[RndTbl] sshd: Corrupted MAC on input.

Gilbert E. Detillieux gedetil at cs.umanitoba.ca
Wed Jul 29 11:37:17 CDT 2020

I've been getting errors such as the following on one of my systems 

Jul 29 11:15:33 localhost sshd[26456]: Corrupted MAC on input.
Jul 29 11:15:33 localhost sshd[26456]: ssh_dispatch_run_fatal: 
Connection from port 61436: message authentication code 

These tend to happen during large rsync runs, which causes rsync to abort.

Following some advice I found on The Google, I tried setting various 
different values for the "MACs" keyword in sshd_config, but it doesn't 
seem to change the behaviour.  (And, yes, I did remember to restart the 
sshd service after each config change.  Running "ssh -vvv" to the host 
shows that it's negotiating the new MAC protocol.)

What's the likely cause of this?  A bad NIC?  Bad RAM?  (I'm guessing 
something is corrupting the packets once in a while, but I'm not sure 
what.  If so, it seems to get past TCP's error correcting.)

Has anyone else come across this before, and have a suggestion?


Gilbert E. Detillieux        E-mail:  <gedetil at cs.umanitoba.ca>
Dept. of Computer Science    Web:     http://www.cs.umanitoba.ca/~gedetil/
University of Manitoba       Phone:   (204)474-8161
Winnipeg MB CANADA  R3T 2N2  Fax:     (204)474-7609

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