From 5bde2379fcf43a51fab7f3311f008e769a45cef8 Mon Sep 17 00:00:00 2001
From: Bob Mottram <bob@libreserver.org>
Date: Fri, 17 Mar 2023 22:26:12 +0000
Subject: [PATCH] xor sha256 hashes

---
 followerSync.py | 22 ++++++++++++++--------
 tests.py        | 19 +++++++++++++++++++
 2 files changed, 33 insertions(+), 8 deletions(-)

diff --git a/followerSync.py b/followerSync.py
index e6c0aac85..db5a1d582 100644
--- a/followerSync.py
+++ b/followerSync.py
@@ -8,6 +8,7 @@ __status__ = "Production"
 __module_group__ = "ActivityPub"
 
 import os
+import hashlib
 from hashlib import sha256
 from utils import acct_dir
 from utils import get_user_paths
@@ -85,7 +86,7 @@ def _get_followers_sync_json(base_dir: str,
     return sync_json
 
 
-def _get_followers_sync_hash(sync_json: {}) -> str:
+def get_followers_sync_hash(sync_json: {}) -> str:
     """Returns a hash used within the Collection-Synchronization http header
     See https://github.com/mastodon/mastodon/pull/14510
     https://codeberg.org/fediverse/fep/src/branch/main/feps/fep-8fcf.md
@@ -94,14 +95,19 @@ def _get_followers_sync_hash(sync_json: {}) -> str:
         return None
     sync_hash = None
     for actor in sync_json['orderedItems']:
-        actor_hash = sha256(actor.encode('utf-8'))
+        curr_sync_hash = sha256(actor.encode('utf-8'))
+        sync_hash_hex = curr_sync_hash.hexdigest()
+        sync_hash_int = int(sync_hash_hex, 16)
         if sync_hash:
-            sync_hash = sync_hash ^ actor_hash
+            sync_hash = sync_hash ^ sync_hash_int
         else:
-            sync_hash = actor_hash
-    if sync_hash:
-        sync_hash = sync_hash.hexdigest()
-    return sync_hash
+            sync_hash = sync_hash_int
+    if sync_hash is None:
+        return None
+    sync_hash_int = sync_hash
+    sync_hash = hashlib.sha256()
+    sync_hash_bytes = sync_hash_int.to_bytes(32, 'big')
+    return sync_hash_bytes.hex()
 
 
 def update_followers_sync_cache(base_dir: str,
@@ -124,7 +130,7 @@ def update_followers_sync_cache(base_dir: str,
                                      http_prefix,
                                      domain_full,
                                      calling_domain)
-        sync_hash = _get_followers_sync_hash(sync_json)
+        sync_hash = get_followers_sync_hash(sync_json)
         if sync_hash:
             sync_cache[foll_sync_key] = {
                 "hash": sync_hash,
diff --git a/tests.py b/tests.py
index 91fd9e854..c0bd3b133 100644
--- a/tests.py
+++ b/tests.py
@@ -202,6 +202,7 @@ from happening import dav_day_via_server
 from webapp_theme_designer import color_contrast
 from maps import get_map_links_from_post_content
 from maps import geocoords_from_map_link
+from followerSync import get_followers_sync_hash
 
 
 TEST_SERVER_GROUP_RUNNING = False
@@ -7942,6 +7943,23 @@ def _test_convert_markdown() -> None:
     assert message_json['mediaType'] == 'text/html'
 
 
+def _test_xor_hashes():
+    print('xor_hashes')
+    sync_json = {
+        "orderedItems": [
+            'https://somedomain/users/somenick',
+            'https://anotherdomain/users/anothernick'
+        ]
+    }
+    result = get_followers_sync_hash(sync_json)
+    expected = \
+        '316f8dfdf471920a9cdc17da48feead398378e927dee3372d938c524aa7d8917'
+    if result != expected:
+        print('expected: ' + expected)
+        print('result:   ' + result)
+    assert result == expected
+
+
 def run_all_tests():
     base_dir = os.getcwd()
     print('Running tests...')
@@ -7959,6 +7977,7 @@ def run_all_tests():
     _test_checkbox_names()
     _test_thread_functions()
     _test_functions()
+    _test_xor_hashes()
     _test_convert_markdown()
     _test_remove_style()
     _test_html_closing_tag()