OpenID Provider Authentication Policy Extension 1.0

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 .

Throughout this document, values are quoted to indicate that they are to be taken literally. When using these values in protocol messages, the quotes MUST NOT be used as part of the value. All OpenID 2.0 messages that contain a Provider Authentication Policy Extension (PAPE) element MUST contain the following extension namespace declaration, as specified in the Extensions section of .

=http://specs.openid.net/extensions/pape/1.0]]> The actual extension namespace alias should be determined on a per-message basis by the party composing the messages, in such a manner as to avoid conflicts between multiple extensions. For the purposes of this document and when constructing OpenID 1.1 messages, the extension namespace alias SHALL be "pape". Additionally, this specification uses name spaces for the custom authentication level identification. It is in the form of

=http://some.authlevel.uri]]> The actual extension namespace alias should be determined on a per-message basis by the party composing the messages, in such a manner as to avoid conflicts between multiple extensions. For the purposes of this document and when constructing OpenID 1.1 messages, the one custom authentication level identification extension namespace defined by this specification is "nist". Others may also be defined and used by implementations, for example, "jisa".

The following terms are defined in : Identifier OpenID Provider (OP) Relying Party (RP) User-Agent An Authentication Method is a single mechanism by which the End User authenticated to their OpenID Provider, for example, a password or a hardware credential. An Authentication Policy is a plain-text description of requirements that dictate which Authentication Methods can be used by an End User when authenticating to their OpenID Provider. An Authentication Policy is defined by a URI which must be previously agreed upon by one or more OPs and RPs.

As part of the Discovery process, OpenID Providers can optionally add supported authentication policies to an End User's XRDS document. This aids Relying Parties in choosing between multiple listed OPs depending on authentication policy requirements. The Relying Party includes parameters in the OpenID Authentication request describing its preferences for authentication policy for the current assertion. The OpenID Provider processes the PAPE request, prompting the End User to fulfill the requested policies during the authentication process. As part of the OpenID Provider's response to the Relying Party, the OP includes PAPE information around the End User's authentication. An OP MAY include this response information even if not requested by the RP. When processing the OpenID Provider's response, the Relying Party takes the PAPE information into account when determining if the End User should be sent through additional verification steps or if the OpenID login process cannot proceed due to not meeting policy requirements.

Via the use of within OpenID, Relying Parties are able to discover OpenID Provider service information in an automated fashion. This is used within OpenID Authentication for a RP to discover what version of the protocol each OP listed supports as well as any extensions, such as this one, that are supported. To aide in the process of a Relying Party selecting which OP they wish to interact with, it is STRONGLY RECOMMENDED that the following information be added to the End User's XRDS document. An OP may choose to advertise both custom levels and supported polices in the same <xrd:Service>. An OP should only advertise the authentication policies and custom assurance level namespaces that it supports. When advertising supported policies, each policy URI MUST be added as the value of an <xrd:Type> element of an OpenID <xrd:Service> element in an XRDS document.

Example: http://specs.openid.net/auth/2.0/signon http://schemas.openid.net/pape/policies/2007/06/phishing-resistant https://example.com/server ]]> When advertising supported custom Assurance Level name spaces, each name space URI MUST be added as the value of an <xrd:Type> element of an OpenID <xrd:Service> element in an XRDS document.

Example: http://specs.openid.net/auth/2.0/signon http://csrc.nist.gov/publications/nistpubs/800-63/SP800-63V1_0_2.pdf https://example.com/server ]]>

