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Security group ingress with all protocols

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Metadata

Id: cloudformation-aws-security-group-ingress-with-all-protocols

Provider: AWS

Platform: CloudFormation

Severity: Medium

Category: Networking and Firewall

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Description

Setting IpProtocol to -1 allows all protocols and all ports. This greatly increases attack surface and can expose services or enable lateral movement if an ingress rule is too permissive.

Check AWS::EC2::SecurityGroupIngress resources and AWS::EC2::SecurityGroup resources’ SecurityGroupIngress entries. IpProtocol must not be set to -1. Resources with IpProtocol: -1 will be flagged. Specify explicit protocols (for example, tcp, udp, or icmp, or their numeric protocol values) and define FromPort/ToPort where applicable. If broader access is required, restrict the source to a specific CIDR or use a referenced security group.

Secure configuration examples:

MyIngressRule:
  Type: AWS::EC2::SecurityGroupIngress
  Properties:
    IpProtocol: tcp
    FromPort: 443
    ToPort: 443
    CidrIp: 10.0.0.0/24

MySecurityGroup:
  Type: AWS::EC2::SecurityGroup
  Properties:
    GroupDescription: Example SG
    SecurityGroupIngress:
      - IpProtocol: tcp
        FromPort: 22
        ToPort: 22
        CidrIp: 203.0.113.5/32

Compliant Code Examples

Resources:
  InstanceSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Allow http to client host
      VpcId:
         Ref: myVPC
      SecurityGroupIngress:
      - IpProtocol: tcp
        FromPort: 80
        ToPort: 80
        CidrIp: 0.0.0.0/0
      SecurityGroupEgress:
      - IpProtocol: tcp
        FromPort: 80
        ToPort: 80
        CidrIp: 0.0.0.0/0
  OutboundRule:
    Type: AWS::EC2::SecurityGroupEgress
    Properties:
      IpProtocol: tcp
      FromPort: 0
      ToPort: 65535
      DestinationSecurityGroupId:
        Fn::GetAtt:
        - TargetSG
        - GroupId
      GroupId:
        Fn::GetAtt:
        - SourceSG
        - GroupId
  InboundRule:
    Type: AWS::EC2::SecurityGroupIngress
    Properties:
      IpProtocol: tcp
      FromPort: 0
      ToPort: 65535
      SourceSecurityGroupId:
        Fn::GetAtt:
        - SourceSG
        - GroupId
      GroupId:
        Fn::GetAtt:
        - TargetSG
        - GroupId

{
  "Resources": {
    "InstanceSecurityGroup": {
      "Type": "AWS::EC2::SecurityGroup",
      "Properties": {
        "SecurityGroupIngress": [
          {
            "IpProtocol": "tcp",
            "FromPort": 80,
            "ToPort": 80,
            "CidrIp": "0.0.0.0/0"
          }
        ],
        "SecurityGroupEgress": [
          {
            "FromPort": 80,
            "ToPort": 80,
            "CidrIp": "0.0.0.0/0",
            "IpProtocol": "tcp"
          }
        ],
        "GroupDescription": "Allow http to client host",
        "VpcId": {
          "Ref": "myVPC"
        }
      }
    },
    "OutboundRule": {
      "Type": "AWS::EC2::SecurityGroupEgress",
      "Properties": {
        "IpProtocol": "tcp",
        "FromPort": 0,
        "ToPort": 65535,
        "DestinationSecurityGroupId": {
          "Fn::GetAtt": [
            "TargetSG",
            "GroupId"
          ]
        },
        "GroupId": {
          "Fn::GetAtt": [
            "SourceSG",
            "GroupId"
          ]
        }
      }
    },
    "InboundRule": {
      "Type": "AWS::EC2::SecurityGroupIngress",
      "Properties": {
        "ToPort": 65535,
        "SourceSecurityGroupId": {
          "Fn::GetAtt": [
            "SourceSG",
            "GroupId"
          ]
        },
        "GroupId": {
          "Fn::GetAtt": [
            "TargetSG",
            "GroupId"
          ]
        },
        "IpProtocol": "tcp",
        "FromPort": 0
      }
    }
  }
}

Non-Compliant Code Examples

Resources:
  InstanceSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Allow http to client host
      VpcId:
         Ref: myVPC
      SecurityGroupIngress:
      - IpProtocol: -1
        FromPort: 80
        ToPort: 80
        CidrIp: 0.0.0.0/0
      SecurityGroupEgress:
      - IpProtocol: tcp
        FromPort: 80
        ToPort: 80
        CidrIp: 0.0.0.0/0
  OutboundRule:
    Type: AWS::EC2::SecurityGroupEgress
    Properties:
      IpProtocol: tcp
      FromPort: 0
      ToPort: 65535
      DestinationSecurityGroupId:
        Fn::GetAtt:
        - TargetSG
        - GroupId
      GroupId:
        Fn::GetAtt:
        - SourceSG
        - GroupId
  InboundRule:
    Type: AWS::EC2::SecurityGroupIngress
    Properties:
      IpProtocol: -1
      FromPort: 0
      ToPort: 65535
      SourceSecurityGroupId:
        Fn::GetAtt:
        - SourceSG
        - GroupId
      GroupId:
        Fn::GetAtt:
        - TargetSG
        - GroupId

{
  "Resources": {
    "InstanceSecurityGroup": {
      "Type": "AWS::EC2::SecurityGroup",
      "Properties": {
        "VpcId": {
          "Ref": "myVPC"
        },
        "SecurityGroupIngress": [
          {
            "IpProtocol": -1,
            "FromPort": 80,
            "ToPort": 80,
            "CidrIp": "0.0.0.0/0"
          }
        ],
        "SecurityGroupEgress": [
          {
            "FromPort": 80,
            "ToPort": 80,
            "CidrIp": "0.0.0.0/0",
            "IpProtocol": "tcp"
          }
        ],
        "GroupDescription": "Allow http to client host"
      }
    },
    "OutboundRule": {
      "Type": "AWS::EC2::SecurityGroupEgress",
      "Properties": {
        "ToPort": 65535,
        "DestinationSecurityGroupId": {
          "Fn::GetAtt": [
            "TargetSG",
            "GroupId"
          ]
        },
        "GroupId": {
          "Fn::GetAtt": [
            "SourceSG",
            "GroupId"
          ]
        },
        "IpProtocol": "tcp",
        "FromPort": 0
      }
    },
    "InboundRule": {
      "Type": "AWS::EC2::SecurityGroupIngress",
      "Properties": {
        "IpProtocol": -1,
        "FromPort": 0,
        "ToPort": 65535,
        "SourceSecurityGroupId": {
          "Fn::GetAtt": [
            "SourceSG",
            "GroupId"
          ]
        },
        "GroupId": {
          "Fn::GetAtt": [
            "TargetSG",
            "GroupId"
          ]
        }
      }
    }
  }
}