kochab/src/lib.rs

#[macro_use] extern crate log;

use std::{
    sync::Arc,
    time::Duration,
};
#[cfg(feature = "gemini_srv")]
use std::{
    convert::TryFrom,
    path::PathBuf,
};
#[cfg(feature = "scgi_srv")]
use std::{
    collections::HashMap,
    net::SocketAddr,
    str::FromStr,
};
use tokio::{
    io,
    io::BufReader,
    net::TcpListener,
    net::ToSocketAddrs,
    prelude::*,
};
#[cfg(feature = "scgi_srv")]
use tokio::net::UnixListener;
#[cfg(feature = "gemini_srv")]
use tokio::{
    time::timeout,
    net::TcpStream,
};
#[cfg(feature = "ratelimiting")]
use tokio::time::interval;
#[cfg(feature = "gemini_srv")]
use rustls::ClientCertVerifier;
#[cfg(feature = "gemini_srv")]
use rustls::internal::msgs::handshake::DigitallySignedStruct;
#[cfg(feature = "gemini_srv")]
use tokio_rustls::{rustls, TlsAcceptor};
#[cfg(feature = "gemini_srv")]
use rustls::*;
use anyhow::*;
use crate::util::opt_timeout;
use routing::RoutingNode;
#[cfg(feature = "ratelimiting")]
use ratelimiting::RateLimiter;

pub mod types;
pub mod util;
pub mod routing;
pub mod handling;
#[cfg(feature = "ratelimiting")]
pub mod ratelimiting;
#[cfg(feature = "user_management")]
pub mod user_management;
#[cfg(feature = "certgen")]
pub mod gencert;

#[cfg(feature="user_management")]
use user_management::UserManager;
#[cfg(feature = "certgen")]
use gencert::CertGenMode;

pub use uriparse as uri;
pub use types::*;

pub const REQUEST_URI_MAX_LEN: usize = 1024;
pub const GEMINI_PORT: u16 = 1965;

use handling::Handler;

#[derive(Clone)]
struct ServerInner {
    #[cfg(feature = "gemini_srv")]
    tls_acceptor: TlsAcceptor,
    routes: Arc<RoutingNode<Handler>>,
    timeout: Duration,
    complex_timeout: Option<Duration>,
    #[cfg(feature="ratelimiting")]
    rate_limits: Arc<RoutingNode<RateLimiter<IpAddr>>>,
    #[cfg(feature="user_management")]
    manager: UserManager,
}

impl ServerInner {
    async fn serve_ip(self, listener: TcpListener) -> Result<()> {
        #[cfg(feature = "ratelimiting")]
        tokio::spawn(prune_ratelimit_log(self.rate_limits.clone()));

        loop {
            let (stream, _addr) = listener.accept().await
                .context("Failed to accept client")?;
            let this = self.clone();

            tokio::spawn(async move {
                if let Err(err) = this.serve_client(stream).await {
                    error!("{:?}", err);
                }
            });
        }
    }

    #[cfg(feature = "scgi_srv")]
    // Yeah it's code duplication, but I can't find a way around it, so this is what we're
    // getting for now
    async fn serve_unix(self, listener: UnixListener) -> Result<()> {
        #[cfg(feature = "ratelimiting")]
        tokio::spawn(prune_ratelimit_log(self.rate_limits.clone()));

        loop {
            let (stream, _addr) = listener.accept().await
                .context("Failed to accept client")?;
            let this = self.clone();

            tokio::spawn(async move {
                if let Err(err) = this.serve_client(stream).await {
                    error!("{:?}", err);
                }
            });
        }
    }

    async fn serve_client(
        &self,
        #[cfg(feature = "gemini_srv")]
        stream: TcpStream,
        #[cfg(feature = "scgi_srv")]
        stream: impl AsyncWrite + AsyncRead + Unpin,
    ) -> Result<()> {
        let fut_accept_request = async {
            #[cfg(feature = "gemini_srv")]
            let stream = self.tls_acceptor.accept(stream).await
                .context("Failed to establish TLS session")?;
            let mut stream = BufReader::new(stream);

            let request = self.receive_request(&mut stream).await
                .context("Failed to receive request")?;

