From 2c5dc1e308dc951a85134dcfa81f0049554ea91b Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Tue, 27 Feb 2024 11:47:03 +0100
Subject: [PATCH 01/30] deepcopy batched_auth_events

---
 synapse/event_auth.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index d922c8dc35b..76415d74688 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -21,6 +21,7 @@
 #
 
 import collections.abc
+import copy
 import logging
 import typing
 from typing import Any, Dict, Iterable, List, Mapping, Optional, Set, Tuple, Union
@@ -177,7 +178,7 @@ async def check_state_independent_auth_rules(
     # 2. Reject if event has auth_events that: ...
     if batched_auth_events:
         # Copy the batched auth events to avoid mutating them.
-        auth_events = dict(batched_auth_events)
+        auth_events = copy.deepcopy(batched_auth_events)
         needed_auth_event_ids = set(event.auth_event_ids()) - batched_auth_events.keys()
         if needed_auth_event_ids:
             auth_events.update(

From 661134155a70212150a10f8db83d793129151527 Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Tue, 27 Feb 2024 12:02:15 +0100
Subject: [PATCH 02/30] add changelog

---
 changelog.d/16968.bugfix | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 changelog.d/16968.bugfix

diff --git a/changelog.d/16968.bugfix b/changelog.d/16968.bugfix
new file mode 100644
index 00000000000..9cff5f2a3e9
--- /dev/null
+++ b/changelog.d/16968.bugfix
@@ -0,0 +1 @@
+Fix a potential deadlock when checking state independent auth rules by creating a deepcopy of authentication events. Contributed by @ggogel.
\ No newline at end of file

From 0bf1f1fb514260e28afdc0d8d33da962fb44c406 Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Tue, 27 Feb 2024 17:58:29 +0100
Subject: [PATCH 03/30] create copy with make_event_from_dict

---
 synapse/event_auth.py | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index 76415d74688..507839d73e9 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -21,7 +21,6 @@
 #
 
 import collections.abc
-import copy
 import logging
 import typing
 from typing import Any, Dict, Iterable, List, Mapping, Optional, Set, Tuple, Union
@@ -31,6 +30,7 @@
 from signedjson.sign import SignatureVerifyException, verify_signed_json
 from typing_extensions import Protocol
 from unpaddedbase64 import decode_base64
+from synapse.events import make_event_from_dict
 
 from synapse.api.constants import (
     MAX_PDU_SIZE,
@@ -178,7 +178,14 @@ async def check_state_independent_auth_rules(
     # 2. Reject if event has auth_events that: ...
     if batched_auth_events:
         # Copy the batched auth events to avoid mutating them.
-        auth_events = copy.deepcopy(batched_auth_events)
+        auth_events = {}
+        for key, value in batched_auth_events.items():
+            auth_events[key] = make_event_from_dict(
+                event_dict=value.get_dict(),
+                room_version=value.room_version,
+                rejected_reason=value.rejected_reason
+            )
+        
         needed_auth_event_ids = set(event.auth_event_ids()) - batched_auth_events.keys()
         if needed_auth_event_ids:
             auth_events.update(

From 80fc96e001d02cf1514ed88b9621e24d87e247f1 Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Tue, 27 Feb 2024 18:39:22 +0100
Subject: [PATCH 04/30] deepcopy event_dict

---
 synapse/event_auth.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index 507839d73e9..f6657ba3efc 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -21,6 +21,7 @@
 #
 
 import collections.abc
+import copy
 import logging
 import typing
 from typing import Any, Dict, Iterable, List, Mapping, Optional, Set, Tuple, Union
@@ -181,7 +182,7 @@ async def check_state_independent_auth_rules(
         auth_events = {}
         for key, value in batched_auth_events.items():
             auth_events[key] = make_event_from_dict(
-                event_dict=value.get_dict(),
+                event_dict=copy.deepcopy(value.get_dict()),
                 room_version=value.room_version,
                 rejected_reason=value.rejected_reason
             )

From ccf3011f8820a28b348ba5ccb77f6a2ae4f67cf3 Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Tue, 27 Feb 2024 19:54:03 +0100
Subject: [PATCH 05/30] only copy required attributes

