adjust default validation for resource parameter in client flow, and server example

src/shared/auth-utils.ts

@@ -7,8 +7,48 @@
  * RFC 8707 section 2 states that resource URIs "MUST NOT include a fragment component".
  * Keeps everything else unchanged (scheme, domain, port, path, query).
  */
-export function resourceUrlFromServerUrl(url: URL): URL {
-  const resourceURL = new URL(url.href);
+export function resourceUrlFromServerUrl(url: URL | string ): URL {
+  const resourceURL = typeof url === "string" ? new URL(url) : new URL(url.href);
   resourceURL.hash = ''; // Remove fragment
   return resourceURL;
 }
+
+/**
+ * Checks if a requested resource URL matches a configured resource URL.
+ * A requested resource matches if it has the same scheme, domain, port,
+ * and its path starts with the configured resource's path.
+ *
+ * @param requestedResource The resource URL being requested
+ * @param configuredResource The resource URL that has been configured
+ * @returns true if the requested resource matches the configured resource, false otherwise
+ */
+ export function checkResourceAllowed(
+   { requestedResource, configuredResource }: {
+     requestedResource: URL | string;
+     configuredResource: URL | string
+   }
+ ): boolean {
+   const requested = typeof requestedResource === "string" ? new URL(requestedResource) : new URL(requestedResource.href);
+   const configured = typeof configuredResource === "string" ? new URL(configuredResource) : new URL(configuredResource.href);
+
+   // Compare the origin (scheme, domain, and port)
+   if (requested.origin !== configured.origin) {
+     return false;
+   }
+
+   // Handle cases like requested=/foo and configured=/foo/
+   if (requested.pathname.length < configured.pathname.length) {
+     return false
+   }
+
+   // Check if the requested path starts with the configured path
+   // Ensure both paths end with / for proper comparison
+   // This ensures that if we have paths like "/api" and "/api/users",
+   // we properly detect that "/api/users" is a subpath of "/api"
+   // By adding a trailing slash if missing, we avoid false positives
+   // where paths like "/api123" would incorrectly match "/api"
+   const requestedPath = requested.pathname.endsWith('/') ? requested.pathname : requested.pathname + '/';
+   const configuredPath = configured.pathname.endsWith('/') ? configured.pathname : configured.pathname + '/';
+
+   return requestedPath.startsWith(configuredPath);
+ }