key generation fails if hostname length > 31 chars

[Ryan Amick]

key generation fails if short hostname length > 31 chars

failed on install with apt in terminal. My computer had froze while on browser. i had to hard reset, then i did update then upgrade. tried upgrade -f

ProblemType: Package
DistroRelease: Ubuntu 18.04
Package: shim-signed 1.34.1+13-0ubuntu2
ProcVersionSignature: Ubuntu 4.15.0-15.16-generic 4.15.15
Uname: Linux 4.15.0-15-generic x86_64
.proc.sys.kernel.moksbstate_disabled: Error: [Errno 2] No such file or directory: '/proc/sys/kernel/moksbstate_disabled'
ApportVersion: 2.20.9-0ubuntu6
Architecture: amd64
Date: Fri Apr 20 20:45:53 2018
ErrorMessage: installed shim-signed package post-installation script subprocess returned error exit status 1
InstallationDate: Installed on 2018-02-10 (70 days ago)
InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Release amd64 (20180105.1)
Python3Details: /usr/bin/python3.6, Python 3.6.5, python3-minimal, 3.6.5-3
PythonDetails: /usr/bin/python2.7, Python 2.7.15rc1, python-minimal, 2.7.15~rc1-1
RelatedPackageVersions:
 dpkg 1.19.0.5ubuntu2
 apt 1.6.1
SecureBoot: 6 0 0 0 0
SourcePackage: shim-signed
Title: package shim-signed 1.34.1+13-0ubuntu2 failed to install/upgrade: installed shim-signed package post-installation script subprocess returned error exit status 1
UpgradeStatus: No upgrade log present (probably fresh install)

[Steve Langasek (vorlon)]

From the dpkg log:

problems making Certificate Request
140700872008128:error:0D07A097:asn1 encoding routines:ASN1_mbstring_ncopy:string too long:../crypto/asn1/a_mbstr.c:109:maxsize=64

from dmesg:

[ 19.639051] systemd[1]: Set hostname to <finisdiem-HP-Pavilion-g6-Notebook-PC>.

This definitely causes the openssl req option, -subj "/CN=`hostname -s` Secure Boot Module Signature key", to exceed 64 bytes.

We should probably just take the first 31 bytes of the hostname.

[Steve Langasek (vorlon)]

Fixed in 1.34.3 in bionic-proposed. Since this bug has only ever been in -proposed, marking this fix-released.

shim-signed (1.34.3) bionic; urgency=medium

  * Only take the first 31 bytes of the hostname. LP: #1765905.