voucher-vault: strict values.schema.json and null-safe hardening

No ingress gate: this chart already gates its Ingress correctly. Two
changes plus one guard that the existing gate turned out to need.

1. values.schema.json (#68): additionalProperties: false on every
   chart-owned object level. Lists that go verbatim into the pod spec
   (ports, storage.volumes, storage.volumeMounts) stay open.

2. Null-safety for hardening, probes and resources (#99). Two specifics
   of this chart:

   - The probes were wrapped in "if" guards, so an erased probe block did
     not render "livenessProbe: null" - it removed the probe entirely and
     silently. The guards are gone; an empty block now means chart
     defaults, so the workload keeps its probes.
   - The rebuilt probes keep the Host: 127.0.0.1 header. Django's
     ALLOWED_HOSTS only accepts 127.0.0.1 and the configured DOMAIN, so a
     probe without it would get 400 and the pod would never be ready.

3. ingress.domain is required() where it is read. The dependency lives in
   values.yaml, not in a template: the DOMAIN env entry is a tpl string
   feeding Django's ALLOWED_HOSTS. With the existing gate and no domain
   the app rendered DOMAIN: "" and answered 400 to every real request -
   silently, and already before this change. It now fails loudly.

Apart from an added comment, the rendered manifest is unchanged.

voucher-vault/Chart.yaml

@@ -5,7 +5,7 @@ icon: https://raw.githubusercontent.com/l4rm4nd/VoucherVault/main/myapp/static/a
 
 type: application
 
-version: 4.0.0+up1.30.1
+version: 5.0.0+up1.30.1
 appVersion: "1.30.1"
 
 maintainers:

