Re: local proxy udp 53

From: Nicolas RUFF (nicolas.ruff@gmail.com)
Date: Sun Feb 19 2006 - 06:28:52 EST


> Take a look at the NSTX project:
> http://nstx.dereference.de/nstx/

Personnally, I consider NSTX more like a "proof of concept" rather than
a field-useable tool. Apart from not being multi-user, it has been
plagued by a bug for several years that will make it crash if a
legitimate DNS request is received (!)

The first byte of the DNS request is used to store the request length,
but the request length is also computed by strlen(). NSTX-1.1b5 code is:

nstx_encode.c:82 *rlen = i - revmap[data[0]];
where i = strlen(data);
and rlen = &len;

When len<0, large amounts of memory will be overwritten in the following
memcpy():
nstx_pstack.c:151 memcpy(ptr->data, data, len);

Author has been contacted last year, but the tool is not actively
maintained (last update 10 monthes ago).

PoC :

# nslookup
> server target.com
> Z.target.com
(NSTX server on target.com crashes)

Regards,
- Nicolas RUFF
Security Researcher @ EADS-CCR

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