The OAuth 2.0 Authorization Framework: JWT Secured Authorization Request (JAR)Nomura Research InstituteOtemachi Financial City Grand Cube, 1-9-2 OtemachiChiyoda-ku100-0004TokyoJapan+81-3-5533-2111n-sakimura@nri.co.jphttp://nat.sakimura.org/YubicoCasilla 177, Sucursal TalaganteTalaganteRMChile+1.202.630.5272ve7jtb@ve7jtb.comhttp://www.thread-safe.com/
Security
OAuth Working GroupRFCRequest for CommentsI-DInternet-DraftAssertionClaimSecurity TokenOAuthJavaScript Object NotationJSONJSON Web TokenJWTJSON Web SignatureJWSJSON Web EncryptionJWEThe 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.
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:
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 has
shortcomings in that:
the communication through the user agents are
not integrity protected and thus the parameters can be tainted
(integrity protection failure)the source of the communication is not authenticated
(source authentication failure)the communication through the user agents can be monitored
(containment / confidentiality failure).
Due to these inherent weaknesses, several attacks against the protocol,
such as Redirection URI rewriting and Mix-up attack
, 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 its close relationship with JSON,
which is used as OAuth's response format its developer friendliness due to its textual natureits relative compactness compared to XML its development status that it is an RFC and so is its associated
signing and encryption methods as
and the relative ease of JWS and JWE compared to XML Signature and Encryption. 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:(integrity protection)
The request can be signed so that the integrity of the request can be checked.(source authentication)
The request can be signed so that the signer can be authenticated.(confidentiality protection)
The request can be encrypted so that end-to-end
confidentiality can be provided even if the TLS connection is
terminated at one point or another. (collection minimization)
The request can be signed by a third party attesting that
the authorization request is compliant with a certain policy.
For example, a request can be pre-examined by a third party
that all the personal data requested is strictly necessary
to perform the process that the end-user asked for, and
statically signed by that third party.
The authorization server then examines the signature
and shows the conformance status to the end-user,
who would have some assurance as to
the legitimacy of the request when authorizing it.
In some cases, it may even be desirable to skip the authorization
dialogue under such circumstances.
There are a few cases that request by reference is useful such
as:When it is desirable to reduce the size of transmitted request.
The use of application layer security increases
the size of the request, particularly when public key
cryptography is used. When the client does not want to do the crypto.
The Authorization Server may provide an endpoint to
accept the Authorization Request through direct communication
with the Client so that the Client is authenticated
and the channel is TLS protected. This capability is in use by OpenID Connect .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 SetAbsolute URI from which the Request
Object can be obtained
The following abbreviations are common to this specification.
Javascript Object NotationJSON Web TokenJSON Web SignatureJSON Web EncryptionUniform Resource IdentifierUniform Resource LocatorWireless Application ProtocolA 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 it is a JWT, JSON strings MUST be represented in UTF-8.
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.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 .
The result is a Nested JWT, as defined in
.
The Authorization Request Object MAY be sent by value as
described in
or by reference as described in .request and
request_uri parameters
MUST NOT be included in Request Objects.
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 Request Object that
holds authorization request parameters stated in section 4 of
OAuth 2.0. The absolute URI as defined by RFC3986 that points to the Request Object that holds authorization request
parameters stated in section 4 of OAuth
2.0.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:The authorization request object MUST be one of the following: JWS signed JWS signed and JWE encryptedThe 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 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.
Many WAP / feature phones do not accept large payloads.
The restriction is typically either 512 or 1024 ASCII characters.The maximum URL length supported by older versions of
Internet Explorer is 2083 ASCII characters. On a slow connection such as 2G mobile connection,
a large URL would cause the slow response and therefore the use of such
is not advisable from the user experience point of view.
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 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 Requiest 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.
It is RECOMMENDED that it be removed
after a reasonable timeout
unless access control measures are taken.
The Client sends the Authorization Request to the
Authorization Endpoint.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.
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 and the
signature validation MUST be performed
as defined in as well.
If decryption fails,
the Authorization Server MUST return an
invalid_request_object error.
To perform signature validation of a
JSON Web Signature signed request
object, 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:
The request_uri in the
Authorization Request returns an error or contains invalid data.The request parameter contains
an invalid Request Object.
The Authorization Server does not support
the use of the request parameter.
The Authorization Server does not support the use of
the request_uri parameter.
