On Thu, 18 Dec 2014, Nikos Mavrogiannopoulos wrote:
>On Wed, 2014-12-17 at 22:54 -0800, Jan Pechanec wrote:
>
>> + Slot ID is a Cryptoki-assigned number that is not guaranteed stable
>> + across PKCS#11 module initializations. However, slot description and
>> + manufacturer ID may not be enough to uniquely identify a specific
>> + reader. In situations where slot information is necessary use of
>> + "slot-id" attribute may be justified if sufficient slot ID stability
>> + is provided in the PKCS#11 provider itself or externaly.
>
>Hello Jan,
>I'd like to propose the following text instead:
>"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 numbers and
>descriptions. For these cases, when the manufacturer ID is not
>sufficient to uniquely identify a specific reader, the slot
>information could be used to increase the precision of the token
>identification. In other scenarios, using the slot identifiers is
>likely to cause usability issues."
>
>That text discusses both the benefits and the risks.
hi Nikos, thank you, I like that it is more explicit. I made
a minor modification since it could be implied that a slot description
might have a different stability level than a slot manufacturer ID.
- Slot ID is Cryptoki-assigned number that is not guaranteed stable
- across PKCS#11 module initializations. However, slot description and
- manufacturer ID may not be enough to uniquely identify a specific
- reader. In situations where slot information is necessary use of
- "slot-id" attribute may be justified if sufficient slot ID stability
- is provided in the PKCS#11 provider itself or externaly.
+ 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 could
+ be used to increase the precision of the token identification. In
+ other scenarios, using slot IDs is likely to cause usability
+ issues.
attached is draft-pechanec-pkcs11uri-17-v2.txt
there will more versions as I'm gonna address more comments
that came in during the last call.
regards, Jan.
--
Jan Pechanec <jan.pechanec@xxxxxxxxxx>
Network Working Group J. Pechanec
Internet-Draft D. Moffat
Intended status: Standards Track Oracle Corporation
Expires: June 22, 2015 December 19, 2014
The PKCS#11 URI Scheme
draft-pechanec-pkcs11uri-17
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 June 22, 2015.
Copyright Notice
Copyright (c) 2014 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.
Pechanec & Moffat Expires June 22, 2015 [Page 1]
Internet-Draft The PKCS#11 URI Scheme December 2014
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 3
3. PKCS#11 URI Scheme Definition . . . . . . . . . . . . . . . . 3
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 . . . . . . 8
3.5. PKCS#11 URI Matching Guidelines . . . . . . . . . . . . . 10
3.6. PKCS#11 URI Comparison . . . . . . . . . . . . . . . . . 11
4. Examples of PKCS#11 URIs . . . . . . . . . . . . . . . . . . 12
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
6. Security Considerations . . . . . . . . . . . . . . . . . . . 16
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.1. Normative References . . . . . . . . . . . . . . . . . . 16
7.2. Informative References . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
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 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
manufacturer, description, and version. Library attributes may be
necessary to use if more than one Cryptoki library provides a token
Pechanec & Moffat Expires June 22, 2015 [Page 2]
Internet-Draft The PKCS#11 URI Scheme December 2014
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_spec] 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 believed to be sufficient in uniquely identifying 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.
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.
Pechanec & Moffat Expires June 22, 2015 [Page 3]
Internet-Draft The PKCS#11 URI Scheme December 2014
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. 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 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]):
Pechanec & Moffat Expires June 22, 2015 [Page 4]
Internet-Draft The PKCS#11 URI Scheme December 2014
pk11-URI = "pkcs11" ":" pk11-path *1("?" pk11-query)
; Path component and its attributes. Path may be empty.
pk11-path = *1(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-x-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-x-qattr
pk11-query = *1(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 / "&"
; We allow "/" and "?" in the query to be unencoded but "&" must
; be encoded since it may be used as a delimiter in 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("." 1*DIGIT)
pk11-object = "object" "=" *pk11-pchar
pk11-type = "type" "=" *1("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-x-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-x-pattr = "x-" 1*pk11-x-attr-nm-char "=" *pk11-pchar
pk11-x-qattr = "x-" 1*pk11-x-attr-nm-char "=" *pk11-qchar
Pechanec & Moffat Expires June 22, 2015 [Page 5]
Internet-Draft The PKCS#11 URI Scheme December 2014
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. Both path and query
components may contain vendor specific attributes. Such attribute
names must start with an "x-" prefix. Attributes in the path
component are delimited by ';' character, attributes in the query
component use '&' as a delimiter.
The general '/' delimiter was removed from available characters that
do not have to be percent-encoded in the path component so that
generic URI parsers never split the path component into multiple
segments. The '/' delimiter can be used unencoded in the query
component. Delimiter '?' was removed since the PKCS#11 URI uses a
query component. Delimiter '#' was removed so that generic URI
parsers are not confused by unencoded hash characters. All other
generic delimiters are allowed to 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 |
+----------------------+---------------------+----------------------+
| library-manufacturer | ID of the Cryptoki | "manufacturerID" |
| | library | member of the |
| | manufacturer | CK_INFO structure |
+----------------------+---------------------+----------------------+
| library-version | Cryptoki library | "libraryVersion" |
| | version number | member of CK_INFO |
Pechanec & Moffat Expires June 22, 2015 [Page 6]
Internet-Draft The PKCS#11 URI Scheme December 2014
| | | structure |
+----------------------+---------------------+----------------------+
| manufacturer | ID of the token | "manufacturerID" |
| | manufacturer | member of |
| | | CK_TOKEN_INFO |
| | | structure |
+----------------------+---------------------+----------------------+
| model | token model | "model" member of |
| | | CK_TOKEN_INFO |
| | | structure |
+----------------------+---------------------+----------------------+
| object | description (name) | "CKA_LABEL" object |
| | of the object | attribute |
+----------------------+---------------------+----------------------+
| 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 |
+----------------------+---------------------+----------------------+
| 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 |
+----------------------+---------------------+----------------------+
| token | application-defined | "label" member of |
| | label, assigned | the CK_TOKEN_INFO |
| | during token | structure |
| | initialization | |
+----------------------+---------------------+----------------------+
| type | object class (type) | "CKA_CLASS" object |
| | | attribute |
+----------------------+---------------------+----------------------+
Table 1: Mapping between URI path component attributes and PKCS#11
specification names
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,
Pechanec & Moffat Expires June 22, 2015 [Page 7]
Internet-Draft The PKCS#11 URI Scheme December 2014
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_spec].
