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.TH unlang 5 "01 Jul 2008" "" "FreeRADIUS Processing un-language"
.SH NAME
unlang \- FreeRADIUS Processing un\-language
.SH DESCRIPTION
FreeRADIUS supports a simple processing language in its configuration
files. We call it an "un-language" because the intention is NOT to
create yet another programming language. If you need something more
complicated than what is described here, we suggest using the Perl or
Python modules rlm_perl, or rlm_python.
The goal of the language is to allow simple policies to be written
with minimal effort. Those policies are then applied when a request
is being processed.
.SH KEYWORDS
The keywords for the language are a combination of pre-defined
keywords, and references to loadable module names. We document only
the pre-defined keywords here.
Subject to a few limitations described below, any keyword can appear
in any context. The language consists of a series of entries, each
one one line. Each entry begins with a keyword. Entries are
organized into lists. Processing of the language is line by line,
from the start of the list to the end. Actions are executed
per-keyword.
.IP module-name
A reference to the named module. When processing reaches this point,
the pre-compiled module is called. The module may succeed or fail,
and will return a status to "unlang" if so. This status can be tested
in a condition. See the "Simple Conditions" text in the CONDITIONS
section, and MODULE RETURN CODES, below.
.DS
chap # call the CHAP module
.br
sql # call the SQL module
.br
...
.DE
.IP if
.br
Checks for a particular condition. If true, the block after the
condition is processed. Otherwise, the block is ignored. See
CONDITIONS, below, for documentation on the format of the conditions.
.DS
if (condition) {
.br
...
.br
}
.DE
.IP else
.br
Define a block to be executed only if the previous "if" condition
returned false.
.DS
else {
.br
...
.br
}
.DE
.IP elsif
.br
Define a block to be executed only if the previous "if" condition
returned false, and if the specified condition evaluates to true.
.DS
elsif (condition) {
.br
...
.br
}
.DE
.IP switch
.br
Evaluate the given string, and choose the first matching "case"
statement inside of the current block. If the string is surrounded by
double quotes, it is expanded as described in the DATA TYPES section,
below.
No statement other than "case" can appear in a "switch" block.
.DS
switch "string" {
.br
...
.br
}
.DE
.IP case
.br
Define a static string to match a parent "switch" statement. The
strings given here are not expanded as is done with the parent
"switch" statement.
A "case" statement cannot appear outside of a "switch" block.
.DS
case string {
.br
...
.br
}
.DE
A default entry can be defined by omitting the static string. This
entry will be used if no other "case" entry matches. Only one default
entry can exist in a "switch" section.
.DS
case {
.br
...
.br
}
.DE
.IP update
.br
Update a particular attribute list, based on the attributes given in
the current block.
.DS
update <list> {
.br
attribute = value
.br
...
.br
}
.DE
The <list> can be one of "request", "reply", "proxy-request",
"proxy-reply", or "control". The "control" list is the list of
attributes maintainted internally by the server that controls how the
server processes the request. Any attribute that does not go in a
packet on the network will generally be placed in the "control" list.
For backwards compatibility with older versions, "check" is accepted
as a synonym for "control". The use of "check" is deprecated, and
will be removed in a future release.
For EAP methods with tunneled authentication sessions (i.e. PEAP and
EAP-TTLS), the inner tunnel session can also reference
"outer.request", "outer.reply", and "outer.control". Those references
allow you to address the relevant list in the outer tunnel session.
The only contents permitted in an "update" section are attributes and
values. The contents of the "update" section are described in the
ATTRIBUTES section below.
.IP redundant
This section contains a simple list of modules. The first module is
called when the section is being processed. If the first module
succeeds in its operation, then the server stops processing the
section, and returns to the parent section.
If, however, the module fails, then the next module in the list is
tried, as described above. The processing continues until one module
succeeds, or until the list has been exhausted.
Redundant sections can contain only a list of modules, and cannot
contain keywords that perform conditional operations (if, else, etc)
or update an attribute list.
.DS
redundant {
.br
sql1 # try this
.br
sql2 # try this only if sql1 fails.
.br
...
.br
}
.DE
.IP load-balance
This section contains a simple list of modules. When the section is
entered, one module is chosen at random to process the request. All
of the modules in the list should be the same type (e.g. ldap or sql).
All of the modules in the list should behave identically, otherwise
the load-balance section will return different results for the same
request.
Load-balance sections can contain only a list of modules, and cannot
contain keywords that perform conditional operations (if, else, etc)
or update an attribute list.
.DS
load-balance {
.br
ldap1 # 50% of requests go here
.br
ldap2 # 50% of requests go here
.br
}
.DE
In general, we recommend using "redundant-load-balance" instead of
"load-balance".
