From e22324adcd56f145cb55d0e2545471f30a39b9e1 Mon Sep 17 00:00:00 2001
From: Dario Ernst <dario@kanojo.de>
Date: Sun, 14 Apr 2019 11:37:09 +0000
Subject: [PATCH] Make aliases case-insensitive (too)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Even though RFC5321 2.4 explains that local-parts are to be case-sensitive,
this does not seem to be how EMail is used today. Thus, instead of reverting
user-emails back to being case sensitive, let’s make aliases case-insensitive
too. Not only more consistent, this also allows users to enjoy receiving EMails
from large airlines or car-rental agencies onto their already existing aliases.

For the rare case of case sensitive aliases existing, let’s query for the
forced-lowercase alias only in the event that the preserved-case one isn’t
found …

closes #867
---
 core/admin/mailu/models.py         | 39 +++++++++++++++++++++---------
 towncrier/newsfragments/867.bugfix |  1 +
 2 files changed, 29 insertions(+), 11 deletions(-)
 create mode 100644 towncrier/newsfragments/867.bugfix

diff --git a/core/admin/mailu/models.py b/core/admin/mailu/models.py
index 8bfb12fb..95dc16a6 100644
--- a/core/admin/mailu/models.py
+++ b/core/admin/mailu/models.py
@@ -436,20 +436,37 @@ class Alias(Base, Email):
 
     @classmethod
     def resolve(cls, localpart, domain_name):
-        return cls.query.filter(
-            sqlalchemy.and_(cls.domain_name == domain_name,
-                sqlalchemy.or_(
-                    sqlalchemy.and_(
-                        cls.wildcard == False,
-                        cls.localpart == localpart
-                    ), sqlalchemy.and_(
-                        cls.wildcard == True,
-                        sqlalchemy.bindparam("l", localpart).like(cls.localpart)
+        alias_preserve_case = cls.query.filter(
+                sqlalchemy.and_(cls.domain_name == domain_name,
+                    sqlalchemy.or_(
+                        sqlalchemy.and_(
+                            cls.wildcard == False,
+                            cls.localpart == localpart
+                        ), sqlalchemy.and_(
+                            cls.wildcard == True,
+                            sqlalchemy.bindparam("l", localpart).like(cls.localpart)
+                        )
                     )
                 )
-            )
-        ).order_by(cls.wildcard, sqlalchemy.func.char_length(cls.localpart).desc()).first()
+            ).order_by(cls.wildcard, sqlalchemy.func.char_length(cls.localpart).desc()).first()
+        if alias_preserve_case:
+            return alias_preserve_case
 
+        if localpart:
+            localpart = localpart.lower()
+        return cls.query.filter(
+                sqlalchemy.and_(cls.domain_name == domain_name,
+                    sqlalchemy.or_(
+                        sqlalchemy.and_(
+                            cls.wildcard == False,
+                            sqlalchemy.func.lower(cls.localpart) == localpart
+                        ), sqlalchemy.and_(
+                            cls.wildcard == True,
+                            sqlalchemy.bindparam("l", localpart).like(sqlalchemy.func.lower(cls.localpart))
+                        )
+                    )
+                )
+            ).order_by(cls.wildcard, sqlalchemy.func.char_length(sqlalchemy.func.lower(cls.localpart)).desc()).first()
 
 class Token(Base):
     """ A token is an application password for a given user.
diff --git a/towncrier/newsfragments/867.bugfix b/towncrier/newsfragments/867.bugfix
new file mode 100644
index 00000000..ef9b04a7
--- /dev/null
+++ b/towncrier/newsfragments/867.bugfix
@@ -0,0 +1 @@
+Make aliases optionally case-insensitive: After attempting to resolve an alias in its preserved case, also attempt to match it case-insensitively