[Bug 533352] [NEW] [LUCID] We need "limit" Upstart-ed ssh respawning

[Fumihito YOSHIDA]

*** This bug is a security vulnerability ***

Public security bug reported:

ssh is now handling by upstart native jobs(with /etc/init/ssh.conf
configs), and "respawn" stanza. This is great works. But this behavior
is not familiar for security paranoid.

Scenario:
  - sshd is enougth to berief, but this is not perfect. In future, if we have got vuln for exploiting sshd, that can "randomly" type atacks (e.g.: buffer overflow, it is exploitable with probabilistic atacks, like brute force.).
  - endless respawning is weaken for these "memory address brute force" atacks.

IMHO, when using "respawn" stanza, it needs something "limit" stanza (e.g.: respawn limit 60 30) or any other way ( e.g.: MAC by AppArmor). limitation by "limit" can mitigates(atack speed limitation) probabilistic atacks. This limitation provides potential over-limit DoS, but unlimited respawning is dangerous.
# May be, we have to improvement upstart respawn stanza, like "respawn delay" feature...

....Yes, this wish is not only ssh services. But ssh is most popular +
internet accessible services.

** Affects: openssh (Ubuntu)
     Importance: Undecided
         Status: New

** Visibility changed to: Public

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[LUCID] We need "limit" Upstart-ed ssh respawning
https://bugs.launchpad.net/bugs/533352
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