Create a private CA in AWS Private CA

You can use the procedures in this section to create either root CAs or subordinate CAs, resulting in an auditable hierarchy of trust relationships that matches your organizational needs. You can create a CA using the AWS Management Console, the PCA portion of the AWS CLI, or AWS CloudFormation.

For information about updating the configuration of a CA that you have already created, see Update a private CA in AWS Private Certificate Authority.

For information about using a CA to sign end-entity certificates for your users, devices, and applications, see Issue private end-entity certificates.

Console

To create a private CA using the console

1. Complete the following steps to create a private CA using the AWS Management Console.

   To get started using the console

   Sign in to your AWS account and open the AWS Private CA console at https://console.aws.amazon.com/acm-pca/home.

   • If you are opening the console in a Region where you have no private CAs, the introductory page appears. Choose Create a private CA.

   • If you are opening the console in a Region where you have already created a CA, the Private certificate authorities page opens with a list of your CAs. Choose Create CA.

2. Under Mode options, choose the expiration mode of the certificates that your CA issues.

   • General-purpose – Issues certificates that can be configured with any expiration date. This is the default.

   • Short-lived certificate – Issues certificates with a maximum validity period of seven days. A short validity period can substitute in some cases for a revocation mechanism.

3. On the Type options section of the console, choose the type of private certificate authority that you want to create.

   • Choosing Root establishes a new CA hierarchy. This CA is backed by a self-signed certificate. It serves as the ultimate signing authority for other CAs and end-entity certificates in the hierarchy.

   • Choosing Subordinate creates a CA that must be signed by a parent CA above it in the hierarchy. Subordinate CAs are typically used to create other subordinate CAs or to issue end-entity certificates to users, computers, and applications.

     Note

     AWS Private CA provides an automated signing process when your subordinate CA's parent CA is also hosted by AWS Private CA. All you do is choose the parent CA to use.

     Your subordinate CA might need to be signed by an external trust services provider. If so, AWS Private CA provides you with a certificate signing request (CSR) that you must download and use to obtain a signed CA certificate. For more information, see Install a subordinate CA certificate signed by an external parent CA.

4. Under Subject distinguished name options, configure the subject name of your private CA. You must enter a value for at least one of the following options:

   • Organization (O) – For example, a company name

   • Organization Unit (OU) – For example, a division within a company

   • Country name (C) – A two-letter country code

   • State or province name – Full name of a state or province

   • Locality name – The name of a city

   • Common Name (CN) – A human-readable string to identify the CA.

   Note

   You can further customize the subject name of a certificate by applying an APIPassthrough template at the time of issue. For more information and a detailed example, see Issue a certificate with a custom subject name using an APIPassthrough template.

   Because the backing certificate is self-signed, the subject information that you provide for a private CA is probably more sparse than what a public CA would contain. For more information about each of the values that make up a subject distinguished name, see RFC 5280.

5. Under Key algorithm options, choose the key algorithm and the bit-size of the key. The default value is an RSA algorithm with a 2048-bit key length. You can choose from the following algorithms:

   • RSA 2048

   • RSA 4096

   • ECDSA P256

   • ECDSA P384

6. Under Certificate revocation options, you can select from two methods of sharing revocation status with clients that use your certificates:

   • Activate CRL distribution

   • Turn on OCSP

   You can configure either, neither, or both of these revocation options for your CA. Although optional, managed revocation is recommended as a best practice. Before completing this step, see Plan your AWS Private CA certificate revocation method for information about the advantages of each method, the preliminary setup that might be required, and additional revocation features.

   Note

   If you create your CA without configuring revocation, you can always configure it later. For more information, see Update a private CA in AWS Private Certificate Authority.

   To configure Certificate revocation options, perform the following steps.

   1. Under Certificate revocation options, choose Activate CRL distribution.

   2. To create an Amazon S3 bucket for your CRL entries, choose Create a new S3 bucket and type a unique bucket name. (You do not need to include the path to the bucket.) Otherwise, under S3 bucket URI, choose an existing bucket from the list.

