Message-Id: <7.0.1.0.0.20060913221437.04755008@theworld.com>
Date: Wed, 13 Sep 2006 22:22:05 -0400
From: Vin McLellan <vin@...world.com>
To: full-disclosure@...ts.grok.org.uk
Subject: Re: RSA SecurID SID800 Token vulnerable by design


On FD, and in several other security forums, Hadmut Danisch 
<hadmut@...isch.de>, a respected German information security analyst, 
recently published a harsh critique of one optional feature in the 
SID800, one of the newest of the six SecurID authentication tokens -- 
some with slightly different form-factors, others with additional 
security functions -- sold by RSA Security, Inc.  It's raised quite a 
stir, and I'd like to respond.

A personal authentication token, by classical definition, must be 
physical, personal, and difficult to counterfeit.  The most popular 
implementations in computer security move the calculation of a 
pseudo-random authentication code -- a so-called "One-Time Password," 
or OTP-- off an employee's PC and into a hand-held hardware fob, 
small enough to be attached to a personal key chain.

RSA's mainstay token, the SID700 SecurID -- millions of which are 
used in over 20,000 enterprise installations worldwide, including 
many government agencies and financial institutions -- use AES (the 
US cryptographic standard) to process Current Time and a 128-bit 
token-specific secret to generate and continuously display a series 
of 6-8 digit (or alphanumeric) OTP "token-codes" which change every 
60-seconds, and remain valid only for a couple of minutes.

In practice, a RSA authentication server can then independently 
calculate the token-code that is appearing on a specific SecurID at 
this particular moment; compare that against an OTP submitted by a 
pre-registered user, and validate a match.  RSA, which first 
introduced the SecurID in 1987, has always insisted on the necessity 
of "two-factor authentication" (2FA), where a remote RSA 
authentication server must validate both a SecurID token-code 
(evidence of "something held") and a user-memorized PIN or password 
("something known.")

A stolen password can be reused indefinitely to masquerade as the 
legitimate user, often with the victim wholly unaware. A 
token-generated OTP, valid only briefly, is a far more robust 
authenticator.  With 2FA, if a SecurID is stolen or lost, it still 
can't be used to obtain illicit access to protected resources without 
the second secret: the user's memorized PIN or password.

The elegant simplicity of the traditional SecurID -- and patents on 
the mechanism by which the "drift" in each individual SecurID's 
internal clock is tracked by the RSA authentication server -- has 
allowed RSA's "time-synched" SecurID to dominate the market niche for 
hand-held OTP authentication devices for 20 years.

In a typical installation, anyone seeking to log on to a protected PC 
or network, or to access restricted online resources, must manually 
type in the OTP currently displayed on the SecurID -- as well as his 
memorized PIN or password -- to have his identity and access 
privileges validated. Network applications handle the combined 
SecurID "pass-code" like any long traditional password. The link 
between the user and the RSA infrastructure is often, but not always, 
an encrypted VPN channel. That's a local decision. Data exchanges 
between the RSA agent  and RSA authentication server -- which 
typically means between one of the 350-odd "SecurID-aware" network 
applications and the RSA Authentication Manager, using RSA's own 
protocol -- are always fully encrypted.

Mr. Danisch is an admirer of the classic SecurID (SID700), RSA's 
traditional hand-held token. His ire is directed at one of the two 
new hybrid SecurID designs that RSA has recently offered in an 
attempt to respond to new requirements in the boisterous and 
rapidly-evolving market for what's called "strong authentication."

With the nascent prospect of a new billion-dollar market in consumer 
authentication for financial services boosted by US federal 
regulatory initiatives, RSA announced the SecurID Signing Token, the 
SID900. The SecurID Signing Token still has a time-synched OTP, but 
RSA added a keypad and a challenge/response function which 
successively authenticates the user, the remote server, and a 
specific financial transaction, before the transaction (e.g., a funds 
transfer) is executed.

On the other side of the market -- where again US laws and federal 
regulatory initiatives have boosted demand for internal controls and 
more accountability measures in enterprise IT -- RSA has introduced 
the SID800, another hybrid SecurID, to meet the requirements of 
organizations that want to move into a full public key infrastructure (PKI.)

The SID800 SecurID is a multi-function authentication and 
cryptographic device that combines, in a single DPA-resistant token, 
the mobility and availability of the classic hand-held SecurID, as 
well as a "smart chip" that implements v2.1.1 Java tech (essentially 
a "virtual smart card") in a USB format. It looks like a slightly 
smaller version of the classic SecurID key fob, with a USB plug 
jutting out at one end. It can carry up to seven X.509 digital 
certificates for PKI, as well as account information and complex 
passwords for up to three Windows accounts. The SID800's lithium 
battery allows it to continuously generate and display 60-second 
SecurID OTPs for up to five years.

