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diff --git a/docs/0-introduction.md b/docs/0-introduction.md new file mode 100644 index 0000000..bb89613 --- /dev/null +++ b/docs/0-introduction.md @@ -0,0 +1,243 @@ +AGL framework 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 |