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

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

ARM