Network Working Group J. Pechanec Internet-Draft D. Moffat Intended status: Standards Track Oracle Corporation Expires: June 29, 2013 December 26, 2012 The PKCS#11 URI Scheme draft-pechanec-pkcs11uri-07 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/. 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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 Pechanec & Moffat Expires June 29, 2013 [Page 1] Internet-Draft The PKCS#11 URI Scheme December 2012 described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 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 4. Examples of PKCS#11 URIs . . . . . . . . . . . . . . . . . . . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 8 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 7.1. Normative References . . . . . . . . . . . . . . . . . . . 9 7.2. Informative References . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 Pechanec & Moffat Expires June 29, 2013 [Page 2] Internet-Draft The PKCS#11 URI Scheme December 2012 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, or 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 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. Note that the 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 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 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. 2. Contributors Stef Walter, Nikos Mavrogiannopoulos, Nico Williams, and Dan Winship contributed to the development of this document. Pechanec & Moffat Expires June 29, 2013 [Page 3] Internet-Draft The PKCS#11 URI Scheme December 2012 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 scheme is a sequence of attribute value pairs separated by a semicolon. In accordance with [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 this rule for the "id" attribute, as stated in Section 3.3. Grammar rules "unreserved" and "pct-encoded" in the PKCS#11 URI specification below were imported from [RFC3986]. As a special case, note that according to [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 will not affect existing attributes. Pechanec & Moffat Expires June 29, 2013 [Page 4] Internet-Draft The PKCS#11 URI Scheme December 2012 A PKCS#11 URI takes the form (for explanation of Augmented BNF, see [RFC5234]): 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" "=" *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 "hier-part" generic URI component as defined in [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" Pechanec & Moffat Expires June 29, 2013 [Page 5] Internet-Draft The PKCS#11 URI Scheme December 2012 corresponds to the "model" member of CK_TOKEN_INFO, the attribute "library-manufacturer" represents the Cryptoki library manufacturer 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 "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. It is recommended to percent-encode the whole value of the "id" attribute which is supposed to be handled as arbitrary binary data. 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 which is allowed by [RFC3986]. Also note that all spaces as part of the URI are percent-encoded, as required by [RFC3986]. 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 Pechanec & Moffat Expires June 29, 2013 [Page 6] Internet-Draft The PKCS#11 URI Scheme December 2012 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 that all attributes may have an empty value. In our case, "serial" is empty. It is up to the consumer of the URI to perform necessary checks if that is not allowed. 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 The Cryptoki library alone can be also identified without specifying any PKCS#11 objects. 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 value must be read as "My token; created by Joe". Lower characters can also be used in percent-encoding as shown below in the "id" attribute value but note that [RFC3986] recommends to use upercase hexadecimal digits for all percent-encoded characters. Library version ".9" should be interpreted as "0" for the major and "9" for the minor Pechanec & Moffat Expires June 29, 2013 [Page 7] Internet-Draft The PKCS#11 URI Scheme December 2012 version of the library. Similarly, library version "9" would be interpreted as "9" for the major and "0" for the minor version of the library. pkcs11:token=My%20token%25%20created%20by%20Joe; library-version=.9 id=%69%95%3e%5c%f4%bd%ec%91; And 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 strange substring '\;'". pkcs11:token=A%20name%20with%20a%20strange%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 5. IANA Considerations This document registers a URI scheme. 6. Security Considerations There are security considerations for URI schemes discussed in [RFC3986]. More specifically, Section 7.1 of [RFC3986] applies since there is no guarantee that the same 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 intentionaly does not allow for specifying the PKCS#11 token PIN as a URI attribute. Pechanec & Moffat Expires June 29, 2013 [Page 8] Internet-Draft The PKCS#11 URI Scheme December 2012 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. 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 Pechanec & Moffat Expires June 29, 2013 [Page 9]