Add private key file to Pageant from Azure local storage resource

Question

I'm implementing a Cloud Service (worker role) application in Azure which can add private key files to Pageant from an Azure Local Storage. The p variable is a Process which starts cmd.exe as well.

var filename = "pageant.exe";

var workerRoleStorageName = "PrivateKeys";
var privatekeyfilename = "ThePrivateKey.ppk";
var localResource = RoleEnvironment.GetLocalResource(workerRoleStorageName);
var path = Path.Combine(localResource.RootPath, privatekeyfilename);

p.StandardInput.WriteLine(filename + " "+ path);

I'm in local now, so the content of the path variable is something like this:

c:\Users\Username\AppData\Local\dftmp\Resources\4691e8f6-fdbd-42ad-af67-986b491aca89\directory\PrivateKeys\ThePrivateKey.ppk

But at the last line of code I have got the following error message:

Couldn't load this key (unable to open file).

It's quite interesting, because if I set up a hard coded simple path it works fine:

var path = @"E:\PrivateKeys\ThePrivateKey.ppk";

I know that the Azure Local Storage folder is hidden in this case, so I tried to set the E:\PrivateKeys folder to hidden, but it still worked with the hard coded path.

What do you think, why I can't add this file to Pageant from that path?

What do you get, if you try something like `...WriteLine("dir " + path)`? — Martin Prikryl, Aug 26 '14 at 13:03
Interesting, I have got no result for that command, just the flashing cursor. — Gábor Domonkos, Aug 26 '14 at 14:56
Is it different with `dir E:\PrivateKeys\ThePrivateKey.ppk`? — Martin Prikryl, Aug 26 '14 at 14:57
No, it's the same, but at my p.OutputDataReceived I can see the result of the dir commnand, with a latency. So I can list the content of that dir with the dir command. — Gábor Domonkos, Aug 26 '14 at 15:08
Well, that's what I was asking for actually. So `dir` works even for the `path`? Or just for `E:\PrivateKeys\ThePrivateKey.ppk`? — Martin Prikryl, Aug 26 '14 at 15:09
I got an 'Access is denied' message. I have to run the cmd as administrator from code? — Gábor Domonkos, Aug 26 '14 at 15:15

score 0 · Accepted Answer · answered Aug 26 '14 at 15:22

Pageant is unfortunately not very informative when failing to load a private key. It reports "Couldn't load this key (unable to open file)." for any error, including non existence and lack or read permissions.

As is clear from your comments, in this particular instance, it's lack of permissions.

I suppose you need to run your application with higher privileges or with an appropriate role. I would not expect you can run just the cmd.exe with higher privileges from a less privileged process.

Add private key file to Pageant from Azure local storage resource

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