Troubleshooting guide

Troubleshooting guide#

Error Host key verification failed. + SSH Monitor Error:...#

If you get the following error message in the IOC Shell, when initializing the IOC program:

...
Host key verification failed.
SSH Monitor ERROR: the full SSH command including the shell instruction (<...>) returns an error when executed!
...
Host key verification failed.
SSH Monitor ERROR: the full SSH command including the shell instruction (<...>) returns an error when executed!
...
Host key verification failed.
SSH Monitor ERROR: the full SSH command including the shell instruction (<...>) returns an error when executed!
...
Host key verification failed.
SSH Monitor ERROR: the full SSH command including the shell instruction (<...>) returns an error when executed!
...

This is probably because the target is not a “known SSH host” of the host.

Try to SSH to the target from the host, with the same user used by your SSH Monitor IOC program (e.g. sshmonitor-user):

host-pc $ echo $USER
    sshmonitor-user

host-pc $ ssh sshmonitor-user@192.168.2.3

At this point, you will be asked if you want to continue (yes) in order to consider the target as a “known SSH host”:

The authenticity of host '192.168.2.3 (<no host ip for proxy command>)' can't be established.
ECDSA key fingerprint is SHA256:4ohcHl4WVPwNL3U4FAsy+TWf7T8i/ziBLIdstgqFhsU.
This key is not known by any other names.
Are you sure you want to continue connecting (yes/no/[fingerprint])?
    > yes
Warning: Permanently added '192.168.2.3' (ECDSA) to the list of known hosts.

Now you should just have to restart the IOC program, and the error messages should have disappear.

If the error still occurs, then another possible explanation is that the SSH_OPTS_AND_ARGS macro
– specified in the .cmd file – contains e.g. a syntax error.

Error Connection closed by UNKNOWN port 65535#

If you get the following error message in the IOC Shell:

...
Jan 1 00:00:00 ioc-name procServ[123456]: Connection closed by UNKNOWN port 65535
Jan 1 00:00:00 ioc-name procServ[123456]: Connection closed by UNKNOWN port 65535
Jan 1 00:00:00 ioc-name procServ[123456]: Connection closed by UNKNOWN port 65535
Jan 1 00:00:00 ioc-name procServ[123456]: Connection closed by UNKNOWN port 65535
Jan 1 00:00:00 ioc-name procServ[123456]: Connection closed by UNKNOWN port 65535
...

This is probably because your are using a intermediate machine as a “jump” machine in order to reach a target, but the host cannot connect through the intermediate machine anymore.

Make sure that the intermediate machine is not down, that it’s firewall configuration is OK, that the network between the host and the intermediate machine is not down and allows the connection, etc.

Message muxclient: master hello exchange failed#

When running your IOC program, if you encounter the following message:

muxclient: master hello exchange failed

then you can ignore it.

This is a quite rare message that might be due to the fact that the user running the IOC program
is forwarding an ssh-agent with more than one SSH key (probably only in some virtualized environments).

See the first note of section 5.1 of the following link: 20241007123652/https://docs.releng.linuxfoundation.org/_/downloads/common-packer/en/latest/pdf/

To get rid of this message, just make sure that the user running the IOC program is not himself accessed through an SSH connection forwarding an ssh-agent.

Message ControlSocket $HOME/.ssh/<...> already exists, disabling multiplexing#

When running your IOC program, if you encounter the following message:

ControlSocket $HOME/.ssh/<...> already exists, disabling multiplexing

Then you can change the SSH_OPTS_AND_ARGS macro in your .cmd file, in order for the ControlPersist option to be set to a longuer duration, longer than the SCAN_MACRO macro (if specified in the .cmd) or the default SCAN macro (specified in the .substitutions).

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