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SQL Anywhere 11.0.0 » SQL Anywhere Server - Database Administration » Security » Keeping your data secure » Controlling database access

 

Increasing password security

Passwords are an important part of any database security system. To be secure, passwords must be difficult to guess, and they must not be easily accessible on users' hard drives or other locations. SQL Anywhere passwords are always case sensitive. You can specify a function used for password authentication with the verify_password_function option. See verify_password_function option [database].

Implement a login policy

Use a login policy to control the frequency of user password changes and to specify the number of login attempts allowed before an account is locked. See Managing login policies overview, or CREATE LOGIN POLICY statement.

Change the default user ID and password

The default user ID and password for a newly created database is DBA and sql. You should change this password before deploying the database.

Implement minimum password lengths

By default, passwords can be any length. For greater security, you can enforce a minimum length requirement on all new passwords to disallow short (and therefore easily guessed) passwords. You do this by setting the min_password_length database option to a value greater than zero. The following statement enforces passwords to be at least 8 bytes long.

SET OPTION PUBLIC.min_password_length = 8;

See min_password_length option [database].

Implement password expiration

By default, database passwords never expire. You can use a login policy to implement password expiry. See Managing login policies overview.

Do not include passwords in ODBC data sources

Passwords are the key to accessing databases. They should not be easily available to unauthorized people in a security-conscious environment.

When you create an ODBC data source or a Sybase Central connection profile, you can optionally include a password. Avoid including passwords to ensure that they are not viewed by unauthorized users.

See Creating an ODBC data source.

Encrypt configuration files containing passwords

When you create a configuration file, you can optionally include password information. To protect your passwords, consider hiding the contents of configuration files with simple encryption, using the File Hiding (dbfhide) utility. See File Hiding utility (dbfhide).

Use password verification

You can use the verify_password_function option to specify a function that implements password rules. See verify_password_function option [database].

The following example defines a table and function and sets some login policy options. Together they implement advanced password rules that include requiring certain types of characters in the password, disallowing password reuse, and expiring passwords. The function is called by the database server with the verify_password_function option when a user ID is created or a password is changed. The application can call the procedure specified by the post_login_procedure option to report that the password should be changed before it expires.

The code for this sample is also available in the following location: samples-dir\SQLAnywhere\SQL\verify_password.sql. (For information about samples-dir, see Samples directory.)

-- This example defines a function that implements advanced password rules 
-- including requiring certain types of characters in the password and 
-- disallowing password reuse. The f_verify_pwd function is called by the 
-- server using the verify_password_function option when a user ID is 
-- created or a password is changed.  
--
-- The "root" login profile is configured to expire passwords every 180 days
-- and lock non-DBA accounts after 5 consecutive failed login attempts.
--
-- The application may call the procedure specified by the 
-- post_login_procedure option to report that the password should be changed 
-- before it expires.


-- only DBA should have permissions on this table
CREATE TABLE DBA.t_pwd_history(
        pk          INT         DEFAULT AUTOINCREMENT PRIMARY KEY,
        user_name   CHAR(128),          -- the user whose password is set
        pwd_hash    CHAR(32) );         -- hash of password value to detect
                                        -- duplicate passwords

-- called whenever a non-NULL password is set
-- to verify the password conforms to password rules
CREATE FUNCTION DBA.f_verify_pwd( uid     VARCHAR(128),
                                  new_pwd VARCHAR(255) )
RETURNS VARCHAR(255)
BEGIN
    -- a table with one row per character in new_pwd
    DECLARE local temporary table pwd_chars(
            pos INT PRIMARY KEY,    -- index of c in new_pwd
            c   CHAR( 1 CHAR ) );   -- character
    -- new_pwd with non-alpha characters removed
    DECLARE pwd_alpha_only      CHAR(255);
    DECLARE num_lower_chars     INT;

    -- enforce minimum length (can also be done with
    -- min_password_length option)
    IF length( new_pwd ) < 6 THEN
        RETURN 'password must be at least 6 characters long';
    END IF;

    -- break new_pwd into one row per character
    INSERT INTO pwd_chars SELECT row_num, substr( new_pwd, row_num, 1 )
                            FROM dbo.RowGenerator
                            WHERE row_num <= length( new_pwd );

    -- copy of new_pwd containing alpha-only characters
    SELECT list( c, '' ORDER BY pos ) INTO pwd_alpha_only
        FROM pwd_chars WHERE c BETWEEN 'a' AND 'z' OR c BETWEEN 'A' AND 'Z';

    -- number of lower case characters IN new_pwd
    SELECT count(*) INTO num_lower_chars
        FROM pwd_chars WHERE CAST( c AS BINARY ) BETWEEN 'a' AND 'z';

    -- enforce rules based on characters contained in new_pwd
    IF ( SELECT count(*) FROM pwd_chars WHERE c BETWEEN '0' AND '9' )
           < 1 THEN
        RETURN 'password must contain at least one numeric digit';
    ELSEIF length( pwd_alpha_only ) < 2 THEN
        RETURN 'password must contain at least two letters';
    ELSEIF num_lower_chars = 0
           OR length( pwd_alpha_only ) - num_lower_chars = 0 THEN
        RETURN 'password must contain both upper- and lowercase characters';
    END IF;

    -- not the same as any user name
    -- (this could be modified to check against a disallowed words table)
    IF EXISTS( SELECT * FROM SYS.SYSUSER
                    WHERE lower( user_name ) IN ( lower( pwd_alpha_only ),
                                                  lower( new_pwd ) ) ) THEN
        RETURN 'password or only alphabetic characters in password ' ||
               'must not match any user name';
    END IF;

    -- not the same as any previous password for this user
    IF EXISTS( SELECT * FROM t_pwd_history
                    WHERE user_name = uid
                      AND pwd_hash = hash( uid || new_pwd, 'md5' ) ) THEN
        RETURN 'previous passwords cannot be reused';
    END IF;

    -- save the new password
    INSERT INTO t_pwd_history( user_name, pwd_hash )
        VALUES( uid, hash( uid || new_pwd, 'md5' ) );

    RETURN( NULL );
END;

ALTER FUNCTION DBA.f_verify_pwd SET HIDDEN;
GRANT EXECUTE ON DBA.f_verify_pwd TO PUBLIC;
SET OPTION PUBLIC.verify_password_function = 'DBA.f_verify_pwd';


-- All passwords expire in 180 days.  Expired passwords can be changed
-- by the user using the NewPassword connection parameter.
ALTER LOGIN POLICY root password_life_time = 180;

-- If an application calls the procedure specified by the 
-- post_login_procedure option, then the procedure can be used to warn 
-- the user that their password is about to expire.  In particular, 
-- Interactive SQL and Sybase Central call the 
-- post_login_procedure system procedure.
ALTER LOGIN POLICY root password_grace_time = 30;

-- Five consecutive failed login attempts will result in a non-DBA 
-- user ID being locked.
ALTER LOGIN POLICY root max_failed_login_attempts = 5;