Add a gpg_key module and a 'pass' key for password-store

Manage OpenPGP keys in the gpg engine from Terraform using the new
gpgvaultsecret provider, and create the first key ('pass') for passv.

- Add a gpg_key module wrapping the gpg_key resource; wire it through
  vault_cluster (variable + module, depends_on the mount) and config discovery
  (config.hcl group keyed <backend>/<name>, syd1 terragrunt input), mirroring
  the *_secret_backend_role modules.
- Register the gpg provider in root.hcl (provider block + required_providers,
  v0.1.0 from the terraform-unkin registry), alongside litellm.
- Add config/gpg_key/gpg/pass.yaml: an rsa-4096 key 'pass' in the gpg mount for
  password-store. Private key stays in Vault; clients import the public key and
  delegate decryption to gpg/decrypt/pass.

config/config.hcl

@@ -198,5 +198,18 @@ locals {
       })
       if startswith(file_path, "litellm_secret_backend_role/")
     }
+    gpg_secret_backend = {
+      for file_path, content in local.all_configs :
+      trimsuffix(basename(file_path), ".yaml") => content
+      if startswith(file_path, "gpg_secret_backend/")
+    }
+    gpg_key = {
+      for file_path, content in local.all_configs :
+      trimsuffix(replace(file_path, "gpg_key/", ""), ".yaml") => merge(content, {
+        name    = trimsuffix(basename(file_path), ".yaml")
+        backend = dirname(replace(file_path, "gpg_key/", ""))
+      })
+      if startswith(file_path, "gpg_key/")
+    }
   }
 }

config/gpg_key/gpg/pass.yaml

@@ -0,0 +1,7 @@
+# config/gpg_key/gpg/pass.yaml
+# An OpenPGP key in the gpg engine for password-store (passv). The private key
+# stays in Vault; clients import the exported public key to encrypt and delegate
+# decryption to gpg/decrypt/pass. Key name = "pass", backend = "gpg".
+algorithm: rsa-4096
+identity: "pass <pass@unkin.net>"
+exportable: false

config/gpg_secret_backend/gpg.yaml

@@ -0,0 +1,9 @@
+# config/gpg_secret_backend/gpg.yaml
+# Registers the vault-plugin-secrets-gpg plugin and mounts it at "gpg".
+# The binary is installed on the OpenBao nodes by Puppet
+# (openbao-plugin-secrets-gpg RPM -> /opt/openbao-plugins/vault-plugin-secrets-gpg).
+#
+# sha256 pins the released v0.1.0 binary; bump it in lockstep with any RPM
+# upgrade or OpenBao will refuse to launch the plugin.
+description: "GPG/OpenPGP secrets engine (sign/verify/encrypt/decrypt)"
+sha256: "0e92d7408795688badb55789bc1604e8f1dd4d71998656c7f831991fce9a7b20"

environments/au/syd1/terragrunt.hcl

@@ -70,6 +70,8 @@ inputs = {
   pki_mount_only                 = local.config.pki_mount_only
   litellm_secret_backend         = local.config.litellm_secret_backend
   litellm_secret_backend_role    = local.config.litellm_secret_backend_role
+  gpg_secret_backend             = local.config.gpg_secret_backend
+  gpg_key                        = local.config.gpg_key
 
   # Pass policy maps to vault_cluster module
   policy_auth_map  = local.policies.policy_auth_map

environments/root.hcl

@@ -17,6 +17,12 @@ provider "litellm" {
   address = local.vault_addr
 }
 
+# The gpg secrets engine's keys are managed through its own provider (same Vault
+# server; token falls back to VAULT_TOKEN).
+provider "gpg" {
+  address = local.vault_addr
+}
+
 terraform {
   backend "consul" {
     address = "https://consul.service.consul"
@@ -39,6 +45,10 @@ terraform {
       source  = "artifactapi.k8s.syd1.au.unkin.net/terraform-unkin/litellmvaultsecret"
       version = "0.1.0"
     }
+    gpg = {
+      source  = "artifactapi.k8s.syd1.au.unkin.net/terraform-unkin/gpgvaultsecret"
+      version = "0.1.0"
+    }
   }
 }
 EOF

modules/vault_cluster/main.tf

@@ -334,6 +334,34 @@ module "litellm_secret_backend_role" {
   depends_on = [module.litellm_secret_backend]
 }
 
+module "gpg_secret_backend" {
+  source = "./modules/gpg_secret_backend"
+
+  for_each = var.gpg_secret_backend
+
+  path        = each.key
+  plugin      = each.value.plugin
+  command     = each.value.command
+  sha256      = each.value.sha256
+  description = each.value.description
+}
+
+module "gpg_key" {
+  source = "./modules/gpg_key"
+
+  for_each = var.gpg_key
+
+  backend                = each.value.backend
+  name                   = each.value.name
+  algorithm              = each.value.algorithm
+  identity               = each.value.identity
+  exportable             = each.value.exportable
+  deletion_allowed       = each.value.deletion_allowed
+  min_decryption_version = each.value.min_decryption_version
+
+  depends_on = [module.gpg_secret_backend]
+}
+
 module "vault_policy" {
   source = "./modules/vault_policy"
 

