[Bug 483928]

[Daniel Richard G.]

Okay, I tried Ubuntu's packaging of OpenSSH (version 1:5.8p1-7ubuntu1)
with your patch, and it powered through everything. Here is a list of
all the error messages I received:

A.B.C.D: Connection closed by remote host
Connection closed by A.B.C.D
Connection to A.B.C.D timed out while waiting to read
Received disconnect from A.B.C.D: 10:  Protocol error
Received disconnect from A.B.C.D: 10:  Protocol error
Received disconnect from A.B.C.D: 11:  SSH Disabled
Received disconnect from A.B.C.D: 2: Client Disconnect
Received disconnect from A.B.C.D: 2: Protocol Timeout
connect (`A.B.C.D'): Network is unreachable
no 'ssh-rsa' hostkey alg(s) for A.B.C.D
read (A.B.C.D): Connection reset by peer
read (A.B.C.D): No route to host

(This is ssh-keyscan output with /^#.*$/ filtered out, all IPs zapped,
and 'sort -u'd)

Now the question is, why hasn't this been checked in already! (Have you
tried making some noise on the mailing list?)

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https://bugs.launchpad.net/bugs/483928

Title:
  ssh-keyscan(1) exits prematurely on some non-fatal errors

Status in Portable OpenSSH:
  Confirmed
Status in “openssh” package in Ubuntu:
  Confirmed

Bug description:
  Binary package hint: openssh-client

  This concerns openssh-client 1:5.1p1-5ubuntu1 in Karmic.

  I am using ssh-keyscan(1) for its intended purpose: building an
  ssh_known_hosts file for a large network. Most of the hosts on this
  network are well-maintained systems, with properly-functioning SSH
  servers, and present no difficulty to the program.

  However, a handful of hosts are barely alive, with SSH servers that
  are not exactly in good working order. ssh-keyscan(1) currently will
  scan these systems, encounter some form of error, and then---right
  here is the problem---exit in the middle of the scan. The last bit of
  stderr output may look like

  	# A.B.C.D SSH-2.0-OpenSSH_4.3
  	# A.B.C.E SSH-2.0-OpenSSH_4.3
  	# A.B.C.F SSH-1.99-OpenSSH_3.7p1
  	Connection closed by A.B.C.F

  or

  	# A.B.C.D SSH-2.0-OpenSSH_4.1
  	# A.B.C.E SSH-2.0-OpenSSH_4.1
  	# A.B.C.F SSH-2.0-mpSSH_0.1.0
  	Received disconnect from A.B.C.F: 10:  Protocol error

  or

  	# A.B.C.D SSH-2.0-OpenSSH_4.4p1
  	# A.B.C.E SSH-2.0-OpenSSH_5.0p1
  	# A.B.C.F SSH-2.0-mpSSH_0.1.0
  	Received disconnect from A.B.C.F: 11:  SSH Disabled

  (These are the different failure modes I've observed to date)

  ssh-keyscan(1) needs to be robust to these kinds of errors---simply
  make a note of them, and continue on with the scan. I don't want to
  have to find out which systems are misbehaving by running and re-
  running the scan (each run yields at most one bad host, obviously),
  nor manually edit out the few bad apples from the input list of hosts
  (especially considering that this particular subset can change over
  time). Neither is feasible when the number of hosts being scanned is
  very large.

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