Include src address in hash of initial message for Main Mode

If two initiators use the same SPI and also use the same SA proposal the
hash for the initial message would be exactly the same.  For IKEv2 and
Aggressive Mode that's not a problem as these messages include random
data (Ni, KEi payloads).

src/libcharon/sa/ike_sa_manager.c

@@ -954,6 +954,34 @@ static u_int64_t get_spi(private_ike_sa_manager_t *this)
 	return 0;
 }
 
+/**
+ * Calculate the hash of the initial IKE message.  Memory for the hash is
+ * allocated on success.
+ *
+ * @returns TRUE on success
+ */
+static bool get_init_hash(private_ike_sa_manager_t *this, message_t *message,
+						  chunk_t *hash)
+{
+	if (!this->hasher)
+	{	/* this might be the case when flush() has been called */
+		return FALSE;
+	}
+	if (message->get_exchange_type(message) == ID_PROT)
+	{	/* include the source for Main Mode as the hash will be the same if
+		 * SPIs are reused by two initiators that use the same proposal */
+		host_t *src = message->get_source(message);
+
+		if (!this->hasher->allocate_hash(this->hasher,
+										 src->get_address(src), NULL))
+		{
+			return FALSE;
+		}
+	}
+	return this->hasher->allocate_hash(this->hasher,
+									   message->get_packet_data(message), hash);
+}
+
 /**
  * Check if we already have created an IKE_SA based on the initial IKE message
  * with the given hash.
@@ -1158,14 +1186,12 @@ METHOD(ike_sa_manager_t, checkout_by_message, ike_sa_t*,
 		}
 	}
 
-	if (is_init && this->hasher)
-	{	/* initial request. checking for the hasher prevents crashes once
-		 * flush() has been called */
+	if (is_init)
+	{
 		u_int64_t our_spi;
 		chunk_t hash;
 
-		if (!this->hasher->allocate_hash(this->hasher,
-									message->get_packet_data(message), &hash))
+		if (!get_init_hash(this, message, &hash))
 		{
 			DBG1(DBG_MGR, "ignoring message, failed to hash message");
 			id->destroy(id);