draft-ietf-ace-oscore-profile-12.txt   draft-ietf-ace-oscore-profile-13.txt 
ACE Working Group F. Palombini ACE Working Group F. Palombini
Internet-Draft Ericsson AB Internet-Draft Ericsson AB
Intended status: Standards Track L. Seitz Intended status: Standards Track L. Seitz
Expires: March 25, 2021 Combitech Expires: April 30, 2021 Combitech
G. Selander G. Selander
Ericsson AB Ericsson AB
M. Gunnarsson M. Gunnarsson
RISE RISE
September 21, 2020 October 27, 2020
OSCORE Profile of the Authentication and Authorization for Constrained OSCORE Profile of the Authentication and Authorization for Constrained
Environments Framework Environments Framework
draft-ietf-ace-oscore-profile-12 draft-ietf-ace-oscore-profile-13
Abstract Abstract
This memo specifies a profile for the Authentication and This memo specifies a profile for the Authentication and
Authorization for Constrained Environments (ACE) framework. It Authorization for Constrained Environments (ACE) framework. It
utilizes Object Security for Constrained RESTful Environments utilizes Object Security for Constrained RESTful Environments
(OSCORE) to provide communication security and proof-of-possession (OSCORE) to provide communication security and proof-of-possession
for a key owned by the client and bound to an OAuth 2.0 access token. for a key owned by the client and bound to an OAuth 2.0 access token.
Status of This Memo Status of This Memo
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This Internet-Draft will expire on March 25, 2021. This Internet-Draft will expire on April 30, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 4 2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 4
3. Client-AS Communication . . . . . . . . . . . . . . . . . . . 6 3. Client-AS Communication . . . . . . . . . . . . . . . . . . . 6
3.1. C-to-AS: POST to token endpoint . . . . . . . . . . . . . 6 3.1. C-to-AS: POST to token endpoint . . . . . . . . . . . . . 6
3.2. AS-to-C: Access Token . . . . . . . . . . . . . . . . . . 8 3.2. AS-to-C: Access Token . . . . . . . . . . . . . . . . . . 8
3.2.1. The OSCORE_Input_Material . . . . . . . . . . . . . . 13 3.2.1. The OSCORE_Input_Material . . . . . . . . . . . . . . 12
4. Client-RS Communication . . . . . . . . . . . . . . . . . . . 16 4. Client-RS Communication . . . . . . . . . . . . . . . . . . . 15
4.1. C-to-RS: POST to authz-info endpoint . . . . . . . . . . 17 4.1. C-to-RS: POST to authz-info endpoint . . . . . . . . . . 16
4.1.1. The Nonce 1 Parameter . . . . . . . . . . . . . . . . 18 4.1.1. The Nonce 1 Parameter . . . . . . . . . . . . . . . . 17
4.2. RS-to-C: 2.01 (Created) . . . . . . . . . . . . . . . . . 18 4.1.2. The ace_client_recipientid Parameter . . . . . . . . 17
4.2.1. The Nonce 2 Parameter . . . . . . . . . . . . . . . . 20 4.2. RS-to-C: 2.01 (Created) . . . . . . . . . . . . . . . . . 17
4.3. OSCORE Setup . . . . . . . . . . . . . . . . . . . . . . 20 4.2.1. The Nonce 2 Parameter . . . . . . . . . . . . . . . . 19
4.2.2. The ace_server_recipientid Parameter . . . . . . . . 19
4.3. OSCORE Setup . . . . . . . . . . . . . . . . . . . . . . 19
4.4. Access rights verification . . . . . . . . . . . . . . . 22 4.4. Access rights verification . . . . . . . . . . . . . . . 22
5. Secure Communication with AS . . . . . . . . . . . . . . . . 22 5. Secure Communication with AS . . . . . . . . . . . . . . . . 22
6. Discarding the Security Context . . . . . . . . . . . . . . . 23 6. Discarding the Security Context . . . . . . . . . . . . . . . 22
7. Security Considerations . . . . . . . . . . . . . . . . . . . 24 7. Security Considerations . . . . . . . . . . . . . . . . . . . 23
8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 25 8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 25
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
9.1. ACE Profile Registry . . . . . . . . . . . . . . . . . . 26 9.1. ACE Profile Registry . . . . . . . . . . . . . . . . . . 25
9.2. OAuth Parameters Registry . . . . . . . . . . . . . . . . 26 9.2. OAuth Parameters Registry . . . . . . . . . . . . . . . . 26
9.3. OAuth Parameters CBOR Mappings Registry . . . . . . . . . 26 9.3. OAuth Parameters CBOR Mappings Registry . . . . . . . . . 26
9.4. OSCORE Security Context Parameters Registry . . . . . . . 27 9.4. OSCORE Security Context Parameters Registry . . . . . . . 27
9.5. CWT Confirmation Methods Registry . . . . . . . . . . . . 28 9.5. CWT Confirmation Methods Registry . . . . . . . . . . . . 28
9.6. JWT Confirmation Methods Registry . . . . . . . . . . . . 28 9.6. JWT Confirmation Methods Registry . . . . . . . . . . . . 28
9.7. Expert Review Instructions . . . . . . . . . . . . . . . 28 9.7. Expert Review Instructions . . . . . . . . . . . . . . . 28
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 29 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 29
10.1. Normative References . . . . . . . . . . . . . . . . . . 29 10.1. Normative References . . . . . . . . . . . . . . . . . . 29
10.2. Informative References . . . . . . . . . . . . . . . . . 30 10.2. Informative References . . . . . . . . . . . . . . . . . 30
Appendix A. Profile Requirements . . . . . . . . . . . . . . . . 31 Appendix A. Profile Requirements . . . . . . . . . . . . . . . . 31
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This profile requires a client to retrieve an access token from the This profile requires a client to retrieve an access token from the
AS for the resource it wants to access on an RS, by sending an access AS for the resource it wants to access on an RS, by sending an access
token request to the token endpoint, as specified in section 5.6 of token request to the token endpoint, as specified in section 5.6 of
[I-D.ietf-ace-oauth-authz]. The access token request and response [I-D.ietf-ace-oauth-authz]. The access token request and response
MUST be confidentiality-protected and ensure authenticity. This MUST be confidentiality-protected and ensure authenticity. This
profile RECOMMENDS the use of OSCORE between client and AS, but other profile RECOMMENDS the use of OSCORE between client and AS, but other
protocols (such as TLS or DTLS) can be used as well. protocols (such as TLS or DTLS) can be used as well.
Once the client has retrieved the access token, it generates a nonce Once the client has retrieved the access token, it generates a nonce
N1 and posts both the token and N1 to the RS using the authz-info N1. The client also generates its OSCORE Recipient ID (see
endpoint and mechanisms specified in section 5.8 of Section 3.1 of [RFC8613]), ID1, for use with the keying material
[I-D.ietf-ace-oauth-authz] and Content-Format = application/ace+cbor. associated to the RS. The client posts the token, N1 and its
When using this profile, the communication with the authz-info Recipient ID to the RS using the authz-info endpoint and mechanisms
endpoint is not protected, except for update of access rights. specified in section 5.8 of [I-D.ietf-ace-oauth-authz] and Content-
Format = application/ace+cbor. When using this profile, the
communication with the authz-info endpoint is not protected, except
for update of access rights.
If the access token is valid, the RS replies to this request with a If the access token is valid, the RS replies to this request with a
2.01 (Created) response with Content-Format = application/ace+cbor, 2.01 (Created) response with Content-Format = application/ace+cbor,
which contains a nonce N2 in a CBOR map. Moreover, the server which contains a nonce N2 and its newly generated OSCORE Recipient
concatenates the input salt received in the token, N1, and N2 to ID, ID2, for use with the keying material associated to the client.
obtain the Master Salt of the OSCORE Security Context (see section 3 Moreover, the server concatenates the input salt received in the
of [RFC8613]). The RS then derives the complete Security Context token, N1, and N2 to obtain the Master Salt of the OSCORE Security
associated with the received token from it plus the parameters Context (see section 3 of [RFC8613]). The RS then derives the
received in the access token from the AS, following section 3.2 of complete Security Context associated with the received token from the
[RFC8613]. Master Salt, the OSCORE Recipient ID generated by the client (set as
its OSCORE Sender ID), its own OSCORE Recipient ID, plus the
parameters received in the access token from the AS, following
section 3.2 of [RFC8613].
After receiving the nonce N2, the client concatenates the input salt In a similar way, after receiving the nonce N2, the client
(received from the AS), N1 and N2 to obtain the Master Salt of the concatenates the input salt, N1 and N2 to obtain the Master Salt of
OSCORE Security Context (see section 3 of [RFC8613]). The client the OSCORE Security Context. The client then derives the complete
then derives the complete Security Context from the nonces plus the Security Context from the Master Salt, the OSCORE Recipient ID
parameters received from the AS. generated by the RS (set as its OSCORE Sender ID), its own OSCORE
Recipient ID, plus the parameters received from the AS.
Finally, the client sends a request protected with OSCORE to the RS. Finally, the client sends a request protected with OSCORE to the RS.
