561 lines
18 KiB
Markdown
561 lines
18 KiB
Markdown
# Phase 4d: Vault Bootstrap Integration - Implementation Summary
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## Overview
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Phase 4d implements automatic Vault/OpenBao integration for new NixOS hosts, enabling:
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- Zero-touch secret provisioning on first boot
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- Automatic AppRole authentication
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- Runtime secret fetching with caching
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- Periodic secret rotation
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**Key principle**: Existing sops-nix infrastructure remains unchanged. This is new infrastructure running in parallel.
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## Architecture
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### Component Diagram
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```
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┌─────────────────────────────────────────────────────────────┐
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│ Developer Workstation │
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│ │
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│ create-host --hostname myhost --ip 10.69.13.x/24 │
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│ │ │
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│ ├─> Generate host configs (hosts/myhost/) │
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│ ├─> Update flake.nix │
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│ ├─> Update terraform/vms.tf │
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│ ├─> Generate terraform/vault/hosts-generated.tf │
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│ ├─> Apply Vault Terraform (create AppRole) │
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│ └─> Generate wrapped token (24h TTL) ───┐ │
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│ │ │
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└───────────────────────────────────────────────┼────────────┘
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│
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┌───────────────────────────┘
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│ Wrapped Token
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│ (single-use, 24h expiry)
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↓
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┌─────────────────────────────────────────────────────────────┐
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│ Cloud-init (VM Provisioning) │
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│ │
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│ /etc/environment: │
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│ VAULT_ADDR=https://vault01.home.2rjus.net:8200 │
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│ VAULT_WRAPPED_TOKEN=hvs.CAES... │
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│ VAULT_SKIP_VERIFY=1 │
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└─────────────────────────────────────────────────────────────┘
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│
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↓
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┌─────────────────────────────────────────────────────────────┐
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│ Bootstrap Service (First Boot) │
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│ │
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│ 1. Read VAULT_WRAPPED_TOKEN from environment │
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│ 2. POST /v1/sys/wrapping/unwrap │
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│ 3. Extract role_id + secret_id │
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│ 4. Store in /var/lib/vault/approle/ │
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│ ├─ role-id (600 permissions) │
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│ └─ secret-id (600 permissions) │
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│ 5. Continue with nixos-rebuild boot │
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└─────────────────────────────────────────────────────────────┘
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│
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↓
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┌─────────────────────────────────────────────────────────────┐
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│ Runtime (Service Starts) │
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│ │
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│ vault-secret-<name>.service (ExecStartPre) │
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│ │ │
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│ ├─> vault-fetch <secret-path> <output-dir> │
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│ │ │ │
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│ │ ├─> Read role_id + secret_id │
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│ │ ├─> POST /v1/auth/approle/login → token │
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│ │ ├─> GET /v1/secret/data/<path> → secrets │
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│ │ ├─> Write /run/secrets/<name>/password │
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│ │ ├─> Write /run/secrets/<name>/api_key │
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│ │ └─> Cache to /var/lib/vault/cache/<name>/ │
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│ │ │
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│ └─> chown/chmod secret files │
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│ │
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│ myservice.service │
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│ └─> Reads secrets from /run/secrets/<name>/ │
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└─────────────────────────────────────────────────────────────┘
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```
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### Data Flow
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1. **Provisioning Time** (Developer → Vault):
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- create-host generates AppRole configuration
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- Terraform creates AppRole + policy in Vault
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- Vault generates wrapped token containing role_id + secret_id
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- Wrapped token stored in terraform/vms.tf
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2. **Bootstrap Time** (Cloud-init → VM):
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- Cloud-init injects wrapped token via /etc/environment
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- Bootstrap service unwraps token (single-use operation)
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- Stores unwrapped credentials persistently
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3. **Runtime** (Service → Vault):
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- Service starts
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- ExecStartPre hook calls vault-fetch
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- vault-fetch authenticates using stored credentials
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- Fetches secrets and caches them
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- Service reads secrets from filesystem
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## Implementation Details
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### 1. vault-fetch Helper (`scripts/vault-fetch/`)
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**Purpose**: Fetch secrets from Vault and write to filesystem
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**Features**:
