[Bug 1810235] Re: cryptsetup silently fails in live environment

[Nathan]

Following up and to clarify my initial post a bit, I've found the main
issue is with cryptsetup (or related system) expecting LUKS to be
located within a certain boundary and bcache creates an offset on the
backing drive that shifts this boundary outside where cryptsetup looks.
The package should throw an exception or at the least say it didn't find
the partition but it fails silently and that will require further
investigation.

There is other strange behaviour when working with bcache created
partitions where bcache backed drives have been created but are then
accessed from another computer (where bcache-tools have not been
installed). These include some utilities throwing errors that the device
partition doesn't exist (when it clearly does) and the silent fail with
cryptsetup and devicemapper.

The drive can become accessible by mounting these systems using a loopback offset such as the command below.
losetup -o 8192 /dev/loop8 /dev/sda3 will correct many of these problems.


** Also affects: bcache-tools (Ubuntu)
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/1810235

Title:
  cryptsetup silently fails in live environment

Status in bcache-tools package in Ubuntu:
  New
Status in cryptsetup package in Ubuntu:
  New

Bug description:
  When attempting to acccess an existing (working) LUKS partition from
  the LiveCD environment, cryptsetup fails silently. No exceptions are
  thrown, no errors displayed. The LUKS device remains completely
  inaccessible.

  I've attached an strace with the following two commands, "cryptsetup
  luksDump /dev/sda3", and "cryptsetup luksOpen /dev/sda3 crypted" as
  there was nothing in the logs that clearly point to a problem other
  than the expected result being missing.


  lsb-release:

  DISTRIB_ID=Ubuntu
  DISTRIB_RELEASE=18.04
  DISTRIB_CODENAME=bionic
  DISTRIB_DESCRIPTION="Ubuntu 18.04.1 LTS"

      #uname -a
  Linux ubuntu 4.15.0-29-generic #31-Ubuntu SMP Tue Jul 17 15:39:52 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: cryptsetup 2:2.0.2-1ubuntu1
  ProcVersionSignature: Ubuntu 4.15.0-29.31-generic 4.15.18
  Uname: Linux 4.15.0-29-generic x86_64
  ApportVersion: 2.20.9-0ubuntu7.2
  Architecture: amd64
  CasperVersion: 1.394
  Date: Wed Jan  2 03:56:27 2019
  LiveMediaBuild: Ubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725)
  ProcEnviron:
   TERM=xterm-256color
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=C.UTF-8
   SHELL=/bin/bash
  SourcePackage: cryptsetup
  UpgradeStatus: No upgrade log present (probably fresh install)
  cmdline: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed boot=casper quiet splash ---
  crypttab: # <target name>	<source device>		<key file>	<options>
  fstab:
   overlay / overlay rw 0 0
   tmpfs /tmp tmpfs nosuid,nodev 0 0

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