            Result::<_, anyhow::Error>::Ok((request, stream))
        };


        // Wait for the request to be parsed
        let (mut request, mut stream) = {
            #[cfg(feature = "gemini_srv")] {
                // Use a timeout for interacting with the client
                let fut_accept_request = timeout(self.timeout, fut_accept_request);
                fut_accept_request.await
                    .context("Client timed out while waiting for response")??
            }
            #[cfg(feature = "scgi_srv")]
            fut_accept_request.await?
        };

        // Determine the remote client's IP address for logging and ratelimiting
        let peer_addr = {
            #[cfg(feature = "gemini_srv")] {
                stream.get_ref()
                    .get_ref()
                    .0
                    .peer_addr()?
                    .ip()
            }
            #[cfg(feature = "scgi_srv")] {
                SocketAddr::from_str(
                    request.headers()
                        .get("REMOTE_ADDR")
                        .ok_or(ParseError::Malformed("REMOTE_ADDR header not received"))?
                        .as_str()
                ).context("Received malformed IP address from upstream")?
                 .ip()
            }
        };

        #[cfg(feature = "ratelimiting")]
        // Perform ratelimiting checks
        if let Some(resp) = self.check_rate_limits(peer_addr, &request) {

            // Log warning
            warn!(
                "Client from {} requesting {} was turned away by ratelimiting",
                peer_addr,
                request.uri()
            );

            // Send error response
            self.send_response(resp, &mut stream).await
                .context("Failed to send response")?;

            // Exit
            return Ok(())
        }

        info!("{} requested: {}", peer_addr, request.uri());

        // Identify the client certificate from the tls stream.  This is the first
        // certificate in the certificate chain.
        #[cfg(feature = "gemini_srv")] { // This is done earlier for `scgi_srv`
            let client_cert = stream.get_ref()
                .get_ref()
                .1
                .get_peer_certificates()
                .and_then(|mut v| if v.is_empty() {None} else {Some(v.remove(0))});

            request.set_cert(client_cert);
        }

        let response = if let Some((trailing, handler)) = self.routes.match_request(&request) {
            request.set_trailing(trailing);
            handler.handle(request).await
        } else {
            Response::not_found()
        };

        self.send_response(response, &mut stream).await
            .context("Failed to send response")?;

        Ok(())
    }

    async fn send_response(&self, mut response: Response, stream: &mut (impl AsyncWrite + Unpin)) -> Result<()> {
        let maybe_body = response.take_body();
        let header = response.header();

        let use_complex_timeout =
            header.status.is_success() &&
            maybe_body.is_some() &&
            header.meta.as_str() != "text/plain" &&
            header.meta.as_str() != "text/gemini" &&
            self.complex_timeout.is_some();

        let send_general_timeout;
        let send_header_timeout;
        let send_body_timeout;

        if use_complex_timeout {
            send_general_timeout = None;
            send_header_timeout = Some(self.timeout);
            send_body_timeout = self.complex_timeout;
        } else {
            send_general_timeout = Some(self.timeout);
            send_header_timeout = None;
            send_body_timeout = None;
        }

        opt_timeout(send_general_timeout, async {
            // Send the header
            opt_timeout(send_header_timeout, send_response_header(response.header(), stream))
                .await
                .context("Timed out while sending response header")?
                .context("Failed to write response header")?;

            // Send the body
            opt_timeout(send_body_timeout, maybe_send_response_body(maybe_body, stream))
                .await
                .context("Timed out while sending response body")?
                .context("Failed to write response body")?;

            Ok::<_,Error>(())
        })
        .await
        .context("Timed out while sending response data")??;

