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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 MOJAVE

dnsextd

dnsextd(8)						    BSD System Manager's Manual 						dnsextd(8)

NAME

     dnsextd -- BIND Extension Daemon

SYNOPSIS

     dnsextd

DESCRIPTION

     dnsextd is a daemon invoked at boot time, running alongside BIND 9, to implement two EDNS0 extensions to the standard DNS protocol.

     dnsextd allows clients to perform DNS Updates with an attached lease lifetime, so that if the client crashes or is disconnected from the net-
     work, its address records will be automatically deleted after the lease expires.

     dnsextd allows clients to perform long-lived queries. Instead of rapidly polling the server to discover when information changes, long-lived
     queries enable a client to indicate its interest in some set of data, and then be notified asynchronously by the server whenever any of that
     data changes.

     dnsextd has no user-specifiable command-line argument, and users should not run dnsextd manually.

SEE ALSO

     mDNS(1) mDNSResponder(8)

     For information on Dynamic DNS Update, see RFC 2136 "Dynamic Updates in the Domain Name System (DNS UPDATE)"

     For information on Dynamic DNS Update Leases, see http://files.dns-sd.org/draft-dns-update-leases.txt

     For information on Long-Lived Queries, see http://files.dns-sd.org/draft-dns-llq.txt

BUGS

     dnsextd bugs are tracked in Apple Radar component "mDNSResponder".

HISTORY

     The dnsextd daemon first appeared in Mac OS X 10.4 (Tiger).

Darwin								   June 1, 2019 							    Darwin
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