[strongSwan-dev] [PATCH v2] IKEv1 fragmentation support for Windows peers

[Volker Rümelin]

Hi,

this is a new version of IKEv1 fragmentation support for Windows
peers. The patch applies on top of the ikev2-fragmentation branch.

I still think ipsec/l2tp with fragmentation support is a useful
fallback option in case the Windows IKEv2 connection fails because
of fragmentation problems.

Tested with Windows XP, 7 and 8.1.

diff --git a/src/libcharon/sa/ike_sa.c b/src/libcharon/sa/ike_sa.c
index 8b659c0..f2e6579 100644
--- a/src/libcharon/sa/ike_sa.c
+++ b/src/libcharon/sa/ike_sa.c
@@ -16,6 +16,28 @@
  * for more details.
  */
 
+/*
+ * Copyright (c) 2014 Volker Rümelin
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
 #include <string.h>
 #include <sys/stat.h>
 #include <errno.h>
@@ -1024,6 +1046,14 @@ METHOD(ike_sa_t, generate_message_fragmented, status_t,
 				break;
 			case FRAGMENTATION_YES:
 				use_frags = supports_extension(this, EXT_IKE_FRAGMENTATION);
+				if (use_frags && this->version == IKEV1 &&
+					supports_extension(this, EXT_MS_NT5_ISAKMPOAKLEY))
+				{
+					/* It seems Windows 7 and 8 peers only accept proprietary
+					 * fragmented messages if they expect certificates. */
+					use_frags = message->get_payload(message,
+													 PLV1_CERTIFICATE) != NULL;
+				}
 				break;
 			default:
 				break;
diff --git a/src/libcharon/sa/ike_sa.h b/src/libcharon/sa/ike_sa.h
index f04fab0..e71e72d 100644
--- a/src/libcharon/sa/ike_sa.h
+++ b/src/libcharon/sa/ike_sa.h
@@ -131,6 +131,11 @@ enum ike_extension_t {
 	 * peer supports proprietary IKEv1 or standardized IKEv2 fragmentation
 	 */
 	EXT_IKE_FRAGMENTATION = (1<<11),
+
+	/**
+	 * peer is a Windows client
+	 */
+	EXT_MS_NT5_ISAKMPOAKLEY = (1<<12),
 };
 
 /**
diff --git a/src/libcharon/sa/ikev1/tasks/isakmp_vendor.c b/src/libcharon/sa/ikev1/tasks/isakmp_vendor.c
index 426c4bd..e33ef2d 100644
--- a/src/libcharon/sa/ikev1/tasks/isakmp_vendor.c
+++ b/src/libcharon/sa/ikev1/tasks/isakmp_vendor.c
@@ -15,7 +15,7 @@
  */
 
 /*
- * Copyright (C) 2012 Volker Rümelin
+ * Copyright (C) 2012-2014 Volker Rümelin
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -106,10 +106,15 @@ static struct {
 	  "\x12\xf5\xf2\x8c\x45\x71\x68\xa9\x70\x2d\x9f\xe2\x74\xcc\x01\x00"},
 
 	/* Proprietary IKE fragmentation extension. Capabilities are handled
-	 * specially on receipt of this VID. */
+	 * specially on receipt of this VID. Windows peers send this VID
+	 * without capabilities, but accept it with and without capabilities. */
 	{ "FRAGMENTATION", EXT_IKE_FRAGMENTATION, FALSE, 20,
 	  "\x40\x48\xb7\xd5\x6e\xbc\xe8\x85\x25\xe7\xde\x7f\x00\xd6\xc2\xd3\x80\x00\x00\x00"},
 
+	/* Windows peers send this VID and a version number */
+	{ "MS NT5 ISAKMPOAKLEY", EXT_MS_NT5_ISAKMPOAKLEY, FALSE, 20,
+	  "\x1e\x2b\x51\x69\x05\x99\x1c\x7d\x7c\x96\xfc\xbf\xb5\x87\xe4\x61\x00\x00\x00\x00"},
+
 }, vendor_natt_ids[] = {
 
 	/* NAT-Traversal VIDs ordered by preference */
@@ -167,15 +172,27 @@ static struct {
  */
 static const u_int32_t fragmentation_ike = 0x80000000;
 
-/**
- * Check if the given vendor ID indicate support for fragmentation
- */
-static bool fragmentation_supported(chunk_t data, int i)
+static bool is_known_vid(chunk_t data, int i)
 {
-	if (vendor_ids[i].extension  == EXT_IKE_FRAGMENTATION &&
-		data.len == 20 && memeq(data.ptr, vendor_ids[i].id, 16))
+	switch (vendor_ids[i].extension)
 	{
-		return untoh32(&data.ptr[16]) & fragmentation_ike;
+		case EXT_IKE_FRAGMENTATION:
+			if (data.len >= 16 && memeq(data.ptr, vendor_ids[i].id, 16))
+			{
+				switch (data.len)
+				{
+					case 16:
+						return TRUE;
+					case 20:
+						return untoh32(&data.ptr[16]) & fragmentation_ike;
+				}
+			}
+			break;
+		case EXT_MS_NT5_ISAKMPOAKLEY:
+			return data.len == 20 && memeq(data.ptr, vendor_ids[i].id, 16);
+		default:
+			return chunk_equals(data, chunk_create(vendor_ids[i].id,
+												   vendor_ids[i].len));
 	}
 	return FALSE;
 }
@@ -251,9 +268,7 @@ static void process(private_isakmp_vendor_t *this, message_t *message)
 
 			for (i = 0; i < countof(vendor_ids); i++)
 			{
-				if (chunk_equals(data, chunk_create(vendor_ids[i].id,
-													vendor_ids[i].len)) ||
-					fragmentation_supported(data, i))
+				if (is_known_vid(data, i))
 				{
 					DBG1(DBG_IKE, "received %s vendor ID", vendor_ids[i].desc);
 					if (vendor_ids[i].extension)
-- 
1.8.4.5