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Re: uml_net bug
Date: Mon, 26 May 2003 19:26:59 +0400

Dear Ktha,

The problem is different: uml_net shouldn't be suid.



An updated kernel-utils package is available that removes the setuid bits
incorrectly assigned to the uml_net binary.

--Saturday, May 24, 2003, 5:10:07 AM, you wrote to bugtraq () securityfocus com:

K> There is a vulnerability in uml_net. The latest version is vulnerable too.

K> The problem is the lack of bounds checking in uml_net.c from uml_utilities,

K> A possible attack could lead to root compromise on some systems since for 

K> example uml_net comes suided root in RH 8.0 by default.

K> Let's look over the code:

K> *       int n = 3, v;

K> we observe how "v" is declared, as a signed integer.

K> with a little bit of "luck" will end up here, knowing that "v" will get 

K> the value of the first parameter (an integer) given to the program:

K> *       if(v > CURRENT_VERSION)

K> so... if "v" is smaller than 0, the test will be passed but "v" will not 

K> be between 0 and CURRENT_VERSION as the author would expected to.

K> after some tests on the second parameter of the program... we should 

K> arrive to this code:

K> *       if(handlers[v] != NULL) (*handlers[v])(argc - n, &argv[n]);

K> here it is called the function located at handlers[v]. by suplying a large 

K> negative integer for "v", handlers[v] can point to the stack which can be 

K> controlled by the user. so, the program can be fooled  to call a user 

K> controlled "function". 

K> since the root privileges are not dropped till this point... the user code 

K> will be executed with super-user privileges.

K> Suggested patch: uml_net.c

K>     - if(v > CURRENT_VERSION){

K>     + if ((v > CURRENT_VERSION) || (v < 0)) {

K> Contact: ktha () hushmail com

You know my name - look up my number (Beatles)

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