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Azure Key Vault Certificate client library for .NET

Azure Key Vault is a cloud service that provides secure storage and automated management of certificates used throughout a cloud application. Multiple certificate, and multiple versions of the same certificate, can be kept in the Key Vault. Each certificate in the vault has a policy associated with it which controls the issuance and lifetime of the certificate, along with actions to be taken as certificates near expiry.

The Azure Key Vault Certificate client library enables programmatically managing certificates, offering methods to create, update, list, and delete certificates, policies, issuers, and contacts. The library also supports managing pending certificate operations and management of deleted certificates.

Source code | Package (NuGet) | API reference documentation | Product documentation | Samples

Getting started

Install the package

Install the Azure Key Vault Certificates client library for .NET with NuGet:

Install-Package Azure.Security.KeyVault.Certificates -IncludePrerelease

Prerequisites

If you use the Azure CLI, replace <your-resource-group-name> and <your-key-vault-name> with your own, unique names:

az keyvault create --resource-group <your-resource-group-name> --name <your-key-vault-name>

Authenticate the client

In order to interact with the Key Vault service, you'll need to create an instance of the CertificateClient class. You would need a vault url, which you may see as "DNS Name" in the portal, and client secret credentials (client id, client secret, tenant id) to instantiate a client object.

Client secret credential authentication is being used in this getting started section but you can find more ways to authenticate with Azure identity. To use the DefaultAzureCredential provider shown below, or other credential providers provided with the Azure SDK, you should install the Azure.Identity package:

Install-Package Azure.Identity

Create/Get credentials

Use the Azure CLI snippet below to create/get client secret credentials.

  • Create a service principal and configure its access to Azure resources:

    az ad sp create-for-rbac -n <your-application-name> --skip-assignment

    Output:

    {
    "appId": "generated-app-ID",
    "displayName": "dummy-app-name",
    "name": "http://dummy-app-name",
    "password": "random-password",
    "tenant": "tenant-ID"
}

  • Use the returned credentials above to set AZURE_CLIENT_ID(appId), AZURE_CLIENT_SECRET(password) and AZURE_TENANT_ID(tenant) environment variables. The following example shows a way to do this in Powershell:

    $Env:AZURE_CLIENT_ID="generated-app-ID"
$Env:AZURE_CLIENT_SECRET="random-password"
$Env:AZURE_TENANT_ID="tenant-ID"

  • Grant the above mentioned application authorization to perform key operations on the key vault:

    az keyvault set-policy --name <your-key-vault-name> --spn $AZURE_CLIENT_ID --certificate-permissions backup delete get list create update purge

    --certificate-permissions: Allowed values: backup, create, delete, deleteissuers, get, getissuers, import, list, listissuers, managecontacts, manageissuers, purge, recover, restore, setissuers, update.

  • Use the above mentioned Key Vault name to retrieve details of your Vault which also contains your Key Vault URL:

    az keyvault show --name <your-key-vault-name>

Create CertificateClient

Once you've populated the AZURE_CLIENT_ID, AZURE_CLIENT_SECRET and AZURE_TENANT_ID environment variables and replaced your-vault-url with the above returned URI, you can create the CertificateClient:

// Create a new certificate client using the default credential from Azure.Identity using environment variables previously set,
// including AZURE_CLIENT_ID, AZURE_CLIENT_SECRET, and AZURE_TENANT_ID.
var client = new CertificateClient(vaultUri: new Uri(keyVaultUrl), credential: new DefaultAzureCredential());

Key concepts

KeyVaultCertificate

A KeyVaultCertificate is the fundamental resource within Azure Key Vault. You'll use certificates to encrypt and verify encrypted or signed data.

CertificateClient

With a CertificateClient you can get certificates from the vault, create new certificates and new versions of existing certificates, update certificate metadata, and delete certificates. You can also manage certificate issuers, contacts, and management policies of certificates. This is illustrated in the examples below.

Examples

The Azure.Security.KeyVault.Certificates package supports synchronous and asynchronous APIs.

The following section provides several code snippets using the above created client, covering some of the most common Azure Key Vault certificate service related tasks:

Sync examples

Async examples

Create a certificate

StartCreateCertificate creates a Certificate to be stored in the Azure Key Vault. If a certificate with the same name already exists, then a new version of the certificate is created. When creating the certificate the user can specify the policy which controls the certificate lifetime. If no policy is specified the default policy will be used. The StartCreateCertificate operation returns a CertificateOperation. The following example creates a self-signed certificate with the default policy.

// Create a certificate. This starts a long running operation to create and sign the certificate.
CertificateOperation operation = client.StartCreateCertificate("MyCertificate", CertificatePolicy.Default);

// You can await the completion of the create certificate operation.
// You should run UpdateStatus in another thread or do other work like pumping messages between calls.
while (!operation.HasCompleted)
{
    Thread.Sleep(2000);

    operation.UpdateStatus();
}

KeyVaultCertificateWithPolicy certificate = operation.Value;

NOTE: Depending on the certificate issuer and validation methods, certificate creation and signing can take an indeterminate amount of time. Users should only wait on certificate operations when the operation can be reasonably completed in the scope of the application, such as with self-signed certificates or issuers with well known response times.

Retrieve a certificate

GetCertificateWithPolicy retrieves the latest version of a certificate stored in the Key Vault along with its CertificatePolicy.

KeyVaultCertificateWithPolicy certificateWithPolicy = client.GetCertificate("MyCertificate");

GetCertificate retrieves a specific version of a certificate in the vault.

