Add API version and have server reject incompatible clients.

This patch contains 2 parts.

The first part is a small utility to create and validate the current
API. To do this it needs to load ipalib which on a fresh system
introduces a few problems, namely that it relies on a python plugin
to set the default encoding to utf8. For our purposes we can skip that.
It is also important that any optional plugins be loadable so the
API can be examined.

The second part is a version exchange between the client and server.
The version has a major and a minor version. The major verion is
updated whenever existing API changes. The minor version is updated when
new API is added. A request will be rejected if either the major versions
don't match or if the client major version is higher than then server
major version (though by implication new API would return a command not
found if allowed to proceed).

To determine the API version of the server from a client use the ping
command.

ticket 584

6 files changed, 69 insertions, 6 deletions

diff --git a/ipalib/cli.py b/ipalib/cli.py
index c5fea8f28..c634d4909 100644
--- a/ipalib/cli.py
+++ b/ipalib/cli.py
@@ -32,7 +32,14 @@ import fcntl
 import termios
 import struct
 import base64
-import default_encoding_utf8
+try:
+    import default_encoding_utf8
+except ImportError:
+    # This is a chicken-and-egg problem. The api can't be imported unless
+    # this is already installed and since it is installed with IPA therein
+    # lies the problem. Skip it for now so ipalib can be imported in-tree
+    # even in cases that IPA isn't installed on the dev machine.
+    pass
 
 import frontend
 import backend
@@ -42,6 +49,7 @@ from errors import PublicError, CommandError, HelpError, InternalError, NoSuchNa
 from constants import CLI_TAB
 from parameters import Password, Bytes, File
 from text import _
+from ipapython.version import API_VERSION
 
 
 def to_cli(name):
@@ -884,6 +892,7 @@ class cli(backend.Executioner):
         if not isinstance(cmd, frontend.Local):
             self.create_context()
         kw = self.parse(cmd, argv)
+        kw['version'] = API_VERSION
         if self.env.interactive:
             self.prompt_interactively(cmd, kw)
         self.load_files(cmd, kw)
@@ -931,6 +940,8 @@ class cli(backend.Executioner):
                 dest=option.name,
                 help=unicode(option.doc),
             )
+            if 'no_option' in option.flags:
+                continue
             if option.password and self.env.interactive:
                 kw['action'] = 'store_true'
             elif option.type is bool and option.autofill:
diff --git a/ipalib/constants.py b/ipalib/constants.py
index b6aa85466..9a2f19826 100644
--- a/ipalib/constants.py
+++ b/ipalib/constants.py
@@ -140,6 +140,9 @@ DEFAULT_CONFIG = (
     ('enable_ra', False),
     ('ra_plugin', 'selfsign'),
 
+    # Used when verifying that the API hasn't changed. Not for production.
+    ('validate_api', False),
+
     # ********************************************************
     #  The remaining keys are never set from the values here!
     # ********************************************************
diff --git a/ipalib/crud.py b/ipalib/crud.py
index 6df3c733d..76d57daef 100644
--- a/ipalib/crud.py
+++ b/ipalib/crud.py
@@ -76,7 +76,7 @@ us:
 >>> list(api.Command.user_add.args)
 ['login']
 >>> list(api.Command.user_add.options)
-['first', 'last', 'all', 'raw']
+['first', 'last', 'all', 'raw', 'version']
 
 Notice that ``'ipauniqueid'`` isn't included in the options for our ``user_add``
 plugin.  This is because of the ``'no_create'`` flag we used when defining the
@@ -94,7 +94,7 @@ class created them for us:
 >>> list(api.Command.user_show.args)
 ['login']
 >>> list(api.Command.user_show.options)
-['all', 'raw']
+['all', 'raw', 'version']
 
 As you can see, `Retrieve` plugins take a single argument (the primary key) and
 no options.  If needed, you can still specify options for your `Retrieve` plugin
diff --git a/ipalib/frontend.py b/ipalib/frontend.py
index 7177bd185..eeed3980c 100644
--- a/ipalib/frontend.py
+++ b/ipalib/frontend.py
@@ -30,9 +30,11 @@ from util import make_repr
 from output import Output, Entry, ListOfEntries
 from text import _, ngettext
 
-from errors import ZeroArgumentError, MaxArgumentError, OverlapError, RequiresRoot
+from errors import ZeroArgumentError, MaxArgumentError, OverlapError, RequiresRoot, VersionError, RequirementError
 from errors import InvocationError
 from constants import TYPE_ERROR
+from ipapython.version import API_VERSION
+from distutils import version
 
