Modified ParamaterList.TryParse() to handle quoted rfc2231-encoded pa…

…ram values

Fixes issue #239

MimeKit/ParameterList.cs

@@ -1029,6 +1029,17 @@ internal static bool TryParse (ParserOptions options, byte[] text, ref int index
 					}
 					hex.Reset ();
 				} else if (param.Encoded) {
+					// Note: param value is not supposed to be quoted, but issue #239 illustrates
+					// that this can happen in the wild. Hopefully we will not need to worry
+					// about quoted-pairs.
+					if (length >= 2 && buffer[startIndex] == (byte) '"') {
+						if (buffer[startIndex + length - 1] == (byte) '"')
+							length--;
+
+						startIndex++;
+						length--;
+					}
+
 					value = DecodeRfc2231 (out encoding, ref decoder, hex, buffer, startIndex, length, true);
 					method = ParameterEncodingMethod.Rfc2231;
 					hex.Reset ();

UnitTests/ContentDispositionTests.cs

@@ -148,6 +148,17 @@ public void TestChineseFilename2047 ()
 			Assert.AreEqual ("GB18030", param.Encoding.HeaderName, "The filename encoding did not match.");
 		}
 
+		[Test]
+		public void TestIssue239 ()
+		{
+			const string text = " attachment; size=1049971;\n\tfilename*=\"utf-8''SBD%20%C5%A0kodov%C3%A1k%2Ejpg\"";
+			const string expected = "SBD Škodovák.jpg";
+			ContentDisposition disposition;
+
+			Assert.IsTrue (ContentDisposition.TryParse (text, out disposition), "Failed to parse Content-Disposition");
+			Assert.AreEqual (expected, disposition.FileName, "The filename value does not match.");
+		}
+
 		[Test]
 		public void TestFormData ()
 		{