If the request verifies, the server stores the complete Security If the request verifies, the server stores the complete Security
Context state that is ready for use in protecting messages, and uses Context state that is ready for use in protecting messages, and uses
it in the response, and in further communications with the client, it in the response, and in further communications with the client,
until token expiration. This Security Context is discarded when a until token expiration. This Security Context is discarded when a
token (whether the same or different) is used to successfully derive token (whether the same or different) is used to successfully derive
a new Security Context for that client. a new Security Context for that client.
The use of random nonces during the exchange prevents the reuse of an The use of random nonces during the exchange prevents the reuse of an
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[RFC8613]). Therefore, the main requirement for the nonces is that [RFC8613]). Therefore, the main requirement for the nonces is that
they have a good amount of randomness. If random nonces were not they have a good amount of randomness. If random nonces were not
used, a node re-using a non-expired old token would be susceptible to used, a node re-using a non-expired old token would be susceptible to
on-path attackers provoking the creation of OSCORE messages using old on-path attackers provoking the creation of OSCORE messages using old
AEAD keys and nonces. AEAD keys and nonces.
After the whole message exchange has taken place, the client can After the whole message exchange has taken place, the client can
contact the AS to request an update of its access rights, sending a contact the AS to request an update of its access rights, sending a
similar request to the token endpoint that also includes an similar request to the token endpoint that also includes an
identifier so that the AS can find the correct OSCORE security identifier so that the AS can find the correct OSCORE security
material it has previously shared with the Client. This specific material it has previously shared with the client. This specific
identifier, which [I-D.ietf-ace-oauth-authz] encodes as a bstr, is identifier, encoded as a byte string, is assigned by the AS to be
formatted to include two OSCORE identifiers, namely ID context and unique in the sets of its OSCORE Security Contexts, and is not used
client ID, that are necessary to determine the correct OSCORE Input as input material to derive the full OSCORE Security Context.
material.
An overview of the profile flow for the OSCORE profile is given in An overview of the profile flow for the OSCORE profile is given in
Figure 1. The names of messages coincide with those of Figure 1. The names of messages coincide with those of
[I-D.ietf-ace-oauth-authz] when applicable. [I-D.ietf-ace-oauth-authz] when applicable.
C RS AS C RS AS
| | | | | |
| ----- POST /token ----------------------------> | | ----- POST /token ----------------------------> |
| | | | | |
| <---------------------------- Access Token ----- | | <---------------------------- Access Token ----- |
| + Access Information | | + Access Information |
| ---- POST /authz-info ---> | | | ---- POST /authz-info ---> | |
| (access_token, N1) | | | (access_token, N1, ID1) | |
| | | | | |
| <--- 2.01 Created (N2) --- | | | <- 2.01 Created (N2, ID2)- | |
| | | | | |
/Sec Context /Sec Context | /Sec Context /Sec Context |
derivation/ derivation/ | derivation/ derivation/ |
| | | | | |
| ---- OSCORE Request -----> | | | ---- OSCORE Request -----> | |
| | | | | |
| /proof-of-possession | | /proof-of-possession |
| Sec Context storage/ | | Sec Context storage/ |
| | | | | |
| <--- OSCORE Response ----- | | | <--- OSCORE Response ----- | |
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{ {
"req_aud" : "tempSensor4711", "req_aud" : "tempSensor4711",
"scope" : "read" "scope" : "read"
} }
Figure 2: Example C-to-AS POST /token request for an access token Figure 2: Example C-to-AS POST /token request for an access token
bound to a symmetric key. bound to a symmetric key.
If the client wants to update its access rights without changing an If the client wants to update its access rights without changing an
existing OSCORE Security Context, it MUST include in its POST request existing OSCORE Security Context, it MUST include in its POST request
to the token endpoint a req_cnf object. The req_cnf MUST include a to the token endpoint a req_cnf object. kid field carrying a CBOR
kid field carrying a bstr-wrapped CBOR array object containing the byte string containing the OSCORE_Input_Material Identifier (assigned
client's identifier (assigned as discussed in Section 3.2) and the as discussed in Section 3.2). This identifier, together with other
context identifier (if assigned as discussed in Section 3.2). The information such as audience (see Section 5.6.1 of
CBOR array is defined in Figure 3, and follows the notation of [I-D.ietf-ace-oauth-authz]), can be used by the AS to determine the
[RFC8610]. These identifiers, together with other information such shared secret bound to the proof-of-possession token and therefore
as audience (see Section 5.6.1 of [I-D.ietf-ace-oauth-authz]), can be MUST identify a symmetric key that was previously generated by the AS
used by the AS to determine the shared secret bound to the proof-of- as a shared secret for the communication between the client and the
possession token and therefore MUST identify a symmetric key that was RS. The AS MUST verify that the received value identifies a proof-
previously generated by the AS as a shared secret for the of-possession key that has previously been issued to the requesting
communication between the client and the RS. The AS MUST verify that client. If that is not the case, the Client-to-AS request MUST be
the received value identifies a proof-of-possession key that has declined with the error code 'invalid_request' as defined in
previously been issued to the requesting client. If that is not the Section 5.6.3 of [I-D.ietf-ace-oauth-authz].
case, the Client-to-AS request MUST be declined with the error code
'invalid_request' as defined in Section 5.6.3 of
[I-D.ietf-ace-oauth-authz].
kid_arr = [
clientId,
?ContextId
]
kid = bstr .cbor kid_arr
Figure 3: CDDL Notation of kid for Update of Access Rights
An example of such a request, with payload in CBOR diagnostic An example of such a request, with payload in CBOR diagnostic
notation without the tag and value abbreviations is reported in notation without the tag and value abbreviations is reported in
Figure 4 Figure 3
Header: POST (Code=0.02) Header: POST (Code=0.02)
Uri-Host: "as.example.com" Uri-Host: "as.example.com"
Uri-Path: "token" Uri-Path: "token"
Content-Format: "application/ace+cbor" Content-Format: "application/ace+cbor"
Payload: Payload:
{ {
"req_aud" : "tempSensor4711", "req_aud" : "tempSensor4711",
"scope" : "write", "scope" : "write",
"req_cnf" : { "req_cnf" : {
"kid" : << ["myclient","contextid1"] >> "kid" : h'01'
} }
Figure 4: Example C-to-AS POST /token request for updating rights to Figure 3: Example C-to-AS POST /token request for updating rights to
an access token bound to a symmetric key. an access token bound to a symmetric key.
3.2. AS-to-C: Access Token 3.2. AS-to-C: Access Token
After verifying the POST request to the token endpoint and that the After verifying the POST request to the token endpoint and that the
client is authorized to obtain an access token corresponding to its client is authorized to obtain an access token corresponding to its
access token request, the AS responds as defined in section 5.6.2 of access token request, the AS responds as defined in section 5.6.2 of
[I-D.ietf-ace-oauth-authz]. If the client request was invalid, or [I-D.ietf-ace-oauth-authz]. If the client request was invalid, or
not authorized, the AS returns an error response as described in not authorized, the AS returns an error response as described in
section 5.6.3 of [I-D.ietf-ace-oauth-authz]. section 5.6.3 of [I-D.ietf-ace-oauth-authz].
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client MUST use OSCORE towards all resource servers for which this client MUST use OSCORE towards all resource servers for which this
access token is valid, and follow Section 4.3 to derive the security access token is valid, and follow Section 4.3 to derive the security
context to run OSCORE. Usually it is assumed that constrained context to run OSCORE. Usually it is assumed that constrained
devices will be pre-configured with the necessary profile, so that devices will be pre-configured with the necessary profile, so that
this kind of profile negotiation can be omitted. this kind of profile negotiation can be omitted.
Moreover, the AS MUST send the following data: Moreover, the AS MUST send the following data:
o a master secret o a master secret
o a server identifier o an identifier of the OSCORE Input Material
o a client identifier
Additionally, the AS MAY send the following data, in the same Additionally, the AS MAY send the following data, in the same
response. response.
o a context identifier o a context identifier
o an AEAD algorithm o an AEAD algorithm
o an HMAC-based key derivation function (HKDF) algorithm o an HMAC-based key derivation function (HKDF) algorithm
o a salt o a salt
o the OSCORE version number o the OSCORE version number
This data is transported in the the OSCORE_Input_Material. The This data is transported in the the OSCORE_Input_Material. The
OSCORE_Input_Material is a CBOR map object, defined in Section 3.2.1. OSCORE_Input_Material is a CBOR map object, defined in Section 3.2.1.
This object is transported in the 'cnf' parameter of the access token This object is transported in the 'cnf' parameter of the access token
response as defined in Section 3.2 of [I-D.ietf-ace-oauth-params], as response as defined in Section 3.2 of [I-D.ietf-ace-oauth-params], as
the value of a field named 'osc', registered in Section 9.5 and the value of a field named 'osc', registered in Section 9.5 and
Section 9.6. Section 9.6.
