SSH public key authentication on OpenVMS
Published: 05-04-2018 | Author: Remy van Elst | Text only version of this article
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My OpenVMS adventure continues, after my rabbit hole of folder removal, this time I actually get public key authentication working with OpenSSH so that I don't have to type my password to login.
There is a bit of documentation from HP to set up SSH key authentication but that misses one important little thing. That thing took me a few days to figure out.
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Client public key authentication
On the HPe website there is extensive documentation on both the SSH server setup as well as the client setup on OpenVMS. On the DECUServe system I'm not an administrative user so this article will only cover the client part. It assumes a set up and working SSH server.
SSH public key authentication allows you to login to an SSH server without specifying a password. It is more secure since passwords can easily be brute forced. An SSH key can be securely on a HSM so that the private part never is exposed and SSH keys allow for key forwarding, that means you can use the key from your laptop to login to other servers and then logon further to machines behind there without placing your private key on the intermidiate machines.
Overall SSH keys are considered to be best practice instead of passwords.
Since I access the DECUServe system via SSH with a password I was wondering if OpenVMS would support key authentication and according to the documentation it should just be simple. Place the public key and configure it to allow login.
But sadly that was not all.
Creating the files and folders.
First create an
[SSH2] folder in your homedir:
$ CREATE /DIRECTORY [.SSH2] $ DIR [.SSH2] %DIRECT-W-NOFILES, no files found
Create the configuration file in which we explicitly allow public key authentication next to password login:
$ EVE [.SSH2]SSH2_CONFIG
Place the following line in there:
AllowedAuthentications publickey, password
Directly underneath that the
EVE editor will show this:
[End of file] Buffer: SSH2_CONFIG. | Write | Insert | Forward 1 line read from file EISNER$DRA3:[DECUSERVE_USER.EXAMPLE.SSH2]SSH2_CONFIG.;2
Save the file with
CTRL+Z. As you can see via the
;2 file version number I
was messing around. Did I mention how awesome it is that OpenVMS has file
versioning built in the filesystem?
On linux and other systems that use OpenSSH, you would create
~/.ssh/authorized_keys and place your key(s) in there like so:
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCq1vxYvJNBZMtrufZD0ivHXrt0A+WhslMcWeQTU2du2jznw64ScrxN+EYXVGg3JKu8N/QK/0VrtsxITFthHJQP0FkC0J8GnWeT3x2y0N38P+H3B/h1rh9DBY/GTUlXY9Q0MKAOEdTjSecK11Nd5183Xcygnv5xAxLqzqmnllumAE1Wd/B0NoKrcSy51hERn0kKTR9hIw8FTOUNPAwTgsMJ+A10aJtqjlk4OrOd1KOHi1jWNTc5wcW6xgWzMksdw++fBBPcJN9Bgihxz9kSwdpkcIYlBkIZZEwZtTvNy7K2nKw94omWmdr0ZlqsNwfOihyQpo4wtusjakTmM4GA+bH3 remy@gateway
On OpenVMS, you create a file named
AUTHORIZATION and in there you specify
filenames of public keys, like
KEY EXAMPLE-HOSTNAME.PUB where
HOSTNAME.PUB is the file name with the format
EVE to create this
AUTHORIZATION. file and add the filename of your
public key file:
$ EVE [.SSH2]AUTHORIZATION
My key example:
Note, do not add the key here like you might be used to on linux, just make up a
filename, prefixed with
KEY. Next create the actual key file:
$ EVE [.SSH2]REMY-GATEWAY.PUB
Paste your public key and save with
The documentation states that the public key file requires specific permission.
On linux I'm used to setting permissions on the
authorized_keys file and the
private key material, but this will be comparable I guess:
SET FILE /PROTECTION=(S:WRED,O:WRED,G:RE,W:R) [.SSH2]REMY-GATEWAY.PUB
You can check the current permissions with the
SHOW SECURITY command:
$ SHOW SECURITY [.SSH2]REMY-GATEWAY.PUB EISNER$DRA3:[DECUSERVE_USER.EXAMPLE.SSH2]REMY-GATEWAY.PUB;2 object of class FILE Owner: [EXAMPLE] Protection: (System: RWED, Owner: RWED, Group: RE, World: R) Access Control List: <empty>
By default, or at least on DECUServe my files get the following permissions:
Protection: (System: RWED, Owner: RWED, Group, World)
Now you should be all set to go. Login specifically disabling password login using your key:
$ ssh -oHostKeyAlgorithms=+ssh-dss -o "PasswordAuthentication no" EXAMPLE@eisner.decus.org
The authenticity of host 'eisner.decus.org (184.108.40.206)' can't be established. DSA key fingerprint is SHA256:S0vOOBec5QvjeC1aLvnSccBewSgOvsF2s97KGaY1pnE. Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added 'eisner.decus.org,220.127.116.11' (DSA) to the list of known hosts. N O T I C E This is Encompasserve. Access is for subscribed individuals only. o By logging into the system you agree to abide by the Encompasserve Canons of Conduct. o Source code or any other information posted on this system is not warranted in any way. YOU USE IT AT YOUR OWN RISK. o If you submit source code to or post information on this system, you must allow its unrestricted use. You must have the right to grant such permission. o Refer to the Encompasserve Canons of Conduct, posted in the DECUServe_Information conference topic 4.3, for further guidance. o Report problems in DECUServe_Forum. For information about Encompasserve please login under -> Username INFORMATION To subscribe to Encompasserve please login under -> Username REGISTRATION To report any form of a problem please login under -> Username PROBLEMS To renew an Expired account please login under -> Username REGISTRATION Permission denied (publickey,password).
