unknown-payload: Use a new private payload type and make original type available

This fixes a DoS and potential remote code execution vulnerability that was
caused because the original payload type that was returned previously was
used to cast such payload objects to payloads of the indicated type (e.g.
when logging notify payloads with a payload type for the wrong IKE version).

Fixes CVE-2015-3991.

src/libcharon/encoding/message.c

@@ -2513,7 +2513,7 @@ static status_t decrypt_payloads(private_message_t *this, keymat_t *keymat)
 			was_encrypted = "encrypted fragment payload";
 		}
 
-		if (payload_is_known(type, this->major_version) && !was_encrypted &&
+		if (type != PL_UNKNOWN && !was_encrypted &&
 			!is_connectivity_check(this, payload) &&
 			this->exchange_type != AGGRESSIVE)
 		{

src/libcharon/encoding/payloads/payload.c

@@ -97,6 +97,7 @@ ENUM_NEXT(payload_type_names, PLV1_NAT_D_DRAFT_00_03, PLV1_FRAGMENT, PLV2_FRAGME
 #endif /* ME */
 ENUM_NEXT(payload_type_names, PL_HEADER, PLV1_ENCRYPTED, PLV1_FRAGMENT,
 	"HEADER",
+	"UNKNOWN",
 	"PROPOSAL_SUBSTRUCTURE",
 	"PROPOSAL_SUBSTRUCTURE_V1",
 	"TRANSFORM_SUBSTRUCTURE",
@@ -167,6 +168,7 @@ ENUM_NEXT(payload_type_short_names, PLV1_NAT_D_DRAFT_00_03, PLV1_FRAGMENT, PLV2_
 #endif /* ME */
 ENUM_NEXT(payload_type_short_names, PL_HEADER, PLV1_ENCRYPTED, PLV1_FRAGMENT,
 	"HDR",
+	"UNKN",
 	"PROP",
 	"PROP",
 	"TRANS",

src/libcharon/encoding/payloads/payload.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2007 Tobias Brunner
+ * Copyright (C) 2007-2015 Tobias Brunner
  * Copyright (C) 2005-2006 Martin Willi
  * Copyright (C) 2005 Jan Hutter
  * Hochschule fuer Technik Rapperswil
@@ -263,6 +263,11 @@ enum payload_type_t {
 	 */
 	PL_HEADER = 256,
 
+	/**
+	 * Used to handle unknown or invalid payload types.
+	 */
+	PL_UNKNOWN,
+
 	/**
 	 * PLV2_PROPOSAL_SUBSTRUCTURE, IKEv2 proposals in a SA payload.
 	 */

src/libcharon/encoding/payloads/unknown_payload.c

@@ -1,4 +1,5 @@
 /*
+ * Copyright (C) 2015 Tobias Brunner
  * Copyright (C) 2005-2006 Martin Willi
  * Copyright (C) 2005 Jan Hutter
  * Hochschule fuer Technik Rapperswil
@@ -120,6 +121,12 @@ METHOD(payload_t, get_header_length, int,
 
 METHOD(payload_t, get_payload_type, payload_type_t,
 	private_unknown_payload_t *this)
+{
+	return PL_UNKNOWN;
+}
+
+METHOD(unknown_payload_t, get_type, payload_type_t,
+	private_unknown_payload_t *this)
 {
 	return this->type;
 }
@@ -181,6 +188,7 @@ unknown_payload_t *unknown_payload_create(payload_type_t type)
 				.destroy = _destroy,
 			},
 			.is_critical = _is_critical,
+			.get_type = _get_type,
 			.get_data = _get_data,
 			.destroy = _destroy,
 		},

src/libcharon/encoding/payloads/unknown_payload.h

@@ -1,4 +1,5 @@
 /*
+ * Copyright (C) 2015 Tobias Brunner
  * Copyright (C) 2005-2006 Martin Willi
  * Copyright (C) 2005 Jan Hutter
  * Hochschule fuer Technik Rapperswil
@@ -41,6 +42,13 @@ struct unknown_payload_t {
 	 */
 	payload_t payload_interface;
 
+	/**
+	 * Get the original payload type as sent by the peer.
+	 *
+	 * @return				type of the original payload
+	 */
+	payload_type_t (*get_type) (unknown_payload_t *this);
+
 	/**
 	 * Get the raw data of this payload, without
 	 * the generic payload header.

src/libcharon/sa/ikev2/task_manager_v2.c

@@ -1184,15 +1184,17 @@ static status_t parse_message(private_task_manager_t *this, message_t *msg)
 		enumerator = msg->create_payload_enumerator(msg);
 		while (enumerator->enumerate(enumerator, &payload))
 		{
-			unknown = (unknown_payload_t*)payload;
-			type = payload->get_type(payload);
-			if (!payload_is_known(type, msg->get_major_version(msg)) &&
-				unknown->is_critical(unknown))
+			if (payload->get_type(payload) == PL_UNKNOWN)
 			{
-				DBG1(DBG_ENC, "payload type %N is not supported, "
-					 "but its critical!", payload_type_names, type);
-				status = NOT_SUPPORTED;
-				break;
+				unknown = (unknown_payload_t*)payload;
+				if (unknown->is_critical(unknown))
+				{
+					type = unknown->get_type(unknown);
+					DBG1(DBG_ENC, "payload type %N is not supported, "
+						 "but its critical!", payload_type_names, type);
+					status = NOT_SUPPORTED;
+					break;
+				}
 			}
 		}
 		enumerator->destroy(enumerator);