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o the OSCORE version number o the OSCORE version number
This data is transported in the the OSCORE_Input_Material. The This data is transported in the the OSCORE_Input_Material. The
OSCORE_Input_Material is a CBOR map object, defined in Section 3.2.1. OSCORE_Input_Material is a CBOR map object, defined in Section 3.2.1.
This object is transported in the 'cnf' parameter of the access token This object is transported in the 'cnf' parameter of the access token
response as defined in Section 3.2 of [I-D.ietf-ace-oauth-params], as response as defined in Section 3.2 of [I-D.ietf-ace-oauth-params], as
the value of a field named 'osc', registered in Section 9.5 and the value of a field named 'osc', registered in Section 9.5 and
Section 9.6. Section 9.6.
The AS MUST assign an identifier to the RS (server identifier), and The AS MAY assign an identifier to the context (context identifier).
to the client (client identifier), and MAY assign an identifier to This identifier is used as ID Context in the OSCORE context as
the context (context identifier). These identifiers are then used as described in section 3.1 of [RFC8613]. If assigned, this parameters
Sender ID, Recipient ID and ID Context in the OSCORE context as MUST be communicated as the 'contextId' field in the
described in section 3.1 of [RFC8613]: specifically, the server OSCORE_Input_Material. The applications needs to consider that this
identifier is used as Sender ID of the node acting as RS in this identifier is sent in the clear and may reveal information about the
profile, and the client identifier is used as Sender ID of the node endpoints, as mentioned in section 12.8 of [RFC8613].
acting as ACE client. These parameters are sent as clientId,
serverId and (when assigned) contextId in the OSCORE_Input_Material.
ClientId and serverId MUST be included in the OSCORE_Input_Material,
contextId MUST be included when assigned. The applications need to
consider that these identifiers are sent in the clear and may reveal
information about the endpoints, as mentioned in section 12.8 of
[RFC8613]. The pair (client identifier, context identifier) MUST be
unique in the set of all clients for a single RS.
The master secret MUST be communicated as the 'ms' field in the 'osc' The master secret and the identifier of the OSCORE_Input_Material
field in the 'cnf' parameter of the access token response. If MUST be communicated as the 'ms' and 'id' field in the 'osc' field in
included, the AEAD algorithm is sent in the 'alg' parameter in the the 'cnf' parameter of the access token response. If included, the
AEAD algorithm is sent in the 'alg' parameter in the
OSCORE_Input_Material; the HKDF algorithm in the 'hkdf' parameter of OSCORE_Input_Material; the HKDF algorithm in the 'hkdf' parameter of
the OSCORE_Input_Material; a salt in the 'salt' parameter of the the OSCORE_Input_Material; a salt in the 'salt' parameter of the
OSCORE_Input_Material; and the OSCORE version in the 'version' OSCORE_Input_Material; and the OSCORE version in the 'version'
parameter of the OSCORE_Input_Material. parameter of the OSCORE_Input_Material.
The same parameters MUST be included in the claims associated with The same parameters MUST be included in the claims associated with
the access token. This profile RECOMMENDS the use of CBOR web token the access token. This profile RECOMMENDS the use of CBOR web token
(CWT) as specified in [RFC8392]. If the token is a CWT, the same (CWT) as specified in [RFC8392]. If the token is a CWT, the same
OSCORE_Input_Material structure defined above MUST be placed in the OSCORE_Input_Material structure defined above MUST be placed in the
'osc' field of the 'cnf' claim of this token. 'osc' field of the 'cnf' claim of this token.
We assume in this document that an RS is associated to one single AS,
which makes it possible for the AS to enforce uniqueness of
identifiers for each client sending requests to an RS. If this is
not the case, collisions of identifiers may occur at the RS, in which
case the RS needs to have a mechanism in place to disambiguate
identifiers or mitigate the effect of the collisions.
Moreover, implementers of this specification need to be aware that if
other authentication mechanisms are used to set up OSCORE between the
same client and RS, that do not rely on AS assigning identifiers,
collisions may happen and need to be mitigated. A mitigation example
would be to use distinct namespaces of identifiers for different
authentication mechanisms.
The AS MUST send different OSCORE_Input_Material (and therefore The AS MUST send different OSCORE_Input_Material (and therefore
different access tokens) to different authorized clients, in order different access tokens) to different authorized clients, in order
for the RS to differentiate between clients. for the RS to differentiate between clients.
Note that in Section 4.3 C sets the Sender ID of its Security Context Figure 4 shows an example of an AS response, with payload in CBOR
to the clientId value received and the Recipient ID to the serverId
value, and RS does the opposite.
Figure 5 shows an example of an AS response, with payload in CBOR
diagnostic notation without the tag and value abbreviations. The diagnostic notation without the tag and value abbreviations. The
access token has been truncated for readability. access token has been truncated for readability.
Header: Created (Code=2.01) Header: Created (Code=2.01)
Content-Type: "application/ace+cbor" Content-Type: "application/ace+cbor"
Payload: Payload:
{ {
"access_token" : h'8343a1010aa2044c53 ... "access_token" : h'8343a1010aa2044c53 ...
(remainder of access token (CWT) omitted for brevity)', (remainder of access token (CWT) omitted for brevity)',
"profile" : "coap_oscore", "profile" : "coap_oscore",
"expires_in" : "3600", "expires_in" : "3600",
"cnf" : { "cnf" : {
"osc" : { "osc" : {
"alg" : "AES-CCM-16-64-128", "id" : h'01',
"clientId" : h'00',
"serverId" : h'01',
"ms" : h'f9af838368e353e78888e1426bd94e6f' "ms" : h'f9af838368e353e78888e1426bd94e6f'
} }
} }
} }
Figure 5: Example AS-to-C Access Token response with OSCORE profile. Figure 4: Example AS-to-C Access Token response with OSCORE profile.
Figure 6 shows an example CWT Claims Set, including the relevant Figure 5 shows an example CWT Claims Set, including the relevant
OSCORE parameters in the 'cnf' claim, in CBOR diagnostic notation OSCORE parameters in the 'cnf' claim, in CBOR diagnostic notation
without tag and value abbreviations. without tag and value abbreviations.
{ {
"aud" : "tempSensorInLivingRoom", "aud" : "tempSensorInLivingRoom",
"iat" : "1360189224", "iat" : "1360189224",
"exp" : "1360289224", "exp" : "1360289224",
"scope" : "temperature_g firmware_p", "scope" : "temperature_g firmware_p",
"cnf" : { "cnf" : {
"osc" : { "osc" : {
"alg" : "AES-CCM-16-64-128", "ms" : h'f9af838368e353e78888e1426bd94e6f',
"clientId" : h'00', "id" : h'01'
"serverId" : h'01',
"ms" : h'f9af838368e353e78888e1426bd94e6f'
} }
} }
}
Figure 6: Example CWT Claims Set with OSCORE parameters. Figure 5: Example CWT Claims Set with OSCORE parameters.
The same CWT Claims Set as in Figure 6, using the value abbreviations The same CWT Claims Set as in Figure 5, using the value abbreviations
defined in [I-D.ietf-ace-oauth-authz] and [RFC8747] and encoded in defined in [I-D.ietf-ace-oauth-authz] and [RFC8747] and encoded in
CBOR is shown in Figure 7. The bytes in hexadecimal are reported in CBOR is shown in Figure 6. The bytes in hexadecimal are reported in
the first column, while their corresponding CBOR meaning is reported the first column, while their corresponding CBOR meaning is reported
after the '#' sign on the second column, for easiness of readability. after the '#' sign on the second column, for easiness of readability.
NOTE TO THE RFC EDITOR: before publishing, it should be checked (and NOTE TO THE RFC EDITOR: before publishing, it should be checked (and
in case fixed) that the values used below (which are not yet in case fixed) that the values used below (which are not yet
registered) are the final values registered in IANA. registered) are the final values registered in IANA.
A5 # map(5) A5 # map(5)
03 # unsigned(3) 63 # text(3)
617564 # "aud"
76 # text(22) 76 # text(22)
74656D7053656E736F72496E4C6976696E67526F6F6D 74656D7053656E736F72496E4C6976696E67526F6F6D
# "tempSensorInLivingRoom" # "tempSensorInLivingRoom"
06 # unsigned(6) 63 # text(3)
1A 5112D728 # unsigned(1360189224) 696174 # "iat"
04 # unsigned(4) 6A # text(10)
1A 51145DC8 # unsigned(1360289224) 31333630313839323234 # "1360189224"
09 # unsigned(9) 63 # text(3)
657870 # "exp"
6A # text(10)
31333630323839323234 # "1360289224"
65 # text(5)
73636F7065 # "scope"
78 18 # text(24) 78 18 # text(24)
74656D70657261747572655F67206669726D776172655F70 74656D70657261747572655F67206669726D776172655F70
# "temperature_g firmware_p" # "temperature_g firmware_p"
08 # unsigned(8) 63 # text(3)
636E66 # "cnf"
A1 # map(1) A1 # map(1)
04 # unsigned(4) 63 # text(3)
A4 # map(4) 6F7363 # "osc"
05 # unsigned(5) A2 # map(2)
0A # unsigned(10) 62 # text(2)
02 # unsigned(2) 6D73 # "ms"
46 # bytes(6)
636C69656E74 # "client"
03 # unsigned(3)
46 # bytes(6)
736572766572 # "server"
01 # unsigned(1)
50 # bytes(16) 50 # bytes(16)
F9AF838368E353E78888E1426BD94E6F F9AF838368E353E78888E1426BD94E6F
# "\xF9\xAF\x83\x83h\xE3S\xE7 # "\xF9\xAF\x83\x83h\xE3S\xE7
\x88\x88\xE1Bk\xD9No" \x88\x88\xE1Bk\xD9No"
62 # text(2)
6964 # "id"
41 # bytes(1)
01 # "\x01"
Figure 7: Example CWT Claims Set with OSCORE parameters, CBOR Figure 6: Example CWT Claims Set with OSCORE parameters, CBOR
encoded. encoded.
