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

name: GCP IAM - Publicly exposed storage bucket
id: 4a433846-4b05-4a27-99d7-92093feded79
description: |
    'Detects possible misconfiguration for bucket policy making it publicly available.'
triggerThreshold: 0
entityMappings:
- fieldMappings:
  - columnName: PayloadAuthenticationinfoPrincipalemail
    identifier: FullName
  - columnName: AccountName
    identifier: Name
  - columnName: AccountUPNSuffix
    identifier: UPNSuffix
  entityType: Account
- fieldMappings:
  - columnName: SrcIpAddr
    identifier: Address
  entityType: IP
version: 1.0.1
triggerOperator: gt
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])  
tactics:
- Discovery
kind: Scheduled
queryFrequency: 1h
severity: Medium
queryPeriod: 1h
requiredDataConnectors:
- dataTypes:
  - GCP_IAM
  connectorId: GCPIAMDataConnector
status: Available
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/GoogleCloudPlatformIAM/Analytic Rules/GCPIAMPublicBucket.yaml
relevantTechniques:
- T1069

ARM