Control: 5.1 Ensure no Network ACLs allow ingress from 0.0.0.0/0 to remote server administration ports

Description

The Network Access Control List (NACL) function provide stateless filtering of ingress and egress network traffic to AWS resources. It is recommended that no NACL allows unrestricted ingress access to remote server administration ports, such as SSH to port 22 and RDP to port 3389.

Public access to remote server administration ports, such as 22 and 3389, increases resource attack surface and unnecessarily raises the risk of resource compromise.

Remediation

From Console

Login VPC Console at VPC
In the left pane, click Network ACLs
For each network ACL to remediate, perform the following:
Select the respective network ACL
Choose the Inbound Rules tab and click Edit Inbound rules
Check remote server access port entries. Note A Port value of ALL or a port range such as 0-1024 are inclusive of port 22, 3389, and other remote server administration ports.
Either
- A) Update the source field to a range other than 0.0.0.0/0 or
- B) Click Remove the offending inbound rule
Click Save changes

Usage

Run the control in your terminal:

powerpipe control run aws_compliance.control.cis_v130_5_1

Snapshot and share results via Turbot Pipes:

powerpipe login
powerpipe control run aws_compliance.control.cis_v130_5_1 --share

SQL

This control uses a named query:

with bad_rules as (
  select
    network_acl_id,
    count(*) as num_bad_rules,
    tags,
    region,
    account_id
  from
    aws_vpc_network_acl,
    jsonb_array_elements(entries) as att
  where
    att ->> 'Egress' = 'false' -- as per aws egress = false indicates the ingress
    and (
      att ->> 'CidrBlock' = '0.0.0.0/0'
      or att ->> 'Ipv6CidrBlock' =  '::/0'
    )
    and att ->> 'RuleAction' = 'allow'
    and (
      (
        att ->> 'Protocol' = '-1' -- all traffic
        and att ->> 'PortRange' is null
      )
      or (
        (att -> 'PortRange' ->> 'From') :: int <= 22
        and (att -> 'PortRange' ->> 'To') :: int >= 22
        and att ->> 'Protocol' in('6', '17')  -- TCP or UDP
      )
      or (
        (att -> 'PortRange' ->> 'From') :: int <= 3389
        and (att -> 'PortRange' ->> 'To') :: int >= 3389
        and att ->> 'Protocol' in('6', '17')  -- TCP or UDP
    )
  )
  group by
    network_acl_id,
    region,
    account_id,
    tags
  order by
    network_acl_id,
    region,
    account_id,
    tags
),
aws_vpc_network_acls as (
  select
    network_acl_id,
    tags,
    partition,
    region,
    account_id
  from
    aws_vpc_network_acl
  order by
    network_acl_id,
    region,
    account_id
)
select
  'arn:' || acl.partition || ':ec2:' || acl.region || ':' || acl.account_id || ':network-acl/' || acl.network_acl_id  as resource,
  case
    when bad_rules.network_acl_id is null then 'ok'
    else 'alarm'
  end as status,
  case
    when bad_rules.network_acl_id is null then acl.network_acl_id || ' does not allow ingress to port 22 or 3389 from 0.0.0.0/0 or ::/0.'
    else acl.network_acl_id || ' contains ' || bad_rules.num_bad_rules || ' rule(s) allowing ingress to port 22 or 3389 from 0.0.0.0/0 or ::/0.'
  end as reason
  
  , acl.region, acl.account_id
from
  aws_vpc_network_acls as acl
  left join bad_rules on bad_rules.network_acl_id = acl.network_acl_id;

Control: 5.1 Ensure no Network ACLs allow ingress from 0.0.0.0/0 to remote server administration ports

Description

Remediation

From Console

Usage

SQL

Tags