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Network Working Group                                        J. Pechanec
Internet-Draft                                                 D. Moffat
Intended status: Standards Track                      Oracle Corporation
Expires: January 10, 2014                                  July 09, 2013


                         The PKCS#11 URI Scheme
                      draft-pechanec-pkcs11uri-11

Abstract

   This memo specifies a PKCS#11 Uniform Resource Identifier (URI)
   Scheme for identifying PKCS#11 objects stored in PKCS#11 tokens, for
   identifying PKCS#11 tokens themselves, or for identifying PKCS#11
   libraries.  The URI is based on how PKCS#11 objects, tokens, and
   libraries are identified in the PKCS#11 Cryptographic Token Interface
   Standard.

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   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 10, 2014.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.












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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  PKCS#11 URI Scheme Definition . . . . . . . . . . . . . . . .   3
     3.1.  PKCS#11 URI Scheme Name . . . . . . . . . . . . . . . . .   3
     3.2.  PKCS#11 URI Scheme Status . . . . . . . . . . . . . . . .   3
     3.3.  PKCS#11 URI Scheme Syntax . . . . . . . . . . . . . . . .   4
     3.4.  PKCS#11 URI Comparison  . . . . . . . . . . . . . . . . .   6
   4.  Examples of PKCS#11 URIs  . . . . . . . . . . . . . . . . . .   7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   The PKCS #11: Cryptographic Token Interface Standard [pkcs11_spec]
   specifies an API, called Cryptoki, for devices which hold
   cryptographic information and perform cryptographic functions.
   Cryptoki, pronounced crypto-key and short for cryptographic token
   interface, follows a simple object-based approach, addressing the
   goals of technology independence (any kind of device may be used) and
   resource sharing (multiple applications may access multiple devices),
   presenting applications with a common, logical view of the device - a
   cryptographic token.

   It is desirable for applications or libraries that work with PKCS#11
   tokens to accept a common identifier that consumers could use to
   identify an existing PKCS#11 object in a PKCS#11 token, an existing
   token itself, or an existing Cryptoki library.  The set of object
   types that can be stored in a PKCS#11 token includes a public key, a
   private key, a certificate, a secret key, and a data object.  These
   objects can be uniquely identifiable via the PKCS#11 URI scheme
   defined in this document.  The set of attributes describing an object
   can contain an object label, its type, and its ID.  The set of



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   attributes that identifies a PKCS#11 token can contain a token label,
   a manufacturer name, a serial number, and a token model.  Attributes
   that can identify a Cryptoki library are a library manufacturer, a
   library description, and a library version.  Library attributes may
   be necessary to use if more than one PKCS#11 module provides a token
   and/or PKCS#11 objects of the same name(s).

   A subset of existing PKCS#11 structure members and object attributes
   was chosen believed to be sufficient in uniquely identifying a
   PKCS#11 token, object, or library in a configuration file, on a
   command line, or in a configuration property of something else.
   Should there be a need for a more complex information exchange on
   PKCS#11 entities a different means of data marshalling should be
   chosen accordingly.

   A PKCS#11 URI is not intended to be used to create new PKCS#11
   objects in tokens, or to create PKCS#11 tokens.  It is solely to be
   used to identify and work with existing objects, tokens, and Cryptoki
   libraries through the PKCS#11 API.

   The URI scheme defined in this document is designed specifically with
   a mapping to the PKCS#11 API in mind.  The URI uses only the scheme
   and the path components which are required by the Uniform Resource
   Identifier (URI): Generic Syntax [RFC3986].  The URI scheme does not
   use the hierarchical element for a naming authority in the path since
   the authority part could not be mapped to PKCS#11 API elements.  The
   URI scheme does not use the optional query and fragment elements.

   If an application has no access to a producer or producers of the
   PKCS#11 API it is left to its implementation to provide adequate user
   interface to locate and load such producer(s).

2.  Contributors

   Stef Walter, Nikos Mavrogiannopoulos, Nico Williams, Dan Winship, and
   Jaroslav Imrich contributed to the development of this document.

3.  PKCS#11 URI Scheme Definition

   In accordance with [RFC4395], this section provides the information
   required to register the PKCS#11 URI scheme.

3.1.  PKCS#11 URI Scheme Name

   pkcs11

3.2.  PKCS#11 URI Scheme Status




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   Permanent.

