Using the Azure CDN to access blobs with custom domains over HTTPS
Azure Content Delivery Network (CDN) now supports HTTPS for custom domain names. You can leverage this feature to access storage blobs using your custom domain over HTTPS. To do so, you’ll first need to enable Azure CDN on your blob endpoint and map the CDN to a custom domain name. Once you take these steps, enabling HTTPS for your custom domain is simplified via one-click enablement, complete certificate management, and all with no additional cost to normal CDN pricing.
This ability is important because it enables you to protect the privacy and data integrity of your sensitive web application data while in transit. Using the SSL protocol to serve traffic via HTTPS ensures that data is encrypted when it is sent across the internet. HTTPS provides trust and authentication, and protects your web applications from attacks.
In addition to providing SSL support for custom domain names, the Azure CDN can help you scale your application to deliver high-bandwidth content around the world. To learn more, check out Overview of the Azure CDN.
These are the steps required to enable HTTPS for your custom blob storage endpoint:
- Integrate an Azure storage account with Azure CDN. This article walks you through creating a storage account in the Azure Portal if you have not done so already.
- Map Azure CDN content to a custom domain.
- Enable HTTPS on an Azure CDN custom domain.
Shared Access Signatures
If your blob storage endpoint is configured to disallow anonymous read access, you will need to provide a Shared Access Signature (SAS) token in each request you make to your custom domain. By default, blob storage endpoints disallow anonymous read access. See Managing anonymous read access to containers and blobs for more information on shared access signatures.
Azure CDN does not respect any restrictions added to the SAS token. For example, all SAS tokens have an expiration time. This means that content can still be accessed with an expired SAS until that content is purged from the CDN edge nodes. You can control how long data is cached on the CDN by setting the cache response header. See Managing expiration of Azure Storage blobs in Azure CDN for instructions.
If you create multiple SAS URLs for the same blob endpoint, we recommend turning on query string caching for your Azure CDN. This is to ensure that each URL is treated as a unique entity. See Controlling Azure CDN caching behavior with query strings for more information.
HTTP to HTTPS redirection
You can elect to redirect HTTP traffic to HTTPS. This requires use of the Azure CDN premium offering from Verizon. You need to Override HTTP behavior using the Azure CDN rules engine with the following rule:
“Cdn-endpoint-name” refers to the name that you configured for your CDN endpoint. You can select this value from the dropdown. “Origin-path” refers to the path within your origin storage account where your static content resides. If you are hosting all static content in a single container, replace “origin-path” with the name of that container.
For a deeper dive into rules, please see the Azure CDN rules engine features.
Pricing and billing
For example, say you have a storage account in West US that is being accessed using an Azure CDN. If someone in the UK tries to access one of the blobs in that storage account via the CDN, Azure first checks the edge node closest to the UK for that blob. If found, it accesses that copy of the blob and will use CDN pricing, because it is being accessed on the CDN. If not found, Azure will copy the blob to the edge node, which will result in egress and transaction charges as specified in the Blob storage pricing, and then access the file on the edge node, which will result in CDN billing.
When looking at the CDN pricing page, note that HTTPS support for custom domain names is only available for Azure CDN from Verizon products (Standard and Premium).