[Bug 1996639] [NEW] Ubuntu Server installer mistreats hostname special characters

[Dominik Szymański]

Public bug reported:

TL;DR;: Installer trimmed bad characters from hostname, but put my input
literally into /etc/hosts

I was installing Ubuntu Server in vmware from freshly downloaded ISO from your webpage.
`lsb_release -rd` output after finish:
Description:	Ubuntu 22.04.1 LTS
Release:	22.04

CRC32 of image: 3d73cc1f

It asked me to update installer so I did (not sure which exactly version
it was).

After some steps of me not choosing any extra packages, formatting whole
drive, selecting network showed up form to put in my name, hostname,
username and password.

Into the hostname field I've put:

mac_ubuntu

Nothing complained so I went with it no problem (although I think
"Installing kernel" step took weirdly lot of time, but that might be
unconnected).

After install I logged in into SSH and noticed prompt being:

dominik at macubuntu:~$

So I though: no biggie, it trimmed the chars it didn't like, and that's
probbaly what happened.

However I noticed `sudo` taking long time. Little search pointed me to
the answer, that `/etc/hosts` file might be missing 127.0.0.1 entry for
my hostname, and so it ended up being!

Result of `hostname`:

macubuntu

Contents of `/etc/hosts`:

127.0.0.1 localhost
127.0.1.1 mac_ubuntu

# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters


And as you can see, entry for 127.0.1.1 is what I've originally put into the installer form, not what machine thinks hostname is.
After adding entry:

127.0.0.1 macubuntu

Sudo started behaving.

It's most probably low priority issue, affecting slim percentage of
people, but sanitizing input or even validating that user puts only
allowed chars in there could be a great idea.

** Affects: debian-installer (Ubuntu)
     Importance: Undecided
         Status: New

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to debian-installer in Ubuntu.
https://bugs.launchpad.net/bugs/1996639

Title:
  Ubuntu Server installer mistreats hostname special characters

Status in debian-installer package in Ubuntu:
  New

Bug description:
  TL;DR;: Installer trimmed bad characters from hostname, but put my
  input literally into /etc/hosts

  I was installing Ubuntu Server in vmware from freshly downloaded ISO from your webpage.
  `lsb_release -rd` output after finish:
  Description:	Ubuntu 22.04.1 LTS
  Release:	22.04

  CRC32 of image: 3d73cc1f

  It asked me to update installer so I did (not sure which exactly
  version it was).

  After some steps of me not choosing any extra packages, formatting
  whole drive, selecting network showed up form to put in my name,
  hostname, username and password.

  Into the hostname field I've put:

  mac_ubuntu

  Nothing complained so I went with it no problem (although I think
  "Installing kernel" step took weirdly lot of time, but that might be
  unconnected).

  After install I logged in into SSH and noticed prompt being:

  dominik at macubuntu:~$

  So I though: no biggie, it trimmed the chars it didn't like, and
  that's probbaly what happened.

  However I noticed `sudo` taking long time. Little search pointed me to
  the answer, that `/etc/hosts` file might be missing 127.0.0.1 entry
  for my hostname, and so it ended up being!

  Result of `hostname`:

  macubuntu

  Contents of `/etc/hosts`:

  127.0.0.1 localhost
  127.0.1.1 mac_ubuntu

  # The following lines are desirable for IPv6 capable hosts
  ::1     ip6-localhost ip6-loopback
  fe00::0 ip6-localnet
  ff00::0 ip6-mcastprefix
  ff02::1 ip6-allnodes
  ff02::2 ip6-allrouters

  
  And as you can see, entry for 127.0.1.1 is what I've originally put into the installer form, not what machine thinks hostname is.
  After adding entry:

  127.0.0.1 macubuntu

  Sudo started behaving.

  It's most probably low priority issue, affecting slim percentage of
  people, but sanitizing input or even validating that user puts only
  allowed chars in there could be a great idea.

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/debian-installer/+bug/1996639/+subscriptions