MRS Cluster User Permission Model

Role-based Access Control

MRS adopts the role-based access control (RBAC) mode to manage rights on the big data system. It integrates the right management functions of the components to centrally manage rights. Common users are shielded from internal right management details, and the right management operations are simplified for administrators, improving right management usability and user experience.

The right model of MRS consists four parts: users, user groups, roles, and rights.

Figure 1 Right model

• Right

  Right, which is defined by components, allows users to access a certain resource of one component. Different components have different rights for their resources.

  For example:

  • HDFS provides read, write, and execute permissions on files.
  • HBase provides create, read, and write permissions on tables.
• Role

  Role is a collection of component rights. Each role can have multiple rights of multiple components. Different roles can have the rights of a resource of one component.

• User group

  User group is a collection of users. When a user group is bound to a role, users in this group obtain the rights defined by the role.

  Different user groups can be associated with the same role. A user group can also be associated with no role, and this user group does not have the rights of any component resources.

  

  In some components, the system grants related rights to specific user groups by default.

• User

  A user is a visitor to the system. Each user has the rights of the user group and role associated with the user. Users need to be added to the user group or associated with roles to obtain the corresponding rights.

Policy-based Access Control

The Ranger component uses policy-based access control (PBAC) to manage rights and implement fine-grained data access control on components such as HDFS, Hive, and HBase.

The component supports only one right control mechanism. After the Ranger right control policy is enabled for the component, the right on the component in the role created on FusionInsight Manager becomes invalid (The ACL rules of HDFS and Yarn still take effect). You need to add a policy on the Ranger management page to grant rights on resources.

The Ranger right model consists of multiple right policies. A right policy consists of the following parts:

• Resource

  Resources are provided by components and can be accessed by users, such as HDFS files or folders, queues in Yarn, and databases, tables, and columns in Hive.

• User

  A User is a visitor to the system. The rights of each user are obtained based on the policy associated with the user. Information about users, user groups, and roles in the LDAP is periodically synchronized to the Ranger.

• Permission

  In a policy, you can configure various access conditions for resources, such as file read and write, permission conditions, rejection conditions, and exception conditions.

Permission Mechanism

MRS adopts the Lightweight Directory Access Protocol (LDAP) to store data of users and user groups. Information about role definitions is stored in the relational database and the mapping between roles and rights is saved in components.

MRS uses Kerberos for unified authentication.

The user permission verification process is as follows:

1. A client (a user terminal or MRS component service) invokes the MRS authentication interface.
2. MRS uses the login username and password for Kerberos authentication.
3. If the authentication succeeds, the client sends a request for accessing the server (an MRS component service).
4. The server finds the user group and role to which the login user belongs.
5. The server obtains all rights of the user group and the role.
6. The server checks whether the client has the right to access the resources it applies for.

Example (RBAC):

There are three files in HDFS, that is, fileA, fileB, and fileC.

• roleA has read and write right for fileA, and roleB has the read right for fileB.
• groupA is bound to roleA, and groupB is bound to roleB.
• userA belongs to groupA and roleB, and userB belongs to groupB.

When userA successfully logs in to the system and accesses the HDFS:

1. HDFS obtains the role (roleB) to which userA is bound.
2. HDFS also obtains the role (roleA) to which the user group of userA is bound.
3. In this case, userA has all the rights of roleA and roleB.
4. As a result, userA has read and write rights for fileA, has the read right on fileB, and has no right for fileC.

Similarly, when userB successfully logs in to the system and accesses the HDFS:

1. userB only has the rights of roleB.
2. As a result, userB has the read right on fileB, and has no rights for fileA and fileC.