PassWD2000 v2.x Weak Encryption Vulnerability

[Daniel Roethlisberger <daniel () roe ch>]

==[ PassWD2000 v2.x Weak Encryption Vulnerability ]===============


              "Success does not consist in never making mistakes
                  but in never making the same one a second time"
                                       --- George Bernard Shaw



Vulnerable:
        PassWD2000 2.0
        PassWD2000 2.1 (*)
        PassWD2000 2.2 (*)
        PassWD2000 2.3 (*)
        PassWD2000 2.4 (*)
        PassWD2000 2.5
        PassWD2000 2.6
        PassWD2000 2.7
        PassWD2000 2.8
         - Microsoft Windows 95
         - Microsoft Windows 98
         - Microsoft Windows NT 4.0
         - Microsoft Windows 2000
         - Microsoft Windows ME

        (*): Apparently never made it into a public release.

Not vulnerable:

Vendor:
        Giordano Bigarelli <info () passwd2000 com>
        http://www.passwd2000.com/


--[ Overview ]----------------------------------------------------

 PassWD2000 is a password managment utility designed to store
 login credentials to remote sites, local passwords or
 registration details, or even credit card information.

 Unfortunately, the vendors' understanding of encryption is a bit
 different from mine. PassWD2000 is using an "encryption"
 algorithm that is trivial to break, effectively giving an
 attacker access to all login information stored within
 PassWD2000 once he gains access to the password file.

 PassWD2000 has received the ZDNet Editors' Pick award and other
 share/freeware recommendations, and thus must be considered to
 be in widespread use.


--[ Déjà vu? ]----------------------------------------------------

 Think you heard all this before? Definately. Precisely one year
 ago, which is coincidence, I published a similar problem of
 predecessor PassWD v1.2; it used an even weaker "encryption"
 algorithm. For details refer to BID 1300 at:

 http://www.securityfocus.com/bid/1300


--[ Vendor Status ]-----------------------------------------------

 Vendor is informed, and has decided to do nothing about this
 issue. According to vendor, PassWD2000 never claimed so use
 strong encryption, only "quite strong encryption". So there will
 be no fix in versions 2.x. Subsequently, the vendor decided not
 to inform about the issue, neither users nor distribution sites
 of PassWD2000 are going to be informed by the vendor.


--[ Solution ]----------------------------------------------------

 Don't use PassWD2000 2.x, and make sure none of your users or
 admins do either. Period. According to the vendor, the upcoming
 3.x release of PassWD2000 will use Blowfish to protect the data.


--[ Technical Details ]-------------------------------------------

 PassWD2000 stores all login credentials along with the access
 password and a bunch of other things in .PEF files. PEF stands
 for PassWD Encrypted Format.

 Basically it uses a simple exclusive or with a 128 bit key. It
 randomly generates a 128 bit session key, which is used to
 encrypt the header and data of the PEF file. It stores this
 session key xored to a fixed master key in front of the
 encrypted header within the PEF file.

 So what you do is xor the fixed master key with the first 128
 bits of the file to reveal the session key. Then use the session
 key to decrypt the header and data of the file. Only pitfall to
 avoid is that header and data are encrypted seperately (reset
 key offset).


--[ Proof of Concept ]--------------------------------------------

 I've written the decoder for PassWD2000 v2.x PEF files. It has
 grown with my knowledge of the file format, thus is very ugly
 code indeed, and probably unportable (compiles with gcc-2.95.2).
 It should illustrate how to decode a PEF file though.


--[ Afterword ]---------------------------------------------------

 If you copy this text or reuse any part of it, please give due
 credit (and let me know about it).

 Copyright (C) 2001 by Daniel Roethlisberger <daniel () roe ch>.

Attachment: pefdump.c
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