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Full Discussion: Change from weak ssh host key to strong one
Operating Systems Solaris Change from weak ssh host key to strong one Post 303036682 by rbatte1 on Monday 8th of July 2019 05:35:10 AM
Old 07-08-2019
Just came across this. One thing to be aware of is that all clients will object when you next try to connect them. They will alert on there being a possible man-in-the-middle attack or a DNS attack that is trying to send you to a different host (as determined by the keys) so you would need to get each client to forget the server keys for the machine(s) you are replacing the keys on and re-validate them all, or manually replace the old key with the new on all the clients.

You need to consider all the names that the clients could refer to the server as, be that IP, local hosts, DNS short name, fully qualified DNS name, DNS alias etc. and look for those in ~/.ssh/known_hosts

You will need to do this for every account on every client, so it is not a thing to be done lightly, especially if there are multiple automated jobs that connect with SSH, SCP, SFTP etc. that you need to ensure are not disrupted.


Sorry if I've made you panic, but better that than a massive failure.



I hope that this helps,
Robin
 

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LEARN ABOUT DEBIAN

sss_ssh_knownhostsproxy

SSS_SSH_KNOWNHOSTSPR(1) 					 SSSD Manual pages					   SSS_SSH_KNOWNHOSTSPR(1)

NAME

       sss_ssh_knownhostsproxy - get OpenSSH host keys

SYNOPSIS

       sss_ssh_knownhostsproxy [options] HOST [PROXY_COMMAND]

DESCRIPTION

       sss_ssh_knownhostsproxy acquires SSH host public keys for host HOST, stores them in a custom OpenSSH known_hosts file (see the
       "SSH_KNOWN_HOSTS FILE FORMAT" section of sshd(8) for more information) /var/lib/sss/pubconf/known_hosts and estabilishes connection to the
       host.

       If PROXY_COMMAND is specified, it is used to create the connection to the host instead of opening a socket.

       ssh(1) can be configured to use sss_ssh_knownhostsproxy for host key authentication by using the following directives for ssh(1)
       configuration:

	   ProxyCommand /usr/bin/sss_ssh_knownhostsproxy -p %p %h
	   GlobalKnownHostsFile2 /var/lib/sss/pubconf/known_hosts

	This is an experimental feature, please use http://fedorahosted.org/sssd to report any issues.

OPTIONS

       -p,--port PORT
	   Use port PORT to connect to the host. By default, port 22 is used.

       -d,--domain DOMAIN
	   Search for host public keys in SSSD domain DOMAIN.

       -h,--help
	   Display help message and exit.

SEE ALSO

       ssh(8), ssh_config(5), sss_ssh_authorizedkeys(1).

AUTHORS

       The SSSD upstream - http://fedorahosted.org/sssd

SSSD
								    03/04/2013						   SSS_SSH_KNOWNHOSTSPR(1)
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