voucher-vault/templates/_helpers.tpl

@@ -114,3 +114,164 @@ template-chart is the reference implementation.
 1
 {{- end -}}
 {{- end -}}
+
+{{/*
+Merge a user-supplied values sub-tree onto a dict of chart defaults so that a
+null / empty override falls back to the defaults instead of erasing them.
+
+Input: dict "defaults" <dict> "given" <dict|nil> "path" <string, optional
+values path used in error messages>. Output: YAML of the merged dict (consume
+it with fromYaml).
+
+Why this exists (issue #99): Helm merges values maps recursively, but an
+override key written without children — e.g. a leftover
+
+  securityContext:
+
+after deleting its last remaining sub-key — is YAML null. Where the chart
+defines a default, Helm treats that null as a deletion of the default; the
+template then renders "securityContext: null": no readOnlyRootFilesystem, no
+dropped capabilities, no allowPrivilegeEscalation: false. The workload starts
+and reports healthy while being unhardened, so nothing points at the mistake.
+The same shape erases a probe or the resources block. This helper defines the
+opposite semantics: an empty block means "chart defaults apply".
+
+Rules:
+  - a nil "given" is treated as an empty dict (all defaults apply).
+  - a key whose override value is null keeps the default (nulls never delete).
+  - a key present in both as a map is merged recursively, so a partially
+    filled block only overrides the keys it actually sets.
+  - a scalar override for a key the defaults define as a map is rejected with
+    a message naming the values path, instead of failing later with a template
+    field error.
+  - any other set value wins as given, including an explicit false or 0 —
+    Helm's "default" and sprig's "mergeOverwrite" would both swallow those
+    zero values, hence the explicit kindIs "invalid" nil check.
+  - keys only present in the override are passed through unchanged.
+
+NOTE: like the helpers above, this is duplicated into every chart's
+templates/_helpers.tpl with the chart's name as define prefix, because charts
+in this repo deliberately have no dependencies.
+*/}}
+{{- define "voucher-vault.defaultedDict" -}}
+{{- $defaults := .defaults | default dict -}}
+{{- $given := .given -}}
+{{- $path := .path | default "value" -}}
+{{- if kindIs "invalid" $given -}}
+{{- $given = dict -}}
+{{- end -}}
+{{- if not (kindIs "map" $given) -}}
+{{- fail (printf "%s must be a mapping or null, got %s (%v)" $path (kindOf $given) $given) -}}
+{{- end -}}
+{{- $out := deepCopy $defaults -}}
+{{- range $key, $value := $given -}}
+{{- if not (kindIs "invalid" $value) -}}
+{{- $default := index $defaults $key -}}
+{{- if and (kindIs "map" $value) (kindIs "map" $default) -}}
+{{- $_ := set $out $key (fromYaml (include "voucher-vault.defaultedDict" (dict "defaults" $default "given" $value "path" (printf "%s.%s" $path $key)))) -}}
+{{- else if kindIs "map" $default -}}
+{{- fail (printf "%s.%s must be a mapping or null, got %s (%v)" $path $key (kindOf $value) $value) -}}
+{{- else -}}
+{{- $_ := set $out $key $value -}}
+{{- end -}}
+{{- end -}}
+{{- end -}}
+{{- toYaml $out -}}
+{{- end -}}
+
+{{/*
+Pick one sub-block out of a values block that may itself be null.
+
+Input: dict "block" <dict|nil> "key" <string> "path" <string>.
+Returns YAML of dict "value" <the sub-block, may be nil>, after rejecting a
+non-mapping block with a message that names the values path. Needed because
+".Values.voucherVault.securityContext" can itself be erased.
+*/}}
+{{- define "voucher-vault.subBlock" -}}
+{{- $block := .block -}}
+{{- if kindIs "invalid" $block -}}
+{{- $block = dict -}}
+{{- end -}}
+{{- if not (kindIs "map" $block) -}}
