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Network Working Group                                        J. Pechanec
Internet-Draft                                                 D. Moffat
Intended status: Standards Track                      Oracle Corporation
Expires: August 17, 2015                               February 13, 2015


                         The PKCS#11 URI Scheme
                      draft-pechanec-pkcs11uri-21

Abstract

   This memo specifies a PKCS#11 Uniform Resource Identifier (URI)
   Scheme for identifying PKCS#11 objects stored in PKCS#11 tokens, and
   also for identifying PKCS#11 tokens, slots or libraries.  The URI is
   based on how PKCS#11 objects, tokens, slots, 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 August 17, 2015.

Copyright Notice

   Copyright (c) 2015 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
   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.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  PKCS#11 URI Scheme Definition . . . . . . . . . . . . . . . .   4
     3.1.  PKCS#11 URI Scheme Name . . . . . . . . . . . . . . . . .   4
     3.2.  PKCS#11 URI Scheme Status . . . . . . . . . . . . . . . .   4
     3.3.  PKCS#11 URI Scheme Syntax . . . . . . . . . . . . . . . .   4
     3.4.  PKCS#11 URI Scheme Query Attribute Semantics  . . . . . .   9
     3.5.  PKCS#11 URI Matching Guidelines . . . . . . . . . . . . .  11
     3.6.  PKCS#11 URI Comparison  . . . . . . . . . . . . . . . . .  12
     3.7.  Generating PKCS#11 URIs . . . . . . . . . . . . . . . . .  13
   4.  Examples of PKCS#11 URIs  . . . . . . . . . . . . . . . . . .  14
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  17
     5.1.  URI Scheme Registration . . . . . . . . . . . . . . . . .  17
   6.  Internationalization Considerations . . . . . . . . . . . . .  17
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  18
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  18
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  19
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  19
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19

1.  Introduction

   The PKCS #11: Cryptographic Token Interface Standard [PKCS11]
   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 storage object in a PKCS#11 token, an
   existing token itself, a slot, or an existing Cryptoki library (also
   called a producer, module, or provider).  The set of storage object
   types that can be stored in a PKCS#11 token includes a certificate, a
   public, private or 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 a storage object can
   contain an object label, its type, and its ID.  The set of attributes
   that identifies a PKCS#11 token can contain a token label,
   manufacturer name, serial number, and token model.  Attributes that
   can identify a slot are a slot ID, description, and manufacturer.
   Attributes that can identify a Cryptoki library are a library



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   manufacturer, description, and version.  Library attributes may be
   necessary to use if more than one Cryptoki library provides a token
   and/or PKCS#11 objects of the same name.  A set of query attributes
   is provided as well.

   The PKCS#11 URI cannot identify other objects defined in the
   specification [PKCS11] aside from storage objects.  For example,
   objects not identifiable by a PKCS#11 URI include a hardware feature
   and mechanism.  Note that a Cryptoki library does not have to provide
   for storage objects at all.  The URI can still be used to identify a
   specific PKCS#11 token, slot or an API producer in such a case.

   A subset of existing PKCS#11 structure members and object attributes
   was chosen to uniquely identify a PKCS#11 storage object, token,
   slot, 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 storage objects, tokens, and
   slots through the PKCS#11 API, or identify Cryptoki libraries
   themselves.

   The URI scheme defined in this document is designed specifically with
   a mapping to the PKCS#11 API in mind.  The URI uses the scheme, path
   and query components defined in the Uniform Resource Identifier
   (URI): Generic Syntax [RFC3986] document.  The URI 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
   does not use the fragment component.

   If an application has no access to a producer or producers of the
   PKCS#11 API the query component module attributes can be used.
   However, the PKCS#11 URI consumer can always decide to provide its
   own adequate user interface to locate and load PKCS#11 API producers.

   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 [RFC2119].

2.  Contributors

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




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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

   Permanent.

3.3.  PKCS#11 URI Scheme Syntax

   The PKCS#11 URI is a sequence of attribute value pairs separated by a
   semicolon that form a one level path component, optionally followed
   by a query.  Except for the value of the "id" attribute defined later
   in this section, these attribute value pairs and query components are
   composed entirely of textual data and therefore SHOULD all first be
   encoded as octets according to the UTF-8 character encoding
   [RFC3629], in accordance with Section 2.5 of [RFC3986]; 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.  Note that the value of the "id" attribute SHOULD
   NOT be encoded as UTF-8 because it can contain non-textual data,
   instead it SHOULD be entirely percent-encoded.  See important caveats
   in Section 3.5 and Section 6 regarding working with UTF-8 strings
   containing characters outside the US-ASCII character set.

