aws_security_group resource

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Use the aws_security_group InSpec audit resource to test detailed properties of an individual Security Group (SG).

SGs are a networking construct which contain ingress and egress rules for network communications. SGs may be attached to EC2 instances, as well as certain other AWS resources. Along with Network Access Control Lists, SGs are one of the two main mechanisms of enforcing network-level security.

Limitations

While this resource provides facilities for searching inbound and outbound rules on a variety of criteria, there is currently no support for performing matches based on:

• References to VPC peers or other AWS services (that is, no support for searches based on ‘prefix lists’).

Syntax

describe aws_security_group('sg-12345678') do
  it { should exist }
end

# May also use hash syntax
describe aws_security_group(group_id: 'sg-12345678') do
  it { should exist }
end

# Ensure you have a Security Group with a specific name.  Names are
# unique within a VPC but not across VPCs.
# Using only Group returns an error if multiple SGs match.
describe aws_security_group(group_name: 'my-group') do
  it { should exist }
end

# Add vpc_id to ensure uniqueness.
describe aws_security_group(group_name: 'my-group', vpc_id: 'vpc-12345678') do
  it { should exist }
end

Parameters

You must provide at least one parameter; group_id, group_name or vpc_id

group_id (required if no other parameter provided)

The Security Group ID which uniquely identifies the SG. This can be passed either as a string or as a group_id: 'value' key-value entry in a hash.

group_name (required if no other parameter provided)

The Security Group name. This can be passed either as a string or as a group_name: 'value' key-value entry in a hash.

vpc_id (required if no other parameter provided)

The ID of the VPC associated with the SG. This can be passed either as a string or as a vpc_id: 'value' key-value entry in a hash.

See also the AWS documentation on Security Groups.

Properties

Examples

Test outbound rules

describe aws_security_group(group_name: isolated_servers) do
  its('outbound_rules.last') { should_not include(ip_ranges:['0.0.0.0/0']) }
end

Test a rule that allows All Traffic

describe aws_security_group(group_name: my_group) do
  it { should allow_in(ipv4_range: ["10.1.2.0/24", "10.3.2.0/24"], protocol: 'all') }
end

Ensure a SG only allows SSH from a specific range

describe aws_security_group(group_name: linux_servers) do
  it { should allow_in(port: 22, ipv4_range: '10.5.0.0/16') }
  it { should_not allow_in(port: 22, ipv4_range: '0.0.0.0/0') }
end

Ensure that the careful_updates Security Group may only initiate contact with specific IPs.

describe aws_security_group(group_name: 'careful_updates') do

  # If you have two rules, with one CIDR each:
  [ '10.7.23.12/32', '10.8.23.12/32' ].each do |allowed_destination|
    # This doesn't care about which ports are enabled
    it { should allow_out(ipv4_range: allowed_destination) }
  end

  # If you have one rule with two CIDRs:
  it { should allow_out(ipv4_range: [ '10.7.23.12/32', '10.8.23.12/32' ]) }

  # Expect exactly three rules.
  its('outbound_rules.count') { should cmp 3 }
end

Ensure that the canary_deployments Security Group only allows access from one specific security group id on port 443.

describe aws_security_group(group_name: 'canary_deployments') do
  it { should allow_in_only(port: 443, security_group: "sg-33334444") }
end

Matchers

This InSpec audit resource has the following special matchers. For a full list of additional available matchers, please visit our Universal Matchers page.

allow

The allow series of matchers includes:

• allow_in
• allow_out
• allow_in_only
• allow_out_only

The allow series of matchers enable you to perform queries about what network traffic would be permitted through the Security Group rule set.

allow_in and allow_in_exactly examine inbound rules, and allow_out and allow_out_exactly examine outbound rules.

allow_in and allow_out examine if at least one rule that matches the criteria exists. allow_in and allow_out also perform inexact (ie, range-based or subset-based) matching on ports and IP addresses ranges, allowing you to specify a candidate port or IP address and determine if it is covered by a rule.

allow_in_only and allow_out_only examines if exactly one rule exists (but see position, below), and if it matches the criteria (this is useful for ensuring no unexpected rules have been added). Additionally, allow_in_only and allow_out_only do not perform inexact matching; you must specify exactly the port range or IP address(es) you wish to match.