+{{- fail (printf "%s must be a mapping or null, got %s (%v)" .path (kindOf $block) $block) -}}
+{{- end -}}
+{{- toYaml (dict "value" (index $block .key)) -}}
+{{- end -}}
+
+{{/*
+The effective security contexts, probes and resources (issue #99).
+
+The defaults below MUST stay in sync with the corresponding blocks in
+values.yaml, which stays the documented, user-facing place for them; this copy
+is only the fallback for the case where an override has erased the block.
+
+The probes carry a Host header of 127.0.0.1: Django's ALLOWED_HOSTS only
+accepts 127.0.0.1 and the configured DOMAIN, so probing with the default Host
+(the pod IP) would always return 400. A rebuilt default probe must keep that
+header, otherwise the pod never becomes ready.
+*/}}
+{{- define "voucher-vault.podSecurityContext" -}}
+{{- $given := (fromYaml (include "voucher-vault.subBlock" (dict "block" . "key" "pod" "path" "voucherVault.securityContext"))).value -}}
+{{- $defaults := dict
+      "runAsNonRoot" true
+      "runAsUser" 33
+      "runAsGroup" 33
+      "fsGroup" 33
+      "fsGroupChangePolicy" "Always" -}}
+{{- include "voucher-vault.defaultedDict" (dict "defaults" $defaults "given" $given "path" "voucherVault.securityContext.pod") -}}
+{{- end -}}
+
+{{- define "voucher-vault.containerSecurityContext" -}}
+{{- $given := (fromYaml (include "voucher-vault.subBlock" (dict "block" . "key" "container" "path" "voucherVault.securityContext"))).value -}}
+{{- $defaults := dict
+      "allowPrivilegeEscalation" false
+      "readOnlyRootFilesystem" true
+      "runAsNonRoot" true
+      "capabilities" (dict "drop" (list "ALL")) -}}
+{{- include "voucher-vault.defaultedDict" (dict "defaults" $defaults "given" $given "path" "voucherVault.securityContext.container") -}}
+{{- end -}}
+
+{{- define "voucher-vault.probeHttpGet" -}}
+{{- dict "path" "/" "port" "http" "httpHeaders" (list (dict "name" "Host" "value" "127.0.0.1")) | toYaml -}}
+{{- end -}}
+
+{{- define "voucher-vault.livenessProbe" -}}
+{{- $defaults := dict
+      "httpGet" (fromYaml (include "voucher-vault.probeHttpGet" .))
+      "periodSeconds" 10
+      "timeoutSeconds" 5
+      "failureThreshold" 3 -}}
+{{- include "voucher-vault.defaultedDict" (dict "defaults" $defaults "given" . "path" "voucherVault.livenessProbe") -}}
+{{- end -}}
+
+{{- define "voucher-vault.readinessProbe" -}}
+{{- $defaults := dict
+      "httpGet" (fromYaml (include "voucher-vault.probeHttpGet" .))
+      "periodSeconds" 10
+      "timeoutSeconds" 5
+      "failureThreshold" 3 -}}
+{{- include "voucher-vault.defaultedDict" (dict "defaults" $defaults "given" . "path" "voucherVault.readinessProbe") -}}
+{{- end -}}
+
+{{- define "voucher-vault.startupProbe" -}}
+{{- $defaults := dict
+      "httpGet" (fromYaml (include "voucher-vault.probeHttpGet" .))
+      "periodSeconds" 5
+      "timeoutSeconds" 5
+      "failureThreshold" 30 -}}
+{{- include "voucher-vault.defaultedDict" (dict "defaults" $defaults "given" . "path" "voucherVault.startupProbe") -}}
+{{- end -}}
+
+{{/*
+The effective resources block, fed into the resources helper above so that an
+erased "resources:" still yields the chart's requests and computed limits.
+The ephemeral-storage request matters here beyond the usual reason: the
+static-files emptyDir holds ~90Mi of assets and counts toward it.
+*/}}
+{{- define "voucher-vault.effectiveResources" -}}
+{{- $defaults := dict
+      "limitFactor" 3
+      "requests" (dict "cpu" 0.1 "memory" "256Mi" "ephemeral-storage" "128Mi") -}}
+{{- $merged := fromYaml (include "voucher-vault.defaultedDict" (dict "defaults" $defaults "given" . "path" "voucherVault.resources")) -}}
+{{- include "voucher-vault.resources" $merged -}}
+{{- end -}}

