The-transit-Project/.github/agents/azure-deploy/scaffold/references/bicep-patterns-data.md

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Bicep Patterns — Data Service Modules

Bicep module templates for database and cache services. Read when the prepare plan includes PostgreSQL, MySQL, or Redis.

For core patterns (file structure, skeleton, naming, tagging), see bicep-patterns.md. For security defaults, see bicep-patterns-security.md.

PostgreSQL Flexible Server Module — Entra-Only

⛔ Password authentication is disabled. No administratorLogin / administratorLoginPassword. The deploying principal is set as the Entra admin so migrations/seeding run token-based; the app's managed identity is granted a DB role as a post-deploy data-plane step (see database-post-deploy.md).

param pgName string
param location string
param tags object

// Entra admin = the deploying principal (so migrations can run token-based). No password params.
param entraAdminObjectId string
param entraAdminName string
@allowed(['User', 'Group', 'ServicePrincipal'])
param entraAdminType string = 'User'

param allowedExtensions string = 'uuid-ossp,pgcrypto,pg_trgm'

resource pg 'Microsoft.DBforPostgreSQL/flexibleServers@2024-08-01' = {
  name: pgName
  location: location
  tags: tags
  sku: { name: 'Standard_B1ms', tier: 'Burstable' }
  properties: {
    version: '16' // ⛔ use prepare-plan.json.services[].version (capabilities-verified) — do not guess
    // ⛔ Entra-only: no password auth, no administratorLogin/Password.
    authConfig: {
      activeDirectoryAuth: 'Enabled'
      passwordAuth: 'Disabled'
      tenantId: subscription().tenantId
    }
    storage: { storageSizeGB: 32 }
  }
}

// Entra administrator (deploying principal) — required for token-based admin + migrations.
resource pgAdmin 'Microsoft.DBforPostgreSQL/flexibleServers/administrators@2024-08-01' = {
  parent: pg
  name: entraAdminObjectId
  properties: {
    principalType: entraAdminType
    principalName: entraAdminName
    tenantId: subscription().tenantId
  }
}

// 0.0.0.0 = all Azure services (intentional) — broad access consented at the Scaffold Gate.
resource pgFirewall 'Microsoft.DBforPostgreSQL/flexibleServers/firewallRules@2024-08-01' = {
  parent: pg
  name: 'AllowAllAzureServicesAndResourcesWithinAzureIps'
  properties: { startIpAddress: '0.0.0.0', endIpAddress: '0.0.0.0' }
}

// Allow PG extensions (uuid-ossp, pgcrypto, pg_trgm)
resource pgExtensions 'Microsoft.DBforPostgreSQL/flexibleServers/configurations@2024-08-01' = {
  parent: pg
  name: 'azure.extensions'
  properties: { value: allowedExtensions, source: 'user-override' }
}

Wire connection parameters (host, db name, MI username, sslmode=require) as plain app settings — NOT a Key Vault secret. The driver fetches an Entra access token at runtime as the password. The app's managed identity is granted a DB role post-deploy via pgaadauth_create_principal (see database-post-deploy.md § Grant the app managed identity a DB role).

MySQL Flexible Server Module — Entra-Only

⛔ Password authentication is disabled. No administratorLogin / administratorLoginPassword. The deploying principal is the Entra admin; the app's MI is mapped as an AAD login post-deploy.

⛔ MySQL Entra admin REQUIRES a user-assigned managed identity (UAMI). Unlike PostgreSQL, Microsoft.DBforMySQL/flexibleServers/administrators will not deploy without a UAMI: the identityResourceId property is mandatory (the portal and az mysql flexible-server ad-admin create --identity both require it), and the parent server must carry that UAMI in its identity block. identityResourceId: null fails to deploy. The UAMI is what the server uses to read Microsoft Entra — grant it the Directory Readers role (or User.Read.All / GroupMember.Read.All / Application.Read.All app permissions) in Entra ID; emit a postDeployRecommendation for that grant since it cannot be assigned from ARM.

param mysqlName string
param location string
param tags object
param appDbName string

// Entra admin = the deploying principal. No password params.
param entraAdminObjectId string
param entraAdminName string

