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diff --git a/security-blueprint/part-5/0_Abstract.md b/security-blueprint/part-5/0_Abstract.md index e724321..6841230 100644 --- a/security-blueprint/part-5/0_Abstract.md +++ b/security-blueprint/part-5/0_Abstract.md @@ -2,6 +2,17 @@ ## Abstract +The Automotive Grade Linux platform is a Linux distribution with **AGL** compliant applications and services. +The platform includes the following software: + +- Linux **BSP** configured for reference boards. +- Proprietary device drivers for common peripherals on reference boards. +- Application framework. +- Windows/layer management (graphics). +- Sound resource management. +- An atomic software update system (chapter Update). +- Building and debug tools (based on Yocto project). + This part focuses on the AGL platform including all tools and techniques used to upgrade the security and downgrade the danger. It must be possible to apply the two fundamental principles written at the very beginning of the document. First @@ -17,8 +28,8 @@ to deal with, we must: <!-- section-note --> -The tools and concepts used to meet these needs are only examples. Any other -tool that meets the need can be used. +The tools and concepts used to meet these needs are only examples. +Any other tool that meets the need can be used. <!-- end-section-note --> @@ -31,6 +42,34 @@ on the user and the application being run: an application should have access to a given service only if it is run by the proper user and if the appropriate permissions are granted. +## Discretionary Access Control + +**D**iscretionary **A**ccess **C**ontrol (**DAC**) is the traditional Linux method of separating +users and groups from one another. In a shared environment where multiple users +have access to a computer or network, Unix IDs have offered a way to contain access +within privilege areas for individuals, or shared among the group or system. +The Android system took this one step further, assigning new user IDs for each App. +This was never the original intention of Linux UIDs, but was able to provide +Android’s initial security element: the ability to sandbox applications. + +Although AGL mentions use of **DAC** for security isolation, the weight of the +security responsibility lies in the **M**andatory **A**ccess **C**ontrol (**MAC**) and **Cynara**. +Furthermore, there are system services with unique UIDs. however,the system +does not go to the extreme of Android, where every application has its own UID. +All sandboxing (app isolation) in AGL is handled in the **MAC** contexts. + +## Mandatory Access Control + +**M**andatory **A**ccess **C**ontrol (**MAC**) is an extension to **DAC**, +whereby extended attributes (xattr) are associated with the filesystem. +In the case of AGL, the smackfs filesystem allows files and directories +to be associated with a SMACK label, providing the ability of further +discrimination on access control. A SMACK label is a simple null terminated +character string with a maximum of 255 bytes. While it doesn’t offer the +richness of an SELinux label, which provides a user, role,type, and level, +the simplicity of a single value makes the overall design far less complex. +There is arguably less chance of the security author making mistakes in the policies set forth. + -------------------------------------------------------------------------------- <!-- pagebreak --> @@ -45,6 +84,7 @@ _ACL_ | **A**ccess **C**ontrol **L**ists _alsa_ | **A**dvanced **L**inux **S**ound **A**rchitecture _API_ | **A**pplication **P**rogramming **I**nterface _AppFw_ | **App**lication **F**rame**w**ork +_BSP_ | **B**oard **S**upport **P**ackage _Cap_ | **Cap**abilities _DAC_ | **D**iscretionary **A**ccess **C**ontrol _DDOS_ | **D**istributed **D**enial **O**f **S**ervice |