Internet DRAFT - draft-birkholz-sacm-coswid
draft-birkholz-sacm-coswid
SACM Working Group H. Birkholz
Internet-Draft Fraunhofer SIT
Intended status: Standards Track J. Fitzgerald-McKay
Expires: September 22, 2016 Department of Defense
C. Schmidt
The MITRE Corporation
D. Waltermire
NIST
March 21, 2016
Concise Software Identifiers
draft-birkholz-sacm-coswid-00
Abstract
This document defines a concise representation of ISO 19770-2:2015
Software Identifiers (SWID tags) that is interoperable with the XML
schema definition of ISO 19770-2:2015.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Concise SWID data definition . . . . . . . . . . . . . . . . 3
3. COSE signatures for Concise SWID tags . . . . . . . . . . . . 7
4. IANA considerations . . . . . . . . . . . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
7. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 9
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 10
9.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
SWID tags have several use-applications including but not limited to:
o Software Inventory Management, a part of the Software Asset
Management [SAM] process, which requires an accurate list of
discernible deployed software instances.
o Vulnerability Assessment, which requires a semantic link between
standardized vulnerability descriptions and [X.1520] IT-assets.
o Remote Attestation, which requires a link between golden (well-
known) measurements and software instances [I-D-birkholz-tuda].
SWID tags, as defined in ISO-19770-2:2015 [SWID], provide a
standardized format for a record that identifies and describes a
specific release of a software product. Different software products,
and even different releases of a particular software product, each
have a different SWID tag record associated with them. In addition
to defining the format of these records, ISO-19770-2:2015 defines
requirements concerning the SWID tag lifecycle. Specifically, when a
software product is installed on an endpoint, that product's SWID tag
is also installed. Likewise, when the product is uninstalled or
replaced, the SWID tag is deleted or replaced, as appropriate. As a
result, ISO-19770-2:2015 describes a system wherein there is a
correspondence between the set of installed software products on an
endpoint, and the presence on that endpoint of the SWID tags
corresponding to those products.
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SWID tags are meant to be flexible and able to express a broad set of
metadata about a software product. Moreover, there are multiple
types of SWID tags, each providing different types of information.
For example, a "corpus tag" is used to describe an application's
installation image on an installation media, while a "patch tag" is
meant to describe a patch that modifies some other application.
While there are very few required fields in SWID tags, there are many
optional fields that support different uses of these different types
of tags. While a SWID tag that consisted only of required fields
could be a few hundred bytes in size, a tag containing many of the
optional fields could be many orders of magnitude larger.
This document defines a more concise representation of SWID tags in
the Concise Binary Object Representation (CBOR) [RFC7049]. This is
described via the CBOR Data Definition Language (CDDL)
[I-D.greevenbosch-appsawg-cbor-cddl]. The resulting Concise SWID
data definition is interoperable with the XML schema definition of
ISO-19770-2:2015 [SWID]. The vocabulary, i.e., the CDDL names of the
types and members used in the Concise SWID data definition, is mapped
to more concise labels represented as small integers. The names used
in the CDDL and the mapping to the CBOR representation using integer
labels is based on the vocabulary of the XML attribute and element
names defined in ISO-19770-2:2015.
Real-world instances of SWID tags can be fairly large, and the
communication of SWID tags in use-applications such as those
described earlier can cause a large amount of data to be transported.
This can be larger than acceptable for constrained devices and
networks. Concise SWID tags significantly reduce the amount of data
transported as compared to a typical SWID tag. This reduction is
enable through the use of CBOR, which maps human-readable labels of
that content to more concise integer labels (indices). This allows
SWID tags to be part of an enterprise security solution for a wider
range of endpoints and environments.
2. Concise SWID data definition
The following is a CDDL representation of the ISO-19770-2:2015 [SWID]
XML schema definition of SWID tags. This representation includes all
SWID tag fields and thus supports all SWID tag use cases. The
CamelCase notation used in the XML schema definition is changed to
hyphen-separated notation (e.g. ResourceCollection is named
resource-collection in the Concise SWID data definition). The human-
readable names of members are mapped to integer indices via a block
of rules at the bottom of the Concise SWID data definition. The 48
character strings of the SWID vocabulary that would have to be stored
or transported in full if using the original vocabulary are replaced.
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software-identity = {
global-attr,
? content,
? corpus,
? patch,
? media,
name,
? supplemental,
tag-id,
? tag-version,
? version,
? version-scheme,
}
NMTOKEN = text ; .regexp to add some validation?
