Added detection for IMAP4rev2

Author: jstedfast

MailKit/Net/Imap/ImapCapabilities.cs

@@ -56,7 +56,7 @@ public enum ImapCapabilities : ulong {
 		IMAP4rev1        = 1L << 1,
 
 		/// <summary>
-		/// The server implements the core IMAP4rev2 commands.
+		/// The server implements the core IMAP4rev2 commands described in <a href="https://tools.ietf.org/html/rfc9051">rfc9051</a>.
 		/// </summary>
 		IMAP4rev2        = 1L << 2,
 

MailKit/Net/Imap/ImapEngine.cs

@@ -78,7 +78,8 @@ enum ImapEngineState {
 	enum ImapProtocolVersion {
 		Unknown,
 		IMAP4,
-		IMAP4rev1
+		IMAP4rev1,
+		IMAP4rev2,
 	}
 
 	enum ImapUntaggedResult {
@@ -1330,6 +1331,8 @@ void ProcessCapabilityToken (string atom)
 				Capabilities |= ImapCapabilities.IMAP4;
 			} else if (atom.Equals ("IMAP4REV1", StringComparison.OrdinalIgnoreCase)) {
 				Capabilities |= ImapCapabilities.IMAP4rev1;
+			} else if (atom.Equals ("IMAP4REV2", StringComparison.OrdinalIgnoreCase)) {
+				Capabilities |= ImapCapabilities.IMAP4rev2;
 			} else if (atom.Equals ("STATUS", StringComparison.OrdinalIgnoreCase)) {
 				Capabilities |= ImapCapabilities.Status;
 			} else if (atom.Equals ("ACL", StringComparison.OrdinalIgnoreCase)) {
@@ -1448,7 +1451,19 @@ void ProcessCapabilityToken (string atom)
 
 		void StandardizeCapabilities ()
 		{
-			if ((Capabilities & ImapCapabilities.IMAP4rev1) != 0) {
+			if ((Capabilities & ImapCapabilities.IMAP4rev2) != 0) {
+				ProtocolVersion = ImapProtocolVersion.IMAP4rev2;
+
+				// Rfc9051, Appendix E defines the capabilities that IMAP4rev2 should be assumed to implement:
+				Capabilities |= ImapCapabilities.Status |
+					ImapCapabilities.Namespace | ImapCapabilities.Unselect | ImapCapabilities.UidPlus | ImapCapabilities.ESearch |
+					ImapCapabilities.SearchResults | ImapCapabilities.Enable | ImapCapabilities.Idle | ImapCapabilities.SaslIR | ImapCapabilities.ListExtended |
+					ImapCapabilities.ListStatus | ImapCapabilities.Move | ImapCapabilities.LiteralMinus | ImapCapabilities.SpecialUse;
+
+				// Note: IMAP4rev2 also supports the FETCH portion of the 'BINARY' extension but not the APPEND portion. Since
+				// we currently have no way to distinguish between them using the ImapCapabilities enum, we do not enable the
+				// ImapCapabilities.Binary extension flag.
+			} else if ((Capabilities & ImapCapabilities.IMAP4rev1) != 0) {
 				ProtocolVersion = ImapProtocolVersion.IMAP4rev1;
 				Capabilities |= ImapCapabilities.Status;
 			} else if ((Capabilities & ImapCapabilities.IMAP4) != 0) {

RFCs.md

@@ -117,3 +117,6 @@ The following IETF specifications define the IMAP, POP3 and SMTP protocols:
 * [8514](https://tools.ietf.org/html/rfc8514): Internet Message Access Protocol (IMAP) - SAVEDATE Extension
 * [8689](https://tools.ietf.org/html/rfc8689): SMTP Require TLS Option
 * [8970](https://tools.ietf.org/html/rfc8970): IMAP4 Extension: Message Preview Generation
+* [9051](https://tools.ietf.org/html/rfc9051): Internet Message Access Protocol (IMAP) - Version 4rev2
+* [9208](https://tools.ietf.org/html/rfc9208): IMAP QUOTA Extension (Obsoletes rfc2087)
+* [9394](https://tools.ietf.org/html/rfc9394): IMAP PARTIAL Extension for Paged SEARCH and FETCH

