[Bug 1088611] [NEW] using random hostnames to detect dns proxies allows for false positives

[Steve Langasek]

Public bug reported:

The fix that's been applied for bug #974509 checks for the presence of a
redirector by looking of three hostnames, and treating as invalid any
results pointing to a matching address:

 - does-not-exist.example.com.
 - example.invalid.
 - a random, unqualified 32-character alphanumeric hostname.

The last of these carries a small but non-zero risk of colliding with a
real hostname, and there's a small but non-zero risk that this host
points to the same address as something we care about.  If possible, it
would be better to not include this random-host lookup in the algorithm,
as somewhere, some day, chances are there will eventually be a
collision, causing an incomprehensible and unreproducible failure for a
user.

** Affects: cloud-init (Ubuntu)
     Importance: Undecided
         Status: New

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Title:
  using random hostnames to detect dns proxies allows for false
  positives

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