Harden header name normalization strip/lower boundaries

Co-authored-by: Shri Sukhani <shrisukhani@users.noreply.github.com>

Author: cursoragent

hyperbrowser/header_utils.py

@@ -51,7 +51,17 @@ def normalize_headers(
     ):
         if not isinstance(key, str) or not isinstance(value, str):
             raise HyperbrowserError(effective_pair_error_message)
-        normalized_key = key.strip()
+        try:
+            normalized_key = key.strip()
+            if not isinstance(normalized_key, str):
+                raise TypeError("normalized header name must be a string")
+        except HyperbrowserError:
+            raise
+        except Exception as exc:
+            raise HyperbrowserError(
+                "Failed to normalize header name",
+                original_error=exc,
+            ) from exc
         if not normalized_key:
             raise HyperbrowserError("header names must not be empty")
         if len(normalized_key) > _MAX_HEADER_NAME_LENGTH:
@@ -74,7 +84,17 @@ def normalize_headers(
             for character in f"{normalized_key}{value}"
         ):
             raise HyperbrowserError("headers must not contain control characters")
-        canonical_header_name = normalized_key.lower()
+        try:
+            canonical_header_name = normalized_key.lower()
+            if not isinstance(canonical_header_name, str):
+                raise TypeError("canonical header name must be a string")
+        except HyperbrowserError:
+            raise
+        except Exception as exc:
+            raise HyperbrowserError(
+                "Failed to normalize header name",
+                original_error=exc,
+            ) from exc
         if canonical_header_name in seen_header_names:
             raise HyperbrowserError(
                 "duplicate header names are not allowed after normalization"

tests/test_header_utils.py

@@ -36,6 +36,30 @@ def items(self):
         return [self._broken_item]
 
 
+class _BrokenStripHeaderName(str):
+    def strip(self, chars=None):  # type: ignore[override]
+        _ = chars
+        raise RuntimeError("header strip exploded")
+
+
+class _BrokenLowerHeaderName(str):
+    def strip(self, chars=None):  # type: ignore[override]
+        _ = chars
+        return self
+
+    def lower(self):  # type: ignore[override]
+        raise RuntimeError("header lower exploded")
+
+
+class _NonStringLowerHeaderName(str):
+    def strip(self, chars=None):  # type: ignore[override]
+        _ = chars
+        return self
+
+    def lower(self):  # type: ignore[override]
+        return object()
+
+
 def test_normalize_headers_trims_header_names():
     headers = normalize_headers(
         {"  X-Correlation-Id  ": "abc123"},
@@ -53,6 +77,57 @@ def test_normalize_headers_rejects_empty_header_name():
         )
 
 
+def test_normalize_headers_wraps_header_name_strip_failures():
+    with pytest.raises(
+        HyperbrowserError, match="Failed to normalize header name"
+    ) as exc_info:
+        normalize_headers(
+            {_BrokenStripHeaderName("X-Trace-Id"): "trace-1"},
+            mapping_error_message="headers must be a mapping of string pairs",
+        )
+
+    assert exc_info.value.original_error is not None
+
+
+def test_normalize_headers_preserves_hyperbrowser_header_name_strip_failures():
+    class _BrokenStripHeaderName(str):
+        def strip(self, chars=None):  # type: ignore[override]
+            _ = chars
+            raise HyperbrowserError("custom strip failure")
+
+    with pytest.raises(HyperbrowserError, match="custom strip failure") as exc_info:
+        normalize_headers(
+            {_BrokenStripHeaderName("X-Trace-Id"): "trace-1"},
+            mapping_error_message="headers must be a mapping of string pairs",
+        )
+
+    assert exc_info.value.original_error is None
+
+
+def test_normalize_headers_wraps_header_name_lower_failures():
+    with pytest.raises(
+        HyperbrowserError, match="Failed to normalize header name"
+    ) as exc_info:
+        normalize_headers(
+            {_BrokenLowerHeaderName("X-Trace-Id"): "trace-1"},
+            mapping_error_message="headers must be a mapping of string pairs",
+        )
+
+    assert exc_info.value.original_error is not None
+
+
+def test_normalize_headers_wraps_non_string_header_name_lower_results():
+    with pytest.raises(
+        HyperbrowserError, match="Failed to normalize header name"
+    ) as exc_info:
+        normalize_headers(
+            {_NonStringLowerHeaderName("X-Trace-Id"): "trace-1"},
+            mapping_error_message="headers must be a mapping of string pairs",
+        )
+
+    assert exc_info.value.original_error is not None
+
+
 def test_normalize_headers_rejects_overly_long_header_names():
     long_header_name = "X-" + ("a" * 255)
     with pytest.raises(