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 schemas are available in raddb/sql/<DB>/*, where <DB> is the
name of the database (mysql, postgresql, etc.)
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
Fall-Through is set in the radreply table
d. 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 OR
b. Fall-Through was set in the last group's reply 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.
For any fairly complex setup, it is likely that most of the actual
processing will be done in the groups. In these cases, the user entry in
radcheck will be of limited use except for things like setting the user's
password. So, one might have the following setup:
radcheck table:
joeuser Cleartext-Password := somepassword
radreply table:
joeuser Fall-Through = Yes
radgroupcheck table:
Check items for various connection scenarios
radgroupreply table:
reply items for the groups
usergroup table:
joeuser WLANgroup 1(this is the priority)
joeuser PPPgroup 2
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
...
}