If the client has requested an update to its access rights using the If the client has requested an update to its access rights using the
same OSCORE Security Context, which is valid and authorized, the AS same OSCORE Security Context, which is valid and authorized, the AS
MUST omit the 'cnf' parameter in the response, and MUST carry the MUST omit the 'cnf' parameter in the response, and MUST carry the
client identifier and the context identifier (if it was set and OSCORE Input Material identifier in the 'kid' field in the 'cnf'
included in the initial access token response by the AS) in the 'kid' parameter of the token. This identifier needs to be included in the
field in the 'cnf' parameter of the token, with the same structure token in order for the RS to identify the correct OSCORE Input
defined in Figure 3. These identifiers need to be included in the Material.
token in order for the RS to identify the previously generated
Security Context.
Figure 8 shows an example of such an AS response, with payload in Figure 7 shows an example of such an AS response, with payload in
CBOR diagnostic notation without the tag and value abbreviations. CBOR diagnostic notation without the tag and value abbreviations.
The access token has been truncated for readability. The access token has been truncated for readability.
Header: Created (Code=2.01) Header: Created (Code=2.01)
Content-Type: "application/ace+cbor" Content-Type: "application/ace+cbor"
Payload: Payload:
{ {
"access_token" : h'8343a1010aa2044c53 ... "access_token" : h'8343a1010aa2044c53 ...
(remainder of access token (CWT) omitted for brevity)', (remainder of access token (CWT) omitted for brevity)',
"profile" : "coap_oscore", "profile" : "coap_oscore",
"expires_in" : "3600" "expires_in" : "3600"
} }
Figure 8: Example AS-to-C Access Token response with OSCORE profile, Figure 7: Example AS-to-C Access Token response with OSCORE profile,
for update of access rights. for update of access rights.
Figure 9 shows an example CWT Claims Set, containing the necessary Figure 8 shows an example CWT Claims Set, containing the necessary
OSCORE parameters in the 'cnf' claim for update of access rights, in OSCORE parameters in the 'cnf' claim for update of access rights, in
CBOR diagnostic notation without tag and value abbreviations. CBOR diagnostic notation without tag and value abbreviations.
{ {
"aud" : "tempSensorInLivingRoom", "aud" : "tempSensorInLivingRoom",
"iat" : "1360189224", "iat" : "1360189224",
"exp" : "1360289224", "exp" : "1360289224",
"scope" : "temperature_h", "scope" : "temperature_h",
"cnf" : { "cnf" : {
"kid" : h'43814100' "kid" : h'01'
} }
} }
Figure 9: Example CWT Claims Set with OSCORE parameters for update of Figure 8: Example CWT Claims Set with OSCORE parameters for update of
access rights. access rights.
3.2.1. The OSCORE_Input_Material 3.2.1. The OSCORE_Input_Material
An OSCORE_Input_Material is an object that represents the input An OSCORE_Input_Material is an object that represents the input
material to derive an OSCORE Security Context, i.e., the local set of material to derive an OSCORE Security Context, i.e., the local set of
information elements necessary to carry out the cryptographic information elements necessary to carry out the cryptographic
operations in OSCORE (Section 3.1 of [RFC8613]). In particular, the operations in OSCORE (Section 3.1 of [RFC8613]). In particular, the
OSCORE_Input_Material is defined to be serialized and transported OSCORE_Input_Material is defined to be serialized and transported
between nodes, as specified by this document, but can also be used by between nodes, as specified by this document, but can also be used by
skipping to change at page 14, line 23 skipping to change at page 13, line 20
| | label | | | | | | label | | | |
+-----------+-------+-------------+-------------------+-------------+ +-----------+-------+-------------+-------------------+-------------+
| version | 0 | unsigned | | OSCORE | | version | 0 | unsigned | | OSCORE |
| | | integer | | Version | | | | integer | | Version |
| | | | | | | | | | | |
| ms | 1 | byte string | | OSCORE | | ms | 1 | byte string | | OSCORE |
| | | | | Master | | | | | | Master |
| | | | | Secret | | | | | | Secret |
| | | | | value | | | | | | value |
| | | | | | | | | | | |
| clientId | 2 | byte string | | OSCORE | | id | 2 | byte string | | OSCORE |
| | | | | Sender ID | | | | | | Input |
| | | | | value of | | | | | | Material |
| | | | | the client, | | | | | | Identifier |
| | | | | OSCORE |
| | | | | Recipient |
| | | | | ID value of |
| | | | | the server |
| | | | | |
| serverId | 3 | byte string | | OSCORE |
| | | | | Sender ID |
| | | | | value of |
| | | | | the server, |
| | | | | OSCORE |
| | | | | Recipient |
| | | | | ID value of |
| | | | | the client |
| | | | | | | | | | | |
| hkdf | 4 | text string | [COSE.Algorithms] | OSCORE HKDF | | hkdf | 3 | text string | [COSE.Algorithms] | OSCORE HKDF |
| | | / integer | Values (HMAC- | value | | | | / integer | Values (HMAC- | value |
| | | | based) | | | | | | based) | |
| | | | | | | | | | | |
| alg | 5 | text string | [COSE.Algorithms] | OSCORE AEAD | | alg | 4 | text string | [COSE.Algorithms] | OSCORE AEAD |
| | | / integer | Values (AEAD) | Algorithm | | | | / integer | Values (AEAD) | Algorithm |
| | | | | value | | | | | | value |
| | | | | | | | | | | |
| salt | 6 | byte string | | an input to | | salt | 5 | byte string | | an input to |
| | | | | OSCORE | | | | | | OSCORE |
| | | | | Master Salt | | | | | | Master Salt |
| | | | | value | | | | | | value |
| | | | | | | | | | | |
| contextId | 7 | byte string | | OSCORE ID | | contextId | 6 | byte string | | OSCORE ID |
| | | | | Context | | | | | | Context |
| | | | | value | | | | | | value |
+-----------+-------+-------------+-------------------+-------------+ +-----------+-------+-------------+-------------------+-------------+
Table 1: OSCORE_Input_Material Parameters Table 1: OSCORE_Input_Material Parameters
version: This parameter identifies the OSCORE Version number, which version: This parameter identifies the OSCORE Version number, which
is an unsigned integer. For more information about this field, is an unsigned integer. For more information about this field,
see section 5.4 of [RFC8613]. In JSON, the "version" value is an see section 5.4 of [RFC8613]. In JSON, the "version" value is an
integer. In CBOR, the "version" type is int, and has label 0. integer. In CBOR, the "version" type is int, and has label 0.
ms: This parameter identifies the OSCORE Master Secret value, which ms: This parameter identifies the OSCORE Master Secret value, which
is a byte string. For more information about this field, see is a byte string. For more information about this field, see
section 3.1 of [RFC8613]. In JSON, the "ms" value is a Base64 section 3.1 of [RFC8613]. In JSON, the "ms" value is a Base64
encoded byte string. In CBOR, the "ms" type is bstr, and has encoded byte string. In CBOR, the "ms" type is bstr, and has
label 1. label 1.
clientId: This parameter identifies a client identifier as a byte id: This parameter identifies the OSCORE_Input_Material and is
string. This identifier is used as OSCORE Sender ID in the client encoded as a byte string. In JSON, the "id" value is a Base64
and OSCORE Recipient ID in the server. For more information about encoded byte string. In CBOR, the "id" type is byte string, and
this field, see section 3.1 of [RFC8613]. In JSON, the "clientId" has label 8.
value is a Base64 encoded byte string. In CBOR, the "clientId"
type is bstr, and has label 2.
serverId: This parameter identifies a server identifier as a byte
string. This identifier is used as OSCORE Sender ID in the server
and OSCORE Recipient ID in the client. For more information about
this field, see section 3.1 of [RFC8613]. In JSON, the "serverId"
value is a Base64 encoded byte string. In CBOR, the "serverId"
type is bstr, and has label 3.