The following are defined policies and policy identifiers describing how the End User may authenticate to an OP. Additional policies can be specified elsewhere and used without making changes to this document. The policies described below are designed to be a starting point to cover the most common use-cases. Additional polices can be found at http://schemas.openid.net/pape/policies/. When multiple policies are listed in the Relying Party's request, the OpenID Provider SHOULD satisfy as many of the requested policies as possible. This may require, for instance, that a user who has already been authenticated using one authentication method be re-authenticated with different or additional methods that satisfy the request made by the Relying Party. It is always the responsibility of the RP to determine whether the particular authentication performed by the OP satisfied its requirements; this determination may involve information contained in the PAPE response, specific knowledge that the RP has about the OP, and additional information that it may possess or obtain about the particular authentication performed. Phishing-Resistant Authentication

http://schemas.openid.net/pape/policies/2007/06/phishing-resistant An authentication mechanism where a party potentially under the control of the Relying Party can not gain sufficient information to be able to successfully authenticate to the End User's OpenID Provider as if that party were the End User. (Note that the potentially malicious Relying Party controls where the User-Agent is redirected to and thus may not send it to the End User's actual OpenID Provider). Multi-Factor Authentication

http://schemas.openid.net/pape/policies/2007/06/multi-factor An authentication mechanism where the End User authenticates to the OpenID Provider by providing more than one authentication factor. Common authentication factors are something you know, something you have, and something you are. An example would be authentication using a password and a software token or digital certificate. Physical Multi-Factor Authentication

http://schemas.openid.net/pape/policies/2007/06/multi-factor-physical An authentication mechanism where the End User authenticates to the OpenID Provider by providing more than one authentication factor where at least one of the factors is a physical factor such as a hardware device or biometric. Common authentication factors are something you know, something you have, and something you are. This policy also implies the Multi-Factor Authentication policy (http://schemas.openid.net/pape/policies/2007/06/multi-factor) and both policies MAY BE specified in conjunction without conflict. An example would be authentication using a password and a hardware token. Of the policies defined above, two are not independent. All authentications satisfying the Multi-Factor Physical policy also satisfy the Multi-Factor policy. Therefore, whenever the OP returns a result saying that Multi-Factor Physical authentication was performed it MUST also indicate that Multi-Factor authentication was performed.

Custom Assurance Levels are optional. The namespaces may be defined by various parties, such as country or industry specific standards bodies, or other groups or individuals. The namespace URI should be chosen with care to be unambiguous when used as a <xrd:Type> element to advertise the namespaces supported by the OP. The custom Assurance Level namespace should define the meaning of the strings that are returned by the OP in the openid.pape.auth_level.<cust> element.

The following parameters MUST be included during an OpenID Authentication request by the Relying Party that uses this extension unless marked as optional. openid.ns.pape Value:

http://specs.openid.net/extensions/pape/1.0 openid.pape.max_auth_age (Optional) If the End User has not actively authenticated to the OP within the number of seconds specified in a manner fitting the requested policies, the OP SHOULD authenticate the End User for this request using the requested policies. The OP MUST actively authenticate the user and not rely on a browser cookie from a previous authentication. Value: Integer value greater than or equal to zero in seconds. If an OP does not satisfy a request for timely authentication, the RP may decide not to grant the End User access to the services provided by the RP. If this parameter is absent from the request, the OP should authenticate the user at its own discretion. openid.pape.preferred_auth_policies Zero or more authentication policy URIs representing authentication policies that the OP SHOULD satisfy when authenticating the user. If multiple policies are requested, the OP SHOULD satisfy as many of them as it can. Value: Space separated list of authentication policy URIs. If no policies are requested, the RP may be interested in other information such as the authentication age.

Example: openid.pape.preferred_auth_policies= http://schemas.openid.net/pape/policies/2007/06/phishing-resistant http://schemas.openid.net/pape/policies/2007/06/multi-factor openid.pape.auth_level.ns.<cust> (Optional) The name space for the custom Assurance Level. Assurance levels and their name spaces are defined by various parties, such as country or industry specific standards bodies, or other groups or individuals. Value: URL that represents this Assurance Level.

Example: openid.pape.auth_level.ns.nist= http://csrc.nist.gov/publications/nistpubs/800-63/SP800-63V1_0_2.pdf openid.pape.auth_level.ns.jisa= http://www.jisa.or.jp/spec/auth_level.html openid.pape.preferred_auth_level_types (Optional) The space separated list of the name spaces of the custom Assurance Level that RP requests, in the order of its preference. Value: The space separated list of the name space aliases of the custom Assurance Level that RP requests, in the order of its preference.

