Internet-Draft CDNI Protected Secrets Metadata July 2023
Rosenblum Expires 9 January 2024 [Page]
Workgroup:
Network Working Group
Internet-Draft:
draft-rosenblum-cdni-protected-secrets-metadata-01
Published:
Intended Status:
Standards Track
Expires:
Author:
B. Rosenblum
Vecima

CDNI Protected Secrets Metadata

Abstract

This document defines a simple mechanism for protected secret data (such as salt values or encryption keys) that may be embedded in configuration metadata or capabilities advertisements.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

This Internet-Draft will expire on 9 January 2024.

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Table of Contents

1. Introduction

Certain objects in both the FCI and MI interfaces encapsulate sensitive values, such as credentials and access keys, which should not necessarily be accessible to all parties that can view the advertisement and configuration payloads.

This document defines two mechanisms to enclose secret values in the context of other FCI and MI objects that may only be viewed by the intended recipients, including embedded secrets encrypted using a certificate supplied by a counterparty and secrets stored in an external service (support defined in this draft is specifically for HashiCorp Vault), which are accessed via a specified path and a key ID. Refer to HashiCorp Vault documentation for details.

Either side can share secrets, and the functionality is the same for both sides, so the FCI capabilities are wrappers around the MI objects, similar to how FCI footprints (used in [RFC8008]) reutilize the MI.Footprint and registry defined in [RFC8006].

The public certificate for the downstream content delivery network (dCDN) is shared via FCI.SecretCertificate and the certificate for the upstream content delivery network (uCDN) is shared via MI.SecretCertificate.

Overview of the workflow for embedded secrets:

uCDN issues a GET to receive an advertisement with FCI.SecretStore and FCI.SecretCertificate. As the uCDN has not yet provided a certificate, any embedded secret values in the advertisement are omitted.

  1. uCDN issues a GET to receive an advertisement with FCI.SecretStore and FCI.SecretCertificate. As the uCDN has not yet provided a certificate, any embedded secret values in the advertisement are omitted.
  2. uCDN issues a PUT to publish a configuration with MI.SecretStore and MI.SecretValue with values encrypted using the dCDN certificate. The configuration also contains MI.SecretStore and MI.SecretCertificate.
  3. uCDN issues a GET to receive an updated capabilities advertisement; having provided an MI.SecretCertificate, the advertisement SHOULD now contain populated MI.SecretValue objects where necessary.

Detailed workflow examples, including modes that reference external services or contain secret values in plaintext, are available in the Workflow Examples section.

The MI.SecretValue objects are utilized in the FCI and MI interfaces, where secrets must be referenced, for example, the access-key-secret used for the MI.LoggingTransportS3API.

Certificates can be validated based on signatures in production environments, and self-signed certificates can be accepted in testing/lab environments. With this model, no out-of-band communication is required to share secrets.

2. Requirements

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].

3. Metadata Objects

3.1. MI.SecretStore

MI.SecretStore instructs the counterparty how to dereference the value of any MI.SecretValue objects linked to the store.

For embedded stores, MI.SecretStore identifies the certificate used for encrypting the values. For external stores (e.g., HashiCorp Vault), MI.SecretStore specifies the service endpoint that should be used in conjunction with the MI.SecretValue key path to obtain the secure data.

  • Property: secret-store-id

    • Description: A unique identifier for this store configuration that is referenced from linked MI.SecretValue objects.
    • Type: String
    • Mandatory-to-Specify: Yes

  • Property: secret-store-type

    • Description: A type discriminator for the configuration object, this property specifies whether the linked MI.SecretValue objects contain embedded secret objects or reference an external store.
    • Type: String. Either MI.SecretStoreTypeEmbedded or MI.SecretStoreTypeVault.
    • Mandatory-to-Specify: Yes

  • Property: secret-store-config

    • Description: The appropriate configuration object for the specified store type.
    • Type: Specified by the secret-store-type property.
    • Mandatory-to-Specify: Yes

  • Property: secret-certificate-id

    • Description: The ID of the MI.SecretStoreCertificate used to encrypt secret messages linked with this store configuration. Used only in the case of MI.SecretStoreTypeEmbedded.
    • Type: String
    • Mandatory-to-Specify: No

The following is an example of MI.SecretStore:

{
  "secret-store-id": "store-1",
  "secret-store-type": "MI.SecretStoreTypeEmbedded",
  "secret-store-config": {
       "format": "cms"
  }
}

3.2. MI.SecretStoreTypeEmbedded

MI.SecretStoreTypeEmbedded contains the configuration necessary to decrypt embedded secrets in MI.SecretValue.

