Add and manage TLS/SSL certificates in Azure App Service

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Note

Starting June 1, 2024, all newly created App Service apps will have the option to generate a unique default hostname using the naming convention <app-name>-<random-hash>.<region>.chinacloudsites.cn. Existing app names will remain unchanged.

Example: myapp-ds27dh7271aah175.westus-01.chinacloudsites.cn

You can add digital security certificates to use in your application code or to help secure custom DNS names in Azure App Service, which provides a highly scalable, self-patching web hosting service. Currently called Transport Layer Security (TLS) certificates, also previously known as Secure Socket Layer (SSL) certificates, these private or public certificates help you secure internet connections by encrypting data sent between your browser, websites that you visit, and the website server.

The following table lists the options for you to add certificates in App Service:

Option Description
Import a certificate from Key Vault Useful if you use Azure Key Vault to manage your PKCS12 certificates. See Private certificate requirements.
Upload a private certificate If you already have a private certificate from a third-party provider, you can upload it. See Private certificate requirements.
Upload a public certificate Public certificates aren't used to secure custom domains, but you can load them into your code if you need them to access remote resources.

Prerequisites

Private certificate requirements

If you choose to upload or import a private certificate to App Service, your certificate must meet the following requirements:

  • Exported as a password-protected PFX file, encrypted using triple DES
  • Contains private key at least 2048 bits long
  • Contains all intermediate certificates and the root certificate in the certificate chain

If you want to help secure a custom domain in a TLS binding, the certificate must meet these additional requirements:

  • Contains an Extended Key Usage for server authentication (OID = 1.3.6.1.5.5.7.3.1)
  • Signed by a trusted certificate authority

Note

Elliptic Curve Cryptography (ECC) certificates work with App Service but aren't covered by this article. For the exact steps to create ECC certificates, work with your certificate authority.

Note

After you add a private certificate to an app, the certificate is stored in a deployment unit that's bound to the App Service plan's resource group, region, and operating system combination, internally called a webspace. That way, the certificate is accessible to other apps in the same resource group, region, and OS combination. Private certificates uploaded or imported to App Service are shared with App Services in the same deployment unit.

You can add up to 1000 private certificates per webspace.

Import a certificate from Key Vault

If you use Azure Key Vault to manage your certificates, you can import a PKCS12 certificate into App Service from Key Vault if you met the requirements.

Authorize App Service to read from the vault

By default, the App Service resource provider doesn't have access to your key vault. To use a key vault for a certificate deployment, you must authorize read access for the resource provider (App Service) to the key vault. You can grant access either with access policy or RBAC.

Import a certificate from your vault to your app

  1. In the Azure portal, from the left menu, select App Services > <app-name>.

  2. From your app's navigation menu, select Certificates > Bring your own certificates (.pfx) > Add certificate.

  3. In Source, select Import from Key Vault.

  4. Select Select key vault certificate.

    Screenshot of the app management page with 'Certificates', 'Bring your own certificates (.pfx)', and 'Import from Key Vault' selected.

  5. To help you select the certificate, use the following table:

    Setting Description
    Subscription The subscription associated with the key vault.
    Key vault The key vault that has the certificate you want to import.
    Certificate From this list, select a PKCS12 certificate that's in the vault. All PKCS12 certificates in the vault are listed with their thumbprints, but not all are supported in App Service.

  6. When finished with your selection, select Select, Validate, and then Add.

    When the operation completes, the certificate appears in the Bring your own certificates list. If the import fails with an error, the certificate doesn't meet the requirements for App Service.

    Screenshot of 'Bring your own certificates (.pfx)' pane with imported certificate listed.

    Note

    If you update your certificate in Key Vault with a new certificate, App Service automatically syncs your certificate within 24 hours.

  7. To helps secure custom domain with this certificate, you still have to create a certificate binding. Follow the steps in Secure a custom DNS name with a TLS/SSL binding in Azure App Service.

Upload a private certificate

After you get a certificate from your certificate provider, make the certificate ready for App Service by following the steps in this section.

Merge intermediate certificates

If your certificate authority gives you multiple certificates in the certificate chain, you must merge the certificates following the same order.

  1. In a text editor, open each received certificate.

  2. To store the merged certificate, create a file named mergedcertificate.crt.

  3. Copy the content for each certificate into this file. Make sure to follow the certificate sequence specified by the certificate chain, starting with your certificate and ending with the root certificate, for example:

    -----BEGIN CERTIFICATE-----
<your entire Base64 encoded SSL certificate>
-----END CERTIFICATE-----

-----BEGIN CERTIFICATE-----
<The entire Base64 encoded intermediate certificate 1>
-----END CERTIFICATE-----

-----BEGIN CERTIFICATE-----
<The entire Base64 encoded intermediate certificate 2>
-----END CERTIFICATE-----

-----BEGIN CERTIFICATE-----
<The entire Base64 encoded root certificate>
-----END CERTIFICATE-----

Export the merged private certificate to PFX

Now, export your merged TLS/SSL certificate with the private key that was used to generate your certificate request. If you generated your certificate request using OpenSSL, then you created a private key file.