3.3.  PKCS#11 URI Scheme Syntax

   The PKCS#11 URI scheme is a sequence of attribute value pairs
   separated by a semicolon.  In accordance with Section 2.5 of
   [RFC3986], the data should first be encoded as octets according to
   the UTF-8 character encoding [RFC3629]; then only those octets that
   do not correspond to characters in the unreserved set or to permitted
   characters from the reserved set should be percent-encoded.  This
   specification suggests one allowable exception to that rule for the
   "id" attribute, as stated later in this section.  Grammar rules
   "unreserved" and "pct-encoded" in the PKCS#11 URI specification below
   are imported from [RFC3986].  As a special case, note that according
   to Appendix A of [RFC3986], a space must be percent-encoded.

   PKCS#11 specification imposes various limitations on the value of
   attributes, be it a more restrictive character set for the "serial"
   attribute or fixed sized buffers for almost all the others, including
   "token", "manufacturer", and "model" attributes.  However, the
   PKCS#11 URI notation does not impose such limitations aside from
   removing generic and PKCS#11 URI delimiters from a permitted
   character set.  We believe that being too restrictive on the
   attribute values could limit the PKCS#11 URI's usefulness.  What is
   more, possible future changes to the PKCS#11 specification should not
   affect existing attributes.

   A PKCS#11 URI takes the form (for explanation of Augmented BNF, see
   [RFC5234]):






















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   pk11-URI            = "pkcs11" ":" pk11-identifier
   pk11-identifier     = *1(pk11-attr *(";" pk11-attr))
   pk11-attr           = pk11-token / pk11-manuf / pk11-serial /
                         pk11-model / pk11-lib-manuf /
                         pk11-lib-ver / pk11-lib-desc /
                         pk11-object / pk11-object-type / pk11-id /
                         pk11-pin-source
   ; Section 2.2 of RFC 3986 specifies that all potentially reserved
   ; characters that do not conflict with actual delimiters of the URI
   ; do not have to be percent-encoded. So, ";" was removed as a
   ; sub-delimiter of the PKCS#11 URI's path and "/", "?", and "#" as
   ; delimiters of generic URI components.
   pk11-reserved-avail = ":" / "[" / "]" / "@" / "!" / "$" /
                         "&" / "'" / "(" / ")" / "*" / "+" /
                         "," / "="
   pk11-char           = unreserved / pk11-reserved-avail /
                         pct-encoded
   pk11-token          = "token" "=" *pk11-char
   pk11-manuf          = "manufacturer" "=" *pk11-char
   pk11-serial         = "serial" "=" *pk11-char
   pk11-model          = "model" "=" *pk11-char
   pk11-lib-manuf      = "library-manufacturer" "=" *pk11-char
   pk11-lib-desc       = "library-description" "=" *pk11-char
   pk11-lib-ver        = "library-version" "=" 1*DIGIT *1("." 1*DIGIT)
   pk11-object         = "object" "=" *pk11-char
   pk11-object-type    = "object-type" "=" *1("public" / "private" /
                         "cert" / "secret-key" / "data")
   pk11-id             = "id" "=" *pk11-char
   pk11-pin-source     = "pin-source" "=" *pk11-char


   More specifically, '/' delimiter of generic URI components was
   removed from available characters that do not have to be percent-
   encoded so that the initial part of a PKCS#11 URI is never confused
   with "path-rootless" part of the "hier-part" generic URI component as
   defined in Section 3 of [RFC3986].  Delimiters '?' and '#' of generic
   URI components were removed to allow for possible future extensions
   of the PKCS#11 URI.  All other delimiters of generic URI components
   are allowed to be used unencoded (':', '[', ']', and '@') in the
   PKCS#11 URI.

   The attribute "token" represents a token label and corresponds to the
   "label" member of the CK_TOKEN_INFO structure, the attribute
   "manufacturer" corresponds to the "manufacturerID" member of
   CK_TOKEN_INFO, the attribute "serial" corresponds to the
   "serialNumber" member of CK_TOKEN_INFO, the attribute "model"
   corresponds to the "model" member of CK_TOKEN_INFO, the attribute
   "library-manufacturer" represents the Cryptoki library manufacturer



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   and corresponds to the "manufacturerID" member of the CK_INFO
   structure, the attribute "library-description" corresponds to the
   "libraryDescription" member of CK_INFO, the attribute "library-
   version" corresponds to the "libraryVersion" member of CK_INFO, the
   attribute "object" represents a PKCS#11 object label and corresponds
   to the "CKA_LABEL" object attribute, the attribute "object-type"
   represents the type of the object and corresponds to the "CKA_CLASS"
   object attribute, the attribute "id" represents the object ID and
   corresponds to the "CKA_ID" object attribute, and the attribute "pin-
   source" specifies where the application or library should find the
   token PIN, if needed.

