avatar: Use fixed avatars for system bots.

This makes a Zulip server more isolated than relying on gravatar, and
avoids complex logistics if in the future we move system bots to live
inside individual realms.

Co-authored-by: PieterCK <pieterceka123@gmail.com>

zerver/lib/avatar.py

@@ -13,6 +13,12 @@ from zerver.lib.upload import get_avatar_url
 from zerver.lib.url_encoding import append_url_query_string
 from zerver.models import UserProfile
 
+SYSTEM_BOTS_AVATAR_FILES = {
+    settings.WELCOME_BOT: "images/welcome-bot.png",
+    settings.NOTIFICATION_BOT: "images/logo/zulip-icon-square.svg",
+    settings.EMAIL_GATEWAY_BOT: "images/email-gateway-bot.png",
+}
+
 
 def avatar_url(
     user_profile: UserProfile, medium: bool = False, client_gravatar: bool = False
@@ -54,6 +60,11 @@ def get_avatar_field(
             computing them on the server (mostly to save bandwidth).
     """
 
+    # System bots have hardcoded avatars
+    system_bot_avatar = SYSTEM_BOTS_AVATAR_FILES.get(email)
+    if system_bot_avatar:
+        return staticfiles_storage.url(system_bot_avatar)
+
     """
     If our client knows how to calculate gravatar hashes, we
     will return None and let the client compute the gravatar

zerver/lib/server_initialization.py

@@ -70,6 +70,9 @@ def create_internal_realm() -> None:
     bots = UserProfile.objects.filter(email__in=[bot_info[1] for bot_info in internal_bots])
     for bot in bots:
         bot.bot_owner = bot
+        # Avatars for system bots are hardcoded, so make sure gravatar
+        # won't be used..
+        bot.avatar_source = "U"
         bot.save()
 
     # Initialize the email gateway bot as able to forge senders.

zerver/migrations/0615_system_bot_avatars.py

@@ -0,0 +1,46 @@
+# Generated by Django 5.0.9 on 2024-10-14 23:22
+
+from django.conf import settings
+from django.db import migrations
+from django.db.backends.base.schema import BaseDatabaseSchemaEditor
+from django.db.migrations.state import StateApps
+
+
+def set_system_bot_avatar_source_user(
+    apps: StateApps, schema_editor: BaseDatabaseSchemaEditor
+) -> None:
+    UserProfile = apps.get_model("zerver", "UserProfile")
+    UserProfile.objects.filter(
+        email__in=[
+            settings.EMAIL_GATEWAY_BOT,
+            settings.NOTIFICATION_BOT,
+            settings.WELCOME_BOT,
+        ]
+    ).update(avatar_source="U")
+
+
+def set_system_bot_avatar_source_gravatar(
+    apps: StateApps, schema_editor: BaseDatabaseSchemaEditor
+) -> None:
+    UserProfile = apps.get_model("zerver", "UserProfile")
+    UserProfile.objects.filter(
+        email__in=[
+            settings.EMAIL_GATEWAY_BOT,
+            settings.NOTIFICATION_BOT,
+            settings.WELCOME_BOT,
+        ]
+    ).update(avatar_source="G")
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("zerver", "0614_remove_realm_move_messages_between_streams_policy"),
+    ]
+
+    operations = [
+        migrations.RunPython(
+            set_system_bot_avatar_source_user,
+            elidable=True,
+            reverse_code=set_system_bot_avatar_source_gravatar,
+        ),
+    ]

zerver/tests/test_upload.py

@@ -1256,12 +1256,12 @@ class AvatarTest(UploadSerializeMixin, ZulipTestCase):
             # Test cross_realm_bot avatar access using email.
             response = self.api_get(hamlet, "/avatar/welcome-bot@zulip.com", {"foo": "bar"})
             redirect_url = response["Location"]
-            self.assertTrue(redirect_url.endswith(str(avatar_url(cross_realm_bot)) + "&foo=bar"))
+            self.assertTrue(redirect_url.endswith(str(avatar_url(cross_realm_bot)) + "?foo=bar"))
 
             # Test cross_realm_bot avatar access using id.
             response = self.api_get(hamlet, f"/avatar/{cross_realm_bot.id}", {"foo": "bar"})
             redirect_url = response["Location"]
-            self.assertTrue(redirect_url.endswith(str(avatar_url(cross_realm_bot)) + "&foo=bar"))
+            self.assertTrue(redirect_url.endswith(str(avatar_url(cross_realm_bot)) + "?foo=bar"))
 
             # Without spectators enabled, no unauthenticated access.
             response = self.client_get("/avatar/cordelia@zulip.com", {"foo": "bar"})