Bài giảng Bảo mật cơ sở dữ liệu: Security models - Trần Thị Kim Chi

Bài giảng Bảo mật cơ sở dữ liệu: Security models trình bày các nội dung: Access control, types of Access control, mandatory access control, rules based access control, authentication methods, operating system authentication,... Mời các bạn cùng tham khảo.

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© FPT Software 1

Giảng Viên: Trần Thị Kim Chi

Operating System Security Fundamentals Tiếp theo bài 1 bắt đầu từ Slide 10

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d Database Application Security Models

Discretionary/mandatory access control

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view or use resources in a computing environment.

• Access control systems perform authorization identification, authentication , access

approval, and accountability of entities through login credentials includingpasswords , personal identification numbers (PINs), biometric scans, and physical or electronic keys.

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Types of Access control

• There are two main types of access control:

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• Mandatory access control

• Role-based access control

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Mandatory access control (MAC)

• Mandatory access control (MAC) is a system-controlled policy restricting access to resource objects (such as data files, devices, systems, etc.) based on the level of authorization or clearance of the accessing entity, be it person, process, or device.

• http://searchsecurity.techtarget.com/definition/mandatory-access-control-MAC

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Trusted Computer System Evaluation Criteria "as a means of restricting access to objects based

on the identity of subjects and/or groups to which they belong The controls are discretionary in the sense that a subject with a certain access permission is capable of passing that permission (perhaps indirectly) on to any other subject (unless restrained by mandatory access control )".

• Discretionary access control is commonly discussed in contrast to mandatory access control

(MAC, sometimes termed non-discretionary access control)

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Role-based access control (RBAC)

• Role-based access control (RBAC) is a method of regulating access to computer or network

resources based on the roles of individual users within an enterprise

• http://searchsecurity.techtarget.com/definition/role-based-access-control-RBAC

• http://

searchsecurity.techtarget.com/tip/Role-based-access-control-for-effective-security-management

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where business changes trigger the application of Rules , which specify access changes.

• Implementation of Rules Based Access Control systems is feasible so long as the number of

triggering business events and the set of possible actions that follow those events are both small.

• - See more at:

http://hitachi-id.com/concepts/rules_based_access_control.html#sthash.TJMhLiGM.dpuf

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Authentication Methods

• Authentication:

– Verifies user identity

– Permits access to the operating system

• Physical authentication:

– Allows physical entrance to company property

– Magnetic cards and biometric measures

• Digital authentication: verifies user identity by digital means

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• Digital token (security token):

– Small electronic device

– Displays a number unique to the token holder; used with the holder’s PIN as a password

– Uses a different password each time

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• Digital card:

– Also known as a security card or smart card

– Similar to a credit card; uses an electronic circuit instead of a magnetic strip

– Stores user identification information

• Kerberos:

– Developed by MIT

– Uses tickets for authentication purposes

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– Developed by the University of Michigan

– A centralized directory database stores:

• Users (user name and user ID)

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• NTLM:

– Developed and used by Microsoft

– Employs a challenge/response authentication protocol

• Public Key Infrastructure (PKI):

– User keeps a private key

– Authentication firm holds a public key

– Encrypt and decrypt data using both keys

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• RADIUS: used by network devices to provide a centralized authentication mechanism

• Secure Socket Layer (SSL): authentication information is transmitted over the network in an

encrypted form

• Secure Remote Password (SRP):

– Password is not stored locally

– Invulnerable to brute force or dictionary attacks

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Authorization

• Process that decides whether users are permitted to perform the functions they request

• Authorization is not performed until the user is authenticated

• Deals with privileges and rights

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• Many databases (including Microsoft SQL Server

2000) depend on OS to authenticate users

• Reasons:

– Once an intruder is inside the OS, it is easier to access

the database

– Centralize administration of users

• Users must be authenticated at each level

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User Administration

• Create user accounts

• Set password policies

• Grant privileges to users

• Best practices:

– Use a consistent naming convention

– Always provide a password to an account and force the user to change it at the first logon

– Protect passwords

– Do not use default passwords

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• Associate login ID with a database user

• Must be member of fixed server roles (SYSADMIN or SECURITYADMIN)

• Two types of login IDs:

