| OAuth Working Group | N. Sakimura |
| Internet-Draft | Nomura Research Institute |
| Intended status: Standards Track | J. Bradley |
| Expires: December 12, 2019 | Yubico |
| June 10, 2019 |
The OAuth 2.0 Authorization Framework: JWT Secured Authorization Request (JAR)
draft-ietf-oauth-jwsreq-19
The authorization request in OAuth 2.0 described in RFC 6749 utilizes query parameter serialization, which means that Authorization Request parameters are encoded in the URI of the request and sent through user agents such as web browsers. While it is easy to implement, it means that (a) the communication through the user agents are not integrity protected and thus the parameters can be tainted, and (b) the source of the communication is not authenticated. Because of these weaknesses, several attacks to the protocol have now been put forward.
This document introduces the ability to send request parameters in a JSON Web Token (JWT) instead, which allows the request to be signed with JSON Web Signature (JWS) and encrypted with JSON Web Encryption (JWE) so that the integrity, source authentication and confidentiality property of the Authorization Request is attained. The request can be sent by value or by reference.
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.
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This Internet-Draft will expire on December 12, 2019.
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The Authorization Request in OAuth 2.0 utilizes query parameter serialization and is typically sent through user agents such as web browsers.
For example, the parameters response_type, client_id, state, and redirect_uri are encoded in the URI of the request:
GET /authorize?response_type=code&client_id=s6BhdRkqt3&state=xyz
&redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb HTTP/1.1
Host: server.example.com
While it is easy to implement, the encoding in the URI does not allow application layer security with confidentiality and integrity protection to be used. While TLS is used to offer communication security between the Client and the user-agent as well as the user-agent and the Authorization Server, TLS sessions are terminated in the user-agent. In addition, TLS sessions may be terminated prematurely at some middlebox (such as a load balancer).
As the result, the Authorization Request of [RFC6749] has shortcomings in that:
Due to these inherent weaknesses, several attacks against the protocol, such as Redirection URI rewriting and Mix-up attack [FETT], have been identified.
The use of application layer security mitigates these issues.
The use of application layer security allows requests to be prepared by a third party so that a client application cannot request more permissions than previously agreed. This offers an additional degree of privacy protection.
Furthermore, the request by reference allows the reduction of over-the-wire overhead.
The JWT encoding has been chosen because of
The parameters request and request_uri are introduced as additional authorization request parameters for the OAuth 2.0 flows. The request parameter is a JSON Web Token (JWT) whose JWT Claims Set holds the JSON encoded OAuth 2.0 authorization request parameters. This JWT is integrity protected and source authenticated using JWS.
The JWT can be passed to the authorization endpoint by reference, in which case the parameter request_uri is used instead of the request.
Using JWT as the request encoding instead of query parameters has several advantages:
There are a few cases that request by reference is useful such as:
This capability is in use by OpenID Connect [OpenID.Core].
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.
For the purposes of this specification, the following terms and definitions in addition to what is defined in OAuth 2.0 Framework, JSON Web Signature, and JSON Web Encryption apply.
JWT that holds an OAuth 2.0 authorization request as JWT Claims Set
Absolute URI from which the Request Object can be obtained
The following abbreviations are common to this specification.
A Request Object is used to provide authorization request parameters for an OAuth 2.0 authorization request. It MUST contains all the OAuth 2.0 authorization request parameters including extension parameters. The parameters are represented as the JWT claims. Parameter names and string values MUST be included as JSON strings. Since Request Objects are handled across domains and potentially outside of a closed ecosystem, per section 8.1 of [RFC8259], these JSON strings MUST be encoded using UTF-8 [RFC3629]. Numerical values MUST be included as JSON numbers. It MAY include any extension parameters. This JSON constitutes the JWT Claims Set defined in JWT. The JWT Claims Set is then signed or signed and encrypted.
To sign, JSON Web Signature (JWS) is used. The result is a JWS signed JWT. If signed, the Authorization Request Object SHOULD contain the Claims iss (issuer) and aud (audience) as members, with their semantics being the same as defined in the JWT specification. The value of aud should be the value of the Authorization Server (AS) issuer as defined in RFC8414.
