rfc9677v1.txt   rfc9677.txt 
Internet Engineering Task Force (IETF) F. Fieau Internet Engineering Task Force (IETF) F. Fieau
Request for Comments: 9677 E. Stephan Request for Comments: 9677 E. Stephan
Category: Standards Track Orange Category: Standards Track Orange
ISSN: 2070-1721 G. Guillaume ISSN: 2070-1721 G. Bichot
C. Christoph C. Neumann
Broadpeak Broadpeak
October 2024 October 2024
Content Delivery Network Interconnection (CDNI) Metadata for Delegated Content Delivery Network Interconnection (CDNI) Metadata for Delegated
Credentials Credentials
Abstract Abstract
The delivery of content over HTTPS involving multiple Content The delivery of content over HTTPS involving multiple Content
Delivery Networks (CDNs) raises credential management issues. This Delivery Networks (CDNs) raises credential management issues. This
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delegated credential and deploy it on multiple endpoints. delegated credential and deploy it on multiple endpoints.
Alternatively, the dCDN MAY deploy a different delegated credential Alternatively, the dCDN MAY deploy a different delegated credential
for each endpoint (provided that the uCDN delivers enough different for each endpoint (provided that the uCDN delivers enough different
delegated credentials). This choice is at the discretion of the dCDN delegated credentials). This choice is at the discretion of the dCDN
and depends on the number of delegated credentials provided by the and depends on the number of delegated credentials provided by the
uCDN. uCDN.
The FCI.DelegationCredentials object does not address expiry or The FCI.DelegationCredentials object does not address expiry or
renewal of delegated credentials. Once the uCDN has provided renewal of delegated credentials. Once the uCDN has provided
delegated credentials via the MI, the uCDN SHOULD monitor the delegated credentials via the MI, the uCDN SHOULD monitor the
provided credentials and their expiry times and timely refresh dCDN provided credentials and their expiry times and SHOULD refresh dCDN
credentials via the MI. The uCDN may decide not to monitor the credentials via the MI in a timely manner. The uCDN may decide not
validity period of delegated credentials and not to refresh the to monitor the validity period of delegated credentials and not to
credentials, for example, in cases of short-term one-shot deployments refresh the credentials, for example, in cases of short-term one-shot
or once it has decided to deprovision a dCDN. If the delegated deployments or once it has decided to deprovision a dCDN. If the
credential is not renewed on time by the uCDN, the servers of the delegated credential is not renewed on time by the uCDN, the servers
dCDN that only have expired delegated credentials MUST refuse any new of the dCDN that only have expired delegated credentials MUST refuse
TLS connection that requires an up-to-date delegated credential. any new TLS connection that requires an up-to-date delegated
credential.
4. CDNI Metadata Interface (MI) Metadata Object for Delegated 4. CDNI Metadata Interface (MI) Metadata Object for Delegated
Credentials Credentials
As expressed in [RFC9345], when an uCDN has delegated to a dCDN, the As expressed in [RFC9345], when an uCDN has delegated to a dCDN, the
dCDN presents the "delegated_credential" (rather than its own dCDN presents the "delegated_credential" (rather than its own
certificate) during the TLS handshake [RFC8446] to the User Agent. certificate) during the TLS handshake [RFC8446] to the User Agent.
This implies that the dCDN is also in the possession of the private This implies that the dCDN is also in the possession of the private
key corresponding to the public key in DelegatedCredential.cred key corresponding to the public key in DelegatedCredential.cred
[RFC9345]. This allows the User Agent to verify the signature in a [RFC9345]. This allows the User Agent to verify the signature in a
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constraints regarding the usage of the private key. constraints regarding the usage of the private key.
If the private-key property is used, the transported private key MUST If the private-key property is used, the transported private key MUST
be encrypted using the PrivateKeyEncryptionKey specified in be encrypted using the PrivateKeyEncryptionKey specified in
FCI.DelegatedCredentials. The envelope format for this property MUST FCI.DelegatedCredentials. The envelope format for this property MUST
use JWE [RFC7516] using the base64 compact serialization (Section 7.1 use JWE [RFC7516] using the base64 compact serialization (Section 7.1
of [RFC7516]), whereas the private key is included as JWE Ciphertext of [RFC7516]), whereas the private key is included as JWE Ciphertext
in the JWE. The JWE content-type field MAY be used to signal the in the JWE. The JWE content-type field MAY be used to signal the
media type of the encrypted key. media type of the encrypted key.
