lemmy/crates/apub/src/activities/mod.rs

use crate::{
  check_is_apub_id_valid,
  context::WithContext,
  fetcher::object_id::ObjectId,
  generate_moderators_url,
  insert_activity,
  objects::{community::ApubCommunity, person::ApubPerson},
};
use activitystreams::public;
use anyhow::anyhow;
use lemmy_api_common::blocking;
use lemmy_apub_lib::{
  activity_queue::send_activity,
  traits::{ActivityFields, ActorType},
  verify::verify_domains_match,
};
use lemmy_db_schema::source::community::Community;
use lemmy_db_views_actor::{
  community_person_ban_view::CommunityPersonBanView,
  community_view::CommunityView,
};
use lemmy_utils::{settings::structs::Settings, LemmyError};
use lemmy_websocket::LemmyContext;
use log::info;
use serde::Serialize;
use url::{ParseError, Url};
use uuid::Uuid;

pub mod comment;
pub mod community;
pub mod deletion;
pub mod following;
pub mod post;
pub mod private_message;
pub mod voting;

/// Checks that the specified Url actually identifies a Person (by fetching it), and that the person
/// doesn't have a site ban.
async fn verify_person(
  person_id: &ObjectId<ApubPerson>,
  context: &LemmyContext,
  request_counter: &mut i32,
) -> Result<(), LemmyError> {
  let person = person_id.dereference(context, request_counter).await?;
  if person.banned {
    return Err(anyhow!("Person {} is banned", person_id).into());
  }
  Ok(())
}

/// Fetches the person and community to verify their type, then checks if person is banned from site
/// or community.
pub(crate) async fn verify_person_in_community(
  person_id: &ObjectId<ApubPerson>,
  community: &ApubCommunity,
  context: &LemmyContext,
  request_counter: &mut i32,
) -> Result<(), LemmyError> {
  let person = person_id.dereference(context, request_counter).await?;
  if person.banned {
    return Err(anyhow!("Person is banned from site").into());
  }
  let person_id = person.id;
  let community_id = community.id;
  let is_banned =
    move |conn: &'_ _| CommunityPersonBanView::get(conn, person_id, community_id).is_ok();
  if blocking(context.pool(), is_banned).await? {
    return Err(anyhow!("Person is banned from community").into());
  }

  Ok(())
}

fn verify_activity(activity: &dyn ActivityFields, settings: &Settings) -> Result<(), LemmyError> {
  check_is_apub_id_valid(activity.actor(), false, settings)?;
  verify_domains_match(activity.id_unchecked(), activity.actor())?;
  Ok(())
}

/// Verify that the actor is a community mod. This check is only run if the community is local,
/// because in case of remote communities, admins can also perform mod actions. As admin status
/// is not federated, we cant verify their actions remotely.
pub(crate) async fn verify_mod_action(
  actor_id: &ObjectId<ApubPerson>,
  community: &ApubCommunity,
  context: &LemmyContext,
  request_counter: &mut i32,
) -> Result<(), LemmyError> {
  if community.local {
    let actor = actor_id.dereference(context, request_counter).await?;

    // Note: this will also return true for admins in addition to mods, but as we dont know about
    //       remote admins, it doesnt make any difference.
    let community_id = community.id;
    let actor_id = actor.id;
    let is_mod_or_admin = blocking(context.pool(), move |conn| {
      CommunityView::is_mod_or_admin(conn, actor_id, community_id)
    })
    .await?;
    if !is_mod_or_admin {
      return Err(anyhow!("Not a mod").into());
    }
  }
  Ok(())
}

/// For Add/Remove community moderator activities, check that the target field actually contains
/// /c/community/moderators. Any different values are unsupported.
fn verify_add_remove_moderator_target(
  target: &Url,
  community: &ApubCommunity,
) -> Result<(), LemmyError> {
  if target != &generate_moderators_url(&community.actor_id)?.into_inner() {
    return Err(anyhow!("Unkown target url").into());
  }
  Ok(())
}

pub(crate) fn verify_is_public(to: &[Url]) -> Result<(), LemmyError> {
  if !to.contains(&public()) {
    return Err(anyhow!("Object is not public").into());
  }
  Ok(())
}

pub(crate) fn check_community_deleted_or_removed(community: &Community) -> Result<(), LemmyError> {
  if community.deleted || community.removed {
    Err(anyhow!("New post or comment cannot be created in deleted or removed community").into())
  } else {
    Ok(())
  }
}

/// Generate a unique ID for an activity, in the format:
/// `http(s)://example.com/receive/create/202daf0a-1489-45df-8d2e-c8a3173fed36`
fn generate_activity_id<T>(kind: T, protocol_and_hostname: &str) -> Result<Url, ParseError>
where
  T: ToString,
{
  let id = format!(
    "{}/activities/{}/{}",
    protocol_and_hostname,
    kind.to_string().to_lowercase(),
    Uuid::new_v4()
  );
  Url::parse(&id)
}

async fn send_lemmy_activity<T: Serialize>(
  context: &LemmyContext,
  activity: &T,
  activity_id: &Url,
  actor: &dyn ActorType,
  inboxes: Vec<Url>,
  sensitive: bool,
) -> Result<(), LemmyError> {
  if !context.settings().federation.enabled || inboxes.is_empty() {
    return Ok(());
  }
  let activity = WithContext::new(activity);

  info!("Sending activity {}", activity_id.to_string());

  // Don't send anything to ourselves
  // TODO: this should be a debug assert
  let hostname = context.settings().get_hostname_without_port()?;
  let inboxes: Vec<&Url> = inboxes
    .iter()
    .filter(|i| i.domain().expect("valid inbox url") != hostname)
    .collect();

  let serialised_activity = serde_json::to_string(&activity)?;

  insert_activity(
    activity_id,
    serialised_activity.clone(),
    true,
    sensitive,
    context.pool(),
  )
  .await?;

  send_activity(
    serialised_activity,
    actor,
    inboxes,
    context.client(),
    context.activity_queue(),
  )
  .await
}