version: 1
Date: 15 March 2016
Author: José Bollo
This document describes what we intend to do. It may happen that our current implementation and the content of this document differ.
In case of differences, it is assumed that this document is right and the implementation is wrong.
The daemon afm-user-daemon is in charge of handling applications for one user. Its main tasks are:
enumerate the applications that the user can run and keep the list avalable on demand
start applications for the user, set their running environment, set their security context
list the current runner applications
stop (aka pause), continue (aka resume), terminate the running instance of application
transfer requests for installation or uninstallation of applications to the dedicated system daemon afm-system-daemon
The afm-user-daemon takes its orders from the session instance of D-Bus.
The figure below summarizes the situation of the afm-user-daemon in the system.
+------------------------------------------------------------+
| User |
| +---------------------+ |
| +---------------------+ | Smack isolated | |
| | D-Bus session + | APPLICATIONS | |
| +----------+----------+ +---------+-----------+ |
| | | |
| | | |
| +----------+--------------------------+-----------+ |
| | | |
| | afm-user-daemon | |
| | | |
| +----------+----------------------+----------+----+ |
| | | : |
| | | : |
:================|======================|==========:=========:
| | | : |
| +----------+----------+ +-----+-----+ : |
| | D-Bus system +-----+ CYNARA | : |
| +----------+----------+ +-----+-----+ : |
| | | : |
| +----------+---------+ +-------+----------+----+ |
| | afm-system-daemon +----+ SECURITY-MANAGER | |
| +--------------------+ +-----------------------+ |
| |
| System |
+------------------------------------------------------------+
At start afm-user-daemon scans the directories containing the applications and load in memory the list applications availables to the current user.
When afm-system-daemon installs or removes an application, it sends the signal org.AGL.afm.system.changed on success. If it receives that signal, afm-user-daemon rebuild its list of applications.
afm-user-daemon provides the data that it collected about application to its clients that either want to get that list or to get information about one application.
afm-user-daemon launchs the applications. This means that its builds a secure environment for the application and then start it inside that secured environment.
Applications of different kind can be launched.
This is set using a configuration file that describes how to launch an application of a given kind for a given mode.
There is two launching modes: local or remote.
Launching an application locally means that the application and its binder are launcher together.
Launching application remotely means that only the binder is launched for the application.
Once launched, running instances of application receive a runid that identify them.
afm-user-daemon manages the list of applications that it launched.
With the good permissions, a client can get the list of the running instances and details about a specific running instance. It can also terminate, stop or continue a given application.
If the client has the good permission, afm-user-daemon delegates that task to afm-system-daemon.
afm-user-daemon is launched as a systemd service attached to user sessions. Normally, the service file is located at /usr/lib/systemd/user/afm-user-daemon.service.
The options for launching afm-user-daemon are:
-a
--application directory
Includes the given application directory to
the database base of applications.
Can be repeated.
-r
--root directory
Includes the root application directory to
the database base of applications.
Note that the default root directory for
applications is always added. It is defined
to be /usr/share/afm/applications (may change).
Can be repeated.
-m
--mode (local|remote)
Set the default launch mode.
The default value is 'local'
-d
--daemon
Daemonizes the process. It is not needed by sytemd.
-q
--quiet
Reduces the verbosity (can be repeated).
-v
--verbose
Increases the verbosity (can be repeated).
-h
--help
Prints a short help.
It contains rules for launching applications. When afm-user-daemon need to launch an application, it looks to the mode of launch, local or remote, and the type of the application as given by the file config.xml of the widget.
This couple mode and type allows to select the rule.
The configuration file is /etc/afm/afm-launch.conf.
It contains sections and rules. It can also contain comments and empty lines to improve the readability.
The separators are space and tabulation, any other character is meaning something.
The format is line oriented. The new line character separate the lines.
Lines having only separators are blank lines and are skipped. Line having the character # (sharp) as first not separator character are comment lines and are ignored.
Lines starting with a not separator character are differents of lines starting with a separator character.
