "",
            "publicKey": (public_key),
            "deviceType": (device_type),
            "libraryVersion": crate::core::version::SEMVER,
            "accountReq": "PREMIUM",
            "brandDisplayName": "librespot",
            "modelDisplayName": "librespot",
            "resolverVersion": "0",
            "groupStatus": "NONE",
            "voiceSupport": "NO",
        })
        .to_string();

        Response::new(Body::from(body))
    }

    fn handle_add_user(&self, params: &Params<'_>) -> Response<hyper::Body> {
        let username = params.get("userName").unwrap().as_ref();
        let encrypted_blob = params.get("blob").unwrap();
        let client_key = params.get("clientKey").unwrap();

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

        let client_key = base64::decode(client_key.as_bytes()).unwrap();
        let shared_key = self.keys.shared_secret(&client_key);

        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);
        let base_key = &base_key[..16];

        let checksum_key = {
            let mut h =
                Hmac::<Sha1>::new_from_slice(base_key).expect("HMAC can take key of any size");
            h.update(b"checksum");
            h.finalize().into_bytes()
        };

        let encryption_key = {
            let mut h =
                Hmac::<Sha1>::new_from_slice(base_key).expect("HMAC can take key of any size");
            h.update(b"encryption");
            h.finalize().into_bytes()
        };

        let mut h =
            Hmac::<Sha1>::new_from_slice(&checksum_key).expect("HMAC can take key of any size");
        h.update(encrypted);
        if h.verify(cksum).is_err() {
            warn!("Login error for user {:?}: MAC mismatch", username);
            let result = json!({
                "status": 102,
                "spotifyError": 1,
                "statusString": "ERROR-MAC"
            });

            let body = result.to_string();
            return Response::new(Body::from(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_string(), &decrypted, &self.config.device_id);

        self.tx.send(credentials).unwrap();

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

        let body = result.to_string();
        Response::new(Body::from(body))
    }

    fn not_found(&self) -> Response<hyper::Body> {
        let mut res = Response::default();
        *res.status_mut() = StatusCode::NOT_FOUND;
        res
    }

    async fn handle(self: Arc<Self>, request: Request<Body>) -> hyper::Result<Response<Body>> {
        let mut params = Params::new();

        let (parts, body) = request.into_parts();

        if let Some(query) = parts.uri.query() {
            let query_params = form_urlencoded::parse(query.as_bytes());
            params.extend(query_params);
        }

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

        let body = hyper::body::to_bytes(body).await?;

        params.extend(form_urlencoded::parse(&body));

        let action = params.get("action").map(Cow::as_ref);

        Ok(match (parts.method, action) {
            (Method::GET, Some("getInfo")) => self.handle_get_info(),
            (Method::POST, Some("addUser")) => self.handle_add_user(&params),
            _ => self.not_found(),
        })
    }
}

pub struct DiscoveryServer {
    cred_rx: mpsc::UnboundedReceiver<Credentials>,
    _close_tx: oneshot::Sender<Infallible>,
}

impl DiscoveryServer {
    pub fn new(config: Config, port: &mut u16) -> hyper::Result<Self> {
        let (discovery, cred_rx) = RequestHandler::new(config);
        let discovery = Arc::new(discovery);

        let (close_tx, close_rx) = oneshot::channel();

        let address = SocketAddr::new(Ipv4Addr::UNSPECIFIED.into(), *port);

        let make_service = make_service_fn(move |_| {
            let discovery = discovery.clone();
            async move {
                Ok::<_, hyper::Error>(service_fn(move |request| discovery.clone().handle(request)))
            }
        });

        let server = hyper::Server::try_bind(&address)?.serve(make_service);

        *port = server.local_addr().port();
        debug!("Zeroconf server listening on 0.0.0.0:{}", *port);

        tokio::spawn(async {
            let result = server
                .with_graceful_shutdown(async {
                    close_rx.await.unwrap_err();
                    debug!("Shutting down discovery server");
                })
                .await;

            if let Err(e) = result {
                warn!("Discovery server failed: {}", e);
            }
        });

        Ok(Self {
            cred_rx,
            _close_tx: close_tx,
        })
    }
}

impl Stream for DiscoveryServer {
    type Item = Credentials;

    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Credentials>> {
        self.cred_rx.poll_recv(cx)
    }
}