Below, please see an example of an MI.DelegatedCredential object. Below, please see an example of an MI.DelegatedCredentials object.
{ {
"generic-metadata-type": "MI.DelegatedCredentials", "generic-metadata-type": "MI.DelegatedCredentials",
"generic-metadata-value": { "generic-metadata-value": {
"delegated-credentials": [ "delegated-credentials": [
{"delegated-credential": {"delegated-credential":
"cBBfm8KK6pPz/tdgKyedwA... "cBBfm8KK6pPz/tdgKyedwA...
iXCCIAmzMM0R8FLI3Ba0UQ=="}, iXCCIAmzMM0R8FLI3Ba0UQ=="},
{"delegated-credential": {"delegated-credential":
"4pyIGtjFdys1+9y/4sS/Fg... "4pyIGtjFdys1+9y/4sS/Fg...
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} }
} }
5. Delegated Credentials Call Flow 5. Delegated Credentials Call Flow
An example call-flow using delegated credentials is depicted in An example call-flow using delegated credentials is depicted in
Figure 1. The steps are as follows. Figure 1. The steps are as follows.
1. It is assumed that the uCDN has been provisioned and configured 1. It is assumed that the uCDN has been provisioned and configured
with a certificate. Note that it is out of scope of CDNI and the with a certificate. Note that it is out of scope of CDNI and the
present document how and from where (e.g., Content Service present document how and from where (e.g., which Content Service
Provider) the uCDN acquired its certificate. Provider) the uCDN acquired its certificate.
2. The uCDN generates a set of delegated credentials (here it is 2. The uCDN generates a set of delegated credentials (here it is
assumed that public keys of the dCDN are known). Note that the assumed that public keys of the dCDN are known). Note that the
uCDN may generate this material at different points in time, uCDN may generate this material at different points in time,
e.g., in advance to have a pool of delegated credentials or on e.g., in advance to have a pool of delegated credentials or on
demand when the dCDN announces its maximum number of supported demand when the dCDN announces its maximum number of supported
delegated credentials. delegated credentials.
3. Using the CDNI FCI [RFC8008], the dCDN advertises 3. Using the CDNI FCI [RFC8008], the dCDN advertises
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| | [2. generation of | | [2. generation of
| | delegated credentials] | | delegated credentials]
| | | | | |
| 3. CDNI FCI used to | 3. CDNI FCI used to
| advertise support of MI.DelegatedCredentials | advertise support of MI.DelegatedCredentials
| and announce number of delegated credentials | and announce number of delegated credentials
| supported using FCI.DelegatedCredentials | supported using FCI.DelegatedCredentials
| |-------------------->+ | |-------------------->+
| | | | | |
| 4. CDNI MI used to | 4. CDNI MI used to
| provide the MI.DelegatedCredential object | provide the MI.DelegatedCredentials object
| |<--------------------+ | |<--------------------+
| | | | | |
. .
. .
. .
[5. TLS handshake according | [5. TLS handshake according |
to [RFC9345]] . | to [RFC9345]] . |
|<------------------->| | |<------------------->| |
| | | | | |
. .
. .
. .
| 6. Some delegated credentials about to expire. | 6. Some delegated credentials about to expire.
| CDNI MI used to | CDNI MI used to
| provide new MI.DelegatedCredential object | provide new MI.DelegatedCredentials object
| |<--------------------+ | |<--------------------+
| | | | | |
Figure 1: Example Call Flow of Delegated Credentials in CDNI Figure 1: Example Call Flow of Delegated Credentials in CDNI
6. IANA Considerations 6. IANA Considerations
IANA has registered the following payload types in the "CDNI Payload IANA has registered the following payload types in the "CDNI Payload
Types" registry in the "Content Delivery Network Interconnection Types" registry in the "Content Delivery Network Interconnection
(CDNI) Parameters" registry group. (CDNI) Parameters" registry group.