   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.

   The 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.  The syntax of the
   PKCS#11 URI does not impose such limitations.  However, if the
   consumer of a PKCS#11 URI encounters values that would not be
   accepted by the PKCS#11 specification, it MUST refuse the URI as
   invalid.

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





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  pk11-URI             = "pkcs11:" pk11-path [ "?" pk11-query ]
  ; Path component and its attributes.  Path may be empty.
  pk11-path            = [ pk11-pattr *(";" pk11-pattr) ]
  pk11-pattr           = pk11-token / pk11-manuf / pk11-serial /
                         pk11-model / pk11-lib-manuf /
                         pk11-lib-ver / pk11-lib-desc /
                         pk11-object / pk11-type / pk11-id /
                         pk11-slot-desc / pk11-slot-manuf /
                         pk11-slot-id / pk11-v-pattr
  ; Query component and its attributes.  Query may be empty.
  pk11-qattr           = pk11-pin-source / pk11-pin-value /
                         pk11-module-name / pk11-module-path /
                         pk11-v-qattr
  pk11-query           = [ pk11-qattr *("&" pk11-qattr) ]
  ; RFC 3986 section 2.2 mandates all potentially reserved characters
  ; that do not conflict with actual delimiters of the URI do not have
  ; to be percent-encoded.
  pk11-res-avail       = ":" / "[" / "]" / "@" / "!" / "$" /
                         "'" / "(" / ")" / "*" / "+" / "," / "="
  pk11-path-res-avail  = pk11-res-avail / "&"
  ; "/" and "?" in the query component MAY be unencoded but "&" MUST
  ; be encoded since it functions as a delimiter within the component.
  pk11-query-res-avail = pk11-res-avail / "/" / "?" / "|"
  pk11-pchar           = unreserved / pk11-path-res-avail / pct-encoded
  pk11-qchar           = unreserved / pk11-query-res-avail / pct-encoded
  pk11-token           = "token" "=" *pk11-pchar
  pk11-manuf           = "manufacturer" "=" *pk11-pchar
  pk11-serial          = "serial" "=" *pk11-pchar
  pk11-model           = "model" "=" *pk11-pchar
  pk11-lib-manuf       = "library-manufacturer" "=" *pk11-pchar
  pk11-lib-desc        = "library-description" "=" *pk11-pchar
  pk11-lib-ver         = "library-version" "=" 1*DIGIT [ "." 1*DIGIT ]
  pk11-object          = "object" "=" *pk11-pchar
  pk11-type            = "type" "=" ( "public" / "private" / "cert" /
                         "secret-key" / "data" )
  pk11-id              = "id" "=" *pk11-pchar
  pk11-slot-manuf      = "slot-manufacturer" "=" *pk11-pchar
  pk11-slot-desc       = "slot-description" "=" *pk11-pchar
  pk11-slot-id         = "slot-id" "=" 1*DIGIT
  pk11-pin-source      = "pin-source" "=" *pk11-qchar
  pk11-pin-value       = "pin-value" "=" *pk11-qchar
  pk11-module-name     = "module-name" "=" *pk11-qchar
  pk11-module-path     = "module-path" "=" *pk11-qchar
  pk11-v-attr-nm-char  = ALPHA / DIGIT / "-" / "_"
  ; Permitted value of a vendor specific attribute is based on
  ; whether the attribute is used in the path or in the query.
  pk11-v-pattr         = 1*pk11-v-attr-nm-char "=" *pk11-pchar
  pk11-v-qattr         = 1*pk11-v-attr-nm-char "=" *pk11-qchar



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   The URI path component contains attributes that identify a resource
   in a one level hierarchy provided by Cryptoki producers.  The query
   component can contain a few attributes that may be needed to retrieve
   the resource identified by the URI path component.  Attributes in the
   path component are delimited by ';' character, attributes in the
   query component use '&' as a delimiter.

