Quick Track: Beginner’s Guide to Azure SQL- Network Security Concepts

Let’s learn a bit about Security in this post.

Securing something you built is as important as creating it. Any resource that you create needs to have in depth layers of protection to save it from the bad eyes.

Let’s take the analogy of the Bank systems where you save your money and other valuables. Starting from the parking lot of the bank till the door of the bank vault where the actual money is stored, there is multi layer of security. Cameras, digital locks, padlocks and more locks to reach the money. This is in depth security system. Breaking any layer can only result in more effort to crack an another layer which is even more difficult.

Same goes with the Data. No matter you are on-prem or in the cloud, Data needs to be protected and there are no exceptions.

Securing data in Azure is an important part and there are different security layers available in Azure. Below diagram shows you the different layers of Security we have in Azure to reach the customer data.

In this post, let’s focus on the Network security.

Source: https://docs.microsoft.com/en-us/azure/azure-sql/database/security-overview?view=azuresql

Network Security

The below table will give an idea about different Network security options available and the differences among them.

Allow Access to Azure ServicesFirewall rulesVirtual network rulesPrivate link
Least secureSecure with firewallPrivate IP address of the Azure VMMost secure
Anything in Azure can connectServices with added Firewall rules can connectAny resource in that VN can access Azure SQLBlock all public access
Outside of Azure cannot connectAllow on-prem connectionsApply virtual network technologies to connect on-premPrivate IP address within a specific virtual network
Public IP addressPublic IP addressPrivate IP address within the VNPrivate IP address
DNS hierarchy is publicDNS hierarchy is public (region, cr)DNS hierarchy is still public (region, cr)DNS hierarchy shows private endpoint

In any specific region you have hosting the Azure SQL Databases, your client can connect to Azure SQL database using the Gateways having the public ip addresses. Gateways are the intermediate layer in between the Azure SQL database and the client. Client can connect to Azure SQL database through these gateways in two ways.

Proxy: We can understand this by simple analogy. You want to visit your friend’s apartment frequently but at the security gate, the watch man asks you several questions where you need to prove your authenticity to enter into your friend’s home every time you want to visit him. That is the proxy mode. Here, the DNS will resolve from one of the multiple gateways through port 1433. Each time the client want to connect, the gateway will act as a proxy in between to connect to the database. Proxy mode is the default mode and if you are trying to connect from outside Azure.

Redirection: You want to visit your friend’s apartment frequently and this time, you will receive additional key to the apartment at the entrance as you prove your authentication. Once you receive the key, you can directly go to the apartment with out any intermediate layer of security check at the gate. In the redirection mode, a redirect token is assigned when the client connects to the gateway and all the connections made to the database next doesn’t have to pass through the gateway. The redirect token contains the ip address of the database and the port in between the range 11000 to 11999. Redirection mode is default if you are trying to connect to the database within azure.

These gateways are known as data slices when they are logically grouped together. These data slices are used for the load balancing.

Let’s learn about each of the network security layer:

1. Allow access to Azure Services: Anything in azure can connect to your database if you enable this option. Any azure resource from any subscription and from any region. On-prem Servers cannot connect using this option. This option is a kind of the firewall rules where the start and end ip addresses were all zeros.

2. Firewall rules: These are the firewall rules that you create like any other on-prem Servers. By adding the client ip addresses here in the firewall rules, the client can connect to the Azure SQL database. On-prem servers can connect to Azure by using this option.

3. Virtual network rules: Clients from the specific virtual network subnets can connect to the Azure SQL through the private IP address.

4. Private Link: Private link is creating a private ip address from the virtual network which can connect to your database privately. Internet will be disconnected here. To create a private endpoint, we need to know what resource type you are creating the private endpoint for. It can be Azure SQL Database or the storage account, then on which virtual network and subnet we are going to create this endpoint.

Here is the youtube link you can follow to create a Private link for your database.

In the next article, we will be learning about the next security later, Access Management.

Thanks for reading!

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