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Network Working Group                                      H. Tschofenig
Internet-Draft                                    Nokia Siemens Networks
Intended status: Informational                                 S. Turner
Expires: January 16, 2013                                     IECA, Inc.
                                                              S. Farrell
                                                  Trinity College Dublin
                                                               M. Hanson
                                                           July 15, 2012

      An Inquiry into the Nature and the Causes of Web Insecurity


   The year 2011 has been quite exciting from a Web security point of
   view: a number of high-profile security incidents have gotten a lot
   of press attention but also new initiatives, such as the National
   Strategy for Trusted Identities in Cyberspace (NSTIC), had been
   launched to improve the Web identity eco-system.  The NSTIC strategy
   paper, for example, observes problems with Internet security due to
   the widespread usage of low-entropy passwords and the lack of widely
   deployed authentication and attribute assurance services.

   With this memorandum we try to develop a shared vision for how to
   deal with the most pressing Web security problems.

Status of this Memo

   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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 16, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the

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   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  6
   3.  Passwords  . . . . . . . . . . . . . . . . . . . . . . . . . .  7
   4.  Roadmap  . . . . . . . . . . . . . . . . . . . . . . . . . . .  9
   5.  From Two-Party to N-Party  . . . . . . . . . . . . . . . . . . 12
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 14
   7.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 15
   8.  Open Issues  . . . . . . . . . . . . . . . . . . . . . . . . . 16
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 17
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 17
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19

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1.  Introduction

   HTTP is an IETF standard and documented in RFC 2616 [RFC2616] and
   provides the core foundation of the browser-based platform but is
   also widely used for non-browser-based applications in smart phones
   and Internet tablets.  Like any other specification in the IETF HTTP
   also comes with various security mechanims.  Digest authentication
   support in HTTP was published in 1997 with RFC 2069 [RFC2069] and
   later updated in 1999 by RFC 2617 [RFC2617].  The HTTP state
   management mechanism, namely cookies, was initially published in 1997
   with RFC 2109 [RFC2109], and re-written in 2000 by RFC 2965

   For client side authentication two different solution tracks have
   therefore been offered from the IETF, namely TLS client side
   authenication (at that time the usage of client certificates was
   envisioned) and also application level authentication via HTTP basic
   and digest.  TLS-based client authentication using certificates was
   quite complex for end users to configure (and still is complex
   today).  HTTP based authentication on the other hand did not found
   widespread usage either for a number of reasons.  First, the user
   interface was rendered differently than in regular Web application
   form making it less attractive for users.  At that time HTTP had a
   semantic that was closer to file system access control and therefore
   the decision making process was binary, either the user was granted
   access to the resource or it wasn't.  With the HTTP 401 there was no
   way for a user to, for example, recover from a lost password or other
   forms of failure cases.  The authentication and authorization process
   was not seen as continuium but rather as a binary decision.  For
   these reasons form-based authentication mechanisms had found
   widespread acceptance by the Web application developer community.
   Additionally, many Web sites decided to deploy their own
   authentication infrastructure and to store cleartext credentials (in
   most cases a username and a password) into a database.  To add to
   this problem cookies were and still are the most common mechanism for
   session management, i.e., a non-cryptographic way to bind the initial
   authentication to the subsequent HTTP protocol exchanges.  Cookies
   introduce various weaknesses into HTTP, including the ability for
   attackers to perform session hijacking.  In the last few years we
   have seen many press anouncements of password leakage due to
   unauthorized access to these credential databases.

   In the last few years a few other standardization efforts were
   started: RFC 2965 HTTP state management specification was recently
   revised to capture deployment reality [RFC6265].  HTTP Strict
   Transport Layer Security (HSTS)
   [I-D.ietf-websec-strict-transport-sec] allows Web sites to declare
   themselves accessible only via secure connections, and the attemp to

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   clarify the Web Origin Concept [I-D.ietf-websec-origin], which covers
   the principles that underlies the concept of origin as used to scope
   of authority or privilege by user agents.  The HTTPbis Working Group
   [I-D.ietf-httpbis-p7-auth] revises RFC 2616 plus those parts from RFC
   2617 that describe the authentication schemes.