Note

OpenSSL v3 changed the default cipher from 3DES to AES256, but this can be overridden on the command line: -keypbe PBE-SHA1-3DES -certpbe PBE-SHA1-3DES -macalg SHA1. OpenSSL v1 uses 3DES as the default, so the PFX files generated are supported without any special modifications.

  1. To export your certificate to a PFX file, run the following command, but replace the placeholders <private-key-file> and <merged-certificate-file> with the paths to your private key and your merged certificate file.

    openssl pkcs12 -export -out myserver.pfx -inkey <private-key-file> -in <merged-certificate-file>

  2. When you're prompted, specify a password for the export operation. When you upload your TLS/SSL certificate to App Service later, you must provide this password.

  3. If you used IIS or Certreq.exe to generate your certificate request, install the certificate to your local computer, and then export the certificate to a PFX file.

Upload the certificate to App Service

You're now ready upload the certificate to App Service.

  1. In the Azure portal, from the left menu, select App Services > <app-name>.

  2. From your app's navigation menu, select Certificates > Bring your own certificates (.pfx) > Upload Certificate.

    Screenshot of the app management page with 'Certificates', 'Bring your own certificates (.pfx)', and 'Upload Certificate' selected.

  3. To help you upload the .pfx certificate, use the following table:

    Setting Description
    PFX certificate file Select your .pfx file.
    Certificate password Enter the password that you created when you exported the PFX file.
    Certificate friendly name The certificate name that will be shown in your web app.

  4. When finished with your selection, select Select, Validate, and then Add.

    When the operation completes, the certificate appears in the Bring your own certificates list.

    Screenshot of the 'Bring your own certificates' pane with the uploaded certificate listed.

  5. To provide security for a custom domain with this certificate, you still have to create a certificate binding. Follow the steps in Secure a custom DNS name with a TLS/SSL binding in Azure App Service.

Upload a public certificate

Public certificates are supported in the .cer format.

Note

After you upload a public certificate to an app, it's only accessible by the app it's uploaded to. Public certificates must be uploaded to each individual web app that needs access. For App Service Environment specific scenarios, refer to the documentation for certificates and the App Service Environment.

You can upload up to 1000 public certificates per App Service Plan.

  1. In the Azure portal, from the left menu, select App Services > <app-name>.

  2. From your app's navigation menu, select Certificates > Public key certificates (.cer) > Add certificate.

  3. To help you upload the .cer certificate, use the following table:

    Setting Description
    CER certificate file Select your .cer file.
    Certificate friendly name The certificate name that will be shown in your web app.

  4. When you're done, select Add.

    Screenshot of the app management page. It shows the public key certificate to upload and its name.

  5. After the certificate is uploaded, copy the certificate thumbprint, and then review Make the certificate accessible.

Renew an expiring certificate

Before a certificate expires, make sure to add the renewed certificate to App Service, and update any certificate bindings where the process depends on the certificate type. For example, a certificate imported from Key Vault, including an App Service certificate, automatically syncs to App Service every 24 hours and updates the TLS/SSL binding when you renew the certificate. For an uploaded certificate, there's no automatic binding update. Based on your scenario, review the corresponding section:

Renew an uploaded certificate

When you replace an expiring certificate, the way you update the certificate binding with the new certificate might adversely affect the user experience. For example, your inbound IP address might change when you delete a binding, even if that binding is IP-based. This result is especially impactful when you renew a certificate that's already in an IP-based binding. To avoid a change in your app's IP address, and to avoid downtime for your app due to HTTPS errors, follow these steps in the specified sequence:

  1. Upload the new certificate.

  2. Go to the Custom domains page for your app, select the ... button, and then select Update binding.

  3. Select the new certificate and then select Update.

  4. Delete the existing certificate.

Renew a certificate imported from Key Vault

To renew a certificate that you imported into App Service from Key Vault, review Renew your Azure Key Vault certificate.

After the certificate renews in your key vault, App Service automatically syncs the new certificate and updates any applicable certificate binding within 24 hours. To sync manually, follow these steps:

  1. Go to your app's Certificate page.

  2. Under Bring your own certificates (.pfx), select the ... button for the imported key vault certificate, and then select Sync.

Frequently asked questions

How can I automate adding a bring-your-own certificate to an app?

Can I use a private CA (certificate authority) certificate for inbound TLS on my app?

You can use a private CA certificate for inbound TLS in App Service Environment version 3. This isn't possible in App Service (multi-tenant).

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