Programmatically Create SAS tokens in .NET

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Andrew Redman explores how to programmatically create SAS tokens using .NET.


Introduction

In today’s digital landscape, data security and controlled access are critical concerns for businesses. Azure Blob Storage is a popular cloud storage solution, allowing you to store and manage unstructured data. To safeguard your data while granting controlled access to authorized users, one effective approach is to generate Shared Access Signature (SAS) tokens programmatically in .NET. In this blog post, we’ll explore how to create SAS tokens in .NET, to enhance the security of your Azure Blob Storage.

 

All the code used in this blob post can be found in Github.  Please check it out if you would like to have an example of this running locally in a Console app.

 

Disclaimer

While Shared Access Signature (SAS) tokens provide a valuable mechanism for granting temporary, controlled access to specific resources in Azure Blob Storage, it is essential to acknowledge that SAS is not always the first option for security measures. In many scenarios, Role-Based Access Control (RBAC) using Azure Active Directory (Azure AD) or other identity providers should be the primary choice for access control and security enforcement.

 

Use Case for SAS over RBAC

SAS tokens are particularly useful in scenarios where you need to grant time-limited, fine-grained access to specific resources without granting broader permissions. For example, when collaborating with external users or granting access to temporary services, SAS tokens offer a secure approach for limited access without the need for permanent user accounts.  Here are some additional use cases for using SAS if you are interested in learning more.

 

What is a SAS token?

A SAS token is a secure, time-limited URL that grants limited access to specific resources in your Azure Blob Storage account. When you create a SAS token, you can define its permissions, validity period, and which resources can be accessed. This provides a powerful mechanism to grant temporary, controlled access to your Blob Storage without compromising your account’s primary access keys.

 

When generating SAS tokens, adhering to the least privileged principle is crucial.  Only provide the necessary permissions required for the specific task.  Granting excessive permissions in the SAS token could expose your data to unnecessary risks.  By defining precise permissions (read, write, list, delete, etc.) and setting an appropriate expiration time, you can ensure that the SAS token is valid only for the required duration and with limited access. If you are interested in learning more about SAS tokens, you can find more information in this document Storage SAS Overview (be sure to check out the Best Practices section which contains a few of the features we have and will discuss in this blog post).

Continue reading Andrew’s full post over in the Healthcare and Life Sciences Technical Community.

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