RE: Vuln in Verisign PayFlow Link payment service

[Erwin Geirnaert <egeirnaert () reference be>]

I think the solution is very easy.
Don't post from the browser to Verisign, but to the server that will forward
the request to Verisign and then back to the browser. In that way the server
controls everything and the client is unable to change the outcome.

Check www.owasp.org for more info on these matters. 

Kind regards.

Erwin

-----Original Message-----
From: Megan McRee [mailto:meganmc () mail ru]
Sent: vrijdag 4 januari 2002 1:12
To: vuln-dev () securityfocus com
Subject: Re: Vuln in Verisign PayFlow Link payment service


I hate to see this post. From a developer's perspective, this is one of the
easiest and most flexible card processing systems to integrate with my
software that I have
found.

Perhaps a fix for VeriSign would be to passback a secret code (configurable
through the PayFlow Link admin panel) that does not originate from a cart
input value, but is stored and sent from PayFlow. Then a simple 'if'
statement in the cart software could weed out the bad along with an e-mail
sent to the admin. That would surely slow someone down if they have to guess
the secret code's input value.

I would hate to see them change the way the current system of passing back
values works. Does anyone know of any other card processing services that
pass back variables to software/scripts in the same manner?



----- Original Message -----
From: Keith Royster <keith () theroysters com>
To: <vuln-dev () securityfocus com>
Sent: Thursday, January 03, 2002 5:39 PM
Subject: Vuln in Verisign PayFlow Link payment service


> Hello!  I'm very new to this list and am looking for advice on how and
where
> to properly post information regarding a vulnerability I have identified
> with Verisign's PayFlow Link credit card payment service.  I would
> ultimately like for this information to get into the Vuln Database at
> BugTraq, but do not know the proper procedures and requirements for
getting
> it there. Below is a brief(?) description of the service and the
exploit...
> THE SERVICE: 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 if 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 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.  This 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 your 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.
>
> WHAT I KNOW:  I have successfully performed both exploits on a Miva
Merchant
> 3.x shopping cart.  I have not had the opportunity to test other shopping
> cart applications or other versions of Merchant.  I have communicated this
> information to both Miva and Verisign.  Verisign tested and confirmed both
> exploits as well.  They then responded that they do not intend to fix it -
> that instead they will 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.  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's PayFlow
Link
> module is the same 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.
>
> TIA!