Fix the creation of ~/.juju/ssh to be user owned

Fix the creation of ~/.juju/ssh to be user owned

If the user's first interaction is with bootstrapping the
local provider with sudo, we want to make sure that the
directory and content is owned by the user.

Drive by fix for the cmd/juju MainSuite. I had a root owned
~/.juju/ssh directory, and the test was trying to read it and
failing, so I isolated the test by having it use the FakeHomeSuite
which overrides $HOME (and other things).

Many other utilities written to help with dealing with
creating directories and changing ownership of files to the
user if running under sudo.

https://code.launchpad.net/~thumper/juju-core/juju-ssh-dir-as-user/+merge/201876

(do not edit description out of merge proposal)

[thumper, 2014-01-16 02:43:58]

Please take a look.

[axw, 2014-01-16 03:09:31]

https://codereview.appspot.com/52950043/diff/1/utils/file.go
File utils/file.go (right):

https://codereview.appspot.com/52950043/diff/1/utils/file.go#newcode104
utils/file.go:104: func IsDirectory(path string) bool {
In light of my comments on MkDirAllForUser, I think this should just be ditched.
Some callers will care about symlinks, some won't.

https://codereview.appspot.com/52950043/diff/1/utils/file.go#newcode106
utils/file.go:106: if os.IsNotExist(err) {
This is redundant, given the below check.

https://codereview.appspot.com/52950043/diff/1/utils/sudo.go
File utils/sudo.go (right):

https://codereview.appspot.com/52950043/diff/1/utils/sudo.go#newcode63
utils/sudo.go:63: if IsDirectory(dir) {
How about symlinks?

I think, rather than IsDirectory, use os.Lstat and os.IsNotExist. If there's a
file in the path, then the function can just fail when we attempt to mkdir.

IOW, something like:

_, err := os.Lstat(dir)
if os.IsNotExist(err) {
    if err := MkdirAllForUser(filepath.Dir(dir), perm); err != nil {
        return err
    }
    err = MkdirForUser(dir, perm)
}
if err != nil {
    return err
}
return ChownToUser(dir)

https://codereview.appspot.com/52950043/diff/1/utils/sudo.go#newcode79
utils/sudo.go:79: os.RemoveAll(topMostDir)
This scares me. Can we please not remove things on failure? What if chown $HOME
is a symlink, and chmod fails? Then we try to RemoveAll $HOME.

[axw, 2014-01-16 03:32:41]

On 2014/01/16 03:09:31, axw wrote:
> https://codereview.appspot.com/52950043/diff/1/utils/file.go
> File utils/file.go (right):
> 
> https://codereview.appspot.com/52950043/diff/1/utils/file.go#newcode104
> utils/file.go:104: func IsDirectory(path string) bool {
> In light of my comments on MkDirAllForUser, I think this should just be
ditched.
> Some callers will care about symlinks, some won't.
> 
> https://codereview.appspot.com/52950043/diff/1/utils/file.go#newcode106
> utils/file.go:106: if os.IsNotExist(err) {
> This is redundant, given the below check.
> 
> https://codereview.appspot.com/52950043/diff/1/utils/sudo.go
> File utils/sudo.go (right):
> 
> https://codereview.appspot.com/52950043/diff/1/utils/sudo.go#newcode63
> utils/sudo.go:63: if IsDirectory(dir) {
> How about symlinks?
> 
> I think, rather than IsDirectory, use os.Lstat and os.IsNotExist. If there's a
> file in the path, then the function can just fail when we attempt to mkdir.
> 
> IOW, something like:
> 
> _, err := os.Lstat(dir)
> if os.IsNotExist(err) {
>     if err := MkdirAllForUser(filepath.Dir(dir), perm); err != nil {
>         return err
>     }
>     err = MkdirForUser(dir, perm)
> }
> if err != nil {
>     return err
> }
> return ChownToUser(dir)
> 
> https://codereview.appspot.com/52950043/diff/1/utils/sudo.go#newcode79
> utils/sudo.go:79: os.RemoveAll(topMostDir)
> This scares me. Can we please not remove things on failure? What if chown
$HOME
> is a symlink, and chmod fails? Then we try to RemoveAll $HOME.

LGTM pending changes

[thumper, 2014-01-16 03:50:34]

Please take a look.