hkdf: This parameter identifies the OSCORE HKDF Algorithm. For more hkdf: This parameter identifies the OSCORE HKDF Algorithm. For more
information about this field, see section 3.1 of [RFC8613]. The information about this field, see section 3.1 of [RFC8613]. The
values used MUST be registered in the IANA "COSE Algorithms" values used MUST be registered in the IANA "COSE Algorithms"
registry (see [COSE.Algorithms]) and MUST be HMAC-based HKDF registry (see [COSE.Algorithms]) and MUST be HMAC-based HKDF
algorithms. The value can either be the integer or the text algorithms. The value can either be the integer or the text
string value of the HMAC-based HKDF algorithm in the "COSE string value of the HMAC-based HKDF algorithm in the "COSE
Algorithms" registry. In JSON, the "hkdf" value is a case- Algorithms" registry. In JSON, the "hkdf" value is a case-
sensitive ASCII string or an integer. In CBOR, the "hkdf" type is sensitive ASCII string or an integer. In CBOR, the "hkdf" type is
tstr or int, and has label 4. tstr or int, and has label 4.
skipping to change at page 16, line 21 skipping to change at page 14, line 44
field, see section 3.1 of [RFC8613]. In JSON, the "salt" value is field, see section 3.1 of [RFC8613]. In JSON, the "salt" value is
a Base64 encoded byte string. In CBOR, the "salt" type is bstr, a Base64 encoded byte string. In CBOR, the "salt" type is bstr,
and has label 6. and has label 6.
contextId: This parameter identifies the security context as a byte contextId: This parameter identifies the security context as a byte
string. This identifier is used as OSCORE ID Context. For more string. This identifier is used as OSCORE ID Context. For more
information about this field, see section 3.1 of [RFC8613]. In information about this field, see section 3.1 of [RFC8613]. In
JSON, the "contextID" value is a Base64 encoded byte string. In JSON, the "contextID" value is a Base64 encoded byte string. In
CBOR, the "contextID" type is bstr, and has label 7. CBOR, the "contextID" type is bstr, and has label 7.
An example of JSON OSCORE_Input_Material is given in Figure 10. An example of JSON OSCORE_Input_Material is given in Figure 9.
"osc" : { "osc" : {
"alg" : "AES-CCM-16-64-128", "alg" : "AES-CCM-16-64-128",
"clientId" : b64'AA', "id" : b64'AQ=='
"serverId" : b64'AQ',
"ms" : b64'+a+Dg2jjU+eIiOFCa9lObw' "ms" : b64'+a+Dg2jjU+eIiOFCa9lObw'
} }
Figure 10: Example JSON OSCORE_Input_Material Figure 9: Example JSON OSCORE_Input_Material
The CDDL grammar describing the CBOR OSCORE_Input_Material is: The CDDL grammar describing the CBOR OSCORE_Input_Material is:
OSCORE_Input_Material = { OSCORE_Input_Material = {
? 0 => int, ; version ? 0 => int, ; version
? 1 => bstr, ; ms ? 1 => bstr, ; ms
? 2 => bstr, ; clientId ? 2 => bstr, ; id
? 3 => bstr, ; serverId ? 3 => tstr / int, ; hkdf
? 4 => tstr / int, ; hkdf ? 4 => tstr / int, ; alg
? 5 => tstr / int, ; alg ? 5 => bstr, ; salt
? 6 => bstr, ; salt ? 6 => bstr, ; contextId
? 7 => bstr, ; contextId
* int / tstr => any * int / tstr => any
} }
4. Client-RS Communication 4. Client-RS Communication
The following subsections describe the details of the POST request The following subsections describe the details of the POST request
and response to the authz-info endpoint between client and RS. The and response to the authz-info endpoint between client and RS. The
client generates a nonce N1, and posts it together with the token client generates a nonce N1 and an identifier ID1 unique in the sets
that includes the materials (e.g., OSCORE parameters) received from of its own Recipient IDs, and posts them together with the token that
the AS to the RS. The RS then generates a nonce N2, and uses includes the materials (e.g., OSCORE parameters) received from the AS
Section 3.2 of [RFC8613] to derive a security context based on a to the RS. The RS then generates a nonce N2 and an identifier ID2
shared master secret and the two nonces, established between client unique in the sets of its own Recipient IDs, and uses Section 3.2 of
and server. The nonces are encoded as bstr if CBOR is used, and as [RFC8613] to derive a security context based on a shared master
Base64 string if JSON is used. This security context is used to secret, the two nonces and the two identifiers, established between
protect all future communication between client and RS using OSCORE, client and server. The nonces and identifiers are encoded as CBOR
as long as the access token is valid. byte string if CBOR is used, and as Base64 string if JSON is used.
This security context is used to protect all future communication
between client and RS using OSCORE, as long as the access token is
valid.
Note that the RS and client authenticates themselves by generating Note that the RS and client authenticates themselves by generating
the shared OSCORE Security Context using the pop-key as master the shared OSCORE Security Context using the pop-key as master
secret. An attacker posting a valid token to the RS will not be able secret. An attacker posting a valid token to the RS will not be able
to generate a valid OSCORE context and thus not be able to prove to generate a valid OSCORE context and thus not be able to prove
possession of the pop-key. Additionally, the mutual authentication possession of the pop-key. Additionally, the mutual authentication
is only achieved after the client has successfully verified the is only achieved after the client has successfully verified the
response from the RS. response from the RS.
4.1. C-to-RS: POST to authz-info endpoint 4.1. C-to-RS: POST to authz-info endpoint
The client MUST generate a nonce value very unlikely to have been The client MUST generate a nonce value very unlikely to have been
previously used with the same input keying material. This profile previously used with the same input keying material. This profile
RECOMMENDS to use a 64-bit long random number as nonce's value. The RECOMMENDS to use a 64-bit long random number as nonce's value. The
client MUST store the nonce N1 as long as the response from the RS is client MUST store the nonce N1 as long as the response from the RS is
not received and the access token related to it is still valid. The not received and the access token related to it is still valid.
client MUST use CoAP and the Authorization Information resource as
described in section 5.8.1 of [I-D.ietf-ace-oauth-authz] to transport The client generates its own Recipient ID, ID1, for the OSCORE
the token and N1 to the RS. Security Context that it is establishing with the RS. By generating
its own Recipient ID, the client makes sure that it does not collide
with any of its Recipient IDs.
The client MUST use CoAP and the Authorization Information resource
as described in section 5.8.1 of [I-D.ietf-ace-oauth-authz] to
transport the token, N1 and ID1 to the RS.
Note that the use of the payload and the Content-Format is different Note that the use of the payload and the Content-Format is different
from what is described in section 5.8.1 of from what is described in section 5.8.1 of
[I-D.ietf-ace-oauth-authz], which only transports the token without [I-D.ietf-ace-oauth-authz], which only transports the token without
any CBOR wrapping. In this profile, the client MUST wrap the token any CBOR wrapping. In this profile, the client MUST wrap the token
and N1 in a CBOR map. The client MUST use the Content-Format and N1 in a CBOR map. The client MUST use the Content-Format
"application/ace+cbor" defined in section 8.14 of "application/ace+cbor" defined in section 8.14 of
[I-D.ietf-ace-oauth-authz]. The client MUST include the access token [I-D.ietf-ace-oauth-authz]. The client MUST include the access token
using the "access_token" parameter and N1 using the 'nonce1' using the "access_token" parameter, N1 using the 'nonce1' parameter
parameter defined in Section 4.1.1. defined in Section 4.1.1, and ID1 using the 'ace_client_recipientid'
parameter defined in Section 4.1.2.
The communication with the authz-info endpoint does not have to be The communication with the authz-info endpoint does not have to be
protected, except for the update of access rights case described protected, except for the update of access rights case described
below. below.
Note that a client may be required to re-POST the access token in Note that a client may be required to re-POST the access token in
order to complete a request, since an RS may delete a stored access order to complete a request, since an RS may delete a stored access
token (and associated Security Context) at any time, for example due token (and associated Security Context) at any time, for example due
to all storage space being consumed. This situation is detected by to all storage space being consumed. This situation is detected by
the client when it receives an AS Request Creation Hints response. the client when it receives an AS Request Creation Hints response.
Reposting the same access token will result in deriving a new OSCORE Reposting the same access token will result in deriving a new OSCORE
Security Context to be used with the RS, as different nonces will be Security Context to be used with the RS, as different nonces will be
used. used.
Figure 11 shows an example of the request sent from the client to the Figure 10 shows an example of the request sent from the client to the
RS, with payload in CBOR diagnostic notation without the tag and RS, with payload in CBOR diagnostic notation without the tag and
value abbreviations. The access token has been truncated for value abbreviations. The access token has been truncated for
readability. readability.
Header: POST (Code=0.02) Header: POST (Code=0.02)
Uri-Host: "rs.example.com" Uri-Host: "rs.example.com"
Uri-Path: "authz-info" Uri-Path: "authz-info"
Content-Format: "application/ace+cbor" Content-Format: "application/ace+cbor"
Payload: Payload:
{ {
"access_token": h'8343a1010aa2044c53 ... "access_token": h'8343a1010aa2044c53 ...