Example: openid.pape.preferred_auth_levels=jisa nist

In response to a Relying Party's request, the following parameters MUST be included in the OpenID Authentication Response. All response parameters MUST be included in the signature of the Authentication Response. It is RECOMMENDED that an OP supporting this extension include the following parameters even if not requested by the Relying Party. All response parameters MUST describe the End User's current session with the OpenID Provider. openid.ns.pape Value:

http://specs.openid.net/extensions/pape/1.0 openid.pape.auth_policies One or more authentication policy URIs representing policies that the OP satisfied when authenticating the End User. Value: Space separated list of authentication policy URIs. Note: If no policies were met though the OP wishes to convey other information in the response, this parameter MUST be included with the value of http://schemas.openid.net/pape/policies/2007/06/none.

Example: openid.pape.auth_policies= http://schemas.openid.net/pape/policies/2007/06/multi-factor http://schemas.openid.net/pape/policies/2007/06/multi-factor-physical openid.pape.auth_time (Optional) The most recent timestamp when the End User has actively authenticated to the OP in a manner fitting the asserted policies. Value: The timestamp MUST be formatted as specified in section 5.6 of , with the following restrictions: All times must be in the UTC time zone, indicated with a "Z". No fractional seconds are allowed

Example: 2005-05-15T17:11:51Z Note: If the RP's request included the "openid.pape.max_auth_age" parameter then the OP MUST include "openid.pape.auth_time" in its response. If "openid.pape.max_auth_age" was not requested, the OP MAY choose to include "openid.pape.auth_time" in its response. openid.pape.auth_level.ns.<cust> (Optional) The name space for the custom Assurance Level defined by various parties, such as a country or industry specific standards body, or other groups or individuals. Value: URL that represents this Assurance Level.

Example: openid.pape.auth_level.ns.nist= http://csrc.nist.gov/publications/nistpubs/800-63/SP800-63V1_0_2.pdf openid.pape.auth_level.ns.jisa= http://www.jisa.or.jp/spec/auth_level.html openid.pape.auth_level.<cust> (Optional) The Assurance Level as defined by the above standards body, group, or individual that corresponds to the authentication method and policies employed by the OP when authenticating the End User. Value: Strings defined according to this Assurance Level.

Example: openid.pape.auth_level.nist=1 openid.pape.auth_level.jisa=2

Per commonly accepted security practices, it should be noted that the overall strength of any authentication is only as strong as its weakest step. It is thus recommended that provisioning of phishing-resistant and other credentials stronger than shared secrets should be accomplished using methods that are at least as strong as the credential being provisioned. By counter-example, allowing people to retrieve a phishing-resistant credential using only a phishable shared secret negates much of the value provided by the phishing-resistant credential itself. Similarly, sometimes using a phishing-resistant method when a phishable method continues to also sometimes be employed may still enable phishing attacks to compromise the OpenID. OPs SHOULD attempt to satisfy the authentication policies requested by the RP and the reply SHOULD minimally contain at least the subset of the requested policies that the authentication performed satisfied. The OP MAY also choose to return additional policies that the authentication performed satisfied, even if not requested. If the RP requested that an authentication level or levels be returned and the OP supports some or all of those level types, then the OP SHOULD return the actual level value for each of the supported types requested, if available.