      When you create a new bucket through the console, AWS Private CA attempts to attach the required access policy to the bucket, and to disable the S3 default Block Public Access (BPA) setting on it. If you instead specify an existing bucket, you must ensure that BPA is disabled for the account and for the bucket. Otherwise, the operation to create the CA fail. If the CA is created successfully, you must still manually attach a policy to it before you can begin generating CRLs. Use one of the policy patterns described in Access policies for CRLs in Amazon S3 . For more information, see Adding a bucket policy using the Amazon S3 console.

      Important

      An attempt to create a CA using the AWS Private CA console fails if all of the following conditions apply:

      • You are setting up a CRL.

      • You ask AWS Private CA to create an S3 bucket automatically.

      • You are enforcing BPA settings in S3.

      In this situation, the console creates a bucket, but attempts and fails to make it publicly accessible. Check your Amazon S3 settings if this occurs, disable BPA as needed, and then repeat the procedure for creating a CA. For more information, see Blocking public access to your Amazon S3 storage.

   3. Expand CRL settings for additional configuration options.

      • Add a Custom CRL Name to create an alias for your Amazon S3 bucket. This name is contained in certificates issued by the CA in the “CRL Distribution Points" extension that is defined by RFC 5280.

      • Type the Validity in days your CRL will remain valid. The default value is 7 days. For online CRLs, a validity period of 2-7 days is common. AWS Private CA tries to regenerate the CRL at the midpoint of the specified period.

   4. Expand S3 settings for optional configuration of Bucket versioning and Bucket access logging.

7. For Certificate revocation options, choose Turn on OCSP.

   1. In the Custom OCSP endpoint - optional field, you can provide a fully qualified domain name (FQDN) for a non-Amazon OCSP endpoint.

      When you provide an FQDN in this field, AWS Private CA inserts the FQDN into the Authority Information Access extension of each issued certificate in place of the default URL for the AWS OCSP responder. When an endpoint receives a certificate containing the custom FQDN, it queries that address for an OCSP response. For this mechanism to work, you need to take two additional actions:

      • Use a proxy server to forward traffic that arrives at your custom FQDN to the AWS OCSP responder.

      • Add a corresponding CNAME record to your DNS database.

      Tip

      For more information about implementing a complete OCSP solution using a custom CNAME, see Customize OCSP URL for AWS Private CA.

      For example, here is a CNAME record for customized OCSP as it would appear in Amazon Route 53.

      Record name	Type	Routing policy	Differentiator	Value/Route traffic to
      alternative.example.com	CNAME	Simple	-	proxy.example.com

      Note

      The value of the CNAME must not include a protocol prefix such as "http://" or "https://".

8. Under Add tags, you can optionally tag your CA. Tags are key-value pairs that serve as metadata for identifying and organizing AWS resources. For a list of AWS Private CA tag parameters and for instructions on how to add tags to CAs after creation, see Add tags for your private CA.

   Note

   To attach tags to a private CA during the creation procedure, a CA administrator must first associate an inline IAM policy with the CreateCertificateAuthority action and explicitly allow tagging. For more information, see Tag-on-create: Attaching tags to a CA at the time of creation.

9. Under CA permissions options, you can optionally delegate automatic renewal permissions to the AWS Certificate Manager service principal. ACM can only automatically renew private end-entity certificates generated by this CA if this permission is granted. You can assign renewal permissions at any time with the AWS Private CA CreatePermission API or create-permission CLI command.

   The default is to enable these permissions.

   Note

   AWS Certificate Manager does not support the automatic renewal of short-lived certificates.

10. Under Pricing, confirm that you understand the pricing for a private CA.

    Note

    For the latest AWS Private CA pricing information, see AWS Private Certificate Authority Pricing. You can also use the AWS pricing calculator to estimate costs.

11. Choose Create CA after you have checked all of the entered information for accuracy. The details page for the CA opens and displays its status as Pending certificate.

