Internet DRAFT - draft-mavrogiannopoulos-tpmuri
draft-mavrogiannopoulos-tpmuri
Network Working Group C. Latze
Internet-Draft Swisscom
Intended status: Standards Track N. Mavrogiannopoulos
Expires: July 29, 2013 KU Leuven
January 25, 2013
The TPMKEY URI Scheme
draft-mavrogiannopoulos-tpmuri-01
Abstract
This memo specifies a TPMKEY Uniform Resource Identifier (URI) Scheme
for identifying cryptographic keys stored in TPM chips and accessed
using the TCG Software Stack (TSS). The URI is based on how TPM keys
are identified in the TSS specification.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. TPMKEY URI Scheme Definition . . . . . . . . . . . . . . . . . 3
2.1. TPMKEY URI Scheme Name . . . . . . . . . . . . . . . . . . 3
2.2. TPMKEY URI Scheme Status . . . . . . . . . . . . . . . . . 3
2.3. TPMKEY URI Scheme Syntax . . . . . . . . . . . . . . . . . 3
2.4. TPMKEY URI scheme semantics . . . . . . . . . . . . . . . . 4
2.5. Applicability of the TPMKEY URI scheme . . . . . . . . . . 4
3. Examples of TPMKEY URI Schemes . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . . 6
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1. Introduction
The Trusted Platform Module (TPM) is a trusted piece of hardware
built into many current devices that has been specified by the
Trusted Computing Group (TCG) [TPMMAIN]. In addition to the chip
itself, the TCG defined one standard way to interface with a TPM,
called the TCG Software Stack (TSS) [TSS].
The TSS defines several layers. The most important ones in the
context of this document are the TCG Service Provider (TSP) and the
TCG Core Services (TCS). The TSP provides the TCG services to
applications, which in turn provide access to the TPM. Each
application accesses a single TSP and there is only one TCS for
several TSPs. The task of the TCS is to provide a common set of
services per platform for all TSPs.
TPM keys can be stored either in the TSP (called "user space") or in
the TCS (called "system space"). Furthermore, the TSS assigns a UUID
to each key. That UUID is unique for a specific key hierarchy on a
specific platform. Last, keys can also be stored in so called key
blobs, which are basically files.
The URI scheme defined in this document is designed with a mapping to
TPM keys that are accessed via the TSS 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 TPM key elements.
The URI scheme does not use the optional query and fragment elements.
2. TPMKEY URI Scheme Definition
In accordance with [RFC4395], this section provides the information
required to register the TPMKEY URI scheme.
2.1. TPMKEY URI Scheme Name
tpmkey
2.2. TPMKEY URI Scheme Status
Provisional.
2.3. TPMKEY URI Scheme Syntax
The TPMKEY 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
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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. Rules "unreserved" and "pct-
encoded" in the TPMKEY specification below were imported from
[RFC3986]. As a special case, note that according to [RFC3986], a
space must be percent-encoded.
A TPMKEY URI takes the form (for explanation of Augmented BNF, see
[RFC5234]):
tpmkey-URI = "tpmkey" ":" tpmkey-identifier
tpmkey-identifier = *1(tpmkey-attr *(";" tpmkey-attr))
tpmkey-attr = tpmkey-uuid / tpmkey-file / pk11-storage
tpmkey-reserved-avail = ":" / "[" / "]" / "@" / "!" / "$" /
"&" / "'" / "(" / ")" / "*" / "+" /
"," / "="
tpmkey-char = unreserved / tpmkey-reserved-avail /
pct-encoded
tpmkey-file = "file" "=" *tpmkey-char
tpmkey-uuid = "uuid" "=" UUID
tpmkey-storage = "storage" "=" *1("user" / "system")
More specifically, the attribute "uuid" represents a unique
identifier of a TPM key and its structure is defined in [RFC4122].
The attribute "storage" corresponds to the storage subsystem used
(user or system). The attribute "file" represents a filename and
corresponds to a file that contains a BER-encoded blob in accordance
with the ASN.1 data definitions in the Portable Data section of the
Trusted Computing Group Software Stack Specification Version 1.2.
2.4. TPMKEY URI scheme semantics
The TPMKEY URI scheme is used to reference TPM keys through the TSS.
The allowed operations on the URI are defined by the TSS
specification.
2.5. Applicability of the TPMKEY URI scheme
The TPMKEY URI scheme is relevant to applications and protocols that
need to identify TPM keys that are accessed through TSS.
3. Examples of TPMKEY URI Schemes
One of the simplest forms is from a key stored in the TSP.
tpmkey:uuid=7f468c16-cb7f-11e1-824d-b3a4f4b20343;storage=user
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A TPM key that is stored in a system's file.
tpmkey:file=/path/to/file
4. IANA Considerations
This document registers a URI scheme. The registration template can
be found in Section 2 of this document.
5. Security Considerations
There are security considerations for URI schemes discussed in
[RFC3986].
Given that the TPMKEY URI is also supposed to be used in command line
arguments to running programs, and those arguments can be world
readable on some systems, the URI intentionaly does not allow for
specifying the TPM key password as a URI attribute.
6. Acknowledgements
This document derives from [I-D.pechanec-pkcs11uri]. Furthermore the
authors want to thank Greg Kazmierczak for early feedback.
7. References
7.1. Normative References
[RFC3986] Berners-Lee, T., Fielding, R., and L.
Masinter, "Uniform Resource Identifier
(URI): Generic Syntax", STD 66, RFC 3986,
January 2005.
[RFC4395] Hansen, T., Hardie, T., and L. Masinter,
"Guidelines and Registration Procedures for
New URI Schemes", BCP 35, RFC 4395,
February 2006.
[RFC3629] Yergeau, F., "UTF-8, a transformation
format of ISO 10646", STD 63, RFC 3629,
November 2003.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A
Universally Unique IDentifier (UUID) URN
Namespace", RFC 4122, July 2005.
[TPMMAIN] TCG, "TPM Main Specification Version 1.2",
March 2011.
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[TSS] TCG, "TCG Software Stack (TSS)
Specification Version 1.2", March 2007.
7.2. Informative References
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF
for Syntax Specifications: ABNF", STD 68,
RFC 5234, January 2008.
[I-D.pechanec-pkcs11uri] Pechanec, J. and D. Moffat, "The PKCS#11
URI Scheme", draft-pechanec-pkcs11uri-07
(work in progress), December 2012.
Authors' Addresses
Carolin Latze
Swisscom Switzerland Ltd
Ostermundigenstrasse 93
Bern, 3008
Switzerland
EMail: carolin.latze@swisscom.com
Nikos Mavrogiannopoulos
ESAT/SCD/COSIC KU Leuven - IBBT
Kasteelpark Arenberg 10, bus 2446
Leuven-Heverlee, B-3001
Belgium
EMail: nikos.mavrogiannopoulos@esat.kuleuven.be
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