To encrypt, JWE is used. When both signature and encryption are being applied, the JWT MUST be signed then encrypted as advised in the section 11.2 of [RFC7519]. The result is a Nested JWT, as defined in [RFC7519].
The Authorization Request Object MAY be sent by value as described in Section 5.1 or by reference as described in Section 5.2.
request and request_uri parameters MUST NOT be included in Request Objects.
The following is an example of the Claims in a Request Object before base64url encoding and signing. Note that it includes extension variables such as "nonce" and "max_age".
{
"iss": "s6BhdRkqt3",
"aud": "https://server.example.com",
"response_type": "code id_token",
"client_id": "s6BhdRkqt3",
"redirect_uri": "https://client.example.org/cb",
"scope": "openid",
"state": "af0ifjsldkj",
"nonce": "n-0S6_WzA2Mj",
"max_age": 86400
}
Signing it with the RS256 algorithm results in this Request Object value (with line wraps within values for display purposes only):
eyJhbGciOiJSUzI1NiIsImtpZCI6ImsyYmRjIn0.ew0KICJpc3MiOiAiczZCaGRSa3 F0MyIsDQogImF1ZCI6ICJodHRwczovL3NlcnZlci5leGFtcGxlLmNvbSIsDQogInJl c3BvbnNlX3R5cGUiOiAiY29kZSBpZF90b2tlbiIsDQogImNsaWVudF9pZCI6ICJzNk JoZFJrcXQzIiwNCiAicmVkaXJlY3RfdXJpIjogImh0dHBzOi8vY2xpZW50LmV4YW1w bGUub3JnL2NiIiwNCiAic2NvcGUiOiAib3BlbmlkIiwNCiAic3RhdGUiOiAiYWYwaW Zqc2xka2oiLA0KICJub25jZSI6ICJuLTBTNl9XekEyTWoiLA0KICJtYXhfYWdlIjog ODY0MDAsDQogImNsYWltcyI6IA0KICB7DQogICAidXNlcmluZm8iOiANCiAgICB7DQ ogICAgICJnaXZlbl9uYW1lIjogeyJlc3NlbnRpYWwiOiB0cnVlfSwNCiAgICAgIm5p Y2tuYW1lIjogbnVsbCwNCiAgICAgImVtYWlsIjogeyJlc3NlbnRpYWwiOiB0cnVlfS wNCiAgICAgImVtYWlsX3ZlcmlmaWVkIjogeyJlc3NlbnRpYWwiOiB0cnVlfSwNCiAg ICAgInBpY3R1cmUiOiBudWxsDQogICAgfSwNCiAgICJpZF90b2tlbiI6IA0KICAgIH sNCiAgICAgImdlbmRlciI6IG51bGwsDQogICAgICJiaXJ0aGRhdGUiOiB7ImVzc2Vu dGlhbCI6IHRydWV9LA0KICAgICAiYWNyIjogeyJ2YWx1ZXMiOiBbInVybjptYWNlOm luY29tbW9uOmlhcDpzaWx2ZXIiXX0NCiAgICB9DQogIH0NCn0.nwwnNsk1-Zkbmnvs F6zTHm8CHERFMGQPhos-EJcaH4Hh-sMgk8ePrGhw_trPYs8KQxsn6R9Emo_wHwajyF KzuMXZFSZ3p6Mb8dkxtVyjoy2GIzvuJT_u7PkY2t8QU9hjBcHs68PkgjDVTrG1uRTx 0GxFbuPbj96tVuj11pTnmFCUR6IEOXKYr7iGOCRB3btfJhM0_AKQUfqKnRlrRscc8K ol-cSLWoYE9l5QqholImzjT_cMnNIznW9E7CDyWXTsO70xnB4SkG6pXfLSjLLlxmPG iyon_-Te111V8uE83IlzCYIb_NMXvtTIVc1jpspnTSD7xMbpL-2QgwUsAlMGzw
The following RSA public key, represented in JWK format, can be used to validate the Request Object signature in this and subsequent Request Object examples (with line wraps within values for display purposes only):
{
"kty":"RSA",
"kid":"k2bdc",
"n":"y9Lqv4fCp6Ei-u2-ZCKq83YvbFEk6JMs_pSj76eMkddWRuWX2aBKGHAtKlE5P
7_vn__PCKZWePt3vGkB6ePgzAFu08NmKemwE5bQI0e6kIChtt_6KzT5OaaXDF