The only currently supported encrypted message format is Cryptographic Message Syntax (CMS) as defined in [RFC5652]. Messages MUST be CMS type "EnvelopedData" and Base64 encoded.

A cleartext format is also defined for testing purposes. In this case, the value of an MI.SecretValue object's secret-value property is the cleartext secret.

  • Property: format

    • Description: The format of the embedded encrypted message.
    • Type: String. Either "cms" or "cleartext".
    • Mandatory-to-Specify: Yes

The following is an example of MI.SecretStoreTypeEmbedded specifying use of CMS:

{
  "secret-store-id": "store-1",
  "secret-store-type": "MI.SecretStoreTypeEmbedded",
  "secret-store-config": {
      "format": "cms"
  }
}

3.3. MI.SecretStoreTypeVault

MI.SecretStoreTypeVault contains the configuration necessary to reference secrets stored in an external instance of a HashiCorp Vault KV store.

MI.SecretValue objects reference secrets stored in the Vault using the secret-path property to identify the path and property key. See the MI.SecretValue section for details.

  • Property: endpoint

    • Description: The base URL of the Vault instance.
    • Type: String
    • Mandatory-to-Specify: Yes

  • Property: namespace

    • Description: The Vault namespace in which secret lookups should be performed.
    • Type: String
    • Mandatory-to-Specify: Yes

  • Property: version

    • Description: The Vault KV version.
    • Type: Integer. Valid values: 1 or 2.
    • Mandatory-to-Specify: Yes

The following is an example of MI.SecretStoreTypeVault specifying a version KV-V1 Vault:

{
  "secret-store-id": "store-2-vaultv1",
  "secret-store-type": "MI.SecretStoreTypeVault",
  "secret-store-config": {
      "endpoint": "https://vault.example.com/v1/secret",
      "version": 1,
      "namespace": "customer-1"
  }
}

The following is an example of MI.SecretStoreTypeVault specifying a version KV-V2 Vault:

{
  "secret-store-id": "store-3-vaultv2",
  "secret-store-type": "MI.SecretStoreTypeVault",
  "secret-store-config": {
      "endpoint": "https://vault.example.com/v1/secret",
      "version": 2,
      "namespace": "customer-1"
  }
}

3.4. MI.SecretValue

MI.SecretValue may be used in any FCI or MI object where sensitive data must be transmitted only to intended recipients.

  • Property: secret-store-id

    • Description: The linked MI.SecretStore that contains the configuration defining how to decrypt or access the referenced secret.
    • Type: String
    • Mandatory-to-Specify: Yes

  • Property: secret-value

    • Description: Used only for embedded secrets, the Base64 encoded value of a CMS message or the cleartext string, depending on the defined MI.SecretStore configuration.
    • Type: String
    • Mandatory-to-Specify: No

  • Property: secret-path

    • Description: Used only for HashiCorp Vault secrets, the path, not including namespace, to the secret, including the key of the particular property to access as the last path parameter.
    • Type: String
    • Mandatory-to-Specify: No

  • Property: timeout

    • Description: If this property is present and the elapsed time since last retrieving the secret value has exceeded the specified duration, any cached instance of this secret value should be discarded and fetched again from the associated secret store.
    • Type: Integer duration in seconds.
    • Mandatory-to-Specify: No

The following is an example of MI.SecretValue specifying an embedded value:

