Skip to main content

Encrypt/Decrypt text using the new Azure Key Vault Client Libraries

Securing applications is hard. We often have to struggle with storing connection strings, encryption keys and other sensitive pieces of information securely in our code base. Azure Key Vault is a great place to store these securely and allow only limited access to authorized applications. Azure Key Vault can store Keys, Secrets and Certificates. It supports storing only asymmetric keys (RSA and EC). One can generate a key in Azure Key Vault and it will only give out Public Key to your application. All operations involving Private Key has to be done by Azure Key Vault only. Encryption algorithms like AES are symmetric encryption methods - meaning they use one key to encrypt and decrypt the data. There are two ways we can store this key - either as a secret in Azure Key Vault (less secure) or encrypt the key itself using the RSA key generated in Azure Key Vault and store the encrypted key as a secret (more secure). If you are using .NET, there are numerous examples on the interwebs showing how to do this using the old Microsoft.Azure.KeyVault libraries. (Un)Fortunately those libraries are now replaced by new Azure SDKs splitting the one library in three separate Nuget packages:


How do we encrypt/decrypt using these packages? Sadly the documentation regarding these is sparse. Hence this blog post.

In the following code, we create a small console application using .NET Core and pull down a RSA key generated in Azure Key Vault named "KEK" (Key Encryption Key). We use that key to encrypt the string passed in by the user and store in Azure Key Vault as a secret. Finally to get back the original string, we pull down the secret stored in previous step and use the KEK to decrypt the string back to original value.

using System;
using System.Text;
using Azure.Identity;
using Azure.Security.KeyVault.Keys;
using Azure.Security.KeyVault.Keys.Cryptography;
using Azure.Security.KeyVault.Secrets;
namespace key_vault_console_app
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Enter string to encrypt:");
            var keyToEncrypt = Console.ReadLine();
            Console.WriteLine("Encrypting...");
            var credential = new ClientSecretCredential("AzureTenantId", "ClientId", "ClientSecret");
            var kvUri = "https://YourKeyVaultName.vault.azure.net";
            var client = new KeyClient(new Uri(kvUri), credential);
            var key = client.GetKey("KEK");
            var cryptoClient = new CryptographyClient(key.Value.Id, credential);
            EncryptResult encryptResult = cryptoClient.Encrypt(EncryptionAlgorithm.RsaOaep256, Encoding.UTF8.GetBytes(keyToEncrypt));
            Console.WriteLine("Encrypted string is: " + Convert.ToBase64String(encryptResult.Ciphertext));
// Store the encrypted key in Azure KV as secret
            var secretClient = new SecretClient(new Uri(kvUri), credential);
            secretClient.SetSecret(new KeyVaultSecret("EncryptedKey1", Convert.ToBase64String(encryptResult.Ciphertext)));

            Console.WriteLine("Do you want to decrypt? (Y/N)");
            if (Console.ReadLine().ToUpper() == "Y")
            {
                var encryptedSecret = secretClient.GetSecret("EncryptedKey1");
                DecryptResult decryptResult = cryptoClient.Decrypt(EncryptionAlgorithm.RsaOaep256, Convert.FromBase64String(encryptedSecret.Value.Value));
                Console.WriteLine("Decrypted string is: " + Encoding.UTF8.GetString(decryptResult.Plaintext));
            }
            Console.ReadLine();
        }
    }
}
Hope the above example helps someone struggling with using the new Azure SDKs. Is there a better way to do this? Do let me know in the comments below.

Comments

Popular posts from this blog

Integrating React with SonarQube using Azure DevOps Pipelines

In the world of automation, code quality is of paramount importance. SonarQube and Azure DevOps are two tools which solve this problem in a continuous and automated way. They play well for a majority of languages and frameworks. However, to make the integration work for React applications still remains a challenge. In this post we will explore how we can integrate a React application to SonarQube using Azure DevOps pipelines to continuously build and assess code quality. Creating the React Application Let's start at the beginning. We will use npx to create a Typescript based React app. Why Typescript? I find it easier to work and more maintainable owing to its strongly-typed behavior. You can very well follow this guide for jsx based applications too. We will use the fantastic Create-React-App (CRA) tool to create a React application called ' sonar-azuredevops-app '. > npx create-react-app sonar-azuredevops-app --template typescript Once the project creation is done, we

Centralized Configuration for .NET Core using Azure Cosmos DB and Narad

We are living in a micro services world. All these services are generally hosted in Docker container which are ephemeral. Moreover these service need to start themselves up, talk to each other, etc. All this needs configuration and there are many commercially available configuration providers like Spring Cloud Config Server, Consul etc. These are excellent tools which provide a lot more functionality than just storing configuration data. However all these have a weakness - they have a single point of failure - their storage mechanism be it a file system, database etc. There are ways to work around those but if you want a really simple place to store configuration values and at the same time make it highly available, with guaranteed global availability and millisecond reads, what can be a better tool than Azure Cosmos DB! So I set forth on this journey for ASP.NET Core projects to talk to Cosmos DB to retrieve their configuration data. For inspiration I looked at Steeltoe Con

Proud to be a Bihari?

After nearly an year, this December I had a chance to visit Bihar. My visits normally consist of resting in my home in Patna and occasional visits to my uncle's place. But this time it was different. I had to go to Gaya to attend my cousin sister's marriage ceremony. Stepping out of Patna made me question - Am I really proud to be a Bihari? Patna is like any other city in India, struggling with pollution, traffic jams, crime, etc. Being snuggled in my bed in Patna had made me forget the reality of what Bihar really is; after all its been nearly 10 years since I had traveled to any town outside of Patna in Bihar. So, the illusion was broken the moment my uncle's brand new Maruti A-Star moved out of outskirts of Patna, to what is supposedly the "National Highway". If you haven't guessed it already, its an apology of a road.