tests: Enable the NoCloud KVM platform

The NoCloud KVM platform includes:

  * Downloads daily Ubuntu images using streams and store in
    /srv/images
  * Image customization, if required, is done using
    mount-image-callback otherwise image is untouched
  * Launches KVM via the xkvm script, a wrapper around
    qemu-system, and sets custom port for SSH
  * Generation and inject an SSH (RSA 4096) key pair to use for
    communication with the guest to collect test artifacts
  * Add method to produce safe shell strings by base64 encoding
    the command

Additional Changes:

  * Set default backend to use LXD
  * Verify not running script as root in order to prevent images
    from becoming owned by root
  * Removed extra quotes around that were added when collecting
    the cloud-init version from the image
  * Added info about each release as previously the lxd backend
    was able to query that information from pylxd image info,
    however, other backends will not be able to obtain the same
    information as easily

1 files changed, 43 insertions, 0 deletions

diff --git a/tests/cloud_tests/util.py b/tests/cloud_tests/util.py
index 2bbe21c7..4357fbb0 100644
--- a/tests/cloud_tests/util.py
+++ b/tests/cloud_tests/util.py
@@ -2,12 +2,14 @@
 
 """Utilities for re-use across integration tests."""
 
+import base64
 import copy
 import glob
 import os
 import random
 import shutil
 import string
+import subprocess
 import tempfile
 import yaml
 
@@ -242,6 +244,47 @@ def update_user_data(user_data, updates, dump_to_yaml=True):
             if dump_to_yaml else user_data)
 
 
+def shell_safe(cmd):
+    """Produce string safe shell string.
+
+    Create a string that can be passed to:
+         set -- <string>
+    to produce the same array that cmd represents.
+
+    Internally we utilize 'getopt's ability/knowledge on how to quote
+    strings to be safe for shell.  This implementation could be changed
+    to be pure python.  It is just a matter of correctly escaping
+    or quoting characters like: ' " ^ & $ ; ( ) ...
+
+    @param cmd: command as a list
+    """
+    out = subprocess.check_output(
+        ["getopt", "--shell", "sh", "--options", "", "--", "--"] + list(cmd))
+    # out contains ' -- <data>\n'. drop the ' -- ' and the '\n'
+    return out[4:-1].decode()
+
+
+def shell_pack(cmd):
+    """Return a string that can shuffled through 'sh' and execute cmd.
+
+    In Python subprocess terms:
+        check_output(cmd) == check_output(shell_pack(cmd), shell=True)
+
+    @param cmd: list or string of command to pack up
+    """
+
+    if isinstance(cmd, str):
+        cmd = [cmd]
+    else:
+        cmd = list(cmd)
+
+    stuffed = shell_safe(cmd)
+    # for whatever reason b64encode returns bytes when it is clearly
+    # representable as a string by nature of being base64 encoded.
+    b64 = base64.b64encode(stuffed.encode()).decode()
+    return 'eval set -- "$(echo %s | base64 --decode)" && exec "$@"' % b64
+
+
 class InTargetExecuteError(c_util.ProcessExecutionError):
     """Error type for in target commands that fail."""