[ldns-users] qualifying a dns packet before processing

[Willem Toorop]

Hi Edward,

I agree ldns_wire2pkt shouldn't be able to crash like this. Even when
the input data would be garbage (provided playload_length doesn't exceed
the memory for the data of course). Can you reproduce the error? Could
you file a bug report here:

	https://www.nlnetlabs.nl/bugs-script/enter_bug.cgi?product=ldns

Thanks!

-- Willem

Op 18-03-12 10:07, Edward Fjellskål schreef:
> Hi again list :)
> 
> So, I parse dns packets, and today I use ldns_wire2pkt to determine
> if I should go on or not, like:
> 
> -----8<-----
> status = ldns_wire2pkt(&decoded_dns,payload, payload_length);
> 
> if (status != LDNS_STATUS_OK) {
>     debug_log("[D] ldns_wire2pkt status = %d\n", status);
>     return;
> }
> -----8<-----
> 
> But some packets processed give me:
> 
> *** stack smashing detected ***
> ======= Backtrace: =========
> /lib/tls/i686/cmov/libc.so.6(__fortify_fail+0x50)[0x2622d0]
> /lib/tls/i686/cmov/libc.so.6(+0xe227a)[0x26227a]
> /usr/lib/libldns.so.1(+0x37204)[0xf16204]
> /usr/lib/libldns.so.1(ldns_wire2dname+0x253)[0xef5b23]
> /usr/lib/libldns.so.1(ldns_wire2rr+0x49)[0xef5db9]
> /usr/lib/libldns.so.1(ldns_wire2pkt+0x239)[0xef6119]
> 
> 
> Are there any other good way to do pre-qualifying of incoming data,
> so it might make popping my stack a bit harder with lib ldns ?
> 
> great lib btw :)
> 
> E
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