[lug] Windows/PuTTY and Linux SSH Key Pair Compatibility

Orion Poplawski orion at nwra.com
Fri Dec 28 14:55:42 MST 2018

On 12/28/18 2:21 PM, D. Stimits wrote:
> I'm trying to find out what is possible for copying a Windows-generated 
> RSA public key (puttygen) to a Linux server. I do not have physical 
> access, and I have my own key set up since I personally only use Linux 
> to log in, but need to add a login for another user...and that user is 
> using Windows. The trouble is that the public key is not what I 
> expected...it is multi-line, it contains other comment, so on. It looks 
> more like an email PGP key, but ignoring actual body content, this is 
> the format:
> Comment: "rsa-key-20181228"
> ABC...cut...TEn
> DEF...cut...HHN
> ghi...cut...W2L
> JkL...cut...YYB
> XYZ...cut...srW
> Foo...cut...Bar
> ---- END SSH2 PUBLIC KEY ----
> So far as I know, the Linux style ".ssh/authorized_keys" would use a 
> single line, and I am guesing that simply concatenating that content 
> like an OpenSSH style single key might break it. I could have other ssh 
> logins ready before doing this, so it isn't 100% that breaking this 
> would lock me out, but I'd rather hear from someone who has done this 
> before what the correct way is.
> Or, if there are comments on whether alternates to PuTTY (e.g., WinSCP) 
> have worked out when a Windows user needs to occasionally copy a file to 
> a Linux server (mostly just PDF files to a document directory). My goal 
> is to have the Windows user with a single ssh key and keyless login.

I'm pretty sure the puttygen utility can export openssh compatible forms 
of keys, though I don't know the method off the top of my head.

Orion Poplawski
Manager of NWRA Technical Systems          720-772-5637
NWRA, Boulder/CoRA Office             FAX: 303-415-9702
3380 Mitchell Lane                       orion at nwra.com
Boulder, CO 80301                 https://www.nwra.com/

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