        Ok(())
    }

    #[cfg(feature="ratelimiting")]
    fn check_rate_limits(&self, addr: IpAddr, req: &Request) -> Option<Response> {
        if let Some((_, limiter)) = self.rate_limits.match_request(req) {
            if let Err(when) = limiter.check_key(addr) {
                return Some(Response::new(ResponseHeader {
                    status: Status::SLOW_DOWN,
                    meta: Meta::new(when.as_secs().to_string()).unwrap()
                }))
            }
        }
        None
    }

    #[cfg(feature = "gemini_srv")]
    async fn receive_request(
        &self,
        stream: &mut (impl AsyncBufRead + Unpin),
    ) -> Result<Request> {
        const HEADER_LIMIT: usize = REQUEST_URI_MAX_LEN + "\r\n".len();
        let mut stream = stream.take(HEADER_LIMIT as u64);
        let mut uri = Vec::new();

        stream.read_until(b'\n', &mut uri).await?;

        if !uri.ends_with(b"\r\n") {
            if uri.len() < REQUEST_URI_MAX_LEN {
                bail!("Request header not terminated with CRLF")
            } else {
                bail!("Request URI too long")
            }
        }

        // Strip CRLF
        uri.pop();
        uri.pop();

        let uri = URIReference::try_from(&*uri)
            .context("Request URI is invalid")?
            .into_owned();

        Request::new(
            uri,
            #[cfg(feature="user_management")]
            self.manager.clone(),
        ).context("Failed to create request from URI")
    }

    #[cfg(feature = "scgi_srv")]
    async fn receive_request(
        &self,
        stream: &mut (impl AsyncBufRead + Unpin),
    ) -> Result<Request> {
        let mut buff = Vec::with_capacity(4);

        #[allow(clippy::char_lit_as_u8)]
        // Read the length of the header netstring (e.g. "120:")
        stream.read_until(':' as u8, &mut buff).await?;

        buff.pop(); // Remove the trailing ':'
        let len = std::str::from_utf8(&*buff)
            .ok()
            .and_then(|s| usize::from_str(s).ok())
            .ok_or(ParseError::Malformed("netstring length"))?;

        // Read in the headers
        buff.clear();
        buff.resize(len + 1, 0);
        stream.read_exact(buff.as_mut()).await?;
        buff.truncate(len - 1); // Remove the final \x00,

        // Parse the headers
        let (maybe_trailing, headers) = buff.split(|b| *b == 0) // Headers are null delimiited
            .map(|bytes| // Convert to an &str
                 std::str::from_utf8(bytes)
                    .map_err(|_| ParseError::Malformed("scgi headers"))
                    .map(str::trim)
             )
            .try_fold( // Turn the array of [header, value, header, ...] into a map
                (Option::<&str>::None, HashMap::<String, String>::with_capacity(16)),
                |(last_header, mut headers), s| {
                    s.map(|text| {
                        match last_header {
                            None => (Some(text), headers),
                            Some(header) => {
                                headers.insert(header.to_string(), text.to_string());
                                (None, headers)
                            }
                        }
                    })
                }
            )?;

        // If there's not the same number of headers as values, that's a problem
        if maybe_trailing.is_some() {
            bail!(ParseError::Malformed("trailing header"));
        }

        // Check the content length info
        let cont_len_val = headers.get("CONTENT_LENGTH")
            .ok_or(ParseError::Malformed("No content length header!"))?;
        let cont_len = usize::from_str(cont_len_val)
            .map_err(|_| ParseError::Malformed("Malformed content length"))?;
        if cont_len > 0 {
            bail!(ParseError::Malformed("Gemini SCGI requests should not have a body"));
        }

        // Spec requires setting an SCGI header to one
        if *headers.get("SCGI").ok_or(ParseError::Malformed("No SCGI header"))? != "1" {
            bail!(ParseError::Malformed("SCGI header not set to \"1\""));
        }

        trace!("Headers received: {:?}", headers);

        Ok(Request::new(headers)?)
    }
}

#[derive(Debug)]
#[cfg(feature = "scgi_srv")]
enum ParseError {
    IO(io::Error),
    Malformed(&'static str),
}