   Both path and query components MAY contain vendor specific
   attributes.  Such attribute names MUST NOT clash with existing
   attribute names.  Note that in accordance with [BCP178], previously
   used convention of starting vendor attributes with an "x-" prefix is
   now deprecated.

   The general '/' delimiter MUST be percent-encoded in the path
   component so that generic URI parsers never split the path component
   into multiple segments.  It MAY be unencoded in the query component.
   Delimiter '?'  MUST be percent-encoded in the path component since
   the PKCS#11 URI uses a query component.  Delimiter '#' MUST be always
   percent-encoded so that generic URI parsers do not treat a hash as a
   beginning of a fragment identifier component.  All other generic
   delimiters MAY be used unencoded (':', '[', ']', and '@') in the
   PKCS#11 URI.

   The following table presents mapping between the PKCS#11 URI path
   component attributes and the PKCS#11 API structure members and object
   attributes.  Given that PKCS#11 URI users may be quite ignorant about
   the PKCS#11 specification the mapping is a product of a necessary
   compromise between how precisely are the URI attribute names mapped
   to the names in the specification and the ease of use and
   understanding of the URI scheme.

   +----------------------+---------------------+----------------------+
   | URI component path   | Attribute           | Attribute            |
   | attribute name       | represents          | corresponds in the   |
   |                      |                     | PKCS#11              |
   |                      |                     | specification to     |
   +----------------------+---------------------+----------------------+
   |                      |                     |                      |
   +----------------------+---------------------+----------------------+
   | id                   | key identifier for  | "CKA_ID" object      |
   |                      | object              | attribute            |
   +----------------------+---------------------+----------------------+
   | library-description  | character-string    | "libraryDescription" |
   |                      | description of the  | member of CK_INFO    |
   |                      | library             | structure.  It is a  |
   |                      |                     | UTF-8 string.        |
   +----------------------+---------------------+----------------------+
   | library-manufacturer | ID of the Cryptoki  | "manufacturerID"     |



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   |                      | library             | member of the        |
   |                      | manufacturer        | CK_INFO structure.   |
   |                      |                     | It is a UTF-8        |
   |                      |                     | string.              |
   +----------------------+---------------------+----------------------+
   | library-version      | Cryptoki library    | "libraryVersion"     |
   |                      | version number      | member of CK_INFO    |
   |                      |                     | structure            |
   +----------------------+---------------------+----------------------+
   | manufacturer         | ID of the token     | "manufacturerID"     |
   |                      | manufacturer        | member of            |
   |                      |                     | CK_TOKEN_INFO        |
   |                      |                     | structure.  It is a  |
   |                      |                     | UTF-8 string.        |
   +----------------------+---------------------+----------------------+
   | model                | token model         | "model" member of    |
   |                      |                     | CK_TOKEN_INFO        |
   |                      |                     | structure.  It is a  |
   |                      |                     | UTF-8 string.        |
   +----------------------+---------------------+----------------------+
   | object               | description (name)  | "CKA_LABEL" object   |
   |                      | of the object       | attribute.  It is a  |
   |                      |                     | UTF-8 string.        |
   +----------------------+---------------------+----------------------+
   | serial               | character-string    | "serialNumber"       |
   |                      | serial number of    | member of            |
   |                      | the token           | CK_TOKEN_INFO        |
   |                      |                     | structure            |
   +----------------------+---------------------+----------------------+
   | slot-description     | slot description    | "slotDescription"    |
   |                      |                     | member of            |
   |                      |                     | CK_SLOT_INFO         |
   |                      |                     | structure.  It is a  |
   |                      |                     | UTF-8 string.        |
   +----------------------+---------------------+----------------------+
   | slot-id              | Cryptoki-assigned   | decimal number of    |
   |                      | value that          | "CK_SLOT_ID" type    |
   |                      | identifies a slot   |                      |
   +----------------------+---------------------+----------------------+
   | slot-manufacturer    | ID of the slot      | "manufacturerID"     |
   |                      | manufacturer        | member of            |
   |                      |                     | CK_SLOT_INFO         |
   |                      |                     | structure.  It is a  |
   |                      |                     | UTF-8 string.        |
   +----------------------+---------------------+----------------------+
   | token                | application-defined | "label" member of    |
   |                      | label, assigned     | the CK_TOKEN_INFO    |
   |                      | during token        | structure.  It is a  |



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   |                      | initialization      | UTF-8 string.        |
   +----------------------+---------------------+----------------------+
   | type                 | object class (type) | "CKA_CLASS" object   |
   |                      |                     | attribute            |
   +----------------------+---------------------+----------------------+

    Table 1: Mapping between URI path component attributes and PKCS#11
                            specification names

   The following table presents mapping between the "type" attribute
   values and corresponding PKCS#11 object classes.

