Control: 7.4 Ensure that HTTP(S) access from the Internet is evaluated and restricted

Description

Network security groups should be periodically evaluated for port misconfigurations. Where certain ports and protocols may be exposed to the Internet, they should be evaluated for necessity and restricted wherever they are not explicitly required and narrowly configured.

The potential security problem with using HTTP(S) over the Internet is that attackers can use various brute force techniques to gain access to Azure resources. Once the attackers gain access, they can use the resource as a launch point for compromising other resources within the Azure tenant.

Remediation

From Azure Portal

Go to Virtual machines.
For each VM, open the Networking blade.
Click on Inbound port rules.
Delete the rule with:

Port = 80/443 OR [port range containing 80/443]
Protocol = TCP OR Any
Source = Any (*) OR IP Addresses(0.0.0.0/0) OR Service Tag(Internet)
Action = Allow

From Azure CLI

Run below command to list network security groups:

az network nsg list --subscription <subscription-id> --output table

For each network security group, run below command to list the rules associated with the specified port:

az network nsg rule list --resource-group <resource-group> --nsg-name <nsg-name> --query "[?destinationPortRange=='80 or 443']"

Run the below command to delete the rule with:

Port = 80/443 OR [port range containing 80/443]
Protocol = TCP OR "*"
Source = Any (*) OR IP Addresses(0.0.0.0/0) OR Service Tag(Internet)
Action = Allow

az network nsg rule delete --resource-group <resource-group> --nsg-name <nsg-name> --name <rule-name>

Usage

Run the control in your terminal:

powerpipe control run azure_compliance.control.cis_v300_7_4

Snapshot and share results via Turbot Pipes:

powerpipe login
powerpipe control run azure_compliance.control.cis_v300_7_4 --share

SQL

This control uses a named query:

with network_sg as (
  select distinct
    name sg_name
  from
    azure_network_security_group nsg,
    jsonb_array_elements(security_rules) sg,
    jsonb_array_elements_text(sg -> 'properties' -> 'destinationPortRanges' || (sg -> 'properties' -> 'destinationPortRange') :: jsonb) dport,
    jsonb_array_elements_text(sg -> 'properties' -> 'sourceAddressPrefixes' || (sg -> 'properties' -> 'sourceAddressPrefix') :: jsonb) sip
  where
    sg -> 'properties' ->> 'access' = 'Allow'
    and sg -> 'properties' ->> 'direction' = 'Inbound'
    and sg -> 'properties' ->> 'protocol' ilike 'TCP'
    and sip in
    (
      '*',
      '0.0.0.0',
      '0.0.0.0/0',
      'Internet',
      'any',
      '<nw>/0',
      '/0'
    )
    and
    (
      dport in
      (
        '80',
        '443',
        '*'
      )
      or
      (
        dport like '%-%'
        and split_part(dport, '-', 1) :: integer <= 80
        and split_part(dport, '-', 2) :: integer >= 80
        and split_part(dport, '-', 1) :: integer <= 443
        and split_part(dport, '-', 2) :: integer >= 443
      )
    )
)
select
  sg.id resource,
  case
    when nsg.sg_name is null then 'ok'
    else 'alarm'
  end as status,
  case
    when nsg.sg_name is null then sg.title || ' restricts HTTPS access from internet.'
    else sg.title || ' allows HTTPS access from internet.'
  end as reason
  
  , sg.resource_group as resource_group
  , sub.display_name as subscription
from
  azure_network_security_group sg
  left join network_sg nsg on nsg.sg_name = sg.name
  left join azure_subscription sub on sub.subscription_id = sg.subscription_id;