Usage of --external-checks-dir, custom checks do not get recognised

Describe the bug: I created a basic yaml custom rules and I plan to create several new rules. Currently I don’t get why the custom rules does not get asserted as it should be.

My custom rule checkov-checks/chekov_custom_rule_tagging.yaml looks like that:

---
metadata:
 name: "Check that all resources are tagged with the key - InfoSecClass"
 id: "CKV_AWS_123"
 category: "GENERAL_SECURITY"
scope:
 provider: aws
definition:
       cond_type: "attribute"
       resource_types: "AWS::EC2::SecurityGroup"
       attribute: "tags.infosecclass"
       operator: "exists"

And I run it via checkov -f src/test/rds-cf-template.json --external-checks-dir ./checkov-checks

Is there something I am doing wrong or is the rule malformed/incorrect?

Currently I am using the Version 2.0.1079

[tsmithv11]

This is a case where a Python check is likely better, but here are both options:

from checkov.common.models.enums import CheckResult, CheckCategories
from checkov.cloudformation.checks.resource.base_resource_value_check import BaseResourceCheck

class BagTagging(BaseResourceCheck):
    def __init__(self):
        name = "Check that all resources are tagged with the key - InfoSecClass"
        id = "CKV_AWS_999"
        supported_resources = ['AWS::EC2::SecurityGroup']
        categories = (CheckCategories.GENERAL_SECURITY)
        super().__init__(name=name, id=id, categories=categories, supported_resources=supported_resources)

    def scan_resource_conf(self, conf):
        if 'Properties' in conf.keys():
            if 'Tags' in conf['Properties'].keys():
                for tag in conf['Properties']['Tags']:
                    if tag['Key'] == 'infosecclass':
                        return CheckResult.PASSED
        return CheckResult.FAILED

check = BagTagging()

or in YAML:

---
metadata:
 name: "Check that all resources are tagged with the key - InfoSecClass"
 id: "CKV_AWS_999"
 category: "GENERAL_SECURITY"
scope:
 provider: aws
definition:
       cond_type: "attribute"
       resource_types: "AWS::EC2::SecurityGroup"
       attribute: Tags.*.Key
       operator: "equals"
       value: "infosecclass"

[antoniorodriguezmoreno]

Thank you for the help @tsmithv11 ! I was able to run it successfully.