Setup the device link form page

crates/handlers/src/lib.rs

@@ -404,6 +404,10 @@ where
             mas_router::UpstreamOAuth2Link::route(),
             get(self::upstream_oauth2::link::get).post(self::upstream_oauth2::link::post),
         )
+        .route(
+            mas_router::DeviceCodeLink::route(),
+            get(self::oauth2::device::link::get).post(self::oauth2::device::link::post),
+        )
         .layer(AndThenLayer::new(
             move |response: axum::response::Response| async move {
                 if response.status().is_server_error() {

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

@@ -0,0 +1,102 @@
+// Copyright 2023 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.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use axum::{
+    extract::{Query, State},
+    response::IntoResponse,
+    Form,
+};
+use axum_extra::response::Html;
+use mas_axum_utils::{
+    cookies::CookieJar,
+    csrf::{CsrfExt, ProtectedForm},
+    FancyError,
+};
+use mas_storage::{BoxClock, BoxRng};
+use mas_templates::{
+    DeviceLinkContext, DeviceLinkFormField, FieldError, FormState, TemplateContext, Templates,
+};
+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,
+}
+
+#[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,
+    PreferredLanguage(locale): PreferredLanguage,
+    State(templates): State<Templates>,
+    cookie_jar: CookieJar,
+    Form(form): Form<ProtectedForm<Params>>,
+) -> Result<impl IntoResponse, FancyError> {
+    let form = cookie_jar.verify_form(&clock, form)?;
+    let (csrf_token, cookie_jar) = cookie_jar.csrf_token(&clock, &mut rng);
+
+    let form_state = FormState::from_form(&form)
+        .with_error_on_field(DeviceLinkFormField::Code, FieldError::Required);
+
+    // TODO: find the device code grant in the database
+    // and redirect to /oauth2/device/link/:id
+    // That then will trigger a login if we don't have a session
+
+    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)))
+}

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

@@ -0,0 +1,15 @@
+// Copyright 2023 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.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+pub mod link;

crates/handlers/src/oauth2/mod.rs

@@ -32,6 +32,7 @@ use thiserror::Error;
 
 pub mod authorization;
 pub mod consent;
+pub mod device;
 pub mod discovery;
 pub mod introspection;
 pub mod keys;

crates/router/src/endpoints.rs

@@ -689,6 +689,23 @@ impl Route for UpstreamOAuth2Link {
     }
 }
 
+/// `GET|POST /link`
+#[derive(Default, Serialize, Deserialize, Debug, Clone)]
+pub struct DeviceCodeLink {
+    code: Option<String>,
+}
+
+impl Route for DeviceCodeLink {
+    type Query = DeviceCodeLink;
+    fn route() -> &'static str {
+        "/link"
+    }
+
+    fn query(&self) -> Option<&Self::Query> {
+        Some(self)
+    }
+}
+
 /// `GET /assets`
 pub struct StaticAsset {
     path: String,

crates/templates/src/context.rs

@@ -1,4 +1,4 @@
-// Copyright 2021 The Matrix.org Foundation C.I.C.
+// Copyright 2021-2023 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.
@@ -104,7 +104,7 @@ impl TemplateContext for () {
 }
 
 /// Context with a specified locale in it
-#[derive(Serialize)]
+#[derive(Serialize, Debug)]
 pub struct WithLanguage<T> {
     lang: String,
 
@@ -143,7 +143,7 @@ impl<T: TemplateContext> TemplateContext for WithLanguage<T> {
 }
 
 /// Context with a CSRF token in it
-#[derive(Serialize)]
+#[derive(Serialize, Debug)]
 pub struct WithCsrf<T> {
     csrf_token: String,
 
@@ -1023,6 +1023,58 @@ impl TemplateContext for UpstreamRegister {
     }
 }
 
+/// Form fields on the device link page
+#[derive(Serialize, Deserialize, Debug, Clone, Copy, Hash, PartialEq, Eq)]
+#[serde(rename_all = "snake_case")]
+pub enum DeviceLinkFormField {
+    /// The device code field
+    Code,
+}
+
+impl FormField for DeviceLinkFormField {
+    fn keep(&self) -> bool {
+        match self {
+            Self::Code => true,
+        }
+    }
+}
+
+/// Context used by the `device_link.html` template
+#[derive(Serialize, Default, Debug)]
+pub struct DeviceLinkContext {
+    form_state: FormState<DeviceLinkFormField>,
+}
+
+impl DeviceLinkContext {
+    /// Constructs a new context with an existing linked user
+    #[must_use]
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Set the form state
+    #[must_use]
+    pub fn with_form_state(mut self, form_state: FormState<DeviceLinkFormField>) -> Self {
+        self.form_state = form_state;
+        self
+    }
+}
+
+impl TemplateContext for DeviceLinkContext {
+    fn sample(_now: chrono::DateTime<Utc>, _rng: &mut impl Rng) -> Vec<Self>
+    where
+        Self: Sized,
+    {
+        vec![
+            Self::new(),
+            Self::new().with_form_state(
+                FormState::default()
+                    .with_error_on_field(DeviceLinkFormField::Code, FieldError::Required),
+            ),
+        ]
+    }
+}
+
 /// Context used by the `form_post.html` template
 #[derive(Serialize)]
 pub struct FormPostContext<T> {

crates/templates/src/lib.rs

@@ -42,13 +42,13 @@ mod macros;
 
 pub use self::{
     context::{
-        AppContext, CompatSsoContext, ConsentContext, EmailAddContext, EmailVerificationContext,
-        EmailVerificationPageContext, EmptyContext, ErrorContext, FormPostContext, IndexContext,
-        LoginContext, LoginFormField, NotFoundContext, PolicyViolationContext, PostAuthContext,
-        PostAuthContextInner, ReauthContext, ReauthFormField, RegisterContext, RegisterFormField,
-        SiteBranding, TemplateContext, UpstreamExistingLinkContext, UpstreamRegister,
-        UpstreamRegisterFormField, UpstreamSuggestLink, WithCsrf, WithLanguage,
-        WithOptionalSession, WithSession,
+        AppContext, CompatSsoContext, ConsentContext, DeviceLinkContext, DeviceLinkFormField,
+        EmailAddContext, EmailVerificationContext, EmailVerificationPageContext, EmptyContext,
+        ErrorContext, FormPostContext, IndexContext, LoginContext, LoginFormField, NotFoundContext,
+        PolicyViolationContext, PostAuthContext, PostAuthContextInner, ReauthContext,
+        ReauthFormField, RegisterContext, RegisterFormField, SiteBranding, TemplateContext,
+        UpstreamExistingLinkContext, UpstreamRegister, UpstreamRegisterFormField,
+        UpstreamSuggestLink, WithCsrf, WithLanguage, WithOptionalSession, WithSession,
     },
     forms::{FieldError, FormError, FormField, FormState, ToFormState},
 };
@@ -365,6 +365,9 @@ register_templates! {
 
     /// Render the upstream register screen
     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" }
 }
 
 impl Templates {