#[cfg(feature = "scgi_srv")]
impl From<io::Error> for ParseError {
    fn from(e: io::Error) -> Self {
        Self::IO(e)
    }
}

#[cfg(feature = "scgi_srv")]
impl std::fmt::Display for ParseError {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        match self {
            Self::IO(e) => write!(f, "IO Error while parsing and responding SCGI: {}", e),
            Self::Malformed(e) => write!(f, "SCGI request malformed at {}", e),
        }
    }
}

#[cfg(feature = "scgi_srv")]
impl std::error::Error for ParseError {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        if let Self::IO(e) = self { Some(e) } else { None }
    }
}

pub struct Server {
    timeout: Duration,
    complex_body_timeout_override: Option<Duration>,
    routes: RoutingNode<Handler>,
    #[cfg(feature = "gemini_srv")]
    cert_path: PathBuf,
    #[cfg(feature = "gemini_srv")]
    key_path: PathBuf,
    #[cfg(feature="ratelimiting")]
    rate_limits: RoutingNode<RateLimiter<IpAddr>>,
    #[cfg(feature="user_management")]
    data_dir: PathBuf,
    #[cfg(feature="user_management")]
    database: Option<sled::Db>,
    #[cfg(feature="certgen")]
    certgen_mode: CertGenMode,
}

impl Server {
    pub fn new() -> Self {
        Self {
            timeout: Duration::from_secs(1),
            complex_body_timeout_override: Some(Duration::from_secs(30)),
            routes: RoutingNode::default(),
            #[cfg(feature = "gemini_srv")]
            cert_path: PathBuf::from("cert/cert.pem"),
            #[cfg(feature = "gemini_srv")]
            key_path: PathBuf::from("cert/key.pem"),
            #[cfg(feature="ratelimiting")]
            rate_limits: RoutingNode::default(),
            #[cfg(feature="user_management")]
            data_dir: "data".into(),
            #[cfg(feature="user_management")]
            database: None,
            #[cfg(feature="certgen")]
            certgen_mode: CertGenMode::Interactive,
        }
    }

    #[cfg(feature="user_management")]
    /// Sets the directory to store user data in
    ///
    /// This will only be used if a database is not provided with [`set_database()`].
    ///
    /// Defaults to `./data` if not specified
    ///
    /// [`set_database()`]: Self::set_database()
    pub fn set_database_dir(mut self, path: impl Into<PathBuf>) -> Self {
        self.data_dir = path.into();
        self
    }

    #[cfg(feature="user_management")]
    /// Sets a specific database to use
    ///
    /// This opens to trees within the database, both namespaced to avoid collisions.
    ///
    /// If this is not provided, a database will be opened at the directory provided by
    /// [`set_database_dir()`]
    ///
    /// [`set_database_dir()`]: Self::set_database_dir()
    pub fn set_database(mut self, db: sled::Db) -> Self {
        self.database = Some(db);
        self
    }

    #[cfg(feature="certgen")]
    /// Determine where certificate config comes from, if generation is required
    ///
    /// If a certificate & keyfile are not available on the provided path, they can be
    /// generated.  If this happens, several modes can be used to generate them, including
    /// not generating them and just erroring, interactively prompting the user for
    /// information, and using pre-provided information.
    pub fn set_certificate_generation_mode(mut self, mode: CertGenMode) -> Self {
        self.certgen_mode = mode;
        self
    }

    #[cfg(feature = "gemini_srv")]
    /// Sets the directory that kochab should look for TLS certs and keys into
    ///
    /// Northstar will look for files called `cert.pem` and `key.pem` in the provided
    /// directory.
    ///
    /// This does not need to be set if both [`set_cert()`](Self::set_cert()) and
    /// [`set_key()`](Self::set_key()) have been called.
    ///
    /// If not set, the default is `cert/`
    pub fn set_tls_dir(self, dir: impl Into<PathBuf>) -> Self {
        let dir = dir.into();
        self.set_cert(dir.join("cert.pem"))
            .set_key(dir.join("key.pem"))
    }