UnitTests/Net/Imap/ImapClientTests.cs

@@ -71,6 +71,10 @@ public class ImapClientTests
 			ImapCapabilities.ESearch | ImapCapabilities.Compress | ImapCapabilities.Enable | ImapCapabilities.ListExtended |
 			ImapCapabilities.ListStatus | ImapCapabilities.Move | ImapCapabilities.UTF8Accept | ImapCapabilities.XList |
 			ImapCapabilities.GMailExt1 | ImapCapabilities.LiteralMinus | ImapCapabilities.AppendLimit;
+		static readonly ImapCapabilities IMAP4rev2CoreCapabilities = ImapCapabilities.IMAP4rev2 | ImapCapabilities.Status |
+			ImapCapabilities.Namespace | ImapCapabilities.Unselect | ImapCapabilities.UidPlus | ImapCapabilities.ESearch |
+			ImapCapabilities.SearchResults | ImapCapabilities.Enable | ImapCapabilities.Idle | ImapCapabilities.SaslIR | ImapCapabilities.ListExtended |
+			ImapCapabilities.ListStatus | ImapCapabilities.Move | ImapCapabilities.LiteralMinus | ImapCapabilities.SpecialUse;
 		static readonly ImapCapabilities AclInitialCapabilities = GMailInitialCapabilities | ImapCapabilities.Acl;
 		static readonly ImapCapabilities AclAuthenticatedCapabilities = GMailAuthenticatedCapabilities | ImapCapabilities.Acl;
 		static readonly ImapCapabilities MetadataInitialCapabilities = GMailInitialCapabilities | ImapCapabilities.Metadata;
@@ -230,6 +234,47 @@ public void TestArgumentExceptions ()
 			}
 		}
 
+		static IList<ImapReplayCommand> CreateIMAP4rev2Commands ()
+		{
+			return new List<ImapReplayCommand> {
+				new ImapReplayCommand ("", Encoding.ASCII.GetBytes ("* OK [CAPABILITY STARTTLS AUTH=SCRAM-SHA-256 LOGINDISABLED IMAP4rev2] IMAP4rev2 Service Ready\r\n")),
+			};
+		}
+
+		[Test]
+		public void TestIMAP4rev2 ()
+		{
+			var commands = CreateIMAP4rev2Commands ();
+
+			using (var client = new ImapClient () { TagPrefix = 'A' }) {
+				try {
+					client.Connect (new ImapReplayStream (commands, false), "localhost", 143, SecureSocketOptions.None);
+				} catch (Exception ex) {
+					Assert.Fail ("Did not expect an exception in Connect: {0}", ex);
+				}
+
+				Assert.AreEqual (IMAP4rev2CoreCapabilities | ImapCapabilities.StartTLS | ImapCapabilities.LoginDisabled, client.Capabilities, "Capabilities");
+				Assert.IsTrue (client.AuthenticationMechanisms.Contains ("SCRAM-SHA-256"), "AUTH=SCRAM-SHA-256");
+			}
+		}
+
+		[Test]
+		public async Task TestIMAP4rev2Async ()
+		{
+			var commands = CreateIMAP4rev2Commands ();
+
+			using (var client = new ImapClient () { TagPrefix = 'A' }) {
+				try {
+					await client.ConnectAsync (new ImapReplayStream (commands, true), "localhost", 143, SecureSocketOptions.None);
+				} catch (Exception ex) {
+					Assert.Fail ("Did not expect an exception in Connect: {0}", ex);
+				}
+
+				Assert.AreEqual (IMAP4rev2CoreCapabilities | ImapCapabilities.StartTLS | ImapCapabilities.LoginDisabled, client.Capabilities, "Capabilities");
+				Assert.IsTrue (client.AuthenticationMechanisms.Contains ("SCRAM-SHA-256"), "AUTH=SCRAM-SHA-256");
+			}
+		}
+
 		[Test]
 		public void TestEscapeUserName ()
 		{