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.

3 files changed, 75 insertions, 9 deletions

diff --git a/core/moduleapi.lua b/core/moduleapi.lua
index 36d82193..f0b412f3 100644
--- a/core/moduleapi.lua
+++ b/core/moduleapi.lua
@@ -19,6 +19,7 @@ local promise = require "util.promise";
 local time_now = require "util.time".now;
 local format = require "util.format".format;
 local jid_node = require "util.jid".node;
+local jid_split = require "util.jid".split;
 local jid_resource = require "util.jid".resource;
 
 local t_insert, t_remove, t_concat = table.insert, table.remove, table.concat;
@@ -601,4 +602,66 @@ function api:get_status()
 	return self.status_type, self.status_message, self.status_time;
 end
 
+function api:default_permission(role_name, permission)
+	permission = permission:gsub("^:", self.name..":");
+	hosts[self.host].authz.add_default_permission(role_name, permission);
+end
+
+function api:default_permissions(role_name, permissions)
+	for _, permission in ipairs(permissions) do
+		permission = permission:gsub("^:", self.name..":");
+		self:default_permission(role_name, permission);
+	end
+end
+
+function api:may(action, context)
+	if type(context) == "string" then -- check JID permissions
+		local role;
+		local node, host = jid_split(context);
+		if host == self.host then
+			role = hosts[host].authz.get_user_role(node);
+		else
+			role = hosts[self.host].authz.get_jid_role(context);
+		end
+		if not role then
+			self:log("debug", "Access denied: JID <%s> may not %s (no role found)", context, action);
+			return false;
+		end
+		local permit = role:may(action);
+		if not permit then
+			self:log("debug", "Access denied: JID <%s> may not %s (not permitted by role %s)", context, action, role.name);
+		end
+		return permit;
+	end
+
+	local session = context.origin or context.session;
+	if not session then
+		error("Unable to identify actor session from context");
+	end
+	if action:byte(1) == 58 then -- action begins with ':'
+		action = self.name..action; -- prepend module name
+	end
+	if session.type == "s2sin" or (session.type == "c2s" and session.host ~= self.host) then
+		local actor_jid = context.stanza.attr.from;
+		local role = hosts[self.host].authz.get_jid_role(actor_jid);
+		if not role then
+			self:log("debug", "Access denied: JID <%s> may not %s (no role found)", actor_jid, action);
+			return false;
+		end
+		local permit = role:may(action, context);
+		if not permit then
+			self:log("debug", "Access denied: JID <%s> may not %s (not permitted by role %s)", actor_jid, action, role.name);
+		end
+		return permit;
+	elseif session.role then
+		local permit = session.role:may(action, context);
+		if not permit then
+			self:log("debug", "Access denied: session %s (%s) may not %s (not permitted by role %s)",
+				session.id, session.full_jid, action, session.role.name
+			);
+		end
+		return permit;
+	end
+end
+
 return api;
diff --git a/core/sessionmanager.lua b/core/sessionmanager.lua
index 7f296ff1..426afa7b 100644
--- a/core/sessionmanager.lua
+++ b/core/sessionmanager.lua
@@ -123,15 +123,24 @@ local function destroy_session(session, err)
 	retire_session(session);
 end
 
-local function make_authenticated(session, username, scope)
+local function make_authenticated(session, username, role_name)
 	username = nodeprep(username);
 	if not username or #username == 0 then return nil, "Invalid username"; end
 	session.username = username;
 	if session.type == "c2s_unauthed" then
 		session.type = "c2s_unbound";
 	end
-	session.auth_scope = scope;
-	session.log("info", "Authenticated as %s@%s", username, session.host or "(unknown)");
+
+	local role;
+	if role_name then
+		role = hosts[session.host].authz.get_role_info(role_name);
+	else
+		role = hosts[session.host].authz.get_user_default_role(username);
+	end
+	if role then
+		sessionlib.set_role(session, role);
+	end
+	session.log("info", "Authenticated as %s@%s [%s]", username, session.host or "(unknown)", role and role.name or "no role");
 	return true;
 end
 
diff --git a/core/usermanager.lua b/core/usermanager.lua
index 45f104fa..970140ef 100644
--- a/core/usermanager.lua
+++ b/core/usermanager.lua
@@ -188,11 +188,6 @@ local function set_roles(jid, host, roles)
 	end
 end
 
-local function is_admin(jid, host)
-	local roles = get_roles(jid, host);
-	return roles and roles["prosody:admin"];
-end
-
 local function get_users_with_role(role, host)
 	if not hosts[host] then return false; end
 	if type(role) ~= "string" then return false; end
@@ -224,7 +219,6 @@ return {
 	get_provider = get_provider;
 	get_roles = get_roles;
 	set_roles = set_roles;
-	is_admin = is_admin;
 	get_users_with_role = get_users_with_role;
 	get_jids_with_role = get_jids_with_role;
 };