    #[cfg(feature = "gemini_srv")]
    /// Set the path to the TLS certificate kochab will use
    ///
    /// This defaults to `cert/cert.pem`.
    ///
    /// This does not need to be called it [`set_tls_dir()`](Self::set_tls_dir()) has been
    /// called.
    pub fn set_cert(mut self, cert_path: impl Into<PathBuf>) -> Self {
        self.cert_path = cert_path.into();
        self
    }

    #[cfg(feature = "gemini_srv")]
    /// Set the path to the ertificate key kochab will use
    ///
    /// This defaults to `cert/key.pem`.
    ///
    /// This does not need to be called it [`set_tls_dir()`](Self::set_tls_dir()) has been
    /// called.
    ///
    /// This should of course correspond to the key set in
    /// [`set_cert()`](Self::set_cert())
    pub fn set_key(mut self, key_path: impl Into<PathBuf>) -> Self {
        self.key_path = key_path.into();
        self
    }

    /// Set the timeout on incoming requests
    ///
    /// Note that this timeout is applied twice, once for the delivery of the request, and
    /// once for sending the client's response.  This means that for a 1 second timeout,
    /// the client will have 1 second to complete the TLS handshake and deliver a request
    /// header, then your API will have as much time as it needs to handle the request,
    /// before the client has another second to receive the response.
    ///
    /// If you would like a timeout for your code itself, please use
    /// [`tokio::time::Timeout`] to implement it internally.
    ///
    /// **The default timeout is 1 second.**  As somewhat of a workaround for
    /// shortcomings of the specification, this timeout, and any timeout set using this
    /// method, is overridden in special cases, specifically for MIME types outside of
    /// `text/plain` and `text/gemini`, to be 30 seconds.  If you would like to change or
    /// prevent this, please see
    /// [`override_complex_body_timeout`](Self::override_complex_body_timeout()).
    pub fn set_timeout(mut self, timeout: Duration) -> Self {
        self.timeout = timeout;
        self
    }

    /// Override the timeout for complex body types
    ///
    /// Many clients choose to handle body types which cannot be displayed by prompting
    /// the user if they would like to download or open the request body.  However, since
    /// this prompt occurs in the middle of receiving a request, often the connection
    /// times out before the end user is able to respond to the prompt.
    ///
    /// As a workaround, it is possible to set an override on the request timeout in
    /// specific conditions:
    ///
    /// 1. **Only override the timeout for receiving the body of the request.**  This will
    ///    not override the timeout on sending the request header, nor on receiving the
    ///    response header.
    /// 2. **Only override the timeout for successful responses.**  The only bodies which
    ///    have bodies are successful ones.  In all other cases, there's no body to
    ///    timeout for
    /// 3. **Only override the timeout for complex body types.**  Almost all clients are
    ///    able to display `text/plain` and `text/gemini` responses, and will not prompt
    ///    the user for these response types.  This means that there is no reason to
    ///    expect a client to have a human-length response time for these MIME types.
    ///    Because of this, responses of this type will not be overridden.
    ///
    /// This method is used to override the timeout for responses meeting these specific
    /// criteria.  All other stages of the connection will use the timeout specified in
    /// [`set_timeout()`](Self::set_timeout()).
    ///
    /// If this is set to [`None`], then the client will have the default amount of time
    /// to both receive the header and the body.  If this is set to [`Some`], the client
    /// will have the default amount of time to recieve the header, and an *additional*
    /// alotment of time to recieve the body.
    ///
    /// The default timeout for this is 30 seconds.
    pub fn override_complex_body_timeout(mut self, timeout: Option<Duration>) -> Self {
        self.complex_body_timeout_override = timeout;
        self
    }

    /// Add a handler for a route
    ///
    /// A route must be an absolute path, for example "/endpoint" or "/", but not
    /// "endpoint".  Entering a relative or malformed path will result in a panic.
    ///
    /// For more information about routing mechanics, see the docs for [`RoutingNode`].
    pub fn add_route(mut self, path: &'static str, handler: impl Into<Handler>) -> Self {
        self.routes.add_route(path, handler.into());
        self
    }

