Upstream PR:
https://github.com/SSSD/sssd/pull/868

Upstream Ticket:
https://pagure.io/SSSD/sssd/issue/4065

Steps to reproduce:
1. Configure SSSD against AD
2. Create user named say 'user-1'
2. Set its UPN to `TestUserUPN` (different from the username)
3. Run:

```
dbus-send --print-reply --system --dest=org.freedesktop.sssd.infopipe /org/freedesktop/sssd/infopipe org.freedesktop.sssd.infopipe.GetUserAttr string:TestUserUPN array:string:name
Error sbus.Error.NotFound: No such file or directory
```

Just to clarify things:
AD seems (Summit to clarify) to ignore UPN settings as Kerberos ticket are always generated in form of sAMAccountName@domain.
So it is correct that the example above does not work (Summit will know).

My point was if we actually used uid attribute, i.e.
ldap_user_name = uid # let's go strict RFC2307 here

 AND then we have an user where uid != sAMAccountName, then we have a problem for sure.

I am not a AD expert so not sure which role the UPN settings plays here - to me it looks like it is (as far as Apache and Kerberos concerns) completely ignored.

Switching to POST as this was resolved upstream.

* `master`
    * 18611d70e2916138103a099d45861252d6323366 - ifp: let cache_req parse input name so it can fallback to upn search

Verified with
[root@vm-10-0-108-222 ~]# rpm -qa sssd
sssd-2.2.3-6.el8.x86_64

Verification steps:
1) configure SSSD against AD server
[root@vm-10-0-108-222 ~]# cat /etc/sssd/sssd.conf 

[sssd]
domains = t1adpy12r82g.com
config_file_version = 2
services = nss, pam

[domain/t1adpy12r82g.com]
ad_domain = t1adpy12r82g.com
krb5_realm = T1ADPY12R82G.COM
realmd_tags = manages-system joined-with-adcli 
cache_credentials = True
id_provider = ad
krb5_store_password_if_offline = True
default_shell = /bin/bash
ldap_id_mapping = True
use_fully_qualified_names = True
fallback_homedir = /home/%u@%d
access_provider = ad

2) Add user-1 in AD server
[root@vm-10-0-108-222 ~]# getent passwd user-1
user-1:*:1682201112:1682200513:user-1:/home/user-1:/bin/bash

3) Set its UPN to `TestUserUPN` using Powershell command 

PS C:\Users\Administrator> Set-ADUser -UserPrincipalName TestUserUPN -Identity user-1

4) run
dbus-send --print-reply --system --dest=org.freedesktop.sssd.infopipe /org/freedesktop/sssd/infopipe org.freedesktop.sssd.infopipe.GetUserAttr string:TestUserUPN array:string:name

[root@vm-10-0-108-222 ~]# dbus-send --print-reply --system --dest=org.freedesktop.sssd.infopipe /org/freedesktop/sssd/infopipe org.freedesktop.sssd.infopipe.GetUserAttr string:TestUserUPN array:string:name
method return time=1582257563.951842 sender=:1.220 -> destination=:1.219 serial=6 reply_serial=2
   array [
      dict entry(
         string "name"
         variant             array [
               string "user-1"
            ]
      )
   ]


Thus from above observations marking this bug as Verified

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2020:1863