NMTOKENS = [* NMTOKEN]
any-attr = text
any-element = any
date-time = time
any-uri = uri
global-attr = (
* (text => any-attr),
? lang,
)
meta-type = (
global-attr,
* (text => any-attr),
)
meta-element = [
global-attr,
* (text => any-attr),
]
resource-collection = (
global-attr,
* (directory-entry // file-entry // process-entry // resource-entry)
)
file = {
filesystem-item,
? size,
? version,
* (text => any-attr),
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}
filesystem-item = (
meta-type,
? key,
? location,
name,
? root,
)
directory = {
filesystem-item,
path-elements,
}
process = {
global-attr,
name,
? pid,
}
resource = {
global-attr,
type,
}
entity = {
global-attr,
meta-elements,
name,
? reg-id,
role,
? thumbprint,
}
evidence = {
global-attr,
resource-collection,
? date,
? device-id,
}
link = {
global-attr,
? artifact,
href,
? media,
? ownership,
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rel,
? type,
? use,
}
software-meta = {
global-attr,
? activation-status,
? channel-type,
? colloquial-version,
? description,
? edition,
? entitlement-data-required,
? entitlement-key,
? generator,
? persistent-id,
? product,
? product-family,
? revision,
? summary,
? unspsc-code,
? unspsc-version,
}
payload = {
global-attr,
resource-collection,
}
tag-id = (0: text)
name = (1: text)
content = (
2: [ * entity / evidence / link / software-meta /
payload / any-element ]
)
corpus = (3: bool)
patch = (4: bool)
media = (5: text)
supplemental = (6: bool)
tag-version = (7: integer)
version = (8: text)
version-scheme = (9: NMTOKEN)
lang = (10: text)
directory-entry = (11: directory)
file-entry = (12: file)
process-entry = (13: process)
resource-entry = (14: resource)
size = (15: integer)
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key = (16: bool)
location = (17: text)
root = (18: text)
path-elements = (19: ([ * (directory / file) ]))
pid = (20: integer)
type = (21: text)
meta-elements = (22: ([ * meta-element ]))
reg-id = (23: any-uri)
role = (24: NMTOKENS)
thumbprint = (25: text)
date = (26: date-time)
device-id = (27: text)
artifact = (28: text)
href = (29: any-uri)
ownership = (30: ("shared" / "private" / "abandon"))
rel = (31: NMTOKEN)
use = (32: ("optional" / "required" / "recommended"))
activation-status = (33: text)
channel-type = (34: text)
colloquial-version = (35: text)
description = (36: text)
edition = (37: text)
entitlement-data-required = (38: bool)
entitlement-key = (39: text)
generator = (40: text)
persistent-id = (41: text)
product = (42: text)
product-family = (43: text)
revision = (44: text)
summary = (45: text)
unspsc-code = (46: text)
unspsc-version = (47: text)
3. COSE signatures for Concise SWID tags
SWID tags, as defined in the ISO-19770-2:2015 XML schema, can include
cryptographic signatures to protect the integrity of the SWID tag.
In general, tags are signed by the tag creator (typically, although
not exclusively, the vendor of the software product that the SWID tag
identifies). Cryptographic signatures can make any modification of
the tag detectable, which is especially important if the integrity of
the tag is important, such as when the tag is providing golden
measurements for files.
The ISO-19770-2:2015 XML schema uses XML DSIG to support
cryptographic signatures. Concise SWID tags require a different
signature scheme than this. COSE provides the required mechanism
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[I-D.ietf-cose-msg], which will be addressed in a future iteration of
this draft and most likely result in additional attributes to be
included in the general Concise SWID data definition, e.g. signature-
type ("compat", "cose", etc.). Note that, by their natures,
cryptographic signatures will not remain valid if a SWID tag is
translated from one representation to another.
4. IANA considerations
This document will include requests to IANA: Integer indices for SWID
content attributes and information elements.
5. Security Considerations
SWID tags contain public information about software products and, as
such, do not need to be protected against disclosure on an endpoint.
Similarly, SWID tags are intended to be easily discoverable by
applications and users on an endpoint in order to make it easy to
identify and collect all of an endpoint's SWID tags. As such, any
security considerations regarding SWID tags focus on the application
of SWID tags to address security challenges, and the possible
disclosure of the results of those applications.
