Distrustful Decomposition pattern
Description
When using a monolithic application, a single process must be granted all the privileges necessary for the application to operate. This issue is resolved by the Distrustful Decomposition pattern.
The purpose of the Distrustful Decomposition pattern is to divide application functionality among individual processes that require different levels of privileges, and to control the interaction between these processes instead of creating a monolithic application.
Using the Distrustful Decomposition pattern reduces the following:
- Attack surface for each process.
- Functionality and data that a hacker will be able to access if one of the processes is compromised.
Alternate names
Privilege Reduction.
Context
Different functions of an application require different levels of privileges.
Problem
An unsophisticated implementation of an application combines many functions requiring different privileges into one component. This component would need to be run with the maximum level of privileges required for any one of these many functions.
Solution
The Distrustful Decomposition pattern divides functionality among individual processes and isolates potential vulnerabilities within a small subset of the system. A cybercriminal who conducts a successful attack will be able to use only the functionality and data of a single compromised component instead of the entire application.
Structure
This pattern divides one monolithic application into multiple applications that are run as individual processes that could potentially have different privileges. Each process implements a small, clearly defined set of functions of the application. Processes use interprocess communication mechanism to exchange data.
Operation
- In KasperskyOS, an application is divided into processes.
- Processes can exchange messages via IPC.
- A user or remote system connects to the process that provides the necessary functionality with the level of privileges sufficient to perform the requested functions.
Implementation recommendations
Interaction between processes can be unidirectional or bidirectional. It is recommended to always use unidirectional interaction whenever possible. Otherwise, the potential attack surface of individual components increases, which reduces the overall security of the entire system. If bidirectional IPC is used, processes should not trust bidirectional data exchange. For example, if a file system is used for IPC, file contents cannot be trusted.
Specialized implementation in KasperskyOS
In universal operating systems such as Linux or Windows, this pattern does not use anything except the standard process/privileges model that already exists in these operating systems. Each program is run in its own process space with potentially different privileges of the specific user in each process. However, an attack on the OS kernel would reduce the effectiveness of this pattern.
Use of this pattern when developing for KasperskyOS means that control over processes and IPC is entrusted to the microkernel, which is difficult to successfully attack. The Kaspersky Security Module is used for IPC control.
Use of KasperskyOS mechanisms ensures a high level of reliability of the software system with the same or less effort required from the developer when compared to the use of this pattern in programs running under universal operating systems.
In addition, KasperskyOS provides the capability for flexible configuration of security policies. Moreover, the process of defining and editing security policies is potentially independent of the process of developing the applications.
Linked patterns
Use of the Distrustful Decomposition pattern involves use of the Defer to Kernel and Policy Decision Point patterns.
Implementation examples
Examples of an implementation of the Distrustful Decomposition pattern:
Sources of information
The Distrustful Decomposition pattern is described in detail in the following resources:
- Chad Dougherty, Kirk Sayre, Robert C. Seacord, David Svoboda, Kazuya Togashi (JPCERT/CC), "Secure Design Patterns" (March-October 2009). Software Engineering Institute. https://resources.sei.cmu.edu/asset_files/TechnicalReport/2009_005_001_15110.pdf
- Dangler, Jeremiah Y., "Categorization of Security Design Patterns" (2013). Electronic Theses and Dissertations. Paper 1119. https://dc.etsu.edu/etd/1119
