lemmy/crates/apub/src/lib.rs

use crate::fetcher::post_or_comment::PostOrComment;
use activitypub_federation::config::{Data, UrlVerifier};
use async_trait::async_trait;
use futures::future::join3;
use lemmy_api_common::context::LemmyContext;
use lemmy_db_schema::{
  source::{
    activity::{Activity, ActivityInsertForm},
    instance::Instance,
    local_site::LocalSite,
  },
  traits::Crud,
  utils::DbPool,
};
use lemmy_utils::error::{LemmyError, LemmyResult};
use moka::future::Cache;
use once_cell::sync::Lazy;
use serde::Serialize;
use std::{sync::Arc, time::Duration};
use url::Url;

pub mod activities;
pub(crate) mod activity_lists;
pub mod api;
pub(crate) mod collections;
pub mod fetcher;
pub mod http;
pub(crate) mod mentions;
pub mod objects;
pub mod protocol;

pub const FEDERATION_HTTP_FETCH_LIMIT: u32 = 50;
/// All incoming and outgoing federation actions read the blocklist/allowlist and slur filters
/// multiple times. This causes a huge number of database reads if we hit the db directly. So we
/// cache these values for a short time, which will already make a huge difference and ensures that
/// changes take effect quickly.
const BLOCKLIST_CACHE_DURATION: Duration = Duration::from_secs(60);

static CONTEXT: Lazy<Vec<serde_json::Value>> = Lazy::new(|| {
  serde_json::from_str(include_str!("../assets/lemmy/context.json")).expect("parse context")
});

#[derive(Clone)]
pub struct VerifyUrlData(pub DbPool);

#[async_trait]
impl UrlVerifier for VerifyUrlData {
  async fn verify(&self, url: &Url) -> Result<(), &'static str> {
    let local_site_data = local_site_data_cached(&self.0)
      .await
      .expect("read local site data");
    check_apub_id_valid(url, &local_site_data)?;
    Ok(())
  }
}

/// Checks if the ID is allowed for sending or receiving.
///
/// In particular, it checks for:
/// - federation being enabled (if its disabled, only local URLs are allowed)
/// - the correct scheme (either http or https)
/// - URL being in the allowlist (if it is active)
/// - URL not being in the blocklist (if it is active)
#[tracing::instrument(skip(local_site_data))]
fn check_apub_id_valid(apub_id: &Url, local_site_data: &LocalSiteData) -> Result<(), &'static str> {
  let domain = apub_id.domain().expect("apud id has domain").to_string();

  if !local_site_data
    .local_site
    .as_ref()
    .map(|l| l.federation_enabled)
    .unwrap_or(true)
  {
    return Err("Federation disabled");
  }

  if local_site_data
    .blocked_instances
    .iter()
    .any(|i| domain.eq(&i.domain))
  {
    return Err("Domain is blocked");
  }

  // Only check this if there are instances in the allowlist
  if !local_site_data.allowed_instances.is_empty()
    && !local_site_data
      .allowed_instances
      .iter()
      .any(|i| domain.eq(&i.domain))
  {
    return Err("Domain is not in allowlist");
  }

  Ok(())
}

#[derive(Clone)]
pub(crate) struct LocalSiteData {
  local_site: Option<LocalSite>,
  allowed_instances: Vec<Instance>,
  blocked_instances: Vec<Instance>,
}

pub(crate) async fn local_site_data_cached(pool: &DbPool) -> LemmyResult<Arc<LocalSiteData>> {
  static CACHE: Lazy<Cache<(), Arc<LocalSiteData>>> = Lazy::new(|| {
    Cache::builder()
      .max_capacity(1)
      .time_to_live(BLOCKLIST_CACHE_DURATION)
      .build()
  });
  Ok(
    CACHE
      .try_get_with((), async {
        let (local_site, allowed_instances, blocked_instances) = join3(
          LocalSite::read(pool),
          Instance::allowlist(pool),
          Instance::blocklist(pool),
        )
        .await;

        Ok::<_, diesel::result::Error>(Arc::new(LocalSiteData {
          // LocalSite may be missing
          local_site: local_site.ok(),
          allowed_instances: allowed_instances?,
          blocked_instances: blocked_instances?,
        }))
      })
      .await?,
  )
}

pub(crate) async fn check_apub_id_valid_with_strictness(
  apub_id: &Url,
  is_strict: bool,
  context: &LemmyContext,
) -> Result<(), LemmyError> {
  let domain = apub_id.domain().expect("apud id has domain").to_string();
  let local_instance = context
    .settings()
    .get_hostname_without_port()
    .expect("local hostname is valid");
  if domain == local_instance {
    return Ok(());
  }

  let local_site_data = local_site_data_cached(context.pool()).await?;
  check_apub_id_valid(apub_id, &local_site_data).map_err(LemmyError::from_message)?;

  // Only check allowlist if this is a community, and there are instances in the allowlist
  if is_strict && !local_site_data.allowed_instances.is_empty() {
    // need to allow this explicitly because apub receive might contain objects from our local
    // instance.
    let mut allowed_and_local = local_site_data
      .allowed_instances
      .iter()
      .map(|i| i.domain.clone())
      .collect::<Vec<String>>();
    let local_instance = context
      .settings()
      .get_hostname_without_port()
      .expect("local hostname is valid");
    allowed_and_local.push(local_instance);

    let domain = apub_id.domain().expect("apud id has domain").to_string();
    if !allowed_and_local.contains(&domain) {
      return Err(LemmyError::from_message(
        "Federation forbidden by strict allowlist",
      ));
    }
  }
  Ok(())
}

/// Store a sent or received activity in the database.
///
/// Stored activities are served over the HTTP endpoint `GET /activities/{type_}/{id}`. This also
/// ensures that the same activity cannot be received more than once.
#[tracing::instrument(skip(data, activity))]
async fn insert_activity<T>(
  ap_id: &Url,
  activity: &T,
  local: bool,
  sensitive: bool,
  data: &Data<LemmyContext>,
) -> Result<(), LemmyError>
where
  T: Serialize,
{
  let ap_id = ap_id.clone().into();
  let form = ActivityInsertForm {
    ap_id,
    data: serde_json::to_value(activity)?,
    local: Some(local),
    sensitive: Some(sensitive),
    updated: None,
  };
  Activity::create(data.pool(), &form).await?;
  Ok(())
}

#[async_trait::async_trait]
pub trait SendActivity: Sync {
  type Response: Sync + Send + Clone;

  async fn send_activity(
    _request: &Self,
    _response: &Self::Response,
    _context: &Data<LemmyContext>,
  ) -> Result<(), LemmyError> {
    Ok(())
  }
}