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Change-Id: Ib9b195814f4596a5cf5233d6a331d206e76c9bae
Signed-off-by: Sebastien Douheret <sebastien.douheret@iot.bzh>

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+AGL framework, IoT.bzh proposal overview
+========================================
+
+Foreword
+--------
+
+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.
+
+
+Introduction
+------------
+
+During the first works in having the security model of Tizen
+integrated in AGL (Automotive Grade Linux) distribution, it became
+quickly obvious that the count of components specific to Tizen
+to integrate was huge.
+
+Here is a minimal list of what was needed:
+
+ - platform/appfw/app-installers
+ - platform/core/security/cert-svc
+ - platform/core/appfw/ail
+ - platform/core/appfw/aul-1
+ - platform/core/appfw/libslp-db-util
+ - platform/core/appfw/pkgmgr-info
+ - platform/core/appfw/slp-pkgmgr
+
+But this list isn't complete because many dependencies are hidden.
+Those hidden dependencies are including some common libraries but also many
+tizen specific sub-components (iniparser, bundle, dlog, libtzplatform-config,
+db-util, vconf-buxton, ...).
+
+This is an issue because AGL is not expected to be Tizen. Taking it would
+either need to patch it for removing unwanted components or to take all
+of them.
+
+However, a careful study of the core components of the security framework
+of Tizen showed that their dependencies to Tizen are light (and since some
+of our work, there is no more dependency to tizen).
+Those components are **cynara**, **security-manager**, **D-Bus aware of cynara**.
+
+Luckily, these core security components of Tizen are provided
+by [meta-intel-iot-security][meta-intel], a set of yocto layers.
+These layers were created by Intel to isolate Tizen specific security
+components from the initial port of Tizen to Yocto.
+The 3 layers are providing components for:
+
+ * Implementing Smack LSM
+ * Implementing Integrity Measurement Architecture
+ * Implementing Tizen Security Framework
+
+The figure below shows the history of these layers.
+
+![Security_model_history][Security_model_history]
+
+We took the decision to use these security layers that provide the
+basis of the Tizen security, the security framework.
+
+For the components of the application framework, built top of
+the security framework, instead of pulling the huge set of packages
+from Tizen, we decided to refit it by developing a tiny set of
+components that would implement the same behaviour but without all
+the dependencies and with minor architectural improvements for AGL.
+
+These components are **afm-system-daemon** and **afm-user-daemon**.
+They provides infrastructure for installing, uninstalling,
+launching, terminating, pausing and resuming applications in
+a multi user secure environment.
+
+A third component exists in the framework, the binder **afb-daemon**.
+The binder provides the easiest way to provide secured API for
+any tier. Currently, the use of the binder is not absolutely mandatory.
+
+This documentation explains the framework created by IoT.bzh
+by rewriting the Tizen Application Framework. Be aware of the
+previous foreword.
+
+<!-- pagebreak -->
+Overview
+--------
+
+The figure below shows the major components of the framework
+and their interactions going through the following scenario:
+APPLICATION installs an other application and then launch it.
+
+![AppFW-APP_install_sequences][AppFW-APP_install_sequences]{style width:70%}
+
+Let follow the sequence of calls:
+
+1. APPLICATION calls its **binder** to install the OTHER application.
+
+2. The binding **afm-main-binding** of the **binder** calls, through
+   **D-Bus** system, the system daemon to install the OTHER application.
+
+3. The system **D-Bus** checks wether APPLICATION has the permission
+   or not to install applications by calling **CYNARA**.
+
+4. The system **D-Bus** transmits the request to **afm-system-daemon**.
+
+   **afm-system-daemon** checks the application to install, its
+   signatures and rights and install it.
+
+5. **afm-system-daemon** calls **SECURITY-MANAGER** for fulfilling
+   security context of the installed application.
+
+6. **SECURITY-MANAGER** calls **CYNARA** to install initial permissions
+   for the application.
+
+7. APPLICATION call its binder to start the nearly installed OTHER application.
+
+8. The binding **afm-main-binding** of the **binder** calls, through
+   **D-Bus** session, the user daemon to launch the OTHER application.
+
+9. The session **D-Bus** checks wether APPLICATION has the permission
+   or not to start an application by calling **CYNARA**.
+
+10. The session **D-Bus** transmits the request to **afm-user-daemon**.
+
+11. **afm-user-daemon** checks wether APPLICATION has the permission
+    or not to start the OTHER application **CYNARA**.
+
+12. **afm-user-daemon** uses **SECURITY-MANAGER** features to set
+    the security context for the OTHER application.
+
+13. **afm-user-daemon** launches the OTHER application.