National Institute of Standards and Technology (NIST) in Special Publication 800-63 defines a set of Assurance Levels from 1 to 4. These may be returned by the OP to the RP to communicate which NIST level the identity proofing, authentication method, and policies employed by the OP when authenticating the End User corresponds to. Value: Integer value between 0 and 4 inclusive. Note: Level 0 is not an assurance level defined by NIST, but rather SHOULD be used to signify that the OP recognizes the parameter and the End User authentication did not meet the requirements of Level 1. See for high-level example classifications of authentication methods within the defined levels. Authentication using a long-lived browser cookie, for instance, is one example where the use of "level 0" is appropriate. Authentications with level 0 should never be used to authorize access to any resource of any monetary value whatsoever. The previous sentence should not be construed as implying that any of the other levels are recommended or appropriate for accessing resources with monetary value either without the Relying Party doing an appropriate risk assessment of the particular OpenID provider asserting them and their issuance and authentication procedures as they apply to the particular online interaction in question. Depending on the particular use case being satisfied by the authentication response and PAPE information, the OpenID Provider will have to make a decision, ideally with the consent of the End User, as if it will include the "openid.pape.auth_level.nist" parameter. This information is designed to give Relying Parties more information around the strength of credentials used without actually disclosing the specific credential type. Disclosing the specific credential type can be considered a potential privacy or security risk. It is RECOMMENDED that this parameter always be included in the response from the OP. This holds true even in cases where the End User authentication does not meet one of the defined Authentication Policies. For example, if the End User is authenticating using a password via HTTPS there is still value to the RP in knowing if the strength of the Password corresponds to the entropy requirements laid out by Level 1 or 2 or that it does not even meet the minimum requirement for the lowest level. With that said, discretion needs to be used by OP's as conveying that one of their End User's has a weak password to an "un-trustworthy" RP would not generally be considered a good idea.

This non-normative section illustrates classification of various common authentication methods and their respective conformance within the defined policies and levels. This table provides examples of common authentication technologies and their mapping to the Authentication Policies defined in . Method Phishing-Resistant Multi-Factor Physical Multi-Factor Password via HTTPS Visual secret via HTTPS PIN and digital certificate via HTTPS X X PIN and "soft" OTP token via HTTPS X PIN and "hard" OTP token via HTTPS X X PIN and "hard" crypto token via HTTPS X X X Information Card via HTTPS X X This section is designed to highlight the Authentication Mechanism Levels described in . All normative and authoritative text can be found in . Note that assurance level is not only comprised of Authentication Mechanism employed but also the nature of the identity proofing performed. The overall assurance level is determined as a combination of these factors. This table is republished from page 39 of . Token Type Level 1 Level 2 Level 3 Level 4 Hard crypto token X X X X One-time password device X X X Soft crypto token X X X Passwords & PINs X X This table is republished from page 39 of . Protect Against Level 1 Level 2 Level 3 Level 4 On-line guessing X X X X Replay X X X X Eavesdropper X X X Verifier impersonation X X Man-in-the-middle X X Session hijacking X The following table illustrates the minimum number of factors required at each Authentication Mechanism Level. Level Factors 1 1 2 1 3 2 4 2 In all cases, implementing a commonly accepted nonce and cross-site scripting protection when entering authentication credentials is required to satisfy all four Authentication Mechanism Levels. All examples below assume this requirement is met. It should be noted that NIST Authentication Mechanism Levels 1 and 2 have differing password entropy requirements. When working with passwords, you should refer to the specification for more details. All examples below assume the password meets these requirements. This table provides examples of common authentication technologies and their mapping to NIST Authentication Mechanism Levels, please be aware that there are details not represented in these examples that may bear on the resulting Authentication Mechanism Level. Method Level 1 Level 2 Level 3 Level 4 Password via HTTP Yes, if challenge-response Password via HTTPS Yes Yes PIN and Digital Certificate via HTTPS Yes Yes Yes PIN and "soft" OTP token via HTTPS Yes Yes Yes PIN and "hard" OTP token via HTTPS Yes Yes Yes PIN and "hard" crypto token via HTTPS Yes Yes Yes Yes, if FIPS 140-2 Level 2 crypto and Level 3 physical The authors would like to thank John Bradley, Kim Cameron, Barry Ferg, George Fletcher, Dick Hardt, Nate Klingstein, Gary Krall, Ben Laurie, Arun Nanda, Drummond Reed, Tatsuki Sakushima, and Allen Tom for their feedback when drafting this specification. David Recordon would also like to acknowledge VeriSign who employed him during the original authoring of this specification.