[NT] DameWare Passes Weak File Encryption Key in the Clear

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To: list@securiteam.com
Date: 25 Mar 2004 16:45:04 +0200

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  DameWare Passes Weak File Encryption Key in the Clear
------------------------------------------------------------------------

SUMMARY

 <http://www.dameware.com/> DameWare Mini Remote, "A lightweight remote
control intended primarily for administrators and help desks for quick and
easy deployment without external dependencies and machine reboot".
DameWare Mini Remote has been found to contain a vulnerability that would
allow an attacker to hijack content sent by DameWare supposedly in a
secure manner (encrypted).

DETAILS

Vulnerable Systems:
 * DameWare Mini Remote Control version 4.1.0.0 and prior

DameWare Mini Remote Control passes a Blowfish encryption key over the
wire in the clear. It is bad enough that they appear to be using Blowfish
in Electronic Codebook Mode; but they compound their errors by the
following two vulnerabilities:

1) The DameWare Mini Remote Control offers the capability to transfer
files between the host and client encrypted using 128-bit Blowfish
Encryption. Their first mistake is using a poor random bit generator to
create their encryption key. After identifying the key in the clear I was
able to surmise that the lack of cryptographic expertise of the DameWare
developers was systemic and checked to see if they were using the built-in
rand() function to generate the key. It did not take long to exhaust the
small space of the Windows' linear congruential generator (LCG) in rand()
to discover the following hypothesized loop for generating their file
encryption key.

int i;
unsigned char dw_f_key[16];
srand(time(NULL));
for(i=0;i<16;i++){
 dw_f_key[i] = rand();
}

2) A more serious mistake is that they actually pass the file encryption
key in the clear over the wire. This can be seen by analyzing packets
between host and target. In a packet just prior to the file being sent the
second to the last string of 16-bytes is the file encryption key.

ADDITIONAL INFORMATION

The information has been provided by <mailto:ax09001h@hotmail.com>
ax09001h.

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