[Bug 2097231] Re: LUKS Passphrase: AltGr + Shift Triggers VT100 Pseudographic Mode

[beMOTION]

Hey Daniel.

""VT100 Pseudographic Mode" is a feature of Plymouth which is usually toggled by pressing Escape."
I can reproduce this behavior without pressing ESC and am quite certain I did not repeatedly entered VT100 by accidentally pressing ESC every time I encountered this issue as the key is far away and obviously not used for anything in the passphrase - in addition, I can be more than certain as it is impossible I hit ESC by accident 30 times in a row in the particular event I stated where I restarted the machine 30 times to finally decrypt it.

I have stated how to reproduce this behavior:
VT100 can be entered with AltGr + Q, and AltGr + Shift - atleast with a german keyboard layout. The evidence is the linked jpeg file that clearly proofs that VT100 mode is activated after performing the @ Symbol on a german keyboard layout by AltGr + Q. And this particular photo was created when testing, and while that I performed every key stroke carefully and "slow" (slow as in dedicated and not rushing from Key to Key like with conventional typing).

So Im not sure what you mean by "So it's possible you've hit a combination that emits the escape sequence ^["
I was not pressing anything other than AltGr + Q in the particular linked jpeg. In that scenario I was far away from the ^ key or the AltGr + 8 combination to perform a [ symbol.
I am also far away from these keys in my daily routine where I encounter this issue persistently.
As stated, while testing to debug this behavior, I tried various C0/C1 control codes, like ^[, and non of them exited VT100 mode in the "initramfs" environment (the environment you see in the linked jpeg).

I was not able to exit VT100 except of using AltGr + Shift: But this
method is not 100% reproducible for me as it requires proper timing.
Additionally, within the actual LUKS passphrase, you do not know if you
are in VT100 or not due to the * characters in plymouth - so one can not
assume after AltGr+Q/AltGr+Shift if he entered VT100 and needs to exit
again before continuing with the passphrase.

As mentioned, I have this issue with 2 machines and at least 3 different keyboards (internal and external), since Ubuntu 18!, with various fresh installs. So this behavior is reproducible and not some user error of accidentally having the unlikely combination of keys to enter VT100 or some altered system that causes the behavior.
To repeat myself: It always occurs for me when AltGr + Q or (accidental) AltGr + Shift is involved.

The later, AltGr + Shift, on the other hand is an "unlikely" accident of holding the Shift Key for too long as I need to capitalize the letter of my passphrase before of the @ symbol.
Cheers

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https://bugs.launchpad.net/bugs/2097231

Title:
  LUKS Passphrase: AltGr + Shift Triggers VT100 Pseudographic Mode

Status in cryptsetup package in Ubuntu:
  New
Status in initrd-tools package in Ubuntu:
  New
Status in plymouth package in Ubuntu:
  New

Bug description:
  Hello,

  I have encountered the following issue on Ubuntu 18, 20, and 22, and now again after upgrading to Ubuntu 24, using Ext4 with LUKS.
  Additionally, after performing a fresh install of Ubuntu 24 in October with encrypted ZFS (LUKS), the same issue has reappeared — this time more frequently and nearly “permanently.”

  Regardless of whether I use the laptop’s internal keyboard (HP ProBook 450 G6 or Lenovo Yoga X1 Gen8 — note that I cross-referenced the issue by transferring the SSD between both Laptops) or an external USB keyboard (directly connected or via docking station), the problem remains the same: the input switches to VT100 pseudographics as soon as I press AltGr+Shift, and sometimes I got the impression it happens on my German keyboard layout up on pressing AltGr+Q to produce the “@” symbol.
  This makes it impossible to enter my passphrase.

  On previous versions (e.g., Ubuntu 22 upgraded to 24), rebooting
  usually solved the problem 99% of the time. However, since October it
  takes me over 60 minutes and approximately 30 reboots before I was
  “lucky” enough to input the passphrase and boot the system.

  As a workaround, I created a second LUKS passphrase without the @
  symbol, but I would like to address and resolve the root of the issue.

  I have searched extensively but cannot find any information about this
  specific issue or whether it is expected behavior for initrd/LUKS
  Passhprase environment/Plymouth to allow VT100 mode switching.

  Here is what the issue looks like to me:
  https://ubuntucommunity.s3.us-east-2.amazonaws.com/original/3X/d/e/de7c362f350b7f38e08c9ed2c99b808f969a1289.jpeg

  As you can see, I can press every single key and get the expected
  character. However, as soon as I press AltGr+Q and created the @
  Symbol, it switches to VT100 pseudographics.

  As a user in ubuntu irc suggested, its most likely VT100: https://en.wikipedia.org/wiki/Shift_Out_and_Shift_In_characters
  Neither CTRL+C, ESC, nor SI/SO Key combinations like CTRL+N, CTRL+O, nor C0/C1 control codes like ^N, ^O, ^[, ^X (https://en.wikipedia.org/wiki/C0_and_C1_control_codes) restores regular character input.

  Another Keycombination that activates VT100 is some timing related
  AltGr + Shift. It does not happen when I press both keys longer, but I
  did manage to go in AND out of VT100 Mode by some quick/short
  combination of those.

  May I ask if there is a way to deactivate the VT100 pseudographics
  entirely for initrd, or if this feature could be implemented and be
  set to "off" by default as most users will never make use of this
  feature anyway?

  Thank you

  See previously Ubuntu Discourse post regarding this behaviour:
  https://discourse.ubuntu.com/t/plymouth-luks-passphrase-altgr-q-symbol-or-altgr-shift-triggers-vt100-pseudographic-mode/50746/1
  --- 
  ProblemType: Bug
  ApportVersion: 2.28.1-0ubuntu3.3
  Architecture: amd64
  CasperMD5CheckResult: pass
  CurrentDesktop: ubuntu:GNOME
  DistroRelease: Ubuntu 24.04
  InstallationDate: Installed on 2024-11-13 (81 days ago)
  InstallationMedia: Ubuntu 24.04.1 LTS "Noble Numbat" - Release amd64 (20240827.1)
  NonfreeKernelModules: zfs
  Package: plymouth
  PackageArchitecture: amd64
  ProcVersionSignature: Ubuntu 6.11.0-1013.13-oem 6.11.0
  Tags: noble wayland-session
  Uname: Linux 6.11.0-1013-oem x86_64
  UpgradeStatus: No upgrade log present (probably fresh install)
  UserGroups: adm cdrom dip lpadmin plugdev sudo users
  _MarkForUpload: True
  cmdline: BOOT_IMAGE=/BOOT/ubuntu_n3gtoe@/vmlinuz-6.11.0-1013-oem root=ZFS=rpool/ROOT/ubuntu_n3gtoe ro text
  crypttab: dm_crypt-0 PARTUUID=dbc7a221-c205-4222-a072-098993c914f7 /dev/urandom swap,initramfs,cipher=aes-xts-plain64:sha256,size=512,plain

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