Nmap Development mailing list archives
Re: Ncat with ssl using 100% cpu
From: David Fifield <david () bamsoftware com>
Date: Thu, 4 Jun 2009 17:30:46 -0600
On Tue, May 19, 2009 at 04:30:32PM -0300, el draco wrote:
Hi everyone, i was testing ncat a little bit and found that under certain conditions it uses all of my cpu. I'm using: Kubuntu 8.10 Kernel 2.6.27-14-generic SMP openssl 0.9.8g-10 libssl0.9.8 libssl-dev 0.9.8g-10 Nmap 4.85BETA9, svn rev. 13330 Test case 1: a) ncat -l 8000 --ssl b) ncat localhost 8000 --ssl So far so good, and now we type anything on the CLIENT like 'test' Now ncat client is using 100% of cpu. Note that it is still working fine, and you have to type in the client-side and not in the server-side When using strace with the client it keeps printing this forever: select(4, [0 3], [3], [], NULL) = 1 (out [3]) select(4, [0 3], [3], [], NULL) = 1 (out [3]) select(4, [0 3], [3], [], NULL) = 1 (out [3]) select(4, [0 3], [3], [], NULL) = 1 (out [3]) On a side note, if you type on the server-side, everything works just fine. Test case 2: a) ncat -l 8000 --ssl --broker --chat b) ncat localhost 8000 --ssl Now we have two issues. The first is the same as test case 1, if you type anything on client-side, cpu reaches 100% The second one is that if you now type something on server-side, while your cpu is at 100%, .. client-side stop using 100% cpu!! You can repeat this from here again. Typing in the client sets cpu to 100%, typing in the server stop this.
Thanks. I can reproduce this. There used to be a similar problem for non-SSL connections, but it was fixed in Ncat. From some investigation, it appears that this problem is inside Nsock. Somehow select is always returning true in some situations. David Fifield _______________________________________________ Sent through the nmap-dev mailing list http://cgi.insecure.org/mailman/listinfo/nmap-dev Archived at http://SecLists.Org
Current thread:
- Ncat with ssl using 100% cpu el draco (May 19)
- Re: Ncat with ssl using 100% cpu David Fifield (Jun 04)
- Re: Ncat with ssl using 100% cpu (PATCH) David Fifield (Jun 19)
- Re: Ncat with ssl using 100% cpu David Fifield (Jun 04)