1 AGL framework, IoT.bzh proposal overview
2 ========================================
7 This document describes what we intend to do. It may happen that our
8 current implementation and the content of this document differ.
10 In case of differences, it is assumed that this document is right
11 and the implementation is wrong.
17 During the first works in having the security model of Tizen
18 integrated in AGL (Automotive Grade Linux) distribution, it became
19 quickly obvious that the count of components specific to Tizen
20 to integrate was huge.
22 Here is a minimal list of what was needed:
24 - platform/appfw/app-installers
25 - platform/core/security/cert-svc
26 - platform/core/appfw/ail
27 - platform/core/appfw/aul-1
28 - platform/core/appfw/libslp-db-util
29 - platform/core/appfw/pkgmgr-info
30 - platform/core/appfw/slp-pkgmgr
32 But this list isn't complete because many dependencies are hidden.
33 Those hidden dependencies are including some common libraries but also many
34 tizen specific sub-components (iniparser, bundle, dlog, libtzplatform-config,
35 db-util, vconf-buxton, ...).
37 This is an issue because AGL is not expected to be Tizen. Taking it would
38 either need to patch it for removing unwanted components or to take all
41 However, a careful study of the core components of the security framework
42 of Tizen showed that their dependencies to Tizen are light (and since some
43 of our work, there is no more dependency to tizen).
44 Those components are **cynara**, **security-manager**, **D-Bus aware of cynara**.
46 Luckily, these core security components of Tizen are provided
47 by [meta-intel-iot-security][meta-intel], a set of yocto layers.
48 These layers were created by Intel to isolate Tizen specific security
49 components from the initial port of Tizen to Yocto.
50 The 3 layers are providing components for:
52 * Implementing Smack LSM
53 * Implementing Integrity Measurement Architecture
54 * Implementing Tizen Security Framework
56 The figure below shows the history of these layers.
58 ![Security_model_history][Security_model_history]
60 We took the decision to use these security layers that provide the
61 basis of the Tizen security, the security framework.
63 For the components of the application framework, built top of
64 the security framework, instead of pulling the huge set of packages
65 from Tizen, we decided to refit it by developing a tiny set of
66 components that would implement the same behaviour but without all
67 the dependencies and with minor architectural improvements for AGL.
69 These components are **afm-system-daemon** and **afm-user-daemon**.
70 They provides infrastructure for installing, uninstalling,
71 launching, terminating, pausing and resuming applications in
72 a multi user secure environment.
74 A third component exists in the framework, the binder **afb-daemon**.
75 The binder provides the easiest way to provide secured API for
76 any tier. Currently, the use of the binder is not absolutely mandatory.
78 This documentation explains the framework created by IoT.bzh
79 by rewriting the Tizen Application Framework. Be aware of the
86 The figure below shows the major components of the framework
87 and their interactions going through the following scenario:
88 APPLICATION installs an other application and then launch it.
90 ![AppFW-APP_install_sequences][AppFW-APP_install_sequences]
92 Let follow the sequence of calls:
94 1. APPLICATION calls its **binder** to install the OTHER application.
96 2. The binding **afm-main-binding** of the **binder** calls, through
97 **D-Bus** system, the system daemon to install the OTHER application.
99 3. The system **D-Bus** checks wether APPLICATION has the permission
100 or not to install applications by calling **CYNARA**.
102 4. The system **D-Bus** transmits the request to **afm-system-daemon**.
104 **afm-system-daemon** checks the application to install, its
105 signatures and rights and install it.
107 5. **afm-system-daemon** calls **SECURITY-MANAGER** for fulfilling
108 security context of the installed application.
110 6. **SECURITY-MANAGER** calls **CYNARA** to install initial permissions
113 7. APPLICATION call its binder to start the nearly installed OTHER application.
115 8. The binding **afm-main-binding** of the **binder** calls, through
116 **D-Bus** session, the user daemon to launch the OTHER application.
118 9. The session **D-Bus** checks wether APPLICATION has the permission
119 or not to start an application by calling **CYNARA**.
121 10. The session **D-Bus** transmits the request to **afm-user-daemon**.
123 11. **afm-user-daemon** checks wether APPLICATION has the permission
124 or not to start the OTHER application **CYNARA**.
126 12. **afm-user-daemon** uses **SECURITY-MANAGER** features to set
127 the security context for the OTHER application.
129 13. **afm-user-daemon** launches the OTHER application.
