deb-package breaks apt/dpkg on dash-shell Linux OS

[ChaosNicro]

What Operating System

Linux (Other)

Debug Code

https://pste.ch/abaligujen

Describe the bug

Installed from ftb-app-1.26.5-amd64.deb.
After installation the app runs, but apt/dpkg will set it as half-installed and continually error when installing or removing packages from that point on.
"dpkg (subprocess): unable to execute installed ftb-app package post-removal script (/var/lib/dpkg/info/ftb-app.postrm): No such file or directory
dpkg: error processing package ftb-app (--remove):
installed ftb-app package post-removal script subprocess returned error exit status 2
dpkg: too many errors, stopping
Errors were encountered while processing:
ftb-app
Processing was halted because there were too many errors.
E: Sub-process /usr/bin/dpkg returned an error code (1)
"
The package can not be removed or automatically fixed.

The cause of this, is that the postrm-script contains Windows-style line-endings, that mangle the bash commands for removing the app from /usr/bin.
In bash-proper this is ignored, in alternatives like dash, this breaks the script.
I understand that this affects a negligible amount of users, but it may be an easy fix.
The other scripts seem to use Unix line-endings, so I wonder why the postrm-script differs.

Could you please review the build-process and ensure that scripts are formatted for Unix.

Steps to reproduce

1. Use a dash-shell Linux OS (Tuxedo OS in my case).
2. Install the app.
3. Observe that "apt install" now lists the ftb-app as "to be installed".
4. Attempt to remove the ftb-app.
5. Observe the error described above.

Expected behaviour

The app can be installed and removed at will, without corrupting the dpkg-state.

Screenshots

No response

Additional information

No response

[nZpUhsX]

this doesn't appear to be limited to just dash. i just ran into the same issue with version 1.27.2 on linux mint 21.3 with bash. all i did was install the .deb file, run the program to make sure it worked then tried to purge it.

mint21vm@mint21vm:~$ bash /var/lib/dpkg/info/ftb-app.postrm 
/var/lib/dpkg/info/ftb-app.postrm: line 2: $'\r': command not found
/var/lib/dpkg/info/ftb-app.postrm: line 9: syntax error: unexpected end of file
mint21vm@mint21vm:~$ apt list ftb-app
Listing... Done
ftb-app/now 1.27.2 amd64 [installed,local]
mint21vm@mint21vm:~$ sudo apt purge ftb-app
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following packages will be REMOVED:
  ftb-app*
0 upgraded, 0 newly installed, 1 to remove and 6 not upgraded.
After this operation, 299 MB disk space will be freed.
Do you want to continue? [Y/n] y
(Reading database ... 674476 files and directories currently installed.)
Removing ftb-app (1.27.2) ...
dpkg (subprocess): unable to execute installed ftb-app package post-removal script (/var/lib/dpkg/info/ftb-app.postrm): No such file or directo
ry
dpkg: error processing package ftb-app (--remove):
 installed ftb-app package post-removal script subprocess returned error exit status 2
dpkg: too many errors, stopping
Errors were encountered while processing:
 ftb-app
Processing was halted because there were too many errors.
E: Sub-process /usr/bin/dpkg returned an error code (1)
mint21vm@mint21vm:~$ ls -l /var/lib/dpkg/info/ftb-app.postrm
-rwxr-xr-x 1 root root 202 Feb  1 12:16 /var/lib/dpkg/info/ftb-app.postrm
mint21vm@mint21vm:~$ file /var/lib/dpkg/info/ftb-app.postrm 
/var/lib/dpkg/info/ftb-app.postrm: Bourne-Again shell script, ASCII text executable, with CRLF line terminators

the reason i tested it: https://forums.linuxmint.com/viewtopic.php?t=439536

[rikkathehare]

Hi there! I'm the person who created the forum topic that user nZpUhsX linked. I'm just gonna copy the solution here just in case someone else sees this bug ticket before the issue is resolved.

I revised ftb-app.postrm located in /var/lib/dpkg/info by changing the line ending option to "Unix/Linux" using the following command:

xed admin:///var/lib/dpkg/info/ftb-app.postrm

After that apt still didn't want to remove the package, but dpkg with the force argument was successful:

my_irl_name:/$ xed admin:///var/lib/dpkg/info/ftb-app.postrm
my_irl_name:/$ sudo apt remove ftb-app
[sudo] password for my_irl_name:          
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
E: The package ftb-app needs to be reinstalled, but I can't find an archive for it.

my_irl_name:/$ sudo dpkg --remove --force-remove-reinstreq ftb-app
dpkg: warning: overriding problem because --force enabled:
dpkg: warning: package is in a very bad inconsistent state; you should
 reinstall it before attempting a removal
(Reading database ... 606037 files and directories currently installed.)
Removing ftb-app (1.26.5) ...
update-alternatives: warning: alternative /opt/FTB Electron App/ftb-app (part of link group ftb-app) doesn't exist; removing from list of alternatives
update-alternatives: warning: /etc/alternatives/ftb-app is dangling; it will be updated with best choice

After that, I cleaned up the config files with:

sudo apt purge ftb-app

And the package is totally gone! Using the following command returns 0 hits:

apt list | grep ftb-app