I6qCLJmk51Cc4VYFaxgqevMncYrzaW_50mZ1yGSFIQzLYP8bijAHGVjdEFgZa
ZEN9lsn_GdWLaJpHrB3ROlS50E45wxrlg9xMncVb8qDPuXZarvghLL0HzOuYR
adBJVoWZowDNTpKpk2RklZ7QaBO7XDv3uR7s_sf2g-bAjSYxYUGsqkNA9b3xV
W53am_UZZ3tZbFTIh557JICWKHlWj5uzeJXaw",
"e":"AQAB"
}
The client constructs the authorization request URI by adding one of the following parameters but not both to the query component of the authorization endpoint URI using the application/x-www-form-urlencoded format:
The client directs the resource owner to the constructed URI using an HTTP redirection response, or by other means available to it via the user-agent.
For example, the client directs the end user's user-agent to make the following HTTPS request:
GET /authz?request=eyJhbG..AlMGzw HTTP/1.1 Host: server.example.com
The value for the request parameter is abbreviated for brevity.
The authorization request object MUST be one of the following:
The client MAY send the parameters included in the request object duplicated in the query parameters as well for the backward compatibility etc. However, the authorization server supporting this specification MUST only use the parameters included in the request object.
The Client sends the Authorization Request as a Request Object to the Authorization Endpoint as the request parameter value.
The following is an example of an Authorization Request using the request parameter (with line wraps within values for display purposes only):
https://server.example.com/authorize?
request=eyJhbGciOiJSUzI1NiIsImtpZCI6ImsyYmRjIn0.ew0KICJpc3MiOiA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.nwwnNsk1-ZkbmnvsF6zTHm8CHERFMGQPhos-EJcaH4H
h-sMgk8ePrGhw_trPYs8KQxsn6R9Emo_wHwajyFKzuMXZFSZ3p6Mb8dkxtVyjoy2
GIzvuJT_u7PkY2t8QU9hjBcHs68PkgjDVTrG1uRTx0GxFbuPbj96tVuj11pTnmFC
UR6IEOXKYr7iGOCRB3btfJhM0_AKQUfqKnRlrRscc8Kol-cSLWoYE9l5QqholImz
jT_cMnNIznW9E7CDyWXTsO70xnB4SkG6pXfLSjLLlxmPGiyon_-Te111V8uE83Il
zCYIb_NMXvtTIVc1jpspnTSD7xMbpL-2QgwUsAlMGzw
The request_uri Authorization Request parameter enables OAuth authorization requests to be passed by reference, rather than by value. This parameter is used identically to the request parameter, other than that the Request Object value is retrieved from the resource identified by the specified URI rather than passed by value.
The entire Request URI MUST NOT exceed 512 ASCII characters. There are three reasons for this restriction.
The contents of the resource referenced by the URI MUST be a Request Object. The request_uri value MUST be either URN as defined in RFC8141 or https URI, as defined in 2.7.2 of RFC7230 . The request_uri value MUST be reachable by the Authorization Server.
