seed_random: support a 'command' to seed /dev/random

This extends 'random_seed' top level entry to include a 'command'
entry, that has the opportunity to then seed the random number generator.

Example config:
 #cloud-config
 random_seed:
   command: ['dd', 'if=/dev/zero', 'of=/dev/random', 'bs=1M', 'count=10']

LP: #1286316

3 files changed, 107 insertions, 9 deletions

diff --git a/ChangeLog b/ChangeLog
index 76ab88c4..a45ab73b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -33,6 +33,8 @@
    rather than relying on EC2 data in openstack metadata service.
  - SmartOS, AltCloud: disable running on arm systems due to bug
    (LP: #1243287, #1285686) [Oleg Strikov]
+ - Allow running a command to seed random, default is 'pollinate -q'
+   (LP: #1286316) [Dustin Kirkland]
 0.7.4:
  - fix issue mounting 'ephemeral0' if ephemeral0 was an alias for a
    partitioned block device with target filesystem on ephemeral0.1.
diff --git a/cloudinit/config/cc_seed_random.py b/cloudinit/config/cc_seed_random.py
index 22a31f29..599280f6 100644
--- a/cloudinit/config/cc_seed_random.py
+++ b/cloudinit/config/cc_seed_random.py
@@ -1,8 +1,11 @@
 # vi: ts=4 expandtab
 #
 #    Copyright (C) 2013 Yahoo! Inc.
+#    Copyright (C) 2014 Canonical, Ltd
 #
 #    Author: Joshua Harlow <harlowja@yahoo-inc.com>
+#    Author: Dustin Kirkland <kirkland@ubuntu.com>
+#    Author: Scott Moser <scott.moser@canonical.com>
 #
 #    This program is free software: you can redistribute it and/or modify
 #    it under the terms of the GNU General Public License version 3, as
@@ -20,9 +23,11 @@ import base64
 from StringIO import StringIO
 
 from cloudinit.settings import PER_INSTANCE
+from cloudinit import log as logging
 from cloudinit import util
 
 frequency = PER_INSTANCE
+LOG = logging.getLogger(__name__)
 
 
 def _decode(data, encoding=None):
@@ -38,24 +43,48 @@ def _decode(data, encoding=None):
         raise IOError("Unknown random_seed encoding: %s" % (encoding))
 
 
-def handle(name, cfg, cloud, log, _args):
-    if not cfg or "random_seed" not in cfg:
-        log.debug(("Skipping module named %s, "
-                   "no 'random_seed' configuration found"), name)
+def handle_random_seed_command(command, required):
+    if not command and required:
+        raise ValueError("no command found but required=true")
+    elif not command:
+        LOG.debug("no command provided")
         return
 
-    my_cfg = cfg['random_seed']
-    seed_path = my_cfg.get('file', '/dev/urandom')
+    cmd = command[0]
+    if not util.which(cmd):
+        if required:
+            raise ValueError("command '%s' not found but required=true", cmd)
+        else:
+            LOG.debug("command '%s' not found for seed_command", cmd)
+            return
+    util.subp(command)
+
+
+def handle(name, cfg, cloud, log, _args):
+    mycfg = cfg.get('random_seed', {})
+    seed_path = mycfg.get('file', '/dev/urandom')
+    seed_data = mycfg.get('data', '')
+
     seed_buf = StringIO()
-    seed_buf.write(_decode(my_cfg.get('data', ''),
-                           encoding=my_cfg.get('encoding')))
+    if seed_data:
+        seed_buf.write(_decode(seed_data, encoding=mycfg.get('encoding')))
 
