How do I properly use the VpcId Property inside Security Group?

Question

I have a cloudformation snippet that looks roughly like this :

ContainerSecurityGroup:
    Type :  AWS::EC2::SecurityGroup
    Properties : 
       InstanceId: !Ref ContainerSG
       GroupDescription :  "ECS Containers Security Group"
       VpcId : 
         !Join :
                -  ""
                - -  "{{resolve:ssm:"
                  -  /
                  -  "ca"
                  -  /
                  -  "config"
                  -  /
                  -  "network"
                  -  /
                  -  "vpc_id:"
                  -  !Sub   "${ParamVersion}"
                  -  "}}"
       GroupName :  !Sub   ${Env}-${ServiceName}-sg
       SecurityGroupIngress :
        -  IpProtocol :  tcp
           FromPort :  8080
           ToPort :  8080
           CidrIp :  10.49.63.0/24
        -  IpProtocol :  tcp
           FromPort :  8080
           ToPort :  8080
           CidrIp :  10.93.0.0/16
        -  IpProtocol :  tcp
           FromPort :  8080
           ToPort :  8080
           CidrIp :  10.97.0.0/16
        -  IpProtocol :  tcp
           FromPort :  8080
           ToPort :  8080
           CidrIp :  10.50.128.0/21
        -  IpProtocol :  tcp
           FromPort :  8080
           ToPort :  8080
           CidrIp :  10.50.144.0/24
        -  IpProtocol :  tcp
           FromPort :  8080
           ToPort :  8080
           CidrIp :  172.25.0.0/16

But when I try to run this, I get the following error:

Template contains errors.: Template format error: [/Resources/ContainerSecurityGroup/Type/VpcId] map keys must be strings; received a map instead

Can anybody help me to resolve this one? Is there perhaps a workaround I have not considered? Would appreciate your help on this, thank you.

Answer 1

Why are you even joining? Can't you just use:

ContainerSecurityGroup:
    Type :  AWS::EC2::SecurityGroup
    Properties : 
       InstanceId: !Ref ContainerSG
       GroupDescription :  "ECS Containers Security Group"
       VpcId : !Sub '{{resolve:ssm:/ca/config/network/vpc_id:${ParamVersion}}}'
       GroupName :  !Sub   ${Env}-${ServiceName}-sg
       SecurityGroupIngress :
        -  IpProtocol :  tcp
           FromPort :  8080
           ToPort :  8080
           CidrIp :  10.49.63.0/24
        -  IpProtocol :  tcp
           FromPort :  8080
           ToPort :  8080
           CidrIp :  10.93.0.0/16
        -  IpProtocol :  tcp
           FromPort :  8080
           ToPort :  8080
           CidrIp :  10.97.0.0/16
        -  IpProtocol :  tcp
           FromPort :  8080
           ToPort :  8080
           CidrIp :  10.50.128.0/21
        -  IpProtocol :  tcp
           FromPort :  8080
           ToPort :  8080
           CidrIp :  10.50.144.0/24
        -  IpProtocol :  tcp
           FromPort :  8080
           ToPort :  8080
           CidrIp :  172.25.0.0/16