   A lot has changed over the last 10 years in the Web eco-system, as
   briefly described in the sub-sections below, and various efforts are
   still ongoing or have recently been started to provide make Web
   applications even more powerful.  Unfortunately, the underlying Web
   platform had not been able to keep up with these changes and the
   security weaknesses will only became more apparent.  It is time to
   tackle this problem and to develop a common understanding of the
   problem and the desired design goals.

   From Documents to Mobile Code  During the last 10 years the Web has
      changed quite fundamentally with the widespread usage of
      JavaScript.  While Web pages have for a long time been dynamically
      generated the ever increasing capabilities of JavaScript, with
      respect to functionality and performance, have changed the
      security model.  A typical Website collects content from multiple
      other Web sites and delivers it to the user's browser and by
      delivering code inside HTML new security challenges have emerged.
      Also the standardization landscape had been challenged by this new
      development and [I-D.tschofenig-post-standardization] documents
      architectural implications.

   Mashups and Data Sharing  With the increasing specialization of Web
      sites developers started to outsource functionality to other
      sites.  Partially this is a user-convenience aspect (e.g., users
      do not want to create a new address book with every site, publish
      their latest status on each and every site again and again) but
      often also driven by business interestes.  In any case, the need
      to access resources hosted on other sites emerged and often these
      resources were not visible to everyone.  Sharing long-term
      passwords is considered a bad habit and consequently the Web
      Authorization (OAuth) protocol [I-D.ietf-oauth-v2] started to
      become used widely.  OAuth avoids the need to share long-term
      credentials with random Web sites.

   The Real-Time Web  As HTTP became the protocol of choice for many
      application developers, also because of it's ability to go through
      firewalls and NATs, requirements for asynchronous protocol
      communication had to be addressed as well.  HTTP, as a request/
      response protocol, was initially not designed for pushing data
      from the server-side to the client as soon as it is available.
      Long polling requests and other tricks had been used to allow bi-
      directional communication between the HTTP client and the HTTP

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      server.  More recently the BiDirectional or Server-Initiated HTTP
      (hybi) working group was created, which only concerns one aspect
      of real-time communication.  To allow one Web browser to
      communicate directly with another Web browser the same-origin
      security framework utilized by the browser has to be bypassed and
      the work on Real-Time Communication in WEB-browsers (rtcweb) was
      chartered very recently to develop a architecture.  More details
      can be found in [I-D.ietf-rtcweb-security] and in
      [I-D.ietf-rtcweb-overview].  Extending Web clients with real-time
      communication capabilities opens the doors for a large number of
      applications that had previously only been available for
      downloadable applications.

   While astonishing progress has been made in getting the Web
   application eco-system on a par with native applications the
   foundation of the Web platform is still unable to address many of the
   most common security vulnerabilities; problems the Internet community
   had been fighting against for over a decade and had solved for other
   application protocol frameworks and Internet deployment environments.
   This document aims to provide an introduction to the problem that
   will serve as input to an upcoming Web authentication workshop.

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2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

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3.  Passwords

   Passwords have a long history in authentication protocols on the
   Internet.  They appear to be convient for users and are easy to
   provision to users by many Web site.  Still, passwords present a
   number of challenges, including:

   o  Users re-use the same password at multiple sites.  This allows a
      rouge Website provider to attempt to impersonate users on other
      sites.  It also allows a hacker to use stolen passwords obtained
      from one site to be used at a non-compromised site.

   o  Password are stored in cleartext in most cases.  In case of a data
      breach account information, including the password, becomes
      accessible to an attacker.

   o  Users are tricked in typing their password into a Website
      maintained by phishing attempts.  Furthermore, some Websites
      request username and password for access to protected resources
      maintained by other Websites.  While there are technical ways to
      avoid the need for such long-term password sharing practice using
      OAuth some Websites still ask users.

   o  Many password based authenication protocols are not secure against
      eavesdropping, or allow easy ways for offline dictionary attacks.

   o  When end systems are compromised as well then a keyboard logger
      can capture any password sequence a user enters.