   The PKCS#11 URI must not contain duplicate attributes of the same
   name.  It means that each attribute may be present at most once in a
   PKCS#11 URI string.

   The "pin-source" attribute may represent a filename that contains a
   token PIN but an application may overload this attribute.  For
   example, "pin-source=%7Cprog-name" could mean to read a PIN from an
   external application (%7C denotes a pipe '|' character).  Note that
   an application may always ask for a PIN and/or interpret the "pin-
   source" attribute by any means it decides to.  However, as discussed
   in Section 6, the attribute should never contain the PIN itself.

   It is recommended to percent-encode the whole value of the "id"
   attribute which is supposed to be handled as arbitrary binary data.
   Value "M" of the "library-version" attribute should be interpreted as
   "M" for the major and "0" for the minor version of the library.  Note
   that if the "library-version" attribute is present, the major version
   number is mandatory.

   An empty PKCS#11 URI attribute that does allow for an empty value
   matches a corresponding structure member or an object attribute with
   an empty value.  Note that according to the PKCS#11 specification
   [pkcs11_spec], empty character values in a PKCS#11 producer must be
   padded with spaces and should not be NULL terminated.

3.4.  PKCS#11 URI Comparison

   Comparison of two URIs is a way of determining whether the URIs are
   equivalent without comparing the actual resource the URIs point to.
   The comparison of URIs aims to minimize false negatives while
   strictly avoiding false positives.

   Two PKCS#11 URIs are said to be equal if URIs as character strings
   are identical as specified in Section 6.2.1 of [RFC3986], or if both
   following rules are fulfilled:




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   o  set of attributes present in the URI is equal.  Note that the
      ordering of attributes in the URI string is not significant for
      the mechanism of comparison.

   o  values of respective attributes are equal based on rules specified
      below

   The rules for comparing values of respective attributes are:

   o  values of attributes "library-description", "library-
      manufacturer", "manufacturer", "model", "object", "object-type",
      "serial", and "token" must be compared using a simple string
      comparison as specified in Section 6.2.1 of [RFC3986] after the
      case and the percent-encoding normalization are both applied as
      specified in Section 6.2.2 of [RFC3986]

   o  value of attribute "id" must be compared using the simple string
      comparison after all bytes are percent-encoded using uppercase
      letters for digits A-F

   o  value for attribute "pin-source", if deemed containing the
      filename with the PIN value, must be compared using the simple
      string comparison after the full syntax based normalization as
      specified in Section 6.2.2 of [RFC3986] is applied.  If value of
      the "pin-source" attribute is believed to be overloaded it is
      recommended to perform case and percent-encoding normalization
      before the values are compared but the exact mechanism of
      comparison is left to the application.

   o  value of attribute "library-version" must be processed as a
      specific scheme-based normalization permitted by Section 6.2.3 of
      [RFC3986].  The value must be split into a major and minor version
      with character '.' (dot) serving as a delimiter.  Library version
      "M" must be treated as "M" for the major version and "0" for the
      minor version.  Resulting minor and major version numbers must be
      then separately compared numerically.

4.  Examples of PKCS#11 URIs

   This section contains some examples of how PKCS#11 token objects,
   PKCS#11 tokens, and PKCS#11 libraries can be identified using the
   PKCS#11 URI scheme.  Note that in some of the following examples,
   newlines and spaces were inserted for better readability.  As
   specified in Appendix C of [RFC3986], whitespace should be ignored
   when extracting the URI.  Also note that all spaces as part of the
   URI are percent-encoded, as specified in Appendix A of [RFC3986].





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   An empty PKCS#11 URI might be useful to PKCS#11 consumers:

   pkcs11:


   One of the simplest and most useful forms might be a PKCS#11 URI that
   specifies only an object label and its type.  The default token is
   used so the URI does not specify it.  Note that when specifying
   public objects, a token PIN might not be required.

   pkcs11:object=my-pubkey;object-type=public


   When a private key is specified either the "pin-source" attribute or
   an application specific method would be usually used.  Also note that
   '/' must be percent-encoded in the "pin-source" attribute value since
   it must be prevented to be mistaken for a path segment delimiter.

   pkcs11:object=my-key;object-type=private;
          pin-source=%2Fetc%2Ftoken_pin