The SID800 "smart chip" has the typical load of standards-compliant 
smart card functionality: ANSI X9.31 PRNG, client-side PKI support 
including key generation for DES/3DES and 1024-bit RSA Public Key 
Cryptography, SHA-1 hashing, and 1024-bit RSA digital signatures.To 
access its local cryptographic services (key generation, 
authentication, file encryption, digital signatures, etc.) and its 
X.509 certificates -- complex resources that require a 
circuit-to-circuit connection and interactive data exchanges --  the 
SID800 SecurID can be plugged directly into a PC's USB port.

None of these features -- none of the SID800's cryptographic 
resources -- were of apparent interest to Mr. Danisch. He ignored 
them all when he denounced the SID800 as "vulnerable by design."

The classic SecurID, declared Mr. Danisch on the Cryptography mailing 
list, "is a smart device which provides a reasonable level of 
security in a very simple and almost foolproof way...."

"It's a pity," he added, "to see it weakened without need..." The 
traditional SecurID has the advantages (and disadvantages) of an "air 
gap." With no direct circuit connection to the user's PC or client 
terminal, it has no direct vulnerability to the various classes of 
malicious or larcenous malware which -- Mr. Danisch warns -- can 
potentially overwhelm and totally corrupt PCs, and particularly Windows PCs.

What particularly disturbs Mr. D is one option among in the SID800 
SecurID features which allows RSA's local client software to poll and 
retrieve a single OTP from the token when the SID800 is plugged into 
the PC's USB port.  Given the potential for malicious malware to 
invade and take control of any Windows PC -- malware that can seize 
and misuse both the user's PIN and an OTP fresh from the USB bus -- 
it was irresponsible, Danisch suggests, for RSA to make such a option 
available to its customers.

There are actually two versions of the SID800 sold by RSA.  In one 
version, there is none of the fancy new OTP functionality that 
worries Mr. D.  In this model, the only way to use the SecurID's OTP 
is the old-fashioned way: to read the LCD and type it (and the user's 
PIN) at the keyboard.

In the second version of the SID800 -- an option selectable by local 
management pre-purchase, and burnt into the token's USB firmware by 
RSA -- the user can select a menu in which he instructs the SecurID 
to load one OTP token-code directly into the paste buffer, presumably 
for immediate use. Since internal access to the SecurID's OTP via the 
USB bus makes it a potential target for "malware or intruders on the 
computer," claimed Mr. Danisch, "This is weak by design."  I beg to 
differ. Effective IT security is about an appropriate balance, not 
walls of iron or stone.

Can this token-code in the paste buffer be misused? Not likely, even 
if it is immediately stolen by malware and immediately used for some 
nefarious purpose.  A SecurID token-code can only be used once; no 
replay is allowed.  As a defense against race attacks, the RSA 
Authentication Manager will also automatically reject both of two 
identical token-codes submitted roughly simultaneously -- even if 
both are accompanied by the proper PIN -- and log it for 
investigation by the security manager. If the legitimate user can use 
the token-code, he effectively preempts any misuse of that OTP by a 
hostile party or malware.

Could hostile malware independently execute the menu request for a 
new token-code -- essentially instruct a token plugged into the USB 
port to produce a new token-code, without the knowledge of the user 
-- and then swipe it, directly or from the paste buffer? Could 
malware collect the PIN and logon data of any authentication process 
with a keyboard logger? Unfortunately, it could.  Mr. Danisch raises 
a valid concern.

The cryptographic functionality of any smart card -- which typically 
includes authentication, encryption, digital signatures, etc. -- can 
be initialized and misused by a powerful hostile agent which took 
control of the user's PC and snatched the user's password.  Just as 
-- although Mr. Danisch didn't mention this -- the "virtual smart 
card" in the SID800, or any similar UBB device, could be initialized 
and misused.

The level of malware penetration that Mr. D presumes could corrupt 
the client authentication and cryptographic functions in any 
contemporary PKI environment, certainly any Windows-based client-side 
SSL. (See: "Keyjacking: the surprising insecurity of client-side 
SSL," by Marchesini, Smith, and Zhao at 
<http://www.cs.dartmouth.edu/~sws/pubs/msz05.pdf>.)

Mr. Danisch denounces RSA for implementing an optional ease-of-use 
feature, just because it effectively reduces the implicit security of 
OTP authentication to no more than what is provided by any PKI smart 
card environment. Some -- but not necessarily me -- might suggest 
that this is carrying an appreciation of the unique and sterling 
qualities of the classic SecurID's OTP a bit far.

This has been an ongoing debate within the RSA user community for the 
past year, where some of the language used in declaring opinions is 
not always as civil or restrained as that used by Mr. Danisch.  It is 
not yet clear how the market's choices and concerns will affect the 
next version of the SID800's firmware, expected later this year -- 
but it seems unlikely that either of the two SID800 versions will be 
removed from RSA's sales list.

In security, ease-of-use (which usually implies internal complexity) 
is often the enemy of security. Yet, any enhancement in ease-of-use 
which will have little or no impact on overall system security is 
something of a Holy Grail for both InfoSec vendors and local IT managers.

