Summerschool Aachen 2004/Network Reconnaissance Lab

Notes on Presentations

Fingerprinting

We also worked on our mandatory assignemt. Our idea was basically first to parse the http://cr.yp.to/surveys/dns1.html page with a perl script and load the fingerprints into our datastructure, into which also the fingerprints of the ftp and smtp servers were to be loaded. We planed to use the already implemented functions which computed the fingerprint of a server and pipe their output to our script and compare it with the stored values in our datastructure. When calling our script the user was expected to give it as a parameter a value N and our script was supposed to output for the best N matches of our fingerprint with the fingerprints stored in our datastructure the name of the corresponding server. However, my project partner left the group at 6.30 pm and I was left alone and consequently joined another project group.

--Samad Nasserian

Notes on Lab Session

Some more fingerprinting

After having been one of the guys complaining about the assignment, too, I nevertheless sat down and started coding. After putting some thought into it and maybe also reducing my own expectations, I found a way to get the whole thing going with not too many lines of perl code.

The script right now is still a bit messy, it depends on certain subroutines being available inside the script itself instead of using a modular or oo-based structure. But it is conceptually extendable and is not too hard to clean up. I then implemented the smtp parsing and scanning as proof of concept. It should be possible to add other protocols quite easily.

The only problem I still have left is one of matching two strings. I definitely get the expected status codes from the servers I am fingerprinting, only something inside my script doesn't want me to successfully match against the database :-)

-- Ernest Hammerschmidt

SNMP Reconnaissance

This is a placeholder for the results of the SNMP scanning I've been doing, but here's a list of default passwords that others might find useful

-- Stephen Lewis

Fingerprinting

So we gave out some mandatory work for today. It was considered boring and frustrating by most and they considered all other possibilities more entertaining. Is that a patter about the grass being greener elsewhere? Alexander seemed to consider the requirement of doing something he doesn't enjoy for a whole afternoon to hard and left without notice. I'm disappointed about that.

To find out if the task was really unbearable I sat down myself and implemented what I asked for. The basic parser was quickly done:

    def loadFingerprints(self): 
        # seek list of probes 
        for l in sys.stdin: 
            if 'Here are the DNS packets sent by the surveying program:' in l: 
                break 
        for l in sys.stdin: 
            if l.startswith('<tr><td align=right>'): 
                fields = l.split('<td>') 
                # this IS exploiutable 
                tests.append((eval(fields[1].strip('</>tdtr')), fields[2].strip('</>tdtr</td></tr>\n'))) 
            if '</table>' in l: 
                break 
 
        # seek list of probes 
        for l in sys.stdin: 
            if not l.startswith('<tr><td>'): 
                continue 
            if l.startswith('<tr><td>Software</td>'): 
                continue 
            probes.append([x.replace('</td>', '').replace('tr>', '').strip(' </\n') for x in l.split('<td>')])

Crude, but works. Mostly. I get entries like

[, 'BIND 9.2', '4q', '5', '5', '1q', '2', '1q', '1q', '1q', '1q', '3AA', '0AA', '3AA', '3AA', '3AA', '3AA', '3AA', '4q', '4q', '4q', '3AA', '3AA', '5', '0AAD, 2, 5']

that is fine, but others are not

[, '1', '1', 't', 't', 't', 't', 't', 't', '1', 't', '0', 't', '0', '15', '0Z0', '0', '0', 't', 't', 't', '0', '0', 't', '4']

I decided to leave that problem for later.

Scaning was easy now:

     def scanTargets(self, targetlist, timeout=1): 
        for target in targetlist:
            s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) 
            s.settimeout(timeout)
            s.connect((target, 53)) 
            for test, desc in tests: 
                flags = []    
                reply = None 
                retries = 5 
                while 1: 
                    print 'sending %r ...' %test, 
                    s.send(test) 
                    try: 
                        reply = s.recv(1500)     
                        print repr(reply) 
                        break   
                    except socket.timeout: 
                        print "timeout"
                        retries -= 1 
                        if retries < 0: 
                            flags.append('t') 
                            break
                if reply: 
                    flags.extend(self.checkFlags(reply)) 
                print "xxx", flags 

I did parse the response with pydns:

    def checkFlags(self, reply): 
 
        flags = [] 
        u = DNS.Lib.Munpacker(reply) 
        r = DNS.Lib.DnsResult(u, []) 
        # check RCODE 
        flags.append(r.header['rcode']) 
        if r.header['tc']: 
            flags.append('TC') 
        if r.header['rd']: 
            flags.append('RD') 
        if r.header['aa']: 
            flags.append('AA') 
        if r.answers: 
            flags.append('D') 
        if len(r.questions) == 0: 
            flags.append('q') 
        if len(r.questions) == 0: 
            flags.append('Q2') 
        # X is missing 
 
        # print vars(r) 
        return flags 

But I failed to implement matching against the fingerprints database. I also got far to much timeouts to my DNS queries. I didn't investigate further. :-(

-- MaxDornseif