(remainder of access token (CWT) omitted for brevity)', (remainder of access token (CWT) omitted for brevity)',
"nonce1": h'018a278f7faab55a' "nonce1": h'018a278f7faab55a',
"ace_client_recipientid" : h'1645'
} }
Figure 11: Example C-to-RS POST /authz-info request using CWT Figure 10: Example C-to-RS POST /authz-info request using CWT
If the client has already posted a valid token, has already If the client has already posted a valid token, has already
established a security association with the RS, and wants to update established a security association with the RS, and wants to update
its access rights, the client can do so by posting the new token its access rights, the client can do so by posting the new token
(retrieved from the AS and containing the update of access rights) to (retrieved from the AS and containing the update of access rights) to
the /authz-info endpoint. The client MUST protect the request using the /authz-info endpoint. The client MUST protect the request using
the OSCORE Security Context established during the first token the OSCORE Security Context established during the first token
exchange. The client MUST only send the access token in the payload, exchange. The client MUST only send the access token in the payload,
no nonce is sent. After proper verification (see Section 4.2), the no nonce or identifier are sent. After proper verification (see
RS will replace the old token with the new one, maintaining the same Section 4.2), the RS will replace the old token with the new one,
Security Context. maintaining the same Security Context.
4.1.1. The Nonce 1 Parameter 4.1.1. The Nonce 1 Parameter
This parameter MUST be sent from the client to the RS, together with This parameter MUST be sent from the client to the RS, together with
the access token, if the ace profile used is coap_oscore. The the access token, if the ace profile used is coap_oscore. The
parameter is encoded as a byte string for CBOR-based interactions, parameter is encoded as a byte string for CBOR-based interactions,
and as a string (Base64 encoded binary) for JSON-based interactions. and as a string (Base64 encoded binary) for JSON-based interactions.
This parameter is registered in Section 9.2. This parameter is registered in Section 9.2.
4.1.2. The ace_client_recipientid Parameter
This parameter MUST be sent from the client to the RS, together with
the access token, if the ace profile used is coap_oscore. The
parameter is encoded as a byte string for CBOR-based interactions,
and as a string (Base64 encoded binary) for JSON-based interactions.
This parameter is registered in Section 9.2.
4.2. RS-to-C: 2.01 (Created) 4.2. RS-to-C: 2.01 (Created)
The RS MUST follow the procedures defined in section 5.8.1 of The RS MUST follow the procedures defined in section 5.8.1 of
[I-D.ietf-ace-oauth-authz]: the RS must verify the validity of the [I-D.ietf-ace-oauth-authz]: the RS must verify the validity of the
token. If the token is valid, the RS must respond to the POST token. If the token is valid, the RS must respond to the POST
request with 2.01 (Created). If the token is valid but is associated request with 2.01 (Created). If the token is valid but is associated
to claims that the RS cannot process (e.g., an unknown scope), or if to claims that the RS cannot process (e.g., an unknown scope), or if
any of the expected parameters in the 'osc' is missing (e.g., any of any of the expected parameters is missing (e.g., any of the mandatory
the mandatory parameters from the AS), or if any parameters received parameters from the AS or the identifier), or if any parameters
in the 'osc' is unrecognized, the RS must respond with an error received in the 'osc' is unrecognized, the RS must respond with an
response code equivalent to the CoAP code 4.00 (Bad Request). In the error response code equivalent to the CoAP code 4.00 (Bad Request).
latter two cases, the RS may provide additional information in the In the latter two cases, the RS may provide additional information in
error response, in order to clarify what went wrong. The RS may make the error response, in order to clarify what went wrong. The RS may
an introspection request (see Section 5.7.1 of make an introspection request (see Section 5.7.1 of
[I-D.ietf-ace-oauth-authz]) to validate the token before responding [I-D.ietf-ace-oauth-authz]) to validate the token before responding
to the POST request to the authz-info endpoint. to the POST request to the authz-info endpoint.
Additionally, the RS MUST generate a nonce N2 very unlikely to have Additionally, the RS MUST generate a nonce N2 very unlikely to have
been previously used with the same input keying material, and send it been previously used with the same input keying material, and its own
within the 2.01 (Created) response. The payload of the 2.01 Recipient ID, ID2. The RS makes sure that ID2 does not collide with
(Created) response MUST be a CBOR map containing the 'nonce2' any of its Recipient IDs. The RS MUST ensure that ID2 is different
parameter defined in Section 4.2.1, set to N2. This profile from the ace_client_recipientid. The RS sends N2 and ID2 within the
RECOMMENDS to use a 64-bit long random number as nonce's value. The 2.01 (Created) response. The payload of the 2.01 (Created) response
RS MUST use the Content-Format "application/ace+cbor" defined in MUST be a CBOR map containing the 'nonce2' parameter defined in
section 8.14 of [I-D.ietf-ace-oauth-authz]. Section 4.2.1, set to N2, and the 'ace_server_recipientid' parameter
defined in Section 4.2.2, set to ID2. This profile RECOMMENDS to use
a 64-bit long random number as nonce's value. The RS MUST use the
Content-Format "application/ace+cbor" defined in section 8.14 of
[I-D.ietf-ace-oauth-authz].
Figure 12 shows an example of the response sent from the RS to the Figure 11 shows an example of the response sent from the RS to the
client, with payload in CBOR diagnostic notation without the tag and client, with payload in CBOR diagnostic notation without the tag and
value abbreviations. value abbreviations.
Header: Created (Code=2.01) Header: Created (Code=2.01)
Content-Format: "application/ace+cbor" Content-Format: "application/ace+cbor"
Payload: Payload:
{ {
"nonce2": h'25a8991cd700ac01' "nonce2": h'25a8991cd700ac01',
"ace_server_recipientid" : h'0000'
} }
Figure 12: Example RS-to-C 2.01 (Created) response Figure 11: Example RS-to-C 2.01 (Created) response
As specified in section 5.8.3 of [I-D.ietf-ace-oauth-authz], the RS As specified in section 5.8.3 of [I-D.ietf-ace-oauth-authz], the RS
must notify the client with an error response with code 4.01 must notify the client with an error response with code 4.01
(Unauthorized) for any long running request before terminating the (Unauthorized) for any long running request before terminating the
session, when the access token expires. session, when the access token expires.
If the RS receives the token in a OSCORE protected message, it means If the RS receives the token in a OSCORE protected message, it means
that the client is requesting an update of access rights. The RS that the client is requesting an update of access rights. The RS
MUST discard any nonce in the request, if any was sent. The RS MUST MUST discard any nonce and identifiers in the request, if any was
check that the "kid" of the "cnf" parameter of the new access token sent. The RS MUST check that the "kid" of the "cnf" parameter of the
matches the OSCORE Security Context used to protect the message. If new access token matches the OSCORE Input Material of the context
that is the case, the RS MUST discard the old token and associate the used to protect the message. If that is the case, the RS MUST
new token to the Security Context identified by the "kid" value in discard the old token and associate the new token to the Security
the "cnf" parameter. The RS MUST respond with a 2.01 (Created) Context identified by the "kid" value in the "cnf" parameter. The RS
response protected with the same Security Context, with no payload. MUST respond with a 2.01 (Created) response protected with the same
Security Context, with no payload. If any verification fails, the RS
If any verification fails, the RS MUST respond with a 4.01 MUST respond with a 4.01 (Unauthorized) error response.
(Unauthorized) error response.
As specified in section 5.8.1 of [I-D.ietf-ace-oauth-authz], when As specified in section 5.8.1 of [I-D.ietf-ace-oauth-authz], when
receiving an updated access token with updated authorization receiving an updated access token with updated authorization
information from the client (see Section 3.1), it is recommended that information from the client (see Section 3.1), it is recommended that
the RS overwrites the previous token, that is only the latest the RS overwrites the previous token, that is only the latest
authorization information in the token received by the RS is valid. authorization information in the token received by the RS is valid.
This simplifies the process needed by the RS to keep track of This simplifies the process needed by the RS to keep track of
authorization information for a given client. authorization information for a given client.
4.2.1. The Nonce 2 Parameter 4.2.1. The Nonce 2 Parameter
This parameter MUST be sent from the RS to the Client if the ace This parameter MUST be sent from the RS to the client if the ace
profile used is coap_oscore. The parameter is encoded as a byte profile used is coap_oscore. The parameter is encoded as a byte
string for CBOR-based interactions, and as a string (Base64 encoded string for CBOR-based interactions, and as a string (Base64 encoded
binary) for JSON-based interactions. This parameter is registered in binary) for JSON-based interactions. This parameter is registered in
Section 9.2. Section 9.2
4.2.2. The ace_server_recipientid Parameter
This parameter MUST be sent from the RS to the client if the ace
profile used is coap_oscore. The parameter is encoded as a byte
string for CBOR-based interactions, and as a string (Base64 encoded
binary) for JSON-based interactions. This parameter is registered in
Section 9.2
4.3. OSCORE Setup 4.3. OSCORE Setup
Once receiving the 2.01 (Created) response from the RS, following the Once receiving the 2.01 (Created) response from the RS, following the
POST request to authz-info endpoint, the client MUST extract the bstr POST request to authz-info endpoint, the client MUST extract the bstr
nonce N2 from the 'nonce2' parameter in the CBOR map in the payload nonce N2 from the 'nonce2' parameter in the CBOR map in the payload
of the response. Then, the client MUST set the Master Salt of the of the response. Then, the client MUST set the Master Salt of the
Security Context created to communicate with the RS to the Security Context created to communicate with the RS to the
concatenation of salt, N1, and N2, in this order: Master Salt = concatenation of salt, N1, and N2, in this order: Master Salt =
salt | N1 | N2, where | denotes byte string concatenation, where salt salt | N1 | N2, where | denotes byte string concatenation, where salt
is the CBOR byte string received from the AS in Section 3.2, and is the CBOR byte string received from the AS in Section 3.2, and
where N1 and N2 are the two nonces encoded as CBOR byte strings. An where N1 and N2 are the two nonces encoded as CBOR byte strings. An
example of Master Salt construction using CBOR encoding is given in example of Master Salt construction using CBOR encoding is given in
Figure 13. Figure 12.
