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https://issues.apache.org/jira/browse/GUACAMOLE-547?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16881714#comment-16881714
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Michael Jumper edited comment on GUACAMOLE-547 at 7/10/19 4:19 AM:
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{quote}
... loop with a _Handler not found for "nop"_ message.
{quote}
This is unrelated to SSH and isn't a loop nor a bug. The "nop" message is sent
by the client to the server as a sort of keep-alive ping. Since the "nop"
instruction doesn't do anything by definition, the server doesn't actually
implement a handler for it. Recent changes from GUACAMOLE-422 added a
debug-level message to let us know if an instruction is not handled because it
has no handler, as that may indicate an incompatibility between client and
server that's worth noting, but in this case it's just benign noise.
was (Author: mike.jumper):
{quote}
... loop with a _Handler not found for "nop"_ message.
{quote}
This is unrelated to SSH and isn't a loop nor a bug. The "nop" message is sent
by the client to the server as a sort of keep-alive ping. Since the "nop"
instruction doesn't do anything by definition, the server doesn't actually
implement a handler for it. Recent changes from GUACAMOLE-422 added a
debug-level message to let us know if an instruction is not handled because it
has no handler, as that may indicate an incompatibility between client and
server that's worth noting, but this in this case it's just benign noise.
> Add support for the "none" SSH authentication method
> ----------------------------------------------------
>
> Key: GUACAMOLE-547
> URL: https://issues.apache.org/jira/browse/GUACAMOLE-547
> Project: Guacamole
> Issue Type: New Feature
> Components: Documentation, SSH
> Environment: Linux 4.13.0-1012-azure #15-Ubuntu SMP Thu Mar 8
> 10:47:27 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
> Reporter: David Hauk
> Assignee: Michael Jumper
> Priority: Minor
> Fix For: 1.1.0
>
> Attachments: guacd-1.0.0.log, guacd-master.log, guacd_debug_fail.txt,
> openssh_verbose_successful connection.txt, sshd_config
>
>
> When connecting to embedded devices that implicitly allow SSH access guacd
> fails when the authentication method is (none). The devices permit any SSH
> user with no password access to the console, and then provide authentication
> internally via their interactive shell.
> Test cases:
> # no username and no password configured: Guacamole requests both, then
> fails to connect.
> # username but no password: Guacamole requests password, and then fails to
> connect.
> # username and password: Guacamole asks for no input, and then fails to
> connect.
> I've attached guacd debug logs from the failed connection attempts, plus
> OpenSSH (-vv) logs from a successful connection. (Files have been suitably
> redacted). The bit they share in common is they both state "Authentication
> (none)" but OpenSSH proceeds with the connection, while guacd terminates the
> connection:
> Guacd:
> {code:java}
> guacd[100079]: DEBUG: Successfully connected to host 192.168.233.20, port 22
> guacd[100079]: DEBUG: Supported authentication methods: (null)
> guacd[100066]: INFO: Connection "$abc52848-a11c-4397-a657-7c2d4bfdb5e9"
> removed.{code}
> OpenSSH:
> {code:java}
> debug1: SSH2_MSG_SERVICE_ACCEPT received
> debug1: Authentication succeeded (none).
> Authenticated to 192.168.233.20 ([192.168.233.20]:22).
> debug1: channel 0: new [client-session]
> debug2: channel 0: send open
> {code}
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