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

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index f6657ba3efc..d384f822958 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -182,7 +182,11 @@ async def check_state_independent_auth_rules(
         auth_events = {}
         for key, value in batched_auth_events.items():
             auth_events[key] = make_event_from_dict(
-                event_dict=copy.deepcopy(value.get_dict()),
+                event_dict={
+                    "type": value.get("type"),
+                    "state_key": value.get_state_key(),
+                    "room_id": value.get("room_id")
+                },
                 room_version=value.room_version,
                 rejected_reason=value.rejected_reason
             )

From 1687238494ae82dcf030de573ca06b605ef523cb Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Tue, 27 Feb 2024 23:13:36 +0100
Subject: [PATCH 06/30] remove auth_events copy and update logic

---
 synapse/event_auth.py | 34 ++++++----------------------------
 1 file changed, 6 insertions(+), 28 deletions(-)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index d384f822958..9efa1fa311d 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -177,35 +177,13 @@ async def check_state_independent_auth_rules(
         return
 
     # 2. Reject if event has auth_events that: ...
+    auth_events = await store.get_events(
+        event.auth_event_ids(),
+        redact_behaviour=EventRedactBehaviour.as_is,
+        allow_rejected=True,
+    )
     if batched_auth_events:
-        # Copy the batched auth events to avoid mutating them.
-        auth_events = {}
-        for key, value in batched_auth_events.items():
-            auth_events[key] = make_event_from_dict(
-                event_dict={
-                    "type": value.get("type"),
-                    "state_key": value.get_state_key(),
-                    "room_id": value.get("room_id")
-                },
-                room_version=value.room_version,
-                rejected_reason=value.rejected_reason
-            )
-        
-        needed_auth_event_ids = set(event.auth_event_ids()) - batched_auth_events.keys()
-        if needed_auth_event_ids:
-            auth_events.update(
-                await store.get_events(
-                    needed_auth_event_ids,
-                    redact_behaviour=EventRedactBehaviour.as_is,
-                    allow_rejected=True,
-                )
-            )
-    else:
-        auth_events = await store.get_events(
-            event.auth_event_ids(),
-            redact_behaviour=EventRedactBehaviour.as_is,
-            allow_rejected=True,
-        )
+        auth_events.update(batched_auth_events)
 
     room_id = event.room_id
     auth_dict: MutableStateMap[str] = {}

From af20b240e62acf0af9782a5084ed4240dbad0496 Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Wed, 28 Feb 2024 00:36:42 +0100
Subject: [PATCH 07/30] only update needed auth events

---
 synapse/event_auth.py | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index 9efa1fa311d..d0b4e0d5c62 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -177,13 +177,23 @@ async def check_state_independent_auth_rules(
         return
 
     # 2. Reject if event has auth_events that: ...
-    auth_events = await store.get_events(
-        event.auth_event_ids(),
-        redact_behaviour=EventRedactBehaviour.as_is,
-        allow_rejected=True,
-    )
     if batched_auth_events:
-        auth_events.update(batched_auth_events)
+        auth_events = batched_auth_events
+        needed_auth_event_ids = set(event.auth_event_ids()) - set(batched_auth_events)
+        if needed_auth_event_ids:
+            auth_events.update(
+                await store.get_events(
+                    needed_auth_event_ids,
+                    redact_behaviour=EventRedactBehaviour.as_is,
+                    allow_rejected=True,
+                )
+            )
+    else:
+        auth_events = await store.get_events(
+            event.auth_event_ids(),
+            redact_behaviour=EventRedactBehaviour.as_is,
+            allow_rejected=True
+        )
 
     room_id = event.room_id
     auth_dict: MutableStateMap[str] = {}

From f780f5b6afe1cdb0718c2a11129bc1867d1f0e93 Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Wed, 28 Feb 2024 00:37:19 +0100
Subject: [PATCH 08/30] remove import copy

---
 synapse/event_auth.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index d0b4e0d5c62..fcb2ce53a18 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -21,7 +21,6 @@
 #
 
 import collections.abc
-import copy
 import logging
 import typing
 from typing import Any, Dict, Iterable, List, Mapping, Optional, Set, Tuple, Union

From 711a57d9561ec34c7833740a977eca3f4832a7ce Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Wed, 28 Feb 2024 00:37:46 +0100
Subject: [PATCH 09/30] remove import make_event_from_dict