N1, N2 and input salt expressed in CBOR diagnostic notation: N1, N2 and input salt expressed in CBOR diagnostic notation:
nonce1 = h'018a278f7faab55a' nonce1 = h'018a278f7faab55a'
nonce2 = h'25a8991cd700ac01' nonce2 = h'25a8991cd700ac01'
input salt = h'f9af838368e353e78888e1426bd94e6f' input salt = h'f9af838368e353e78888e1426bd94e6f'
N1, N2 and input salt as CBOR encoded byte strings: N1, N2 and input salt as CBOR encoded byte strings:
nonce1 = 0x48018a278f7faab55a nonce1 = 0x48018a278f7faab55a
nonce2 = 0x4825a8991cd700ac01 nonce2 = 0x4825a8991cd700ac01
input salt = 0x50f9af838368e353e78888e1426bd94e6f input salt = 0x50f9af838368e353e78888e1426bd94e6f
Master Salt = 0x50 f9af838368e353e78888e1426bd94e6f 48 018a278f7faab55a 48 25a8991cd700ac01 Master Salt = 0x50 f9af838368e353e78888e1426bd94e6f 48 018a278f7faab55a 48 25a8991cd700ac01
Figure 13: Example of Master Salt construction using CBOR encoding Figure 12: Example of Master Salt construction using CBOR encoding
If JSON is used instead of CBOR, the Master Salt of the Security If JSON is used instead of CBOR, the Master Salt of the Security
Context is the Base64 encoding of the concatenation of the same Context is the Base64 encoding of the concatenation of the same
parameters, each of them prefixed by their size, encoded in 1 byte. parameters, each of them prefixed by their size, encoded in 1 byte.
When using JSON, the nonces and input salt have a maximum size of 255 When using JSON, the nonces and input salt have a maximum size of 255
bytes. An example of Master Salt construction using Base64 encoding bytes. An example of Master Salt construction using Base64 encoding
is given in Figure 14. is given in Figure 13.
N1, N2 and input salt values: N1, N2 and input salt values:
nonce1 = 0x018a278f7faab55a (8 bytes) nonce1 = 0x018a278f7faab55a (8 bytes)
nonce2 = 0x25a8991cd700ac01 (8 bytes) nonce2 = 0x25a8991cd700ac01 (8 bytes)
input salt = 0xf9af838368e353e78888e1426bd94e6f (16 bytes) input salt = 0xf9af838368e353e78888e1426bd94e6f (16 bytes)
Input to Base64 encoding: 0x10 f9af838368e353e78888e1426bd94e6f 08 018a278f7faab55a 08 25a8991cd700ac01 Input to Base64 encoding: 0x10 f9af838368e353e78888e1426bd94e6f 08 018a278f7faab55a 08 25a8991cd700ac01
Master Salt = b64'EPmvg4No41PniIjhQmvZTm8IAYonj3+qtVoIJaiZHNcArAE=' Master Salt = b64'EPmvg4No41PniIjhQmvZTm8IAYonj3+qtVoIJaiZHNcArAE='
Figure 14: Example of Master Salt construction using Base64 encoding Figure 13: Example of Master Salt construction using Base64 encoding
The client MUST set the Master Secret, Sender ID and Recipient ID The client MUST set the Sender ID to the ace_server_recipientid
from the parameters received from the AS in Section 3.2. The client received in Section 4.2, and the Recipient ID to the
MUST set the AEAD Algorithm, ID Context, HKDF, and OSCORE Version ace_client_recipientid sent in Section 4.1. The client MUST set the
from the parameters received from the AS in Section 3.2, if present. Master Secret from the parameter received from the AS in Section 3.2.
In case an optional parameter is omitted, the default value SHALL be The client MUST set the AEAD Algorithm, ID Context, HKDF, and OSCORE
used as described in sections 3.2 and 5.4 of [RFC8613]. After that, Version from the parameters received from the AS in Section 3.2, if
the client MUST derive the complete Security Context following present. In case an optional parameter is omitted, the default value
section 3.2.1 of [RFC8613]. From this point on, the client MUST use SHALL be used as described in sections 3.2 and 5.4 of [RFC8613].
this Security Context to communicate with the RS when accessing the After that, the client MUST derive the complete Security Context
resources as specified by the authorization information. following section 3.2.1 of [RFC8613]. From this point on, the client
MUST use this Security Context to communicate with the RS when
accessing the resources as specified by the authorization
information.
If any of the expected parameters is missing (e.g., any of the If any of the expected parameters is missing (e.g., any of the
mandatory parameters from the AS, the client MUST stop the exchange, mandatory parameters from the AS or the RS), or if
and MUST NOT derive the Security Context. The client MAY restart the ace_client_recipientid equals ace_server_recipientid, then the client
exchange, to get the correct security material. MUST stop the exchange, and MUST NOT derive the Security Context.
The client MAY restart the exchange, to get the correct security
material.
The client then uses this Security Context to send requests to RS The client then uses this Security Context to send requests to RS
using OSCORE. using OSCORE.
After sending the 2.01 (Created) response, the RS MUST set the Master After sending the 2.01 (Created) response, the RS MUST set the Master
Salt of the Security Context created to communicate with the client Salt of the Security Context created to communicate with the client
to the concatenation of salt, N1, and N2, in the same way described to the concatenation of salt, N1, and N2, in the same way described
above. An example of Master Salt construction using CBOR encoding is above. An example of Master Salt construction using CBOR encoding is
given in Figure 13 and using Base64 encoding is given in Figure 14. given in Figure 12 and using Base64 encoding is given in Figure 13.
The RS MUST set the Master Secret, Sender ID and Recipient ID from The RS MUST set the Sender ID from the ace_client_recipientid
the parameters, received from the AS and forwarded by the client in received in Section 4.1, and the Recipient ID from the
the access token in Section 4.1 after validation of the token as ace_server_recipientid sent in Section 4.2. The RS MUST set the
specified in Section 4.2. The RS MUST set the AEAD Algorithm, ID Master Secret from the parameter, received from the AS and forwarded
Context, HKDF, and OSCORE Version from the parameters received from by the client in the access token in Section 4.1 after validation of
the AS and forwarded by the client in the access token in Section 4.1 the token as specified in Section 4.2. The RS MUST set the AEAD
after validation of the token as specified in Section 4.2, if Algorithm, ID Context, HKDF, and OSCORE Version from the parameters
present. In case an optional parameter is omitted, the default value received from the AS and forwarded by the client in the access token
SHALL be used as described in sections 3.2 and 5.4 of [RFC8613]. in Section 4.1 after validation of the token as specified in
After that, the RS MUST derive the complete Security Context Section 4.2, if present. In case an optional parameter is omitted,
following section 3.2.1 of [RFC8613], and MUST associate this the default value SHALL be used as described in sections 3.2 and 5.4
of [RFC8613]. After that, the RS MUST derive the complete Security
Context following section 3.2.1 of [RFC8613], and MUST associate this
Security Context with the authorization information from the access Security Context with the authorization information from the access
token. token.
The RS then uses this Security Context to verify requests and send The RS then uses this Security Context to verify requests and send
responses to C using OSCORE. If OSCORE verification fails, error responses to C using OSCORE. If OSCORE verification fails, error
responses are used, as specified in section 8 of [RFC8613]. responses are used, as specified in section 8 of [RFC8613].
Additionally, if OSCORE verification succeeds, the verification of Additionally, if OSCORE verification succeeds, the verification of
access rights is performed as described in section Section 4.4. The access rights is performed as described in section Section 4.4. The
RS MUST NOT use the Security Context after the related token has RS MUST NOT use the Security Context after the related token has
expired, and MUST respond with a unprotected 4.01 (Unauthorized) expired, and MUST respond with a unprotected 4.01 (Unauthorized)
error message to requests received that correspond to a Security error message to requests received that correspond to a Security
Context with an expired token. Context with an expired token.