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- Reads AppRole credentials from `/var/lib/vault/approle/`
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- Authenticates to Vault (fresh token each time)
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- Fetches secret from KV v2 engine
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- Writes individual files per secret key
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- Updates cache for fallback
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- Gracefully degrades to cache if Vault unreachable
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**Usage**:
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```bash
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vault-fetch hosts/monitoring01/grafana /run/secrets/grafana
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```
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**Environment Variables**:
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- `VAULT_ADDR`: Vault server (default: https://vault01.home.2rjus.net:8200)
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- `VAULT_SKIP_VERIFY`: Skip TLS verification (default: 1)
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**Error Handling**:
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- Vault unreachable → Use cache (log warning)
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- Invalid credentials → Fail with clear error
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- No cache + unreachable → Fail with error
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### 2. NixOS Module (`system/vault-secrets.nix`)
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**Purpose**: Declarative Vault secret management for NixOS services
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**Configuration Options**:
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```nix
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vault.enable = true; # Enable Vault integration
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vault.secrets.<name> = {
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secretPath = "hosts/monitoring01/grafana"; # Path in Vault
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outputDir = "/run/secrets/grafana"; # Where to write secrets
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cacheDir = "/var/lib/vault/cache/grafana"; # Cache location
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owner = "grafana"; # File owner
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group = "grafana"; # File group
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mode = "0400"; # Permissions
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services = [ "grafana" ]; # Dependent services
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restartTrigger = true; # Enable periodic rotation
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restartInterval = "daily"; # Rotation schedule
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};
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```
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**Module Behavior**:
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1. **Fetch Service**: Creates `vault-secret-<name>.service`
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- Runs on boot and before dependent services
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- Calls vault-fetch to populate secrets
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- Sets ownership and permissions
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2. **Rotation Timer**: Optionally creates `vault-secret-rotate-<name>.timer`
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- Scheduled restarts for secret rotation
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- Automatically excluded for critical services
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- Configurable interval (daily, weekly, monthly)
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3. **Critical Service Protection**:
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```nix
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vault.criticalServices = [ "bind" "openbao" "step-ca" ];
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```
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Services in this list never get auto-restart timers
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### 3. create-host Tool Updates
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**New Functionality**:
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1. **Vault Terraform Generation** (`generators.py`):
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- Creates/updates `terraform/vault/hosts-generated.tf`
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- Adds host policy granting access to `secret/data/hosts/<hostname>/*`
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- Adds AppRole configuration
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- Idempotent (safe to re-run)
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2. **Wrapped Token Generation** (`vault_helper.py`):
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- Applies Vault Terraform to create AppRole
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- Reads role_id from Vault
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- Generates secret_id
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- Wraps credentials in cubbyhole token (24h TTL, single-use)
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- Returns wrapped token
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3. **VM Configuration Update** (`manipulators.py`):
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- Adds `vault_wrapped_token` field to VM in vms.tf
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- Preserves other VM settings
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**New CLI Options**:
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```bash
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create-host --hostname myhost --ip 10.69.13.x/24
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# Full workflow with Vault integration
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create-host --hostname myhost --skip-vault
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# Create host without Vault (legacy behavior)
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create-host --hostname myhost --force
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# Regenerate everything including new wrapped token
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```
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**Dependencies Added**:
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- `hvac`: Python Vault client library
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### 4. Bootstrap Service Updates
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**New Behavior** (`hosts/template2/bootstrap.nix`):
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```bash
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# Check for wrapped token
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if [ -n "$VAULT_WRAPPED_TOKEN" ]; then
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# Unwrap to get credentials
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curl -X POST \
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-H "X-Vault-Token: $VAULT_WRAPPED_TOKEN" \
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$VAULT_ADDR/v1/sys/wrapping/unwrap
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# Store role_id and secret_id
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mkdir -p /var/lib/vault/approle
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echo "$ROLE_ID" > /var/lib/vault/approle/role-id
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echo "$SECRET_ID" > /var/lib/vault/approle/secret-id
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chmod 600 /var/lib/vault/approle/*
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# Continue with bootstrap...