– Windows Integrated (trusted) login

– SQL Server login

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Creating Windows Integrated Logins

• Command line:

– SP_GRANTLOGIN system stored procedure

– Can be associated local, domain, group usernames

• Enterprise Manager:

– Use the Security container

– Logins -> New Login

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Creating SQL Server Logins

• Command line:

– SP_ADDLOGIN system stored procedure

– Password is encrypted by default

– Specify a default database

– Security container

– SQL Server Authentication option

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• Command line:

– SP_ADDLOGIN system stored procedure

– Password is encrypted by default

– Specify a default database

– Security container

– SQL Server Authentication option

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Removing Users

• Simple process

• Make a backup first

• Obtain a written request (for auditing purposes)

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• Command line: SP_DENYLOGIN system stored procedure

– Highlight the desired login

– Choose Delete from the Action menu

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– Increasing a storage quota

• ALTER USER DDL statement

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• Command line:

– SP_DEFAULTDB system stored procedure

– SP_DEFAULTLANGUAGE stored procedure

– Expand the security container

– Select desired login

– Properties (on the Action Menu)

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Default Users

• Oracle default users:

– SYS, owner of the data dictionary

– SYSTEM, performs almost all database tasks

– ORAPWD, creates a password file

• SQL Server default users:

– SA, system administrator

– BUILT_IN\Administrators

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Database Links

• Connection from one database to another: allow DDL and SQL statements

• Types: PUBLIC and PRIVATE

• Authentication Methods:

– CURRENT USER

– FIXED USER

– CONNECT USER

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• Connection from one database to another: allow DDL and SQL statements

• Types: PUBLIC and PRIVATE

• Authentication Methods:

– CURRENT USER

– FIXED USER

– CONNECT USER

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• Allow you to connect to almost any:

– Object Linking and Embedding Database (OLEDB)

– Open Database Connectivity (ODBC)

• OPENQUERY function

• Map logins in your SQL Server instance to users in the linked database

• Remote servers: allow communication using RPC

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Best Practices

• Follow company’s policies and procedures

• Always document and create logs

• Educate users

• Keep abreast of database and security technology

• Review and modify procedures

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• For SQL server:

– Mimic Oracle’s recommended installation for UNIX

– Use local Windows or domain Windows accounts

• Block direct access to database tables

• Limit and restrict access to the server

• Use strong passwords

• Patches, patches, patches

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Best Practices

• For SQL server:

– Mimic Oracle’s recommended installation for UNIX

– Use local Windows or domain Windows accounts

• Block direct access to database tables

• Limit and restrict access to the server

• Use strong passwords

• Patches, patches, patches

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Best Practices

• Modifying user attributes: ALTER USER DDL statement

• Local database and users

• Remote users

• Database links

• Linked servers

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• First line of defense

• Dictionary attack: permutation of words in dictionary

• Make hard for hackers entering your systems

• Best password policy:

– Matches your company missions

– Enforced at all level of the organization

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Defining and Using Profiles

• Profile:

– Describes limitation of database resources

– Defines database users behavior

– Prevents users from wasting resources

• Not offered by every database system:

– Oracle does

– Microsoft SQL Server 2000 does not

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• Profiles are not available in Microsoft SQL Server 2000 or 2005

• Query and connection time-outs: handled at application level within OLEDB

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Designing and Implementing Password Policies

• Password is the key to open a user account; strong passwords are harder to break

• User authentication depends on passwords

• Hacker violations begin with breaking a password

• Companies spend on:

– Training

– Education

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• Set of guidelines:

– Enhances the robustness of a password

– Reduces the likelihood of password breaking

• Deals with:

– Complexity

– Change frequency

– Reuse

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Importance of Password Policies

• First line of defense

• Most companies invest considerable resources to strengthen authentication by adopting

technological measures that protect their assets

• Forces employees to abide by the guidelines set by the company and raises employee

awareness of password protection

• Helps ensure that a company does not fail audits

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• Complexity: set of guidelines for creating passwords

• Aging: how long a password can be used

• Usage: how many times a password can be used

• Storage: storing a password in an encrypted manner

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Implementing Password Policies

• Microsoft SQL Server 2000:

– Integrated server system

– Windows authentication mode

• NTLM:

