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88tcp/udp - Pentesting Kerberos

Reading time: 4 minutes

Basic Information

Kerberos operates on a principle where it authenticates users without directly managing their access to resources. This is an important distinction because it underlines the protocol's role in security frameworks.

In environments like Active Directory, Kerberos is instrumental in establishing the identity of users by validating their secret passwords. This process ensures that each user's identity is confirmed before they interact with network resources. However, Kerberos does not extend its functionality to evaluate or enforce the permissions a user has over specific resources or services. Instead, it provides a secure way of authenticating users, which is a critical first step in the security process.

After authentication by Kerberos, the decision-making process regarding access to resources is delegated to individual services within the network. These services are then responsible for evaluating the authenticated user's rights and permissions, based on the information provided by Kerberos about the user's privileges. This design allows for a separation of concerns between authenticating the identity of users and managing their access rights, enabling a more flexible and secure approach to resource management in distributed networks.

Default Port: 88/tcp/udp

PORT   STATE SERVICE
88/tcp open  kerberos-sec

To learn how to abuse Kerberos you should read the post about Active Directory.

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Shodan

• port:88 kerberos

MS14-068

The MS14-068 flaw permits an attacker to tamper with a legitimate user's Kerberos login token to falsely claim elevated privileges, such as being a Domain Admin. This counterfeit claim is mistakenly validated by the Domain Controller, enabling unauthorized access to network resources across the Active Directory forest.

Kerberos Vulnerability in MS14-068 (KB3011780) Explained – Active Directory Security

Other exploits: https://github.com/SecWiki/windows-kernel-exploits/tree/master/MS14-068/pykek

HackTricks Automatic Commands

Protocol_Name: Kerberos    #Protocol Abbreviation if there is one.
Port_Number:  88   #Comma separated if there is more than one.
Protocol_Description: AD Domain Authentication         #Protocol Abbreviation Spelled out

Entry_1:
  Name: Notes
  Description: Notes for Kerberos
  Note: |
    Kerberos operates on a principle where it authenticates users without directly managing their access to resources. This is an important distinction because it underlines the protocol's role in security frameworks.
    In environments like **Active Directory**, Kerberos is instrumental in establishing the identity of users by validating their secret passwords. This process ensures that each user's identity is confirmed before they interact with network resources. However, Kerberos does not extend its functionality to evaluate or enforce the permissions a user has over specific resources or services. Instead, it provides a secure way of authenticating users, which is a critical first step in the security process.

    https://book.hacktricks.wiki/en/network-services-pentesting/pentesting-kerberos-88/index.html

Entry_2:
  Name: Pre-Creds
  Description: Brute Force to get Usernames
  Command: nmap -p 88 --script=krb5-enum-users --script-args krb5-enum-users.realm="{Domain_Name}",userdb={Big_Userlist} {IP}

Entry_3:
  Name: With Usernames
  Description: Brute Force with Usernames and Passwords
  Note: consider git clone https://github.com/ropnop/kerbrute.git ./kerbrute -h

Entry_4:
  Name: With Creds
  Description: Attempt to get a list of user service principal names
  Command: GetUserSPNs.py -request -dc-ip {IP} active.htb/svc_tgs