[api] OPSAPS-31699 Add SSL context argument to ApiResource

Starting in Python 2.7, SSL certificate validation is turned on by
default (yay!), but means that if CM is using an SSL certificate not
signed by a public CA, Python API calls will fail. To allow specifying
a local CA certificate, we need to allow API users to pass in a custom
SSL context. This change adds the SSL context argument to ApiResource.
Because HTTPSHandler only supports the context argument in Python 2.7.9
and above, this feature is only available in those versions.

Testing:
- Added an example script which connects to CM using a custom CA cert
- Tested against my cluster which has HTTPS turned on

Author: jtran-cloudera

python/examples/tls.py

@@ -0,0 +1,88 @@
+#!/usr/bin/env python
+# Licensed to Cloudera, Inc. under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  Cloudera, Inc. licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""
+Lists all hosts managed by CM. Demonstrates connecting to CM via HTTPS using a
+custom CA certificate in PEM format. Requires Python 2.7.9 or higher.
+
+Usage: %s hostname username password ca_cert_file [options]
+
+Options:
+-h    Displays usage
+"""
+
+import getopt
+import inspect
+import logging
+import ssl
+import sys
+import textwrap
+
+from cm_api.api_client import ApiResource
+
+def list_hosts(host, username, password, cafile):
+  context = ssl.create_default_context(cafile=cafile)
+
+  api = ApiResource(host, username=username, password=password, use_tls=True,
+                    ssl_context=context)
+
+  for h in api.get_all_hosts():
+    print h.hostname
+
+def usage():
+  doc = inspect.getmodule(usage).__doc__
+  print >>sys.stderr, textwrap.dedent(doc % (sys.argv[0],))
+
+def setup_logging(level):
+  logging.basicConfig()
+  logging.getLogger().setLevel(level)
+
+def main(argv):
+  setup_logging(logging.INFO)
+
+  # Argument parsing
+  try:
+    opts, args = getopt.getopt(argv[1:], "h")
+  except getopt.GetoptError, err:
+    print >>sys.stderr, err
+    usage()
+    return -1
+
+  for option, val in opts:
+    if option == '-h':
+      usage()
+      return -1
+    else:
+      print >>sys.stderr, "Unknown flag:", option
+      usage()
+      return -1
+
+  if len(args) < 4:
+    print >>sys.stderr, "Invalid number of arguments"
+    usage()
+    return -1
+
+  # Do work
+  list_hosts(*args)
+  return 0
+
+
+#
+# The "main" entry
+#
+if __name__ == '__main__':
+  sys.exit(main(sys.argv))

python/src/cm_api/api_client.py

@@ -55,7 +55,8 @@ class ApiResource(Resource):
 
   def __init__(self, server_host, server_port=None,
                username="admin", password="admin",
-               use_tls=False, version=API_CURRENT_VERSION):
+               use_tls=False, version=API_CURRENT_VERSION,
+               ssl_context=None):
     """
     Creates a Resource object that provides API endpoints.
 
@@ -66,6 +67,7 @@ def __init__(self, server_host, server_port=None,
     @param password: Login password.
     @param use_tls: Whether to use tls (https).
     @param version: API version.
+    @param ssl_context: A custom SSL context to use for HTTPS (Python 2.7.9+)
     @return: Resource object referring to the root.
     """
     self._version = version
@@ -75,7 +77,8 @@ def __init__(self, server_host, server_port=None,
     base_url = "%s://%s:%s/api/v%s" % \
         (protocol, server_host, server_port, version)
 
-    client = HttpClient(base_url, exc_class=ApiException)
+    client = HttpClient(base_url, exc_class=ApiException,
+                        ssl_context=ssl_context)
     client.set_basic_auth(username, password, API_AUTH_REALM)
     client.set_headers( { "Content-Type" : "application/json" } )
     Resource.__init__(self, client)

python/src/cm_api/http_client.py

@@ -78,10 +78,11 @@ class HttpClient(object):
   """
   Basic HTTP client tailored for rest APIs.
   """
-  def __init__(self, base_url, exc_class=None, logger=None):
+  def __init__(self, base_url, exc_class=None, logger=None, ssl_context=None):
     """
     @param base_url: The base url to the API.
     @param exc_class: An exception class to handle non-200 results.
+    @param ssl_context: A custom SSL context to use for HTTPS (Python 2.7.9+)
 
     Creates an HTTP(S) client to connect to the Cloudera Manager API.
     """
@@ -97,11 +98,19 @@ def __init__(self, base_url, exc_class=None, logger=None):
     # Make a cookie processor
     cookiejar = cookielib.CookieJar()
 
-    self._opener = urllib2.build_opener(
-        HTTPErrorProcessor(),
-        urllib2.HTTPCookieProcessor(cookiejar),
-        authhandler)
-
+    # Python 2.6's HTTPSHandler does not support the context argument, so only
+    # instantiate it if non-None context is given
+    if (ssl_context is not None):
+      self._opener = urllib2.build_opener(
+          urllib2.HTTPSHandler(context=ssl_context),
+          HTTPErrorProcessor(),
+          urllib2.HTTPCookieProcessor(cookiejar),
+          authhandler)
+    else:
+      self._opener = urllib2.build_opener(
+          HTTPErrorProcessor(),
+          urllib2.HTTPCookieProcessor(cookiejar),
+          authhandler)
 
   def set_basic_auth(self, username, password, realm):
     """