---
 synapse/event_auth.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index fcb2ce53a18..e9de96e593c 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -30,7 +30,6 @@
 from signedjson.sign import SignatureVerifyException, verify_signed_json
 from typing_extensions import Protocol
 from unpaddedbase64 import decode_base64
-from synapse.events import make_event_from_dict
 
 from synapse.api.constants import (
     MAX_PDU_SIZE,

From a3bfc23cb21511db68c1b0cb6844f47e512579e7 Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Wed, 28 Feb 2024 00:39:34 +0100
Subject: [PATCH 10/30] update changelog

---
 changelog.d/16968.bugfix | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/changelog.d/16968.bugfix b/changelog.d/16968.bugfix
index 9cff5f2a3e9..75a982f23a9 100644
--- a/changelog.d/16968.bugfix
+++ b/changelog.d/16968.bugfix
@@ -1 +1 @@
-Fix a potential deadlock when checking state independent auth rules by creating a deepcopy of authentication events. Contributed by @ggogel.
\ No newline at end of file
+Do not create a shallow copy of batched_auth_events to prevent a potential deadlock. Contributed by @ggogel.
\ No newline at end of file

From 0263502c4390674737505fd85a920761e0028dd6 Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Wed, 28 Feb 2024 09:31:10 +0100
Subject: [PATCH 11/30] Revert "only update needed auth events"

This reverts commit 59e3c1b4ac507d9a218578e84e06e78d4686f850.
---
 synapse/event_auth.py | 22 ++++++----------------
 1 file changed, 6 insertions(+), 16 deletions(-)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index e9de96e593c..f26a6e7c6cc 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -175,23 +175,13 @@ async def check_state_independent_auth_rules(
         return
 
     # 2. Reject if event has auth_events that: ...
+    auth_events = await store.get_events(
+        event.auth_event_ids(),
+        redact_behaviour=EventRedactBehaviour.as_is,
+        allow_rejected=True,
+    )
     if batched_auth_events:
-        auth_events = batched_auth_events
-        needed_auth_event_ids = set(event.auth_event_ids()) - set(batched_auth_events)
-        if needed_auth_event_ids:
-            auth_events.update(
-                await store.get_events(
-                    needed_auth_event_ids,
-                    redact_behaviour=EventRedactBehaviour.as_is,
-                    allow_rejected=True,
-                )
-            )
-    else:
-        auth_events = await store.get_events(
-            event.auth_event_ids(),
-            redact_behaviour=EventRedactBehaviour.as_is,
-            allow_rejected=True
-        )
+        auth_events.update(batched_auth_events)
 
     room_id = event.room_id
     auth_dict: MutableStateMap[str] = {}

From 05a00b2de6907c41c9b8f859e3dff58e0c482706 Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Wed, 28 Feb 2024 12:40:21 +0100
Subject: [PATCH 12/30] Revert "Revert "only update needed auth events""

This reverts commit c7ea377919f9a39cc1ef746fa8c8790a8a7b3209.
---
 synapse/event_auth.py | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index f26a6e7c6cc..e9de96e593c 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -175,13 +175,23 @@ async def check_state_independent_auth_rules(
         return
 
     # 2. Reject if event has auth_events that: ...
-    auth_events = await store.get_events(
-        event.auth_event_ids(),
-        redact_behaviour=EventRedactBehaviour.as_is,
-        allow_rejected=True,
-    )
     if batched_auth_events:
-        auth_events.update(batched_auth_events)
+        auth_events = batched_auth_events
+        needed_auth_event_ids = set(event.auth_event_ids()) - set(batched_auth_events)
+        if needed_auth_event_ids:
+            auth_events.update(
+                await store.get_events(
+                    needed_auth_event_ids,
+                    redact_behaviour=EventRedactBehaviour.as_is,
+                    allow_rejected=True,
+                )
+            )
+    else:
+        auth_events = await store.get_events(
+            event.auth_event_ids(),
+            redact_behaviour=EventRedactBehaviour.as_is,
+            allow_rejected=True
+        )
 
     room_id = event.room_id
     auth_dict: MutableStateMap[str] = {}

From 7d1f98cb303b11c02365b03e9a6f0f21fedd210a Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Wed, 28 Feb 2024 12:47:12 +0100
Subject: [PATCH 13/30] do not nest store.get_events in update

