MicrosoftEntraOneDriveDownloader

Description

The MicrosoftEntraOneDriveDownloader program is a .NET application designed to interact with Microsoft Azure Blob Storage using OAuth 2.0 authentication. The program performs the following tasks:

1. Authenticate using OAuth 2.0:
   • Requests an access token from Azure Active Directory using a client ID and secret.
   • The token is used for all subsequent API calls to authenticate requests.
2. List blobs (files) in a container:
   • Retrieves the list of blobs from a specified Azure Blob Storage container.
   • Parses the response and extracts blob names and URLs.
3. Download large files in chunks:
   • Downloads each blob from the container.
   • Handles large files by dividing them into manageable chunks and writing each chunk to the destination file.
   • Supports HTTP range headers to efficiently download files in parts.

Features

• OAuth 2.0 Authentication: Secures API calls by obtaining an access token from Azure AD.
• Blob Listing: Lists all files (blobs) in the specified Azure Blob Storage container.
• Chunked File Downloads: Handles large files by downloading them in chunks to avoid memory issues.
• Customizable Parameters: Allows configuration of container URLs, destination paths, and Azure API version.
• Error Handling: Captures and logs errors during authentication, blob listing, or file download operations.

How It Works

1. Authenticate:
   • The GetAccessToken method sends a POST request to Azure AD to retrieve an access token using client credentials.
   • The token is included in the Authorization header for subsequent requests.
2. List Blobs:
   • The ListBlobsAsync method sends a GET request to the Azure Blob Storage REST API to retrieve the list of blobs in a container.
   • Parses the XML response to extract blob names and generate their URLs.
3. Download Files:
   • The DownloadLargeFile method downloads each blob from the container in chunks.
   • Uses HTTP range headers to fetch specific byte ranges of the file.
   • Writes each chunk sequentially to a file in the specified destination directory.

Prerequisites

• .NET SDK (for building and running the program)
• A valid Azure subscription
• An Azure Blob Storage account with the following:
  • Container URL
  • Client ID
  • Client secret

Configuration

To configure the program, update the following values in the code:

• Azure AD OAuth Settings:

var values = new Dictionary<string, string>
{
    { "client_id", "<YOUR_CLIENT_ID>" },
    { "client_secret", "<YOUR_CLIENT_SECRET>" },
    { "resource", "https://storage.azure.com" },
    { "grant_type", "client_credentials" }
};

• Container URL and Destination Path:

string containerUrl = "<YOUR_CONTAINER_URL>";
string destinationPath = "<YOUR_DESTINATION_PATH>";

• Azure API Version:

string msVersion = "2020-04-08";

Usage

Build and run the program using your preferred .NET IDE (e.g., Visual Studio) or command-line tools.

The program will:

• Authenticate with Azure AD.
• List all blobs in the specified container.
• Download each blob to the specified local directory.

Example Output:

Downloaded chunk 1/4: samplefile.txt
Downloaded chunk 2/4: samplefile.txt
Downloaded chunk 3/4: samplefile.txt
Downloaded chunk 4/4: samplefile.txt

References

• Azure Storage REST API Documentation
• Microsoft Authentication Library (MSAL)