Dear Bugtraq,

This vulnerability was reported by Natalia Melnikova
(Hataha at yandex.ru)

Vulnerability:  Microsoft ActiveSync information leak and spoofing
URL:            http://www.security.nnov.ru/Fnews64.html
Vendor:         Microsoft
Software:       Active Sync 3.8
Author:         Natalia Melnikova


Related Russian article:
"Microsoft ActiveSync (In)Security"
http://www.securitylab.ru/56278.html


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Microsoft ActiveSync clear text password


Microsoft  ActiveSync  is  widely used to synchronies Windows based PDAs
and  smartphones  with  desktop  computer.  PDA  can  connect  to PC via
COM/USB/IR  or  LAN.  Before  synchronization  user  on  PC  must  setup
"partnership"  to  allow  synchronization.  If  PDA  is  protected  with
password  user  on  PC  should provide password before he can access the
device.

Synchronization over LAN has some design weakness.

1. All data, including initial "authentication", is transmitted in clear
text.   This  is  OK  in  case  COM/USB  and  other  physical  protected
communication,  but  LAN  (Wi-Fi  in  most  cases) is very sensitive for
sniffing.
2. Even if PDA is password protected, ActiveSync doesn't ask password in
case of network synchronization. I’m not sure, what is it - security bug
or feature, because password is transmitted in clear text over USB.
3.  ActiveSync doesn't use any form of authentication for server (PC) or
client (PDA), so fake server or fake client attack is possible.

Discover Activesync with LAN synchronization allowed

nmap -p 5679 192.168.0.*

Fake server

It is easy to build fake server attack without special software. All you
need are ActiveSync, sniffer and any MitM condition.

1. Install ActiveSync on fake server. Enable network synchronization
2. Realize MitM condition.
3. Launch you favorite sniffer and set filter to save TCP packets on port 5679.
4. Wait for PDA connection.
5. Open sniffer and check second data packet from PDA. At offset 0x14 and 0x18 you can see partnerships ids. Activesync can support up to 2 PC and as you can see, PDA send both IDs in the "handshake"
6. Import template in registry. Change key HKEY_CURRENT_USER\Software\Microsoft\Windows CE Services\Partners\<Partnerhsip> to sniffed partnership id.
7. Wait for another connection and check ActiveSinc, device should be connected as "guest". Even if you got "Synchronization Error", try to click "Explore" button on the toolbar.

Fake Client

Is  very  similar to the fake server, but you don't need MitM conditions
to   accomplish  this  attack.  All  you  need  it  a  name  of  PC  and
corresponding "partnership id".

1. Launch your favorite registry editor for Windows Mobile.
2. Navigate to HKLM\Software\Microsoft\Windows CE Services\Partners\P1
3. Create string value  PName = <PC_NAME>
4. Create DWORD value PId = <partnership id>
5. Launch  active  sync on PDA and try to connect. If everything is ok,
synchronization will occur.

Mitigating factors
1. LAN synchronization disabled by default
2. To implement "fake client" you should know Partnership ID. It’s hard
to  guess  (2^32),  but  because  ActiveSync accept 2 partnership ID per
connection, actually we need (2^31) connections for bruteforce.

I  think  ActiveSync should use TLS for authentication of PC and PDA and
data  encryption. We don't need PKI in this case, because "direct trust"
can  be  created  and  certificates  transmitted from PDA to PC and vise
versa when "Partnership" is established.

Thanks 2 3APA3A and everybody in SynCE project