Xenial: phablet-shell ssh connection fails when using the key created by QtCreator

[Andrea Bernabei]

Environment: Xenial 16.04

Summary:
Keys created by QtCreator can't be used with phablet-shell. Note: this is probably a more generic ssh problem.

How to reproduce:
1) Install Ubuntu SDK (I'm using QtCreator 3.5.1 based on Qt 5.6.0, from SDK's experimental PPA)
2) Tools->Options->Devices->Add a generic linux device
3) Select "password" as auth type and fill in IP and username, then click Next and Finish
4) Click on "Create new" next to "Private key file:"
5) now remove .ssh/authorized_keys on your ubuntu phone/tablet
6) run phablet-shell. It will read the newest key from .ssh (which, at this point, will be the one we've just created) and copy it to .ssh/authorized_keys on the device
7) phablet-shell will fail to connect, returning error
sign_and_send_pubkey: signing failed: agent refused operation

QtCreator creates a 1024bit RSA key, although I could NOT reproduce the problem using a key generated with "ssh-keygen -t rsa -b 1024".

I also tried creating a 2048bit key using QtCreator, and that failed with the same error.

It seems all keys created by QtCreator are unusable to connect to the device using phablet-shell (or more generically ssh)

https://bugzilla.mindrot.org/show_bug.cgi?id=2568 This could be somehow related

openssh-client:
  Installed: 1:7.2p2-4ubuntu1

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.