chore: impl default value for callback_url

Author: Jeidnx

src/core/config/mod.rs

@@ -2635,11 +2635,10 @@ pub struct IdentityProvider {
 	pub issuer_url: Option<Url>,
 
 	/// The callback URL configured when registering the OAuth application with
-	/// the provider. Tuwunel's callback URL must be strictly formatted exactly
-	/// as instructed. The URL host must point directly at the matrix server and
-	/// use the following path:
-	/// `/_matrix/client/unstable/login/sso/callback/<client_id>` where
-	/// `<client_id>` is the same one configured for this provider above.
+	/// the provider. This doesn't need to be set manually, it will be
+	/// constructed as:
+	/// `<global.well_known.client>/_matrix/client/unstable/login/sso/callback/
+	/// <client_id>`
 	pub callback_url: Option<Url>,
 
 	/// When more than one identity_provider has been configured and
@@ -2698,10 +2697,13 @@ pub struct IdentityProvider {
 	#[serde(default)]
 	pub userid_claims: BTreeSet<String>,
 
-	/// Optional extra path components after the issuer_url leading to the
-	/// location of the `.well-known` directory used for discovery. This will be
-	/// empty for specification-compliant providers. We have supplied any known
-	/// values based on `brand` (e.g. `/login/oauth` for GitHub).
+	/// Optionally overwrite the path used for the discovery url. If base_path
+	/// starts with a / the issuer path is ignored and the discovery url is
+	/// constructed from the host + base_path + well-known path. If base_path is
+	/// a relative path, it will be constructed relative to the issuer
+	/// path. This should be empty for specification-compliant providers. We
+	/// have supplied any known values based on `brand` (e.g. `/login/oauth`
+	/// for GitHub).
 	pub base_path: Option<String>,
 
 	/// Overrides the `.well-known` location where the provider's openid

src/service/oauth/providers.rs

@@ -123,6 +123,25 @@ async fn configure(&self, mut provider: Provider) -> Result<Provider> {
 		.name
 		.get_or_insert_with(|| provider.brand.clone());
 
+	if provider.callback_url.is_none() {
+		let server_url = self
+			.services
+			.config
+			.well_known
+			.client
+			.as_ref()
+			.expect("should be set");
+
+		let callback_path =
+			format!("_matrix/client/unstable/login/sso/callback/{}", provider.client_id);
+
+		provider.callback_url = Some(
+			server_url
+				.join(&callback_path)
+				.expect("valid callback url"),
+		);
+	}
+
 	if provider.brand == "github" {
 		return configure_github(provider);
 	}