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