Internet-Draft CDNI rotected Secrets Metadata March 2023
Rosenblum Expires 11 September 2023 [Page]
Workgroup:
Network Working Group
Internet-Draft:
draft-rosenblum-cdni-protected-secrets-metadata-00
Updates:
8006, 8008 (if approved)
Published:
Intended Status:
Standards Track
Expires:
Author:
B. Rosenblum
Vecima

CDNI Protected Secrets Metadata

Abstract

This is an early draft for a proposed mechanism to protect secret values (such as keys or token salt values) that are part of the Configuration Metadata.

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 11 September 2023.

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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 which can view the advertisement and configuration payloads.

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

Either side can share secrets, and the functionality is the same, 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 dCDN is shared via FCI.SecretCertificate and the certificate for the uCDN is shared via MI.SecretCertificate.

The workflow for embedded secrets on both sides:

  1. uCDN GET advertisement with FCI.SecretStore and FCI.SecretCertificate
  2. As the uCDN has not yet provided a certificate, any embedded secret values in the advertisement are omitted.
  3. uCDN PUT configuration with MI.SecretStore and MI.SecretValue with values encrypted using dCDN certificate. Configuration also contains MI.SecretStore and MI.SecretCertificate.
  4. uCDN GET advertisement again; having provided an MI.SecretCertificate, the advertisement now contains populated MI.SecretValue objects where necessary.

Detailed workflow examples, including modes which reference external services or contain secret values in plaintext, are available in Section 4 .

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 signature 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. Metadata Objects

2.1. MI.SecretStore

MI.SecretStore instructs the counterparty on 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 (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 config object, this property specifies whether the linked MI.SecretValue objects contain embedded secret objects or reference an external store.
    • Type: String. One of 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 shows an example usage of MI.SecretStore

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

2.2. 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 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 a MI.SecretValue object's secret-value property is the cleartext secret.

  • Property: format

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

The following shows an example usage of MI.SecretStoreTypEmbedded with a "cms" format.

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

2.3. MI.SecretStoreTypeVault

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

MI.SecretValue objects referencing secrets stored in Vault use the secret-path property to identify the path and property key. See the MI.SecretValue documentation 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 shows an example usage of MI.SecretStoreTypVault for Vault V1.

{
  "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 shows an example usage of MI.SecretStoreTypVault for Vault V2.

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

2.4. 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 which 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.

The following shows an example usage of MI.SecretValue with an embdedded CMS secret.

{
  "secret-store-id": "store-1-cms",
  "secret-value": "MIIBiQYJKoZIhvcNAQcDoIIBejCCAXYCAQAxggEhMIIBHQIBADAFM
AACAQEwDQYJKoZIhvcNAQEBBQAEggEApJeXzsUS1jbAyNtQiJ9um9IMIHW5B2g+gHnXdNSTy
d33OEfTR6yLSZihBlFbHpY3qSzK1CX7RF5Oz3SqLDW+r3i1D/aHbVXwQbviWHEvHterql8l9
VDm2FCNaDx5vihdbtvng3+/vdJNNMMhmovwZL5uhPsK81DkKwZCvznMMWt8YdNSFGT62f73a
sh7Eg/mS54IUyYOJHYrXEkRLSjvl0j+JqcIR8hCOCA78+5bS4MgfdsS9xxSwQTrPru6EdTiv
MDKE/jlKg7li8lWdirWqtv0za5gLmH5T+zslXIoklwERAE50Jj8FxZD98EikKH8DAa+JeFsB
m6Z1+yVFsWucTBMBgkqhkiG9w0BBwEwHQYJYIZIAWUDBAEqBBBws1riXA6m336zRbsiKtrVg
CA267133v2zD/wjFQHXrKSJfd/2YJaxPskgdmQaVlgWCw=="
}

The following shows an example usage of MI.SecretValue with a reference to a secert stored in Vault.

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

2.5. MI.SecretCertificate

MI.SecretCertificate is used to share an [X.509] certificate to be used 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 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 the counterparty.
    • Type: String.
    • Mandatory-to-Specify: Yes.