The following is an example of the contents of a Request Object resource that can be referenced by a request_uri (with line wraps within values for display purposes only):
eyJhbGciOiJSUzI1NiIsImtpZCI6ImsyYmRjIn0.ew0KICJpc3MiOiAiczZCaGRSa3 F0MyIsDQogImF1ZCI6ICJodHRwczovL3NlcnZlci5leGFtcGxlLmNvbSIsDQogInJl c3BvbnNlX3R5cGUiOiAiY29kZSBpZF90b2tlbiIsDQogImNsaWVudF9pZCI6ICJzNk JoZFJrcXQzIiwNCiAicmVkaXJlY3RfdXJpIjogImh0dHBzOi8vY2xpZW50LmV4YW1w bGUub3JnL2NiIiwNCiAic2NvcGUiOiAib3BlbmlkIiwNCiAic3RhdGUiOiAiYWYwaW Zqc2xka2oiLA0KICJub25jZSI6ICJuLTBTNl9XekEyTWoiLA0KICJtYXhfYWdlIjog ODY0MDAsDQogImNsYWltcyI6IA0KICB7DQogICAidXNlcmluZm8iOiANCiAgICB7DQ ogICAgICJnaXZlbl9uYW1lIjogeyJlc3NlbnRpYWwiOiB0cnVlfSwNCiAgICAgIm5p Y2tuYW1lIjogbnVsbCwNCiAgICAgImVtYWlsIjogeyJlc3NlbnRpYWwiOiB0cnVlfS wNCiAgICAgImVtYWlsX3ZlcmlmaWVkIjogeyJlc3NlbnRpYWwiOiB0cnVlfSwNCiAg ICAgInBpY3R1cmUiOiBudWxsDQogICAgfSwNCiAgICJpZF90b2tlbiI6IA0KICAgIH sNCiAgICAgImdlbmRlciI6IG51bGwsDQogICAgICJiaXJ0aGRhdGUiOiB7ImVzc2Vu dGlhbCI6IHRydWV9LA0KICAgICAiYWNyIjogeyJ2YWx1ZXMiOiBbInVybjptYWNlOm luY29tbW9uOmlhcDpzaWx2ZXIiXX0NCiAgICB9DQogIH0NCn0.nwwnNsk1-Zkbmnvs F6zTHm8CHERFMGQPhos-EJcaH4Hh-sMgk8ePrGhw_trPYs8KQxsn6R9Emo_wHwajyF KzuMXZFSZ3p6Mb8dkxtVyjoy2GIzvuJT_u7PkY2t8QU9hjBcHs68PkgjDVTrG1uRTx 0GxFbuPbj96tVuj11pTnmFCUR6IEOXKYr7iGOCRB3btfJhM0_AKQUfqKnRlrRscc8K ol-cSLWoYE9l5QqholImzjT_cMnNIznW9E7CDyWXTsO70xnB4SkG6pXfLSjLLlxmPG iyon_-Te111V8uE83IlzCYIb_NMXvtTIVc1jpspnTSD7xMbpL-2QgwUsAlMGzw
The Client stores the Request Object resource either locally or remotely at a URI the Authorization Server can access. Such facility may be provided by the authorization server or a third party. For example, the authorization server may provide a URL to which the client POSTs the request object and obtains the Request URI. This URI is the Request Object URI, request_uri.
It is possible for the Request Object to include values that are to be revealed only to the Authorization Server. As such, the request_uri MUST have appropriate entropy for its lifetime. For the guidance, refer to 5.1.4.2.2 of [RFC6819]. It is RECOMMENDED that it be removed after a reasonable timeout unless access control measures are taken.
The following is an example of a Request Object URI value (with line wraps within values for display purposes only):
https://tfp.example.org/request.jwt#
GkurKxf5T0Y-mnPFCHqWOMiZi4VS138cQO_V7PZHAdM
The Client sends the Authorization Request to the Authorization Endpoint.
The following is an example of an Authorization Request using the request_uri parameter (with line wraps within values for display purposes only):
https://server.example.com/authorize?
response_type=code%20id_token
&client_id=s6BhdRkqt3
&request_uri=https%3A%2F%2Ftfp.example.org%2Frequest.jwt
%23GkurKxf5T0Y-mnPFCHqWOMiZi4VS138cQO_V7PZHAdM
&state=af0ifjsldkj
Upon receipt of the Request, the Authorization Server MUST send an HTTP GET request to the request_uri to retrieve the referenced Request Object, unless it is stored in a way so that it can retrieve it through other mechanism securely, and parse it to recreate the Authorization Request parameters.
