In the context of Relational Database Management Systems (RDBMS), MAC stands for Mandatory Access Control.
Understanding Mandatory Access Control (MAC)
Mandatory Access Control (MAC) is a stringent security model used in various systems, including RDBMS, to enforce access control policies. Unlike Discretionary Access Control (DAC), where resource owners can grant or deny access permissions, MAC operates based on system-defined security policies and security labels assigned to both data and users/processes.
According to the provided reference, "Mandatory access control (MAC) is a security strategy that restricts the ability individual resource owners have to grant or deny access to resource objects in a file system."
This principle extends to RDBMS. In a database environment using MAC, the system, not the user or object owner, determines who can access what based on predefined security rules. These rules often involve comparing the sensitivity of the data (e.g., classification level) with the clearance level of the user or process attempting access.
Key Concepts of MAC in RDBMS
- Security Labels: Both subjects (users, processes) and objects (tables, rows, columns) are assigned security labels. These labels represent sensitivity levels or categories (e.g., "Confidential", "Secret", "Top Secret" combined with compartments like "Nuclear", "Crypto").
- System-Defined Policies: Access decisions are made by the system based on mandatory rules that compare subject and object labels. A common policy is the "no read down, no write up" rule from the Bell-LaPadula model, ensuring information doesn't flow from higher to lower security levels.
- Centralized Administration: MAC policies are typically defined and managed by a central authority (like a system administrator or security officer), not individual users.
MAC vs. DAC
Here's a simple comparison between MAC and the more common Discretionary Access Control (DAC):
| Feature | Mandatory Access Control (MAC) | Discretionary Access Control (DAC) |
|---|---|---|
| Decision Maker | System-enforced policies & security labels | Resource owner |
| Control Type | Centralized, mandatory | Decentralized, user-defined |
| Flexibility | Less flexible, rigid policies | More flexible, owner can grant/revoke access |
| Security | High, resistant to Trojan horses | Lower, susceptible to user errors & malware |
| Administration | Complex setup and maintenance | Easier for individual owners |
How MAC Works in an RDBMS
In a MAC-enabled RDBMS:
- Every piece of data (e.g., a row in a table) is tagged with a security label indicating its sensitivity.
- Every user or process is assigned a clearance level or a set of security labels indicating what level of sensitive information they are authorized to access.
- When a user attempts to access data, the RDBMS security kernel compares the user's clearance label with the data's sensitivity label based on the predefined MAC policy.
- Access is granted only if the policy allows it, regardless of any DAC permissions the user might have. For example, a user with "Confidential" clearance cannot read data labeled "Secret", even if they are the data's owner.
Benefits and Drawbacks
- Benefits:
- Provides a high level of security assurance and data isolation.
- Effective in preventing unauthorized information flow (e.g., preventing classified data from being copied to an unclassified file).
- Suitable for environments with strict confidentiality requirements (e.g., government, military, healthcare).
- Drawbacks:
- Complex to implement and manage.
- Less flexible for users.
- Can be resource-intensive.
In summary, MAC in RDBMS is a powerful security model where access is controlled by system-wide policies and security labels, ensuring data is accessed only by entities with the appropriate clearance, overriding the permissions granted by individual object owners. This aligns with the general principle from the reference that MAC restricts the resource owner's ability to grant or deny access.