voucher-vault/templates/voucher-vault.sfs.yaml

@@ -18,7 +18,7 @@ spec:
     spec:
       automountServiceAccountToken: false
       securityContext:
-        {{- toYaml .Values.voucherVault.securityContext.pod | nindent 8 }}
+        {{- include "voucher-vault.podSecurityContext" .Values.voucherVault.securityContext | nindent 8 }}
       initContainers:
         # STATIC_ROOT (/opt/app/myapp/static) doubles as the app's own static
         # source directory, so it cannot simply be shadowed by an empty
@@ -33,7 +33,7 @@ spec:
           # on the mountpoint itself, which the non-root uid may not own.
           command: ["sh", "-c", "cp -a /opt/app/myapp/static/* /static-seed/"]
           securityContext:
-            {{- toYaml .Values.voucherVault.securityContext.container | nindent 12 }}
+            {{- include "voucher-vault.containerSecurityContext" .Values.voucherVault.securityContext | nindent 12 }}
           volumeMounts:
             - name: static-files
               mountPath: /static-seed
@@ -73,22 +73,19 @@ spec:
             {{- end }}
           ports:
             {{- toYaml .Values.voucherVault.ports | nindent 12 }}
-          {{- if .Values.voucherVault.livenessProbe }}
+          # No "if" guards here any more: an erased probe block used to omit the
+          # probe entirely and silently. It now falls back to the chart
+          # defaults (#99), so the workload keeps its probes.
           livenessProbe:
-            {{- toYaml .Values.voucherVault.livenessProbe | nindent 12 }}
+            {{- include "voucher-vault.livenessProbe" .Values.voucherVault.livenessProbe | nindent 12 }}
-          {{- end }}
-          {{- if .Values.voucherVault.readinessProbe }}
           readinessProbe:
-            {{- toYaml .Values.voucherVault.readinessProbe | nindent 12 }}
+            {{- include "voucher-vault.readinessProbe" .Values.voucherVault.readinessProbe | nindent 12 }}
-          {{- end }}
-          {{- if .Values.voucherVault.startupProbe }}
           startupProbe:
-            {{- toYaml .Values.voucherVault.startupProbe | nindent 12 }}
+            {{- include "voucher-vault.startupProbe" .Values.voucherVault.startupProbe | nindent 12 }}
-          {{- end }}
           resources:
-            {{- include "voucher-vault.resources" .Values.voucherVault.resources | nindent 12 }}
+            {{- include "voucher-vault.effectiveResources" .Values.voucherVault.resources | nindent 12 }}
           securityContext:
-            {{- toYaml .Values.voucherVault.securityContext.container | nindent 12 }}
+            {{- include "voucher-vault.containerSecurityContext" .Values.voucherVault.securityContext | nindent 12 }}
           volumeMounts:
             # Writable emptyDirs over the paths the image writes at runtime,
             # so the root filesystem can stay read-only (see securityContext

