Squid - Kerberos - update keytab issue



  • Hi,

    I'm encountering an issue using Kerberos authentication. Indeed, every 30 days, my kerberos authentication breaks.
    (currently, to bypass this issue, I regenerate keytab file).

    Here, the command that I run every 6h to keep my keytab up to date.

    /usr/sbin/msktutil --auto-update --verbose --computer-name KRB-PROX -k /etc/squid/squid.keytab

    Below log I have every run (when everything is ok):

    samedi 21 mars 2020, 06:00:01 (UTC+0100) -- init_password: Wiping the computer password structure -- generate_new_password: Generating a new, random password for the computer account -- generate_new_password: Characters read from /dev/urandom = 88 -- get_dc_host: Attempting to find Domain Controller to use via DNS SRV record in domain XXXXXX.LOCAL for procotol tcp -- get_dc_host: Found DC: xxxxxxxxx.xxxxxxxxx.local -- get_dc_host: Canonicalizing DC through forward/reverse lookup... -- get_dc_host: Found Domain Controller: xxxxxxxx.xxxxxxxxxx.local -- create_fake_krb5_conf: Created a fake krb5.conf file: /tmp/.msktkrb5.conf-ze3JWq -- reload: Reloading Kerberos Context -- finalize_exec: SAM Account Name is: KRB-PROX$ -- try_machine_keytab_princ: Trying to authenticate for KRB-PROX$ from local keytab... -- switch_default_ccache: Using the local credential cache: FILE:/tmp/.mskt_krb5_ccache-t1AykD -- finalize_exec: Authenticated using method 1 -- LDAPConnection: Connecting to LDAP server: xxxxxxxxxx.xxxxxxxxxxxxx.local -- ldap_get_base_dn: Determining default LDAP base: dc=xxxxxxxxxxxxx,dc=LOCAL -- get_default_ou: Determining default OU: CN=Computers,DC=xxxxxxxxxxxxxxx,DC=local -- ldap_get_pwdLastSet: pwdLastSet is 132267790228776214 -- execute: Password last set 28 days ago. -- execute: Exiting because password was changed recently. -- ~KRB5Context: Destroying Kerberos Context

    Below logs when things gone bad:

    lundi 23 mars 2020, 00:00:01 (UTC+0100) -- init_password: Wiping the computer password structure -- generate_new_password: Generating a new, random password for the computer account -- generate_new_password: Characters read from /dev/urandom = 93 -- get_dc_host: Attempting to find Domain Controller to use via DNS SRV record in domain XXXXXX.LOCAL for procotol tcp -- get_dc_host: Found DC: xxxxxxxxxxxx.xxxxxxxxxxx.local -- get_dc_host: Canonicalizing DC through forward/reverse lookup... -- get_dc_host: Found Domain Controller: xxxxxxxxxxxx.xxxxxxxxxxx.local -- create_fake_krb5_conf: Created a fake krb5.conf file: /tmp/.msktkrb5.conf-UYDFiO -- reload: Reloading Kerberos Context -- finalize_exec: SAM Account Name is: KRB-PROX$ -- try_machine_keytab_princ: Trying to authenticate for KRB-PROX$ from local keytab... -- switch_default_ccache: Using the local credential cache: FILE:/tmp/.mskt_krb5_ccache-p6KtWW -- finalize_exec: Authenticated using method 1 -- LDAPConnection: Connecting to LDAP server: xxxxxxxxxxxx.xxxxxxxxxxxx.local -- ldap_get_base_dn: Determining default LDAP base: dc=xxxxxxxxxxxxxx,dc=LOCAL -- get_default_ou: Determining default OU: CN=Computers,DC=xxxxxxxxxxxxxxx,DC=local -- ldap_get_pwdLastSet: pwdLastSet is 132267790228776214 -- execute: Password last set 30 days ago. -- ldap_check_account: Checking that a computer account for KRB-PROX$ exists -- ldap_check_account: Checking computer account - found -- ldap_check_account: Found userAccountControl = 0x1000 -- ldap_check_account: Found supportedEncryptionTypes = 28 -- ldap_check_account: Found dNSHostName = xxxxxxxx.xxxxxxxxxxx.local -- ldap_check_account: Found Principal: HTTP/xxxxxxxxxx.xxxxxxxxxxx.local -- ldap_check_account: Found User Principal: HTTP/proxy.xxxxxxxxxxxxxxxxx.local -- ldap_check_account_strings: Inspecting (and updating) computer account attributes -- ldap_set_supportedEncryptionTypes: No need to change msDs-supportedEncryptionTypes they are 28 -- ldap_set_userAccountControl_flag: Setting userAccountControl bit at 0x200000 to 0x0 -- ldap_set_userAccountControl_flag: userAccountControl not changed 0x1000 -- ldap_get_kvno: KVNO is 1 -- set_password: Attempting to reset computer's password -- set_password: Try using keytab for KRB-PROX$ to change password -- ldap_get_pwdLastSet: pwdLastSet is 132267790228776214 -- set_password: krb5_change_password failed using keytab: (3) Authentication error -- ~KRB5Context: Destroying Kerberos Context

    lundi 23 mars 2020, 06:00:01 (UTC+0100) -- init_password: Wiping the computer password structure -- generate_new_password: Generating a new, random password for the computer account -- generate_new_password: Characters read from /dev/urandom = 90 -- get_dc_host: Attempting to find Domain Controller to use via DNS SRV record in domain xxxxxxxxx.LOCAL for procotol tcp -- get_dc_host: Found DC: xxxxxxxxx.xxxxxxxxx.local -- get_dc_host: Canonicalizing DC through forward/reverse lookup... -- get_dc_host: Found Domain Controller: xxxxxxxxxx.xxxxxxx.local -- create_fake_krb5_conf: Created a fake krb5.conf file: /tmp/.msktkrb5.conf-9XY0Qp -- reload: Reloading Kerberos Context -- finalize_exec: SAM Account Name is: KRB-PROX$ -- try_machine_keytab_princ: Trying to authenticate for KRB-PROX$ from local keytab... -- try_machine_keytab_princ: Error: krb5_get_init_creds_keytab failed (Preauthentication failed) -- try_machine_keytab_princ: Authentication with keytab failed -- try_machine_keytab_princ: Trying to authenticate for KRB-PROX$ from local keytab... -- try_machine_keytab_princ: Error: krb5_get_init_creds_keytab failed (Preauthentication failed) -- try_machine_keytab_princ: Authentication with keytab failed -- try_machine_keytab_princ: Trying to authenticate for host/xxxxxxxxxxx.xxxxxxxxxx.local from local keytab... -- try_machine_keytab_princ: Error: krb5_get_init_creds_keytab failed (Key table entry not found) -- try_machine_keytab_princ: Authentication with keytab failed -- try_machine_password: Trying to authenticate for KRB-PROX$ with password. -- create_default_machine_password: Default machine password for KRB-PROX$ is krb-prox -- try_machine_password: Error: krb5_get_init_creds_keytab failed (Preauthentication failed) -- try_machine_password: Authentication with password failed -- try_user_creds: Checking if default ticket cache has tickets... -- finalize_exec: Authenticated using method 5 -- LDAPConnection: Connecting to LDAP server: xxxxxxxxx.xxxxxxxxx.local -- ~KRB5Context: Destroying Kerberos Context

    Technical information:
    -Windows 2016 server (Kerberos)
    -Squid 3-x
    -msktutil version 1.0

    Thanks for your help!

    Seb


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