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[Andreas <1952219@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

Ubuntu Release:  Ubuntu 20.04.3 LTS
Package: samba 4.13.14+dfsg-0ubuntu0.20.04.1

Expected behavior:
I'm running a 20.04.03 LTS server joined into an AD-Domain via sssd.
Logging in via ssh works like fine. 
The server also exports the user homes via samba, so the users can access
their homes e.g. via \\myserver\myusername from their Windows10 desktops
"just like that". The authentication via kerberos works flawlessly,
they do not have to provide a password. 
That was the case for the system as long as it was running samba version 4.11.6.

What happens instead?
After a regular nightly system security update, the samba server
stack went from:

libsmbclient 2:4.11.6+dfsg-0ubuntu1.10 samba install ok installed
libwbclient0 2:4.11.6+dfsg-0ubuntu1.10 samba install ok installed
python3-samba 2:4.11.6+dfsg-0ubuntu1.10 samba install ok installed
samba 2:4.11.6+dfsg-0ubuntu1.10  hold ok installed
samba-common 2:4.11.6+dfsg-0ubuntu1.10 samba install ok installed
samba-common-bin 2:4.11.6+dfsg-0ubuntu1.10 samba install ok installed
samba-dsdb-modules 2:4.11.6+dfsg-0ubuntu1.10 samba install ok installed
samba-libs 2:4.11.6+dfsg-0ubuntu1.10 samba install ok installed
samba-vfs-modules 2:4.11.6+dfsg-0ubuntu1.10 samba install ok installed

to:

libsmbclient 2:4.13.14+dfsg-0ubuntu0.20.04.1 samba install ok installed
libwbclient0 2:4.13.14+dfsg-0ubuntu0.20.04.1 samba install ok installed
python3-samba 2:4.13.14+dfsg-0ubuntu0.20.04.1 samba install ok installed
samba 2:4.13.14+dfsg-0ubuntu0.20.04.1  install ok installed
samba-common 2:4.13.14+dfsg-0ubuntu0.20.04.1 samba install ok installed
samba-common-bin 2:4.13.14+dfsg-0ubuntu0.20.04.1 samba install ok installed
samba-dsdb-modules 2:4.13.14+dfsg-0ubuntu0.20.04.1 samba install ok installed
samba-libs 2:4.13.14+dfsg-0ubuntu0.20.04.1 samba install ok installed
samba-vfs-modules 2:4.13.14+dfsg-0ubuntu0.20.04.1 samba install ok installed

(aktually the following packages got updated:
libicu66 libipa-hbac0 libldb2 libsmbclient libsss-idmap0 libwbclient0 python3-ldb python3-samba python3-sss samba samba-common samba-common-bin samba-dsdb-modules samba-libs samba-vfs-modules sssd sssd-ad sssd-ad-common sssd-common sssd-ipa sssd-krb5 sssd-krb5-common sssd-ldap sssd-proxy sssd-tools)

After the update, the export of the user homes is not working anymore. 
The Windows10 users are not able to reach it via "\\myserver\myusername".  
The share is unavailable.

I can reproduce that behavior, by restoring an older snapshot
of that virtual server. It works fine at first (immediately after the
restore), but then  -after an initiated package update- it stops working.

Here is my smb.conf:

-------------------------------------------------------
[global]
interfaces = lo ens160
bind interfaces only = yes
 realm = MYDOMA.IN
        kerberos method = secrets and keytab
   server string = %h server (Samba, Ubuntu)
   log file = /var/log/samba/log.%m
   max log size = 1000
   logging = file
   panic action = /usr/share/samba/panic-action %d
 log level = 3
   server role = standalone server
   obey pam restrictions = yes
   unix password sync = yes
   passwd program = /usr/bin/passwd %u
   passwd chat = *Enter\snew\s*\spassword:* %n\n *Retype\snew\s*\spassword:* %n\n *password\supdated\ssuccessfully* .
   pam password change = yes
   map to guest = bad user
   usershare allow guests = yes
[Homes]
    comment = User Homes
    path = /home/mydoma.in/%U
    browsable = yes
    valid users = %U
    force group = "Domain users"
    follow symlinks = yes
    wide links = no
    writable = yes
    read only = no
    force create mode = 0660
    create mask = 0777
    directory mask = 0777
    force directory mode = 0770
    access based share enum = yes
    hide unreadable = yes
----------------------------------------------------------

When trying to connect from a Windows10 client, the updated samba server
(4.13.14) logs for that particular IP address show:

[2021/11/25 11:12:52.256505,  1] ../../source3/librpc/crypto/gse_krb5.c:179(fill_mem_keytab_from_secrets)
  fill_mem_keytab_from_secrets: secrets_fetch_or_upgrade_domain_info(WORKGROUP) - NT_STATUS_CANT_ACCESS_DOMAIN_INFO
[2021/11/25 11:12:52.256532,  3] ../../source3/librpc/crypto/gse_krb5.c:570(gse_krb5_get_server_keytab)
  ../../source3/librpc/crypto/gse_krb5.c:570: Warning! Unable to set mem keytab from secrets!
[2021/11/25 11:12:52.258626,  1] ../../source3/librpc/crypto/gse_krb5.c:179(fill_mem_keytab_from_secrets)
  fill_mem_keytab_from_secrets: secrets_fetch_or_upgrade_domain_info(WORKGROUP) - NT_STATUS_CANT_ACCESS_DOMAIN_INFO
[2021/11/25 11:12:52.258647,  3] ../../source3/librpc/crypto/gse_krb5.c:570(gse_krb5_get_server_keytab)
  ../../source3/librpc/crypto/gse_krb5.c:570: Warning! Unable to set mem keytab from secrets!
[2021/11/25 11:12:52.259947,  1] ../../source3/auth/auth_generic.c:209(auth3_generate_session_info_pac)
  auth3_generate_session_info_pac: Unexpected PAC for [myuser@MYDOMAIN] in standalone mode - NT_STATUS_BAD_TOKEN_TYPE
[2021/11/25 11:12:52.259983,  3] ../../source3/smbd/smb2_server.c:3861(smbd_smb2_request_error_ex)
  smbd_smb2_request_error_ex: smbd_smb2_request_error_ex: idx[1] status[NT_STATUS_BAD_TOKEN_TYPE] || at ../../source3/smbd/smb2_sesssetup.c:146
[2021/11/25 11:12:52.260415,  3] ../../source3/smbd/server_exit.c:220(exit_server_common)
  Server exit (NT_STATUS_CONNECTION_RESET)

** Affects: samba (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1952219

Title:
  AD-joined Samba Server stops working after upgrade to
  4.13.14+dfsg-0ubuntu0.20.04.1

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