voucher-vault/values.schema.json

@@ -0,0 +1,210 @@
+{
+  "$schema": "https://json-schema.org/draft-07/schema#",
+  "title": "voucher-vault values",
+  "description": "Strict values schema (issue #68). additionalProperties is false on every chart-owned object level, so a key that the chart does not read is rejected at render time instead of being silently ignored. The only objects that stay open are the ones passed verbatim into the Kubernetes pod spec (probes, security contexts, ports, volumes, global) - the chart does not interpret their contents, so it cannot judge which keys are meaningful. The hardening, probe and resources blocks additionally accept null, because an erased block falls back to the chart defaults (issue #99).",
+  "type": "object",
+  "additionalProperties": false,
+  "properties": {
+    "global": {
+      "description": "Helm's conventional cross-chart values. Unused by this chart, kept open so an umbrella install cannot break on it.",
+      "type": "object"
+    },
+    "scaleDown": {
+      "type": "boolean"
+    },
+    "secrets": {
+      "type": "object",
+      "additionalProperties": false,
+      "properties": {
+        "voucherVaultSecretRef": {
+          "type": ["string", "null"]
+        },
+        "oidcSecretRef": {
+          "type": ["string", "null"]
+        },
+        "databaseSecretRef": {
+          "type": ["string", "null"]
+        }
+      }
+    },
+    "voucherVault": {
+      "type": "object",
+      "additionalProperties": false,
+      "properties": {
+        "replicas": {
+          "type": "integer",
+          "minimum": 0
+        },
+        "resources": {
+          "$ref": "#/definitions/resources"
+        },
+        "livenessProbe": {
+          "$ref": "#/definitions/probe"
+        },
+        "readinessProbe": {
+          "$ref": "#/definitions/probe"
+        },
+        "startupProbe": {
+          "$ref": "#/definitions/probe"
+        },
+        "securityContext": {
+          "$ref": "#/definitions/securityContext"
+        },
+        "ports": {
+          "description": "Rendered verbatim as the container's ports list; kept open because the chart does not interpret the entries.",
+          "type": ["array", "null"]
+        },
+        "env": {
+          "description": "The container's full env list (not merely additive here). Entries are rendered through tpl, so values may contain Helm templating.",
+          "$ref": "#/definitions/env"
+        },
+        "storage": {
+          "description": "Volumes and volumeMounts of the workload, rendered verbatim into the pod spec; kept open because the chart does not interpret the entries.",
+          "type": "object",
+          "additionalProperties": false,
+          "properties": {
+            "volumes": {
+              "type": ["array", "null"]
+            },
+            "volumeMounts": {
+              "type": ["array", "null"]
+            }
+          }
+        }
+      }
+    },
+    "storage": {
+      "description": "The data PVC. Not null-safe on purpose: an erased block yields an invalid PVC rather than a silently degraded workload.",
+      "type": "object",
+      "additionalProperties": false,
+      "properties": {
+        "amount": {
+          "type": ["string", "null"]
+        },
+        "storageClass": {
+          "type": ["string", "null"]
+        }
+      }
+    },
+    "ingress": {
+      "type": "object",
+      "additionalProperties": false,
+      "properties": {
+        "enabled": {
+          "description": "Gates the whole Ingress template. false omits the Ingress and makes clusterIssuer unnecessary - but NOT domain, which is also Django's ALLOWED_HOSTS entry.",
+          "type": "boolean"
+        },
+        "clusterIssuer": {
+          "type": ["string", "null"]
+        },
+        "domain": {
+          "type": ["string", "null"]
+        },
+        "className": {
+          "type": ["string", "null"]
+        },
+        "annotations": {
+          "description": "Extra Ingress annotations, merged with the cert-manager annotation the chart always sets. Free-form keys by nature.",
+          "type": "object"
+        }
+      }
+    }
+  },
+  "definitions": {
+    "resources": {
+      "description": "May be null / empty: the chart then falls back to its default requests and computed limits (issue #99) instead of rendering a container without resource accounting.",
+      "type": ["object", "null"],
+      "additionalProperties": false,
+      "properties": {
+        "limitFactor": {
+          "type": "number",
+          "exclusiveMinimum": 0
+        },
+        "requests": {
+          "$ref": "#/definitions/resourceList"
+        },
+        "limits": {
+          "$ref": "#/definitions/resourceList"
+        }
+      }
+    },
+    "resourceList": {
+      "type": ["object", "null"],
+      "additionalProperties": false,
+      "properties": {
+        "cpu": {
+          "type": ["string", "number", "null"]
+        },
+        "memory": {
+          "type": ["string", "number", "null"]
+        },
+        "ephemeral-storage": {
+          "type": ["string", "number", "null"]
+        },
+        "ephemeralStorage": {
+          "type": ["string", "number", "null"]
+        }
+      }
+    },
+    "env": {
+      "type": ["array", "null"],
+      "items": {
+        "type": "object",
+        "additionalProperties": false,
+        "required": ["name"],
+        "properties": {
+          "name": {
+            "type": "string"
+          },
+          "value": {
+            "type": ["string", "number", "boolean"]
+          },
+          "valueFrom": {
+            "type": "object",
+            "additionalProperties": false,
+            "properties": {
+              "secretKeyRef": {
+                "$ref": "#/definitions/keyRef"
+              },
+              "configMapKeyRef": {
+                "$ref": "#/definitions/keyRef"
+              }
+            }
+          }
+        }
+      }
+    },
+    "keyRef": {
+      "type": "object",
+      "additionalProperties": false,
+      "required": ["name", "key"],
+      "properties": {
+        "name": {
+          "type": "string"
+        },
+        "key": {
+          "type": "string"
+        }
+      }
+    },
+    "securityContext": {
+      "description": "May be null / empty at any level: the chart then falls back to its hardening defaults (issue #99) instead of rendering an unhardened workload.",
+      "type": ["object", "null"],
+      "additionalProperties": false,
+      "properties": {
+        "pod": {
+          "description": "Merged onto the chart's pod hardening defaults and rendered as the pod's securityContext; kept open because the chart does not interpret the individual fields.",
+          "type": ["object", "null"]
+        },
+        "container": {
+          "description": "Merged onto the chart's container hardening defaults and rendered as the securityContext of both the init container and the app container; kept open because the chart does not interpret the individual fields.",
+          "type": ["object", "null"]
+        }
+      }
+    },
+    "probe": {
+      "description": "Merged onto the chart's probe defaults and rendered as a container probe; kept open because the chart does not interpret the individual fields. May be null / empty, which means the defaults apply (issue #99) rather than the probe disappearing.",
+      "type": ["object", "null"]
+    }
+  }
+}

voucher-vault/values.yaml

@@ -86,8 +86,12 @@ voucherVault:
       protocol: TCP
       name: http
   env:
+    # ingress.domain is not a pure Ingress value: Django's ALLOWED_HOSTS only
+    # accepts 127.0.0.1 and this DOMAIN, so an empty value makes the app answer
+    # 400 to every real request. It therefore stays required even when the
+    # Ingress is switched off via ingress.enabled.
     - name: DOMAIN
-      value: "{{ .Values.ingress.domain }}"
+      value: '{{ required "A Domain/Host must be provided (ingress.domain)" .Values.ingress.domain }}'
     - name: SECURE_COOKIES
       value: "True"
     - name: SESSION_COOKIE_AGE
@@ -196,6 +200,9 @@ storage:
   storageClass: null
 
 ingress:
+  # Set to false to omit the Ingress entirely. Note that ingress.domain stays
+  # required even then: it is also Django's ALLOWED_HOSTS entry (the DOMAIN env
+  # above), not just the Ingress host. Only clusterIssuer becomes unnecessary.
   enabled: true
   clusterIssuer: null
   domain: null