Some organizations choose to use SID800 SecurIDs which offer RSA's 
"OTP paste" feature, others do not. Those who don't are presumably 
acting on the basis of a risk analysis of their environment that 
determines that the advantages of enhanced usability do not justify 
the risks it entails.  Many of those, I presume, have concerns 
similar to those of Mr. Danisch.

If the hostile malware can wait and capture the initiation password 
off the keyboard, it can ask for anything the password can authorize. 
 From the SID800. From any smart card. From any application. From any 
network resource. This is not a new insight.  (Ironically, the 
SID800's OTP output to the USB bus is relatively more difficult to 
misuse, since it is time-constrained, while stolen smart card 
functionality typically is not.)

Obviously, if a hostile enemy can load malware that "owns" your PCs, 
untrustworthy user authentication is only the beginning of your problems.

If the enemy "owns" your Windows box today -- or any other computer, 
for that matter -- he probably totally controls everything that 
passes through it, and all devices connected to it.  Although the 
firmware in a smart card -- or in USB plugs like the SID800 which 
offer "virtual smart cards" -- supposedly won't allow the PC to 
directly access the token's internal secrets, a computer under the 
control of a hostile party can doubtless gain illicit access to the 
cryptographic services provided by those devices.

Assuming imperfect defenses in any given technical context -- 
certainly true with the current Microsoft Windows OS, the leading 
browsers, and the protocols now in use for both secure data transfer 
and authentication -- the industry consensus calls for multiple 
defensive layers. Where one defensive layer leaves a gap, another 
will often overlap to cover it. The logic of such an approach is 
based on gritty experience: there is no such thing a perfect security!

Mr. Danisch bemoans -- as do other fretful traditionalists like 
myself, including many who work for RSA -- the loss of the "air gap," 
the isolation of the SecurID's OTP generation from the potentially 
corrupted PC and network.  (A networked device will never be as 
transparent as the classic OTP token, where everybody knows exactly 
what the SecurID is doing, and can be certain that it is doing no 
more than it is expected to do. The elegance of simplicity.)

Others -- including many fretful traditionalists -- celebrate 
(despite imperfect implementations, despite many inherently 
untrustworthy operational environments) the powerful security 
utilities which become available with interactive PKI, which RSA 
pioneered with its work on the seminal Public Key Crypto Standards 
(PKCS) and the revolutionary RSA public key cipher which is critical 
to so much of today's network security services.

The two hardest things to do in computer security are (A) to create a 
perfectly secure technical infrastructure, and (B) to second-guess 
the CIO, CISO, or local system administrator who has the 
responsibility to identify his assets, understand his risks, and 
select where and how to balance his investments in usable 
functionality and information security.

Since no one today argues that perfect security is attainable, 
security mavens like Mr. Danisch (and myself) are forever occupied 
with the second task. Yet, as Courtney's First Law -- codified 40 
years ago by IBM's Bob Courtney, one of the pioneers in computer 
security -- puts it: "Nothing useful can be said about the security 
of a mechanism except in the context of a specific application and a 
specific environment."

Information security vendors like RSA attempt to respond to the 
perceived market requirements, juggling concerns about risk, 
liability, and cost against demands for functionality, flexibility, 
and accessibility.  When relative security is slightly compromised 
for a perhaps critical enhancement in ease-of-use, it seems smart to 
at least give the buyers the option.  That leaves the critical 
judgment to the professionals who know their environment, their real 
risks, and their people, best.

Lecturing CIOs about the relative importance of security threats -- 
when they have to get real work done in an imperfect universe -- is 
as presumptuous as it is almost surely ill-informed.  Hectoring 
vendors who respond to demands from their customers for alternative 
ways to address security issues -- some admittedly more or less 
robust than others -- is far more appropriate. In that sense, debates 
that arise when critics like Mr. Danisch forcefully state their case 
are useful, even necessary.

It is no secret that Windows and the browsers have design 
flaws.  Client-side SSL still has some major architectural issues, 
particularly in Windows. It is no secret that PC users today need a 
safer place -- some sort of restricted input environment, 
inaccessible to all but the local user -- by which they can submit 
authentication calls to an application over a trusted path. It is no 
secret that network protocols require new IETF initiatives to better 
secure them against attempts to corrupt them for illicit gain. It is 
no secret that simple authentication protocols must today often be 
supplemented by some form of mutual authentication, or that 
high-value transactions may require supplementary authentication, or 
that unusual transactions or access claims may trigger direct 
oversight or adaptive authentication requirements.

Simple user authentication, simple web server authentication, simple 
client-side SSL, basic PKI, is no longer enough when malware is now 
usually the sophisticated product of a criminal enterprise. Forensic 
audit logs have never been more important. The good news is that -- 
thanks to concerns raised by outspoken techies like Hadmut Danisch -- 
there is public debate and significant developments in all these 
areas, and solutions (probably imperfect, but better) are on the horizon.

Suerte,
            _Vin

PS. I have been a consultant to RSA for nearly 20 years and my bias 
is overt. I beg the indulgence of the List for the length of my comments.



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