Strip whitespace around part header values in FormParser

python_multipart/multipart.py

@@ -1828,7 +1828,7 @@ def on_header_value(data: bytes, start: int, end: int) -> None:
                 header_value.append(data[start:end])
 
             def on_header_end() -> None:
-                headers[b"".join(header_name).lower()] = b"".join(header_value)
+                headers[b"".join(header_name).lower()] = b"".join(header_value).strip(b" \t")
                 del header_name[:]
                 del header_value[:]
 

tests/test_data/http/base64_encoding_whitespace.http

@@ -0,0 +1,11 @@
+----boundary
+Content-Disposition: form-data; name="a"
+Content-Transfer-Encoding: base64 
+
+aGVsbG8=
+----boundary
+Content-Disposition: form-data; name="b"
+Content-Transfer-Encoding:	base64	
+
+aGVsbG8=
+----boundary--

tests/test_data/http/base64_encoding_whitespace.yaml

@@ -0,0 +1,8 @@
+boundary: --boundary
+expected:
+  - name: a
+    type: field
+    data: !!binary "aGVsbG8="
+  - name: b
+    type: field
+    data: !!binary "aGVsbG8="