[Bug 1469260] Re: [SRU] Custom vendor data causes cloud-init failure on 0.7.5

[Felipe Reyes]

Rebased patch on top of latest cloud-init available in trusty-updates.

** Patch removed: "lp1469260_trusty.debdiff"
   https://bugs.launchpad.net/cloud-init/+bug/1469260/+attachment/4434870/+files/lp1469260_trusty.debdiff

** Patch added: "lp1469260_trusty.debdiff"
   https://bugs.launchpad.net/cloud-init/+bug/1469260/+attachment/4460581/+files/lp1469260_trusty.debdiff

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Title:
  [SRU] Custom vendor data causes cloud-init failure on 0.7.5

Status in cloud-init:
  Fix Released
Status in cloud-init package in Ubuntu:
  Fix Released
Status in cloud-init source package in Trusty:
  In Progress
Status in cloud-init source package in Utopic:
  Invalid

Bug description:
  [Impact]

  When a vendor data json provides a dictionary without a 'cloud-init'
  key, cloud-init renders a non functional user-data, so any
  configuration (i.e. ssh public keys to use) is missed.

  This prevents cloud providers from publishing a vendor data that is
  not intended to be consumed by cloud-init.

  This patch checks for the existence of 'cloud-init' key and tries to
  get None, a string or a list as value, if this process fails or cloud-
  init key is missing the vendor data is set to None.

  [Test Case]

  * deploy an OpenStack cloud (easy right? :) )
    - the easiest way is to branch https://code.launchpad.net/~ost-maintainers/openstack-charm-testing/trunk and run: juju deployer -c default.yaml -d -v -s 10 trusty-kilo
  * configure vendor data
    - Edit /etc/nova/nova.conf in neutron-gateway unit(s), include the following two lines:
      vendordata_driver=nova.api.metadata.vendordata_json.JsonFileVendorData
      vendordata_jsonfile_path=/etc/nova/vendordata.json
    - Create /etc/nova/vendordata.json in neutron-gateway unit(s) with the following content:
      {"custom": {"a": 1, "b": [2, 3]}}
    - Restart nova-api-metadata (sudo service nova-api-metadata restart)
  * Launch an instance using trusty

  Expected result:
  - the new instance is launched and is accesible according to the configuration used

  Actual result:
  - cloud-init fails to configure the ssh public key

  [Regression Potential]

  * This patch is already part of Vivid and there are no known issues.
  * This proposed fix was tested with a custom image and no issues were detected.

  [Other Info]

  I encountered this issue when adding custom vendor data via nova-
  compute. Originally the bug manifested as SSH host key generation
  failing to fire when vendor data was present (example vendor data
  below).

  {"msg": "", "uuid": "4996e2b67d2941818646481453de1efe", "users":
  [{"username": "erhudy", "sshPublicKeys": [], "uuid": "erhudy"}],
  "name": "TestTenant"}

  I launched a volume-backed instance, waited for it to fail, then
  terminated it and mounted its root volume to examine the logs. What I
  found was that cloud-init was failing to process vendor-data into MIME
  multipart (note the absence of the line that indicates that cloud-init
  is writing vendor-data.txt.i):

  2015-06-25 21:41:02,178 - util.py[DEBUG]: Writing to /var/lib/cloud/instance/obj.pkl - wb: [256] 9751 bytes
  2015-06-25 21:41:02,178 - util.py[DEBUG]: Writing to /var/lib/cloud/instances/65c9fb0c-0700-4f87-a22f-c59534e98dfb/user-data.txt - wb: [384] 0 bytes
  2015-06-25 21:41:02,184 - util.py[DEBUG]: Writing to /var/lib/cloud/instances/65c9fb0c-0700-4f87-a22f-c59534e98dfb/user-data.txt.i - wb: [384] 345 bytes
  2015-06-25 21:41:02,185 - util.py[DEBUG]: Writing to /var/lib/cloud/instances/65c9fb0c-0700-4f87-a22f-c59534e98dfb/vendor-data.txt - wb: [384] 234 bytes
  2015-06-25 21:41:02,185 - util.py[DEBUG]: Reading from /proc/uptime (quiet=False)

  After following the call chain all the way down, I found the
  problematic code in user_data.py:

  # Coverts a raw string into a mime message
  def convert_string(raw_data, headers=None):
      if not raw_data:
          raw_data = ''
      if not headers:
          headers = {}
      data = util.decomp_gzip(raw_data)
      if "mime-version:" in data[0:4096].lower():
          msg = email.message_from_string(data)
          for (key, val) in headers.iteritems():
              _replace_header(msg, key, val)
      else:
          mtype = headers.get(CONTENT_TYPE, NOT_MULTIPART_TYPE)
          maintype, subtype = mtype.split("/", 1)
          msg = MIMEBase(maintype, subtype, *headers)
          msg.set_payload(data)
      return msg

  raw_data in the case that is failing is a dictionary rather than the
  expected string, so slicing into data causes a TypeError: unhashable
  type exception.

  I think this bug was fixed after a fashion in 0.7.7, where the call to
  util.decomp_gzip() is now wrapped by util.decode_binary(), which
  appears to always return a string.

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