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MI Azure Managed Identity for Laravel

This package enables Azure Managed Identity (MI) authentication for:

1) Azure Blob Storage (Laravel Storage disk: azure) 2) Azure Cache for Redis (Laravel Redis client: azure-mi) 3) Azure Database for PostgreSQL (Laravel DB connector: pgsql)

It fetches short-lived access tokens from the Azure Instance Metadata Service (IMDS), caches them (recommended: file cache), then injects them into each client connection so the application can authenticate without long-lived secrets.

Table of Contents

• High-Level Overview
• Token Service
• Configuration
  • Config File
  • .env Variables
• Azure Blob Storage
  • How It Works
  • Mermaid Flow Chart
  • Test Command
• Azure Redis
  • How It Works
  • Mermaid Flow Chart
  • Test Command
• Azure PostgreSQL (pgsql)
  • How It Works
  • Mermaid Flow Chart
  • Notes About Read/Write Hosts
• Logging
• Security Notes
• Troubleshooting

High-Level Overview

All services follow the same MI pattern:

1) Determine if MI is enabled for that service/connection. 2) Fetch a token from IMDS:

• Endpoint: http://169.254.169.254/metadata/identity/oauth2/token
• Header: Metadata: true
• Params:
  • api-version=...
  • resource=...
  • optional client_id=... (User Assigned Managed Identity) 3) Cache the token in Laravel cache (recommended: file). 4) Inject the token into the relevant client:
• Storage: Authorization: Bearer <token>
• Redis: password=<token> (and username=<aad-user>)
• PostgreSQL: password=<token> 5) Connect normally through Laravel APIs.

Token Service

Class

MI\AzureManagedIdentity\Services\AzureManagedIdentityTokenService

Responsibilities

• Read resource configuration from: config('azure-managed-identity.resources.<key>')
• Fetch token from IMDS with the correct:
  • resource
  • api-version
  • optional client_id
• Cache tokens by:
  • resource key (e.g. storage, redis, db)
  • client id (or system)
• Apply a buffer before expiry to reduce refresh failures.

Token caching key pattern

Why file cache is recommended

• Avoids any circular dependency (for example: if Redis needs MI, you must not depend on Redis to cache the MI token).
• Keeps startup reliable.
• Works well in containers as long as the filesystem is writable.

Configuration

Config File

config/azure-managed-identity.php

.env Variables

Minimum recommended variables (based on the provided classes):

Azure Blob Storage

How Blob Works

Classes involved

• Service Provider:
  • MI\AzureManagedIdentity\Providers\AzureServiceProvider
• Disk adapter:
  • MI\AzureManagedIdentity\Filesystem\AzureAdapter
• Blob client wrapper:
  • MI\AzureManagedIdentity\Services\ManagedIdentityBlobRestProxy
• Token fetcher:
  • MI\AzureManagedIdentity\Services\AzureManagedIdentityTokenService

What happens when you call Storage::disk('azure')?

1) AzureServiceProvider::boot() registers a custom driver:

• Storage::extend('azure', ...) 2) When the disk is used:
• If use_managed_identity=true in the disk config:
  • Fetch token using TokenService->getAccessToken($clientId, 'storage') 3) The blob client is created:
• ManagedIdentityBlobRestProxy::createWithManagedIdentity(...) 4) A custom Guzzle middleware injects:
• Authorization: Bearer <token>
• x-ms-version: 2021-08-06 5) Flysystem adapter is created and returned as a Laravel disk. 6) Your app uses it like normal:
• list files
• put files
• get files
• delete files
• etc.

Why a custom HTTP client is injected

The microsoft/azure-storage-blob SDK is primarily designed for Shared Key / SAS.
Your implementation injects a Bearer-token aware HTTP client so requests are authenticated using MI.

Blob Mermaid Flow Chart

Blob Test Command

Command: azure:test

What it does:

• If MI is enabled, it fetches a token and performs a direct container list request.
• Then it tries a normal Laravel Storage call (files()) to confirm end-to-end integration.

Azure Redis

How Redis Works

Classes involved

• Redis connector:
  • MI\AzureManagedIdentity\Redis\AzureManagedIdentityPhpRedisConnector
• Token fetcher:
  • MI\AzureManagedIdentity\Services\AzureManagedIdentityTokenService
• Service Provider registration:
  • MI\AzureManagedIdentity\Providers\AzureServiceProvider

What happens when you call Redis::connection('default')?

