Skip the device code form when using the full verification URI

This changes the form to use a GET method, as it is only really doing
a redirect.

crates/handlers/src/lib.rs

@@ -412,7 +412,7 @@ where
         )
         .route(
             mas_router::DeviceCodeLink::route(),
-            get(self::oauth2::device::link::get).post(self::oauth2::device::link::post),
+            get(self::oauth2::device::link::get),
         )
         .route(
             mas_router::DeviceCodeConsent::route(),

crates/handlers/src/oauth2/device/link.rs

@@ -1,4 +1,4 @@
-// Copyright 2023 The Matrix.org Foundation C.I.C.
+// Copyright 2023, 2024 The Matrix.org Foundation C.I.C.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -14,17 +14,12 @@
 
 use axum::{
     extract::{Query, State},
-    response::{IntoResponse, Response},
-    Form,
+    response::IntoResponse,
 };
 use axum_extra::response::Html;
-use mas_axum_utils::{
-    cookies::CookieJar,
-    csrf::{CsrfExt, ProtectedForm},
-    FancyError,
-};
+use mas_axum_utils::{cookies::CookieJar, FancyError};
 use mas_router::UrlBuilder;
-use mas_storage::{BoxClock, BoxRepository, BoxRng};
+use mas_storage::{BoxClock, BoxRepository};
 use mas_templates::{
     DeviceLinkContext, DeviceLinkFormField, FieldError, FormState, TemplateContext, Templates,
 };
@@ -32,10 +27,6 @@ use serde::{Deserialize, Serialize};
 
 use crate::PreferredLanguage;
 
-// We use this struct for both the form and the query parameters. This is useful
-// to build a form state from the query parameters. The query parameter is only
-// really used when the `verification_uri_complete` feature of the device code
-// grant is used.
 #[derive(Serialize, Deserialize)]
 pub struct Params {
     code: String,
@@ -43,76 +34,49 @@ pub struct Params {
 
 #[tracing::instrument(name = "handlers.oauth2.device.link.get", skip_all, err)]
 pub(crate) async fn get(
-    mut rng: BoxRng,
-    clock: BoxClock,
-    PreferredLanguage(locale): PreferredLanguage,
-    State(templates): State<Templates>,
-    cookie_jar: CookieJar,
-    query: Option<Query<Params>>,
-) -> Result<impl IntoResponse, FancyError> {
-    let (csrf_token, cookie_jar) = cookie_jar.csrf_token(&clock, &mut rng);
-
-    let mut form_state = FormState::default();
-
-    // XXX: right now we just get the code from the query to pre-fill the form. We
-    // may want to make the form readonly instead at some point? tbd
-    if let Some(Query(params)) = query {
-        // Validate that it's a full code
-        if params.code.len() == 6 && params.code.chars().all(|c| c.is_ascii_alphanumeric()) {
-            form_state = FormState::from_form(&params);
-        }
-    };
-
-    let ctx = DeviceLinkContext::new()
-        .with_form_state(form_state)
-        .with_csrf(csrf_token.form_value())
-        .with_language(locale);
-
-    let content = templates.render_device_link(&ctx)?;
-
-    Ok((cookie_jar, Html(content)))
-}
-
-#[tracing::instrument(name = "handlers.oauth2.device.link.post", skip_all, err)]
-pub(crate) async fn post(
-    mut rng: BoxRng,
     clock: BoxClock,
     mut repo: BoxRepository,
     PreferredLanguage(locale): PreferredLanguage,
     State(templates): State<Templates>,
     State(url_builder): State<UrlBuilder>,
     cookie_jar: CookieJar,
-    Form(form): Form<ProtectedForm<Params>>,
-) -> Result<Response, FancyError> {
-    let form = cookie_jar.verify_form(&clock, form)?;
-    let (csrf_token, cookie_jar) = cookie_jar.csrf_token(&clock, &mut rng);
+    query: Option<Query<Params>>,
+) -> Result<impl IntoResponse, FancyError> {
+    let mut form_state = FormState::default();
 
-    let code = form.code.to_uppercase();
-    let grant = repo
-        .oauth2_device_code_grant()
-        .find_by_user_code(&code)
-        .await?
-        // XXX: We should have different error messages for already exchanged and expired
-        .filter(|grant| grant.is_pending())
-        .filter(|grant| grant.expires_at > clock.now());
+    // If we have a code in query, find it in the database
+    if let Some(Query(params)) = query {
+        // Save the form state so that we echo back the code
+        form_state = FormState::from_form(&params);
 
-    let Some(grant) = grant else {
-        let form_state = FormState::from_form(&form)
-            .with_error_on_field(DeviceLinkFormField::Code, FieldError::Invalid);
+        // Find the code in the database
+        let code = params.code.to_uppercase();
+        let grant = repo
+            .oauth2_device_code_grant()
+            .find_by_user_code(&code)
+            .await?
+            // XXX: We should have different error messages for already exchanged and expired
+            .filter(|grant| grant.is_pending())
+            .filter(|grant| grant.expires_at > clock.now());
 
-        let ctx = DeviceLinkContext::new()
-            .with_form_state(form_state)
-            .with_csrf(csrf_token.form_value())
-            .with_language(locale);
+        if let Some(grant) = grant {
+            // This is a valid code, redirect to the consent page
+            // This will in turn redirect to the login page if the user is not logged in
+            let destination = url_builder.redirect(&mas_router::DeviceCodeConsent::new(grant.id));
 
-        let content = templates.render_device_link(&ctx)?;
+            return Ok((cookie_jar, destination).into_response());
+        }
 
-        return Ok((cookie_jar, Html(content)).into_response());
+        // The code isn't valid, set an error on the form
+        form_state = form_state.with_error_on_field(DeviceLinkFormField::Code, FieldError::Invalid);
     };
 
-    // Redirect to the consent page
-    // This will in turn redirect to the login page if the user is not logged in
-    let destination = url_builder.redirect(&mas_router::DeviceCodeConsent::new(grant.id));
+    // Rendre the form
+    let ctx = DeviceLinkContext::new()
+        .with_form_state(form_state)
+        .with_language(locale);
 
-    Ok((cookie_jar, destination).into_response())
+    let content = templates.render_device_link(&ctx)?;
+
+    Ok((cookie_jar, Html(content)).into_response())
 }

crates/templates/src/lib.rs

@@ -377,7 +377,7 @@ register_templates! {
     pub fn render_upstream_oauth2_do_register(WithLanguage<WithCsrf<UpstreamRegister>>) { "pages/upstream_oauth2/do_register.html" }
 
     /// Render the device code link page
-    pub fn render_device_link(WithLanguage<WithCsrf<DeviceLinkContext>>) { "pages/device_link.html" }
+    pub fn render_device_link(WithLanguage<DeviceLinkContext>) { "pages/device_link.html" }
 
     /// Render the device code consent page
     pub fn render_device_consent(WithLanguage<WithCsrf<WithSession<DeviceConsentContext>>>) { "pages/device_consent.html" }