// UAMI required for MySQL Entra auth — the server uses it to read Entra.
resource mysqlAadIdentity 'Microsoft.ManagedIdentity/userAssignedIdentities@2023-01-31' = {
  name: '${mysqlName}-aad-id'
  location: location
  tags: tags
}

resource mysql 'Microsoft.DBforMySQL/flexibleServers@2023-12-30' = {
  name: mysqlName
  location: location
  tags: tags
  sku: { name: 'Standard_B1ms', tier: 'Burstable' }
  identity: {
    type: 'UserAssigned'
    userAssignedIdentities: {
      '${mysqlAadIdentity.id}': {}
    }
  }
  properties: {
    version: '8.0.21' // ⛔ use prepare-plan.json.services[].version (capabilities-verified) — major-only '8.0' is rejected by ARM
    storage: { storageSizeGB: 32 }
  }
}

// Entra administrator (deploying principal) — enables token-based admin + migrations.
resource mysqlAdmin 'Microsoft.DBforMySQL/flexibleServers/administrators@2023-12-30' = {
  parent: mysql
  name: 'ActiveDirectory'
  properties: {
    administratorType: 'ActiveDirectory'
    login: entraAdminName
    sid: entraAdminObjectId
    tenantId: subscription().tenantId
    identityResourceId: mysqlAadIdentity.id // ⛔ MANDATORY — MySQL AAD admin will not deploy without a UAMI
  }
}

// Enforce Entra-only auth (disable native password auth)
resource mysqlAadOnly 'Microsoft.DBforMySQL/flexibleServers/configurations@2023-12-30' = {
  parent: mysql
  name: 'aad_auth_only'
  properties: { value: 'ON', source: 'user-override' }
  dependsOn: [ mysqlAdmin ]
}

// 0.0.0.0 = all Azure services (intentional) — broad access consented at the Scaffold Gate.
resource mysqlFirewall 'Microsoft.DBforMySQL/flexibleServers/firewallRules@2023-12-30' = {
  parent: mysql
  name: 'AllowAllAzureServicesAndResourcesWithinAzureIps'
  properties: { startIpAddress: '0.0.0.0', endIpAddress: '0.0.0.0' }
}

// Enforce TLS
resource mysqlTls 'Microsoft.DBforMySQL/flexibleServers/configurations@2023-12-30' = {
  parent: mysql
  name: 'require_secure_transport'
  properties: { value: 'ON', source: 'user-override' }
}

// App database from compose (e.g. MYSQLDB_DATABASE) — emit so it exists before first boot. Omit if only the default DB is used.
resource mysqlDb 'Microsoft.DBforMySQL/flexibleServers/databases@2023-12-30' = {
  parent: mysql
  name: appDbName
}

Wire connection parameters as plain app settings (host, db name, MI username, SSL required) — NOT a Key Vault secret. The driver fetches an Entra token at runtime. The app's MI is mapped as an AAD login post-deploy (see database-post-deploy.md).

Redis Cache Module (Entra-Only)

⛔ Access-key authentication is disabled (disableAccessKeyAuthentication: true). The app's managed identity is granted data access via an access-policy assignment. Do NOT store a Redis access key in Key Vault. If the app's Redis client library cannot present an Entra token, surface it as a FLAGGED finding rather than re-enabling keys.

param redisName string
param location string
param tags object
param appPrincipalId string // the app compute MI objectId

resource redis 'Microsoft.Cache/redis@2024-03-01' = {
  name: redisName
  location: location
  tags: tags
  properties: {
    sku: { name: 'Basic', family: 'C', capacity: 0 }
    enableNonSslPort: false
    minimumTlsVersion: '1.2'
    disableAccessKeyAuthentication: true // ⛔ Entra-only
    redisConfiguration: {
      'aad-enabled': 'true'
    }
  }
}

// Data-plane access for the app MI (Entra) — no keys.
resource redisAccess 'Microsoft.Cache/redis/accessPolicyAssignments@2024-03-01' = {
  parent: redis
  name: guid(redis.id, appPrincipalId, 'Data Owner')
  properties: {
    accessPolicyName: 'Data Owner'
    objectId: appPrincipalId
    objectIdAlias: appPrincipalId
  }
}

Wire redis.properties.hostName (+ MI object id as the username) as plain app settings. The client obtains an Entra token at runtime — no key in Key Vault.