An ingress Network ACL rule allows specific ports from /0.

Explanation

Opening up ACLs to the public internet is potentially dangerous. You should restrict access to IP addresses or ranges that explicitly require it where possible.

Possible Impact

The ports are exposed for ingressing data to the internet

Suggested Resolution

Set a more restrictive cidr range

Insecure Example

The following example will fail the aws-vpc-no-public-ingress check.

resource "aws_network_acl_rule" "bad_example" {
  egress         = false
  protocol       = "tcp"
  from_port      = 22
  to_port        = 22
  rule_action    = "allow"
  cidr_block     = "0.0.0.0/0"
}

Secure Example

The following example will pass the aws-vpc-no-public-ingress check.

resource "aws_network_acl_rule" "good_example" {
  egress         = false
  protocol       = "tcp"
  from_port      = 22
  to_port        = 22
  rule_action    = "allow"
  cidr_block     = "10.0.0.0/16"
}

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