  • Property: certificate-value

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

The following shows an example usage of MI.SecretCertificate.

{
  "certificate-id": "store-1",
  "certificate-value": "MIIDZTCCAk2gAwIBAgIUFJokJzAxDgUGsBd8uhSblpMwSLAw
DQYJKoZIhvcNAQELBQAwQjELMAkGA1UEBhMCVVMxEDAOBgNVBAgMB0dlb3JnaWExITAfBgNV
BAoMGEludGVybmV0IFdpZGdpdHMgUHR5IEx0ZDAeFw0yMzAxMjMyMDM2MDNaFw0yMzAyMjIy
MDM2MDNaMEIxCzAJBgNVBAYTAlVTMRAwDgYDVQQIDAdHZW9yZ2lhMSEwHwYDVQQKDBhJbnRl
cm5ldCBXaWRnaXRzIFB0eSBMdGQwggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQCT
11o9yebJmjiq7mXbLtnr5THpTnyahNpKECI+N8YZSl5+cS9hGa06zKQV3MNxbjJ15smmeWbg
ynYGwqhs5ZXGUjzd8S1/M1A08z1VFhEJiODQ00f3BOocpIn25RQzFz/BOLREW7sLkrhuz/WV
BR3bzp6T1gu3nKcRSNuNxO1p9490gS1LhsZYQKfNvncuxBCP0GTNbUOXd6xkQ+EX5cEKoODU
YWzOMdMAMlEEFb4jUjxYbbJoygwTMHpG2yGAQ2IXpB2/wrrawivxDHlMHGpML+Ie8o6YBR4P
DiOJmlCg9uIsirf65R1zhfcCxmNQ7z/IggC0WNQjZwymeZT9cFDdAgMBAAGjUzBRMB0GA1Ud
DgQWBBQb5eJeYLEpErJetb1eid5BgsS3uTAfBgNVHSMEGDAWgBQb5eJeYLEpErJetb1eid5B
gsS3uTAPBgNVHRMBAf8EBTADAQH/MA0GCSqGSIb3DQEBCwUAA4IBAQBURnrjVbHVwfV/u/xj
zK8p4dTke0xb0oKt0J5YeH95sRa66m3tQJYf0jbMNQ8InfXK0IzGM/uUOJX3daeOMQxMbJva
UDZV64kuU6IgkEQuLwkOP5k0Rc9+SuRMlvWOB2exiyQkd2iHJtURuEtvB39LIr4pPDsicBAY
xsm5ybIWCmqNMPkVl8Qks3lAXeF+xvH11tmciTJSYP0Ud2psbV3lduD76UT2bzDGkr690Kqr
oNS57WbQrHxEhtMbdq0cPfzqFlxyhckqNYrcw2v1igQDhplQ2eUc4ye0Mvimj1Me2mWjPvil
hvS3vDGhrmcx9mlishlI/RFy6yDI1gtkF7eS"
}

3. Capabilities Objects

These objects are simple capability wrappers around the Section 2 defined MI objects.

3.1. FCI.SecretStore

FCI.SecretStore instructs the uCDN on 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 Section 2.1 MI.SecretStore.

The following shows an example usage 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"
        }
      }
    }
  ]
}

3.2. FCI.SecretCertificate

FCI.SecretCertificate is used to share an [X.509] certificate to be used for encrypting embedded secret messages via an embedded MI.SecretCertificate object. For further details, see Section 2.5 MI.SecretCertificate.