KeyVaultCertificate certificate = client.GetCertificateVersion(certificateWithPolicy.Name, certificateWithPolicy.Properties.Version);

Update an existing Certificate

UpdateCertificate updates a certificate stored in the Key Vault.

CertificateProperties certificateProperties = new CertificateProperties(certificate.Id);
certificateProperties.Tags["key1"] = "value1";

KeyVaultCertificate updated = client.UpdateCertificateProperties(certificateProperties);

List certificates

GetCertificates enumerates the certificates in the vault, returning select properties of the certificate. Sensitive fields of the certificate will not be returned. This operation requires the certificates/list permission.

Pageable<CertificateProperties> allCertificates = client.GetPropertiesOfCertificates();

foreach (CertificateProperties certificateProperties in allCertificates)
{
    Console.WriteLine(certificateProperties.Name);
}

Delete a certificate

DeleteCertificate deletes all versions of a certificate stored in the Key Vault. When soft-delete is not enabled for the Key Vault, this operation permanently deletes the certificate. If soft delete is enabled the certificate is marked for deletion and can be optionally purged or recovered up until its scheduled purge date.

DeleteCertificateOperation operation = client.StartDeleteCertificate("MyCertificate");

// You only need to wait for completion if you want to purge or recover the certificate.
// You should call `UpdateStatus` in another thread or after doing additional work like pumping messages.
while (!operation.HasCompleted)
{
    Thread.Sleep(2000);

    operation.UpdateStatus();
}

DeletedCertificate secret = operation.Value;
client.PurgeDeletedCertificate(secret.Name);

Create a certificate asynchronously

The asynchronous APIs are identical to their synchronous counterparts, but return with the typical "Async" suffix for asynchronous methods and return a Task.

This example creates a certificate in the Key Vault with the specified optional arguments.

// Create a certificate. This starts a long running operation to create and sign the certificate.
CertificateOperation operation = await client.StartCreateCertificateAsync("MyCertificate", CertificatePolicy.Default);

// You can await the completion of the create certificate operation.
KeyVaultCertificateWithPolicy certificate = await operation.WaitForCompletionAsync();

List certificates asynchronously

Listing certificate does not rely on awaiting the GetPropertiesOfCertificatesAsync method, but returns an AsyncPageable<CertificateProperties> that you can use with the await foreach statement:

AsyncPageable<CertificateProperties> allCertificates = client.GetPropertiesOfCertificatesAsync();

await foreach (CertificateProperties certificateProperties in allCertificates)
{
    Console.WriteLine(certificateProperties.Name);
}

Delete a certificate asynchronously

When deleting a certificate asynchronously before you purge it, you can await the WaitForCompletionAsync method on the operation. By default, this loops indefinitely but you can cancel it by passing a CancellationToken.

DeleteCertificateOperation operation = await client.StartDeleteCertificateAsync("MyCertificate");

// You only need to wait for completion if you want to purge or recover the certificate.
await operation.WaitForCompletionAsync();

DeletedCertificate secret = operation.Value;
await client.PurgeDeletedCertificateAsync(secret.Name);

Troubleshooting

General

When you interact with the Azure Key Vault Certificate client library using the .NET SDK, errors returned by the service correspond to the same HTTP status codes returned for REST API requests.

For example, if you try to retrieve a Key that doesn't exist in your Key Vault, a 404 error is returned, indicating Not Found.

try
{
    KeyVaultCertificateWithPolicy certificateWithPolicy = client.GetCertificate("SomeCertificate");
}
catch (RequestFailedException ex)
{
    Console.WriteLine(ex.ToString());
}

You will notice that additional information is logged, like the Client Request ID of the operation.

Message:
    Azure.RequestFailedException : Service request failed.
    Status: 404 (Not Found)
Content:
    {"error":{"code":"CertificateNotFound","message":"Certificate not found: MyCertificate"}}

Headers:
    Cache-Control: no-cache
    Pragma: no-cache
    Server: Microsoft-IIS/10.0
    x-ms-keyvault-region: westus
    x-ms-request-id: 625f870e-10ea-41e5-8380-282e5cf768f2
    x-ms-keyvault-service-version: 1.1.0.866
    x-ms-keyvault-network-info: addr=131.107.174.199;act_addr_fam=InterNetwork;
    X-AspNet-Version: 4.0.30319
    X-Powered-By: ASP.NET
    Strict-Transport-Security: max-age=31536000;includeSubDomains
    X-Content-Type-Options: nosniff
    Date: Tue, 18 Jun 2019 16:02:11 GMT
    Content-Length: 75
    Content-Type: application/json; charset=utf-8
    Expires: -1

Next steps

Key Vault Certificates client library samples are available to you in this GitHub repository. These samples provide example code for additional scenarios commonly encountered while working with Key Vault:

  • HelloWorld.cs and HelloWorldAsync.cs - for working with Azure Key Vault certificates, including:

    • Create a certificate
    • Get an existing certificate
    • Update an existing certificate
    • Delete a certificate

  • GetCertificates.cs and GetCertificatesAsync.cs - Example code for working with Key Vault certificates, including:

    • Create certificates
    • List all certificates in the Key Vault
    • List versions of a specified certificate
    • Delete certificates from the Key Vault
    • List deleted certificates in the Key Vault

Additional Documentation

Contributing

This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit https://cla.microsoft.com.

When you submit a pull request, a CLA-bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., label, comment). Simply follow the instructions provided by the bot. You will only need to do this once across all repos using our CLA.

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact [email protected] with any additional questions or comments.

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