use labels input for finding error offset, not output result

python · methane · Mar 17, 2024 · Jan 3, 2024 · Jan 3, 2024 · Jan 3, 2024
commit 9f575153c328bb7cf3fd664d095b5b9f5533d5ec
diff --git a/Lib/encodings/idna.py b/Lib/encodings/idna.py
@@ -191,16 +191,15 @@ def encode(self, input, errors='strict'):
        else:
            # ASCII name: fast path
            labels = result.split(b'.')
-            index = 0
-            for label in labels[:-1]:
-                if not (0 < len(label) < 64):
+            for i, label in enumerate(labels[:-1]):
                if len(label) == 0:
-                    raise UnicodeEncodeError("idna", input, index, index+1, "label empty")
-                elif len(label >= 64:
-                    raise UnicodeEncodeError("idna", input, index, index+len(label), "label too long")
-                index += len(label) + 1
-            if len(labels[-1]) >= 64:
-                raise UnicodeEncodeError("idna", input, index, len(input), "label too long")
+                    offset = sum(len(l) for l in labels[:i]) + i
+                    raise UnicodeEncodeError("idna", input, offset, offset+1, "label empty")
+            for i, label in enumerate(labels):
+                if len(label) >= 64:
+                    offset = sum(len(l) for l in labels[:i]) + i
+                    raise UnicodeEncodeError(
+                        "idna", input, offset, offset+len(label), "label too long")
            return result, len(input)

        result = bytearray()
@@ -210,18 +209,19 @@ def encode(self, input, errors='strict'):
            del labels[-1]
        else:
            trailing_dot = b''
-        for label in labels:
+        for i, label in enumerate(labels):
            if result:
                # Join with U+002E
                result.extend(b'.')
            try:
                result.extend(ToASCII(label))
            except UnicodeEncodeError as exc:
+                offset = sum(len(l) for l in labels[:i]) + i
                raise UnicodeEncodeError(
                    "idna",
                    input,
-                    len(result) + exc.start,
-                    len(result) + exc.end,
+                    offset + exc.start,
+                    offset + exc.end,
                    exc.reason,
                )
        return bytes(result+trailing_dot), len(input)
@@ -259,14 +259,9 @@ def decode(self, input, errors='strict'):
            try:
                u_label = ToUnicode(label)
            except UnicodeEncodeError as exc:
-                len_result = sum(len(x) for x in result) + len(result)
+                offset = sum(len(x) for x in result) + len(result)
                raise UnicodeDecodeError(
-                    "idna",
-                    input,
-                    len_result + exc.start,
-                    len_result + exc.end,
-                    exc.reason,
-                )
+                    "idna", input, offset+exc.start, offset+exc.end, exc.reason)
            else:
                result.append(u_label)