 
 RULE_FLAG = 'validation_rule'
@@ -412,6 +414,8 @@ class Command(HasParam):
         self.info(
             '%s(%s)', self.name, ', '.join(self._repr_iter(**params))
         )
+        if not self.api.env.in_server and 'version' not in params:
+            params['version'] = API_VERSION
         self.validate(**params)
         (args, options) = self.params_2_args_options(**params)
         ret = self.run(*args, **options)
@@ -680,6 +684,30 @@ class Command(HasParam):
             value = kw.get(param.name, None)
             param.validate(value, self.env.context)
 
+    def verify_client_version(self, client_version):
+        """
+        Compare the version the client provided to the version of the
+        server.
+
+        If the client major version does not match then return an error.
+        If the client minor version is less than or equal to the server
+        then let the request proceed.
+        """
+        ver = version.LooseVersion(client_version)
+        if len(ver.version) < 2:
+            raise VersionError(cver=ver.version, sver=server_ver.version, server= self.env.xmlrpc_uri)
+        client_major = ver.version[0]
+        client_minor = ver.version[1]
+
+        server_ver = version.LooseVersion(API_VERSION)
+        server_major = server_ver.version[0]
+        server_minor = server_ver.version[1]
+
+        if server_major != client_major:
+            raise VersionError(cver=client_version, sver=API_VERSION, server=self.env.xmlrpc_uri)
+        if client_minor > server_minor:
+            raise VersionError(cver=client_version, sver=API_VERSION, server=self.env.xmlrpc_uri)
+
     def run(self, *args, **options):
         """
         Dispatch to `Command.execute` or `Command.forward`.
@@ -693,6 +721,9 @@ class Command(HasParam):
         performs is executed remotely.
         """
         if self.api.env.in_server:
+            if 'version' in options:
+                self.verify_client_version(options['version'])
+                del options['version']
             return self.execute(*args, **options)
         return self.forward(*args, **options)
 
@@ -826,6 +857,11 @@ class Command(HasParam):
                     exclude='webui',
                     flags=['no_output'],
                 )
+                yield Str('version?',
+                    doc=_('Client version. Used to determine if server will accept request.'),
+                    exclude='webui',
+                    flags=['no_option', 'no_output'],
+                )
                 return
 
     def validate_output(self, output):
diff --git a/ipalib/plugins/batch.py b/ipalib/plugins/batch.py
index 07c50600a..f6f662f28 100644
--- a/ipalib/plugins/batch.py
+++ b/ipalib/plugins/batch.py
@@ -33,7 +33,7 @@ where the contenst of the file batch_request.json follow the below example
         {"method":"user_show","params":[["admin"],{"all":true}]}
         ],{}],"id":1}
 
-THe format of the response is nested the same way.  At the top you will see
+The format of the response is nested the same way.  At the top you will see
   "error": null,
     "id": 1,
     "result": {
@@ -51,6 +51,7 @@ from ipalib import Str, List
 from ipalib.output import Output
 from ipalib import output
 from ipalib.text import _
+from ipapython.version import API_VERSION
 
 class batch(Command):
     INTERNAL = True
@@ -61,6 +62,17 @@ class batch(Command):
              ),
         )
 
+    take_options = (
+        Str('version',
+            cli_name='version',
+            doc=_('Client version. Used to determine if server will accept request.'),
+            exclude='webui',
+            flags=['no_option', 'no_output'],
+            default=API_VERSION,
+            autofill=True,
+            )
+    )
+
     has_output = (
         Output('count', int, doc=_('')),
         Output('results', list, doc=_(''))
diff --git a/ipalib/plugins/ping.py b/ipalib/plugins/ping.py
index 634c4f875..c2f9b6b28 100644
--- a/ipalib/plugins/ping.py
+++ b/ipalib/plugins/ping.py
@@ -23,6 +23,7 @@ Ping the remote IPA server
 from ipalib import api
 from ipalib import Command
 from ipalib import output
+from ipapython.version import VERSION, API_VERSION
 
 class ping(Command):
     """
@@ -37,6 +38,6 @@ class ping(Command):
         A possible enhancement would be to take an argument and echo it
         back but a fixed value works for now.
         """
-        return dict(summary=u'pong')
+        return dict(summary=u'IPA server version %s. API version %s' % (VERSION, API_VERSION))
 
 api.register(ping)