---
 synapse/event_auth.py | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index e9de96e593c..7fa84f8c16c 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -179,13 +179,12 @@ async def check_state_independent_auth_rules(
         auth_events = batched_auth_events
         needed_auth_event_ids = set(event.auth_event_ids()) - set(batched_auth_events)
         if needed_auth_event_ids:
-            auth_events.update(
-                await store.get_events(
-                    needed_auth_event_ids,
-                    redact_behaviour=EventRedactBehaviour.as_is,
-                    allow_rejected=True,
-                )
+            needed_auth_events = await store.get_events(
+                needed_auth_event_ids,
+                redact_behaviour=EventRedactBehaviour.as_is,
+                allow_rejected=True
             )
+            auth_events.update(needed_auth_events)
     else:
         auth_events = await store.get_events(
             event.auth_event_ids(),

From e1cc6846bbe358323752f02ad8e5be835c2b9c4a Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Wed, 28 Feb 2024 13:51:36 +0100
Subject: [PATCH 14/30] use a list comprehension instead of set operation

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

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index 7fa84f8c16c..f7682c5322c 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -177,7 +177,7 @@ async def check_state_independent_auth_rules(
     # 2. Reject if event has auth_events that: ...
     if batched_auth_events:
         auth_events = batched_auth_events
-        needed_auth_event_ids = set(event.auth_event_ids()) - set(batched_auth_events)
+        needed_auth_event_ids = [event_id for event_id in event.auth_event_ids() if event_id not in batched_auth_events]
         if needed_auth_event_ids:
             needed_auth_events = await store.get_events(
                 needed_auth_event_ids,

From e63563703506478f518037120141ffcff19aaa75 Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Mon, 4 Mar 2024 21:15:03 +0100
Subject: [PATCH 15/30] linting

---
 synapse/event_auth.py | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index f7682c5322c..234d9753101 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -177,19 +177,23 @@ async def check_state_independent_auth_rules(
     # 2. Reject if event has auth_events that: ...
     if batched_auth_events:
         auth_events = batched_auth_events
-        needed_auth_event_ids = [event_id for event_id in event.auth_event_ids() if event_id not in batched_auth_events]
+        needed_auth_event_ids = [
+            event_id
+            for event_id in event.auth_event_ids()
+            if event_id not in batched_auth_events
+        ]
         if needed_auth_event_ids:
             needed_auth_events = await store.get_events(
                 needed_auth_event_ids,
                 redact_behaviour=EventRedactBehaviour.as_is,
-                allow_rejected=True
+                allow_rejected=True,
             )
             auth_events.update(needed_auth_events)
     else:
         auth_events = await store.get_events(
             event.auth_event_ids(),
             redact_behaviour=EventRedactBehaviour.as_is,
-            allow_rejected=True
+            allow_rejected=True,
         )
 
     room_id = event.room_id

From e65cabd82a57b6821997515f0ad95d684c4787ca Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Mon, 4 Mar 2024 21:57:31 +0100
Subject: [PATCH 16/30] type auth_events

---
 synapse/event_auth.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index 234d9753101..40e508f5b4a 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -23,7 +23,7 @@
 import collections.abc
 import logging
 import typing
-from typing import Any, Dict, Iterable, List, Mapping, Optional, Set, Tuple, Union
+from typing import Any, Dict, Iterable, List, Mapping, MutableMapping, Optional, Set, Tuple, Union
 
 from canonicaljson import encode_canonical_json
 from signedjson.key import decode_verify_key_bytes
@@ -175,6 +175,7 @@ async def check_state_independent_auth_rules(
         return
 
     # 2. Reject if event has auth_events that: ...
+    auth_events: MutableMapping[str, "EventBase"]
     if batched_auth_events:
         auth_events = batched_auth_events
         needed_auth_event_ids = [

From a4534ed06552ae9ce1f5dae025105dd612b49eea Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Tue, 5 Mar 2024 13:40:11 +0100
Subject: [PATCH 17/30] dict batched_auth_events

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

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index 40e508f5b4a..52a78f51aa9 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -177,7 +177,7 @@ async def check_state_independent_auth_rules(
     # 2. Reject if event has auth_events that: ...
     auth_events: MutableMapping[str, "EventBase"]
     if batched_auth_events:
-        auth_events = batched_auth_events
+        auth_events = dict(batched_auth_events)
         needed_auth_event_ids = [
             event_id
             for event_id in event.auth_event_ids()

From 8197f84e79964f4ea0d30d48d1144fff07c8ec43 Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Tue, 5 Mar 2024 13:55:38 +0100
Subject: [PATCH 18/30] isort lint

