Added a work-around for Exchange servers that send broken multipart B…

…ODYSTRUCTURE responses

MailKit/Net/Imap/ImapUtils.cs

@@ -662,15 +662,25 @@ static async Task<object> ParseContentTypeAsync (ImapEngine engine, string forma
 			return contentType;
 		}
 
-		static async Task<ContentDisposition> ParseContentDispositionAsync (ImapEngine engine, string format, bool doAsync, CancellationToken cancellationToken)
+		static async Task<ContentDisposition> ParseContentDispositionAsync (ImapEngine engine, string format, bool isMultipart, bool doAsync, CancellationToken cancellationToken)
 		{
 			var token = await engine.ReadTokenAsync (doAsync, cancellationToken).ConfigureAwait (false);
 
 			if (token.Type == ImapTokenType.Nil)
 				return null;
 
-			if (token.Type != ImapTokenType.OpenParen)
+			if (token.Type != ImapTokenType.OpenParen) {
+				if (isMultipart && token.Type == ImapTokenType.QString) {
+					// Note: This is a work-around for broken Exchange servers.
+					//
+					// See https://stackoverflow.com/questions/33481604/mailkit-fetch-unexpected-token-in-imap-response-qstring-multipart-message
+					// for details.
+					engine.Stream.UngetToken (token);
+					return null;
+				}
+
 				throw ImapEngine.UnexpectedToken (format, token);
+			}
 
 			var dsp = await ReadStringTokenAsync (engine, format, doAsync, cancellationToken).ConfigureAwait (false);
 
@@ -832,7 +842,7 @@ static async Task<BodyPart> ParseMultipartAsync (ImapEngine engine, string forma
 			}
 
 			if (token.Type != ImapTokenType.CloseParen) {
-				body.ContentDisposition = await ParseContentDispositionAsync (engine, format, doAsync, cancellationToken).ConfigureAwait (false);
+				body.ContentDisposition = await ParseContentDispositionAsync (engine, format, true, doAsync, cancellationToken).ConfigureAwait (false);
 				token = await engine.PeekTokenAsync (doAsync, cancellationToken).ConfigureAwait (false);
 			}
 
@@ -938,7 +948,7 @@ public static async Task<BodyPart> ParseBodyAsync (ImapEngine engine, string for
 			}
 
 			if (token.Type != ImapTokenType.CloseParen) {
-				body.ContentDisposition = await ParseContentDispositionAsync (engine, format, doAsync, cancellationToken).ConfigureAwait (false);
+				body.ContentDisposition = await ParseContentDispositionAsync (engine, format, false, doAsync, cancellationToken).ConfigureAwait (false);
 				token = await engine.PeekTokenAsync (doAsync, cancellationToken).ConfigureAwait (false);
 			}
 

UnitTests/Net/Imap/ImapUtilsTests.cs

@@ -426,6 +426,58 @@ public void TestParseMultipartBodyStructureWithNilBodyFldParam ()
 			}
 		}
 
+		[Test]
+		public void TestParseMultipartBodyStructureWithoutBodyFldDsp ()
+		{
+			// Test case from https://stackoverflow.com/questions/33481604/mailkit-fetch-unexpected-token-in-imap-response-qstring-multipart-message
+			const string text = "((\"text\" \"plain\" (\"charset\" \"UTF-8\") NIL \"Message text\" \"Quoted-printable\" 209 6 NIL (\"inline\" NIL) NIL NIL)(\"text\" \"xml\" (\"name\" \"4441004299066.xml\") NIL \"4441004299066.xml\" \"Base64\" 10642 137 NIL (\"inline\" (\"filename\" \"4441004299066.xml\")) NIL NIL)(\"application\" \"pdf\" (\"name\" \"4441004299066.pdf\") NIL \"4441004299066.pdf\" \"Base64\" 48448 NIL (\"inline\" (\"filename\" \"4441004299066.pdf\")) NIL NIL) \"mixed\" (\"boundary\" \"6624CFB2_17170C36_Synapse_boundary\") \"Multipart message\" NIL)\r\n";
+
+			using (var memory = new MemoryStream (Encoding.ASCII.GetBytes (text), false)) {
+				using (var tokenizer = new ImapStream (memory, null, new NullProtocolLogger ())) {
+					using (var engine = new ImapEngine (null)) {
+						BodyPartMultipart multipart;
+						BodyPartBasic basic;
+						BodyPart body;
+
+						engine.SetStream (tokenizer);
+
+						try {
+							body = ImapUtils.ParseBodyAsync (engine, "Unexpected token: {0}", string.Empty, false, CancellationToken.None).GetAwaiter ().GetResult ();
+						} catch (Exception ex) {
+							Assert.Fail ("Parsing BODYSTRUCTURE failed: {0}", ex);
+							return;
+						}
+
+						var token = engine.ReadToken (CancellationToken.None);
+						Assert.AreEqual (ImapTokenType.Eoln, token.Type, "Expected new-line, but got: {0}", token);
+
+						Assert.IsInstanceOf<BodyPartMultipart> (body, "Body types did not match.");
+						multipart = (BodyPartMultipart) body;
+
+						Assert.IsTrue (body.ContentType.IsMimeType ("multipart", "mixed"), "Content-Type did not match.");
+						Assert.AreEqual ("6624CFB2_17170C36_Synapse_boundary", body.ContentType.Parameters ["boundary"], "boundary param did not match");
+						Assert.AreEqual (3, multipart.BodyParts.Count, "BodyParts count does not match.");
+
+						Assert.IsInstanceOf<BodyPartText> (multipart.BodyParts[0], "The type of the first child does not match.");
+						basic = (BodyPartBasic) multipart.BodyParts[0];
+						Assert.AreEqual ("plain", basic.ContentType.MediaSubtype, "Content-Type did not match.");
+						Assert.AreEqual ("Message text", basic.ContentDescription, "Content-Description does not match.");
+
+						Assert.IsInstanceOf<BodyPartText> (multipart.BodyParts[1], "The type of the second child does not match.");
+						basic = (BodyPartBasic) multipart.BodyParts[1];
+						Assert.AreEqual ("xml", basic.ContentType.MediaSubtype, "Content-Type did not match.");
+						Assert.AreEqual ("4441004299066.xml", basic.ContentDescription, "Content-Description does not match.");
+
+						Assert.IsInstanceOf<BodyPartBasic> (multipart.BodyParts[2], "The type of the third child does not match.");
+						basic = (BodyPartBasic) multipart.BodyParts[2];
+						Assert.AreEqual ("application", basic.ContentType.MediaType, "Content-Type did not match.");
+						Assert.AreEqual ("pdf", basic.ContentType.MediaSubtype, "Content-Type did not match.");
+						Assert.AreEqual ("4441004299066.pdf", basic.ContentDescription, "Content-Description does not match.");
+					}
+				}
+			}
+		}
+
 		[Test]
 		public void TestParseExampleThreads ()
 		{