Fix cosmetic header validity parsing regex (#7308)

Author: nateprewitt

src/requests/_internal_utils.py

@@ -10,10 +10,10 @@
 
 from .compat import builtin_str
 
-_VALID_HEADER_NAME_RE_BYTE = re.compile(rb"^[^:\s][^:\r\n]*$")
-_VALID_HEADER_NAME_RE_STR = re.compile(r"^[^:\s][^:\r\n]*$")
-_VALID_HEADER_VALUE_RE_BYTE = re.compile(rb"^\S[^\r\n]*$|^$")
-_VALID_HEADER_VALUE_RE_STR = re.compile(r"^\S[^\r\n]*$|^$")
+_VALID_HEADER_NAME_RE_BYTE = re.compile(rb"^[^:\s][^:\r\n]*\Z")
+_VALID_HEADER_NAME_RE_STR = re.compile(r"^[^:\s][^:\r\n]*\Z")
+_VALID_HEADER_VALUE_RE_BYTE = re.compile(rb"^\S[^\r\n]*\Z|^\Z")
+_VALID_HEADER_VALUE_RE_STR = re.compile(r"^\S[^\r\n]*\Z|^\Z")
 
 _HEADER_VALIDATORS_STR = (_VALID_HEADER_NAME_RE_STR, _VALID_HEADER_VALUE_RE_STR)
 _HEADER_VALIDATORS_BYTE = (_VALID_HEADER_NAME_RE_BYTE, _VALID_HEADER_VALUE_RE_BYTE)

tests/test_requests.py

@@ -1791,6 +1791,11 @@ def test_header_value_not_str(self, httpbin, invalid_header, key):
             {"fo\r\no": "bar"},
             {"fo\n\ro": "bar"},
             {"fo\no": "bar"},
+            {"foo": "bar\n"},
+            {"foo\n": "bar"},
+            {"foo": "bar\r\n"},
+            {"foo": "\n"},
+            {"foo": "\r\n"},
         ),
     )
     def test_header_no_return_chars(self, httpbin, invalid_header):