The following is an example of this fetch process:
GET /request.jwt HTTP/1.1 Host: tfp.example.org
The following is an example of the fetch response:
HTTP/1.1 200 OK Date: Thu, 16 Feb 2017 23:52:39 GMT Server: Apache/2.2.22 (tfp.example.org) Content-type: application/jwt Content-Length: 1250 Last-Modified: Wed, 15 Feb 2017 23:52:32 GMT eyJhbGciOiJSUzI1NiIsImtpZCI6ImsyYmRjIn0.ew0KICJpc3MiOiAiczZCaGRSa3 F0MyIsDQogImF1ZCI6ICJodHRwczovL3NlcnZlci5leGFtcGxlLmNvbSIsDQogInJl c3BvbnNlX3R5cGUiOiAiY29kZSBpZF90b2tlbiIsDQogImNsaWVudF9pZCI6ICJzNk JoZFJrcXQzIiwNCiAicmVkaXJlY3RfdXJpIjogImh0dHBzOi8vY2xpZW50LmV4YW1w bGUub3JnL2NiIiwNCiAic2NvcGUiOiAib3BlbmlkIiwNCiAic3RhdGUiOiAiYWYwaW Zqc2xka2oiLA0KICJub25jZSI6ICJuLTBTNl9XekEyTWoiLA0KICJtYXhfYWdlIjog ODY0MDAsDQogImNsYWltcyI6IA0KICB7DQogICAidXNlcmluZm8iOiANCiAgICB7DQ ogICAgICJnaXZlbl9uYW1lIjogeyJlc3NlbnRpYWwiOiB0cnVlfSwNCiAgICAgIm5p Y2tuYW1lIjogbnVsbCwNCiAgICAgImVtYWlsIjogeyJlc3NlbnRpYWwiOiB0cnVlfS wNCiAgICAgImVtYWlsX3ZlcmlmaWVkIjogeyJlc3NlbnRpYWwiOiB0cnVlfSwNCiAg ICAgInBpY3R1cmUiOiBudWxsDQogICAgfSwNCiAgICJpZF90b2tlbiI6IA0KICAgIH sNCiAgICAgImdlbmRlciI6IG51bGwsDQogICAgICJiaXJ0aGRhdGUiOiB7ImVzc2Vu dGlhbCI6IHRydWV9LA0KICAgICAiYWNyIjogeyJ2YWx1ZXMiOiBbInVybjptYWNlOm luY29tbW9uOmlhcDpzaWx2ZXIiXX0NCiAgICB9DQogIH0NCn0.nwwnNsk1-Zkbmnvs F6zTHm8CHERFMGQPhos-EJcaH4Hh-sMgk8ePrGhw_trPYs8KQxsn6R9Emo_wHwajyF KzuMXZFSZ3p6Mb8dkxtVyjoy2GIzvuJT_u7PkY2t8QU9hjBcHs68PkgjDVTrG1uRTx 0GxFbuPbj96tVuj11pTnmFCUR6IEOXKYr7iGOCRB3btfJhM0_AKQUfqKnRlrRscc8K ol-cSLWoYE9l5QqholImzjT_cMnNIznW9E7CDyWXTsO70xnB4SkG6pXfLSjLLlxmPG iyon_-Te111V8uE83IlzCYIb_NMXvtTIVc1jpspnTSD7xMbpL-2QgwUsAlMGzw
If the request object is encrypted, the Authorization Server MUST decrypt the JWT in accordance with the JSON Web Encryption specification.
The result is a signed request object.
If decryption fails, the Authorization Server MUST return an invalid_request_object error.
The Authorization Server MUST perform the signature validation of the JSON Web Signature signed request object. For this, the alg Header Parameter in its JOSE Header MUST match the value of the pre-registered algorithm. The signature MUST be validated against the appropriate key for that client_id and algorithm.
If signature validation fails, the Authorization Server MUST return an invalid_request_object error.
The Authorization Server MUST extract the set of Authorization Request parameters from the Request Object value. The Authorization Server MUST only use the parameters in the Request Object even if the same parameter is provided in the query parameter. The Authorization Server then validates the request as specified in OAuth 2.0.