    Note

    While on the details page, you can finish configuring your CA by choosing Actions, Install CA certificate, or you can return later to the Private certificate authorities list and complete the installation procedure that applies in your case:

    • Install a root CA certificate

    • Install a subordinate CA certificate hosted by AWS Private CA

    • Install a subordinate CA certificate signed by an external parent CA

CLI

Use the create-certificate-authority command to create a private CA. You must specify the CA configuration (containing algorithm and subject-name information), the revocation configuration (if you plan to use OCSP and/or a CRL), and the CA type (root or subordinate). The configuration and revocation configuration details are contained in two files that you supply as arguments to the command. Optionally, you can also configure the CA usage mode (for issuing standard or short-lived certificates), attach tags, and provide an idempotency token.

If you are configuring a CRL, you must have a secured Amazon S3 bucket in place before you issue the create-certificate-authority command. For more information, see Access policies for CRLs in Amazon S3 .

The CA configuration file specifies the following information:

• The name of the algorithm

• The key size to be used to create the CA private key

• The type of signing algorithm that the CA uses to sign

• X.500 subject information

The revocation configuration for OCSP defines an OcspConfiguration object with the following information:

• The Enabled flag set to "true".

• (Optional) A custom CNAME declared as a value for OcspCustomCname.

The revocation configuration for a CRL defines a CrlConfiguration object with the following information:

• The Enabled flag set to "true".

• The CRL expiration period in days (the validity period of the CRL).

• The Amazon S3 bucket that will contain the CRL.

• (Optional) An S3ObjectAcl value that determines whether the CRL is publicly accessible. In the example presented here, public access is blocked. For more information, see Enable S3 Block Public Access (BPA) with CloudFront.

• (Optional) A CNAME alias for the S3 bucket that is included in certificates issued by the CA. If the CRL is not publicly accessible, this will point to a distribution mechanism such as Amazon CloudFront.

• (Optional) A CrlDistributionPointExtensionConfiguration object with the following information:

  • The OmitExtension flag set to "true" or "false". This controls whether the default value for the CDP extension will be written to a certificate issued by the CA. For more information about the CDP extension, see Determining the CRL Distribution Point (CDP) URI . A CustomCname cannot be set if OmitExtension is "true".

Note

You can enable both revocation mechanisms on the same CA by defining both an OcspConfiguration object and a CrlConfiguration object. If you supply no --revocation-configuration parameter, both mechanisms are disabled by default. If you need revocation validation support later, see Updating a CA (CLI).

See the following section for CLI examples.

CLI examples for creating a private CA

The following examples assume that you have set up your .aws configuration directory with a valid default Region, endpoint, and credentials. For information about configuring your AWS CLI environment, see Configuration and credential file settings. For readability, we supply the CA configuration and revocation input as JSON files in the example commands. Modify the example files as needed for your use.

All of the examples use the following ca_config.txt configuration file unless otherwise stated.

File: ca_config.txt

{
   "KeyAlgorithm":"RSA_2048",
   "SigningAlgorithm":"SHA256WITHRSA",
   "Subject":{
      "Country":"US",
      "Organization":"Example Corp",
      "OrganizationalUnit":"Sales",
      "State":"WA",
      "Locality":"Seattle",
      "CommonName":"www.example.com"
   }
}

Example 1: Create a CA with OCSP enabled

In this example, the revocation file enables default OCSP support, which uses the AWS Private CA responder to check certificate status.

File: revoke_config.txt for OCSP

{
   "OcspConfiguration":{
      "Enabled":true
   }
}

Command

$ aws acm-pca create-certificate-authority \
     --certificate-authority-configuration file://ca_config.txt \
     --revocation-configuration file://revoke_config.txt \
     --certificate-authority-type "ROOT" \
     --idempotency-token 01234567 \
     --tags Key=Name,Value=MyPCA

If successful, this command outputs the Amazon Resource Name (ARN) of the new CA.

{
	"CertificateAuthorityArn":"arn:aws:acm-pca:region:account:
       certificate-authority/CA_ID"
}

Command

$ aws acm-pca create-certificate-authority \
	--certificate-authority-configuration file://ca_config.txt \
	--revocation-configuration file://revoke_config.txt \
	--certificate-authority-type "ROOT" \
	--idempotency-token 01234567 \
	--tags Key=Name,Value=MyPCA-2

If successful, this command outputs the Amazon Resource Name (ARN) of the CA.