Err, what? We followed the documentation to the letter?
Why does it not work?
This problem took me a few days to resolve. As I have no access to logging on the OpenVMS system and no knowledge of how to view said logging, I was left to trial and error.
To save you time and trouble, it appears that the key file was not in the
correct format for OpenVMS. We pasted the OpenSSH key format in the key file but
there is another format. I found this on a USENET newsgroup, you know you're far
in the exotic corners of the internet when you're searching
hey, it helped me solve this issue.
The DECUServe system does not have the
SSH-KEYGEN OpenVMS program installed or
at least I got an error when trying to execute it. Otherwise I would have tried
to create a key there and compare the files and permissions with my own file.
OpenSSH uses, suprisingly,
openssh format public keys. The ones you know and
probably 99% of the regular internet uses. But as always there are special
snowflakes and it seems this is one of them. Googling around also gave lot's of
hits for IBM and
ssh-keygen (on linux) we can convert a private key to this format with
-e option. From the man page:
-e Extract/convert from OpenSSH private key file to SECSH public key format
In my case:
$ ssh-keygen -e -f ~/.ssh/id_rsa
---- BEGIN SSH2 PUBLIC KEY ---- Comment: "2048-bit RSA, converted by remy@gateway from OpenSSH" AAAAB3NzaC1yc2EAAAADAQABAAABAQCq1vxYvJNBZMtrufZD0ivHXrt0A+WhslMcWeQTU2 du2jznw64ScrxN+EYXVGg3JKu8N/QK/0VrtsxITFthHJQP0FkC0J8GnWeT3x2y0N38P+H3 B/h1rh9DBY/GTUlXY9Q0MKAOEdTjSecK11Nd5183Xcygnv5xAxLqzqmnllumAE1Wd/B0No KrcSy51hERn0kKTR9hIw8FTOUNPAwTgsMJ+A10aJtqjlk4OrOd1KOHi1jWNTc5wcW6xgWz Mksdw++fBBPcJN9Bgihxz9kSwdpkcIYlBkIZZEwZtTvNy7K2nKw94omWmdr0ZlqsNwfOih yQpo4wtusjakTmM4GA+bH3 ---- END SSH2 PUBLIC KEY ----
Use the editor to update your KEY file on OpenVMS, in my case
GATEWAY.PUB. Save with
CTRL+Z and retry:
$ ssh -oHostKeyAlgorithms=+ssh-dss -o "PasswordAuthentication no" -i .ssh/id_rsa EXAMPLE@eisner.decus.org
N O T I C E This is Encompasserve. Access is for subscribed individuals only. o By logging into the system you agree to abide by the Encompasserve Canons of Conduct. o Source code or any other information posted on this system is not warranted in any way. YOU USE IT AT YOUR OWN RISK. o If you submit source code to or post information on this system, you must allow its unrestricted use. You must have the right to grant such permission. o Refer to the Encompasserve Canons of Conduct, posted in the DECUServe_Information conference topic 4.3, for further guidance. o Report problems in DECUServe_Forum. For information about Encompasserve please login under -> Username INFORMATION To subscribe to Encompasserve please login under -> Username REGISTRATION To report any form of a problem please login under -> Username PROBLEMS To renew an Expired account please login under -> Username REGISTRATION Last interactive login on Thursday, 5-APR-2018 14:10:22.71 %DCL-S-SPAWNED, process EXAMPLE_62002 spawned User [EXAMPLE] has 132 blocks used, 9868 available, of 10000 authorized and permitted overdraft of 0 blocks on DISK_USER $ Subprocess EXAMPLE_62002 has completed $
I learned a lot, again. I notice that filesystem actions like editing and permissions are a bit easier for me since I'm beginning to grasp the concepts and commands. To summarize:
- OpenVMS supports public key authentication
- It's almost the same as with OpenSSH on Linux
- Define your public key in an
AUTHORIZATIONfile and place the key on the system
- Make sure it is the correct key format
- Set the correct permissions
One more thing, LOGOUT of OpenVMS
In an earlier article I wrote that I was unable to logout on OpenVMS since
CTRL+D not exited the SSH session. I stopped my sessions using
~. or by closing the window.
In the same
comp.os.vms I found the
LOG command. The help says:
$ HELP LOG [...] LOGOUT Terminates an interactive terminal session. Format LOGOUT
So, now I can type 'LOG' on the prompt and exit OpenVMS.Tags: alpha , blog , dec , decus , itanium , openvms , pdp , simh , vax , vms