From 29da0229749976c4e251fe964babd685a9cc35b3 Mon Sep 17 00:00:00 2001
From: Bastien <bastien.wermeille@gmail.com>
Date: Mon, 20 Nov 2023 14:47:51 +0100
Subject: [PATCH 1/4] fix: allow redirection after login

---
 multiauthenticator/multiauthenticator.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/multiauthenticator/multiauthenticator.py b/multiauthenticator/multiauthenticator.py
index 61b881e..88d7de9 100644
--- a/multiauthenticator/multiauthenticator.py
+++ b/multiauthenticator/multiauthenticator.py
@@ -137,7 +137,7 @@ def get_custom_html(self, base_url):
             html.append(
                 f"""
                 <div class="service-login">
-                  <a role="button" class='btn btn-jupyter btn-lg' href='{url}'>
+                  <a role="button" class='btn btn-jupyter btn-lg' href='{url}{{% if next is defined %}}?next={{{{next}}}}{{% endif %}}'>
                     Sign in with {login_service}
                   </a>
                 </div>

From 375e8904577a581377edb01a992531d7c3c1875f Mon Sep 17 00:00:00 2001
From: Bastien <bastien.wermeille@gmail.com>
Date: Mon, 20 Nov 2023 15:10:13 +0100
Subject: [PATCH 2/4] fix: allow redirection after login

---
 multiauthenticator/multiauthenticator.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/multiauthenticator/multiauthenticator.py b/multiauthenticator/multiauthenticator.py
index 88d7de9..48b488b 100644
--- a/multiauthenticator/multiauthenticator.py
+++ b/multiauthenticator/multiauthenticator.py
@@ -137,7 +137,7 @@ def get_custom_html(self, base_url):
             html.append(
                 f"""
                 <div class="service-login">
-                  <a role="button" class='btn btn-jupyter btn-lg' href='{url}{{% if next is defined %}}?next={{{{next}}}}{{% endif %}}'>
+                  <a role="button" class='btn btn-jupyter btn-lg' href='{url}{{% if next is defined and next|length %}}?next={{{{next}}}}{{% endif %}}'>
                     Sign in with {login_service}
                   </a>
                 </div>

From 0132e54429fa45ba4048b0b489ed6c8385d1fdc1 Mon Sep 17 00:00:00 2001
From: Samuel Gaist <samuel.gaist@idiap.ch>
Date: Mon, 20 Nov 2023 15:35:08 +0100
Subject: [PATCH 3/4] doc: annotate get_custom_html docstring to keep in mind
 that Jinja is involved

---
 multiauthenticator/multiauthenticator.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/multiauthenticator/multiauthenticator.py b/multiauthenticator/multiauthenticator.py
index 48b488b..dfe7040 100644
--- a/multiauthenticator/multiauthenticator.py
+++ b/multiauthenticator/multiauthenticator.py
@@ -123,7 +123,11 @@ def check_blocked_users(self, username, authentication=None):
             self._authenticators.append(authenticator)
 
     def get_custom_html(self, base_url):
-        """Re-implementation generating one login button per configured authenticator"""
+        """Re-implementation generating one login button per configured authenticator
+
+        Note: the html generated in this method will be passed through Jinja's template
+        rendering, see the login implementation in JupyterHub's sources.
+        """
 
         html = []
         for authenticator in self._authenticators:

From dc012232ad98759c0a97393d129f24ef074eb510 Mon Sep 17 00:00:00 2001
From: Samuel Gaist <samuel.gaist@idiap.ch>
Date: Mon, 20 Nov 2023 15:35:50 +0100
Subject: [PATCH 4/4] test: ensure next handling is working as expected

---
 .../tests/test_multiauthenticator.py          | 25 +++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/multiauthenticator/tests/test_multiauthenticator.py b/multiauthenticator/tests/test_multiauthenticator.py
index 4b55155..b288707 100644
--- a/multiauthenticator/tests/test_multiauthenticator.py
+++ b/multiauthenticator/tests/test_multiauthenticator.py
@@ -4,6 +4,7 @@
 """Test module for the MultiAuthenticator class"""
 import pytest
 
+from jinja2 import Template
 from jupyterhub.auth import DummyAuthenticator
 from jupyterhub.auth import PAMAuthenticator
 from oauthenticator import OAuthenticator
@@ -297,3 +298,27 @@ class MyAuthenticator(OAuthenticator):
         MultiAuthenticator()
 
     assert f"Login service cannot contain {PREFIX_SEPARATOR}" in str(excinfo.value)
+
+
+def test_next_handling():
+    MultiAuthenticator.authenticators = [
+        (
+            PAMAuthenticator,
+            "/pam",
+            {"service_name": "test-service", "allowed_users": {"test"}},
+        ),
+    ]
+
+    multi_authenticator = MultiAuthenticator()
+    html = multi_authenticator.get_custom_html("")
+
+    template = Template(html)
+
+    with_next = template.render({"next": "/next-destination"})
+    assert "href='pam/login?next=/next-destination'" in with_next
+
+    without_next = template.render()
+    assert "href='pam/login'" in without_next
+
+    with_empty_next = template.render({"next": ""})
+    assert "href='pam/login'" in with_empty_next