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Configuring CDN Credentials and Authentication cdn-credentials-authentication

Last update: Fri Oct 04 2024 00:00:00 GMT+0000 (Coordinated Universal Time)

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The Adobe-provided CDN has several features and services, some of which rely on credentials and authentication in order to ensure an appropriate level of enterprise security. By declaring rules in a configuration file deployed by using the Cloud Manager config pipeline, customers can configure, in a self-service way, the following:

  • The X-AEM-Edge-Key HTTP header value used by the Adobe CDN to validate requests coming from a Customer-managed CDN.
  • The API token used to purge resources in the CDN cache.
  • A list of username/password combinations that can access restricted content, by submitting a Basic Authentication form.

Each of these, including the configuration syntax, is described in its own section below.

There is a section on how to rotate keys, which is a good security practice.

Customer-managed CDN HTTP header value CDN-HTTP-value

As described in the CDN in AEM as a Cloud Service page, customers may choose to route traffic through their own CDN, which is referred to as the Customer CDN (also sometimes called BYOCDN).

As part of the setup, the Adobe CDN and the Customer CDN must agree on a value of the X-AEM-Edge-Key HTTP Header. This value is set on each request, at the Customer CDN, before it is routed to the Adobe CDN, which then validates that the value is as expected, so it can trust other HTTP headers, including those that help route the request to the appropriate AEM origin.

The X-AEM-Edge-Key value is referenced by the edgeKey1 and edgeKey2 properties in a file named cdn.yaml or similar, somewhere under a top-level config folder. Read Using Config Pipelines for details about the folder structure and how to deploy the configuration. The syntax is described in the example below.

WARNING
Direct access without a correct X-AEM-Edge-Key will be denied for all requests matching the condition (in the sample below that means all requests to the publish tier). If you need to gradually introduce authentication please see the Migrating safely to reduce the risk of blocked traffic section.
kind: "CDN"
version: "1"
metadata:
  envTypes: ["dev"]
data:
  authentication:
    authenticators:
      - name: edge-auth
        type: edge
        edgeKey1: ${{CDN_EDGEKEY_052824}}
        edgeKey2: ${{CDN_EDGEKEY_041425}}
    rules:
      - name: edge-auth-rule
        when: { reqProperty: tier, equals: "publish" }
        action:
          type: authenticate
          authenticator: edge-auth

See Using Config Pipelines for a description of the properties above the data node. The kind property value should be CDN and the version property should be set to 1.

See Configure and deploy HTTP Header validation CDN rule tutorial step for more details.

Additional properties include:

  • Data node that contains a child authentication node.

  • Under authentication, one authenticators node and one rules node, both of which are arrays.

  • Authenticators: Lets you declare a type of token or credential, which in this case is an edge key. It includes the following properties:

    • name - a descriptive string.
    • type - must be edge.
    • edgeKey1 - the value of the X-AEM-Edge-Key, which must reference a Cloud Manager secret-type environment variable. For the Service Applied field, select All. It is recommended that the value (for example,${{CDN_EDGEKEY_052824}}) reflects the day it was added.
    • edgeKey2 - used for the rotation of secrets, which is described in the rotating secrets section below. Define it similarly to edgeKey1. At least one of edgeKey1 and edgeKey2 must be declared.

  • Rules: Lets you declare which of the authenticators should be used, and whether it’s for the publish and/or preview tier. It includes:

    • name - a descriptive string.
    • when - a condition that determines when the rule should be evaluated, according to the syntax in the Traffic Filter Rules article. Typically, it will include a comparison of the current tier (for example., publish) so all live traffic is validated as routing through the customer CDN.
    • action - must specify “authenticate”, with the intended authenticator referenced.
NOTE
The Edge Key must be configured as a secret type Cloud Manager environment variable, before the configuration referencing it is deployed. It is recommended to use a unique random key of minimum 32 bytes length; for example, the Open SSL cryptographic library can generate a random key by executing the command openssl rand -hex 32.

Migrating safely to reduce the risk of blocked traffic migrating-safely

If your site is already live, exercise caution when migrating to customer-managed CDN since a misconfiguration can block public traffic; this is because only requests with the expected X-AEM-Edge-Key header value will be accepted by the Adobe CDN. An approach is recommended where an additional condition is temporarily included in the authentication rule, which causes it to block the request only if a test header is included or if a path is matched:

    - name: edge-auth-rule
        when:
          allOf:
            - { reqProperty: tier, equals: "publish" }
            - { reqHeader: x-edge-test, equals: "test" }
        action:
          type: authenticate
          authenticator: edge-auth

    - name: edge-auth-rule
        when:
          allOf:
            - { reqProperty: tier, equals: "publish" }
            - { reqProperty: path, like: "/test*" }
        action:
          type: authenticate
          authenticator: edge-auth

The following curl request pattern can be used:

curl https://publish-p<PROGRAM_ID>-e<ENV-ID>.adobeaemcloud.com -H "X-Forwarded-Host: example.com" -H "X-AEM-Edge-Key: <CONFIGURED_EDGE_KEY>" -H "x-edge-test: test"

After successfully testing, the additional condition can be removed and the configuration redeployed.

Purge API Token purge-API-token

Customers can purge the CDN cache by using a declared Purge API token. The token is declared in a file named cdn.yaml or similar, somewhere under a top-level config folder. Read Using Config Pipelines for details about the folder structure and how to deploy the configuration.