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
, to avoid man-in-the-middle attacks.
The rules and guidelines defined in
apply here, with the following considerations:
Support for DNS-ID identifier type (that is, the dNSName identity
in the subjectAltName extension) is REQUIRED. Certification
authorities which issue server certificates MUST support
the DNS-ID identifier type, and the DNS-ID identifier type MUST
be present in server certificates.
DNS names in server certificates MAY contain the
wildcard character "*".
Clients MUST NOT use CN-ID
identifiers; a CN field may be present in the server
certificate's
subject name, but MUST NOT be used for authentication within the
rules described in .
SRV-ID and URI-ID as described in Section 6.5 of
MUST NOT be used for comparison.
This specification requests no actions by IANA.
In addition to the all
the security considerations discussed in OAuth 2.0,
the security considerations in
,
, and
needs to be considered.
Also, there are several academic papers such as
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.
Verifying the JWS Signature of the Request Object.Verifying that the symmetric key for the JWE encryption is the correct one
if the JWE is using symmetric encryption.Verifying the TLS Server Identity of the Request Object URI.
In this case, the Authorization Server MUST know
out-of-band that the Client uses Request Object URI and
only the Client is covered by the TLS certificate.
In general, it is not a reliable method.
Authorization Server is providing an endpoint
that provides a Request Object URI in exchange for
a Request Object. In this case, the Authorization
Server MUST perform Client Authentication to accept
the Request Object and bind the Client Identifier
to the Request Object URI it is providing.
Since Request Object URI can be replayed, the lifetime
of the Request Object URI MUST be short and preferably
one-time use. The entropy of the Request Object URI
MUST be sufficiently large.
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.
A third party, such as a Trust Framework Provider,
provides an endpoint
that provides a Request Object URI in exchange for
a Request Object. The same requirements as (b) above
apply. In addition, the Authorization Server
MUST know out-of-band that the Client utilizes
the Trust Framework Operator.
Although this specification does not require them,
research such as 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 :
Protected Resources (protected_resources)Authorization Endpoint (authorization_endpoint)Redirection URI (redirect_uri)Token Endpoint (token_endpoint)
Further, if dynamic discovery is used, then the discovery
related endpoints also come into question.
In ,
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 sited as the
cause of Cross-Phase Attacks introduced in .
An extension specification should be created
as a measure to address the risk.
The introdcution of redirect_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/jose
(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/json
(c) implement a time-out for obtaining the content of
request_uri.
Curent 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),
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).-15Removed further duplication-14#71 Reiterate dynamic params are included. #70 Made clear that AS must return error.#69 Inconsistency of the need to sign.Fixed Mimetype. #67 Incosistence in requiring HTTPS in request uri.#66 Dropped ISO 29100 reference.#25 Removed Encrypt only option.#59 Same with #25.-13add TLS Security Consideration sectionreplace RFC7525 reference with BCP195moved front tag in FETT reference to fix XML structurechanges reference from SoK to FETT-12fixes #62 - Alexey Melnikov Discuss fixes #48 - OPSDIR Review : General - delete semicolors after list itemsfixes #58 - DP Comments for the Last Callfixes #57 - GENART - Remove "non-normative ... " from examples.fixes #45 - OPSDIR Review : Introduction - are attacks discovered or already openedfixes #49 - OPSDIR Review : Introduction - Inconsistent colons after initial sentence of list items.fixes #53 - OPSDIR Review : 6.2 JWS Signed Request Object - Clarify JOSE Headerfixes #42 - OPSDIR Review : Introduction - readability of 'and' is confusingfixes #50 - OPSDIR Review : Section 4 Request Object - Clarify 'signed, encrypted, or signed and encrypted'fixes #39 - OPSDIR Review : Abstract - Explain/Clarify JWS and JWEfixed #50 - OPSDIR Review : Section 4 Request Object - Clarify 'signed, encrypted, or signed and encrypted'fixes #43 - OPSDIR Review : Introduction - 'properties' sounds awkward and are not exactly 'properties'fixes #56 - OPSDIR Review : 12 Acknowledgements - 'contribution is' => 'contribution are'fixes #55 - OPSDIR Review : 11.2.2 Privacy Considerations - ' It is in a way' => 'In a way, it is'fixes #54 - OPSDIR Review : 11 Privacy Considerations - 'and not specific' => 'and are not specific'fixes #51 - OPSDIR Review : Section 4 Request Object - 'It is fine' => 'It is recommended'fixes #47 - OPSDIR Review : Introduction - 'over- the- wire' => 'over-the-wire'fixes #46 - OPSDIR Review : Introduction - 'It allows' => 'The use of application security' forfixes #44 - OPSDIR Review : Introduction - 'has' => 'have'fixes #41 - OPSDIR Review : Introduction - missing 'is' before 'typically sent'fixes #38 - OPSDIR Review : Section 11 - Delete 'freely accessible' regarding ISO 29100-11s/bing/being/Added history for -10-10#20: KM1 -- some wording that is awkward in the TLS section.
