VSI OpenVMS Forum

Posted: **Tue Sep 19, 2023 2:52 am**

Hi,

Getting this problem when trying to connect from an old 8.4 installation to a new 9.2.1 server.

warning: Authentication failed.
Disconnected; key exchange or algorithm negotiation failed (Algorithm negotiation failed.).

Log from 9.2.1 server

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Unable to negotiate with 192.168.91.85 port 0: no matching cipher found. Their offer: aes128-cbc,3des-cbc,twofish128-cbc,cast128-cbc,twofish-cbc,blowfish-cbc,aes192-cbc,aes256-cbc,twofish192-cbc,twofish256-cbc,arcfour

Tried several configs in SSHD_CONFIG. but with no luck, just results in ssh crashing when it receives a connection.
Anyone has any suggestions on how to get SSH on 9.2.1 to accept old & unsecure encryptions/algorithms ?

Posted: **Wed Sep 20, 2023 4:12 pm**

What modifications did you make to your SSHD_CONFIG file?

Posted: **Thu Sep 21, 2023 2:52 am**

Just did a quick test from

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$ tcpip show version

  HP TCP/IP Services for OpenVMS Alpha Version V5.7
  on an AlphaServer 400 4/166 running OpenVMS V8.4

$ ssh x86vms
   warning: Authentication failed.
Disconnected; key exchange or algorithm negotiation failed (Algorithm negotiation failed.).

Updated TCPIP Services 5.7 to ECO5 and:

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$ tcpip show version

  HP TCP/IP Services for OpenVMS Alpha Version V5.7 - ECO 5
  on an AlphaServer 400 4/166 running OpenVMS V8.4

$ ssh x86vms

 Welcome to OpenVMS (TM) x86_64 Operating System, Version V9.2-1
system's password:

Authentication successful.

For completeness: After the update to ECO5 it has

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$ ssh -h
...
Supported ciphers:

  3des-cbc,aes256-cbc,aes192-cbc,aes128-cbc,aes256-ctr,aes192-ctr,aes128-ctr,
blowfish-cbc,twofish-cbc,twofish256-cbc,twofish192-cbc,twofish128-cbc,
des-cbc@ssh.com,cast128-cbc,rc2-cbc@ssh.com,arcfour,none

Supported MAC algorithms:

  hmac-md5,hmac-md5-96,hmac-sha1,hmac-sha1-96,hmac-sha256@ssh.com,
hmac-sha256-96@ssh.com,hmac-ripemd160@ssh.com,hmac-ripemd160-96@ssh.com,
hmac-tiger128@ssh.com,hmac-tiger128-96@ssh.com,hmac-tiger160@ssh.com,
hmac-tiger160-96@ssh.com,hmac-tiger192@ssh.com,hmac-tiger192-96@ssh.com,none

Posted: **Thu Sep 21, 2023 3:16 am**

Can see that we are running ECO4 on the IA64 server, so updating it to ECO5 probably solves the problem then.
Can´t really update it now since its our build/dev server, so guessing telnet/ftp have to do for now.
Thanks for all the help!
//Niklas

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