	SQL Module

0. Introduction

  The SQL module is composed of two parts: a generic SQL front-end
  (rlm_sql), and a series of database-dependent back-end drivers,
  (rlm_sql_mysql, rlm_sql_postgresql, etc.)

  In order to build the drivers, you MUST ALSO install the development
  versions of the database.  That is, you must have the appropriate
  header files and client libraries for (say) MySQL.  The
  rlm_sql_mysql driver is NOT a complete MySQL client implementation.
  Instead, it is a small 'shim' between the FreeRADIUS rlm_sql module,
  and the MySQL client libraries.


  In general, the SQL schemas mirror the layout of the 'users' file.
  So for configuring check items and reply items, see 'man 5 users',
  and the examples in the 'users' file.


1. Schema and usage

  The SQL module employs two sets of check and reply item tables for
  processing in the authorization stage.  One set of tables (radcheck and
  radreply) are specific to a single user.  The other set of tables
  (radgroupcheck and radgroupreply) is used to apply check and reply items
  to users that are members of a certain SQL group.  The usergroup table
  provides the list of groups each user is a member of along with a priority
  field to control the order in which groups are processed.

  When a request comes into the server and is processed by the SQL module,
  the flow goes something like this:

  1. Search the radcheck table for any check attributes specific to the user
  2. If check attributes are found, and there's a match, pull the reply items
     from the radreply table for this user and add them to the reply
  3. Group processing then begins if any of the following conditions are met:
     a. The user IS NOT found in radcheck
     b. The user IS found in radcheck, but the check items don't match
     c. The user IS found in radcheck, the check items DO match AND
	the read_groups directive is set to 'yes'
  4. If groups are to be processed for this user, the first thing that is
     done is the list of groups this user is a member of is pulled from the
     usergroup table ordered by the priority field.  The priority field of
     the usergroup table allows us to control the order in which groups are
     processed, so that we can emulate the ordering in the users file.  This
     can be important in many cases.
  5. For each group this user is a member of, the corresponding check items
     are pulled from radgroupcheck table and compared with the request.  If
     there is a match, the reply items for this group are pulled from the
     radgroupreply table and applied.
  6. Processing continues to the next group IF:
     a. There was not a match for the last group's check items
     (The above is exactly the same as in the users file)
  7. Finally, if the user has a User-Profile attribute set or the Default
     Profile option is set in the sql.conf, then steps 4-6 are repeated for
     the groups that the profile is a member of.

  A web page with some helpful documentation is:

	http://www.frontios.com/freeradius.html

  NOTE: this page may be slightly out of date when dealing with the database
        schema


2. What NOT to do.

  One of the fields of the SQL schema is named 'op'  This is for the
  'operator' used by the attributes.  e.g.:

   Framed-IP-Address  =      1.2.3.4
   ^ ATTRIBUTE ----^  ^ OP   ^ VALUE

  If you want the server to be completely misconfigured, and to never
  do what you want, leave the 'op' field blank.  If you want to be
  rudely told to RTFM, then post questions on the mailing list, asking

  "why doesn't my SQL configuration work when I leave the 'op' field empty?"


  The short answer is that with the op field empty, the server does
  not know what you want it to do with the attribute.  Should it be
  added to the reply?  Maybe you wanted to compare the operator to one
  in the request?   The server simply doesn't know.

  So put a value in the field.  The value is the string form of the
  operator: "=", ">=", etc.  See Section 4, below, for more details.


3. Authentication versus Authorization

  Many people ask if they can "authenticate" users to their SQL
  database.  The answer to this question is "You're asking the wrong
  question."

  An SQL database stores information.  An SQL database is NOT an
  authentication server.  The ONLY users who should be able to
  authenticate themselves to the database are the people who
  administer it.  Most administrators do NOT want every user to be
  able to access the database, which means that most users will not be
  able to "authenticate" themselves to the database.

  Instead, the users will have their authorization information (name,
  password, configuration) stored in the database.  The configuration
  files for FreeRADIUS contain a username and password used to
  authenticate FreeRADIUS to the SQL server.  (See raddb/sql.conf).
  Once the FreeRADIUS authentication server is connected to the SQL
  database server, then FreeRADIUS can pull user names and passwords
  out of the database, and use that information to perform the
  authentication.

4. Operators

 The list of operators is given below.

 Op	Example and documentation
 --	-------------------------

 =	"Attribute = Value"

	Not allowed as a check item for RADIUS protocol attributes.  It is
	allowed for server configuration attributes (Auth-Type, etc), and sets
	the value of on attribute, only if there is no other item of the
	same attribute.

	As a reply item, it means "add the item to the reply list, but
	only if there is no other item of the same attribute."


 :=	"Attribute := Value"

	Always matches as a check item, and replaces in the
	configuration items any attribute of the same name.  If no
	attribute of that name appears in the request, then this
	attribute is added.

	As a reply item, it has an identical meaning, but for the
	reply items, instead of the request items.

 ==	"Attribute == Value"

	As a check item, it matches if the named attribute is present
	in the request, AND has the given value.

	Not allowed as a reply item.


 +=	"Attribute += Value"

	Always matches as a check item, and adds the current attribute
	with value to the list of configuration items.

	As a reply item, it has an identical meaning, but the
	attribute is added to the reply items.


 !=	"Attribute != Value"

	As a check item, matches if the given attribute is in the
	request, AND does not have the given value.

	Not allowed as a reply item.


 >	"Attribute > Value"

	As a check item, it matches if the request contains an
	attribute with a value greater than the one given.

	Not allowed as a reply item.


 >=	"Attribute >= Value"

	As a check item, it matches if the request contains an
	attribute with a value greater than, or equal to the one
	given.

	Not allowed as a reply item.

 <	"Attribute < Value"

	As a check item, it matches if the request contains an
	attribute with a value less than the one given.

	Not allowed as a reply item.


 <=	"Attribute <= Value"

	As a check item, it matches if the request contains an
	attribute with a value less than, or equal to the one given.

	Not allowed as a reply item.


 =~	"Attribute =~ Expression"

	As a check item, it matches if the request contains an
	attribute which matches the given regular expression.  This
	operator may only be applied to string attributes.

	Not allowed as a reply item.


 !~	"Attribute !~ Expression"

	As a check item, it matches if the request contains an
	attribute which does not match the given regular expression.
	This operator may only be applied to string attributes.

	Not allowed as a reply item.


 =*	"Attribute =* Value"

	As a check item, it matches if the request contains the named
	attribute, no matter what the value is.

	Not allowed as a reply item.


 !*	"Attribute !* Value"

	As a check item, it matches if the request does not contain
	the named attribute, no matter what the value is.

	Not allowed as a reply item.

5. Instances

  Just like any other module, multiple instances of the rlm_sql
  module can be defined and used wherever you like.

  The default .conf files for the different database types,
  contain 1 instance without a name like so:
  sql {
    ...
  }

  You can create multiple named instances like so:
  sql sql_instance1 {
    ...
  }
  sql sql_instance2 {
    ...
  }

  And then you can use a specific instance in radiusd.conf, like
  so:
  authorize {
    ...
    sql_instance1
    ...
  }
  accounting {
    ...
    sql_instance1
    sql_instance2
    ...
  }