The syntax is described below:

kind: "CDN"
version: "1"
metadata:
  envTypes: ["dev"]
data:
  authentication:
    authenticators:
       - name: purge-auth
         type: purge
         purgeKey1: ${{CDN_PURGEKEY_031224}}
         purgeKey2: ${{CDN_PURGEKEY_021225}}
    rules:
       - name: purge-auth-rule
         when: { reqProperty: tier, equals: "publish" }
         action:
           type: authenticate
           authenticator: purge-auth

See Using Config Pipelines for a description of the properties above the data node. The kind property value should be CDN and the version property should be set to 1.

Additional properties include:

  • data node that contains a child authentication node.

  • Under authentication, one authenticators node and one rules node, both of which are arrays.

  • Authenticators: Lets you declare a type of token or credential, which in this case is an purge key. It includes the following properties:

    • name - a descriptive string.
    • type - must be purge.
    • purgeKey1 - its value must reference a Cloud Manager secret-type Environment Variable. For the Service Applied field, select All. It is recommended that the value (for example, ${{CDN_PURGEKEY_031224}}) reflects the day it was added.
    • purgeKey2 - used for rotation of secrets, which is described in the rotating secrets section section below. At least one of purgeKey1 and purgeKey2 must be declared.

  • Rules: Lets you declare which of the authenticators should be used, and whether it’s for the publish and/or preview tier. It includes:

    • name - a descriptive string
    • when - a condition that determines when the rule should be evaluated, according to the syntax in the Traffic Filter Rules article. Typically, it will include a comparison of the current tier (for example., publish).
    • action - must specify “authenticate”, with the intended authenticator referenced.
NOTE
The Purge Key must be configured as a secret type Cloud Manager Environment Variable, before the configuration referencing it is deployed. It is recommended to use a unique random key of minimum 32 bytes length; for example, the Open SSL cryptographic library can generate a random key by executing the command openssl rand -hex 32

You may reference a tutorial focused on configuring purge keys and performing the CDN cache purge.

Basic Authentication basic-auth

Protect certain content resources by popping up a basic auth dialog requiring a username and password. This feature is primarily intended for light authentication use cases such as business stakeholder review of content, rather than as a full-fledged solution for end-user access rights.

The end user will experience a basic auth dialog popping up like the following:

basicauth-dialog

The syntax is as follows:


kind: "CDN"
version: "1"
metadata:
  envTypes: ["dev"]
data:
  authentication:
    authenticators:
       - name: my-basic-authenticator
         type: basic
         credentials:
           - user: johndoe
             password: ${{JOHN_DOE_PASSWORD}}
           - user: janedoe
             password: ${{JANE_DOE_PASSWORD}}
    rules:
       - name: basic-auth-rule
         when: { reqProperty: path, like: "/summercampaign" }
         action:
           type: authenticate
           authenticator: my-basic-authenticator

See Using Config Pipelines for a description of the properties above the data node. The kind property value should be CDN and the version property should be set to 1.

In addition, the syntax includes:

  • a data node that contains an authentication node.

  • Under authentication, one authenticators node and one rules node, both of which are arrays.

  • Authenticators: in this scenario declare a basic authenticator, which has the following structure:

    • name - a descriptive string

    • type - must be basic

    • an array of up to 10 credentials, each of which includes the following name/value pairs, which end-users can enter in the basic auth dialog:

  • Rules: Lets you declare which of the authenticators should be used, and which resources should be protected. Each rule includes:

    • name - a descriptive string
    • when - a condition that determines when the rule should be evaluated, according to the syntax in the Traffic Filter Rules article. Typically, it will include a comparison of the publish tier or specific paths.
    • action - must specify “authenticate”, with the intended authenticator referenced, which is basic-auth for this scenario
NOTE
The passwords must be configured as secret type Cloud Manager environment variables, before the configuration referencing it is deployed.

Rotating secrets rotating-secrets

  1. It is good security practice to occasionally change credentials. This can be accomplished as exemplified below, using the example of an edge key, although the same strategy is used for purge keys.

  2. Initially just edgeKey1 has been defined, in this case referenced as ${{CDN_EDGEKEY_052824}}, which as a recommended convention, reflects the date it was created.

    code language-none 
    authentication:
  authenticators:
    - name: edge-auth
      type: edge
      edgeKey1: ${{CDN_EDGEKEY_052824}}

  3. When it’s time to rotate the key, create a new Cloud Manager secret, for example ${{CDN_EDGEKEY_041425}}.

  4. In the configuration, reference it from edgeKey2 and deploy.

    code language-none 
    authentication:
  authenticators:
    - name: edge-auth
      type: edge
      edgeKey1: ${{CDN_EDGEKEY_052824}}
      edgeKey2: ${{CDN_EDGEKEY_041425}}

  5. Once you are sure the old edge key is not used anymore, remove it by removing edgeKey1 from the configuration.

    code language-none 
    authentication:
  authenticators:
    - name: edge-auth
      type: edge
      edgeKey2: ${{CDN_EDGEKEY_041425}}

  6. Delete the old secret reference (${{CDN_EDGEKEY_052824}}) from Cloud Manager and deploy.

  7. When ready for the next rotation, follow the same procedure, however this time you will add edgeKey1 to the configuration, referencing a new Cloud Manager environment secret named, for example, ${{CDN_EDGEKEY_031426}}.

    code language-none 
    authentication:
  authenticators:
    - name: edge-auth
      type: edge
      edgeKey2: ${{CDN_EDGEKEY_041425}}
      edgeKey1: ${{CDN_EDGEKEY_031426}}
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