From 1b9def4736fcf0fac98abac72a70ee5d8df239e6 Mon Sep 17 00:00:00 2001
From: Shannon Sterz <s.sterz@proxmox.com>
Date: Tue, 4 Mar 2025 15:42:35 +0100
Subject: [PATCH] auth-api: add logout method

adds a new endpoint that is useful when dealing with HttpOnly cookies
that cannot be removed by client-side javascript (and by extension
wasm) code. the logout handle simply removes the cookie that is used
for storing the current ticket. this works the same way as it does in
the front-end: by setting an expired cookie with the same name.

as cookies are now prefixed with `__Host-` by default, the cookie here
also needs to be `Secure` and have the same `Path` to not be rejected
by the browser before it can remove the old cookie.

Signed-off-by: Shannon Sterz <s.sterz@proxmox.com>
---
 proxmox-auth-api/src/api/access.rs | 29 ++++++++++++++++++++++++++++-
 proxmox-auth-api/src/api/mod.rs    |  2 +-
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/proxmox-auth-api/src/api/access.rs b/proxmox-auth-api/src/api/access.rs
index b91a2b6f..6dcda375 100644
--- a/proxmox-auth-api/src/api/access.rs
+++ b/proxmox-auth-api/src/api/access.rs
@@ -11,7 +11,7 @@ use proxmox_rest_server::{extract_cookie, RestEnvironment};
 use proxmox_router::{
     http_err, ApiHandler, ApiMethod, ApiResponseFuture, Permission, RpcEnvironment,
 };
-use proxmox_schema::{api, AllOfSchema, ApiType, ParameterSchema, ReturnType};
+use proxmox_schema::{api, AllOfSchema, ApiType, ObjectSchema, ParameterSchema, ReturnType};
 use proxmox_tfa::api::TfaChallenge;
 
 use super::ApiTicket;
@@ -63,6 +63,33 @@ pub async fn create_ticket(
     handle_ticket_creation(create_params, env).await
 }
 
+pub const API_METHOD_LOGOUT: ApiMethod = ApiMethod::new(
+    &ApiHandler::AsyncHttpBodyParameters(&logout_handler),
+    &ObjectSchema::new("", &[]),
+)
+.protected(true)
+.access(None, &Permission::World);
+
+fn logout_handler(
+    _parts: Parts,
+    _param: Value,
+    _info: &ApiMethod,
+    _rpcenv: Box<dyn RpcEnvironment>,
+) -> ApiResponseFuture {
+    Box::pin(async move {
+        // unset authentication cookie by setting an invalid one. needs the same `Path` and
+        // `Secure` parameter to not be rejected by some browsers. also use the same `HttpOnly` and
+        // `SameSite` parameters just in case.
+        let host_cookie = format!(
+            "{}=; Expires=Thu, 01 Jan 1970 00:00:00 GMT; Secure; SameSite=Lax; HttpOnly; Path=/;",
+            auth_context()?.prefixed_auth_cookie_name()
+        );
+
+        Ok(Response::builder()
+            .header(hyper::header::SET_COOKIE, host_cookie)
+            .body(Body::empty())?)
+    })
+}
 
 pub const API_METHOD_CREATE_TICKET_HTTP_ONLY: ApiMethod = ApiMethod::new_full(
     &ApiHandler::AsyncHttpBodyParameters(&create_ticket_http_only),
diff --git a/proxmox-auth-api/src/api/mod.rs b/proxmox-auth-api/src/api/mod.rs
index 3ee2d0e1..e176ea01 100644
--- a/proxmox-auth-api/src/api/mod.rs
+++ b/proxmox-auth-api/src/api/mod.rs
@@ -20,7 +20,7 @@ use access::verify_csrf_prevention_token;
 
 pub use access::{
     assemble_csrf_prevention_token, create_ticket, API_METHOD_CREATE_TICKET,
-    API_METHOD_CREATE_TICKET_HTTP_ONLY,
+    API_METHOD_CREATE_TICKET_HTTP_ONLY, API_METHOD_LOGOUT,
 };
 pub use ticket::{ApiTicket, PartialTicket};