Transcript ON securable

Database Security
An Overview
with some SQL
Copyright © 2013 Curt Hill
The DataBase
Administrator
• The security of a DBMS rests with
the DBA
• This person owns the account that
has all the power
• The DBA giveth and the DBA taketh
away the permissions
• When security fails, then the DBA is
fired
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What needs protection?
• Confidentiality
– Only authorized parties are allowed to
view material
• Includes printing and display
– Sometimes just revealing the existence
of a person/item is a breach of security
• Integrity
– The ability to modify should be rarer
than the ability to view
• Availability
– The system can be made available to
authorized parties
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Why?
• Competitive advantage
– We need to protect our corporate data
which may be of help to our
competitors
– Customers trust us with their data
• Laws
– The US has numerous laws concerning
who may and who may not access
confidential data
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What Do We Do?
• Authentication
– Force users to login, have good
passwords and change them
occasionally
• Restrict access
– Permissions or privileges restrict what
a particular user may do
• Encryption
– Prevents the database from being
accessed outside of the DBMS
• Logging
– Helps to understand breaches
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Access Control
• We can restrict what a user may see
or do
• This often focusses around the
notion of roles and permissions
• Like much in the SQL domain, not
very standard
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SQL Server
• SQL Server believes in roles
• Each role expresses the relationship
a login has to objects
• Determines what the user may do
• The notion of a role is to ease the
management of a permissions
• These permissions may be given or
taken away from individuals or to
every user who has the same role
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Role types
• There are:
– Predefined roles connected to a
particular database
– Fixed roles connected to entire server
– User created roles which are
connected to a particular database
• A few of these are considered in the
next screens
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Predefined roles
• db_owner: Members have full
access
• db_datareader: Members can read
all data
• db_datawriter: Members can add,
delete, or modify data in the tables
• db_securityadmin: Members can
modify role membership and
manage permissions
• db_bckupoperator: Members can
back up the database
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Fixed roles
• SysAdmin: Any member can perform
any action on the server
• ServerAdmin: Any member can set
configuration options on the server
• Security Admin: Any member can
manage server security
• DbCreator: Any member can create,
alter, drop, and restore databases.
• BulkAdmin: Any member can run the
bulk insert command
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Assigning Roles
• Like many things in SQL Server
things can be done by the
Management Console or by SQL
command
– Many of the SQL commands in this area
have a unique syntax for SQL Server
• The SQL command is Create Role
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Creating a role
• Syntax is:
Create Role role_name
Authorization user
• The role_name is the new role
• User is the user which owns this role
– This may be left out (including
Authorization) then the current user
owns this role
• This type of role is then connected
with database objects
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Now what?
• Once roles are created we may give
them permissions
– The reserved word is Grant
• With Grant we connect a permission
with a user or role
• Consider the syntax next
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Simplified Grant Syntax
GRANT
permission [ ( column [ ,...n ] ) ] [ ,...n
]
[ ON securable ]
TO principal [ ,...n ]
[ WITH GRANT OPTION ] [ AS
principal ]
• Where
– Permission is what they are able to do
– Securable may be a table, database,
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Curt Hill others
stored procedure
among
Permissions
• The permissions depend on the
object considered
• For a table or view they include:
DELETE, INSERT, REFERENCES,
SELECT, UPDATE
• For a stored procedure only
EXECUTE
• For a database there are many
– One for most actions
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An Example
• Consider the following:
Create Role TestRole
Grant SELECT ON Faculty
TO TestRole
Grant Update ON Faculty
TO TestRole
• Permissions not granted are
unavailable
• The table may need to be qualified
by the database
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Deny
• Blocks a permission
• Usually used to remove a single
permission
• Syntax is similar to Grant
• Example:
Deny Update ON Faculty
TO TestRole
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Revoke
• Removes the permission specified
by a Grant or Deny
• Similar syntax
• Example
Revoke Select on Faculty
from TestRole
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Oracle
• Not the number 1 database without
cause
• Has all the capabilities of the normal
database
• Implements:
–
–
–
–
Create Role
Grant
Deny
Revoke
• Although not quite the same syntax
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Guidelines
• Restrict permissions to those who
actually need them
– Common mistake is for too many users
to have excessive privileges
• Web access is usually through a
predefined login
– Secure it to prevent issues
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Injection Attacks
• A common problem is that user input
will be used to construct a SQL
command
• An injection attack is using cleverly
crafted bad input to subvert the
process
• Consider the next screen for an
example
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Normally
• Suppose that we have a web form
and it asks for an ID that is to come
from the faculty table
• Suppose we read that value into a
JavaScript variable and then build a
JavaScript string with it:
stmt = ‘select * from faculty
where naid = ‘ + input
• Usually the user types in a number
and stmt contains:
select * from faculty
where naid = 512
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Attack!
• In the above you get zero or one
rows depending on whether 512
may be found
• Instead of typing in
512
a hacker types in:
1 or 1 = 1
• Now the statement becomes:
select * from faculty
where naid = 1 or 1 = 1
• The whole table is the result
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Defense
• The code in the web page cannot
just blindly insert user input
characters into a SQL statement
• First the user input characters must
be examined
• Suspicious or unexpected
characters need to be removed and
the query rejected
• Some systems have functions to
automate this
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Statistical Databases
• The Census Bureau, among others,
maintains several statistical
databases
– These are generally publicly available
• The purpose is to provide for
demographic research
– Useful for governmental and market
research
• The inherent goal is that no personal
information may be observed
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Attacking
• It is possible to make a query that
shows us an individual’s personal
data
• Find the average salary of all the
people who have a title of professor
at VCSU who started in 1995 and a
degree in CS
– This is me and me only
• The inherent confidentiality
requirement has been violated
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Defense
• The above is an inference attack
– Attempt to get data on an individual
from a statistical database
• The usual approach to an inference
attack is to restrict queries that end
up with just a few individuals
• Make queries return a threshold
number’s worth of individuals before
release
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