1) You set:

• REDIS_CLIENT=azure-mi 2) AzureServiceProvider::boot() registers:
• Redis::extend('azure-mi', ...) 3) Laravel uses AzureManagedIdentityPhpRedisConnector when connecting. 4) Inside connect():
• If use_managed_identity=true for that Redis connection:
  • Validate username exists (required for Azure Redis AAD auth)
  • Fetch token via:
    • TokenService->getAccessToken($clientId, 'redis')
  • Set:
    • config['password'] = <token>
    • config['username'] = <aad-username> 5) Parent connector connects normally. 6) Redis commands work normally (PING, SET, GET, etc.).

Required Redis config fields

When MI is enabled, the Redis connection config must provide:

• username (the AAD principal/object id used by Redis AAD auth)
• scheme=tls (recommended)
• port=6380 (common for TLS)

Redis Mermaid Flow Chart

Redis Test Command

Command: azure:redis-test

What it does:

• Connects using Laravel Redis Manager
• Executes:
  • PING
  • SET then GET

Azure PostgreSQL (pgsql)

How DB Works

Classes involved

• Postgres connector:
  • MI\AzureManagedIdentity\Database\AzureManagedIdentityPostgresConnector
• Token fetcher:
  • MI\AzureManagedIdentity\Services\AzureManagedIdentityTokenService
• Service Provider binding:
  • MI\AzureManagedIdentity\Providers\AzureServiceProvider

What happens when Laravel connects to pgsql?

1) In AzureServiceProvider::register(), the package binds:

• db.connector.pgsql → AzureManagedIdentityPostgresConnector 2) When Laravel creates a pgsql connection, it uses this connector. 3) Inside connect(array $config):
• Determine if MI is enabled:
  • use_managed_identity in the pgsql config
• If enabled:
  • Fetch token via:
    • TokenService->getAccessToken($clientId, 'db')
  • Set:
    • config['password'] = <token>
  • Ensure SSL:
    • If sslmode is empty, set it to require 4) The connector calls parent::connect($config) which creates the real PDO connection. 5) From the application point of view, DB queries work normally.

What the DB token represents

For Azure Database for PostgreSQL with Entra/AAD auth, the access token acts like a short-lived password for the configured DB user. Your DevOps verification command mirrors that behavior:

• fetch token from IMDS for resource:
  • https://ossrdbms-aad.database.windows.net
• use it as PGPASSWORD
• connect using TLS (sslmode=require)

DB Mermaid Flow Chart

Notes About Read/Write Hosts

Your database.php supports read replicas:

Laravel may connect to:

• write host for write operations
• read host for read operations (depending on query patterns and runtime)

Managed Identity still works because:

• The connector injects the token as the password for every pgsql connection attempt.
• SSL mode should be require for Azure PostgreSQL.

If you experience authentication issues only on read replicas, that usually means the replica side is not configured to accept the same Entra/AAD principal or security rules differ.

Logging

The package logs:

• service start (storage/redis/db)
• cached token usage vs IMDS call
• token caching TTL (without printing the token)
• connection success

Recommended:

• Keep LOG_LEVEL=debug in non-prod environments while validating.
• Never log the raw token; only log token length if needed.

Security Notes

• Use AZURE_MI_CACHE_STORE=file to avoid circular dependencies (Redis itself might require MI).
• Tokens are short-lived and automatically refreshed before expiry by the cache buffer strategy.
• Use TLS for:
  • Azure Redis (commonly scheme=tls and port=6380)
  • Azure PostgreSQL (sslmode=require)
• Ensure the filesystem used by file cache is writable by the application user and not world-readable.

Troubleshooting

Storage fails (403/401)

• Ensure the managed identity has correct RBAC on the Storage Account:
  • typically Storage Blob Data Contributor (or as required)
• Validate AZURE_MI_STORAGE_RESOURCE is https://storage.azure.com/

Redis fails

Common causes:

• Missing username in redis connection config
• Not using TLS or using wrong port
• Wrong resource:
  • must be https://redis.azure.com
• AAD not enabled/configured for the Redis instance

DB fails (password authentication failed)

Common causes:

• DB_USERNAME does not match the Entra/AAD configured DB user/principal
• wrong DB token resource:
  • must be https://ossrdbms-aad.database.windows.net
• SSL not required:
  • set DB_SSLMODE=require
• read replicas not configured the same as primary