Implementing HashiCorp Vault Dynamic Secrets

When to Use

• Applications use static database credentials stored in configuration files or environment variables
• AWS IAM access keys are long-lived and shared across services
• Need to eliminate credential sprawl by generating short-lived, per-request secrets
• Compliance requirements mandate credential rotation (PCI-DSS Requirement 8, NIST 800-53 IA-5)
• Implementing zero-trust secret management where credentials are never stored at rest
• Migrating from manual credential management to automated secrets lifecycle

Do not use for storing static secrets that cannot be dynamically generated (use Vault's KV secrets engine instead); dynamic secrets are for credentials that can be programmatically created and revoked on target systems.

Prerequisites

• HashiCorp Vault 1.15+ (Community or Enterprise edition)
• Vault server initialized and unsealed with auto-unseal configured (AWS KMS, Azure Key Vault, or Transit)
• Target database systems with admin credentials for Vault to create/revoke dynamic accounts
• AWS IAM account with permissions to create/delete IAM users and access keys
• Network connectivity from Vault to all target systems
• Vault policies and authentication methods configured for consuming applications

Workflow

Step 1: Deploy and Configure Vault Server

Initialize Vault with production-grade configuration:

# vault-config.hcl - Production Vault server configuration
storage "raft" {
  path    = "/opt/vault/data"
  node_id = "vault-1"

  retry_join {
    leader_api_addr = "https://vault-2.corp.local:8200"
  }
  retry_join {
    leader_api_addr = "https://vault-3.corp.local:8200"
  }
}

listener "tcp" {
  address       = "0.0.0.0:8200"
  tls_cert_file = "/opt/vault/tls/vault-cert.pem"
  tls_key_file  = "/opt/vault/tls/vault-key.pem"
}

seal "awskms" {
  region     = "us-east-1"
  kms_key_id = "alias/vault-unseal-key"
}

api_addr      = "https://vault-1.corp.local:8200"
cluster_addr  = "https://vault-1.corp.local:8201"

telemetry {
  prometheus_retention_time = "24h"
  disable_hostname          = true
}

ui = true

# Initialize Vault cluster
vault operator init -key-shares=5 -key-threshold=3

# Enable audit logging
vault audit enable file file_path=/var/log/vault/audit.log

# Enable AppRole authentication for applications
vault auth enable approle

# Create policy for database secret consumers
vault policy write db-consumer - <<EOF
# Allow reading dynamic database credentials
path "database/creds/app-readonly" {
  capabilities = ["read"]
}
path "database/creds/app-readwrite" {
  capabilities = ["read"]
}

# Allow renewing and revoking own leases
path "sys/leases/renew" {
  capabilities = ["update"]
}
path "sys/leases/revoke" {
  capabilities = ["update"]
}

# Allow reading own token info
path "auth/token/lookup-self" {
  capabilities = ["read"]
}
EOF

# Create AppRole for application
vault write auth/approle/role/webapp \
    token_policies="db-consumer" \
    token_ttl=1h \
    token_max_ttl=4h \
    secret_id_ttl=720h \
    secret_id_num_uses=0

Step 2: Configure Database Secrets Engine

Set up dynamic credential generation for PostgreSQL and MySQL:

# Enable the database secrets engine
vault secrets enable database

# Configure PostgreSQL connection
vault write database/config/production-postgres \
    plugin_name=postgresql-database-plugin \
    allowed_roles="app-readonly,app-readwrite,app-admin" \
    connection_url="postgresql://{{username}}:{{password}}@db-primary.corp.local:5432/appdb?sslmode=verify-full" \
    username="vault_admin" \
    password="$VAULT_DB_PASSWORD" \
    password_authentication="scram-sha-256"

# Rotate the root credentials so Vault manages them exclusively
vault write -force database/rotate-root/production-postgres

# Create read-only role (TTL: 1 hour, max 24 hours)
vault write database/roles/app-readonly \
    db_name=production-postgres \
    creation_statements="CREATE ROLE \"{{name}}\" WITH LOGIN PASSWORD '{{password}}' VALID UNTIL '{{expiration}}'; \
        GRANT SELECT ON ALL TABLES IN SCHEMA public TO \"{{name}}\"; \
        ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT ON TABLES TO \"{{name}}\";" \
    revocation_statements="REVOKE ALL PRIVILEGES ON ALL TABLES IN SCHEMA public FROM \"{{name}}\"; \
        DROP ROLE IF EXISTS \"{{name}}\";" \
    default_ttl="1h" \
    max_ttl="24h"

# Create read-write role (TTL: 30 minutes, max 8 hours)

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