{
    "CertificateAuthorityArn":"arn:aws:acm-pca:us-east-1:111122223333:certificate-authority/11223344-1234-1122-2233-112233445566"
}

Use the following command to inspect the configuration of your CA.

$ aws acm-pca describe-certificate-authority \
      --certificate-authority-arn "arn:aws:acm-pca:us-east-1:111122223333:certificate-authority/11223344-1234-1122-2233-112233445566" \
      --output json

This description should contain the following section.

"RevocationConfiguration": {
   ...
   "OcspConfiguration": {
      "Enabled": true
   }
   ...
}

Example 2: Create a CA with OCSP and a custom CNAME enabled

In this example, the revocation file enables customized OCSP support. The OcspCustomCname parameter takes a fully qualified domain name (FQDN) as its value.

When you provide an FQDN in this field, AWS Private CA inserts the FQDN into the Authority Information Access extension of each issued certificate in place of the default URL for the AWS OCSP responder. When an endpoint receives a certificate containing the custom FQDN, it queries that address for an OCSP response. For this mechanism to work, you need to take two additional actions:

For example, here is a CNAME record for customized OCSP as it would appear in Amazon Route 53.

File: revoke_config.txt for OCSP

{
   "OcspConfiguration":{
      "Enabled":true,
      "OcspCustomCname":"alternative.example.com"
   }
}

Command

$ aws acm-pca create-certificate-authority \
	--certificate-authority-configuration file://ca_config.txt \
	--revocation-configuration file://revoke_config.txt \
	--certificate-authority-type "ROOT" \
	--idempotency-token 01234567 \
	--tags Key=Name,Value=MyPCA-3

If successful, this command outputs the Amazon Resource Name (ARN) of the CA.

{
    "CertificateAuthorityArn":"arn:aws:acm-pca:us-east-1:111122223333:certificate-authority/11223344-1234-1122-2233-112233445566"
}

Use the following command to inspect the configuration of your CA.

$ aws acm-pca describe-certificate-authority \
      --certificate-authority-arn "arn:aws:acm-pca:us-east-1:111122223333:certificate-authority/11223344-1234-1122-2233-112233445566" \
      --output json

This description should contain the following section.

"RevocationConfiguration": {
   ...
   "OcspConfiguration": {
      "Enabled": true,
      "OcspCustomCname": "alternative.example.com"
   }
   ...
}

Example 3: Create a CA with an attached CRL

In this example, the revocation configuration defines CRL parameters.

File: revoke_config.txt

{
   "CrlConfiguration":{
      "Enabled":true,
      "ExpirationInDays":7,
      "S3BucketName":"amzn-s3-demo-bucket"
   }
}

Command

$ aws acm-pca create-certificate-authority \
      --certificate-authority-configuration file://ca_config.txt \
      --revocation-configuration file://revoke_config.txt \
      --certificate-authority-type "ROOT" \
      --idempotency-token 01234567 \
      --tags Key=Name,Value=MyPCA-1

If successful, this command outputs the Amazon Resource Name (ARN) of the CA.

{
    "CertificateAuthorityArn":"arn:aws:acm-pca:us-east-1:111122223333:certificate-authority/11223344-1234-1122-2233-112233445566"
}

Use the following command to inspect the configuration of your CA.

$ aws acm-pca describe-certificate-authority \
      --certificate-authority-arn "arn:aws:acm-pca:us-east-1:111122223333:certificate-authority/11223344-1234-1122-2233-112233445566" \
      --output json

This description should contain the following section.

"RevocationConfiguration": {
   ...
   "CrlConfiguration": {
      "Enabled": true,
      "ExpirationInDays": 7,
      "S3BucketName": "amzn-s3-demo-bucket"
   },
   ...
}

Example 4: Create a CA with an attached CRL and a custom CNAME enabled

In this example, the revocation configuration defines CRL parameters that include a custom CNAME.