   So, why do we need passwords at all?  It is easy to come up with
   solutions that use hardware-based mechanisms (e.g., such as OTP
   tokens), mobile phones, etc.  [Quest] lists some of these mechanisms
   and makes an attempt to classify them.  There are, however, reasons
   why alternatives have not found widespread deployment on the
   Internet, such as

   o  Passwords are cheap (at least the primary costs) for user's and
      service providers.  Hardware tokens on the other hand have a
      certain amount of cost associated with them.

   o  Provisioning new users with passwords is easy.  Tools and
      processes exist and are widely accepted.

   o  Service providers have no external dependency when they manage
      user accounts themselves (unlike with many third party identity
      management solutions).

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   o  Users are familiar with password-based systems and the acceptance
      is good.

   o  Passwords can easily be delegated to others.

   o  Users typically feel quite secure when they are using shared
      secrets and it fits into their mental model of self-securing.

   o  Passwords can easily be transferred to multiple devices used by a
      single user.

   Note that the credential type and the actual form of where these
   credentials are stored (e.g., software, hardware) is orthogonal to
   the actual identity proofing process.  Stronger forms of identity
   proofing (e.g., requiring in-person passport verification) can be
   quite expensive.  There are also secondary costs in the form of
   support calls and education if credential provisioning is more
   complicated, as it is often the case with client certificates.

   Regardless how many disadvantages passwords have they will be with us
   for a long time.  As such, out attempt is therefore to start from the
   currently deployment and to look towards a future where fewer of them
   are used, and if they are used then in a more secure fashion.

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4.  Roadmap

   It is our aim to accomplish three types of goals:

   1.  Reduce the number of passwords used on the Web

   2.  Increase security of how passwords are used

   3.  Broaden the use of other, non-password-based credentials

   A non-goal of this document is to evaluate ways for improving
   identity proofing, which is a requirement for accomplishing higher
   levels of assurance.

   We do not believe that the technical community should be attempting
   to come up with the single and best solution to satisfy these three
   goals.  We would like to leave room for innovation and allow many
   different solutions to co-exist to best suite their deployment.

   Subsequently, we try to highlight a few guiding principles in an
   attempt to come with a way forward.

   Move Authentication down into the Platform:

      Exposing authentication protocol functionality to the user and
      requiring Web application developers to write security related
      code has proven to lead to problems.  Avoid user interaction
      related to security whenever possible but keep in mind that
      authorization decisions, particularly with regard to data sharing,
      require a consent.  Ensure that library support is available for
      Web developers to allow them easy integration of security
      functionality into their applications.  Unfortunately a protocol
      design also needs to consider the transition scenario where the
      Web endpoints are not yet upgraded to support the new
      functionality and that the authentication functionality is not yet

   Design for Growth:

      No single authentication mechanism nor credential type is able to
      fulfill all use cases.  Design for later extensions and develop
      the protocol architecture in such a way that components are
      interchangable.  In particular, there are a number of
      authentication mechanisms already in use in other deployment

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   Context Matters:

      Users require context for all disclosures and the sequence of
      interactions matters.  A monolitic authentication protocol that
      provides mutual authentication is less likely going to capture the
      context related disclosures.  Server-side authentication is the
      first interaction that will have to be provided to guarantee
      genuine content as well as the prerequisity of an early setup for
      a confidentiality protected channel.  Client side authentication
      may, however, come at a much later stage of the application
      interaction.  It is often bundled with an authorization decision
      where different application execution paths depend on the level of

         Discussion: Is it indeed given that client authentication will
         have to happen at a later stage given that platform-level
         authentication proliferates and "authenticated by default"
         becomes the norm?  If so, then strong signals in UIs of
         authenticated status, identity selection, and anonymous/
         pseudonymous modes become more important.  One could compare
         this to the evolution in the telephony communication where
         caller ID information was initially not provided but became the
         norm later and blocking the caller ID instead became the

