lemmy/server/src/routes/webfinger.rs

use crate::{
  db::{community::Community, user::User_},
  routes::DbPoolParam,
  Settings,
};
use actix_web::{error::ErrorBadRequest, web::Query, *};
use regex::Regex;
use serde::{Deserialize, Serialize};

#[derive(Deserialize)]
pub struct Params {
  resource: String,
}

#[derive(Serialize, Deserialize, Debug)]
pub struct WebFingerResponse {
  pub subject: String,
  pub aliases: Vec<String>,
  pub links: Vec<WebFingerLink>,
}

#[derive(Serialize, Deserialize, Debug)]
pub struct WebFingerLink {
  pub rel: Option<String>,
  #[serde(rename(serialize = "type", deserialize = "type"))]
  pub type_: Option<String>,
  pub href: Option<String>,
  #[serde(skip_serializing_if = "Option::is_none")]
  pub template: Option<String>,
}

pub fn config(cfg: &mut web::ServiceConfig) {
  if Settings::get().federation.enabled {
    cfg.route(
      ".well-known/webfinger",
      web::get().to(get_webfinger_response),
    );
  }
}

lazy_static! {
  static ref WEBFINGER_COMMUNITY_REGEX: Regex = Regex::new(&format!(
    "^group:([a-z0-9_]{{3, 20}})@{}$",
    Settings::get().hostname
  ))
  .unwrap();
  static ref WEBFINGER_USER_REGEX: Regex = Regex::new(&format!(
    "^acct:([a-z0-9_]{{3, 20}})@{}$",
    Settings::get().hostname
  ))
  .unwrap();
}

/// Responds to webfinger requests of the following format. There isn't any real documentation for
/// this, but it described in this blog post:
/// https://mastodon.social/.well-known/webfinger?resource=acct:gargron@mastodon.social
///
/// You can also view the webfinger response that Mastodon sends:
/// https://radical.town/.well-known/webfinger?resource=acct:felix@radical.town
async fn get_webfinger_response(
  info: Query<Params>,
  db: DbPoolParam,
) -> Result<HttpResponse, Error> {
  let res = web::block(move || {
    let conn = db.get()?;

    let community_regex_parsed = WEBFINGER_COMMUNITY_REGEX
      .captures(&info.resource)
      .map(|c| c.get(1))
      .flatten();

    let user_regex_parsed = WEBFINGER_USER_REGEX
      .captures(&info.resource)
      .map(|c| c.get(1))
      .flatten();

    let url = if let Some(community_name) = community_regex_parsed {
      // Make sure the requested community exists.
      let community = match Community::read_from_name(&conn, &community_name.as_str()) {
        Ok(o) => o,
        Err(_) => return Err(format_err!("not_found")),
      };
      community.actor_id
    } else if let Some(user_name) = user_regex_parsed {
      // Make sure the requested user exists.
      let user = match User_::read_from_name(&conn, &user_name.as_str()) {
        Ok(o) => o,
        Err(_) => return Err(format_err!("not_found")),
      };
      user.actor_id
    } else {
      return Err(format_err!("not_found"));
    };

    let wf_res = WebFingerResponse {
      subject: info.resource.to_owned(),
      aliases: vec![url.to_owned()],
      links: vec![
        WebFingerLink {
          rel: Some("http://webfinger.net/rel/profile-page".to_string()),
          type_: Some("text/html".to_string()),
          href: Some(url.to_owned()),
          template: None,
        },
        WebFingerLink {
          rel: Some("self".to_string()),
          type_: Some("application/activity+json".to_string()),
          href: Some(url),
          template: None,
        }, // TODO: this also needs to return the subscribe link once that's implemented
           //{
           //  "rel": "http://ostatus.org/schema/1.0/subscribe",
           //  "template": "https://my_instance.com/authorize_interaction?uri={uri}"
           //}
      ],
    };

    Ok(wf_res)
  })
  .await
  .map(|json| HttpResponse::Ok().json(json))
  .map_err(ErrorBadRequest)?;
  Ok(res)
}