Azure Blob Storage for Secure Document Management

Introduction

Azure Blob Storage is a scalable, secure, and cost-effective storage solution for unstructured data such as images, videos, and documents. This blog highlights a real-world implementation for a legal services client that used Azure Blob Storage to streamline and secure their document management system.

Client Overview

Client: International Legal Services Firm

The client handles large volumes of confidential legal documents, including contracts, case files, and compliance records, which must be securely stored, managed, and accessed across multiple global offices.

Challenges:

1. Scalability Issues: Their existing on-premises file storage struggled to handle growing volumes of data.
2. Security Concerns: Sensitive legal documents needed enhanced security and controlled access.
3. Inefficient Collaboration: Sharing documents across global teams was slow and prone to versioning errors.
4. Cost Overruns: Managing on-premises storage infrastructure incurred high maintenance costs.

Solution: Document Management System with Azure Blob Storage

We implemented a cloud-based document management system using Azure Blob Storage as the backbone for secure, scalable, and efficient file storage. The system was integrated with Azure Active Directory (AAD) for access control, Azure Key Vault for encryption, and Azure Functions for automated workflows.

Architecture Overview

1. Data Storage: Documents are stored in Azure Blob Storage within a highly secure storage account.
2. Security:
   • Role-based access control (RBAC) through AAD.
   • Data encryption at rest using Azure Key Vault.
3. Automation:
   • Azure Functions handle automatic file organization and retention policies.
4. Access and Collaboration:
   • Shared Access Signatures (SAS) enable secure, time-limited sharing of documents.
5. Monitoring: Azure Monitor tracks storage usage, access logs, and security incidents.

Implementation Details

1. Storage Account Setup

A Blob Storage account was created with the following configurations:

• Hot Tier: For frequently accessed files.
• Cool Tier: For infrequently accessed, archived case files.
• Private Endpoint: Ensures access only through the client’s virtual network.

2. Data Organization

Blobs were organized into containers:

• /contracts
• /case-files
• /compliance-docs

Each container followed a naming convention for easy retrieval, e.g., case-files/2024/Q1/ClientName_FileName.pdf.

3. Security Implementation

1. Access Control:

   • Azure Active Directory (AAD) RBAC ensured only authorized users could access specific containers.
   • Users were assigned roles such as Reader, Contributor, or Owner.

2. Encryption:

   • Data at rest was encrypted using Microsoft-managed keys.
   • Sensitive files were encrypted using customer-managed keys stored in Azure Key Vault.

3. SAS Tokens:

   • Time-limited SAS URLs were generated for secure file sharing with external clients or stakeholders.

4. Automation with Azure Functions

Azure Functions automated key workflows:

• File Organization: Automatically moved files to appropriate containers based on metadata (e.g., file type, date).
• Retention Policy: Deleted files older than 5 years to comply with data retention regulations.
• Notifications: Sent email alerts to users when new documents were uploaded to shared containers.

Code Example: Azure Function for Retention Policy

public static async Task Run(TimerInfo myTimer, ILogger log)

{

    string connectionString = Environment.GetEnvironmentVariable("AzureWebJobsStorage");

    BlobServiceClient blobServiceClient = new BlobServiceClient(connectionString);

    BlobContainerClient containerClient = blobServiceClient.GetBlobContainerClient("case-files");

    await foreach (BlobItem blobItem in containerClient.GetBlobsAsync())

    {

        var properties = containerClient.GetBlobClient(blobItem.Name).GetProperties();

        if (properties.Value.LastModified < DateTime.UtcNow.AddYears(-5))

        {

            await containerClient.DeleteBlobIfExistsAsync(blobItem.Name);

            log.LogInformation($"Deleted: {blobItem.Name}");

        }

    }

}