The grammar of the configuration file is defined below:
CONF: *COMMENT *SECTION
SECTION: MODE *RULE
RULE: +TYPE VECTOR ?VECTOR
MODE: 'mode' +SEP ('local' | 'remote') *SEP EOL
TYPE: DATA *SEP EOL
VECTOR: +SEP DATA *(+SEP NDATA) *SEP EOL
DATA: CHAR *NCHAR
NDATA: +NCHAR
EOL: NL *COMMENT
COMMENT: *SEP CMT *(SEP | NCHAR) NL
NL: '\x0a'
SEP: '\x20' | '\x09'
CMT: '#'
CHAR: '\x00'..'\x08' | '\x0b'..'\x1f' | '\x21' | '\x22' | '\x24'..'\xff'
NCHAR: CMT | CHAR
Here is a sample of configuration file for defining how to launch an application declared of types application/x-executable, text/x-shellscript and text/html in mode local:
mode local
application/x-executable
text/x-shellscript
%r/%c
text/html
/usr/bin/afb-daemon --mode=local --readyfd=%R --alias=/icons:%I --port=%P --rootdir=%r --token=%S --sessiondir=%D/.afb-daemon
/usr/bin/web-runtime http://localhost:%P/%c?token=%S
This shows that:
Within this mode, the launchers have either one or two vectors describing them. All of these vectors are treated as programs and are executed with the system call ‘execve’.
The first vector is the leader vector and it defines the process group. The second vector (if any) is attached to the group defined by this first vector.
Within this mode, the launchers have either one or two vectors describing them.
The first vector is treated as a program and is executed with the system call ‘execve’.
The second vector (if any) defines a text that is returned to the caller. This mechanism can be used to return the uri to connect to for executing the application remotely.
The daemon afm-user-daemon allocates a port for the running the application remotely. The current implmentation of the port allocation is just incremental. A more reliable (cacheable and same-originable) allocation is to be defined.
Vectors can include sequences of 2 characters that have a special meaning. These sequences are named %substitution because their first character is the percent sign (%) and because each occurrence of the sequence is replaced, at launch time, by the value associated to sequences.
Here is the list of %substitutions:
%%: %.
This simply emits the percent sign %
%a: appid
This is the application Id of the launched application.
Defined by the attribute id of the element
%c: content
The file within the widget directory that is the entry point.
For a HTML application, it is the relative path to the main page (aka index.html).
Defined by the attribute src of the element
%D: datadir
Path of the directory where the application runs (cwd) and stores its data.
It is equal to %h/%a.
%H: height
Requested height for the widget.
Defined by the attribute height of the element
%h: homedir
Path of the home directory for all applications.
It is generally equal to $HOME/app-data
%I: icondir
Path of the directory were the icons of the applications can be found.
%m: mime-type
Mime type of the launched application.
Defined by the attribute type of the element
%n: name
Name of the application as defined by the content of the
element
%p: plugins
Unhandled until now.
Will be the colon separated list of plugins and plugins directory.
%P: port
A port to use. It is currently a kind of random port. The precise model is to be defined later.
%R: readyfd
Number of the file descriptor to use for signalling readyness of the launched process.
%r: rootdir
Path of the directory containing the widget and its data.
%S: secret
An hexadecimal number that can be used to pair the client with its server binder.
%W: width
Requested width for the widget.
Defined by the attribute width of the element
afm-user-daemon takes its orders from the session instance of D-Bus. The use of D-Bus is great because it allows to implement discovery and signaling.
The dbus of the session is by default adressed by the environment variable DBUS_SESSION_BUS_ADDRESS. Using systemd the variable DBUS_SESSION_BUS_ADDRESS is automatically set for user sessions.
The afm-user-daemon is listening with the destination name org.AGL.afm.user at the object of path /org/AGL/afm/user on the interface org.AGL.afm.user for the below detailed members runnables, detail, start, terminate, stop, continue, runners, state, install and uninstall.
D-Bus is mainly used for signaling and discovery. Its optimized typed protocol is not used except for transmitting only one string in both directions.
The client and the service are using JSON serialisation to exchange data.
The D-Bus interface is defined by:
DESTINATION: org.AGL.afm.user
PATH: /org/AGL/afm/user
INTERFACE: org.AGL.afm.user
The signature of any member of the interface is string -> string for JSON -> JSON.
This is the normal case. In case of error, the current implmentation returns a dbus error that is a string.