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requires access to the private key in order to exploit a delegated requires access to the private key in order to exploit a delegated
credential and impersonate dCDN nodes. Thus, leakage of only the credential and impersonate dCDN nodes. Thus, leakage of only the
delegated credential without the private key represents a limited delegated credential without the private key represents a limited
security risk. security risk.
Delegated credentials and associated private keys are short-lived Delegated credentials and associated private keys are short-lived
(per default, the maximum validity period is set to 7 days in (per default, the maximum validity period is set to 7 days in
[RFC9345]) and as such a single leaked delegated credential with its [RFC9345]) and as such a single leaked delegated credential with its
private key represents a limited security risk. Still, it is NOT private key represents a limited security risk. Still, it is NOT
RECOMMENDED to send private keys through the MI. Omitting the RECOMMENDED to send private keys through the MI. Omitting the
private key further limits the possibility exploits by an attacker to private key further limits the possible ways an attacker could
exploit the delegated credential. exploits the delegated credential.
If this recommendation is not followed, i.e., the private key is If this recommendation is not followed, i.e., the private key is
communicated via the MI, the transported private key MUST be communicated via the MI, the transported private key MUST be
encrypted within a JWE envelope using the encryption key encrypted within a JWE envelope using the encryption key
(PrivateKeyEncryptionKey) provided within the (PrivateKeyEncryptionKey) provided within the
FCI.DelegatedCredentials by the dCDN. The JWE encryption key FCI.DelegatedCredentials by the dCDN. The JWE encryption key
(PrivateKeyEncryptionKey) MUST have a strength equal to or larger (PrivateKeyEncryptionKey) MUST have a strength equal to or larger
than the private key it is encrypting for transport. Note that the than the private key it is encrypting for transport. Note that the
specified encryption method does not offer forward secrecy. If the specified encryption method does not offer forward secrecy. If the
dCDN's encryption key becomes compromised in the future, then all dCDN's encryption key becomes compromised in the future, then all
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secure these interfaces, protecting the integrity and secure these interfaces, protecting the integrity and
confidentiality, as well as ensuring the authenticity of the dCDN and confidentiality, as well as ensuring the authenticity of the dCDN and
uCDN, which should prevent an attacker from systematically retrieving uCDN, which should prevent an attacker from systematically retrieving
delegated credentials and associated private keys. delegated credentials and associated private keys.
8. Privacy Considerations 8. Privacy Considerations
The FCI and MI objects and the information defined in the present The FCI and MI objects and the information defined in the present
document do not contain any personally identifiable information document do not contain any personally identifiable information
(PII). As such, this document does not change or alter the (PII). As such, this document does not change or alter the
Confidentiality and Privacy Consideration outlined in the CDNI confidentiality and privacy considerations outlined in Section 8.2 of
Metadata and Footprint and Capabilities RFCs [RFC8006]. [RFC8006] and Section 7 of [RFC8008].
A single or systematic retrieval of delegated credentials and A single or systematic retrieval of delegated credentials and
associated private keys would allow the attacker to decrypt any data associated private keys would allow the attacker to decrypt any data
sent by the end user intended for the end service, which may include sent by the end user intended for the end service, which may include
PII. PII.
9. References 9. References
9.1. Normative References 9.1. Normative References
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Emile Stephan Emile Stephan
Orange Orange
2, avenue Pierre Marzin 2, avenue Pierre Marzin
22300 Lannion 22300 Lannion
France France
Email: emile.stephan@orange.com Email: emile.stephan@orange.com
Guillaume Bichot Guillaume Bichot
Broadpeak Broadpeak
15, rue Claude Chappe 3771 Boulevard des Alliés
35510 Cesson-Sevigne 35510 Cesson-Sévigné
France France
Email: guillaume.bichot@broadpeak.tv Email: guillaume.bichot@broadpeak.tv
Christoph Neumann Christoph Neumann
Broadpeak Broadpeak
15, rue Claude Chappe 3771 Boulevard des Alliés
35510 Cesson-Sevigne 35510 Cesson-Sévigné
France France
Email: christoph.neumann@broadpeak.tv Email: christoph.neumann@broadpeak.tv
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