The permissions

Permission’s names

The proposal here is to specify a naming scheme for permissions that allows the system to be as stateless as possible.
The current specification includes in the naming of permissions either the name of the bound binding when existing and the level of the permission itself.
Doing this, there is no real need for the framework to keep installed permissions in a database.

The permission names are URN of the form:

    urn:AGL:permission:<api>:<level>:<hierarchical-name>

where “AGL” is the NID (the namespace identifier) dedicated to AGL.
(note: a RFC should be produced to standardize this name space)

The permission names are made of NSS (the namespace specific string) starting with “permission:” and followed by colon separated fields.
The 2 first fields are <api> and <level> and the remaining fields are grouped to form the <hierarchical-name>.

    <api> ::= [ <pname> ]

    <pname> ::= 1*<pchars>

    <pchars> ::= <upper> | <lower> | <number> | <extra>

    <extra> ::= "-" | "." | "_" | "@"

The field <api> can be made of any valid character for NSS except the characters colon and star (:*).
This field designates the api providing the permission.
This scheme is used to deduce binding requirements from permission requirements.
The field <api> can be the empty string when the permission is defined by the AGL system itself.

[PROPOSAL 1] The field <api> if starting with the character “@” represents a transversal/cross permission not bound to any binding.

[PROPOSAL 2]The field <api> if starting with the 2 characters “@@” in addition to a permission not bound to any binding, represents a permission that must be set at installation and that can not be revoked later.

<level> ::= 1*<lower>

The field <level> is made only of letters in lower case.
The field <level> can only take some predefined values:

  • system
  • platform
  • partner
  • tiers
  • owner
  • public

The field <hierarchical-name> is made of <pname> separated by colons.

<hierarchical-name> ::= <pname> 0*(":" <pname>)

The names at left are hierarchically grouping the names at right.
This hierarchical behaviour is intended to be used to request permissions using hierarchical grouping.

Permission value

In some case, it could be worth to add a value to a permission.

Currently, the framework allows it for permissions linked to systemd.
But this not currently used.

Conversely, permissions linked to cynara can’t carry data except in their name.

Thus to have a simple and cleaner model, it is better to forbid attachment of value to permission.

Example of permissions

Here is a list of some possible permissions.
These permissions are available the 17th of March 2017.

  • urn:AGL:permission::platform:no-oom
    Set OOMScoreAdjust=-500 to keep the out-of-memory killer away.
  • urn:AGL:permission::partner:real-time
    Set IOSchedulingClass=realtime to give to the process realtime scheduling.
    Conversely, not having this permission set RestrictRealtime=on to forbid realtime features.
  • urn:AGL:permission::public:display
    Adds the group “display” to the list of supplementary groups of the process.
  • urn:AGL:permission::public:syscall:clock
    Without this permission SystemCallFilter=~@clock is set to forfid call to clock.
  • urn:AGL:permission::public:no-htdocs
    The http directory served is not “htdocs” but “.”
  • urn:AGL:permission::public:applications:read
    Allows to read data of installed applications (and to access icons).
  • urn:AGL:permission::partner:service:no-ws
    Forbids services to provide its API through websocket.
  • urn:AGL:permission::partner:service:no-dbus
    Forbids services to provide its API through D-Bus.
  • urn:AGL:permission::system:run-by-default
    Starts automatically the application. Example: home-screen.
  • http://tizen.org/privilege/internal/dbus Permission to use D-Bus.