This is a text-only version of the following page on https://raymii.org:

This is a text-only version of the following page on https://raymii.org:
---
Title : SSH public key authentication on OpenVMS
Author : Remy van Elst
Date : 05-04-2018
URL : https://raymii.org/s/blog/SSH_public_key_authentication_on_OpenVMS.html
Format : Markdown/HTML
---

[![openvms][1]][2]

(You can read all my OpenVMS articles by [clicking the picture (above][2])

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][4] on both the SSH server
setup as well as the client setup on OpenVMS. On the [DECUServe][5] 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][6] 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][5] system via SSH with a password I was wondering
if OpenVMS would support key authentication and [according to the
documentation][7] 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 `EXAMPLE-
HOSTNAME.PUB` is the file name with the format `$USER-$HOST.PUB`.

Use `EVE` to create this `AUTHORIZATION.` file and add the filename of your
public key file:

$ EVE [.SSH2]AUTHORIZATION

My key example:

KEY REMY-GATEWAY.PUB

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 `CTRL+Z`.

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" [email protected]

Output:

The authenticity of host 'eisner.decus.org (104.207.199.162)' 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,104.207.199.162' (DSA) to the list of known hosts.

N O T I C E

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o By logging into the system you agree to abide by the Encompasserve
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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.

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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 `comp.os.vms`. But
hey, it helped me solve this issue.

OpenVMS uses IEFT SECSH (Tectia) format keys. There is an IETF [document][8]
describing the format and [a document][9] on the SSH key subsystem if you want
to know more.

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 `z/OS`.

Using `ssh-keygen` (on linux) we can convert a private key to this format with
the `-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

Output:

---- 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 `[.SSH]REMY-
GATEWAY.PUB`. Save with `CTRL+Z` and retry:

$ ssh -oHostKeyAlgorithms=+ssh-dss -o "PasswordAuthentication no" -i .ssh/id_rsa [email protected]

Output:

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
$

Yay!

### Conclusion

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 `AUTHORIZATION` file and place the key on the system
* Make sure it is the correct key format
* Set the correct permissions
* ???
* PROFIT!!

### One more thing, LOGOUT of OpenVMS

In an earlier article I wrote that I was unable to logout on OpenVMS since
`exit` and `CTRL+D` not exited the SSH session. I stopped my sessions using
either `~.` 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.

[1]: https://raymii.org/s/inc/img/ovmsdec.png
[2]: https://raymii.org/s/tags/openvms.html
[3]: https://www.digitalocean.com/?refcode=7435ae6b8212
[4]: https://web.archive.org/web/20180405170159/http://h41379.www4.hpe.com/doc/83final/ba548_90007/index.html
[5]: http://decus.org
[6]: https://raymii.org/s/tags/hsm.html
[7]: https://web.archive.org/web/20180405171201/http://h41379.www4.hpe.com/doc/83final/ba548_90007/ch03s08.html
[8]: https://www.ietf.org/proceedings/50/I-D/secsh-publickeyfile-01.txt
[9]: https://tools.ietf.org/html/draft-ietf-secsh-publickey-subsystem-08

---

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