                +-----------------+----------------------+
                | Attribute value | PKCS#11 object class |
                +-----------------+----------------------+
                | cert            | CKO_CERTIFICATE      |
                | data            | CKO_DATA             |
                | private         | CKO_PRIVATE_KEY      |
                | public          | CKO_PUBLIC_KEY       |
                | secret-key      | CKO_SECRET_KEY       |
                +-----------------+----------------------+

     Table 2: Mapping between the "type" attribute and PKCS#11 object
                                  classes

   The query component attribute "pin-source" specifies where the
   application or library should find the normal user's token PIN, the
   "pin-value" attribute provides the normal user's PIN value directly,
   if needed, and the "module-name" and "module-path" attributes modify
   default settings for accessing PKCS#11 providers.  For the definition
   of a "normal user", see [PKCS11].

   The ABNF rules above is a best effort definition and this paragraph
   specifies additional constraints.  The PKCS#11 URI MUST NOT contain
   duplicate attributes of the same name in the URI path component.  It
   means that each attribute may be present at most once in the PKCS#11
   URI path component.  Aside from the query attributes defined in this
   document, duplicate (vendor) attributes MAY be present in the URI
   query component and it is up to the URI consumer to decide on how to
   deal with such duplicates.

   As stated earlier in this section, the value of the "id" attribute
   can contain non-textual data.  This is because the corresponding
   PKCS#11 "CKA_ID" object attribute can contain arbitrary binary data.
   Therefore, the whole value of the "id" attribute SHOULD be percent-
   encoded.





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   The "library-version" attribute represents the major and minor
   version number of the library and its format is "M.N".  Both numbers
   are one byte in size, see the "libraryVersion" member of the CK_INFO
   structure in [PKCS11] for more information.  Value "M" for the
   attribute MUST be interpreted as "M" for the major and "0" for the
   minor version of the library.  If the attribute is present the major
   version number is REQUIRED.  Both "M" and "N" MUST be decimal
   numbers.

   Slot ID is a Cryptoki-assigned number that is not guaranteed stable
   across PKCS#11 module initializations.  However, there are certain
   libraries and modules which provide stable slot identifiers.  For
   these cases, when the slot description and manufacturer ID is not
   sufficient to uniquely identify a specific reader, the slot ID MAY be
   used to increase the precision of the token identification.  In other
   scenarios, using the slot IDs is likely to cause usability issues.

   An empty PKCS#11 URI path component 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], empty character values in a PKCS#11 API
   producer must be padded with spaces and should not be NULL
   terminated.

3.4.  PKCS#11 URI Scheme Query Attribute Semantics

   An application can always ask for a PIN by any means it decides to.
   What is more, in order not to limit PKCS#11 URI portability the "pin-
   source" attribute value format and interpretation is left to be
   implementation specific.  However, the following rules SHOULD be
   followed in descending order for the value of the "pin-source"
   attribute:

   o  if the value represents a URI it SHOULD be treated as an object
      containing the PIN.  Such a URI may be "file:", "https:", another
      PKCS#11 URI, or something else.

   o  if the value contains "|<absolute-command-path>" the
      implementation SHOULD read the PIN from the output of an
      application specified with absolute path "<absolute-command-
      path>".  Note that character "|" representing a pipe does not have
      to be percent encoded in the query component of the PKCS#11 URI.

   o  interpret the value as needed in an implementation dependent way

   If a URI contains both "pin-source" and "pin-value" query attributes
   the URI SHOULD be refused as invalid.




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   Use of the "pin-value" attribute may have security related
   consequences.  Section 7 should be consulted before this attribute is
   ever used.  Standard percent encoding rules SHOULD be followed for
   the attribute value.

   A consumer of PKCS#11 URIs MAY accept query component attributes
   "module-name" and "module-path" in order to modify default settings
   for accessing a PKCS#11 provider or providers.

