[PATCH] Introduce the authorizer protocol

[Giulio Camuffo]

This new extension is used by clients wanting to execute priviledged
actions such as taking a screenshot.
The usual way of granting special priviledged to apps is to fork and
exec them in the compositor, and then checking if the client is the
known one when it binds the restricted global interface. This works
but is quite limited, as it doesn't allow the compositor to ask the
user if the app is trusted, because it can't wait for the answer in
the bind function as that would block the compositor.
This new protocol instead allows the answer to come after some time
without blocking the compositor or the client.
---

For reference, i've implemented this in orbital[0] and it's used by
the screenshooter tool[1]. The name is different but it works exaclty
the same as this one.
One thing missing is how the revoke authorization, if even want/need it?

0: https://github.com/giucam/orbital/blob/master/src/compositor/authorizer.cpp
1: https://github.com/giucam/orbital/blob/master/src/screenshooter/main.cpp#L301 


 Makefile.am                                    |  1 +
 unstable/authorizer/authorizer-unstable-v1.xml | 90 ++++++++++++++++++++++++++
 2 files changed, 91 insertions(+)
 create mode 100644 unstable/authorizer/authorizer-unstable-v1.xml

diff --git a/Makefile.am b/Makefile.am
index a32e977..bfe9a6a 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -5,6 +5,7 @@ unstable_protocols =								\
 	unstable/text-input/text-input-unstable-v1.xml				\
 	unstable/input-method/input-method-unstable-v1.xml			\
 	unstable/xdg-shell/xdg-shell-unstable-v5.xml				\
+	unstable/authorizer/authorizer-unstable-v1.xml
 	$(NULL)
 
 nobase_dist_pkgdata_DATA =							\
diff --git a/unstable/authorizer/authorizer-unstable-v1.xml b/unstable/authorizer/authorizer-unstable-v1.xml
new file mode 100644
index 0000000..f10dd0e
--- /dev/null
+++ b/unstable/authorizer/authorizer-unstable-v1.xml
@@ -0,0 +1,90 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<protocol name="authorizer_unstable_v1">
+
+  <copyright>
+    Copyright © 2015 Giulio Camuffo.
+
+    Permission to use, copy, modify, distribute, and sell this
+    software and its documentation for any purpose is hereby granted
+    without fee, provided that the above copyright notice appear in
+    all copies and that both that copyright notice and this permission
+    notice appear in supporting documentation, and that the name of
+    the copyright holders not be used in advertising or publicity
+    pertaining to distribution of the software without specific,
+    written prior permission.  The copyright holders make no
+    representations about the suitability of this software for any
+    purpose.  It is provided "as is" without express or implied
+    warranty.
+
+    THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS
+    SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+    FITNESS, IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY
+    SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
+    AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
+    ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
+    THIS SOFTWARE.
+  </copyright>
+
+  <interface name="zwp_authorizer_v1" version="1">
+    <description summary="authorize clients to use certain interfaces">
+      This global interface allows clients to ask the compositor the
+      authorization to bind certain restricted global interfaces.
+      Any client that aims to bind restricted interfaces should first
+      request the authorization by using this interface. Failing to do
+      so will result in the compositor sending a protocol error to the
+      client when it binds the restricted interface.
+
+      The list of restricted interfaces is compositor dependant, but must
+      not include the core interfaces defined in wayland.xml. However, if
+      an authorization request is done for a non-restricted interface the
+      compositor must reply with a grant.
+    </description>
+
+    <request name="destroy" type="destructor">
+      <description summary="destroy this zwp_authorizer_v1 object">
+        Any currently ongoing authorization request will outlive this object.
+      </description>
+    </request>
+
+    <request name="authorize">
+      <description summary="authorize a global interface">
+        The authorize request allows the client to ask the compositor the
+        authorization to bind a restricted global interface. The newly
+        created zwp_authorizer_feedback_v1 will be invalid after the
+        compositor sends either the granted or denied event so the client
+        is expected to destroy it immediately after.
+      </description>
+      <arg name="id" type="new_id" interface="zwp_authorizer_feedback_v1" summary="the new feedback object"/>
+      <arg name="global" type="string" summary="the global interface the client wants to bind"/>
+    </request>
+    </interface>
+
+    <interface name="zwp_authorizer_feedback_v1" version="1">
+      <description summary="feedback for an authorization request">
+        A zwp_authorizer_feedback_v1 object is created by requesting
+        an authorization with the zwp_authorizer_v1.authorize request.
+        The compositor will send either the granted or denied event based
+        on the system and user configuration. How the authorization process
+        works is compositor specific, but a compositor is allowed to ask
+        for user input, so the client must not assume the reply will come
+        immediately.
+      </description>
+
+      <event name="granted">
+        <description summary="the authorization was granted">
+          The authorization was granted. The client can now bind the restricted
+          interface.
+        </description>
+      </event>
+
+      <event name="denied">
+        <description summary="the authorization was denied">
+          The authorization was denied. The client is not allowed to bind the
+          restricted interface and trying to do so will trigger a protocol
+          error killing the client.
+        </description>
+      </event>
+
+  </interface>
+</protocol>
-- 
2.6.2