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. Aside from the query attributes defined in this document,
duplicate 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.
It is recommended to percent-encode the whole value of the "id"
attribute which is supposed to be handled as arbitrary binary data.
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_spec] 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 mandatory. 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 could
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 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 API
producer must be padded with spaces and should not be NULL
terminated.
3.4. PKCS#11 URI Scheme Query Attribute Semantics
An application may 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, we recommend the certain rules to
Pechanec & Moffat Expires June 22, 2015 [Page 8]
Internet-Draft The PKCS#11 URI Scheme December 2014
be followed in descending order for the value of the "pin-source"
attribute:
o if the value represents a local absolute path the implementation
should use it as a PIN file containing the PIN value
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 if the value represents a URI treat it as an object containing the
PIN. Such a URI may be "file:", "https:", another PKCS#11 URI, or
something else.
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.
Use of the "pin-value" attribute may have security related
consequences. Section 6 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 modify default settings for accessing
a PKCS#11 provider or providers by accepting query component
attributes "module-name" and "module-path"."
Processing the URI query module attributes should follow these rules:
o attribute "module-name" is expected to 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
is expected to use a system or application specific locations to
find modules based on the name provided in the attribute.
o attribute "module-path" is expected to 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 always rejected.
Pechanec & Moffat Expires June 22, 2015 [Page 9]
Internet-Draft The PKCS#11 URI Scheme December 2014
o the URI consumer may refuse to accept either of the attributes, or
both. If use of an attribute present in the URI string is not
accepted a warning message should be presented to the provider of
the URI.
o if either of the module attributes is present, only those modules
found matching these query attributes should be used to search for
an object 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 may not contain multiple module attributes of the same name.
Use of the module attributes may have security related consequences.
Section 6 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 three
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 should help a PKCS#11 URI consumer (eg. an
application accepting PKCS#11 URIs) to match the URI with the desired
resource.
o the consumer must 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.
Pechanec & Moffat Expires June 22, 2015 [Page 10]
Internet-Draft The PKCS#11 URI Scheme December 2014
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 should 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 should consider whether a warning message presented to
the user is appropriate in such a case.
o an attribute not present in the URI path but known to a consumer
matches everything. Each additional attribute present in the URI
path further restricts the selection.
o a logical extension of the above is that an empty URI path matches
everything. For example, if used to identify storage objects it
matches all accessible objects in all tokens provided by all
PKCS#11 API producers found in the system.
o use of PIN attributes may change the set of storage objects
visible to the consumer.
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.
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.
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",
Pechanec & Moffat Expires June 22, 2015 [Page 11]
Internet-Draft The PKCS#11 URI Scheme December 2014
"serial", "slot-description", "slot-manufacturer", "token",
"type", and query component attribute "module-name" 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 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 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 "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 it is recommended to
perform case and percent-encoding normalization before the values
are compared but the exact mechanism of such a comparison is left
to the application.
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
Pechanec & Moffat Expires June 22, 2015 [Page 12]
Internet-Draft The PKCS#11 URI Scheme December 2014
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 might 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=/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=/etc/token_pin
Pechanec & Moffat Expires June 22, 2015 [Page 13]
Internet-Draft The PKCS#11 URI Scheme December 2014
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 6 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
Pechanec & Moffat Expires June 22, 2015 [Page 14]
Internet-Draft The PKCS#11 URI Scheme December 2014
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 3.6 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" 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;
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;
x-vend-aaa=value-a
?pin-source=/etc/token_pin
&x-vend-bbb=value-b
Pechanec & Moffat Expires June 22, 2015 [Page 15]
Internet-Draft The PKCS#11 URI Scheme December 2014
5. IANA Considerations
This document moves the "pkcs11" URI scheme from the provisional to
permanent URI scheme registry. The registration template for the URI
scheme is accessible on http://www.iana.org/assignments/uri-schemes.
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, 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.
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.
Pechanec & Moffat Expires June 22, 2015 [Page 16]
Internet-Draft The PKCS#11 URI Scheme December 2014
[pkcs11_spec]
RSA Laboratories, "PKCS #11: Cryptographic Token Interface
Standard v2.20", June 2004.
Authors' Addresses
Jan Pechanec
Oracle Corporation
4180 Network Circle
Santa Clara CA 95054
USA
Email: Jan.Pechanec@xxxxxxxxxx
URI: http://www.oracle.com
Darren J. Moffat
Oracle Corporation
Oracle Parkway
Thames Valley Park
Reading RG6 1RA
UK
Email: Darren.Moffat@xxxxxxxxxx
URI: http://www.oracle.com
Pechanec & Moffat Expires June 22, 2015 [Page 17]