VERISIGN "PAYFLOW LINK" PAYMENT SERVICE SECURITY FAILURE

[keith royster <keith () theroysters com>]

VERISIGN PAYFLOW PAYMENT SERVICE SECURITY FAILURE 

PAYFLOW LINK SERVICE DESCRIPTION: The final checkout page of various online 
shopping cart applications presents the shopper with a form asking for credit 
card acct#, exp date, etc.  When the shopper submits the form, the data is sent 
directly to the vendor's PayFlow Link account at Verisign for validation.  If 
the credit card information is validated, Verisign authorizes payment and 
submits the data back to the vendors shopping cart application.  When the 
vendor's shopping app receives this data, it assumes payment was authorized and 
finalizes the order for the vendor to fill and ship it. 

EXPLOIT #1: On the final checkout page, save the HTML to disk (keeping browser 
open to maintain session) and edit the ACTION= portion of the form to direct 
the data back at the shopping cart instead of to verisign.  The exact URL 
should match that which verisign would submit a validated order to.  Save the 
edited HTML, reload in your browser, and submit bogus credit card info with 
your order. Since there is no authentication between Verisign and the shopping 
application, the shopping app will think that the card was authorized, and so 
it will finalize the order. 

EXPLOIT #2: Sign up for a free demo PayFlow Link account at Verisign.  While in 
demo mode, this account will "validate" almost any credit card info submitted 
to it as long as the card# meets basic format, expiration date hasn't expired, 
and amount <= $100.  This demo account should be configured to send the 
confirmation information to the exploitee's shopping system.  Then perform a 
similar HTML edit of the final checkout page as above, only this time change 
the hidden form tag to direct the payment to the demo PayFlow Link account. 
Save the HTML, reload in your browser, and submit bogus credit card info. 

THE RISK: Vendors that do no validate payment in their Verisign acct prior to 
shipment, or those that offer immediate downloads of software upon payment, are 
vulnerable to theft. 

THE FIX: In a communication from Verisign, they recommend upgrading to their 
more secure PayFlow Pro product if you have security concerns with PayFlow Link.

WHAT I KNOW:  I have successfully performed both exploits on a Miva Merchant 
3.x shopping cart.  Due to a lack of accessability, I have not tested other 
shopping cart applications or other versions of Miva Merchant.  I have 
communicated this information to both Miva and Verisign.  Verisign tested and 
confirmed both exploits as well.  They then responded that they will work with 
Miva to work towards better security, although they did not offer any 
timelines.  They did not mention working with other vendors of other shopping 
carts, nor did they admit the problem exists with other shopping cart apps.  
Their only current solution is to educate their customers regarding the risks 
and encourage them to upgrade to the more secure (and costly) PayFlow Pro 
product. 

WHAT I DON'T KNOW: I don't know what other shopping cart applications (if any, 
besides Miva's) are vulnerable.  But I am highly suspicious that others are 
because the problem seems to be that the PayFlow Link app does not offer any 
credentials so that the receiving shopping cart app can validate the source of 
the data.  I also have not verified any other version of Miva Merchant besides 
3.x. Merchant 4.x is the most current version, but I think it uses the same 
PayFlow Link module and so it should be vulnerable as well. I would be 
interested in working with others that have access to other shopping cart apps 
that can interface with PayFlow Link. 

PS - my first post to bugtraq, so I hope I did it right.  Please let me know if 
I've left anything off.

-- 
keith royster
keith () theroysters com