A signed SWID tag whose signature is intact can be relied upon to be
unchanged since it was signed. If the SWID tag was created by the
software author, this generally means that it has undergone no change
since the software application with which the tag is associated was
installed. By implication, this means that the signed tag reflects
the software author's understanding of the details of that software
product. This can be useful assurance when the information in the
tag needs to be trusted, such as when the tag is being used to convey
golden measurements. By contrast, the data contained in unsigned
tags cannot be trusted to be unmodified.
SWID tags are designed to be easily added and removed from an
endpoint along with the installation or removal of software products.
On endpoints where addition or removal of software products is
tightly controlled, the addition or removal of SWID tags can be
similarly controlled. On more open systems, where many users can
manage the software inventory, SWID tags may be easier to add or
remove. On such systems, it may be possible to add or remove SWID
tags in a way that does not reflect the actual presence or absence of
corresponding software products. Similarly, not all software
products automatically install SWID tags, so products may be present
on an endpoint without providing a corresponding SWID tag. As such,
any collection of SWID tags cannot automatically be assumed to
represent either a complete or fully accurate representation of the
software inventory of the endpoint. However, especially on devices
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that more strictly control the ability to add or remove applications,
SWID tags are an easy way to provide an preliminary understanding of
that endpoint's software inventory.
Any report of an endpoint's SWID tag collection provides information
about the software inventory of that endpoint. If such a report is
exposed to an attacker, this can tell them which software products
and versions thereof are present on the endpoint. By examining this
list, the attacker might learn of the presence of applications that
are vulnerable to certain types of attacks. As noted earlier, SWID
tags are designed to be easily discoverable by an endpoint, but this
does not present a significant risk since an attacker would already
need to have access to the endpoint to view that information.
However, when the endpoint transmits its software inventory to
another party, or that inventory is stored on a server for later
analysis, this can potentially expose this information to attackers
who do not yet have access to the endpoint. As such, it is important
to protect the confidentiality of SWID tag information that has been
collected from an endpoint, not because those tags individually
contain sensitive information, but because the collection of SWID
tags and their association with an endpoint reveals information about
that endpoint's attack surface.
Finally, both the ISO-19770-2:2015 XML schema definition and the
Concise SWID data definition allow for the construction of "infinite"
SWID tags or SWID tags that contain malicious content with the intend
if creating non-deterministic states during validation or processing
of SWID tags. While software product vendors are unlikely to do
this, SWID tags can be created by any party and the SWID tags
collected from an endpoint could contain a mixture of vendor and non-
vendor created tags. For this reason, tools that consume SWID tags
ought to treat the tag contents as potentially malicious and should
employ input sanitizing on the tags they ingest.
6. Acknowledgements
7. Change Log
First version -00
8. Contributors
9. References
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9.1. Normative References
[I-D.ietf-cose-msg]
Schaad, J., "CBOR Encoded Message Syntax", draft-ietf-
cose-msg-10 (work in progress), February 2016.
[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
October 2013, <http://www.rfc-editor.org/info/rfc7049>.
[SAM] "Information technology - Software asset management - Part
5: Overview and vocabulary", ISO/IEC 19770-5:2013,
November 2013.
[SWID] "Information technology - Software asset management - Part
2: Software identification tag'", ISO/IEC 19770-2:2015,
October 2015.
[X.1520] "ITU-T X.1520 (01/2014)", n.d..
9.2. Informative References
[I-D-birkholz-tuda]
Fuchs, A., Birkholz, H., McDonald, I., and C. Bormann,
"Time-Based Uni-Directional Attestation", draft-birkholz-
tuda-01 (work in progress), March 2016.
[I-D.greevenbosch-appsawg-cbor-cddl]
Vigano, C. and H. Birkholz, "CBOR data definition language
(CDDL): a notational convention to express CBOR data
structures", draft-greevenbosch-appsawg-cbor-cddl-08 (work
in progress), March 2016.
Authors' Addresses
Henk Birkholz
Fraunhofer SIT
Rheinstrasse 75
Darmstadt 64295
Germany
Email: henk.birkholz@sit.fraunhofer.de
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Jessica Fitzgerald-McKay
Department of Defense
9800 Savage Road
Ft. Meade, Maryland
USA
Email: jmfitz2@nsa.gov
Charles Schmidt
The MITRE Corporation
202 Burlington Road
Bedford, Maryland 01730
USA
Email: cmschmidt@mitre.org
David Waltermire
National Institute of Standards and Technology
100 Bureau Drive
Gaithersburg, Maryland 20877
USA
Email: david.waltermire@nist.gov
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