Date: Thu Mar  2 02:22:20 2006
From: bugtraq at securescience.net (Lance James)
Subject: Re: Fedex Kinkos Smart Card Authentication Bypass

Lance James wrote:
> Eric B wrote:
>   
>> Wait, so if I read this right, consumers with existing cards could
>> dupe their legit cards for fake ones and cash in the fake ones yet
>> still have credit on the legit card?
>>
>> So I'm assuming Fedex has no database/authentication system storing
>> these serials...brilliant.
>>
>>     
>
> Yup.
>
> According to Fedex Kinko's:
> "Our analysis shows that the information in the article is inaccurate
> and not based on the way the actual technology and security function.
> Security is a priority to FedEx Kinko's, and we are confident in the
> security of our network in preventing such illegal activity."
>
> Our response:
>
> http://ip.securescience.net/exploits/P1010029.JPG
>   

Following up with a video for skeptics

http://www.securescience.net/exploits/ssc_expresspay_vuln.wmv

Thanks.
>
>   
>> Good write-up, thanks!
>>
>> On 2/28/06, *Lance James* <bugtraq@...urescience.net
>> <mailto:bugtraq@...urescience.net>> wrote:
>>
>>     Abstract:
>>     ---------
>>     The ExpressPay stored-value card system used by FedEx Kinko's is
>>     vulnerable to attack.  An attacker who gains the ability to alter the
>>     data stored on the card can use FedEx Kinko's services fraudulently
>>     and anonymously, and can even obtain cash from the store.
>>
>>
>>     Description:
>>     ------------
>>     The FedEx Kinko's ExpressPay system, developed by enTrac Technologies
>>     of Toronto, Ontario, is based on a Siemens / Infineon SLE4442 memory
>>     chip card.  The data stored on this card is freely rewritable once a
>>     three-byte security code has been presented to the card's security
>>     logic.  Neither this security code nor the data stored on the card is
>>     encrypted; anyone able to obtain the security code is free to rewrite
>>     the data stored on the card using an inexpensive commercially
>>     available smart card reader/writer.
>>
>>     The first thirty-two bytes of the memory chip card are writable and
>>     subsequently permanently write-protectable (in this application,
>>     these
>>     bytes are write-protected), and contain a header which identifies the
>>     card as an ExpressPay stored-value card.  Bytes 0x20 through 0x27
>>     contain the value stored on the card, represented in IEEE 754
>>     double-precision floating point format.  Bytes 0x60 through 0x6A
>>     contain the card's eleven-digit serial number stored as unsigned
>>     zoned-decimal ASCII; digits 0x60 through 0x63 are the store number the
>>     card was initially issued at, and the remaining seven digits are
>>     assigned sequentially at the moment of first issue.  A timestamp
>>     indicating date and time of issue are located from 0x30 through 0x37,
>>     and is repeated from 0xC7 through 0xCE.
>>
>>     In order to write to the card, a three-byte security code must be
>>     presented in a specific sequence of commands as outlined by the
>>     SLE4442's white paper.  By soldering wires to the contact points of
>>     the card and then connecting those wires to an inexpensive logic
>>     analyzer, an attacker can sniff the three-byte code as the kiosk or a
>>     card terminal prepares to write data to the card.  This security code
>>     appears to be the same across all FedEx Kinko's ExpressPay cards
>>     currently in circulation.
>>
>>     Once the three-byte code is known to the attacker, the card's stored
>>     value and serial number can be changed to any value.  The ExpressPay
>>     system appears to implicitly trust the value stored on the card,
>>     regardless of what that value actually is.  The system will also
>>     accept cards with obviously fake serial numbers (e.g. a non-existent
>>     store number followed by all nines).  Using these altered cards,
>>     xeroxes can be made from any machine with a card reader, and computers
>>     can be rented anonymously and indefinitely.  Most disturbing, however,
>>     is that since stored-value cards can be cashed out by an employee at
>>     the register at any time, an attacker could cash out altered cards
>>     obtained at little or no monetary cost.  If a card is cashed out, its
>>     serial number does not appear to be invalidated in the system.  If an
>>     attacker were to clone a known good card and cash it out, the clone
>>     would still be usable.
>>
>>
>>     Tested Vendors:
>>     ---------------
>>     - FedEx Kinko's
>>
>>
>>     Suspected Vendors:
>>     ------------------
>>     - Any client of enTrac Technologies who uses the ExpressPay
>>     stored-value card system.
>>     - Any company which uses a stored-value card system based on the
>>     SLE4442
>>
>>
>>     Vendor and Patch Information:
>>     -----------------------------
>>     Proof-of-concept of the initial security vulnerability was
>>     achieved on
>>     8 February 2006, with research into the ramifications continuing
>>     through 12 February.  Copies of this report were sent to both FedEx
>>     Kinko's and enTrac Technologies on 15 February; a read receipt was
>>     returned from enTrac on 19 February, while no receipt has yet been
>>     received from FedEx Kinko's.
>>
>>
>>     Solution:
>>     ---------
>>     - Encrypt data before storing it on the SLE4442 card, or migrate to a
>>     system which uses cards which have built-in encryption functionality.
>>     - Verify that the stored value on the card does not significantly
>>     differ from a reference value stored in a database.
>>     - Do not allow the use of cards with invalid serial numbers.
>>     - Invalidate serial numbers of cards that are cashed out.
>>
>>
>>     Credits:
>>     --------
>>     Strom Carlson, Secure Science Corporation: Hardware Security Division
>>     stromc@...urescience.net <mailto:stromc@...urescience.net>
>>
>>
>>     
>
>
>   

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