[Bug 1748310] Re: [SRU][xenial]boot stalls looking for entropy in FIPS mode

[Vineetha Hari Pai]

debdiff.xenial

** Attachment added: "debdiff.xenial"
   https://bugs.launchpad.net/ubuntu/+source/libgcrypt20/+bug/1748310/+attachment/5052125/+files/debdiff.xenial

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Title:
  [SRU][xenial]boot stalls looking for entropy in FIPS mode

Status in libgcrypt20 package in Ubuntu:
  New

Bug description:
  [IMPACT]
  libgcrypt20 is not a FIPS certified library. On a machine running FIPS enabled kernel, the library by default goes into FIPS mode if /proc/sys/crypto/fips_enabled=1. FIPS mode is not a configurable compile option currently in the library. Hence FIPS code paths are always executed on a FIPS enabled machine. In FIPS mode, it runs self tests and integrity checks and it looks for quality entropy from /dev/random.

  On encrypted installations, cryptsetup uses libgcrypt20. During boot
  on an encrypted machine running in FIPS mode, cryptsetup invokes
  libgcrypt and it stalls looking for quality entropy from /dev/random.
  This results in significant delays during startup. The issue was
  reported by a FIPS customer.

  This issue only impacts xenial's version of libgcrypt. In later
  version of libgcrypt in Bionic, the entropy device is a global
  configurable option via /etc/gcrypt/random.conf config file. The
  config setting "only-urandom" can be used to set the entropy device to
  /dev/urandom globally in libgcrypt. So bionic libgcrypt is not
  impacted by this issue.

  lsb_release -rd
  Description:	Ubuntu 16.04.3 LTS
  Release:	16.04

  version - 1.6.5-2ubuntu0.3

  [FIX]
  Get entropy from /dev/urandom device in FIPS mode. This does not block.

  [TEST]
  Tested on a VM installed with xenial desktop iso and one with xenial server iso. Enabled full disk encryption during install. Tested with and without FIPS. Found no delays during boot after the patch fix was applied.

  With FIPS enabled on encrypted install, without the patch fix, the
  boot stalls before and after prompting for decryption password.

  [REGRESSION POTENTIAL]
  The regression potential for this is small. This patch does not take away current functionality. It changes the entropy device in FIPS mode to /dev/urandom to get faster entropy.

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