---
 synapse/event_auth.py | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index 52a78f51aa9..45aee341a04 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -23,7 +23,18 @@
 import collections.abc
 import logging
 import typing
-from typing import Any, Dict, Iterable, List, Mapping, MutableMapping, Optional, Set, Tuple, Union
+from typing import (
+    Any,
+    Dict,
+    Iterable,
+    List,
+    Mapping,
+    MutableMapping,
+    Optional,
+    Set,
+    Tuple,
+    Union,
+)
 
 from canonicaljson import encode_canonical_json
 from signedjson.key import decode_verify_key_bytes

From e199b27fcdef6461ad335cfccb30b0814c325713 Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Tue, 5 Mar 2024 14:11:33 +0100
Subject: [PATCH 19/30] update changelog

---
 changelog.d/16968.bugfix | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/changelog.d/16968.bugfix b/changelog.d/16968.bugfix
index 75a982f23a9..57ed851178f 100644
--- a/changelog.d/16968.bugfix
+++ b/changelog.d/16968.bugfix
@@ -1 +1 @@
-Do not create a shallow copy of batched_auth_events to prevent a potential deadlock. Contributed by @ggogel.
\ No newline at end of file
+Prevent locking up when checking auth rules that are independent of room state for batched auth events. Contributed by @ggogel.
\ No newline at end of file

From deba2ceb5aadca903756eaea57e7383633d0de4c Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Fri, 8 Mar 2024 00:45:30 +0100
Subject: [PATCH 20/30] Revert "dict batched_auth_events"

This reverts commit dfac2cab3f425b99d5c17cb9cc6e20915e751e99.
---
 synapse/event_auth.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index 45aee341a04..b1e78686958 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -188,7 +188,7 @@ async def check_state_independent_auth_rules(
     # 2. Reject if event has auth_events that: ...
     auth_events: MutableMapping[str, "EventBase"]
     if batched_auth_events:
-        auth_events = dict(batched_auth_events)
+        auth_events = batched_auth_events
         needed_auth_event_ids = [
             event_id
             for event_id in event.auth_event_ids()

From a3fa5535f5a0873067bd34aa116a3690f3a1e513 Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Fri, 8 Mar 2024 01:44:34 +0100
Subject: [PATCH 21/30] use update

---
 synapse/event_auth.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index b1e78686958..d151024c172 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -186,9 +186,8 @@ async def check_state_independent_auth_rules(
         return
 
     # 2. Reject if event has auth_events that: ...
-    auth_events: MutableMapping[str, "EventBase"]
+    auth_events: MutableMapping[str, "EventBase"] = {}
     if batched_auth_events:
-        auth_events = batched_auth_events
         needed_auth_event_ids = [
             event_id
             for event_id in event.auth_event_ids()
@@ -201,6 +200,7 @@ async def check_state_independent_auth_rules(
                 allow_rejected=True,
             )
             auth_events.update(needed_auth_events)
+        auth_events.update(batched_auth_events)
     else:
         auth_events = await store.get_events(
             event.auth_event_ids(),

From 3826b99bbf507c9561a99693f3c8134494f58a82 Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Fri, 8 Mar 2024 12:59:58 +0100
Subject: [PATCH 22/30] Revert "use update"

This reverts commit 22df933f38c21166bf652d6cbaebfcbe00d22fa2.
---
 synapse/event_auth.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index d151024c172..b1e78686958 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -186,8 +186,9 @@ async def check_state_independent_auth_rules(
         return
 
     # 2. Reject if event has auth_events that: ...
-    auth_events: MutableMapping[str, "EventBase"] = {}
+    auth_events: MutableMapping[str, "EventBase"]
     if batched_auth_events:
+        auth_events = batched_auth_events
         needed_auth_event_ids = [
             event_id
             for event_id in event.auth_event_ids()
@@ -200,7 +201,6 @@ async def check_state_independent_auth_rules(
                 allow_rejected=True,
             )
             auth_events.update(needed_auth_events)
-        auth_events.update(batched_auth_events)
     else:
         auth_events = await store.get_events(
             event.auth_event_ids(),

From 31bf88b80a25b96eec1845090eeb00cb1fabcbdb Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Fri, 8 Mar 2024 15:24:10 +0100
Subject: [PATCH 23/30] add items individually

---
 synapse/event_auth.py | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index b1e78686958..030a746df22 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -186,14 +186,18 @@ async def check_state_independent_auth_rules(
         return
 