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fi
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```
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**Error Handling**:
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- Token already used → Log error, continue bootstrap
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- Token expired → Log error, continue bootstrap
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- Vault unreachable → Log warning, continue bootstrap
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- **Never fails bootstrap** - host can still run without Vault
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### 5. Cloud-init Configuration
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**Updates** (`terraform/cloud-init.tf`):
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```hcl
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write_files:
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- path: /etc/environment
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content: |
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VAULT_ADDR=https://vault01.home.2rjus.net:8200
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VAULT_WRAPPED_TOKEN=${vault_wrapped_token}
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VAULT_SKIP_VERIFY=1
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```
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**VM Configuration** (`terraform/vms.tf`):
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```hcl
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locals {
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vms = {
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"myhost" = {
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ip = "10.69.13.x/24"
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vault_wrapped_token = "hvs.CAESIBw..." # Added by create-host
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}
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}
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}
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```
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### 6. Vault Terraform Structure
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**Generated Hosts File** (`terraform/vault/hosts-generated.tf`):
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```hcl
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locals {
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generated_host_policies = {
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"myhost" = {
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paths = [
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"secret/data/hosts/myhost/*",
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]
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}
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}
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}
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resource "vault_policy" "generated_host_policies" {
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for_each = local.generated_host_policies
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name = "host-${each.key}"
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policy = <<-EOT
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path "secret/data/hosts/${each.key}/*" {
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capabilities = ["read", "list"]
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}
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EOT
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}
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resource "vault_approle_auth_backend_role" "generated_hosts" {
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for_each = local.generated_host_policies
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backend = vault_auth_backend.approle.path
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role_name = each.key
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token_policies = ["host-${each.key}"]
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secret_id_ttl = 0 # Never expire
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token_ttl = 3600 # 1 hour tokens
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}
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```
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**Separation of Concerns**:
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- `approle.tf`: Manual host configurations (ha1, monitoring01)
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- `hosts-generated.tf`: Auto-generated configurations
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- `secrets.tf`: Secret definitions (manual)
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- `pki.tf`: PKI infrastructure
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## Security Model
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### Credential Distribution
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**Wrapped Token Security**:
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- **Single-use**: Can only be unwrapped once
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- **Time-limited**: 24h TTL
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- **Safe in git**: Even if leaked, expires quickly
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- **Standard Vault pattern**: Built-in Vault feature
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**Why wrapped tokens are secure**:
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```
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Developer commits wrapped token to git
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↓
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Attacker finds token in git history
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↓
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Attacker tries to use token
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↓
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❌ Token already used (unwrapped during bootstrap)
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↓
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❌ OR: Token expired (>24h old)
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```
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### AppRole Credentials
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**Storage**:
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- Location: `/var/lib/vault/approle/`
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- Permissions: `600 (root:root)`
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- Persistence: Survives reboots
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**Security Properties**:
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- `role_id`: Non-sensitive (like username)
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- `secret_id`: Sensitive (like password)
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- `secret_id_ttl = 0`: Never expires (simplicity vs rotation tradeoff)
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- Tokens: Ephemeral (1h TTL, not cached)
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**Attack Scenarios**:
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1. **Attacker gets root on host**:
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- Can read AppRole credentials
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- Can only access that host's secrets
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- Cannot access other hosts' secrets (policy restriction)
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- ✅ Blast radius limited to single host
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2. **Attacker intercepts wrapped token**:
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- Single-use: Already consumed during bootstrap
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- Time-limited: Likely expired
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- ✅ Cannot be reused
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3. **Vault server compromised**:
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- All secrets exposed (same as any secret storage)
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- ✅ No different from sops-nix master key compromise
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### Secret Storage
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**Runtime Secrets**:
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- Location: `/run/secrets/` (tmpfs)
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- Lost on reboot
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- Re-fetched on service start
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- ✅ Not in Nix store
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- ✅ Not persisted to disk
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**Cached Secrets**:
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- Location: `/var/lib/vault/cache/`
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- Persists across reboots
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- Only used when Vault unreachable
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- ✅ Enables service availability
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- ⚠️ May be stale
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## Failure Modes
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### Wrapped Token Expired
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**Symptom**: Bootstrap logs "token expired" error
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**Impact**: Host boots but has no Vault credentials
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**Fix**: Regenerate token and redeploy
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```bash
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create-host --hostname myhost --force
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cd terraform && tofu apply
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```
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### Vault Unreachable
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**Symptom**: Service logs "WARNING: Using cached secrets"
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**Impact**: Service uses stale secrets (may work or fail depending on rotation)
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**Fix**: Restore Vault connectivity, restart service
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### No Cache Available
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**Symptom**: Service fails to start with "No cache available"