{
  "secret-store-id": "store-1-cms",
  "secret-value": "MIIBiQYJKoZIhvcNAQcDoIIBejCCAXYCAQAxggEhMIIBHQIBAD
AFMAACAQEwDQYJKoZIhvcNAQEBBQAEggEApJeXzsUS1jbAyNtQiJ9um9IMIHW5B2g+gHn
XdNSTyd33OEfTR6yLSZihBlFbHpY3qSzK1CX7RF5Oz3SqLDW+r3i1D/aHbVXwQbviWHEv
Hterql8l9VDm2FCNaDx5vihdbtvng3+/vdJNNMMhmovwZL5uhPsK81DkKwZCvznMMWt8Y
dNSFGT62f73ash7Eg/mS54IUyYOJHYrXEkRLSjvl0j+JqcIR8hCOCA78+5bS4MgfdsS9x
xSwQTrPru6EdTivMDKE/jlKg7li8lWdirWqtv0za5gLmH5T+zslXIoklwERAE50Jj8FxZ
D98EikKH8DAa+JeFsBm6Z1+yVFsWucTBMBgkqhkiG9w0BBwEwHQYJYIZIAWUDBAEqBBBw
s1riXA6m336zRbsiKtrVgCA267133v2zD/wjFQHXrKSJfd/2YJaxPskgdmQaVlgWCw=="
}

The following is an example of MI.SecretValue for a Vault:

{
  "secret-store-id": "store-2-vaultv1",
  "secret-path": "bar/baz/importantsecret",
  "timeout": 3600,
}

3.5. MI.SecretCertificate

MI.SecretCertificate is used to share an [X.509] certificate to be utilized for encrypting embedded secret messages.

In lab and testing environments, this certificate MAY be self-signed, depending on participant agreement.

In production environments, this SHOULD be a certificate signed by an appropriate certificate authority (CA)and validated by the counterparty.

  • Property: certificate-id

    • Description: A unique ID for this certificate that can be referenced from a corresponding MI.SecretStore configuration defined by a counterparty.
    • Type: String
    • Mandatory-to-Specify: Yes

  • Property: certificate-value

    • Description: The Base64 encoded certificate.
    • Type: String
    • Mandatory-to-Specify: Yes

The following is an example of MI.SecretCertificate:

{
  "certificate-id": "store-1",
  "certificate-value": "MIIDZTCCAk2gAwIBAgIUFJokJzAxDgUGsBd8uhSblpMwS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"
}

4. Capabilities Objects

These objects are simple capability wrappers around the MI objects defined in this specification.

4.1. FCI.SecretStore

FCI.SecretStore instructs the uCDN how to dereference the value of any MI.SecretValue objects linked to the store from other FCI objects via an embedded MI.SecretValue object. For further details, see the MI.SecretStore section.

The following is an example of FCI.SecretStore:

{
  "capabilities": [
    {
      "capability-type": "FCI.SecretStore",
      "capability-value": {
        "secret-store-id": "store-1",
        "secret-store-type": "MI.SecretStoreTypeEmbedded",
        "secret-store-config": {
           "format": "cms"
        }
      }
    }
  ]
}

4.2. FCI.SecretCertificate

FCI.SecretCertificate is used to share an [X.509] certificate to be utilized for encrypting embedded secret messages via an embedded MI.SecretCertificate object. For further details, see the MI.SecretCertificate section.

The following is an example of FCI.SecretCertificate:

{
  "capabilities": [
    {
      "capability-type": "FCI.SecretCertificate",
      "capability-value": {
        "certificate-id": "store-1",
        "certificate-value": "MIIDZTCCAk2gAwIBAgIUFJokJzAxDgUGsBd8uhS
blpMwSLAwDQYJKoZIhvcNAQELBQAwQjELMAkGA1UEBhMCVVMxEDAOBgNVBAgMB0dlb3Jn
aWExITAfBgNVBAoMGEludGVybmV0IFdpZGdpdHMgUHR5IEx0ZDAeFw0yMzAxMjMyMDM2M
DNaFw0yMzAyMjIyMDM2MDNaMEIxCzAJBgNVBAYTAlVTMRAwDgYDVQQIDAdHZW9yZ2lhMS
EwHwYDVQQKDBhJbnRlcm5ldCBXaWRnaXRzIFB0eSBMdGQwggEiMA0GCSqGSIb3DQEBAQU
AA4IBDwAwggEKAoIBAQCT11o9yebJmjiq7mXbLtnr5THpTnyahNpKECI+N8YZSl5+cS9h
Ga06zKQV3MNxbjJ15smmeWbgynYGwqhs5ZXGUjzd8S1/M1A08z1VFhEJiODQ00f3BOocp
In25RQzFz/BOLREW7sLkrhuz/WVBR3bzp6T1gu3nKcRSNuNxO1p9490gS1LhsZYQKfNvn
cuxBCP0GTNbUOXd6xkQ+EX5cEKoODUYWzOMdMAMlEEFb4jUjxYbbJoygwTMHpG2yGAQ2I
XpB2/wrrawivxDHlMHGpML+Ie8o6YBR4PDiOJmlCg9uIsirf65R1zhfcCxmNQ7z/IggC0
WNQjZwymeZT9cFDdAgMBAAGjUzBRMB0GA1UdDgQWBBQb5eJeYLEpErJetb1eid5BgsS3u
TAfBgNVHSMEGDAWgBQb5eJeYLEpErJetb1eid5BgsS3uTAPBgNVHRMBAf8EBTADAQH/MA
0GCSqGSIb3DQEBCwUAA4IBAQBURnrjVbHVwfV/u/xjzK8p4dTke0xb0oKt0J5YeH95sRa
66m3tQJYf0jbMNQ8InfXK0IzGM/uUOJX3daeOMQxMbJvaUDZV64kuU6IgkEQuLwkOP5k0
Rc9+SuRMlvWOB2exiyQkd2iHJtURuEtvB39LIr4pPDsicBAYxsm5ybIWCmqNMPkVl8Qks
3lAXeF+xvH11tmciTJSYP0Ud2psbV3lduD76UT2bzDGkr690KqroNS57WbQrHxEhtMbdq
0cPfzqFlxyhckqNYrcw2v1igQDhplQ2eUc4ye0Mvimj1Me2mWjPvilhvS3vDGhrmcx9ml
ishlI/RFy6yDI1gtkF7eS"
      }
    }
  ]
}

5. Workflow Examples

The facilities in this document can be used for simple and bidirectional exchange of secret values between uCDN and dCDN participants in an Open Caching system. The embedded model provides for a secret exchange without reference to out-of-band services, while the Vault support allows for external reference to secrets stored in a HashiCorp Vault.

Participants utilizing a secret distribution method or service not supported here MAY define a Private Feature MI object [SVTA2038] with the necessary configuration for that method or service and then utilize that MI object within MI.SecretStore and FCI.SecretStore.

Provided below are workflow examples for uCDN -> dCDN and dCDN -> uCDN exchanges of secret values.

Consideration is needed when addressing key rollover, expiration, and revocation in the embedded model. The RECOMMENDED workflow for key rollover is as follows:

When the recipient of a secret provides an updated configuration that no longer contains an MI.SecretCertificate with an ID referenced in MI.SecretStore used by MI.SecretValue objects, those MI.SecretValue objects SHOULD be reduced to an object with no contained secret-value property as they would be in the initial state before any certificate had been provided.

  1. When the recipient of a secret provides an updated configuration that no longer contains an MI.SecretCertificate with an ID referenced in MI.SecretStore used by MI.SecretValue objects, those MI.SecretValue objects SHOULD be reduced to an object with no contained secret-value property as they would be in the initial state before any certificate had been provided.
  2. If the recipient of a secret then provides a new MI.SecretCertificate object, the sender of the secret SHOULD update its MI.SecretStore to reference the new certificate-id and then update any referencing MI.SecretValue objects to include an updated secret-value property that contains the newly encrypted values.