File: revoke_config.txt

{
   "CrlConfiguration":{
      "Enabled":true,
      "ExpirationInDays":7,
      "CustomCname": "alternative.example.com",
      "S3BucketName":"amzn-s3-demo-bucket"
   }
}

Command

$ aws acm-pca create-certificate-authority \
      --certificate-authority-configuration file://ca_config.txt \
      --revocation-configuration file://revoke_config.txt \
      --certificate-authority-type "ROOT" \
      --idempotency-token 01234567 \
      --tags Key=Name,Value=MyPCA-1

If successful, this command outputs the Amazon Resource Name (ARN) of the CA.

{
    "CertificateAuthorityArn":"arn:aws:acm-pca:us-east-1:111122223333:certificate-authority/11223344-1234-1122-2233-112233445566"
}

Use the following command to inspect the configuration of your CA.

$ aws acm-pca describe-certificate-authority \
      --certificate-authority-arn "arn:aws:acm-pca:us-east-1:111122223333:certificate-authority/11223344-1234-1122-2233-112233445566" \
      --output json

This description should contain the following section.

"RevocationConfiguration": {
   ...
   "CrlConfiguration": {
      "Enabled": true,
      "ExpirationInDays": 7,
      "CustomCname": "alternative.example.com",
      "S3BucketName": "amzn-s3-demo-bucket",
   ...
   }
}

Example 5: Create a CA and specify the usage mode

In this example, the CA usage mode is specified when creating a CA. If unspecified, the usage mode parameter defaults to GENERAL_PURPOSE. In this example, the parameter is set to SHORT_LIVED_CERTIFICATE, which means that the CA will issue certificates with a maximum validity period of seven days. In situations where it is inconvenient to configure revocation, a short-lived certificate that has been compromised quickly expires as part of normal operations. Consequently, this example CA lacks a revocation mechanism.

$ aws acm-pca create-certificate-authority \
	     --certificate-authority-configuration file://ca_config.txt \
	     --certificate-authority-type "ROOT" \
	     --usage-mode SHORT_LIVED_CERTIFICATE \
	     --tags Key=usageMode,Value=SHORT_LIVED_CERTIFICATE

Use the describe-certificate-authority command in the AWS CLI to display details about the resulting CA, as shown in the following command:

$ aws acm-pca describe-certificate-authority \
	     --certificate-authority-arn arn:aws:acm:region:account:certificate-authority/CA_ID

{
	   "CertificateAuthority":{
	      "Arn":"arn:aws:acm-pca:region:account:certificate-authority/CA_ID",
	      "CreatedAt":"2022-09-30T09:53:42.769000-07:00",
	      "LastStateChangeAt":"2022-09-30T09:53:43.784000-07:00",
	      "Type":"ROOT",
	      "UsageMode":"SHORT_LIVED_CERTIFICATE",
	      "Serial":"serial_number",
	      "Status":"PENDING_CERTIFICATE",
	      "CertificateAuthorityConfiguration":{
	         "KeyAlgorithm":"RSA_2048",
	         "SigningAlgorithm":"SHA256WITHRSA",
	         "Subject":{
	            "Country":"US",
	            "Organization":"Example Corp",
	            "OrganizationalUnit":"Sales",
	            "State":"WA",
	            "Locality":"Seattle",
	            "CommonName":"www.example.com"
	         }
	      },
	      "RevocationConfiguration":{
	         "CrlConfiguration":{
	            "Enabled":false
	         },
	         "OcspConfiguration":{
	            "Enabled":false
	         }
	      },
	...

Example 6: Create a CA for Active Directory login

You can create a private CA suitable for use in the Enterprise NTAuth store of Microsoft Active Directory (AD), where it can issue card-logon or domain-controller certificates. For information about importing a CA certificate into AD, see How to import third-party certification authority (CA) certificates into the Enterprise NTAuth store.

The Microsoft certutil tool can be used to publish CA certificates in AD by invoking the -dspublish option. A certificate published to AD with certutil is trusted across the entire forest. Using group policy, you can also limit trust to a subset of the entire forest, for example, a single domain or a group of computers in a domain. For logon to work, the issuing CA must also be published in the NTAuth store. For more information, see Distribute Certificates to Client Computers by Using Group Policy.

This example uses the following ca_config_AD.txt configuration file.