   Transform Long-Term Passwords to Short-Term Credentials:

      One of the function of authentication protocols is to transform
      long-term credentials into short term secrets.  Long-term
      credentials, such as passwords, require substantial protection in
      a protocol exchange and therefore this interaction often leads to
      a computationally expensive, multi-roundtrip protocol exchange.
      We do, however, encourage protocol designers to make heavier use
      of this transformation step into short term credentials.
      Furthermore, the initial step of entity authentication cannot be
      seen in isolution of the ultimate purpose of application protocol
      interaction that requires session management to take place.  While
      this session management today happens in most cases in a non-
      cryptographic way (i.e., without data origin authentication) we
      believe it is time revisit this practice.

   Keep the User Experience in Mind:

      Design your protocol stack in such a way that developers up the
      stack can give good advice to users.  The use case analysis should

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      include common failure scenarios since error paths need as much
      expressiveness as success paths, whereby expressiveness refers to
      the ability to communicate with the user about failure cases.

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5.  From Two-Party to N-Party

   It would be short sighted to write about a topic like this without
   touching a commonly desired way to reduce the number of long term
   credentials: federated logins

   Federated login allows a user to utilize his credential obtained from
   one organization, acting as the Identity Provider, for accessing a
   resource at another entity, who acts as a Relying Party.  While this
   approach addresses some of our design goals it causes secondary
   problems to appear - particularly related to privacy.

   The following issues in this transition from a two-party to a three-
   party model are to observe:


      How do the three parties find each other?  In particular, how does
      the user (via his user agent) inform the relying party about the
      identity provider it wants to use?  How does the relying party
      inform the user agent (and user) about the identity providers it
      is able and willing to interact with?  How does the relying party
      find the identity provider for a given user?

   Mutual Authentication:

      How do we ensure that each party is authenticated to each other?

   Authorization and Trust:

      What information should the user share with the relying party and
      how can he be reassured that the information is used in the way he
      permitted?  What information is needed by the Relying Party for
      the application specific functionality?  How is the identity
      provider able to protect its users against misbehaving relying


      How should a user be protected against identity providers and
      relying parties conspiring?

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      How can it be ensured that the interactions between the three
      parties are not manipulated or attacked?

   Note: While this text talks about three parties there may well be
   more parties involved in the exchange.  The role of the identity
   consists of a credential provider and an attribute provider that may
   be provided by different parties.  Furthermore, attributes associated
   with personal data may be contributed by multiple attribute
   providers, not just by a single entity.  There may also be additional
   parties involved in the communication between the identity provider
   and the relying party the trust path from the identity provider to
   the relying party.

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6.  IANA Considerations

   This document does not require actions by IANA.

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7.  Acknowledgments

   The content of this document has been created based on discussions
   with a number of persons, including

   o  Jeff Hodges

   o  Michael Garcia

   o  Adam Barth

   o  Brad Hill

   o  Dan Mills

   o  Ed Felton

   o  Tara Whalen

   o  Andy Steingruebl

   o  Tim Polk

   o  Dirk Balfanz

   o  Nico Williams

   o  Tobias Gondrom

   o  Julian Reschke

   We would like to thank them for their input.  We would also like to
   thank the participants of the May 2011 W3C Identity in the Browser
   workshop for their discussion feedback.