   Processing the URI query module attributes SHOULD follow these rules:

   o  attribute "module-name" SHOULD contain a case-insensitive PKCS#11
      module name (not path nor filename) without system specific
      affixes.  Such affix could be an ".so" or ".DLL" suffix, or a
      "lib" prefix, for example.  Not using system specific affixes is
      expected to increase portability of PKCS#11 URIs among different
      systems.  A URI consumer searching for PKCS#11 modules SHOULD use
      a system or application specific locations to find modules based
      on the name provided in the attribute.

   o  attribute "module-path" SHOULD contain a system specific absolute
      path to the PKCS#11 module, or a system specific absolute path to
      the directory of where PKCS#11 modules are located.  For security
      reasons, a URI with a relative path in this attribute SHOULD be
      rejected.

   o  the URI consumer MAY refuse to accept either of the attributes, or
      both.  If use of the attribute present in the URI string is not
      accepted a warning message SHOULD be presented to the provider of
      the URI and system specific module locations SHOULD be used.

   o  if either of the module attributes is present, only those modules
      found matching these query attributes SHOULD be used to search for
      an entity represented by the URI.

   o  use of the module attributes does not suppress matching of any
      other URI path component attributes present in a URI.

   o  semantics of using both attributes in the same URI string is
      implementation specific but such use SHOULD be avoided.  Attribute
      "module-name" is preferred to "module-path" due to its system
      independent nature but the latter may be more suitable for
      development and debugging.

   o  a URI MUST NOT contain multiple module attributes of the same
      name.





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   Use of the module attributes may have security related consequences.
   Section 7 should be consulted before these attributes are ever used.

   A word "module" was chosen over word "library" in these query
   attribute names to avoid confusion with semantically different
   library attributes used in the URI path component.

3.5.  PKCS#11 URI Matching Guidelines

   The PKCS#11 URI can identify PKCS#11 storage objects, tokens, slots,
   or Cryptoki libraries.  Note that since a URI may identify four
   different types of entities the context within which the URI is used
   may be needed to determine the type.  For example, a URI with only
   library attributes may either represent all objects in all tokens in
   all Cryptoki libraries identified by the URI, all tokens in those
   libraries, or just the libraries.

   The following guidelines can help a PKCS#11 URI consumer (eg. an
   application accepting PKCS#11 URIs) to match the URI with the desired
   resource.

   o  the consumer needs to know whether the URI is to identify PKCS#11
      storage object(s), token(s), slot(s), or Cryptoki producer(s).

   o  if the consumer is willing to accept query component module
      attributes only those PKCS#11 providers matching these attributes
      SHOULD be worked with.  See Section 3.4 for more information.

   o  an unrecognized attribute in the URI path component, including a
      vendor specific attribute, SHOULD result in an empty set of
      matched resources.  The consumer can consider whether an error
      message presented to the user is appropriate in such a case.

   o  an unrecognized attribute in the URI query SHOULD be ignored.  The
      consumer can consider whether a warning message presented to the
      user is appropriate in such a case.

   o  an attribute not present in the URI path component but known to a
      consumer matches everything.  Each additional attribute present in
      the URI path component further restricts the selection.

   o  a logical extension of the above is that a URI with an empty path
      component matches everything.  For example, if used to identify
      storage objects it matches all accessible objects in all tokens
      provided by all relevant PKCS#11 API producers.

   o  note that use of PIN attributes may change the set of storage
      objects visible to the consumer.



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   o  in addition to query component attributes defined in this
      document, vendor specific query attributes may contain further
      information about how to perform the selection or other related
      information.

   As noted in Section 6, the PKCS#11 specification is not clear about
   how to normalize UTF-8 encoded Unicode characters [RFC3629].  For
   that reason, it is RECOMMENDED not to use characters outside the US-
   ASCII character set for labels and names.  However, those who
   discover a need to use such characters should be cautious,
   conservative, and expend extra effort to be sure they know what they
   are doing and that failure to do so may create both operational and
   security risks.  It means that when matching UTF-8 string based
   attributes (see Table 1) with characters outside the US-ASCII
   repertoire, normalizing all UTF-8 strings before string comparison
   may be the only safe approach.  For example, for objects (keys) it
   means that PKCS#11 attribute search template would only contain
   attributes that are not UTF-8 strings and another pass through
   returned objects is then needed for UTF-8 string comparison after the
   normalization is applied.

