Internet DRAFT - draft-daisuke-iodef-experiment
draft-daisuke-iodef-experiment
MILE Working Group D. Miyamoto
Internet-Draft UTokyo
Intended status: Experimental T. Takahashi
Expires: August 16, 2014 NICT
February 12, 2014
Knowledge obtained from the implementation experience of an IODEF-
capable incident response management system
draft-daisuke-iodef-experiment-00.txt
Abstract
This document explains our observation on the usability of IODEF
[RFC5070], based on our experiments. We aim at developing an IODEF-
capable incident response management systems in order to facilitate
incident response activities. We started to design and implement the
system for our university CERT, however, there are several technical
issues while implementing and operating the system. This document
shares the observation from our proto-type implementation and
provides new sight from operational aspects.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Implementation . . . . . . . . . . . . . . . . . . . . . . . 3
4. Operational Issues . . . . . . . . . . . . . . . . . . . . . 4
4.1. type attribute @ Impact class . . . . . . . . . . . . . . 5
4.2. category attribute @ NodeRole Class . . . . . . . . . . . 5
4.3. action attribute @ Expectation Class . . . . . . . . . . 5
4.4. Potential information leakage . . . . . . . . . . . . . . 5
4.5. Configuration of Nodes . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 6
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1. Normative References . . . . . . . . . . . . . . . . . . 6
9.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
The number of incidents in cyber society is growing day by day.
Incident information needs to be reported, exchanged, and shared
among organizations in order to cope with the situation. IODEF
provides a scheme to describe and exchange incident response
information among interested parties.
For our university CERT, we decided to introduce an IODEF-capable
incident response management system to facilitate incident response
activities. Our university has two types of CERT, namely, a central
CERT and divisional CERTs. The former is a contact point for
external organizations, and the latter is a CERT for each division in
the university. When the central CERT receives such information, it
notifies the information to the corresponding divisional CERT who has
an accountability for decision and actions.
Our old system employed emails for exchanging the information between
the central and divisional CERTS, however, we started to employ
machine-readable message in regard to the growing demand for
automated incident response systems. For doing so, we attempted to
implement an IODEF-capable incident response management system.
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In our implementation, we encountered problems while dealing with XML
schema. To save the development cost, we employed code generators
that build class libraries for accessing values in IODEF elements.
Due to the complexity of IODEF message format defined in [RFC5070],
some code generators could not understand its schema.
We also found some operational problems as well as the implementation
problem. Most of the problems were on the choice of values for IODEF
attributes and/or elemens.
This draft provides how we evade the implementation problem, and
explores the suitable value for XML element in regard to the
incidents.
2. Terminology
The terminology used in this document follows the one defined in
[RFC5070].
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].
3. Implementation
Since a code generator for XSD automatically develops useful
libraries for accessing XML attributes and/or composing messages, we
tested following generators to build the libraries from RFC 5070
[RFC5070] .
o XML::Pastor [XSD:Perl] (Perl)
o RXSD [XSD:Ruby] (Ruby)
o PyXB [XSD:Python] (Python)
o JAXB [XSD:Java] (Java)
o CodeSynthesis XSD [XSD:Cxx] (C++)
o Xsd.exe [XSD:CS] (C#)
We thought we can use them to generate IODEF, but they cannot be
easily used. For instance, we have used XML::Pastor, but it could
not properly understand its schema due to the complexity of IODEF
XSD. The same applies to RXSD and JAXB. Only PyXB, CodeSynthesis
XSD and Xsd.exe were able to understand the schema.
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To cope with the situation, we have made a trick, which is not
recommended, but is one option to go through the situation. That is,
"XSD2XML2XSD", which means that XSD is converted to XML, and it is
again converted to XSD. The resultant XSD was process-able by the
all tools above.
Nevertheless, the generated module was unworkable. This is due to
the fact that IODEF uses '-' (hyphen) symbols in its classes or
attributes, listed as follows.
o IODEF-Document Class; it is the top level class in the IODEF data
model described in section 3.1 of [RFC5070].
o The vlan-name and vlan-num Attribute; according to section 3.16.2
of [RFC5070], they are the name and number of Virtual LAN and are
the attributes for Address class.
o Extending the Enumerated Values of Attribute; according to section
5.1 of [RFC5070], it is a extension techniques to add new
enumerated values to an attribute, and has a prefix of "ext-",
e.g., ext-value, ext-category, ext-type, and so on.
According to the language specification, Perl classes and/or
functions could not contain '-' symbols in their names. We replaced
hyphens with '_' (underscore) symbols to evade this issue. Before
outputting an IODEF format message, our system must manually replace
these renamed characters in its serialization process.
