feat: Add form-post specification (#8428)

* Added check for response mode in callback

* chore: lint

---------

Co-authored-by: Nico Domino <[email protected]>
Co-authored-by: Thang Vu <[email protected]>

Author: 3 people

packages/core/src/lib/actions/callback/index.ts

@@ -56,8 +56,15 @@ export async function callback(
 
   try {
     if (provider.type === "oauth" || provider.type === "oidc") {
+      // Use body if the response mode is set to form_post. For all other cases, use query
+      const payload =
+        provider.authorization?.url.searchParams.get("response_mode") ===
+        "form_post"
+          ? body
+          : query
+
       const { proxyRedirect, randomState } = handleState(
-        query,
+        payload,
         provider,
         options.isOnRedirectProxy
       )
@@ -68,7 +75,7 @@ export async function callback(
       }
 
       const authorizationResult = await handleOAuth(
-        query,
+        payload,
         request.cookies,
         options,
         randomState