Merge pull request #317 from HackTricks-wiki/update_Charting_your_way_in_Helm_template_injection_c4c3d85e188cf37f

Charting your way in Helm template injection

Author: carlospolop

src/pentesting-cloud/azure-security/az-privilege-escalation/az-automation-accounts-privesc.md

@@ -314,7 +314,7 @@ sudo nc -nlvp 443
 
 The scheduled task executes the payload, achieving SYSTEM-level privileges.
 
-{{#include ../../../banners/hacktricks-training.md}}
+
 
 
 ### `Microsoft.Automation/automationAccounts/python3Packages/write`, `Microsoft.Automation/automationAccounts/runbooks/write`, `Microsoft.Automation/automationAccounts/runbooks/publish/action`, `Microsoft.Automation/automationAccounts/jobs/write`
@@ -601,3 +601,4 @@ az rest --method GET \
   --url "https://management.azure.com/subscriptions/${SUBSCRIPTION_ID}/resourceGroups/${RESOURCE_GROUP}/providers/Microsoft.Automation/automationAccounts/${AUTOMATION_ACCOUNT}/jobs/${JOB_ID}/streams?api-version=2023-11-01"
 ```
 
+{{#include ../../../banners/hacktricks-training.md}}

src/pentesting-cloud/kubernetes-security/kubernetes-basics.md

@@ -366,6 +366,75 @@ helm search <keyword>
 
 Helm is also a template engine that allows to generate config files with variables:
 
+### Helm `.Values` YAML injection
+
+If a chart inserts **attacker-controlled values** directly into YAML, Helm will **render them as raw YAML content** unless the template explicitly quotes, converts, or validates them. This is especially dangerous in **GitOps** environments (for example with **ArgoCD**) where developers are only allowed to modify `values.yaml` and the chart is assumed to be trusted.
+
+**Typical vulnerable patterns:**
+
+```yaml
+spec:
+  replicas: {{ .Values.replicaCount }}
+...
+image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
+```
+
+If an attacker can control those values, they can abuse YAML multiline scalars (`|` or `|-`) to **break the expected context**, inject **new fields** at the right indentation level, and even inject **new YAML documents** with `---`.
+
+### Exploitation ideas
+
+- **Field injection** from scalar-looking values:
+
+```yaml
+replicaCount: |
+  3
+    injectedAttribute: true
+```
+
+This can transform a numeric-looking field into additional manifest attributes.
+
+- **Quoted-context breakout** to inject container attributes such as `command`, `args`, or `securityContext`:
+
+```yaml
+image:
+  tag: |-
+    1.0.0"
+              securityContext:
+                privileged: true
+              command: ["/bin/sh", "-c"]
+              args: ["id"]
+```
+
+- **Arbitrary object injection** by creating extra YAML documents with `---`, which may create resources such as `Namespace`, `Pod`, `Role`, `ClusterRole`, `RoleBinding`, or `ClusterRoleBinding` if the Helm/ArgoCD service account is allowed to create them. This connects directly with [RBAC abuse](kubernetes-role-based-access-control-rbac.md), [abusing dangerous roles](abusing-roles-clusterroles-in-kubernetes/), and [namespace pivoting](kubernetes-namespace-escalation.md).
+
+> [!WARNING]
+> Control over `values.yaml` in a vulnerable chart can become **arbitrary workload creation**, **command execution inside Pods**, **privileged Pod deployment**, and sometimes **cluster compromise**.
+
+### Helm v3 vs Helm v4
+
+- **Helm v3** may accept injected unknown fields as long as the final rendered output is valid YAML.
+- **Helm v4** uses **Server-Side Apply** by default and rejects several invalid fields against the Kubernetes schema.
+- However, **Helm v4 does not fully solve the problem**: an attacker may still inject **valid resources first** and append a final invalid object only to absorb the broken context, so previously injected valid resources are still created.
+
+### Defensive patterns
+
+Treat every Helm value as **untrusted input**:
+
+```yaml
+image: {{ printf "%s:%s" .Values.image.repository .Values.image.tag | quote }}
+replicas: {{ .Values.replicaCount | int }}
+{{- if not (regexMatch "^(latest|1\.1|dev)$" .Values.image.tag) }}
+{{- fail "invalid image.tag" }}
+{{- end }}
+```
+
+Additional hardening:
+
+- Use `values.schema.json` to enforce **types**, **required keys**, and **regex patterns** during `helm template`, `helm install`, `helm upgrade`, and `helm lint`.
+- In **ArgoCD**, restrict the kinds an application can create via `AppProject` rules such as `clusterResourceWhitelist`, and prefer **namespace-scoped** ArgoCD permissions whenever possible.
+- Use **ValidatingAdmissionPolicy** / **ValidatingAdmissionPolicyBinding**, Kyverno, or Gatekeeper rules to block dangerous outputs such as **privileged Pods** even if rendering was compromised.
+- If a target namespace is protected by Pod Security controls, check whether the attacker can inject a **new namespace** where those controls do not apply, then use the new workload for [pod escape](abusing-roles-clusterroles-in-kubernetes/pod-escape-privileges.md) or further [post-compromise attacks from inside a pod](attacking-kubernetes-from-inside-a-pod.md).
+
 ## Kubernetes secrets
 
 A **Secret** is an object that **contains sensitive data** such as a password, a token or a key. Such information might otherwise be put in a Pod specification or in an image. Users can create Secrets and the system also creates Secrets. The name of a Secret object must be a valid **DNS subdomain name**. Read here [the official documentation](https://kubernetes.io/docs/concepts/configuration/secret/).
@@ -566,12 +635,13 @@ https://sickrov.github.io/
 https://www.youtube.com/watch?v=X48VuDVv0do
 {{#endref}}
 
-{{#ref}}
-https://kubernetes.io/docs/concepts/storage/volumes/#image
-{{#endref}}
-
-{{#ref}}
-https://kubernetes.io/docs/tasks/configure-pod-container/image-volumes/
-{{#endref}}
+- [Charting your way in: Helm template injection](https://synacktiv.com/en/publications/charting-your-way-in-helm-template-injection.html)
+- [Helm template functions and pipelines](https://helm.sh/docs/chart_template_guide/functions_and_pipelines/)
+- [Helm chart schema files (`values.schema.json`)](https://helm.sh/docs/topics/charts/#schema-files)
+- [Argo CD projects (`AppProject` restrictions)](https://argo-cd.readthedocs.io/en/latest/user-guide/projects/)
+- [Argo CD multiple sources / external Helm value files](https://argo-cd.readthedocs.io/en/latest/user-guide/multiple_sources/#helm-value-files-from-external-git-repository)
+- [Kubernetes ValidatingAdmissionPolicy](https://kubernetes.io/docs/reference/access-authn-authz/validating-admission-policy/)
+- [https://kubernetes.io/docs/concepts/storage/volumes/#image](https://kubernetes.io/docs/concepts/storage/volumes/#image)
+- [https://kubernetes.io/docs/tasks/configure-pod-container/image-volumes/](https://kubernetes.io/docs/tasks/configure-pod-container/image-volumes/)
 
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