Deploy custom certificate

Note

Only available on Enterprise plans.

Enterprise customers who do not wish to install the Cloudflare certificate have the option to upload their own root certificate to Cloudflare. This feature is sometimes referred to as Bring Your Own Public Key Infrastructure (BYOPKI). Gateway will use your uploaded certificate to encrypt all sessions between the end user and Gateway, enabling all HTTPS inspection features that previously required the Cloudflare certificate. You can upload multiple certificates to your account, but only one can be active at any given time. You also need to upload a private key to intercept domains with JIT certificates and to enable the block page.

Caution

Custom certificates are limited to use between your users and the Gateway proxy. Connections between Gateway and the origin server will use the Cloudflare certificate.

Generate a custom root CA

Before you generate a custom root CA, make sure you have OpenSSL installed.

1. Open a terminal.

2. Create a directory for the root CA and change into it.

   $ mkdir -p /root/customca
   $ cd /root/customca

3. Generate a private key for the root CA.

   $ openssl genrsa -out <CUSTOM-ROOT-PRIVATE-KEY>.pem 2048

4. Generate a self-signed root certificate.

   $ openssl req -x509 -sha256 -new -nodes -key <CUSTOM-ROOT-PRIVATE-KEY>.pem -days 365 -out <CUSTOM-ROOT-CERT>.pem

When preparing your certificate and private key for upload, be sure to remove any unwanted characters, such as mismatching subdomains in the certificate’s common name. To review the private key, run the following command:

$ openssl rsa -in <CUSTOM-ROOT-PRIVATE-KEY>.pem -text

To review the certificate, run the following command:

$ openssl x509 -in <CUSTOM-ROOT-CERT>.pem -text

Deploy a custom root certificate

1. Verify that the certificate is installed on your devices.

2. Use the Upload mTLS certificate endpoint to upload the certificate and private key to Cloudflare. The certificate must be a root CA, formatted as a single string with \n replacing the line breaks.

   curl "https://api.cloudflare.com/client/v4/accounts/{account_id}/mtls_certificates" \
   --header "X-Auth-Email: <EMAIL>" \
   --header "X-Auth-Key: <API_KEY>" \
   --header "Content-Type: application/json" \
   --data '{
     "name": "example_ca_cert",
     "certificates": "-----BEGIN CERTIFICATE-----\nXXXXX\n-----END CERTIFICATE-----",
     "private_key": "-----BEGIN PRIVATE KEY-----\nXXXXX\n-----END PRIVATE KEY-----",
     "ca": true
   }'

   The response will return a UUID for the certificate:

   {
     "success": true,
     "errors": [],
     "messages": [],
     "result": {
       "id": "2458ce5a-0c35-4c7f-82c7-8e9487d3ff60",
       "name": "example_ca_cert",
       "issuer": "O=Example Inc.,L=California,ST=San Francisco,C=US",
       "signature": "SHA256WithRSA"
       ...
     }
   }

3. Enable the certificate in Gateway with its UUID.

   curl --request PATCH \
   "https://api.cloudflare.com/client/v4/accounts/{account_id}/gateway/configuration" \
   --header "X-Auth-Email: <EMAIL>" \
   --header "X-Auth-Key: <API_KEY>" \
   --header "Content-Type: application/json" \
   --data '{
     "settings": {
       "custom_certificate": {
         "enabled": true,
         "id": "2458ce5a-0c35-4c7f-82c7-8e9487d3ff60"
       }
     }
   }'

   The response will show the current status of the certificate:

   {
   "success": true,
   "errors": [],
   "messages": [],
   "result": {
         "settings": {
               "antivirus": {...},
               "block_page": {...},
               "custom_certificate":
               {
                   "enabled": true,
                   "id": "2458ce5a-0c35-4c7f-82c7-8e9487d3ff60",
                   "binding_status": "pending_deployment",
                   "qs_pack_id": "50a78g31-a5b5-4k58d-a6ed-b0ac17da9k05"
               },
               "tls_decrypt": {...},
               "activity_log": {...},
               "browser_isolation": {...},
               "fips": {...},
           },
       },
       "created_at": "2014-01-01T05:20:00.12345Z",
       "updated_at": "2014-01-01T05:20:00.12345Z"
   }

Once binding_status changes to active, Gateway will sign your traffic using the custom root certificate and private key. If you disable the custom certificate, Gateway will revert to the default Cloudflare certificate.

Private key visibility

When you upload a private key to Zero Trust, Cloudflare encrypts the key and stores it at rest. Only your delegated apps have the necessary decryption keys to decrypt the private key. You will not be able to retrieve the private key after upload.

Troubleshoot HTTP errors

If Gateway returns an HTTP Response Code: 526 after deploying a custom certificate, you can troubleshoot errors with our FAQ.