    #[cfg(feature="ratelimiting")]
    /// Add a rate limit to a route
    ///
    /// The server will allow at most `burst` connections to any endpoints under this
    /// route in a period of `period`.  All extra requests will recieve a `SLOW_DOWN`, and
    /// not be sent to the handler.
    ///
    /// A route must be an absolute path, for example "/endpoint" or "/", but not
    /// "endpoint".  Entering a relative or malformed path will result in a panic.
    ///
    /// For more information about routing mechanics, see the docs for [`RoutingNode`].
    pub fn ratelimit(mut self, path: &'static str, burst: usize, period: Duration) -> Self {
        let limiter = RateLimiter::new(period, burst);
        self.rate_limits.add_route(path, limiter);
        self
    }

    fn build(mut self) -> Result<ServerInner> {
        #[cfg(feature = "gemini_srv")]
        let config = tls_config(
            &self.cert_path,
            &self.key_path,
            #[cfg(feature="certgen")]
            self.certgen_mode
        ).context("Failed to create TLS config")?;

        self.routes.shrink();

        #[cfg(feature="user_management")]
        let data_dir = self.data_dir;

        Ok(ServerInner {
            routes: Arc::new(self.routes),
            timeout: self.timeout,
            complex_timeout: self.complex_body_timeout_override,
            #[cfg(feature = "gemini_srv")]
            tls_acceptor: TlsAcceptor::from(config),
            #[cfg(feature="ratelimiting")]
            rate_limits: Arc::new(self.rate_limits),
            #[cfg(feature="user_management")]
            manager: UserManager::new(
                self.database.unwrap_or_else(move|| sled::open(data_dir).unwrap())
            )?,
        })
    }

    /// Start serving requests on a given bound address & port
    ///
    /// `addr` can be anything `tokio` can parse, including just a string like
    /// "localhost:1965"
    pub async fn serve_ip(self, addr: impl ToSocketAddrs) -> Result<()> {
        let server = self.build()?;
        let socket = TcpListener::bind(addr).await?;
        server.serve_ip(socket).await
    }

    #[cfg(feature = "scgi_srv")]
    /// Start serving requests on a given unix socket
    ///
    /// Requires an address in the form of a path to bind to.  This is only available when
    /// in `scgi_srv` mode.
    pub async fn serve_unix(self, addr: impl AsRef<std::path::Path>) -> Result<()> {
        let server = self.build()?;
        let socket = UnixListener::bind(addr)?;
        server.serve_unix(socket).await
    }
}

impl Default for Server {
    fn default() -> Self {
        Self::new()
    }
}

async fn send_response_header(header: &ResponseHeader, stream: &mut (impl AsyncWrite + Unpin)) -> Result<()> {
    let header = format!(
        "{status} {meta}\r\n",
        status = header.status.code(),
        meta = header.meta.as_str(),
    );

    stream.write_all(header.as_bytes()).await?;
    stream.flush().await?;

    Ok(())
}

async fn maybe_send_response_body(maybe_body: Option<Body>, stream: &mut (impl AsyncWrite + Unpin)) -> Result<()> {
    if let Some(body) = maybe_body {
        send_response_body(body, stream).await?;
    }

    Ok(())
}

async fn send_response_body(body: Body, stream: &mut (impl AsyncWrite + Unpin)) -> Result<()> {
    match body {
        Body::Bytes(bytes) => stream.write_all(&bytes).await?,
        Body::Reader(mut reader) => { io::copy(&mut reader, stream).await?; },
    }

    stream.flush().await?;

    Ok(())
}

#[cfg(feature="ratelimiting")]
/// Every 5 minutes, remove excess keys from all ratelimiters
async fn prune_ratelimit_log(rate_limits: Arc<RoutingNode<RateLimiter<IpAddr>>>) -> Never {
    let mut interval = interval(tokio::time::Duration::from_secs(10));
    let log = rate_limits.as_ref();
    loop {
        interval.tick().await;
        log.iter().for_each(RateLimiter::trim_keys_verbose);
    }
}

