# Working with JDBCRealm

## What is JDBCRealm?

Is an implementation of a tomcat 3.X Realm that use a set of configurable tables inside a RDMS to store user's data, this tables are accessed by means of standard JDBC drivers.
The passwords can be stored as digested ( using standard Java's MessageDigest ) or in plain form.
All the parameters, drivers, tables, and columns are user configurable.

## Example Config for JDBCRealm

This is an example of how to set up a JDBC Realm. For this example I used the MySQL JDBC driver.

### 1. Create a database.

> I made the database named "authority"

### 2. Create needed tables.

> #### 1. The user table.

> > This table needs the user's name and a password field. In the example I use "users" for the table name, "user_name" for the column that holds the user's name, and "user_pass" for the user's password.

> #### 2. The role table.

> > This table needs the role's set up that will be in any deployment descriptor that is managed under the container this Realm is in. In the example I use "roles" as the table name and "role_name" as the role's name. NB: This table doesn't get used at all by tomcat.

> #### 3. The role to user table.

> > This table joins a set of roles to a single user. In the example the table name is "user_roles", the role's name is "role_name" , and the user's name is assumed to have the same column name as in the user's table ("user_name" in this example.

> > Here is the SQL I used to create the tables:

    create table users
    (
      user_name varchar(15) not null primary key,
      user_pass varchar(15) not null
    );

    create table roles
    (
      role_name varchar(15) not null primary key
    );

    create table user_roles
    (
      user_name varchar(15) not null,
      role_name varchar(15) not null,
      primary key( user_name, role_name )
    );

> > Here is sample output from the tables:

    mysql> select * from users;
    +-----------+-----------+
    | user_name | user_pass |
    +-----------+-----------+
    | tomcat    | tomcat    |
    | user1     | tomcat    |
    | user2     | tomcat    |
    | user3     | tomcat    |
    +-----------+-----------+
    4 rows in set (0.00 sec)

    mysql>
    mysql> select * from roles;
    +------------+
    | role_name  |
    +------------+
    | tomcat     |
    | role1      |
    +------------+
    2 rows in set (0.02 sec)

    mysql>

    mysql> select * from user_roles;
    +------------+-----------+
    | role_name  | user_name |
    +------------+-----------+
    | tomcat     | user1     |
    | role1      | user2     |
    | tomcat     | tomcat    |
    | role1      | tomcat    |
    +------------+-----------+
    4 rows in set (0.00 sec)

    mysql>

### 3. Configure Tomcat

> Add the information to the server.xml file. For this example I used this entry inside:

`<JDBCRealm" debug="99" driverName="org.gjt.mm.mysql.Driver" connectionURL="jdbc:mysql://localhost/authority?user=test;password=test" userTable="users" userNameCol="user_name" userCredCol="user_pass" userRoleTable="user_roles" roleNameCol="role_name" />`

The meaning of the attributes is as follow:

attribute | Meaning
--- | ---
driverName | The name of the driver needed to connect to the database
connectionURL | The connection URL used to connect to the database
userTable | The user's tables
userNameCol | The column in the user's table that contains the name
userCredCol | The column in the user's table that contains the password
userRoleTable | The user's roles table
roleNameCol | The column in the user's table that contains a role given to a user
connectionName | The name to use when connecting to the database. (Optional)
connectionPassword | The password to use when connecting to the database. (Optional)
digest | The algorithm used for digest passwords or "No" for plain passwords, the values can be "MD5", "MD2", "SHA", etc... (Optional)

Done!!

## Using digested passwords

To use digested password you need to store them digested. To achieve this, you will need to use the same digest strategies that JDBCrealm uses to store the passwords. Iinside JDBCRealm there is a static method with signature `final public static String digest(String password,String algorithm)`. This method is provided as a tool to be used outside JDBCRealm by an application that wants to generate digested passwords readable by JDBCRealm.

The class JDBCRealm contains a main method, so it can be used as an application to generate digests and print them to stdout. Usage is:
`java org.apache.tomcat.modules.aaa.RealmBase -a <algorithm> <password> [<password> ...]`
where <algorithm> is a supported message digest algorithm, e.g. MD5, and <password> is a plaintext password to be digested.

Note: the jar where RealmBase class can be found is %TOMCAT_HOME%/lib/container/tomcat_modules.jar

## Hints

- Make sure that the JDBC driver is in the lib/container directory.
- If you have problem connecting you can specify connectionName and connectionPassword

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