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 > Good write-up, thanks! > > On 2/28/06, *Lance James* <bugtraq@xxxxxxxxxxxxxxxxx > <mailto:bugtraq@xxxxxxxxxxxxxxxxx>> 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@xxxxxxxxxxxxxxxxx <mailto:stromc@xxxxxxxxxxxxxxxxx> > >