– Challenge/response methodology

– Challenge is eight bytes of random data

– Response is a 24-byte DES-encrypted hash

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– Integrated server system

– Windows authentication mode

• NTLM:

– Challenge/response methodology

– Challenge is eight bytes of random data

– Response is a 24-byte DES-encrypted hash

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Implementing Password Policies

• Kerberos:

– A key known by client and server encrypts handshake data

– Requires a Key Distribution Center (KDC)

– Tickets

– Time must be synchronized networkwide

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• Permit or deny access to data or to perform database operations

• In Oracle:

– System privileges:

• Granted only by a database administrator

• Granted by a user with administration privileges

– Object privileges:

• Granted to a user by the schema owner

• Granted by a user with GRANT privileges

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Granting and Revoking User Privileges

• In SQL Server (4 levels); system/server privileges:

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– Grant permission using the GRANT statement

– Revoke permission using the REVOKE statement

– Enterprise Manager

– Deny permission using the DENY statement

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• In SQL Server:

– Table and database objects privileges:

• GRANT, REVOKE, and DENY

• EXECUTE permission

• Enterprise Manager (3 methods)

– Column privileges:

• GRANT, REVOKE, and DENY

• Enterprise Manager (2 methods)

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Creating, Assigning, and Revoking User Roles

• Role:

– Used to organize and administer privileges

– It is like a user, except it cannot own object

– Can be assigned privileges

– Can be assigned to users

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• In SQL Server; user-defined roles:

– Standard and application

– Create roles using SP_ADDROLE system-stored procedure

– Add members to a role using SP_ADDROLEMEMBER stored procedure

– Drop members from a role using SP_DROPROLEMEMBER stored procedure

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• In SQL Server (continued):

– User-defined roles (continued):

• Drop roles using SP_DROPROLE stored procedure

• Use Enterprise Manager

– Fixed server roles:

• Cannot be modified or created

• Add member to a role using SP_ADDSRVROLEMEMBER stored procedure

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– Fixed server roles (continued):

• Drop members from a role using SP_DROPSRVROLEMEMBER stored procedure

– Fixed database roles:

• Cannot be modified

• Give access to database administrative tasks

• Add members to a role using SP_ADDROLEMEMBER stored procedure

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– Fixed database roles (continued):

• Drop members from a role using SP_DROPROLEMEMBER stored procedure

– Public database role:

• Cannot be dropped

• Users automatically belong to this role

• Users cannot be dropped

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• Develop a secure environment:

– Never store passwords for an application in plaintext

– Change passwords frequently

– Use passwords at least eight characters long

– Pick a password that you can remember

– Use roles to control and administer privileges

– Report compromise or loss of a password

– Report any violation of company guidelines

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Best Practices

• Develop a secure environment (continued):

– Never give your password to anyone

– Never share your password with anyone

– Never give your password over the phone

– Never type your password in an e-mail

– Make sure your password is complex enough

– Use Windows integrated security mode

– In Windows 2000/3 domain use domain users and take advantage of Kerberos

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• When configuring policies:

– Require complex passwords with special characters in the first seven bytes

– Require a password length of at least eight

– Set an account lockout threshold

– Do not allow passwords to automatically reset

– Expire end-user passwords

– Do not expire application-user passwords

– Enforce a password history

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– Enhances password robustness

– Reduces likelihood of password breaking

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Best Practices

• GRANT and REVOKE

• Role is used to:

– Organize and administer privileges in an easy manner

– Role is like a user but cannot own objects

– Role can be assigned privileges

– GRANT and REVOKE

• Best practices for developing a secure environment

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• Tool must widely used by public

• May be the tool must frequently used by hackers:

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– Do not configure e-mail server on the same machine were sensitive data resides

– Do not disclose technical details about the

e-mail server

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• Common threats:

– File permission

– File sharing

• Files must be protected from unauthorized reading and writing actions

• Data resides in files; protecting files

protects data

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File Permissions

• Read, write, and execute privileges

• In Windows 2000:

– Change permission on the Security tab

on a file’s Properties dialog box

– Allow indicates grant

– Deny indicates revoke

Tiêu đề	Security Models
Tác giả	Trần Thị Kim Chi
Trường học	FPT University
Chuyên ngành	Database Security
Thể loại	Bài giảng

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