   The following example identifies a certificate in the software token.
   Note an empty value for the attribute "serial".  Also note that the
   "id" attribute value is entirely percent-encoded, as recommended.
   While ',' is in the reserved set it does not have to be percent-
   encoded since it does not conflict with any sub-delimiters used.  The
   '#' character as in "The Software PKCS#11 Softtoken" is a general
   delimiter as '/' so it must be percent-encoded, too.

   pkcs11:token=The%20Software%20PKCS%2311%20Softtoken;
          manufacturer=Snake%20Oil,%20Inc.;
          serial=;
          model=1.0;
          object=my-certificate;
          object-type=cert;
          id=%69%95%3E%5C%F4%BD%EC%91;
          pin-source=%2Fetc%2Ftoken_pin


   The token alone can be identified without specifying any PKCS#11
   objects.  A PIN may still be needed to list all objects, for example.

   pkcs11:token=Software%20PKCS%2311%20softtoken;
          manufacturer=Snake%20Oil,%20Inc.;
          pin-source=%2Fetc%2Ftoken_pin





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   The Cryptoki library alone can be also identified without specifying
   a PKCS#11 token or object.

   pkcs11:library-manufacturer=Snake%20Oil,%20Inc.;
          library-description=Soft%20Token%20Library;
          library-version=1.23


   The following example shows that the attribute value can contain a
   semicolon.  In such case, it is percent-encoded.  The token attribute
   value must be read as "My token; created by Joe".  Lower case letters
   can also be used in percent-encoding as shown below in the "id"
   attribute value but note that Sections 2.1 and 6.2.2.1 of [RFC3986]
   read that all percent-encoded characters should use the uppercase
   hexadecimal digits.  More specifically, if the URI string was to be
   compared, the algorithm defined in Section 3.4 explicitly requires
   percent-encoding to use the uppercase digits A-F in the "id"
   attribute values.  And as explained in Section 3.3, library version
   "3" should be interpreted as "3" for the major and "0" for the minor
   version of the library.

   pkcs11:token=My%20token%25%20created%20by%20Joe;
          library-version=3
          id=%01%02%03%Ba%dd%Ca%fe%04%05%06;


   If there is any need to include literal "%;" substring, for example,
   both characters must be escaped.  The token value must be read as "A
   name with a substring %;".

   pkcs11:token=A%20name%20with%20a%20substring%20%25%3B;
          object=my-certificate;
          object-type=cert;
          pin-source=%2Fetc%2Ftoken_pin


   The next example includes a small A with acute in the token name.  It
   must be encoded in octets according to the UTF-8 character encoding
   and then percent-encoded.  Given that a small A with acute is U+225
   unicode code point, the UTF-8 encoding is 195 161 in decimal, and
   that is "%C3%A1" in percent-encoding.

   pkcs11:token=Name%20with%20a%20small%20A%20with%20acute:%20%C3%A1;
          object=my-certificate;
          object-type=cert






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5.  IANA Considerations

   This document registers a URI scheme.

6.  Security Considerations

   There are general security considerations for URI schemes discussed
   in Section 7 of [RFC3986].

   From those security considerations, Section 7.1 of [RFC3986] applies
   since there is no guarantee that the same PKCS#11 URI will always
   identify the same object, token, or a library in the future.

   Section 7.5 of [RFC3986] applies since the PKCS#11 URI may be used in
   command line arguments to run applications, and those arguments can
   be world readable on some systems.  For that reasons, the URI
   intentionally does not allow for specifying the PKCS#11 token PIN as
   a URI attribute.

7.  References

7.1.  Normative References

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", RFC 3629, STD 63, November 2003.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", RFC 3986, STD
              66, January 2005.

   [RFC5234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", RFC 5234, STD 68, January 2008.

7.2.  Informative References

   [RFC4395]  Hansen, T., Hardie, T., and L. Masinter, "Guidelines and
              Registration Procedures for New URI Schemes", RFC 4395,
              February 2006.

   [pkcs11_spec]
              RSA Laboratories, "PKCS #11: Cryptographic Token Interface
              Standard v2.20", June 2004.









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Authors' Addresses

   Jan Pechanec
   Oracle Corporation
   4180 Network Circle
   Santa Clara  CA 95054
   USA

   Email: Jan.Pechanec@Oracle.COM
   URI:   http://www.oracle.com


   Darren J. Moffat
   Oracle Corporation
   Oracle Parkway
   Thames Valley Park
   Reading  RG6 1RA
   UK

   Email: Darren.Moffat@Oracle.COM
   URI:   http://www.oracle.com






























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