Add a warning for MS08-068 when applicable

[zeroSteiner]

This adds a warning that intends to help users that are performing relay attacks. It notes that the attack won't work when relaying SMB to SMB on the same host if the MS08-068 patch has been applied. I think it still makes sense to attempt the attack in case port forwarding is in use, or the target maybe isn't Windows.

Verification

List the steps needed to make sure this thing works

• Start msfconsole
• use exploit/windows/smb/smb_relay
• Set the RHOSTS to a target you can login to
• Login to that target and use net use to trigger an authentication attempt to Metasploit and see a helpful error message that it probably wont work
• See the attack fail because we try anyways

Demo

[jheysel-r7]

Thanks for making this fix 🙇 Testing was as expected:

msf6 exploit(windows/smb/smb_relay) > run
[*] Exploit running as background job 0.
[*] Exploit completed, but no session was created.

[*] Started reverse TCP handler on 192.168.1.65:4444
msf6 exploit(windows/smb/smb_relay) > [!] Warning: RHOSTS datastore value has been set which is not supported by this module. Please verify RELAY_TARGETS is set correctly.
[*] SMB Server is running. Listening on 0.0.0.0:445
[*] Server started.
[*] New request from 172.16.199.200
[*] Received request for kerberos.issue\Administrator
[*] Relaying to next target smb://172.16.199.200:445
[!] Relaying SMB to SMB on the same host will not work if the target has been patched for MS08-068
[!] Identity: kerberos.issue\Administrator - Relayed client authentication failed on target server smb://172.16.199.200:445

[jheysel-r7]

Release Note

Adds a warning that intends to help users that are performing relay attacks. It notes that the attack won't work when relaying SMB to SMB on the same host if the MS08-068 patch has been applied.