2008-02-29

Nmap - os detection for every open tcp port

While ago I created tool, that shows p0f-like signatures for every open port. This signature is based on information taken from single SYN-ACK packet from target port. Sample output:

$ sudo ./nmap -n -sT -PS80 -p21,22,53,80,443 --script=p0f.nse www.cisco.com

Starting Nmap 4.22SOC1 ( http://insecure.org ) at 2007-07-12 00:04 CEST
Interesting ports on 198.133.219.25:
PORT STATE SERVICE
21/tcp open ftp
|_ p0f signature: UNKNOWN [65500:61:1:64:M1436,N,N,S,N,W0,N,N,T:AT:?:?] (link: IPSec/GRE, up: 1446 hrs, ipid:54702)
22/tcp filtered ssh
53/tcp filtered domain
80/tcp open http
|_ p0f signature: UNKNOWN [8192:238:0:44:M1460:A:?:?] (link: ethernet/modem, up: disabled, fill:4008, ipid:1)
443/tcp open https
|_ p0f signature: UNKNOWN [8192:238:0:44:M1460:A:?:?] (link: ethernet/modem, up: disabled, fill:f8ef, ipid:10)
Now I created similar test, but it does full os detection for open port. It uses nmap os detection algorithms to determine what os is on specific port. This is very useful if target uses destination nat and forwards incoming connections to other hosts. Let's look again at the cisco.com:
$ export NMAPDIR=.
$ sudo ./nmap -sS -p25,53,80,113,443,8080 -n www.cisco.com -PS80 --script=os.nse -O

Starting Nmap 4.53 ( http://nmap.org ) at 2008-02-29 12:51 CET
Interesting ports on 198.133.219.25:
PORT STATE SERVICE
25/tcp open smtp
|_ os: NCR 5676 or 5688 automated teller machine (94%), Rockwell Automation 1761-NET-ENI Ethernet-to-RS-232-C interface module (94%), Billion 7404VGO-M DSL router (93%)
53/tcp filtered domain
80/tcp open http
|_ os: D-Link DWL-624+ or TRENDnet TEW-432BRP wireless broadband router (93%), Linksys BEFSR41 EtherFast broadband router or D-Link DCS-6620G webcam (93%), HP 9100c Digital Sender scanner (93%)
113/tcp filtered auth
443/tcp open https
|_ os: D-Link DWL-624+ or TRENDnet TEW-432BRP wireless broadband router (93%), Linksys BEFSR41 EtherFast broadband router or D-Link DCS-6620G webcam (93%), HP 9100c Digital Sender scanner (93%)
8080/tcp closed http-proxy
No OS matches for host
Uptime: 0.007 days (since Fri Feb 29 12:42:05 2008)
I don't suggest that cisco uses D-Link DWL-624. But it's obvious that different host answers to the port 25 and different to ports 80 and 443.

My os detection script is much less reliable than standard nmap -O, because it sends packets to single open port. Normal scan uses also icmp packets, udp probes and tcp closed ports tests.

But I hope that my script can give a brief info of forwarded ports.

If you know how to interpret nmap-os signatures, adding -d1 can give you more detailed information:
$ export NMAPDIR=.
$ sudo ./nmap -sS -p21,22,25,53,80,113,443,8080 -n www.cisco.com -PS80 --script=os.nse -O -d1

Interesting ports on 198.133.219.25:
PORT STATE SERVICE REASON
21/tcp closed ftp reset
22/tcp filtered ssh no-response
25/tcp open smtp syn-ack
| os: Rockwell Automation 1761-NET-ENI Ethernet-to-RS-232-C interface module (94%), Billion 7404VGO-M DSL router (93%), Vodavi XTS-IP PBX (93%)
| seq info: got packets=6 try=1/1 variance=5.431390
| ECN(R=Y%DF=Y%TG=40%W=8052%O=NW3NNSM5B4%CC=N%Q=)
| T2(R=N)
| T3(R=N)
| T4(R=N)
| SEQ(SP=100%GCD=1%ISR=10E%TI=RD%TS=14%uptime=9 minutes)
| OPS(O1=NNT11NW3NNSM5B4%O2=NNT11NW3NNSM5B4%O3=NNT11NW3M5B4%O4=NNT11NW3NNSM5B4%O5=NNT11NW3NNSM5B4%O6=NNT11NNSM5B4)
| WIN(W1=80AE%W2=8017%W3=802D%W4=80AE%W5=802F%W6=FFF7)
|_ T1(R=Y%DF=Y%TG=40%S=O%A=S+%F=AS%RD=0%Q=)
53/tcp filtered domain no-response
80/tcp open http syn-ack
| os: D-Link DWL-624+ or TRENDnet TEW-432BRP wireless broadband router (93%), Linksys BEFSR41 EtherFast broadband router or D-Link DCS-6620G webcam (93%), HP 9100c Digital Sender scanner (93%)
| seq info: got packets=6 try=1/1 variance=2.828427
| ECN(R=Y%DF=N%TG=FF%W=2000%O=M5B4%CC=N%Q=)
| T2(R=N)
| T3(R=N)
| T4(R=N)
| SEQ(SP=108%GCD=1%ISR=10E%TI=RD%TS=U)
| OPS(O1=M5B4%O2=M5B4%O3=M5B4%O4=M5B4%O5=M5B4%O6=M5B4)
| WIN(W1=2000%W2=2000%W3=2000%W4=2000%W5=2000%W6=2000)
|_ T1(R=Y%DF=N%TG=FF%S=O%A=S+%F=AS%RD=0%Q=)
113/tcp filtered auth no-response
443/tcp open https syn-ack
| os: D-Link DWL-624+ or TRENDnet TEW-432BRP wireless broadband router (93%), Linksys BEFSR41 EtherFast broadband router or D-Link DCS-6620G webcam (93%), HP 9100c Digital Sender scanner (93%)
| seq info: got packets=6 try=1/1 variance=1.154701
| ECN(R=Y%DF=N%TG=FF%W=2000%O=M5B4%CC=N%Q=)
| T2(R=N)
| T3(R=N)
| T4(R=N)
| SEQ(SP=105%GCD=1%ISR=106%TI=RD%TS=U)
| OPS(O1=M5B4%O2=M5B4%O3=M5B4%O4=M5B4%O5=M5B4%O6=M5B4)
| WIN(W1=2000%W2=2000%W3=2000%W4=2000%W5=2000%W6=2000)
|_ T1(R=Y%DF=N%TG=FF%S=O%A=S+%F=AS%RD=0%Q=)
I should also make it clear that p0f.nse don't sends any crafted packets (it only openes connection using standard connect()). But os.nse sends at least 10 crafted packet to every open port. That's not very stealthy method.


The sources are in my svn:
svn co svn://svn.insecure.org/nmap-exp/majek04/nmap-6861 nmap-majek


1 comment:

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Sorry for offtopic