Enhanced XML Digital Signature Algorithm to Mitigate Wrapping Attacks
draft-enhanced-xml-digital-signature-algorithm-01

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IETF                                                      Jitendra Kumar
Internet-Draft                                          Balaji Rajendran
Intended status: Best Current Practice                  Bindhumadhava BS
Expires: August 8, 2019                                  C-DAC Bangalore
                                                       February 04, 2019

 Enhanced XML Digital Signature Algorithm to Mitigate Wrapping Attacks
           draft-enhanced-xml-digital-signature-algorithm-01

Abstract

   XML signature standard [RFC3275]identifies signed elements by their
   unique identities in the XML document.  However this allows shifting
   of XML elements from one location to another within the same XML
   document, without affecting the ability to verify the signature.
   This flexibility paves the way for an attacker to tweak the original
   XML message without getting noticed by the receiver, leading to XML
   Signature wrapping or rewriting attacks.  This document proposes to
   use absolute XPath as a "Positional Token" and modifies the existing
   XML Digital Signature algorithm to overcome this attack.

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Jitendra Kumar, et al.   Expires August 8, 2019                 [Page 1]
Internet-Draft              Abbreviated Title              February 2019

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  XML Digital Signature structure . . . . . . . . . . . . . . .   3
   3.  Suggested Modified Algorithm  . . . . . . . . . . . . . . . .   3
     3.1.  Algorithm for XML Signature . . . . . . . . . . . . . . .   4
     3.2.  Algorithm for verification of Signature . . . . . . . . .   4
       3.2.1.  Verifying SignedInfo Element Digest with Decrypted
               Digest from SignatureValue element  . . . . . . . . .   5
   4.  Simple Example  . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Algorithm Validation  . . . . . . . . . . . . . . . . . . . .   9
     5.1.  Mitigation of XML Signature wrapping attacks  . . . . . .   9
     5.2.  Mitigation of XML elements jumbling type of wrapping
           attacks . . . . . . . . . . . . . . . . . . . . . . . . .   9
   6.  Conclusion  . . . . . . . . . . . . . . . . . . . . . . . . .   9
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   McIntosh and Austel have illustrated that a SOAP message with XML
   Digital Signature (described in wrapping_attack [wrapping_attack])
   can be forged without invalidating the signature and they have
   further illustrated that a SOAP message content, protected by an XML
   Digital Signature, as specified in WS-Security(refer, WS-Security
   [WS-Security]) can be forged without invalidating the signature.
   This attack is possible because the XML Digital Signature refers to a
   signed element in XML document in a way without giving significance
   to the position within the XML document.  An attacker may inject
   additional nodes replacing the signed nodes while still preserving
   the signed nodes inside the document at different levels in the
   hierarchy of the XML tree, such that it results in successful
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