{
  "capabilities": [
    {
      "capability-type": "FCI.SecretCertificate",
      "capability-value": {
        "certificate-id": "store-1",
        "certificate-value": "MIIDZTCCAk2gAwIBAgIUFJokJzAxDgUGsBd8uhSblp
MwSLAwDQYJKoZIhvcNAQELBQAwQjELMAkGA1UEBhMCVVMxEDAOBgNVBAgMB0dlb3JnaWExIT
AfBgNVBAoMGEludGVybmV0IFdpZGdpdHMgUHR5IEx0ZDAeFw0yMzAxMjMyMDM2MDNaFw0yMz
AyMjIyMDM2MDNaMEIxCzAJBgNVBAYTAlVTMRAwDgYDVQQIDAdHZW9yZ2lhMSEwHwYDVQQKDB
hJbnRlcm5ldCBXaWRnaXRzIFB0eSBMdGQwggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAo
IBAQCT11o9yebJmjiq7mXbLtnr5THpTnyahNpKECI+N8YZSl5+cS9hGa06zKQV3MNxbjJ15s
mmeWbgynYGwqhs5ZXGUjzd8S1/M1A08z1VFhEJiODQ00f3BOocpIn25RQzFz/BOLREW7sLkr
huz/WVBR3bzp6T1gu3nKcRSNuNxO1p9490gS1LhsZYQKfNvncuxBCP0GTNbUOXd6xkQ+EX5c
EKoODUYWzOMdMAMlEEFb4jUjxYbbJoygwTMHpG2yGAQ2IXpB2/wrrawivxDHlMHGpML+Ie8o
6YBR4PDiOJmlCg9uIsirf65R1zhfcCxmNQ7z/IggC0WNQjZwymeZT9cFDdAgMBAAGjUzBRMB
0GA1UdDgQWBBQb5eJeYLEpErJetb1eid5BgsS3uTAfBgNVHSMEGDAWgBQb5eJeYLEpErJetb
1eid5BgsS3uTAPBgNVHRMBAf8EBTADAQH/MA0GCSqGSIb3DQEBCwUAA4IBAQBURnrjVbHVwf
V/u/xjzK8p4dTke0xb0oKt0J5YeH95sRa66m3tQJYf0jbMNQ8InfXK0IzGM/uUOJX3daeOMQ
xMbJvaUDZV64kuU6IgkEQuLwkOP5k0Rc9+SuRMlvWOB2exiyQkd2iHJtURuEtvB39LIr4pPD
sicBAYxsm5ybIWCmqNMPkVl8Qks3lAXeF+xvH11tmciTJSYP0Ud2psbV3lduD76UT2bzDGkr
690KqroNS57WbQrHxEhtMbdq0cPfzqFlxyhckqNYrcw2v1igQDhplQ2eUc4ye0Mvimj1Me2m
WjPvilhvS3vDGhrmcx9mlishlI/RFy6yDI1gtkF7eS"
      }
    }
  ]
}

4. 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 secret exchange without reference to out-of-band services, and the Vault support allows external reference to secrets stored in HashiCorp Vault.

Participants utilizing a secrets distribution method or service not supported here may define a Private Feature MI object 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 exchange 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 secrets recipient 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 secrets recipient 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 secrets recipient then provides a new MI.SecretCertificate object, the secrets sender should update their 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.

4.1. Workflow: uCDN -> dCDN Embedded

  1. 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 do not presently contain a secret-value property.
  2. dCDN pushes MI configuration with an MI.SecretCertificate.
  3. 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.

4.2. Workflow: dCDN -> uCDN Embedded

  1. uCDN advertises an FCI.SecretCertificate.
  2. dCDN pushes 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.

4.3. Workflow: Embedded Cleartext (uCDN and dCDN)

  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.

4.4. Workflow: uCDN -> dCDN Vault

  1. uCDN advertises an FCI.SecretStore with appropriate configuration for accessing an instance of 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 which secret to retrieve.

4.5. Workflow: dCDN -> uCDN Vault

  1. dCDN pushes MI configuration including an MI.SecretStore with appropriate configuration for accessing an instance of 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 which secret to retrieve.

5. 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.

6. IANA Considerations

7. Acknowledgements

The authors would like to express their gratitude to the following members of the Streaming Video Technology Alliance [SVTA] Open Caching Working Group for their guidance, contribution, and review,

8. References

8.1. Normative References

[RFC5652]
Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, RFC 5652, DOI 10.17487/RFC5652, , <https://www.rfc-editor.org/info/rfc5652>.
[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>.
[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>.
[X.509]
{ITU}, "X.509", , <http://www.itu.int/rec/T-REC-X.509>.

8.2. Informative References

[SVTA]
"Streaming Video Technology Alliance Home Page", <https://www.svta.org>.

Author's Address

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