If the validation fails, then the Authorization Server MUST return an error as specified in OAuth 2.0.
Authorization Server Response is created and sent to the client as in Section 4 of OAuth 2.0 .
In addition, this document uses these additional error values:
Client implementations supporting the Request Object URI method MUST support TLS following Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS).
To protect against information disclosure and tampering, confidentiality protection MUST be applied using TLS with a cipher suite that provides confidentiality and integrity protection.
HTTP clients MUST also verify the TLS server certificate, using subjectAltName dNSName identities as described in [RFC6125], to avoid man-in-the-middle attacks. The rules and guidelines defined in [RFC6125] apply here, with the following considerations:
This specification requests no actions by IANA.
In addition to the all the security considerations discussed in OAuth 2.0, the security considerations in [RFC7515], [RFC7516], and [RFC7518] needs to be considered. Also, there are several academic papers such as [BASIN] that provide useful insight into the security properties of protocols like OAuth.
In consideration of the above, this document advises taking the following security considerations into account.
When sending the authorization request object through request parameter, it MUST either be signed using JWS or encrypted using JWE with then considered appropriate algorithm.
The source of the Authorization Request MUST always be verified. There are several ways to do it in this specification.
Although this specification does not require them, research such as [BASIN] points out that it is a good practice to explicitly state the intended interaction endpoints and the message position in the sequence in a tamper evident manner so that the intent of the initiator is unambiguous. The endpoints that come into question in this specification are :
Further, if dynamic discovery is used, then the discovery related endpoints also come into question.
In [RFC6749], while Redirection URI is included, others are not included in the Authorization Request. As the result, the same applies to Authorization Request Object.
The lack of the link among those endpoints are cited as the cause of Cross-Phase Attacks introduced in [FETT]. An extension specification should be created as a measure to address the risk.
The introduction of request_uri introduces several attack possibilities.
A set of malicious client can launch a DoS attack to the authorization server by pointing the request_uri to a uri that returns extremely large content or extremely slow to respond. Under such an attack, the server may use up its resource and start failing.
Similarly, a malicious client can specify the request_uri value that itself points to an authorization request URI that uses request_uri to cause the recursive lookup.
To prevent such attack to succeed, the server should (a) check that the value of request_uri parameter does not point to an unexpected location, (b) check the content type of the response is application/jwt (c) implement a time-out for obtaining the content of request_uri, and (d) do not perform recursive GET on the request_uri.
The value of request_uri is not signed thus it can be tampered by Man-in-the-browser attacker. Several attack possibilities rise because of this, e.g., (a) attacker may create another file that the rewritten URI points to making it possible to request extra scope (b) attacker launches a DoS attack to a victim site by setting the value of request_uri to be that of the victim.
To prevent such attack to succeed, the server should (a) check that the value of request_uri parameter does not point to an unexpected location, (b) check the content type of the response is application/jwt (c) implement a time-out for obtaining the content of request_uri.
Current security considerations can be found in Recommendations for Secure Use of TLS and DTLS. This supersedes the TLS version recommendations in OAuth 2.0.
When the Client is being granted access to a protected resource containing personal data, both the Client and the Authorization Server need to adhere to Privacy Principles. RFC 6973 Privacy Considerations for Internet Protocols gives excellent guidance on the enhancement of protocol design and implementation. The provision listed in it should be followed.
Most of the provision would apply to The OAuth 2.0 Authorization Framework and The OAuth 2.0 Authorization Framework: Bearer Token Usage and are not specific to this specification. In what follows, only the specific provisions to this specification are noted.
When the Client is being granted access to a protected resource containing personal data, the Client SHOULD limit the collection of personal data to that which is within the bounds of applicable law and strictly necessary for the specified purpose(s).
It is often hard for the user to find out if the personal data asked for is strictly necessary. A Trust Framework Provider can help the user by examining the Client request and comparing to the proposed processing by the Client and certifying the request. After the certification, the Client, when making an Authorization Request, can submit Authorization Request to the Trust Framework Provider to obtain the Request Object URI.
