GCP IAM - Publicly exposed storage bucket

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Id	4a433846-4b05-4a27-99d7-92093feded79
Rulename	GCP IAM - Publicly exposed storage bucket
Description	Detects possible misconfiguration for bucket policy making it publicly available.
Severity	Medium
Tactics	Discovery
Techniques	T1069
Required data connectors	GCPIAMDataConnector
Kind	Scheduled
Query frequency	1h
Query period	1h
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/GoogleCloudPlatformIAM/Analytic Rules/GCPIAMPublicBucket.yaml
Version	1.0.1
Arm template	4a433846-4b05-4a27-99d7-92093feded79.json

KQL

GCP_IAM
| where PayloadMethodname =~ 'google.iam.v1.IAMPolicy.SetIamPolicy'
| where ResourceType has 'bucket'
| extend members = parse_json(todynamic(PayloadRequestPolicyBindings))[0]['members']
| extend action = parse_json(todynamic(PayloadRequestPolicyBindings))[0]['action']
| where members in~ ('allUsers', 'allAuthenticatedUsers')
| where action =~ 'ADD'
| extend AccountName = tostring(split(PayloadAuthenticationinfoPrincipalemail, "@")[0]), AccountUPNSuffix = tostring(split(PayloadAuthenticationinfoPrincipalemail, "@")[1])

YAML

entityMappings:
- entityType: Account
  fieldMappings:
  - identifier: FullName
    columnName: PayloadAuthenticationinfoPrincipalemail
  - identifier: Name
    columnName: AccountName
  - identifier: UPNSuffix
    columnName: AccountUPNSuffix
- entityType: IP
  fieldMappings:
  - identifier: Address
    columnName: SrcIpAddr
tactics:
- Discovery
requiredDataConnectors:
- dataTypes:
  - GCP_IAM
  connectorId: GCPIAMDataConnector
id: 4a433846-4b05-4a27-99d7-92093feded79
severity: Medium
status: Available
query: |
  GCP_IAM
  | where PayloadMethodname =~ 'google.iam.v1.IAMPolicy.SetIamPolicy'
  | where ResourceType has 'bucket'
  | extend members = parse_json(todynamic(PayloadRequestPolicyBindings))[0]['members']
  | extend action = parse_json(todynamic(PayloadRequestPolicyBindings))[0]['action']
  | where members in~ ('allUsers', 'allAuthenticatedUsers')
  | where action =~ 'ADD'
  | extend AccountName = tostring(split(PayloadAuthenticationinfoPrincipalemail, "@")[0]), AccountUPNSuffix = tostring(split(PayloadAuthenticationinfoPrincipalemail, "@")[1])  
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/GoogleCloudPlatformIAM/Analytic Rules/GCPIAMPublicBucket.yaml
kind: Scheduled
queryPeriod: 1h
version: 1.0.1
name: GCP IAM - Publicly exposed storage bucket
queryFrequency: 1h
triggerThreshold: 0
relevantTechniques:
- T1069
description: |
    'Detects possible misconfiguration for bucket policy making it publicly available.'
triggerOperator: gt

ARM