GCP cloudfunctions functions update

Severity: high
Log types: GCP.AuditLog
Reference: https://rhinosecuritylabs.com/gcp/privilege-escalation-google-cloud-platform-part-1/
Source: github.com/panther-labs/panther-analysis

The Identity and Access Management (IAM) service manages authorization and authentication for a GCP environment. This means that there are very likely multiple privilege escalation methods that use the IAM service and/or its permissions.

MITRE ATT&CK coverage

Tactic	Techniques
Privilege Escalation	`T1548` Abuse Elevation Control Mechanism

Rule body yaml

AnalysisType: rule
RuleID: "GCP.Cloudfunctions.Functions.Update"
DisplayName: "GCP cloudfunctions functions update"
Description:
  The Identity and Access Management (IAM) service manages authorization and authentication for
  a GCP environment. This means that there are very likely multiple privilege escalation methods that use
  the IAM service and/or its permissions.
Enabled: true
Filename: gcp_cloudfunctions_functions_update.py
LogTypes:
  - GCP.AuditLog
Severity: High
DedupPeriodMinutes: 60
Threshold: 1
Reference: https://rhinosecuritylabs.com/gcp/privilege-escalation-google-cloud-platform-part-1/
Runbook:
  Confirm this was authorized and necessary behavior. This is not a vulnerability in GCP, it is a vulnerability
  in how GCP environment is configured, so it is necessary to be aware of these attack vectors and to defend against
  them. It’s also important to remember that privilege escalation does not necessarily need to pass through the
  IAM service to be effective. Make sure to follow the principle of least-privilege in your environments to help
  mitigate these security risks.
Reports:
  MITRE ATT&CK:
    - TA0004:T1548
Tests:
  - Name: privilege-escalation
    ExpectedResult: true
    Log:
      protoPayload:
        authorizationInfo:
          - granted: true
            permission: cloudfunctions.functions.update
        methodName: v2.deploymentmanager.deployments.insert
        serviceName: deploymentmanager.googleapis.com
      receiveTimestamp: "2024-01-19 13:47:19.465856238"
      resource:
        labels:
          name: test-vm-deployment
          project_id: panther-threat-research
        type: deployment
      severity: NOTICE
      timestamp: "2024-01-19 13:47:18.279921000"
  - Name: fail
    ExpectedResult: false
    Log:
      protoPayload:
        authorizationInfo:
          - granted: false
            permission: cloudfunctions.functions.update
        methodName: v2.deploymentmanager.deployments.insert
        serviceName: deploymentmanager.googleapis.com
      receiveTimestamp: "2024-01-19 13:47:19.465856238"
      resource:
        labels:
          name: test-vm-deployment
          project_id: panther-threat-research
        type: deployment
      severity: NOTICE
      timestamp: "2024-01-19 13:47:18.279921000"

Detection logic

Condition

protoPayload.authorizationInfo is_not_null
protoPayload.authorizationInfo array_any

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`protoPayload.authorizationInfo`	is_not_null	(no value, null check)

Output fields

Fields the rule emits when it matches. Chronicle authors list these in the outcome block; they appear on the detection and $risk_score drives alerting. Sentinel / Defender XDR rules build them up through project / summarize / extend stages. Sentinel maps these into alert fields via entityMappings and customDetails; Defender XDR custom detections surface them as alert fields directly.

Field	Source
`project`	`resource.labels.project_id`
`principal`	`protoPayload.authenticationInfo.principalEmail`
`caller_ip`	`protoPayload.requestMetadata.callerIP`
`methodName`	`protoPayload.methodName`
`resourceName`	`protoPayload.resourceName`
`serviceName`	`protoPayload.serviceName`

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)