feat(query): implements "Beta - Activity Log Alert For Delete Policy Assignment"

[cx-andre-pereira]

Reason for Proposed Changes

• Currently there is no query to ensure that there is a "azurerm_monitor_activity_log_alert" resource configured to capture delete policy assignment events.

• Quoting CIS_Microsoft_Azure_Foundations_Benchmark_v5.0.0 page 231: "Monitoring for delete policy assignment events gives insight into changes done in "azure policy - assignments" and can reduce the time it takes to detect unsolicited changes."

• Through the CIS benchmark we can also determine that detecting the target configuration boils down to checking 2 fields in the criteria block:

  • category should be set to "Administrative"
  • operation_name should be set to "Microsoft.Authorization/policyAssignments/delete"

• Additionally we must ensure the log alert resource does not set any "filters" that act "on Level, Status or
  Caller" these can be set on the "azurerm_monitor_activity_log_alert" resource through the following fields : "caller", "level", "levels", "status", "statuses", "sub_status" or "sub_statuses". Since these could suppress or cause the log alert to miss relevant events they must not be set.

• Finally it must be ensured that the "action_group_id" field is set (inside an "action" block).

Proposed Changes

• Implemented the missing query.

• The query will trigger if:

  • Either of the 2 mandatory fields is incorrect, if so all "azurerm_monitor_activity_log_alert" are flagged with the results pointing to their "criteria" fields specifically.
  • Both fields are correct but there is at least 1 "filter" field defined.
  • Both fields are correct and no filter is defined but the the "action_group_id" field is missing.

• In a given document if there are multiple "azurerm_monitor_activity_log_alert" and none of them fully align with the required requisites the query will prioritize flagging all the ones only missing the "action_group_id" first, then all the ones that flag due to a filter being set and, if none of the resources set the two mandatory fields to the expected values, it will flag all log alert resources. These priorities are demonstrated through the positive4.tf and positive5.tf tests and their results.

I submit this contribution under the Apache-2.0 license.

[github-actions]

KICS version: v2.1.13

Category Results CRITICAL 0 HIGH 0 MEDIUM 0 LOW 0 INFO 0 TRACE 0 TOTAL 0	Metric Values Files scanned 1 Files parsed 1 Files failed to scan 0 Total executed queries 47 Queries failed to execute 0 Execution time 0

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