[Bug 1783810] Re: [SRU] blocks boot on core18

[Michael Vogt]

Thanks for your careful review Robie! As far as security is concerned, upstream comments on this in edc1c90cb972fdca1f66be5a8e2b0706bd2a4949:
"""
   Note that we do not use random numbers for security sensitive things
   like keys or so. It's used for random based UUIDs etc.
"""

I looked at the util-linux source and it is used in:
* dos.c: create a random disk ID
* ipcmk.c: create shared memory segments with a random key
* gen_uuid.c: generate UUIDs
* mcookie.c: to generate 128bit random numbers for xauth but the man-page warns that the randomness of this may come from the libc pseudo-random functions

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https://bugs.launchpad.net/bugs/1783810

Title:
  [SRU] blocks boot on core18

Status in util-linux package in Ubuntu:
  Fix Released
Status in util-linux source package in Bionic:
  Fix Committed

Bug description:
  The current version of libuuid is using getrandom() without the
  GRND_NONBLOCK flag. This means that in early boot the boot is blocked
  until the crng is initialized to "level=1" which on virtual machines
  may take some time.

  Upstream fixed this in https://github.com/karelzak/util-
  linux/commit/a9cf659e0508c1f56813a7d74c64f67bbc962538 and we should
  just backport the fix.

  [Impact]
   * Makes systems that use libuuid in early boot hang

  [Test Case]
   * boot a fresh core18 system with kernel 4.15

  [Regression Potential]
   * little, change is very targeted

  This is uploaded to the bionic-proposed queue now.

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