lemmy/crates/routes/src/images.rs

use actix_web::{
  body::BodyStream,
  error,
  http::{
    header::{HeaderName, ACCEPT_ENCODING, HOST},
    StatusCode,
  },
  web,
  Error,
  HttpRequest,
  HttpResponse,
};
use anyhow::anyhow;
use futures::stream::{Stream, StreamExt};
use lemmy_utils::{claims::Claims, error::LemmyError, rate_limit::RateLimit};
use lemmy_websocket::LemmyContext;
use reqwest::Body;
use reqwest_middleware::{ClientWithMiddleware, RequestBuilder};
use serde::{Deserialize, Serialize};

pub fn config(cfg: &mut web::ServiceConfig, client: ClientWithMiddleware, rate_limit: &RateLimit) {
  cfg
    .app_data(web::Data::new(client))
    .service(
      web::resource("/pictrs/image")
        .wrap(rate_limit.image())
        .route(web::post().to(upload)),
    )
    // This has optional query params: /image/{filename}?format=jpg&thumbnail=256
    .service(web::resource("/pictrs/image/{filename}").route(web::get().to(full_res)))
    .service(web::resource("/pictrs/image/delete/{token}/{filename}").route(web::get().to(delete)));
}

#[derive(Debug, Serialize, Deserialize)]
struct Image {
  file: String,
  delete_token: String,
}

#[derive(Debug, Serialize, Deserialize)]
struct Images {
  msg: String,
  files: Option<Vec<Image>>,
}

#[derive(Deserialize)]
struct PictrsParams {
  format: Option<String>,
  thumbnail: Option<String>,
}

fn adapt_request(
  request: &HttpRequest,
  client: &ClientWithMiddleware,
  url: String,
) -> RequestBuilder {
  // remove accept-encoding header so that pictrs doesnt compress the response
  const INVALID_HEADERS: &[HeaderName] = &[ACCEPT_ENCODING, HOST];

  let client_request = client.request(request.method().clone(), url);

  request
    .headers()
    .iter()
    .fold(client_request, |client_req, (key, value)| {
      if INVALID_HEADERS.contains(key) {
        client_req
      } else {
        client_req.header(key, value)
      }
    })
}

async fn upload(
  req: HttpRequest,
  body: web::Payload,
  client: web::Data<ClientWithMiddleware>,
  context: web::Data<LemmyContext>,
) -> Result<HttpResponse, Error> {
  // TODO: check rate limit here
  let jwt = req
    .cookie("jwt")
    .expect("No auth header for picture upload");

  if Claims::decode(jwt.value(), &context.secret().jwt_secret).is_err() {
    return Ok(HttpResponse::Unauthorized().finish());
  };

  let image_url = format!("{}/image", pictrs_url(context.settings().pictrs_url)?);

  let mut client_req = adapt_request(&req, &client, image_url);

  if let Some(addr) = req.head().peer_addr {
    client_req = client_req.header("X-Forwarded-For", addr.to_string())
  };

  let res = client_req
    .body(Body::wrap_stream(make_send(body)))
    .send()
    .await
    .map_err(error::ErrorBadRequest)?;

  let status = res.status();
  let images = res.json::<Images>().await.map_err(error::ErrorBadRequest)?;

  Ok(HttpResponse::build(status).json(images))
}

async fn full_res(
  filename: web::Path<String>,
  web::Query(params): web::Query<PictrsParams>,
  req: HttpRequest,
  client: web::Data<ClientWithMiddleware>,
  context: web::Data<LemmyContext>,
) -> Result<HttpResponse, Error> {
  let name = &filename.into_inner();

  // If there are no query params, the URL is original
  let pictrs_url_settings = context.settings().pictrs_url;
  let url = if params.format.is_none() && params.thumbnail.is_none() {
    format!(
      "{}/image/original/{}",
      pictrs_url(pictrs_url_settings)?,
      name,
    )
  } else {
    // Use jpg as a default when none is given
    let format = params.format.unwrap_or_else(|| "jpg".to_string());

    let mut url = format!(
      "{}/image/process.{}?src={}",
      pictrs_url(pictrs_url_settings)?,
      format,
      name,
    );

    if let Some(size) = params.thumbnail {
      url = format!("{}&thumbnail={}", url, size,);
    }
    url
  };

  image(url, req, client).await
}

async fn image(
  url: String,
  req: HttpRequest,
  client: web::Data<ClientWithMiddleware>,
) -> Result<HttpResponse, Error> {
  let mut client_req = adapt_request(&req, &client, url);

  if let Some(addr) = req.head().peer_addr {
    client_req = client_req.header("X-Forwarded-For", addr.to_string());
  }

  if let Some(addr) = req.head().peer_addr {
    client_req = client_req.header("X-Forwarded-For", addr.to_string());
  }

  let res = client_req.send().await.map_err(error::ErrorBadRequest)?;

  if res.status() == StatusCode::NOT_FOUND {
    return Ok(HttpResponse::NotFound().finish());
  }

  let mut client_res = HttpResponse::build(res.status());

  for (name, value) in res.headers().iter().filter(|(h, _)| *h != "connection") {
    client_res.insert_header((name.clone(), value.clone()));
  }

  Ok(client_res.body(BodyStream::new(res.bytes_stream())))
}

async fn delete(
  components: web::Path<(String, String)>,
  req: HttpRequest,
  client: web::Data<ClientWithMiddleware>,
  context: web::Data<LemmyContext>,
) -> Result<HttpResponse, Error> {
  let (token, file) = components.into_inner();

  let url = format!(
    "{}/image/delete/{}/{}",
    pictrs_url(context.settings().pictrs_url)?,
    &token,
    &file
  );

  let mut client_req = adapt_request(&req, &client, url);

  if let Some(addr) = req.head().peer_addr {
    client_req = client_req.header("X-Forwarded-For", addr.to_string());
  }

  let res = client_req.send().await.map_err(error::ErrorBadRequest)?;

  Ok(HttpResponse::build(res.status()).body(BodyStream::new(res.bytes_stream())))
}

fn pictrs_url(pictrs_url: Option<String>) -> Result<String, LemmyError> {
  pictrs_url.ok_or_else(|| anyhow!("images_disabled").into())
}

fn make_send<S>(mut stream: S) -> impl Stream<Item = S::Item> + Send + Unpin + 'static
where
  S: Stream + Unpin + 'static,
  S::Item: Send,
{
  // NOTE: the 8 here is arbitrary
  let (tx, rx) = tokio::sync::mpsc::channel(8);

  // NOTE: spawning stream into a new task can potentially hit this bug:
  // - https://github.com/actix/actix-web/issues/1679
  //
  // Since 4.0.0-beta.2 this issue is incredibly less frequent. I have not personally reproduced it.
  // That said, it is still technically possible to encounter.
  actix_web::rt::spawn(async move {
    while let Some(res) = stream.next().await {
      if tx.send(res).await.is_err() {
        break;
      }
    }
  });

  SendStream { rx }
}

struct SendStream<T> {
  rx: tokio::sync::mpsc::Receiver<T>,
}

impl<T> Stream for SendStream<T>
where
  T: Send,
{
  type Item = T;

  fn poll_next(
    mut self: std::pin::Pin<&mut Self>,
    cx: &mut std::task::Context<'_>,
  ) -> std::task::Poll<Option<Self::Item>> {
    std::pin::Pin::new(&mut self.rx).poll_recv(cx)
  }
}