     # 2. Reject if event has auth_events that: ...
-    auth_events: MutableMapping[str, "EventBase"]
+    auth_events: MutableMapping[str, "EventBase"] = {}
     if batched_auth_events:
-        auth_events = batched_auth_events
+        # Add items individually to prevent locking the whole mapping
+        for key, value in batched_auth_events.items():
+            auth_events[key] = value
+        
         needed_auth_event_ids = [
             event_id
             for event_id in event.auth_event_ids()
             if event_id not in batched_auth_events
         ]
+
         if needed_auth_event_ids:
             needed_auth_events = await store.get_events(
                 needed_auth_event_ids,

From eee0a2b1883cf706369b101744b03b4517515be1 Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Fri, 8 Mar 2024 21:56:14 +0100
Subject: [PATCH 24/30] use unpacking operator

---
 synapse/event_auth.py | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index 030a746df22..30d0a2ae3d2 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -186,25 +186,23 @@ async def check_state_independent_auth_rules(
         return
 
     # 2. Reject if event has auth_events that: ...
-    auth_events: MutableMapping[str, "EventBase"] = {}
     if batched_auth_events:
-        # Add items individually to prevent locking the whole mapping
-        for key, value in batched_auth_events.items():
-            auth_events[key] = value
-        
         needed_auth_event_ids = [
             event_id
             for event_id in event.auth_event_ids()
             if event_id not in batched_auth_events
         ]
 
+        needed_auth_events: MutableMapping[str, "EventBase"] = {}
+
         if needed_auth_event_ids:
             needed_auth_events = await store.get_events(
                 needed_auth_event_ids,
                 redact_behaviour=EventRedactBehaviour.as_is,
                 allow_rejected=True,
             )
-            auth_events.update(needed_auth_events)
+        
+        auth_events: Mapping[str, "EventBase"] = {**batched_auth_events, **needed_auth_events} 
     else:
         auth_events = await store.get_events(
             event.auth_event_ids(),

From d13f298099332078b8ec70c221ff1220ea037808 Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Sat, 9 Mar 2024 00:17:29 +0100
Subject: [PATCH 25/30] use cast

---
 synapse/event_auth.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index 30d0a2ae3d2..9e7d06c54f5 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -34,6 +34,7 @@
     Set,
     Tuple,
     Union,
+    cast,
 )
 
 from canonicaljson import encode_canonical_json
@@ -186,6 +187,7 @@ async def check_state_independent_auth_rules(
         return
 
     # 2. Reject if event has auth_events that: ...
+    auth_events: MutableMapping[str, "EventBase"] = {}
     if batched_auth_events:
         needed_auth_event_ids = [
             event_id
@@ -202,7 +204,8 @@ async def check_state_independent_auth_rules(
                 allow_rejected=True,
             )
         
-        auth_events: Mapping[str, "EventBase"] = {**batched_auth_events, **needed_auth_events} 
+        auth_events = cast(MutableMapping[str, "EventBase"], batched_auth_events)
+        auth_events.update(needed_auth_events)
     else:
         auth_events = await store.get_events(
             event.auth_event_ids(),

From 5bd7d937301dc6b20ff6054e17edaf08cd62dbb8 Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Sat, 9 Mar 2024 08:04:15 +0100
Subject: [PATCH 26/30] update only if needed auth events exist

---
 synapse/event_auth.py | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index 9e7d06c54f5..8545b3f909c 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -189,23 +189,20 @@ async def check_state_independent_auth_rules(
     # 2. Reject if event has auth_events that: ...
     auth_events: MutableMapping[str, "EventBase"] = {}
     if batched_auth_events:
+        auth_events = cast(MutableMapping[str, "EventBase"], batched_auth_events)
         needed_auth_event_ids = [
             event_id
             for event_id in event.auth_event_ids()
             if event_id not in batched_auth_events
         ]
-
-        needed_auth_events: MutableMapping[str, "EventBase"] = {}
-
         if needed_auth_event_ids:
-            needed_auth_events = await store.get_events(
-                needed_auth_event_ids,
-                redact_behaviour=EventRedactBehaviour.as_is,
-                allow_rejected=True,
+            auth_events.update(
+                await store.get_events(
+                    needed_auth_event_ids,
+                    redact_behaviour=EventRedactBehaviour.as_is,
+                    allow_rejected=True,
+                )
             )
-        
-        auth_events = cast(MutableMapping[str, "EventBase"], batched_auth_events)
-        auth_events.update(needed_auth_events)
     else:
         auth_events = await store.get_events(
             event.auth_event_ids(),

