VPC IPv4 validation (#2026)

* Implemented throwing invalid subnet range error and fixed breaking tests.

* Implemented throwing invalid CIDR block parameter error for vpcs and subnets.

* Implemented throwing invalid destination CIDR block error.

* IPv6 addresses not accepted, strict checking disabled.

* Implemented throwing invalid subnet conflict error and fixed breaking tests.

* Implemented throwing invalid VPC range error and fixed breaking tests.

* Fixed accidentally removed ).

* Fixed test case trying to create two subnets with the same CIDR range.

moto/ec2/models.py

@@ -36,8 +36,10 @@ from .exceptions import (
     InvalidAMIIdError,
     InvalidAMIAttributeItemValueError,
     InvalidAssociationIdError,
+    InvalidCIDRBlockParameterError,
     InvalidCIDRSubnetError,
     InvalidCustomerGatewayIdError,
+    InvalidDestinationCIDRBlockParameterError,
     InvalidDHCPOptionsIdError,
     InvalidDomainError,
     InvalidID,
@@ -58,13 +60,16 @@ from .exceptions import (
     InvalidSecurityGroupDuplicateError,
     InvalidSecurityGroupNotFoundError,
     InvalidSnapshotIdError,
+    InvalidSubnetConflictError,
     InvalidSubnetIdError,
+    InvalidSubnetRangeError,
     InvalidVolumeIdError,
     InvalidVolumeAttachmentError,
     InvalidVpcCidrBlockAssociationIdError,
     InvalidVPCPeeringConnectionIdError,
     InvalidVPCPeeringConnectionStateTransitionError,
     InvalidVPCIdError,
+    InvalidVPCRangeError,
     InvalidVpnGatewayIdError,
     InvalidVpnConnectionIdError,
     MalformedAMIIdError,
@@ -2151,6 +2156,12 @@ class VPCBackend(object):
 
     def create_vpc(self, cidr_block, instance_tenancy='default', amazon_provided_ipv6_cidr_block=False):
         vpc_id = random_vpc_id()
+        try:
+            vpc_cidr_block = ipaddress.IPv4Network(six.text_type(cidr_block), strict=False)
+        except ValueError:
+            raise InvalidCIDRBlockParameterError(cidr_block)
+        if vpc_cidr_block.prefixlen < 16 or vpc_cidr_block.prefixlen > 28:
+            raise InvalidVPCRangeError(cidr_block)
         vpc = VPC(self, vpc_id, cidr_block, len(self.vpcs) == 0, instance_tenancy, amazon_provided_ipv6_cidr_block)
         self.vpcs[vpc_id] = vpc
 
@@ -2367,7 +2378,7 @@ class Subnet(TaggedEC2Resource):
         self.id = subnet_id
         self.vpc_id = vpc_id
         self.cidr_block = cidr_block
-        self.cidr = ipaddress.ip_network(six.text_type(self.cidr_block))
+        self.cidr = ipaddress.IPv4Network(six.text_type(self.cidr_block), strict=False)
         self._availability_zone = availability_zone
         self.default_for_az = default_for_az
         self.map_public_ip_on_launch = map_public_ip_on_launch
@@ -2499,7 +2510,19 @@ class SubnetBackend(object):
 
     def create_subnet(self, vpc_id, cidr_block, availability_zone):
         subnet_id = random_subnet_id()
-        self.get_vpc(vpc_id)  # Validate VPC exists
+        vpc = self.get_vpc(vpc_id)  # Validate VPC exists and the supplied CIDR block is a subnet of the VPC's
+        vpc_cidr_block = ipaddress.IPv4Network(six.text_type(vpc.cidr_block), strict=False)
+        try:
+            subnet_cidr_block = ipaddress.IPv4Network(six.text_type(cidr_block), strict=False)
+        except ValueError:
+            raise InvalidCIDRBlockParameterError(cidr_block)
+        if not (vpc_cidr_block.network_address <= subnet_cidr_block.network_address and
+                vpc_cidr_block.broadcast_address >= subnet_cidr_block.broadcast_address):
+            raise InvalidSubnetRangeError(cidr_block)
+
+        for subnet in self.get_all_subnets(filters={'vpc-id': vpc_id}):
+            if subnet.cidr.overlaps(subnet_cidr_block):
+                raise InvalidSubnetConflictError(cidr_block)
 
         # if this is the first subnet for an availability zone,
         # consider it the default
@@ -2759,6 +2782,11 @@ class RouteBackend(object):
             elif EC2_RESOURCE_TO_PREFIX['internet-gateway'] in gateway_id:
                 gateway = self.get_internet_gateway(gateway_id)
 
+        try:
+            ipaddress.IPv4Network(six.text_type(destination_cidr_block), strict=False)
+        except ValueError:
+            raise InvalidDestinationCIDRBlockParameterError(destination_cidr_block)
+
         route = Route(route_table, destination_cidr_block, local=local,
                       gateway=gateway,
                       instance=self.get_instance(