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**Impact**: Service unavailable until Vault restored
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**Fix**: Restore Vault, restart service
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### Invalid Credentials
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**Symptom**: vault-fetch logs authentication failure
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**Impact**: Service cannot start
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**Fix**:
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1. Check AppRole exists: `vault read auth/approle/role/hostname`
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2. Check policy exists: `vault policy read host-hostname`
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3. Regenerate credentials if needed
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## Migration Path
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### Current State (Phase 4d)
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- ✅ sops-nix: Used by all existing services
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- ✅ Vault: Available for new services
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- ✅ Parallel operation: Both work simultaneously
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### Future Migration
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**Gradual Service Migration**:
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1. **Pick a non-critical service** (e.g., test service)
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2. **Add Vault secrets**:
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```nix
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vault.secrets.myservice = {
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secretPath = "hosts/myhost/myservice";
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};
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```
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3. **Update service to read from Vault**:
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```nix
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systemd.services.myservice.serviceConfig = {
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EnvironmentFile = "/run/secrets/myservice/password";
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};
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```
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4. **Remove sops-nix secret**
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5. **Test thoroughly**
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6. **Repeat for next service**
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**Critical Services Last**:
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- DNS (bind)
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- Certificate Authority (step-ca)
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- Vault itself (openbao)
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**Eventually**:
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- All services migrated to Vault
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- Remove sops-nix dependency
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- Clean up `/secrets/` directory
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## Performance Considerations
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### Bootstrap Time
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**Added overhead**: ~2-5 seconds
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- Token unwrap: ~1s
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- Credential storage: ~1s
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**Total bootstrap time**: Still <2 minutes (acceptable)
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### Service Startup
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**Added overhead**: ~1-3 seconds per service
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- Vault authentication: ~1s
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- Secret fetch: ~1s
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- File operations: <1s
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**Parallel vs Serial**:
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- Multiple services fetch in parallel
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- No cascade delays
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### Cache Benefits
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**When Vault unreachable**:
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- Service starts in <1s (cache read)
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- No Vault dependency for startup
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- High availability maintained
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## Testing Checklist
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Complete testing workflow documented in `vault-bootstrap-testing.md`:
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- [ ] Create test host with create-host
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- [ ] Add test secrets to Vault
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- [ ] Deploy VM and verify bootstrap
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- [ ] Verify secrets fetched successfully
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- [ ] Test service restart (re-fetch)
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- [ ] Test Vault unreachable (cache fallback)
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- [ ] Test secret rotation
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- [ ] Test wrapped token expiry
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- [ ] Test token reuse prevention
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- [ ] Verify critical services excluded from auto-restart
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## Files Changed
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### Created
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- `scripts/vault-fetch/vault-fetch.sh` - Secret fetching script
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- `scripts/vault-fetch/default.nix` - Nix package
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- `scripts/vault-fetch/README.md` - Documentation
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- `system/vault-secrets.nix` - NixOS module
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- `scripts/create-host/vault_helper.py` - Vault API client
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- `terraform/vault/hosts-generated.tf` - Generated Terraform
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- `docs/vault-bootstrap-implementation.md` - This file
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- `docs/vault-bootstrap-testing.md` - Testing guide
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### Modified
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- `scripts/create-host/default.nix` - Add hvac dependency
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- `scripts/create-host/create_host.py` - Add Vault integration
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- `scripts/create-host/generators.py` - Add Vault Terraform generation
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- `scripts/create-host/manipulators.py` - Add wrapped token injection
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- `terraform/cloud-init.tf` - Inject Vault credentials
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- `terraform/vms.tf` - Support vault_wrapped_token field
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- `hosts/template2/bootstrap.nix` - Unwrap token and store credentials
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- `system/default.nix` - Import vault-secrets module
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- `flake.nix` - Add vault-fetch package
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### Unchanged
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- All existing sops-nix configuration
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- All existing service configurations
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- All existing host configurations
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- `/secrets/` directory
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## Future Enhancements
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### Phase 4e+ (Not in Scope)
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1. **Dynamic Secrets**
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- Database credentials with rotation
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- Cloud provider credentials
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- SSH certificates
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2. **Secret Watcher**
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- Monitor Vault for secret changes
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- Automatically restart services on rotation
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- Faster than periodic timers
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3. **PKI Integration** (Phase 4c)
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- Migrate from step-ca to Vault PKI
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- Automatic certificate issuance
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- Short-lived certificates
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4. **Audit Logging**
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- Track secret access
|
|
- Alert on suspicious patterns
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|
- Compliance reporting
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|
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|
5. **Multi-Environment**
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|
- Dev/staging/prod separation
|
|
- Per-environment Vault namespaces
|
|
- Separate AppRoles per environment
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|
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## Conclusion
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Phase 4d successfully implements automatic Vault integration for new NixOS hosts with:
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|
|
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- ✅ Zero-touch provisioning
|
|
- ✅ Secure credential distribution
|
|
- ✅ Graceful degradation
|
|
- ✅ Backward compatibility
|
|
- ✅ Production-ready error handling
|
|
|
|
The infrastructure is ready for gradual migration of existing services from sops-nix to Vault.
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