Switch to a new role-based authorization framework, removing is_admin()

We began moving away from simple "is this user an admin?" permission checks
before 0.12, with the introduction of mod_authz_internal and the ability to
dynamically change the roles of individual users.

The approach in 0.12 still had various limitations however, and apart from
the introduction of roles other than "admin" and the ability to pull that info
from storage, not much actually changed.

This new framework shakes things up a lot, though aims to maintain the same
functionality and behaviour on the surface for a default Prosody
configuration. That is, if you don't take advantage of any of the new
features, you shouldn't notice any change.

The biggest change visible to developers is that usermanager.is_admin() (and
the auth provider is_admin() method) have been removed. Gone. Completely.

Permission checks should now be performed using a new module API method:

  module:may(action_name, context)

This method accepts an action name, followed by either a JID (string) or
(preferably) a table containing 'origin'/'session' and 'stanza' fields (e.g.
the standard object passed to most events). It will return true if the action
should be permitted, or false/nil otherwise.

Modules should no longer perform permission checks based on the role name.
E.g. a lot of code previously checked if the user's role was prosody:admin
before permitting some action. Since many roles might now exist with similar
permissions, and the permissions of prosody:admin may be redefined
dynamically, it is no longer suitable to use this method for permission
checks. Use module:may().

If you start an action name with ':' (recommended) then the current module's
name will automatically be used as a prefix.

To define a new permission, use the new module API:

  module:default_permission(role_name, action_name)
  module:default_permissions(role_name, { action_name[, action_name...] })

This grants the specified role permission to execute the named action(s) by
default. This may be overridden via other mechanisms external to your module.

The built-in roles that developers should use are:

 - prosody:user (normal user)
 - prosody:admin (host admin)
 - prosody:operator (global admin)

The new prosody:operator role is intended for server-wide actions (such as
shutting down Prosody).

Finally, all usage of is_admin() in modules has been fixed by this commit.
Some of these changes were trickier than others, but no change is expected to
break existing deployments.

EXCEPT: mod_auth_ldap no longer supports the ldap_admin_filter option. It's
very possible nobody is using this, but if someone is then we can later update
it to pull roles from LDAP somehow.

2 files changed, 19 insertions, 28 deletions

diff --git a/plugins/adhoc/adhoc.lib.lua b/plugins/adhoc/adhoc.lib.lua
index eb91f252..9f091e3b 100644
--- a/plugins/adhoc/adhoc.lib.lua
+++ b/plugins/adhoc/adhoc.lib.lua
@@ -23,10 +23,16 @@ end
 function _M.new(name, node, handler, permission)
 	if not permission then
 		error "adhoc.new() expects a permission argument, none given"
-	end
-	if permission == "user" then
+	elseif permission == "user" then
 		error "the permission mode 'user' has been renamed 'any', please update your code"
 	end
+	if permission == "admin" then
+		module:default_permission("prosody:admin", "mod_adhoc:"..node);
+		permission = "check";
+	elseif permission == "global_admin" then
+		module:default_permission("prosody:operator", "mod_adhoc:"..node);
+		permission = "check";
+	end
 	return { name = name, node = node, handler = handler, cmdtag = _cmdtag, permission = permission };
 end
 
diff --git a/plugins/adhoc/mod_adhoc.lua b/plugins/adhoc/mod_adhoc.lua
index 9d6ff77a..c94ff24f 100644
--- a/plugins/adhoc/mod_adhoc.lua
+++ b/plugins/adhoc/mod_adhoc.lua
@@ -7,7 +7,6 @@
 
 local it = require "util.iterators";
 local st = require "util.stanza";
-local is_admin = require "core.usermanager".is_admin;
 local jid_host = require "util.jid".host;
 local adhoc_handle_cmd = module:require "adhoc".handle_cmd;
 local xmlns_cmd = "http://jabber.org/protocol/commands";
@@ -15,18 +14,17 @@ local commands = {};
 
 module:add_feature(xmlns_cmd);
 
+local function check_permissions(event, node, command)
+	return (command.permission == "check" and module:may("mod_adhoc:"..node, event))
+	    or (command.permission == "local_user" and jid_host(event.stanza.attr.from) == module.host)
+	    or (command.permission == "any");
+end
+
 module:hook("host-disco-info-node", function (event)
 	local stanza, origin, reply, node = event.stanza, event.origin, event.reply, event.node;
 	if commands[node] then
-		local from = stanza.attr.from;
-		local privileged = is_admin(from, stanza.attr.to);
-		local global_admin = is_admin(from);
-		local hostname = jid_host(from);
 		local command = commands[node];
-		if (command.permission == "admin" and privileged)
-		    or (command.permission == "global_admin" and global_admin)
-		    or (command.permission == "local_user" and hostname == module.host)
-		    or (command.permission == "any") then
+		if check_permissions(event, node, command) then
 			reply:tag("identity", { name = command.name,
 			    category = "automation", type = "command-node" }):up();
 			reply:tag("feature", { var = xmlns_cmd }):up();
@@ -44,20 +42,13 @@ module:hook("host-disco-info-node", function (event)
 end);
 
 module:hook("host-disco-items-node", function (event)
-	local stanza, reply, disco_node = event.stanza, event.reply, event.node;
+	local reply, disco_node = event.reply, event.node;
 	if disco_node ~= xmlns_cmd then
 		return;
 	end
 
-	local from = stanza.attr.from;
-	local admin = is_admin(from, stanza.attr.to);
-	local global_admin = is_admin(from);
-	local hostname = jid_host(from);
 	for node, command in it.sorted_pairs(commands) do
-		if (command.permission == "admin" and admin)
-		    or (command.permission == "global_admin" and global_admin)
-		    or (command.permission == "local_user" and hostname == module.host)
-		    or (command.permission == "any") then
+		if check_permissions(event, node, command) then
 			reply:tag("item", { name = command.name,
 			    node = node, jid = module:get_host() });
 			reply:up();
@@ -71,15 +62,9 @@ module:hook("iq-set/host/"..xmlns_cmd..":command", function (event)
 	local node = stanza.tags[1].attr.node
 	local command = commands[node];
 	if command then
-		local from = stanza.attr.from;
-		local admin = is_admin(from, stanza.attr.to);
-		local global_admin = is_admin(from);
-		local hostname = jid_host(from);
-		if (command.permission == "admin" and not admin)
-		    or (command.permission == "global_admin" and not global_admin)
-		    or (command.permission == "local_user" and hostname ~= module.host) then
+		if not check_permissions(event, node, command) then
 			origin.send(st.error_reply(stanza, "auth", "forbidden", "You don't have permission to execute this command"):up()
-			    :add_child(command:cmdtag("canceled")
+				:add_child(command:cmdtag("canceled")
 				:tag("note", {type="error"}):text("You don't have permission to execute this command")));
 			return true
 		end