3.6.  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.  When working with UTF-8 strings
   with characters outside the US-ASCII character sets, see important
   caveats in Section 3.5 and Section 6.

   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:

   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 path component attributes "library-description",
      "library-manufacturer", "manufacturer", "model", "object",
      "serial", "slot-description", "slot-manufacturer", "token",
      "type", and query component attribute "module-name" MUST be
      compared using a simple string comparison as specified in



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      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 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.

   o  value of attribute "slot-id" MUST be processed as a specific
      scheme-based normalization permitted by Section 6.2.3 of [RFC3986]
      and compared numerically.

   o  value of "pin-source", if containing a "file:" URI or "|<absolute-
      command-path>", 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 the case and
      percent-encoding normalization SHOULD be applied before the values
      are compared but the exact mechanism of comparison is left to the
      application.

   o  value of attribute "module-path" 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.

   o  when comparing vendor specific attributes the case and percent-
      encoding normalization as specified in Section 6.2.2 of [RFC3986]
      SHOULD be applied before the values are compared but the exact
      mechanism of such a comparison is left to the application.

3.7.  Generating PKCS#11 URIs

   When generating URIs for PKCS#11 resources the exact set of
   attributes used in a URI is inherently context specific.  A PKCS#11
   URI template [RFC6570] support MAY be provided by a URI generating
   application to list URIs to access the same resource(s) again if the
   template captured the necessary context.






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4.  Examples of PKCS#11 URIs

   This section contains some examples of how PKCS#11 token objects,
   tokens, slots, and 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].

   An empty PKCS#11 URI might be useful to PKCS#11 consumers.  See
   Section 3.5 for more information on semantics of such a URI.

     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 may not be required.

     pkcs11:object=my-pubkey;type=public

   When a private key is specified either the "pin-source" attribute,
   "pin-value, or an application specific method would be usually used.
   Note that '/' is not percent-encoded in the "pin-source" attribute
   value since this attribute is part of the query component, not the
   path, and thus is separated by '?' from the rest of the URI.

     pkcs11:object=my-key;type=private?pin-source=file:/etc/token

   The following example identifies a certificate in the software token.
   Note an empty value for the attribute "serial" which matches only
   empty "serialNumber" member of the "CK_TOKEN_INFO" structure.  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" MUST
   be percent-encoded.

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




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   The next example covers how to use the "module-name" query attribute.
   Considering that the module is located in /usr/lib/libmypkcs11.so.1
   file, the attribute value is "mypkcs11", meaning only the module name
   without the full path, and without the platform specific "lib" prefix
   and ".so.1" suffix.

     pkcs11:object=my-sign-key;
            type=private
            ?module-name=mypkcs11

   The following example covers how to use the "module-path" query
   attribute.  The attribute may be useful if a user needs to provide
   the key via a PKCS#11 module stored on a removable media, for
   example.  Getting the PIN to access the private key here is left to
   be application specific.

     pkcs11:object=my-sign-key;
            type=private
            ?module-path=/mnt/libmypkcs11.so.1

   In the context where a token is expected the token can be identified
   without specifying any PKCS#11 objects.  A PIN might still be needed
   in the context of listing all objects in the token, for example.
   Section 7 should be consulted before the "pin-value" attribute is
   ever used.

     pkcs11:token=Software%20PKCS%2311%20softtoken;
            manufacturer=Snake%20Oil,%20Inc.
            ?pin-value=the-pin

   In the context where a slot is expected the slot can be identified
   without specifying any PKCS#11 objects in any token it may be
   inserted in it.

     pkcs11:slot-description=Sun%20Metaslot

   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









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   The following example shows an attribute value with a semicolon.  In
   such case it MUST be percent-encoded.  The token attribute value MUST
   be read as "My token; created by Joe".  Lower case letters MAY 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 3.6 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" MUST 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;
            type=cert

   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;
            type=cert

   Both the path and query components MAY contain vendor specific
   attributes.  Attributes in the query component MUST be delimited by
   '&'.

     pkcs11:token=my-token;
            object=my-certificate;
            type=cert;
            vendor-aaa=value-a
            ?pin-source=file:/etc/token_pin
            &vendor-bbb=value-b







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5.  IANA Considerations

5.1.  URI Scheme Registration

   This document moves the "pkcs11" URI scheme from the provisional to
   permanent URI scheme registry.  The registration request complies
   with [RFC4395].

