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Re: Other comments on draft-ietf-secsh-publickey-subsystem





On Wednesday, August 30, 2006 10:12:27 AM -0500 Nicolas Williams <Nicolas.Williams%sun.com@localhost> wrote:

On Wed, Aug 30, 2006 at 12:54:01PM +0200, Jon Bright wrote:
Nicolas Williams wrote:
>
>>> - An attribute is needed to set environment variables for the
>>>  environment where the command/shell/subsystem is executed.
>> Why?  Again, I think it's too late for this kind of substantive
>> change.
>
> Because the facility you patterned this after (right?  OpenSSH?) has a
> way to associate environment variables with public keys.

I didn't write the original version of this draft, I've just been
shepherding it since it became a WG working item.  It'd be nice to
document how OpenSSH does this, but I think it's too late to make this
the job of this draft.

But then OpenSSH can't implement this protocol without changing its
existing behaviour.


Therefore I think the fair thing to do would be to either allow the
'command-override' command to override subsystem commands also

I don't think so.

Subsystems are not the same as shells. A subsystem name is essentially a protocol constant used to request a particular service; it is not a command. It's appropriate to limit what subsystems may be used, but not to replace a subsystem with a connection to a random program that does not speak the protocol defined for that subsystem. I understand that this is the current OpenSSH behavior, but I believe that behavior is problematic, and that defining a useful, interoperable behavior is more important than being consistent with OpenSSH.

OpenSSH _can_ implement this protocol without eliminating its existing behavior and without breaking backward-compatibility, by introducing a new keyword which has the effect specified for command-override.

-- Jeff



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