#21: KM2 - the additional attacks against OAuth 2.0 should
also have a pointer
#22: KM3 -- Nit: in the first line of 10.4:
#23: KM4 -- Mention RFC6973 in Section 11 in addition
to ISO 29100
#24: SECDIR review: Section 4 -- Confusing requirements
for sign+encrypt
#25: SECDIR review: Section 6 -- authentication and integrity
need not be provided if the requestor encrypts the token?
#26: SECDIR Review: Section 10 -- why no reference for
JWS algorithms?
#27: SECDIR Review: Section 10.2 - how to do the agreement
between client and server "a priori"?
#28: SECDIR Review: Section 10.3 - Indication on "large entropy"
and "short lifetime" should be indicated
#29: SECDIR Review: Section 10.3 - Typo
#30: SECDIR Review: Section 10.4 - typos and missing articles#31: SECDIR Review: Section 10.4 - Clearer statement
on the lack of endpoint identifiers needed#32: SECDIR Review: Section 11 - ISO29100 needs
to be moved to normative reference#33: SECDIR Review: Section 11 - Better English and Entropy
language needed#34: Section 4: Typo#35: More Acknowledgment#36: DP - More precise qualification on Encryption needed.-09Minor Editorial Nits. Section 10.4 added.Explicit reference to Security consideration (10.2) added in
section 5 and section 5.2., (add yourself) removed from the acknowledgment. -08Applied changes proposed by Hannes on 2016-06-29 on IETF OAuth
list recorded as https://bitbucket.org/Nat/oauth-jwsreq/issues/12/. TLS requirements added.Security Consideration reinforced.Privacy Consideration added.Introduction improved. -07Changed the abbrev to OAuth JAR from oauth-jar. Clarified sig and enc methods. Better English.Removed claims from one of the example. Re-worded the URI construction.Changed the example to use request instead of request_uri.Clarified that Request Object parameters take precedence
regardless of request or request_uri parameters were used. Generalized the language in 4.2.1 to convey the intent
more clearly.Changed "Server" to "Authorization Server" as a clarification.Stopped talking about request_object_signing_alg.IANA considerations now reflect the current status.Added Brian Campbell to the contributors list.
Made the lists alphabetic order based on the last names.
Clarified that the affiliation is at the time of the contribution.Added "older versions of " to the reference to IE uri length
limitations.Stopped talking about signed or unsigned JWS etc.1.Introduction improved.-06Added explanation on the 512 chars URL restriction. Updated Acknowledgements. -05More alignment with OpenID Connect. -04Fixed typos in examples. (request_url -> request_uri, cliend_id -> client_id) Aligned the error messages with the OAuth IANA registry.Added another rationale for having request object.-03Fixed the non-normative description about the advantage of static signature. Changed the requirement for the parameter values in the request itself and the request object from 'MUST MATCH" to 'Req Obj takes precedence.-02Now that they are RFCs, replaced JWS, JWE, etc. with RFC numbers. -01Copy Edits.Recommendations for Secure Use of Transport Layer Security (TLS) and
Datagram Transport Layer Security (DTLS)Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) are
widely used to protect data exchanged over application protocols such as HTTP,
SMTP, IMAP, POP, SIP, and XMPP. Over the last few years, several serious
attacks on TLS have emerged, including attacks on its most commonly used cipher
suites and their modes of operation. This document provides recommendations for
improving the security of deployed services that use TLS and DTLS. The
recommendations are applicable to the majority of use cases.OpenID Connect Core 1.0Nomura Research Institute, Ltd.Ping IdentityMicrosoftGoogleSalesforceProvably Repairing the ISO/IEC 9798 Standard for Entity AuthenticationA Comprehensive Formal Security Analysis of OAuth 2.0