RustPython · youknowone · Apr 22, 2024 · Apr 21, 2024 · Apr 21, 2024 · Apr 22, 2024
diff --git a/Lib/encodings/__init__.py b/Lib/encodings/__init__.py
@@ -156,6 +156,10 @@ def search_function(encoding):
 codecs.register(search_function)
 
 if sys.platform == 'win32':
+    # bpo-671666, bpo-46668: If Python does not implement a codec for current
+    # Windows ANSI code page, use the "mbcs" codec instead:
+    # WideCharToMultiByte() and MultiByteToWideChar() functions with CP_ACP.
+    # Python does not support custom code pages.
     def _alias_mbcs(encoding):
         try:
             import _winapi

diff --git a/Lib/encodings/cp65001.py b/Lib/encodings/cp65001.py
diff --git a/Lib/encodings/idna.py b/Lib/encodings/idna.py
@@ -39,23 +39,21 @@ def nameprep(label):
 
     # Check bidi
     RandAL = [stringprep.in_table_d1(x) for x in label]
-    for c in RandAL:
-        if c:
-            # There is a RandAL char in the string. Must perform further
-            # tests:
-            # 1) The characters in section 5.8 MUST be prohibited.
-            # This is table C.8, which was already checked
-            # 2) If a string contains any RandALCat character, the string
-            # MUST NOT contain any LCat character.
-            if any(stringprep.in_table_d2(x) for x in label):
-                raise UnicodeError("Violation of BIDI requirement 2")
-
-            # 3) If a string contains any RandALCat character, a
-            # RandALCat character MUST be the first character of the
-            # string, and a RandALCat character MUST be the last
-            # character of the string.
-            if not RandAL[0] or not RandAL[-1]:
-                raise UnicodeError("Violation of BIDI requirement 3")
+    if any(RandAL):
+        # There is a RandAL char in the string. Must perform further
+        # tests:
+        # 1) The characters in section 5.8 MUST be prohibited.
+        # This is table C.8, which was already checked
+        # 2) If a string contains any RandALCat character, the string
+        # MUST NOT contain any LCat character.
+        if any(stringprep.in_table_d2(x) for x in label):
+            raise UnicodeError("Violation of BIDI requirement 2")
+        # 3) If a string contains any RandALCat character, a
+        # RandALCat character MUST be the first character of the
+        # string, and a RandALCat character MUST be the last
+        # character of the string.
+        if not RandAL[0] or not RandAL[-1]:
+            raise UnicodeError("Violation of BIDI requirement 3")
 
     return label
 
@@ -103,6 +101,16 @@ def ToASCII(label):
     raise UnicodeError("label empty or too long")
 
 def ToUnicode(label):
+    if len(label) > 1024:
+        # Protection from https://github.com/python/cpython/issues/98433.
+        # https://datatracker.ietf.org/doc/html/rfc5894#section-6
+        # doesn't specify a label size limit prior to NAMEPREP. But having
+        # one makes practical sense.
+        # This leaves ample room for nameprep() to remove Nothing characters
+        # per https://www.rfc-editor.org/rfc/rfc3454#section-3.1 while still
+        # preventing us from wasting time decoding a big thing that'll just
+        # hit the actual <= 63 length limit in Step 6.
+        raise UnicodeError("label way too long")
     # Step 1: Check for ASCII
     if isinstance(label, bytes):
         pure_ascii = True