131 This scenario does not cover all the features of the frameworks.
132 Shortly because details will be revealed in the next chapters,
135 * ***SECURITY-MANAGER***: in charge of setting Smack contexts and rules,
136 of setting groups, and, of creating initial content of *CYNARA* rules
139 * ***CYNARA***: in charge of handling API access permissions by users and by
142 * ***D-Bus***: in charge of checking security of messaging. The usual D-Bus
143 security rules are enhanced by *CYNARA* checking rules.
145 * ***afm-system-daemon***: in charge of installing and uninstalling applications.
147 * ***afm-user-daemon***: in charge of listing applications, querying application details,
148 starting, terminating, pausing, resuming applications and their instances
149 for a given user context.
151 * ***afb-binder***: in charge of serving resources and features through an
154 * ***afm-main-binding***: This binding allows applications to use the API
155 of the AGL framework.
158 Links between the "Security framework" and the "Application framework"
159 ----------------------------------------------------------------------
161 The security framework refers to the security model used to ensure
162 security and to the tools that are provided for implementing that model.
164 The security model refers to how DAC (Discretionary Access Control),
165 MAC (Mandatory Access Control) and Capabilities are used by the system
166 to ensure security and privacy. It also includes features of reporting
167 using audit features and by managing logs and alerts.
169 The application framework manages the applications:
170 installing, uninstalling, starting, pausing, listing ...
172 The application framework uses the security model/framework
173 to ensure the security and the privacy of the applications that
176 The application framework must be compliant with the underlying
177 security model/framework. But it should hide it to the applications.
180 The security framework
181 ----------------------
183 The implemented security model is the security model of Tizen 3.
184 This model is described [here][tizen-secu-3].
186 The security framework then comes from Tizen 3 but through
188 It includes: **Security-Manager**, **Cynara**
189 and **D-Bus** compliant to Cynara.
191 Two patches are applied to the security-manager. The goal of these patches
192 is to remove specific dependencies with Tizen packages that are not needed
194 None of these patches adds or removes any behaviour.
196 **In theory, the security framework/model is an implementation details
197 that should not impact the layers above the application framework**.
199 The security framework of Tizen provides "nice lad" a valuable component to
200 scan log files and analyse auditing. This component is still in development.
203 The application framework
204 -------------------------
206 The application framework on top of the security framework
207 provides the components to install and uninstall applications
208 and to run it in a secured environment.
210 The goal is to manage applications and to hide the details of
211 the security framework to the applications.
213 For the reasons explained in introduction, we did not used the
214 application framework of Tizen as is but used an adaptation of it.
216 The basis is kept identical: the applications are distributed
217 in a digitally signed container that must match the specifications
218 of widgets (web applications). This is described by the technical
219 recommendations [widgets] and [widgets-digsig] of the W3 consortium.
221 This model allows the distribution of HTML, QML and binary applications.
223 The management of signatures of the widget packages.
224 This basis is not meant as being rigid and it can be extended in the
225 future to include for example incremental delivery.
230 [meta-intel]: https://github.com/01org/meta-intel-iot-security "A collection of layers providing security technologies"
231 [widgets]: http://www.w3.org/TR/widgets "Packaged Web Apps"
232 [widgets-digsig]: http://www.w3.org/TR/widgets-digsig "XML Digital Signatures for Widgets"
233 [libxml2]: http://xmlsoft.org/html/index.html "libxml2"
234 [openssl]: https://www.openssl.org "OpenSSL"
235 [xmlsec]: https://www.aleksey.com/xmlsec "XMLSec"
236 [json-c]: https://github.com/json-c/json-c "JSON-c"
237 [d-bus]: http://www.freedesktop.org/wiki/Software/dbus "D-Bus"
238 [libzip]: http://www.nih.at/libzip "libzip"
239 [cmake]: https://cmake.org "CMake"
240 [security-manager]: https://wiki.tizen.org/wiki/Security/Tizen_3.X_Security_Manager "Security-Manager"
241 [app-manifest]: http://www.w3.org/TR/appmanifest "Web App Manifest"
242 [tizen-security]: https://wiki.tizen.org/wiki/Security "Tizen security home page"
243 [tizen-secu-3]: https://wiki.tizen.org/wiki/Security/Tizen_3.X_Overview "Tizen 3 security overview"
245 [AppFW-APP_install_sequences]: pictures/AppFW-APP_install_sequences.svg
246 [Security_model_history]: pictures/Security_model_history.svg