utils/ssh: explicitly specify default identities

utils/ssh: explicitly specify default identities

There is a bug in ssh_openssh.go: if any identities
are specified, then default identities are not
attempted unless they are loaded into the ssh-agent.
This is only a problem if the user relies on the
default identity, AND explicitly specifies
authorized-keys in their environment config.

This problem is fixed by explicitly specifying the
default identities if any identities are specified,
which is almost always (~/.juju/ssh).

Fixes lp:1275657

https://code.launchpad.net/~axwalk/juju-core/lp1275657-default-ssh-identities/+merge/204595

(do not edit description out of merge proposal)

[axw, 2014-02-04 03:21:51]

Please take a look.

[wallyworld, 2014-02-04 03:31:47]

LGTM, just a little iffy about hard coding the default identities, not sure if
there's a golang ssh lib call that can be made to get them?

https://codereview.appspot.com/57690049/diff/1/utils/ssh/ssh_openssh.go
File utils/ssh/ssh_openssh.go (right):

https://codereview.appspot.com/57690049/diff/1/utils/ssh/ssh_openssh.go#newco...
utils/ssh/ssh_openssh.go:27: }
Is there some env variable which tells where ~/.ssh is? Or does ssh always
assume its files live in ~/.ssh? 
Are there the only identities there can be? Is there a lib call we can make to
get these values?

[axw, 2014-02-04 03:37:31]

https://codereview.appspot.com/57690049/diff/1/utils/ssh/ssh_openssh.go
File utils/ssh/ssh_openssh.go (right):

https://codereview.appspot.com/57690049/diff/1/utils/ssh/ssh_openssh.go#newco...
utils/ssh/ssh_openssh.go:27: }
On 2014/02/04 03:31:47, wallyworld wrote:
> Is there some env variable which tells where ~/.ssh is? Or does ssh always
> assume its files live in ~/.ssh? 
> Are there the only identities there can be? Is there a lib call we can make to
> get these values?

According to man ssh, these are the only ones and they are always in ~/.ssh.
There's no SSH_HOME or anything like that. There's also no dynamic source for
obtaining a list, AFAIK.