Caja PDF

Comparta fácilmente sus documentos PDF con sus contactos, la web y las redes sociales.

Compartir un archivo PDF Gestor de archivos Caja de instrumento Buscar PDF Ayuda Contáctenos



Passcape Software .pdf



Nombre del archivo original: Passcape Software.pdf
Título: Vulnerability of DPAPI data protection in Win2K, Win2K3, Windows Server 2008, and Windows Server 2012

Este documento en formato PDF 1.4 fue generado por Help & Manual 6 / wPDF3 by WPCubed GmbH, y fue enviado en caja-pdf.es el 18/06/2014 a las 15:15, desde la dirección IP 80.94.x.x. La página de descarga de documentos ha sido vista 1132 veces.
Tamaño del archivo: 240 KB (17 páginas).
Privacidad: archivo público




Descargar el documento PDF









Vista previa del documento


Passcape Software

DPAPI flaw
Vulnerability of DPAPI data protection in
Win2K, Win2K3, Windows Server 2008, and
Windows Server 2012

Content

2

1

Brief description of the vulnerability

1.1

The...................................................................................................................................
problem
2

1.2

Affected
software
...................................................................................................................................
2

2

Technical details

2.1

DPAPI
encryption in Windows XP and higher OSes
...................................................................................................................................
4

2.2

DPAPI
encryption in OS Windows 2000
...................................................................................................................................
4

2.3

DPAPI
encryption flaw in Windows 2003, 2008, 2012 server OSes
...................................................................................................................................
5

3

Utilizing the vulnerability

3.1

Creating
interactive domain user in Windows 2012 server
...................................................................................................................................
8

3.2

Creating
the Master Key and DPAPI secret for the new user
...................................................................................................................................
8

3.3

Decrypting
the user DPAPI secret without knowing the owner logon password
...................................................................................................................................
8

4

Conclusion

2

4

8

14

DPAPI flaw

Part

I
Brief description of the vulnerability

1

Passcape Software

1

DPAPI flaw

Brief description of the vulnerability
1.1

The problem

One of our previous articles described the operating principles of the DPAPI system, its
exceptional reliability, functional value, and cracking resistance. Not long ago, we
occasionally found out that some DPAPI blobs in Windows 2003 had decryption issues.
After determining the cause of the problem, a rather interesting breach in DPAPI security
was revealed which can be reproduced in all server operating systems, beginning with
Win2K and ending with Windows Server 2012.
Briefly, the essence of it is the following: By default, the Master Keys of all domain users
with interactive logon privileges, except for built-in accounts, are created in the Windows
2000 compatibility mode; therefore, the decryption of the data encrypted with DPAPI
doesn’t require the owner’s logon password.

1.2

Affected software

This means that any Administrator or any other user who has physical access to the server
can decrypt the following personal data of vulnerable user accounts:
Passwords and form auto-completion data in the popular browsers: Internet Explorer,
Google Chrome, Opera Browser, etc.
E-mail account passwords in Outlook, Windows Mail, Windows Live Mail, etc.
Account passwords of the Windows FTP manager
Access passwords to shared folders and resources
Keys and passwords to wireless networks
Encryption keys in Windows CardSpace
Encryption keys in Windows Vault
Remote desktop connection passwords
.NET Passport passwords
Windows Live ID personal data
Private keys in encrypting file system (EFS)
Encryption keys in S-MIME mail
Users’ certificates
Private data in the Internet Information Services
EAP/TLS and 802.1x authentication
Network passwords in the Credential Manager
Personal data in any application, programmatically protected with the Windows API
function CryptProtectData, such as Skype, Windows Rights Management Services,
Windows Media, MSN messenger, Google Talk, etc.

2

Passcape Software

DPAPI flaw

Part

II
Technical details

3

Passcape Software

2

DPAPI flaw

Technical details
2.1

DPAPI encryption in Windows XP and higher OSes

This is what the process of decrypting private data encrypted with DPAPI looks like (some
details are omitted): Initially, the data owner’s logon password is passed through SHA-1 to
get the password hash; the password hash and the owner’s SID are then fed to PBKDF2
function. At the output, that produces a prekey, which participates in the decryption of the
Master Key. The decrypted Master Key in its turn is used for the decryption of the actual
DPAPI blobs. Here is what it looks like in a chart:

2.2

DPAPI encryption in OS Windows 2000

The first implementation of DPAPI used in Windows 2000 had other Master Key
encryption algorithms. But that wasn’t what has made it extremely vulnerable; it was the
fact that in order to obtain the user’s password hash, it used MD4 hashing function instead
of SHA-1. Here is what it looks like:

4

Passcape Software

DPAPI flaw

Technical details

2

Amusingly, the same hashing function is also used in validating users’ logon passwords,
the hashes of which are stored either in the SAM registry or in the Active Directory (for
server operating systems). Thus, the user’s plaintext password is not really necessary do
decrypt the Master Key. It is sufficient to just take an existing MD4 hash of the respective
user from SAM or NTDS.DIT and use it as data-in. The rest is already known.