Note that the ID Context can be assigned by the AS, communicated and Note that the ID Context can be assigned by the AS, communicated and
set in both the RS and client after the exchange specified in this set in both the RS and client after the exchange specified in this
profile is executed. Subsequently, client and RS can update their ID profile is executed. Subsequently, client and RS can update their ID
Context by running a mechanism such as the one defined in Context by running a mechanism such as the one defined in
Appendix B.2 of [RFC8613] if they support it. In that case, the ID Appendix B.2 of [RFC8613] if they both support it and are configured
Context in the OSCORE Security Context will not match the "contextId" to do so. In that case, the ID Context in the OSCORE Security
parameter of the corresponding OSCORE_Input_Material. That is fine, Context will not match the "contextId" parameter of the corresponding
as long as the nodes store and use the "contextId" value to identify OSCORE_Input_Material. Running Appendix B.2 results in the keying
the correct OSCORE_Input_Material at the AS. material in the Security Contexts of client and RS being updated;
this same result can also be achieved by the client reposting the
access token as described in Section 4.1, but without updating the ID
Context.
4.4. Access rights verification 4.4. Access rights verification
The RS MUST follow the procedures defined in section 5.8.2 of The RS MUST follow the procedures defined in section 5.8.2 of
[I-D.ietf-ace-oauth-authz]: if an RS receives an OSCORE-protected [I-D.ietf-ace-oauth-authz]: if an RS receives an OSCORE-protected
request from a client, then the RS processes it according to request from a client, then the RS processes it according to
[RFC8613]. If OSCORE verification succeeds, and the target resource [RFC8613]. If OSCORE verification succeeds, and the target resource
requires authorization, the RS retrieves the authorization requires authorization, the RS retrieves the authorization
information using the access token associated to the Security information using the access token associated to the Security
Context. The RS then must verify that the authorization information Context. The RS then must verify that the authorization information
skipping to change at page 24, line 22 skipping to change at page 23, line 51
Authorization for Constrained Environments (ACE) framework Authorization for Constrained Environments (ACE) framework
[I-D.ietf-ace-oauth-authz]. Thus the general security considerations [I-D.ietf-ace-oauth-authz]. Thus the general security considerations
from the framework also apply to this profile. from the framework also apply to this profile.
Furthermore the general security considerations of OSCORE [RFC8613] Furthermore the general security considerations of OSCORE [RFC8613]
also apply to this specific use of the OSCORE protocol. also apply to this specific use of the OSCORE protocol.
As previously stated, the proof-of-possession in this profile is As previously stated, the proof-of-possession in this profile is
performed by both parties verifying that they have established the performed by both parties verifying that they have established the
same Security Context, as specified in Section 4.3, which means that same Security Context, as specified in Section 4.3, which means that
both the OSCORE request and OSCORE pass verification. RS both the OSCORE request and OSCORE response pass verification. RS
authentication requires both that the client trusts the AS and that authentication requires both that the client trusts the AS and that
the OSCORE response from the RS pass verification. the OSCORE response from the RS pass verification.
OSCORE is designed to secure point-to-point communication, providing OSCORE is designed to secure point-to-point communication, providing
a secure binding between the request and the response(s). Thus the a secure binding between the request and the response(s). Thus the
basic OSCORE protocol is not intended for use in point-to-multipoint basic OSCORE protocol is not intended for use in point-to-multipoint
communication (e.g., multicast, publish-subscribe). Implementers of communication (e.g., multicast, publish-subscribe). Implementers of
this profile should make sure that their usecase corresponds to the this profile should make sure that their usecase corresponds to the
expected use of OSCORE, to prevent weakening the security assurances expected use of OSCORE, to prevent weakening the security assurances
provided by OSCORE. provided by OSCORE.
skipping to change at page 25, line 48 skipping to change at page 25, line 32
The token is sent in the clear to the authz-info endpoint, so if a The token is sent in the clear to the authz-info endpoint, so if a
client uses the same single token from multiple locations with client uses the same single token from multiple locations with
multiple Resource Servers, it can risk being tracked by the token's multiple Resource Servers, it can risk being tracked by the token's
value even when the access token is encrypted. value even when the access token is encrypted.
The nonces exchanged in the request and response to the authz-info The nonces exchanged in the request and response to the authz-info
endpoint are also sent in the clear, so using random nonces is best endpoint are also sent in the clear, so using random nonces is best
for privacy (as opposed to, e.g., a counter, that might leak some for privacy (as opposed to, e.g., a counter, that might leak some
information about the client). information about the client).
The AS is the party tasked with assigning the identifiers used in The identifiers used in OSCORE, negotiated between client and RS are
OSCORE, which are privacy sensitive (see Section 12.8 of [RFC8613]), privacy sensitive (see Section 12.8 of [RFC8613]), and could reveal
and which could reveal information about the client, or may be used information about the client, or may be used for correlating requests
for correlating requests from one client. from one client.
Note that some information might still leak after OSCORE is Note that some information might still leak after OSCORE is
established, due to observable message sizes, the source, and the established, due to observable message sizes, the source, and the
destination addresses. destination addresses.
9. IANA Considerations 9. IANA Considerations
Note to RFC Editor: Please replace all occurrences of "[[this Note to RFC Editor: Please replace all occurrences of "[[this
specification]]" with the RFC number of this specification and delete specification]]" with the RFC number of this specification and delete
this paragraph. this paragraph.
skipping to change at page 26, line 44 skipping to change at page 26, line 28
o Parameter name: nonce1 o Parameter name: nonce1
o Parameter usage location: client-rs request o Parameter usage location: client-rs request
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): [[this specification]] o Specification Document(s): [[this specification]]
o Parameter name: nonce2 o Parameter name: nonce2
o Parameter usage location: rs-client response o Parameter usage location: rs-client response
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): [[this specification]] o Specification Document(s): [[this specification]]
o Parameter name: ace_client_recipientid
o Parameter usage location: client-rs request
o Change Controller: IESG
o Specification Document(s): [[this specification]]
o Parameter name: ace_server_recipientid
o Parameter usage location: rs-client response
o Change Controller: IESG
o Specification Document(s): [[this specification]]
9.3. OAuth Parameters CBOR Mappings Registry 9.3. OAuth Parameters CBOR Mappings Registry
The following registrations are done for the OAuth Parameters CBOR The following registrations are done for the OAuth Parameters CBOR
Mappings Registry following the procedure specified in section 8.10 Mappings Registry following the procedure specified in section 8.10
of [I-D.ietf-ace-oauth-authz]: of [I-D.ietf-ace-oauth-authz]:
o Name: nonce1 o Name: nonce1
o CBOR Key: TBD1 o CBOR Key: TBD1
o Value Type: bstr o Value Type: bstr
o Reference: [[this specification]] o Reference: [[this specification]]
o Name: nonce2 o Name: nonce2
o CBOR Key: TBD2 o CBOR Key: TBD2
o Value Type: bstr o Value Type: bstr
o Reference: [[this specification]] o Reference: [[this specification]]
o Name: ace_client_recipientid
o CBOR Key: TBD3
o Value Type: bstr
o Reference: [[this specification]]
o Name: ace_server_recipientid
o CBOR Key: TBD4
o Value Type: bstr
o Reference: [[this specification]]
9.4. OSCORE Security Context Parameters Registry 9.4. OSCORE Security Context Parameters Registry
It is requested that IANA create a new registry entitled "OSCORE It is requested that IANA create a new registry entitled "OSCORE
Security Context Parameters" registry. The registry is to be created Security Context Parameters" registry. The registry is to be created
as Expert Review Required. Guidelines for the experts is provided as Expert Review Required. Guidelines for the experts is provided
Section 9.7. It should be noted that in addition to the expert Section 9.7. It should be noted that in addition to the expert
review, some portions of the registry require a specification, review, some portions of the registry require a specification,
potentially on standards track, be supplied as well. potentially on standards track, be supplied as well.
skipping to change at page 29, line 42 skipping to change at page 29, line 42
Framework (ACE-OAuth)", draft-ietf-ace-oauth-authz-35 Framework (ACE-OAuth)", draft-ietf-ace-oauth-authz-35
(work in progress), June 2020. (work in progress), June 2020.
[I-D.ietf-ace-oauth-params] [I-D.ietf-ace-oauth-params]
Seitz, L., "Additional OAuth Parameters for Authorization Seitz, L., "Additional OAuth Parameters for Authorization
in Constrained Environments (ACE)", draft-ietf-ace-oauth- in Constrained Environments (ACE)", draft-ietf-ace-oauth-
params-13 (work in progress), April 2020. params-13 (work in progress), April 2020.
[I-D.ietf-cbor-7049bis] [I-D.ietf-cbor-7049bis]
Bormann, C. and P. Hoffman, "Concise Binary Object Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", draft-ietf-cbor-7049bis-14 (work Representation (CBOR)", draft-ietf-cbor-7049bis-16 (work
in progress), June 2020. in progress), September 2020.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252, Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014, DOI 10.17487/RFC7252, June 2014,
<https://www.rfc-editor.org/info/rfc7252>. <https://www.rfc-editor.org/info/rfc7252>.
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