#[cfg(feature = "gemini_srv")]
fn tls_config(
    cert_path: &PathBuf,
    key_path: &PathBuf,
    #[cfg(feature = "certgen")]
    mode: CertGenMode,
) -> Result<Arc<ServerConfig>> {
    let mut config = ServerConfig::new(AllowAnonOrSelfsignedClient::new());

    #[cfg(feature = "certgen")]
    mode.load_or_generate(&mut config, cert_path, key_path)?;

    #[cfg(not(feature = "certgen"))] {
        let cert_chain = load_cert_chain(cert_path)
            .context("Failed to load TLS certificate")?;
        let key = load_key(key_path)
            .context("Failed to load TLS key")?;
        config.set_single_cert(cert_chain, key)
            .context("Failed to use loaded TLS certificate")?;
    }

    Ok(config.into())
}

#[cfg(feature = "gemini_srv")]
fn load_cert_chain(cert_path: &PathBuf) -> Result<Vec<Certificate>> {
    let certs = std::fs::File::open(cert_path)
        .with_context(|| format!("Failed to open `{:?}`", cert_path))?;
    let mut certs = std::io::BufReader::new(certs);
    let certs = rustls::internal::pemfile::certs(&mut certs)
        .map_err(|_| anyhow!("failed to load certs `{:?}`", cert_path))?;

    Ok(certs)
}

#[cfg(feature = "gemini_srv")]
fn load_key(key_path: &PathBuf) -> Result<PrivateKey> {
    let keys = std::fs::File::open(key_path)
        .with_context(|| format!("Failed to open `{:?}`", key_path))?;
    let mut keys = std::io::BufReader::new(keys);
    let mut keys = rustls::internal::pemfile::pkcs8_private_keys(&mut keys)
        .map_err(|_| anyhow!("failed to load key `{:?}`", key_path))?;

    ensure!(!keys.is_empty(), "no key found");

    let key = keys.swap_remove(0);

    Ok(key)
}

#[cfg(feature = "gemini_srv")]
/// A client cert verifier that accepts all connections
///
/// Unfortunately, rustls doesn't provide a ClientCertVerifier that accepts self-signed
/// certificates, so we need to implement this ourselves.
struct AllowAnonOrSelfsignedClient { }

#[cfg(feature = "gemini_srv")]
impl AllowAnonOrSelfsignedClient {

    /// Create a new verifier
    fn new() -> Arc<Self> {
        Arc::new(Self {})
    }

}

#[cfg(feature = "gemini_srv")]
impl ClientCertVerifier for AllowAnonOrSelfsignedClient {

    fn client_auth_root_subjects(
        &self,
        _: Option<&webpki::DNSName>
    ) -> Option<DistinguishedNames> {
        Some(Vec::new())
    }

    fn client_auth_mandatory(&self, _sni: Option<&webpki::DNSName>) -> Option<bool> {
        Some(false)
    }

    // the below methods are a hack until webpki doesn't break with certain certs

    fn verify_client_cert(
        &self,
        _: &[Certificate],
        _: Option<&webpki::DNSName>
    ) -> Result<ClientCertVerified, TLSError> {
        Ok(ClientCertVerified::assertion())
    }

    fn verify_tls12_signature(
        &self,
        _message: &[u8],
        _cert: &Certificate,
        _dss: &DigitallySignedStruct,
    ) -> Result<HandshakeSignatureValid, TLSError> {
        Ok(HandshakeSignatureValid::assertion())
    }

    fn verify_tls13_signature(
        &self,
        _message: &[u8],
        _cert: &Certificate,
        _dss: &DigitallySignedStruct,
    ) -> Result<HandshakeSignatureValid, TLSError> {
        Ok(HandshakeSignatureValid::assertion())
    }
}

#[cfg(feature = "ratelimiting")]
enum Never {}