File: ca_config_AD.txt

{
   "KeyAlgorithm":"RSA_2048",
   "SigningAlgorithm":"SHA256WITHRSA",
   "Subject":{
      "CustomAttributes":[
         {
            "ObjectIdentifier":"2.5.4.3",
            "Value":"root CA"
         },
         {
            "ObjectIdentifier":"0.9.2342.19200300.100.1.25",
            "Value":"example"
         },
         {
            "ObjectIdentifier":"0.9.2342.19200300.100.1.25",
            "Value":"com"
         }
      ]
   }
}

Command

$ aws acm-pca create-certificate-authority \
	     --certificate-authority-configuration file://ca_config_AD.txt \
	     --certificate-authority-type "ROOT" \
	     --tags Key=application,Value=ActiveDirectory

If successful, this command outputs the Amazon Resource Name (ARN) of the CA.

{
	"CertificateAuthorityArn":"arn:aws:acm-pca:us-east-1:111122223333:certificate-authority/11223344-1234-1122-2233-112233445566"
	}

Use the following command to inspect the configuration of your CA.

$ aws acm-pca describe-certificate-authority \
      --certificate-authority-arn "arn:aws:acm-pca:us-east-1:111122223333:certificate-authority/11223344-1234-1122-2233-112233445566" \
      --output json

This description should contain the following section.

...

"Subject":{
   "CustomAttributes":[
      {
         "ObjectIdentifier":"2.5.4.3",
         "Value":"root CA"
      },
      {
         "ObjectIdentifier":"0.9.2342.19200300.100.1.25",
         "Value":"example"
      },
      {
         "ObjectIdentifier":"0.9.2342.19200300.100.1.25",
         "Value":"com"
      }
   ]
}
...

Example 7: Create a Matter CA with an attached CRL and the CDP extension omitted from issued certificates

You can create a private CA suitable for issuing certificates for the Matter smart home standard. In this example, the CA configuration in ca_config_PAA.txt defines a Matter Product Attestation Authority (PAA) with the Vendor ID (VID) set to FFF1.

File: ca_config_PAA.txt

{
   "KeyAlgorithm":"EC_prime256v1",
   "SigningAlgorithm":"SHA256WITHECDSA",
   "Subject":{
      "Country":"US",
      "Organization":"Example Corp",
      "OrganizationalUnit":"SmartHome",
      "State":"WA",
      "Locality":"Seattle",
      "CommonName":"Example Corp Matter PAA",
	  "CustomAttributes":[
      {
        "ObjectIdentifier":"1.3.6.1.4.1.37244.2.1",
        "Value":"FFF1"
      }
    ]
  }
}

The revocation configuration enables CRLs, and configures the CA to omit the default CDP URL from any issued certificates.

File: revoke_config.txt

{
   "CrlConfiguration":{
      "Enabled":true,
      "ExpirationInDays":7,
      "S3BucketName":"amzn-s3-demo-bucket",
	  "CrlDistributionPointExtensionConfiguration":{
		"OmitExtension":true
	  }
   }
}

Command

$ aws acm-pca create-certificate-authority \
      --certificate-authority-configuration file://ca_config_PAA.txt \
      --revocation-configuration file://revoke_config.txt \
      --certificate-authority-type "ROOT" \
      --idempotency-token 01234567 \
      --tags Key=Name,Value=MyPCA-1

If successful, this command outputs the Amazon Resource Name (ARN) of the CA.

{
    "CertificateAuthorityArn":"arn:aws:acm-pca:us-east-1:111122223333:certificate-authority/11223344-1234-1122-2233-112233445566"
}

Use the following command to inspect the configuration of your CA.

$ aws acm-pca describe-certificate-authority \
      --certificate-authority-arn "arn:aws:acm-pca:us-east-1:111122223333:certificate-authority/11223344-1234-1122-2233-112233445566" \
      --output json

This description should contain the following section.

"RevocationConfiguration": {
   ...
   "CrlConfiguration": {
      "Enabled": true,
      "ExpirationInDays": 7,
      "S3BucketName": "amzn-s3-demo-bucket",
	  "CrlDistributionPointExtensionConfiguration":{
		"OmitExtension":true
	  }
   },
   ...
}
...