Bug 2121914

Description of problem:

When booting a system in rescue mode and having "user data" LUKS devices on the system, it's mandatory for the user to unlock those even though this should just be optional because these are not useful to troubleshoot system boot related to some issue with the system filesystems (/, /boot, /usr, etc.).
This is because of a bug in the python-simpleline implementation available on RHEL8: not entering a passphrase (through just typing "Enter" key) leads to the modal dialog to remain alive and hang Anaconda Rescue module.

This bug is critical because in some cases, the admin can just NOT unlock the LUKS devices, typically if there is no passphrase associated to the LUKS device and Clevis is used instead.

The bug is in file `/usr/lib/python3.6/site-packages/simpleline/render/adv_widgets.py`:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
 60 class PasswordDialog(UIScreen):
 61     """Dialog screen for password input."""
 :
 78     def prompt(self, args=None):
 :
 89         self._password = handler.value
 90         if not self._password:
 91             return None
 92         else:
 93             # this may seem innocuous, but it's really a giant hack; we should
 94             # not be calling close() from prompt(), but the input handling code
 95             # in the TUI is such that without this very simple workaround, we
 96             # would be forever pelting users with a prompt to enter their pw
 97             self.close()
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

Here above, a test is made is password is empty on line 90, leading to just returning None and never closing the dialog.
The patch, which is already implemented in a more recent release of `python-simpleline` (found for example on Fedora 36 through `python3-simpleline-1.9.0-2.fc36.noarch` package) consists in unconditionally closing the dialog (and returning "None" as well):
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
 62 class PasswordDialog(UIScreen):
 :
 80     def prompt(self, args=None):
 :
 91         self._password = handler.value
 92 
 93         # this may seem innocuous, but it's really a giant hack; we should
 94         # not be calling close() from prompt(), but the input handling code
 95         # in the TUI is such that without this very simple workaround, we
 96         # would be forever pelting users with a prompt to enter their pw
 97         self.close()
 98         return None
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

Version-Release number of selected component (if applicable):

All python-simpleline including python-simpleline-1.1.1-2.el8.noarch

How reproducible:

Always

Steps to Reproduce:
1. Add a second disk to a VM on which a LVM LV will be encrypted and boot the VM
2. Create the encrypted disk

   # vgcreate data /dev/vdb
   # lvcreate -n luksdata -L 2G data
   # cryptsetup luksFormat /dev/data/luksdata --force-password
   --> "redhat"
   # UUID=$(cryptsetup luksUUID /dev/data/luksdata)
   # echo "luks-$UUID UUID=$UUID none discard" >> /etc/crypttab
   # cryptsetup luksOpen /dev/data/luksdata luks-$UUID
   # mkfs.xfs -L "LUKS XFS" /dev/mapper/luks-$UUID
   # echo "/dev/mapper/luks-$UUID /luksdata xfs defaults,x-systemd.device-timeout=0 0 0" >> /etc/fstab

3. Boot with RHEL DVD in Troubleshooting mode and select "1) Continue"

4. Enter no passphrase by just typing "Enter" key

Actual results:

-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
================================================================================
Password

                                 data-luksdata

Passphrase: <CR>
--> hangs there forever
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

Expected results: continues to /mnt/sysroot prompt without unlocking

-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
================================================================================
Password

                                 data-luksdata

Passphrase: <CR>
================================================================================
================================================================================
Rescue Shell

Your system has been mounted under /mnt/sysroot.
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------