modules/vault_cluster/modules/gpg_key/main.tf

@@ -0,0 +1,12 @@
+# Manages an OpenPGP key inside a gpg secrets engine mount, via the
+# gpgvaultsecret provider. The private key never leaves Vault; consumers use the
+# exported public_key to encrypt and delegate decryption back to the engine.
+resource "gpg_key" "this" {
+  backend                = var.backend
+  name                   = var.name
+  algorithm              = var.algorithm
+  identity               = var.identity
+  exportable             = var.exportable
+  deletion_allowed       = var.deletion_allowed
+  min_decryption_version = var.min_decryption_version
+}

modules/vault_cluster/modules/gpg_key/terraform.tf

@@ -0,0 +1,9 @@
+terraform {
+  required_version = ">= 1.10"
+  required_providers {
+    gpg = {
+      source  = "artifactapi.k8s.syd1.au.unkin.net/terraform-unkin/gpgvaultsecret"
+      version = "0.1.0"
+    }
+  }
+}

modules/vault_cluster/modules/gpg_key/variables.tf

@@ -0,0 +1,39 @@
+variable "backend" {
+  description = "Mount path of the gpg secrets engine (e.g. \"gpg\")"
+  type        = string
+}
+
+variable "name" {
+  description = "Name of the key"
+  type        = string
+}
+
+variable "algorithm" {
+  description = "Key algorithm: rsa-2048, rsa-3072, rsa-4096 or ed25519"
+  type        = string
+  default     = "rsa-3072"
+}
+
+variable "identity" {
+  description = "OpenPGP User ID (defaults to the key name)"
+  type        = string
+  default     = null
+}
+
+variable "exportable" {
+  description = "Allow exporting the private key (enable-only)"
+  type        = bool
+  default     = false
+}
+
+variable "deletion_allowed" {
+  description = "Whether the key may be deleted"
+  type        = bool
+  default     = false
+}
+
+variable "min_decryption_version" {
+  description = "Minimum key version usable for decryption/verification"
+  type        = number
+  default     = null
+}

modules/vault_cluster/modules/gpg_secret_backend/main.tf

@@ -0,0 +1,20 @@
+# Registers the GPG/OpenPGP secrets plugin in the catalog and mounts it. The
+# plugin binary is installed on the OpenBao nodes by Puppet
+# (openbao-plugin-secrets-gpg RPM -> /opt/openbao-plugins/vault-plugin-secrets-gpg);
+# `command` is that filename, resolved relative to the server's plugin_directory.
+#
+# The sha256 is pinned here to the released binary. Puppet installs the RPM
+# floating, so on a plugin upgrade this sha256 must be bumped in lockstep or
+# OpenBao will refuse to launch the plugin.
+resource "vault_plugin" "this" {
+  type    = "secret"
+  name    = var.plugin
+  command = var.command
+  sha256  = var.sha256
+}
+
+resource "vault_mount" "this" {
+  path        = var.path
+  type        = vault_plugin.this.name
+  description = var.description
+}

modules/vault_cluster/modules/gpg_secret_backend/terraform.tf

@@ -0,0 +1,9 @@
+terraform {
+  required_version = ">= 1.10"
+  required_providers {
+    vault = {
+      source  = "hashicorp/vault"
+      version = "5.6.0"
+    }
+  }
+}

modules/vault_cluster/modules/gpg_secret_backend/variables.tf

@@ -0,0 +1,27 @@
+variable "path" {
+  description = "Mount path of the GPG secrets engine (e.g. \"gpg\")"
+  type        = string
+}
+
+variable "plugin" {
+  description = "Name to register the plugin under in the catalog (also the mount type)"
+  type        = string
+  default     = "vault-plugin-secrets-gpg"
+}
+
+variable "command" {
+  description = "Plugin binary filename, relative to the server plugin_directory"
+  type        = string
+  default     = "vault-plugin-secrets-gpg"
+}
+
+variable "sha256" {
+  description = "SHA-256 of the installed plugin binary; must match the on-disk binary or OpenBao rejects it"
+  type        = string
+}
+
+variable "description" {
+  description = "Human-friendly description of the mount"
+  type        = string
+  default     = null
+}

modules/vault_cluster/variables.tf

@@ -315,6 +315,31 @@ variable "litellm_secret_backend_role" {
   default = {}
 }
 
+variable "gpg_secret_backend" {
+  description = "Map of GPG/OpenPGP secret engines to register + mount (path => plugin sha256 + config)"
+  type = map(object({
+    plugin      = optional(string, "vault-plugin-secrets-gpg")
+    command     = optional(string, "vault-plugin-secrets-gpg")
+    sha256      = string
+    description = optional(string)
+  }))
+  default = {}
+}
+
+variable "gpg_key" {
+  description = "Map of OpenPGP keys to manage in a gpg engine mount"
+  type = map(object({
+    name                   = string
+    backend                = string
+    algorithm              = optional(string, "rsa-3072")
+    identity               = optional(string)
+    exportable             = optional(bool, false)
+    deletion_allowed       = optional(bool, false)
+    min_decryption_version = optional(number)
+  }))
+  default = {}
+}
+
 variable "policy_auth_map" {
   description = "Map of auth mounts -> auth roles -> policy names"
   type        = map(map(list(string)))