Matchers search criteria

The matchers accept a key-value list of search criteria. For a rule to match, it must match all provided criteria.

from_port

Determines if a rule exists whose port range begins at the specified number. The word from_ does not relate to inbound/outbound directionality; it relates to the port range (“counting from"). from_port is an exact criterion; so if the rule allows 1000-2000 and you specify a from_port of 1001, it does not match.

ipv4_range

Specifies an IPv4 address or subnet as a CIDR, or a list of them, to be checked as a permissible origin (for allow_in) or destination (for allow_out) for traffic. Each AWS Security Group rule may have multiple allowed source IP ranges.

ipv6_range

Specifies an IPv6 address or subnet as a CIDR, or a list of them, to be checked as a permissible origin (for allow_in) or destination (for allow_out) for traffic. Each AWS Security Group rule may have multiple allowed source IP ranges.

port

Determines if a particular TCP/IP port is reachable. allow_in and allow_out examine whether the specified port is included in the port range of a rule, while allow_in. You may specify the port as a string ('22') or as a number.

position

A one-based index into the list of rules. If provided, this restricts the evaluation to the rule at that position. You may also use the special values :first and :last. position may also be used to enable allow_in_only and allow_out_only to work with multi-rule Security Groups.

protocol

Specifies the IP protocol. tcp, udp, and icmp are some typical values. The string "-1" or any is used to indicate any protocol.

to_port

Determines if a rule exists whose port range ends at the specified number. The word to_ does not relate to inbound/outbound directionality; it relates to the port range (“counting to"). to_port is an exact criterion; so if the rule allows 1000-2000 and you specify a to_port of 1999, it does not match.

security_group

Specifies a security-group id, to be checked as permissible origin (for allow_in) or destination (for allow_out) for traffic. Each AWS Security Group rule may have multiple allowed source or destination security groups.

describe aws_security_group(group_name: 'mixed-functionality-group') do
  # Allow RDP from defined range
  it { should allow_in(port: 3389, ipv4_range: '10.5.0.0/16') }
  it { should allow_in(port: 3389, ipv6_range: '2001:db8::/122') }

  # Allow SSH from two ranges
  it { should allow_in(port: 22, ipv4_range: ['10.5.0.0/16', '10.2.3.0/24']) }

  # Check Bacula port range
  it { should allow_in(from_port: 9101, to_port: 9103, ipv4_range: '10.6.7.0/24') }

  # Assuming the AWS SG allows 9001-9003, use inexact matching to check 9002
  it { should allow_in(port: 9002) }

  # Assuming the AWS SG allows 10.2.1.0/24, use inexact matching to check 10.2.1.33/32
  it { should allow_in(ipv4_range: '10.2.1.33/32') }

  # Ensure the 3rd outbound rule is TCP-based
  it { should allow_in(protocol: 'tcp', position: 3') }
  # Do not allow unrestricted IPv4 access.
  it { should_not allow_in(ipv4_range: '0.0.0.0/0') }
  # Allow unrestricted access from security-group.
  it { should allow_in(security_group: 'sg-11112222') }
end

Suppose you have a Group that should allow SSH and RDP from the admin network, 10.5.0.0/16. The resource has 2 rules to allow this, and you want to ensure no others have been added.

describe aws_security_group(group_name: 'admin-group') do
  # Allow RDP from a defined range and nothing else
  # The SG must have this rule in position 1 and it must match this exactly
  it { should allow_in_only(port: 3389, ipv4_range: '10.5.0.0/16', position: 1) }

  # Specify position 2 for the SSH rule.  Without `position`,
  # allow_in_only only allows one rule, total.
  it { should allow_in_only(port: 22, ipv4_range: '10.5.0.0/16', position: 2) }

  # Because this is an _only matcher, this fails - _only matchers
  # use exact IP matching.
  it { should allow_in_only(port: 3389, ipv4_range: '10.5.1.34/32', position: 1) }
end

exist

The control will pass if the describe returns at least one result.

Use should_not to test the entity should not exist.

it { should exist }

it { should_not exist }

AWS Permissions

Your Principal will need the ec2:DescribeSecurityGroups action with Effect set to Allow.

You can find detailed documentation at Actions, Resources, and Condition Keys for Amazon EC2.