+    # 'random_seed' is set up by Azure datasource, and comes already in
+    # openstack meta_data.json
     metadata = cloud.datasource.metadata
     if metadata and 'random_seed' in metadata:
         seed_buf.write(metadata['random_seed'])
 
     seed_data = seed_buf.getvalue()
     if len(seed_data):
-        log.debug("%s: adding %s bytes of random seed entrophy to %s", name,
+        log.debug("%s: adding %s bytes of random seed entropy to %s", name,
                   len(seed_data), seed_path)
         util.append_file(seed_path, seed_data)
+
+    command = mycfg.get('command', ['pollinate', '-q'])
+    req = mycfg.get('command_required', False)
+    try:
+        handle_random_seed_command(command=command, required=req)
+    except ValueError as e:
+        log.warn("handling random command [%s] failed: %s", command, e)
+        raise e
diff --git a/tests/unittests/test_handler/test_handler_seed_random.py b/tests/unittests/test_handler/test_handler_seed_random.py
index 2b21ac02..00c50fc1 100644
--- a/tests/unittests/test_handler/test_handler_seed_random.py
+++ b/tests/unittests/test_handler/test_handler_seed_random.py
@@ -42,10 +42,29 @@ class TestRandomSeed(t_help.TestCase):
     def setUp(self):
         super(TestRandomSeed, self).setUp()
         self._seed_file = tempfile.mktemp()
+        self.unapply = []
+
+        # by default 'which' has nothing in its path
+        self.apply_patches([(util, 'which', self._which)])
+        self.apply_patches([(util, 'subp', self._subp)])
+        self.subp_called = []
+        self.whichdata = {}
 
     def tearDown(self):
+        apply_patches([i for i in reversed(self.unapply)])
         util.del_file(self._seed_file)
 
+    def apply_patches(self, patches):
+        ret = apply_patches(patches)
+        self.unapply += ret
+
+    def _which(self, program):
+        return self.whichdata.get(program)
+
+    def _subp(self, args):
+        self.subp_called.append(tuple(args))
+        return
+
     def _compress(self, text):
         contents = StringIO()
         gz_fh = gzip.GzipFile(mode='wb', fileobj=contents)
@@ -148,3 +167,51 @@ class TestRandomSeed(t_help.TestCase):
         cc_seed_random.handle('test', cfg, c, LOG, [])
         contents = util.load_file(self._seed_file)
         self.assertEquals('tiny-tim-was-here-so-was-josh', contents)
+
+    def test_seed_command_not_provided_pollinate_available(self):
+        c = self._get_cloud('ubuntu', {})
+        self.whichdata = {'pollinate': '/usr/bin/pollinate'}
+        cc_seed_random.handle('test', {}, c, LOG, [])
+
+        self.assertEquals(self.subp_called, [('pollinate', '-q')])
+
+    def test_seed_command_not_provided_pollinate_not_available(self):
+        c = self._get_cloud('ubuntu', {})
+        self.whichdata = {}
+        cc_seed_random.handle('test', {}, c, LOG, [])
+
+        # subp should not have been called as which would say not available
+        self.assertEquals(self.subp_called, list())
+
+    def test_unavailable_seed_command_and_required_raises_error(self):
+        c = self._get_cloud('ubuntu', {})
+        self.whichdata = {}
+        self.assertRaises(ValueError, cc_seed_random.handle,
+            'test', {'random_seed': {'command_required': True}}, c, LOG, [])
+
+    def test_seed_command_and_required(self):
+        c = self._get_cloud('ubuntu', {})
+        self.whichdata = {'foo': 'foo'}
+        cfg = {'random_seed': {'command_required': True, 'command': ['foo']}}
+        cc_seed_random.handle('test', cfg, c, LOG, [])
+
+        self.assertEquals(self.subp_called, [('foo',)])
+
+    def test_seed_command_non_default(self):
+        c = self._get_cloud('ubuntu', {})
+        self.whichdata = {'foo': 'foo'}
+        cfg = {'random_seed': {'command_required': True, 'command': ['foo']}}
+        cc_seed_random.handle('test', cfg, c, LOG, [])
+
+        self.assertEquals(self.subp_called, [('foo',)])
+
+
+def apply_patches(patches):
+    ret = []
+    for (ref, name, replace) in patches:
+        if replace is None:
+            continue
+        orig = getattr(ref, name)
+        setattr(ref, name, replace)
+        ret.append((ref, name, orig))
+    return ret