+
+This scenario does not cover all the features of the frameworks.
+Shortly because details will be revealed in the next chapters,
+the components are:
+
+* ***SECURITY-MANAGER***: in charge of setting Smack contexts and rules,
+  of setting groups, and, of creating initial content of *CYNARA* rules
+  for applications.
+
+* ***CYNARA***: in charge of handling API access permissions by users and by
+  applications.
+
+* ***D-Bus***: in charge of checking security of messaging. The usual D-Bus
+  security rules are enhanced by *CYNARA* checking rules.
+
+* ***afm-system-daemon***: in charge of installing and uninstalling applications.
+
+* ***afm-user-daemon***: in charge of listing applications, querying application details,
+  starting, terminating, pausing, resuming applications and their instances
+  for a given user context.
+
+* ***afb-binder***: in charge of serving resources and features through an
+  HTTP interface.
+
+* ***afm-main-binding***: This binding allows applications to use the API
+  of the AGL framework.
+
+
+Links between the "Security framework" and the "Application framework"
+----------------------------------------------------------------------
+
+The security framework refers to the security model used to ensure
+security and to the tools that are provided for implementing that model.
+
+The security model refers to how DAC (Discretionary Access Control),
+MAC (Mandatory Access Control) and Capabilities are used by the system
+to ensure security and privacy. It also includes features of reporting
+using audit features and by managing logs and alerts.
+
+The application framework manages the applications:
+installing, uninstalling, starting, pausing, listing ...
+
+The application framework uses the security model/framework
+to ensure the security and the privacy of the applications that
+it manages.
+
+The application framework must be compliant with the underlying
+security model/framework. But it should hide it to the applications.
+
+
+The security framework
+----------------------
+
+The implemented security model is the security model of Tizen 3.
+This model is described [here][tizen-secu-3].
+
+The security framework then comes from Tizen 3 but through
+the [meta-intel].
+It includes: **Security-Manager**, **Cynara**
+and **D-Bus** compliant to Cynara.
+
+Two patches are applied to the security-manager. The goal of these patches
+is to remove specific dependencies with Tizen packages that are not needed
+by AGL.
+None of these patches adds or removes any behaviour.
+
+**In theory, the security framework/model is an implementation details
+that should not impact the layers above the application framework**.
+
+The security framework of Tizen provides "nice lad" a valuable component to
+scan log files and analyse auditing. This component is still in development.
+
+
+The application framework
+-------------------------
+
+The application framework on top of the security framework
+provides the components to install and uninstall applications
+and to run it in a secured environment.
+
+The goal is to manage applications and to hide the details of
+the security framework to the applications.
+
+For the reasons explained in introduction, we did not used the
+application framework of Tizen as is but used an adaptation of it.
+
+The basis is kept identical: the applications are distributed
+in a digitally signed container that must match the specifications
+of widgets (web applications). This is described by the technical
+recommendations [widgets] and [widgets-digsig] of the W3 consortium.
+
+This model allows the distribution of HTML, QML and binary applications.
+
+The management of signatures of the widget packages.
+This basis is not meant as being rigid and it can be extended in the
+future to include for example incremental delivery.
+
+
+
+
+[meta-intel]:       https://github.com/01org/meta-intel-iot-security                "A collection of layers providing security technologies"
+[widgets]:          http://www.w3.org/TR/widgets                                    "Packaged Web Apps"
+[widgets-digsig]:   http://www.w3.org/TR/widgets-digsig                             "XML Digital Signatures for Widgets"
+[libxml2]:          http://xmlsoft.org/html/index.html                              "libxml2"
+[openssl]:          https://www.openssl.org                                         "OpenSSL"
+[xmlsec]:           https://www.aleksey.com/xmlsec                                  "XMLSec"
+[json-c]:           https://github.com/json-c/json-c                                "JSON-c"
+[d-bus]:            http://www.freedesktop.org/wiki/Software/dbus                   "D-Bus"
+[libzip]:           http://www.nih.at/libzip                                        "libzip"
+[cmake]:            https://cmake.org                                               "CMake"
+[security-manager]: https://wiki.tizen.org/wiki/Security/Tizen_3.X_Security_Manager "Security-Manager"
+[app-manifest]:     http://www.w3.org/TR/appmanifest                                "Web App Manifest"
+[tizen-security]:   https://wiki.tizen.org/wiki/Security                            "Tizen security home page"
+[tizen-secu-3]:     https://wiki.tizen.org/wiki/Security/Tizen_3.X_Overview         "Tizen 3 security overview"
+
+[AppFW-APP_install_sequences]: pictures/AppFW-APP_install_sequences.svg
+[Security_model_history]: pictures/Security_model_history.svg