      URI scheme name: pkcs11

      URI scheme status: permanent

      URI scheme syntax: defined in Section 3.3 of [RFCXXXX]

      URI scheme semantics: defined in Section 1 of [RFCXXXX]

      Encoding considerations: see Section 3.3 and Section 6 of
      [RFCXXXX]

      Applications/protocols that use this URI scheme name: for general
      information, see Section 1 of [RFCXXXX].  List of known consumers
      of the PKCS#11 URI include GnuTLS, Gnome, p11-kit, Oracle
      Solaris 11 and higher, OpenSC, OpenConnect, and FreeIPA.

      Interoperability considerations: see Section 6 of [RFCXXXX]

      Security considerations: see Section 7 of [RFCXXXX]

      Contact: Jan Pechanec <Jan.Pechanec@Oracle.COM>, Darren Moffat
      <Darren.Moffat@Oracle.COM>

      Author/Change Controller: IESG <iesg@ietf.org>

      References: [RFCXXXX]

6.  Internationalization Considerations

   The PKCS#11 specification does not specify a canonical form for
   strings of characters of the CK_UTF8CHAR type.  This presents the
   usual false negative and false positive (aliasing) concerns that
   arise when dealing with unnormalized strings.  Because all PKCS#11
   items are local and local security is assumed, these concerns are
   mainly about usability and interoperability.

   In order to improve the user experience, it is RECOMMENDED that
   applications that create PKCS#11 objects or label tokens do not use
   characters outside the US-ASCII character set for the labels.  If
   that is not possible, labels SHOULD be normalized to Normalization



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   Form C (NFC) [UAX15].  For the same reason PKCS#11 libraries, slots
   (token readers), and tokens SHOULD use US-ASCII characters only for
   their names and if that is not possible, they SHOULD normalize their
   names to NFC.  When listing PKCS#11 libraries, slots, tokens, and/or
   objects, an application SHOULD normalize their names to NFC if
   characters outside of the US-ASCII character set are expected.  When
   matching PKCS#11 URIs to libraries, slots, tokens, and/or objects,
   applications MAY convert names to a chosen normalization form before
   the string comparison for matching, as those might pre-date these
   recommendations.  See also Section 3.5.

7.  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, slot, or a library in the future.

   Section 7.2 of [RFC3986] applies since by accepting query component
   attributes "module-name" or "module-path" the consumer potentially
   allows loading of arbitrary code into a process.

   Section 7.5 of [RFC3986] applies since the PKCS#11 URI may be used in
   world readable command line arguments to run applications, stored in
   public configuration files, or otherwise used in clear text.  For
   that reason the "pin-value" attribute should only be used if the URI
   string itself is protected with the same level of security as the
   token PIN itself otherwise is.

   The PKCS#11 specification does not provide means to authenticate
   devices to users; it only allows to authenticate users to tokens.
   Instead, local and physical security are demanded: the user must be
   in possession of their tokens, and system into whose slots the users'
   tokens are inserted must be secure.  As a result, the usual security
   considerations regarding normalization do not arise.  For the same
   reason, confusable script issues also do not arise.  Nonetheless, if
   use of characters outside the US-ASCII character set is required, it
   is best to normalize to NFC all strings appearing in PKCS#11 API
   elements.  See also Section 6.

8.  References








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8.1.  Normative References

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

   [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.

8.2.  Informative References

   [BCP178]   Saint-Andre, P., Crocker, D., and M. Nottingham,
              "Deprecating the "X-" Prefix and Similar Constructs in
              Application Protocols", RFC 6648, BCP 178, June 2012.

   [PKCS11]   RSA Laboratories, "PKCS #11: Cryptographic Token Interface
              Standard v2.20", June 2004.

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

   [RFC6570]  Gregorio, J., Fielding, R., Hadley, M., Nottingham, M.,
              and D. Orchard, "URI Template", RFC 6570, March 2012.

   [UAX15]    Davis, M., Ed., Whistler, K., Ed., and Unicode Consortium,
              "Unicode Standard Annex #15 - Unicode Normalization Forms,
              Version Unicode 7.0.0", June 2014.

Authors' Addresses

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

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






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   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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