Here is an example that use dbus-send to query data on installed applications.
dbus-send --session --print-reply \
--dest=org.AGL.afm.user \
/org/AGL/afm/user \
org.AGL.afm.user.runnables string:true
The command line tool afm-util uses dbus-send to send orders to afm-user-daemon. This small scripts allows to send command to afm-user-daemon either interactively at shell prompt or scriptically.
The syntax is simple: it accept a command and if the command requires it, the argument to the command.
Here is the summary of afm-util:
afm-util runnables :
list the runnable widgets installed
afm-util install wgt :
install the wgt file
afm-util uninstall id :
remove the installed widget of id
afm-util detail id :
print detail about the installed widget of id
afm-util runners :
list the running instance
afm-util start id :
start an instance of the widget of id
afm-util terminate rid :
terminate the running instance rid
afm-util stop rid :
stop the running instance rid
afm-util continue rid :
continue the previously rid
afm-util state rid :
get status of the running instance rid
Here is how to list applications using afm-util:
afm-util runnables
Recall:
DESTINATION: org.AGL.afm.user
PATH: /org/AGL/afm/user
INTERFACE: org.AGL.afm.user
Description: Get details about an application from its id.
Input: the id of the application as below.
Either just a string:
"appli@x.y"
Or an object having the field “id” of type string:
{"id":"appli@x.y"}
Output: A JSON object describing the application containing the fields described below.
{
"id": string, the application id (id@version)
"version": string, the version of the application
"width": integer, requested width of the application
"height": integer, resqueted height of the application
"name": string, the name of the application
"description": string, the description of the application
"shortname": string, the short name of the application
"author": string, the author of the application
}
Description: Get the list of applications that can be run.
Input: any valid json entry, can be anything except null.
output: An array of description of the runnable applications. Each item of the array contains an object containing the detail of an application as described above for the method org.AGL.afm.user.detail.
Description: Install an application from its widget file.
If an application of the same id and version exists, it is not reinstalled except if force=true.
Applications are installed in the subdirectories of the common directory of applications. If root is specified, the application is installed under the sub-directories of the root defined.
Note that this methods is a simple accessor to the method org.AGL.afm.system.install of afm-system-daemon.
After the installation and before returning to the sender, afm-user-daemon sends the signal org.AGL.afm.user.changed.
Input: The path of the widget file to install and, optionaly, a flag to force reinstallation, and, optionaly, a root directory.
Either just a string being the absolute path of the widget file:
"/a/path/driving/to/the/widget"
Or an object:
{
"wgt": "/a/path/to/the/widget",
"force": false,
"root": "/a/path/to/the/root"
}
“wgt” and “root” must be absolute paths.
output: An object with the field “added” being the string for the id of the added application.
{"added":"appli@x.y"}
Description: Uninstall an application from its id.
Note that this methods is a simple accessor to the method org.AGL.afm.system.uninstall of afm-system-daemon.
After the uninstallation and before returning to the sender, afm-user-daemon sends the signal org.AGL.afm.user.changed.
Input: the id of the application and, otpionaly, the path to root of the application.
Either a string:
"appli@x.y"
Or an object:
{
"id": "appli@x.y",
"root": "/a/path/to/the/root"
}
output: the value ‘true’.
Description:
Input: the id of the application and, optionaly, the start mode as below.
Either just a string:
"appli@x.y"
Or an object having the field “id” of type string and optionaly a field mode:
{"id":"appli@x.y","mode":"local"}
The field “mode” as a string value being either “local” or “remote”.
output: The runid of the application launched. The runid is an integer.
Description: Terminates the application of runid.
Input: The runid (an integer) of the running instance to terminate.
output: the value ‘true’.
Description: Stops the application of runid until terminate or continue.
Input: The runid (an integer) of the running instance to stop.
output: the value ‘true’.
Description: Continues the application of runid previously stopped.
Input: The runid (an integer) of the running instance to continue.
output: the value ‘true’.
Description: Get informations about a running instance of runid.
Input: The runid (an integer) of the running instance inspected.
output: An object describing the state of the instance. It contains: the runid (an integer), the id of the running application (a string), the state of the application (a string being either “starting”, “running” or “stopped”).
Example of returned state:
{
"runid": 2,
"state": "running",
"id": "appli@x.y"
}
Description: Get the list of the currently running instances.
Input: anything.
output: An array of states, one per running instance, as returned by the methodd org.AGL.afm.user.state.