From 7ccf264791e7bcf98a01622baf8525f8fa40bb6f Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Mon, 11 Mar 2024 11:41:05 +0100
Subject: [PATCH 27/30] use ChainMap

---
 synapse/event_auth.py | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index 8545b3f909c..52440cb75cb 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -35,6 +35,7 @@
     Tuple,
     Union,
     cast,
+    ChainMap,
 )
 
 from canonicaljson import encode_canonical_json
@@ -187,16 +188,16 @@ async def check_state_independent_auth_rules(
         return
 
     # 2. Reject if event has auth_events that: ...
-    auth_events: MutableMapping[str, "EventBase"] = {}
+    auth_events: ChainMap[str, EventBase] = ChainMap()
     if batched_auth_events:
-        auth_events = cast(MutableMapping[str, "EventBase"], batched_auth_events)
+        auth_events = auth_events.new_child(cast(MutableMapping[str, "EventBase"], batched_auth_events))
         needed_auth_event_ids = [
             event_id
             for event_id in event.auth_event_ids()
             if event_id not in batched_auth_events
         ]
         if needed_auth_event_ids:
-            auth_events.update(
+            auth_events = auth_events.new_child(
                 await store.get_events(
                     needed_auth_event_ids,
                     redact_behaviour=EventRedactBehaviour.as_is,
@@ -204,10 +205,12 @@ async def check_state_independent_auth_rules(
                 )
             )
     else:
-        auth_events = await store.get_events(
-            event.auth_event_ids(),
-            redact_behaviour=EventRedactBehaviour.as_is,
-            allow_rejected=True,
+        auth_events = auth_events.new_child(
+            await store.get_events(
+                event.auth_event_ids(),
+                redact_behaviour=EventRedactBehaviour.as_is,
+                allow_rejected=True,
+            )
         )
 
     room_id = event.room_id

From 1fc776caaa9349f35c34788c66c5bac6882153af Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Mon, 11 Mar 2024 11:42:09 +0100
Subject: [PATCH 28/30] fix isort

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

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index 52440cb75cb..058f62256b1 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -25,6 +25,7 @@
 import typing
 from typing import (
     Any,
+    ChainMap,
     Dict,
     Iterable,
     List,
@@ -35,7 +36,6 @@
     Tuple,
     Union,
     cast,
-    ChainMap,
 )
 
 from canonicaljson import encode_canonical_json

From b6bba1049d1bcfe0cf92458140834b88a620e4e9 Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Mon, 11 Mar 2024 11:50:47 +0100
Subject: [PATCH 29/30] add comments

---
 synapse/event_auth.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index 058f62256b1..25e92c86cc6 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -190,6 +190,10 @@ async def check_state_independent_auth_rules(
     # 2. Reject if event has auth_events that: ...
     auth_events: ChainMap[str, EventBase] = ChainMap()
     if batched_auth_events:
+        # batched_auth_events can become very large. To avoid repeatedly copying it, which
+        # would significantly impact performance, we use a ChainMap.
+        # batched_auth_events must be cast to MutableMapping because .new_child() requires
+        # this type. This casting is safe as the mapping is never mutated.
         auth_events = auth_events.new_child(cast(MutableMapping[str, "EventBase"], batched_auth_events))
         needed_auth_event_ids = [
             event_id

From 5fd55d17f65f0769623eab5b88d5c630ed4fbf28 Mon Sep 17 00:00:00 2001
From: Gerrit Gogel <gerrit@gogel.me>
Date: Mon, 11 Mar 2024 12:46:53 +0100
Subject: [PATCH 30/30] linting

---
 synapse/event_auth.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index 25e92c86cc6..c8b06f760eb 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -194,7 +194,9 @@ async def check_state_independent_auth_rules(
         # would significantly impact performance, we use a ChainMap.
         # batched_auth_events must be cast to MutableMapping because .new_child() requires
         # this type. This casting is safe as the mapping is never mutated.
-        auth_events = auth_events.new_child(cast(MutableMapping[str, "EventBase"], batched_auth_events))
+        auth_events = auth_events.new_child(
+            cast(MutableMapping[str, "EventBase"], batched_auth_events)
+        )
         needed_auth_event_ids = [
             event_id
             for event_id in event.auth_event_ids()