2.3

DPAPI encryption flaw in Windows 2003, 2008, 2012
server OSes

Which algorithm is used – SHA-1 or MD4 – is specified in the header of the Master Key.
Bit 4 of the dwPolicy flag indicates that the Master Key uses the SHA-1 algorithm. Newly
created users with interactive logon privileges in Windows server OSes do not have this
flag set by default. Respectively, the decryption of their private data doesn’t require the
logon password.

5

Passcape Software

2

DPAPI flaw

Technical details

6

Passcape Software

DPAPI flaw

Part

III
Utilizing the vulnerability

7

Passcape Software

3

DPAPI flaw

Utilizing the vulnerability
3.1

Creating interactive domain user in Windows 2012
server

Let’s move on from theory to practice and try adding a new user to a Windows Server
2012 domain, then create some DPAPI secret and then decrypting it offline without the
owner’s logon password.
Open the “Active Directory Users and Computers” console and create a new domain user
named Test. Grant that user an interactive logon privilege. To do so, you can simply add
that user to the local administrators group.

3.2

Creating the Master Key and DPAPI secret for the new
user

Now we need to log off the system and then logon under this account. The new account
doesn’t have the Master Key yet. It will be created during the first call of the
CryptProtectData function. We’ll speed that process up by forcing the call for the
respective function. For that purpose, we have a homonymous utility
CryptProtectData.exe, which simply calls the API function CryptProtectData with
command-line parameters (the utility source code is available on the website). Launch it
with the following parameters: CryptProtectData mysupersecret out.dat. At the output,
we’ll have the out.dat file with a DPAPI blob containing our encrypted text (mysupersecret).
So, the Master Key has been created and stored in the folder C:\Users\test\AppData
\Roaming\Microsoft\Protect\<SID>\<mk>
Where <SID> – the owner’s sid. We’ll still need it, so either memorize it or copy the entire
catalog.
<mk> – name of DPAPI Master Key; e.g., 6cdd0a92-eacc-4a6a-9af5-263ba1afdbf5
Other than that, for the offline decryption of the out.dat file we’ll need the MD4 hash of the
data owner, which is stored in the Active Directory. To get it, we’ll take advantage of our
utility and make a copy of the NTDS.DIT file, as well as a copy the SYSTEM registry
required for obtaining the hash.

3.3

Decrypting the user DPAPI secret without knowing the
owner logon password

As the result, we’ll have:
The out.dat file with the encrypted secret, which we need to decrypt
The data owner’s textual SID
His Master Key
The owner’s hash (files NTDS.DIT and SYSTEM).

8

Passcape Software

DPAPI flaw

Utilizing the vulnerability

3

Now, launch the DPAPI offline decryption utility and tell it the path to the out.dat file.

9

Passcape Software

3

DPAPI flaw

Utilizing the vulnerability

On the second step of the Wizad, specify the path to the data owner’s Master Key: select
the path and then click Next. The program pops a warning that a vulnerability is found in
the Master Key, and therefore the decryption can be carried out two ways: with the user’s
password and without it. We, certainly, want the latter.

10

Passcape Software

DPAPI flaw

Utilizing the vulnerability

3

So, on the next step of the Wizard, enter the owner’s SID and the path to the NTDS.DIT
and SYSTEM files, leaving the password field blank.

11

Passcape Software

3

DPAPI flaw

Utilizing the vulnerability

Click Next, and here we have the decrypted secret. As you can see, the owner’s password
wasn’t necessary.

12

Passcape Software

DPAPI flaw

Part

IV
Conclusion

13

Passcape Software

4

DPAPI flaw

Conclusion
What remains quite unclear is whether this flaw in the interactive users is related to an
error or it shouldn’t be treated as such. Perhaps this is a peculiarity of the DPAPI
implementation in the server operating systems; for instance, to provide backward
compatibility. On the other hand, this seems to be highly unlikely, as the safety of user’s
confidential data is not properly ensured, while DPAPI was specifically meant to be the
data protection system based on the owner’s password. Funny, but it turns out that
desktop PCs are more resistant to offline password recovery than those running the
server operating systems. One way or the other, system administrators should be aware
of this vulnerability, as forewarned is forearmed.

14

Passcape Software

Product and company names mentioned in this manual may be
trademarks or registered trademarks of their respective companies.
Mention of third-party products is for informational purposes only
and constitutes neither an endorsement nor a recommendation. The
author assumes no responsibility w ith regard to the performance or
use of these products. All understandings, agreements, or
w arranties, if any, take place directly betw een the vendors and the
prospective users. Every effort has been made to ensure that the
information in this manual is accurate. The author is not responsible
for printing or clerical errors.
The product described in this manual incorporates copyright
protection technology that is protected by method claims of certain
U.S. patents and other intellectual property rights.
© 2014 Passcape Softw are.
All rights reserved.


Documentos relacionados


Documento PDF passcape software
Documento PDF window server
Documento PDF eset emsx 45 userguide esn
Documento PDF cuestionario grado quinto
Documento PDF practica final 1
Documento PDF microsoft press ebook introducing microsoft sql server 2014 pdf


Palabras claves relacionadas