Aside from the case of Perl, other language tend to evade using any
hyphens in its name space. PyXB and CodeSynthesis XSD automatically
replaced hyphen with underscore symbols, and JAXB and Xsd.exe simply
removed hyphens. These tools also might output an exact IODEF
message format through their serialization process. RXSD was similar
to JAXB and Xsd.exe, replaced with hyphens automatically, but did not
support converting the renamed characters for outputting.
4. Operational Issues
This section explains some pitfalls while assigning values for IODEF-
based XML elements. Mainly, our central CERT notifies the incident
information to the issued divisional CERT, and the divisional CERT
reports the results of forensics. Based on this situation, we found
several cases that we were not sure about which attributes should be
chosen.
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4.1. type attribute @ Impact class
Various incident classification exist. For instance, JPCERT proposes
the following classification: phishing site, page hijack, malware
propagation, scan, DoS/DDoS, and control systems. Nevertheless, it
is hard to fit them into the type attribute of theimpact class.
For example, phishing site, scan, and DoS/DDoS might be mapped as
"social-engineering", "recon", and "dos" attributes in respectively.
In the rest of cases, what the type of the attribute should we
choose?
4.2. category attribute @ NodeRole Class
IODEF has category attribute for NodeRole class. Though various
categories are described, they are not enough. For instance, we
sometime report the category of "proxy server" in our daily CERT
operation, but which one am we supposed to choose? How about web
mail? Should we choose "www"? or "mail"?
4.3. action attribute @ Expectation Class
Assuming if the notifier sends a message with expecting to forensic
for the issues, and the reporter answers the result of their
forensics. In such cases, the notifiers would choose
"investigation", but what types of action attribute should the
reporter choose? Should the reporter choose "nothing" ?
When a notifier sends IODEF document, the report wishes to confirm it
without asking any further actions. Then what values shall we
choose?
4.4. Potential information leakage
The numbering of Incident ID needs to be considered. Otherwise,
information, such as the number of incidents within certain period
could be observed by document receivers. For instance, we could
randomize the assignment of the numbers.
4.5. Configuration of Nodes
Node class can describe various information of the system, but the
level of information granularity there is not defined. It could be
that very detailed information is needed, or it could be the
opposite. It has the field of the software id and configid, but the
formats for them are not specifically defined.
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It is natural to guess that we cannot define single, common level of
information granularity. Depending on situation and operation, the
needed level of information granularity differs.
Thus one approach is using IODEF-SCI, which can choose arbitrary
schema to describe the details of such information.
5. Security Considerations
This document raises no security issues itself. The potential
security issues are the vulnerabilities in the class libraries
constructed by code generators.
6. IANA Considerations
This document contains no considerations for IANA.
7. Conclusions
The document explains the implemetation issue, the problems raised
from code generation, and the operational issue, the problems while
choosing the value in XML elements for IODEF format messages.
8. Acknowledgements
Many thanks for feedback from Tomohiro Ishihara for his comments.
This work is materially supported by the Ministry of Internal Affairs
and Communication, Japan, and by the European Union Seventh Framework
Programme (FP7/2007-2013) under grant agreement No. 608533 (NECOMA).
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5070] Danyliw, R., Meijer, J., and Y. Demchenko, "The Incident
Object Description Exchange Format", RFC 5070, December
2007.
9.2. Informative References
[XSD:Perl]
Ulsoy, A., "XML::Pastor",
<http://search.cpan.org/~aulusoy/XML-Pastor-1.0.4/>.
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[XSD:Ruby]
Morsi, M., "RXSD - XSD / Ruby Translator", <https://
github.com/movitto/RXSD>.
[XSD:Python]
Bigot, P., "PyXB: Python XML Schema Bindings", <https://
pypi.python.org/pypi/PyXB>.
[XSD:Java]
Project Kenai, "JAXB Reference Implementation", <https://
jaxb.java.net/>.
[XSD:Cxx] CodeSynthesis, "XSD - XML Data Binding for C++",
<http://www.codesynthesis.com/>.
[XSD:CS] Microsoft, "XML Schema Definition Tool (Xsd.exe)",
<http://www.codesynthesis.com/>.
Authors' Addresses
Daisuke Miyamoto
The University of Tokyo
2-11-16 Yayoi Bunkyo-Ku
113-8658 Tokyo
Japan
Phone: +80 3 5841 0836
Email: daisu-mi@nc.u-tokyo.ac.jp
Takeshi Takahashi
National Institute of Information and Communications Technology
4-2-1 Nukui-Kitamachi Koganei
184-8795 Tokyo
Japan
Phone: +80 423 27 5862
Email: takeshi_takahashi@nict.go.jp
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