bugtraq - Dameware Passes Weak File Encryption Key in the Clear

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Message-ID: <20040323201710.16065.qmail@www.securityfocus.com>
Date: 23 Mar 2004 20:17:10 -0000
From: ax09001h <ax09001h@...mail.com>
To: bugtraq@...urityfocus.com
Subject: Dameware Passes Weak File Encryption Key in the Clear

Dameware Mini Remote Control version 4.1.0.0 and presumably other versions pass 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.

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();
}

The second major and 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.