Issues in Identifier Comparison for Security Purposes
draft-iab-identifier-comparison-02

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Last updated 2012-05-08
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Network Working Group                                     D. Thaler, Ed.
Internet-Draft                                                 Microsoft
Intended status: Informational                               May 8, 2012
Expires: November 9, 2012

         Issues in Identifier Comparison for Security Purposes
                 draft-iab-identifier-comparison-02.txt

Abstract

   Identifiers such as hostnames, URIs, and email addresses are often
   used in security contexts to identify security principals and
   resources.  In such contexts, an identifier supplied via some
   protocol is often compared against some policy to make security
   decisions such as whether the principal may access the resource, what
   level of authentication or encryption is required, etc.  If the
   parties involved in a security decision use different algorithms to
   compare identifiers, then failure scenarios ranging from denial of
   service to elevation of privilege can result.

Status of this Memo

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   This Internet-Draft will expire on November 9, 2012.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   (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

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   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Canonicalization . . . . . . . . . . . . . . . . . . . . .  4
   2.  Security Uses  . . . . . . . . . . . . . . . . . . . . . . . .  5
     2.1.  Types of Identifiers . . . . . . . . . . . . . . . . . . .  6
     2.2.  False Positives and Negatives  . . . . . . . . . . . . . .  7
     2.3.  Hypothetical Example . . . . . . . . . . . . . . . . . . .  8
   3.  Common Identifiers . . . . . . . . . . . . . . . . . . . . . .  9
     3.1.  Hostnames  . . . . . . . . . . . . . . . . . . . . . . . .  9
       3.1.1.  IPv4 Literals  . . . . . . . . . . . . . . . . . . . .  9
       3.1.2.  IPv6 Literals  . . . . . . . . . . . . . . . . . . . . 11
       3.1.3.  Internationalization . . . . . . . . . . . . . . . . . 12
       3.1.4.  Resolution for comparison  . . . . . . . . . . . . . . 12
     3.2.  Ports and Service Names  . . . . . . . . . . . . . . . . . 13
     3.3.  URIs . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
       3.3.1.  Scheme component . . . . . . . . . . . . . . . . . . . 15
       3.3.2.  Authority component  . . . . . . . . . . . . . . . . . 15
       3.3.3.  Path component . . . . . . . . . . . . . . . . . . . . 16
       3.3.4.  Query component  . . . . . . . . . . . . . . . . . . . 16
       3.3.5.  Fragment component . . . . . . . . . . . . . . . . . . 16
       3.3.6.  Resolution for comparison  . . . . . . . . . . . . . . 17
     3.4.  Email Address-like Identifiers . . . . . . . . . . . . . . 17
   4.  General Internationalization Issues  . . . . . . . . . . . . . 17
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 18
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 19
   8.  Informative References . . . . . . . . . . . . . . . . . . . . 19
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 21

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1.  Introduction

   In computing and the Internet, various types of "identifiers" are
   used to identify humans, devices, content, etc.  Before discussing
   security issues, we first give some background on some typical
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