Upon receiving such Request Object URI in the Authorization Request, the Authorization Server first verifies that the authority portion of the Request Object URI is a legitimate one for the Trust Framework Provider. Then, the Authorization Server issues HTTP GET request to the Request Object URI. Upon connecting, the Authorization Server MUST verify the server identity represented in the TLS certificate is legitimate for the Request Object URI. Then, the Authorization Server can obtain the Request Object, which includes the client_id representing the Client.
The Consent screen MUST indicate the Client and SHOULD indicate that the request has been vetted by the Trust Framework Operator for the adherence to the Collection Limitation principle.
This specification allows extension parameters. These may include potentially sensitive information. Since URI query parameter may leak through various means but most notably through referrer and browser history, if the authorization request contains a potentially sensitive parameter, the Client SHOULD JWE encrypt the request object.
Where Request Object URI method is being used, if the request object contains personally identifiable or sensitive information, the request_uri SHOULD be used only once, have a short validity period, and MUST have large enough entropy deemed necessary with applicable security policy unless the Request Object itself is JWE Encrypted. The adequate shortness of the validity and the entropy of the Request Object URI depends on the risk calculation based on the value of the resource being protected. A general guidance for the validity time would be less than a minute and the Request Object URI is to include a cryptographic random value of 128bit or more at the time of the writing of this specification.
Even if the protected resource does not include a personally identifiable information, it is sometimes possible to identify the user through the Request Object URI if persistent per-user Request Object URI is used. A third party may observe it through browser history etc. and start correlating the user's activity using it. In a way, it is a data disclosure as well and should be avoided.
Therefore, per-user Request Object URI should be avoided.
The following people contributed to the creation of this document in the OAuth WG. (Affiliations at the time of the contribution are used.)
Sergey Beryozkin, Brian Campbell (Ping Identity), Vladimir Dzhuvinov (Connect2id), Michael B. Jones (Microsoft), Torsten Lodderstedt (YES) Jim Manico, Axel Nenker(Deutsche Telecom), Hannes Tschofenig (ARM), Ben Campbell, Kathleen Moriarty (as AD), and Steve Kent (as SECDIR).
The following people contributed to creating this document through the OpenID Connect Core 1.0.
Brian Campbell (Ping Identity), George Fletcher (AOL), Ryo Itou (Mixi), Edmund Jay (Illumila), Michael B. Jones (Microsoft), Breno de Medeiros (Google), Hideki Nara (TACT), Justin Richer (MITRE).
In addition, the following people contributed to this and previous versions through the OAuth Working Group.
Dirk Balfanz (Google), James H. Manger (Telstra), John Panzer (Google), David Recordon (Facebook), Marius Scurtescu (Google), Luke Shepard (Facebook).
Note to the RFC Editor: Please remove this section from the final RFC.
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| [BASIN] | Basin, D., Cremers, C. and S. Meier, "Provably Repairing the ISO/IEC 9798 Standard for Entity Authentication", Journal of Computer Security - Security and Trust Principles Volume 21 Issue 6, Pages 817-846, November 2013. |
| [FETT] | Fett, D., Kusters, R. and G. Schmitz, "A Comprehensive Formal Security Analysis of OAuth 2.0", CCS '16 Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security Pages 1204-1215 , October 2016. |
| [OpenID.Core] | Sakimura, N., Bradley, J., Jones, M., de Medeiros, B. and C. Mortimore, "OpenID Connect Core 1.0", OpenID Foundation Standards, February 2014. |
| [RFC6819] | Lodderstedt, T., McGloin, M. and P. Hunt, "OAuth 2.0 Threat Model and Security Considerations", RFC 6819, DOI 10.17487/RFC6819, January 2013. |
| [RFC6973] | Cooper, A., Tschofenig, H., Aboba, B., Peterson, J., Morris, J., Hansen, M. and R. Smith, "Privacy Considerations for Internet Protocols", RFC 6973, DOI 10.17487/RFC6973, July 2013. |