Add validate_auth api endpoint (fixes #3702) (#4049)

* Add validate_auth api endpoint (fixes #3702)

* clippy

---------

Co-authored-by: Dessalines <dessalines@users.noreply.github.com>

crates/api/src/lib.rs

@@ -2,11 +2,15 @@ use actix_web::{http::header::Header, HttpRequest};
 use actix_web_httpauth::headers::authorization::{Authorization, Bearer};
 use base64::{engine::general_purpose::STANDARD_NO_PAD as base64, Engine};
 use captcha::Captcha;
-use lemmy_api_common::utils::{local_site_to_slur_regex, AUTH_COOKIE_NAME};
+use lemmy_api_common::{
+  claims::Claims,
+  context::LemmyContext,
+  utils::{check_user_valid, local_site_to_slur_regex, AUTH_COOKIE_NAME},
+};
 use lemmy_db_schema::source::local_site::LocalSite;
 use lemmy_db_views::structs::LocalUserView;
 use lemmy_utils::{
-  error::{LemmyError, LemmyErrorExt, LemmyErrorType, LemmyResult},
+  error::{LemmyError, LemmyErrorExt, LemmyErrorExt2, LemmyErrorType, LemmyResult},
   utils::slurs::check_slurs,
 };
 use std::io::Cursor;
@@ -144,6 +148,20 @@ pub(crate) fn build_totp_2fa(
   .with_lemmy_type(LemmyErrorType::CouldntGenerateTotp)
 }
 
+#[tracing::instrument(skip_all)]
+pub async fn local_user_view_from_jwt(
+  jwt: &str,
+  context: &LemmyContext,
+) -> Result<LocalUserView, LemmyError> {
+  let local_user_id = Claims::validate(jwt, context)
+    .await
+    .with_lemmy_type(LemmyErrorType::NotLoggedIn)?;
+  let local_user_view = LocalUserView::read(&mut context.pool(), local_user_id).await?;
+  check_user_valid(&local_user_view.person)?;
+
+  Ok(local_user_view)
+}
+
 #[cfg(test)]
 mod tests {
   #![allow(clippy::unwrap_used)]

crates/api/src/local_user/mod.rs

@@ -14,4 +14,5 @@ pub mod report_count;
 pub mod reset_password;
 pub mod save_settings;
 pub mod update_totp;
+pub mod validate_auth;
 pub mod verify_email;

crates/api/src/local_user/validate_auth.rs

@@ -0,0 +1,23 @@
+use crate::{local_user_view_from_jwt, read_auth_token};
+use actix_web::{
+  web::{Data, Json},
+  HttpRequest,
+};
+use lemmy_api_common::{context::LemmyContext, SuccessResponse};
+use lemmy_utils::error::{LemmyError, LemmyErrorType};
+
+/// Returns an error message if the auth token is invalid for any reason. Necessary because other
+/// endpoints silently treat any call with invalid auth as unauthenticated.
+#[tracing::instrument(skip(context))]
+pub async fn validate_auth(
+  req: HttpRequest,
+  context: Data<LemmyContext>,
+) -> Result<Json<SuccessResponse>, LemmyError> {
+  let jwt = read_auth_token(&req)?;
+  if let Some(jwt) = jwt {
+    local_user_view_from_jwt(&jwt, &context).await?;
+  } else {
+    Err(LemmyErrorType::NotLoggedIn)?;
+  }
+  Ok(Json(SuccessResponse::default()))
+}

src/api_routes_http.rs

@@ -38,6 +38,7 @@ use lemmy_api::{
     reset_password::reset_password,
     save_settings::save_user_settings,
     update_totp::update_totp,
+    validate_auth::validate_auth,
     verify_email::verify_email,
   },
   post::{
@@ -296,7 +297,8 @@ pub fn config(cfg: &mut web::ServiceConfig, rate_limit: &RateLimitCell) {
           .route("/leave_admin", web::post().to(leave_admin))
           .route("/totp/generate", web::post().to(generate_totp_secret))
           .route("/totp/update", web::post().to(update_totp))
-          .route("/list_logins", web::get().to(list_logins)),
+          .route("/list_logins", web::get().to(list_logins))
+          .route("/validate_auth", web::get().to(validate_auth)),
       )
       .service(
         web::scope("/user")

src/session_middleware.rs

@@ -7,14 +7,8 @@ use actix_web::{
 };
 use core::future::Ready;
 use futures_util::future::LocalBoxFuture;
-use lemmy_api::read_auth_token;
-use lemmy_api_common::{
-  claims::Claims,
-  context::LemmyContext,
-  lemmy_db_views::structs::LocalUserView,
-  utils::check_user_valid,
-};
-use lemmy_utils::error::{LemmyError, LemmyErrorExt2, LemmyErrorType};
+use lemmy_api::{local_user_view_from_jwt, read_auth_token};
+use lemmy_api_common::context::LemmyContext;
 use reqwest::header::HeaderValue;
 use std::{future::ready, rc::Rc};
 
@@ -100,20 +94,6 @@ where
   }
 }
 
-#[tracing::instrument(skip_all)]
-async fn local_user_view_from_jwt(
-  jwt: &str,
-  context: &LemmyContext,
-) -> Result<LocalUserView, LemmyError> {
-  let local_user_id = Claims::validate(jwt, context)
-    .await
-    .with_lemmy_type(LemmyErrorType::NotLoggedIn)?;
-  let local_user_view = LocalUserView::read(&mut context.pool(), local_user_id).await?;
-  check_user_valid(&local_user_view.person)?;
-
-  Ok(local_user_view)
-}
-
 #[cfg(test)]
 mod tests {
   #![allow(clippy::unwrap_used)]
@@ -121,6 +101,7 @@ mod tests {
 
   use super::*;
   use actix_web::test::TestRequest;
+  use lemmy_api_common::claims::Claims;
   use lemmy_db_schema::{
     source::{
       instance::Instance,