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8.  Open Issues

   This document version serves as a starting point for a discussion.
   As such, there are several things not yet mentioned, such as

   o  The introduction section should also point to SPDY as recent
      development in the are of HTTP evolution.

   o  The browser security model should be briefly described.  As a
      comparison, in the browser, we use cross-site communication
      techniques (redirects, JavaScript) and SSL.  In the OS/platform,
      we use trusted APIs, e.g., signed code, OS-level APIs.  In the
      hardware, we use trusted computing bases (e.g., SIM cards or
      locked-down platforms).

   o  The current document does not discuss how the relying party can
      trust the information it receives from the identity provider nor
      how the identity provider makes sure that the relying party adhere
      to any privacy requirements it has.  Various models for
      accomplishing this trust have been mentioned in the past,
      including trust frameworks as used by the General Services
      Administration (GSA) Identity, Credential and Access Management
      (ICAM), or the work envisioned by Application Bridging for
      Federated Access Beyond web (abfab) [I-D.ietf-abfab-arch].

   o  The document should also discuss the problems related to the PKI
      as used by web browsers, the procedures for how trust anchors are
      provisioned, and the lack of liability in the PKI.

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9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC2617]  Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
              Leach, P., Luotonen, A., and L. Stewart, "HTTP
              Authentication: Basic and Digest Access Authentication",
              RFC 2617, June 1999.

   [RFC2109]  Kristol, D. and L. Montulli, "HTTP State Management
              Mechanism", RFC 2109, February 1997.

   [RFC6265]  Barth, A., "HTTP State Management Mechanism", RFC 6265,
              April 2011.

   [RFC2965]  Kristol, D. and L. Montulli, "HTTP State Management
              Mechanism", RFC 2965, October 2000.

9.2.  Informative References

              Hardt, D. and D. Recordon, "The OAuth 2.0 Authorization
              Framework", draft-ietf-oauth-v2-29 (work in progress),
              July 2012.

   [RFC5849]  Hammer-Lahav, E., "The OAuth 1.0 Protocol", RFC 5849,
              April 2010.

              Barth, A., "The Web Origin Concept",
              draft-ietf-websec-origin-06 (work in progress),
              October 2011.

              Hodges, J., Jackson, C., and A. Barth, "HTTP Strict
              Transport Security (HSTS)",
              draft-ietf-websec-strict-transport-sec-11 (work in
              progress), July 2012.

   [RFC2069]  Franks, J., Hallam-Baker, P., Hostetler, J., Leach, P.,
              Luotonen, A., Sink, E., and L. Stewart, "An Extension to

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              HTTP : Digest Access Authentication", RFC 2069,
              January 1997.

              Howlett, J., Hartman, S., Tschofenig, H., Lear, E., and J.
              Schaad, "Application Bridging for Federated Access Beyond
              Web (ABFAB) Architecture", draft-ietf-abfab-arch-03 (work
              in progress), July 2012.

              Fielding, R., Lafon, Y., and J. Reschke, "HTTP/1.1, part
              7: Authentication", draft-ietf-httpbis-p7-auth-19 (work in
              progress), March 2012.

              Tschofenig, H., Aboba, B., Peterson, J., and D. McPherson,
              "Trends in Web Applications and the Implications on
              Standardization", draft-tschofenig-post-standardization-02
              (work in progress), May 2012.

              Alvestrand, H., "Overview: Real Time Protocols for Brower-
              based Applications", draft-ietf-rtcweb-overview-04 (work
              in progress), June 2012.

              Rescorla, E., "Security Considerations for RTC-Web",
              draft-ietf-rtcweb-security-03 (work in progress),
              June 2012.

   [Quest]    "The Quest to Replace Passwords: A Framework for
              Comparative Evaluation of Web Authentication Schemes, In
              Proc. IEEE Symp. on Security and Privacy 2012 (Oakland
              2012)", July 2012.

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Authors' Addresses

   Hannes Tschofenig
   Nokia Siemens Networks
   Linnoitustie 6
   Espoo  02600

   Phone: +358 (50) 4871445
   Email: Hannes.Tschofenig@gmx.net
   URI:   http://www.tschofenig.priv.at

   Sean Turner
   IECA, Inc.
   3057 Nutley Street, Suite 106
   Fairfax, VA  22031

   Email: turners@ieca.com

   Stephen Farrell
   Trinity College Dublin
   Dublin,   2

   Phone: +353-1-896-2354
   Email: stephen.farrell@cs.tcd.ie

   Mike Hanson

   Email: mhanson@mozilla.com

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