5.1. Workflow: uCDN -> dCDN Embedded

The uCDN advertises FCI.SecretStore with a store-type of MI.SecretStoreTypeEmbedded; other FCI objects may contain MI.SecretValue objects that reference the store-id. MI.SecretValue objects that do not presently contain a secret-value property.

  1. The uCDN advertises FCI.SecretStore with a store-type of MI.SecretStoreTypeEmbedded; other FCI objects may contain MI.SecretValue objects that reference the store-id. MI.SecretValue objects that do not presently contain a secret-value property.
  2. The dCDN pushes the MI configuration with an MI.SecretCertificate.
  3. The uCDN updates the advertised FCI.SecretStore with a certificate-id property that references the dCDN MI.SecretCertificate; any MI.SecretValue objects in other FCI objects now contain a secret-value property with the CMS encrypted secret.

5.2. Workflow: dCDN -> uCDN Embedded

The uCDN advertises an FCI.SecretCertificate.

  1. The uCDN advertises an FCI.SecretCertificate.
  2. The dCDN pushes the MI configuration containing MI.SecretStore with a store-type of MI.SecretStoreTypeEmbedded and a certificate-id referencing the FCI.SecretCertificate advertised by the uCDN. Other MI objects may contain MI.SecretValue objects with a secret-value property containing the CMS encrypted secret.

5.3. Workflow: Embedded Cleartext (uCDN and dCDN)

An MI.SecretStoreTypeEmbedded has a defined format of "cleartext".

  1. An MI.SecretStoreTypeEmbedded has a defined format of "cleartext".
  2. Any MI.SecretValue objects that reference the cleartext store contain a secret-value property with the unencrypted secret.

5.4. Workflow: uCDN -> dCDN Vault

The uCDN advertises an FCI.SecretStore with an appropriate configuration for accessing an instance of a HashiCorp Vault accessible to the dCDN. Other FCI objects may contain MI.SecretValue objects that reference the FCI.SecretStore and a secret-path property specifying the secret to retrieve.

5.5. Workflow: dCDN -> uCDN Vault

The dCDN pushes the MI configuration, including an MI.SecretStore with appropriate configuration for accessing an instance of a HashiCorp Vault accessible to the uCDN. Other MI objects may contain MI.SecretValue objects that reference the MI.SecretStore and a secret-path property specifying the secret to retrieve.

6. Security Considerations

The FCI and MI objects defined in the present document are transferred via the interfaces defined in CDNI [RFC8006]. [RFC8006] describes how to secure these interfaces, protecting the integrity, confidentiality and ensuring the authenticity of the dCDN and uCDN. The security provide by [RFC8006] should therefore address the above security concerns.

7. IANA Considerations

8. Acknowledgements

The authors would like to express their gratitude to the members of the Streaming Video Technology Alliance [SVTA] Open Caching Working Group for their guidance / contribution / reviews ...)

9. References

9.1. Normative References

[RFC8008]
Seedorf, J., Peterson, J., Previdi, S., van Brandenburg, R., and K. Ma, "Content Delivery Network Interconnection (CDNI) Request Routing: Footprint and Capabilities Semantics", RFC 8008, DOI 10.17487/RFC8008, , <https://www.rfc-editor.org/info/rfc8008>.
[RFC8006]
Niven-Jenkins, B., Murray, R., Caulfield, M., and K. Ma, "Content Delivery Network Interconnection (CDNI) Metadata", RFC 8006, DOI 10.17487/RFC8006, , <https://www.rfc-editor.org/info/rfc8006>.
[RFC5652]
Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, RFC 5652, DOI 10.17487/RFC5652, , <https://www.rfc-editor.org/info/rfc5652>.
[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/info/rfc2119>.
[X.509]
{ITU}, "X.509", , <http://www.itu.int/rec/T-REC-X.509>.

9.2. Informative References

[SVTA]
"Streaming Video Technology Alliance Home Page", <https://www.svta.org>.
[SVTA2038]
"Configuration Interface Part 2h: Private Features", <https://svta.org/documents/SVTA2038>.

Author's Address

Ben Rosenblum
Vecima
4375 River Green Pkwy #100
Duluth , GA 30096
United States of America