.IP redundant-load-balance
This section contains a simple list of modules. When the section is
entered, one module is chosen at random to process the request. If
that module succeeds, then the server stops processing the section.
If, however, the module fails, then one of the remaining modules is
chosen at random to process the request. This process repeats until
one module succeeds, or until the list has been exhausted.
All of the modules in the list should be the same type (e.g. ldap or
sql). All of the modules in the list should behave identically,
otherwise the load-balance section will return different results for
the same request.
Load-balance sections can contain only a list of modules, and cannot
contain keywords that perform conditional operations (if, else, etc)
or update an attribute list.
.DS
redundant-load-balance {
.br
ldap1 # 50%, unless ldap2 is down, then 100%
.br
ldap2 # 50%, unless ldap1 is down, then 100%
.br
}
.DE
.SH CONDITIONS
The conditions are similar to C conditions in syntax, though
quoted strings are supported, as with the Unix shell.
.IP Simple
conditions
.br
.DS
(foo)
.DE
Evalutes to true if 'foo' is a non-empty string (single quotes, double
quotes, or back-quoted). Also evaluates to true if 'foo' is a
non-zero number. Note that the language is poorly typed, so the
string "0000" can be interpreted as a numerical zero. This issue can
be avoided by comparings strings to an empty string, rather than by
evaluating the string by itself.
If the word 'foo' is not a quoted string, then it can be taken as a
reference to a named attribute. See "Referencing attribute lists",
below, for examples of attribute references. The condition evaluates
to true if the named attribute exists.
Otherwise, if the word 'foo' is not a quoted string, and is not an
attribute reference, then it is interpreted as a reference to a module
return code. The condition evaluates to true if the most recent
module return code matches the name given here. Valid module return
codes are given in MODULE RETURN CODES, below.
.IP Negation
.DS
(!foo)
.DE
Evalutes to true if 'foo' evaluates to false, and vice-versa.
.PP
Short-circuit operators
.RS
.br
.DS
(foo || bar)
.br
(foo && bar)
.DE
"&&" and "||" are short-circuit operators. "&&" evaluates the first
condition, and evaluates the second condition if and only if the
result of the first condition is true. "||" is similar, but executes
the second command if and only if the result of the first condition is
false.
.RE
.IP Comparisons
.DS
(foo == bar)
.DE
Compares 'foo' to 'bar', and evaluates to true if the comparison holds
true. Valid comparison operators are "==", "!=", "<", "<=", ">",
">=", "=~", and "!~", all with their usual meanings. Invalid
comparison operators are ":=" and "=".
.PP
Conditions may be nested to any depth, subject only to line length
limitations (8192 bytes).
.SH DATA TYPES
There are only a few data types supported in the language. Reference
to attributes, numbers, and strings. Any data type can appear in
stand-alone condition, in which case they are evaluated as described
in "Simple conditions", above. They can also appear (with some
exceptions noted below) on the left-hand or on the right-hand side of
a comparison.
.IP Numbers
Numbers are composed of decimal digits. Floating point, hex, and
octal numbers are not supported. The maximum value for a number is
machine-dependent, but is usually 32-bits, including one bit for a
sign value.
.PP
word
.RS
Text that is not enclosed in quotes is interpreted differently
depending on where it occurs in a condition. On the left hand side of
a condition, it is interpreted as a reference to an attribute. On the
right hand side, it is interpreted as a simple string, in the same
manner as a single-quoted string.
Using attribute references permits limited type-specific comparisons,
as seen in the examples below.
.DS
if (User-Name == "bob") {
.br
...
.br
if (Framed-IP-Address > 127.0.0.1) {
.br
...
.br
if (Service-Type == Login-User) {
.DE
.RE
.IP "strings"
.RS
Double-quoted strings are expanded by inserting the value of any
variables (see VARIABLES, below) before being evaluated. If
the result is a number it is evaluated in a numerical context.
String length is limited by line-length, usually about 8000
characters. A double quote character (") can be used in a string via
the normal back-slash escaping method. ("like \\"this\\" !")
.RE
.IP 'strings'
Single-quoted strings are evaluated as-is. Their values are not
expanded as with double-quoted strings above, and they are not
interpreted as attribute references.
.IP `strings`
Back-quoted strings are evaluated by expanding the contents of the
string, as described above for double-quoted strings. The resulting
command given inside of the string in a sub-shell, and taking the
output as a string. This behavior is much the same as that of Unix
shells.
Note that for security reasons, the input string is split into command
and arguments before variable expansion is done.
For performance reasons, we suggest that the use of back-quoted
strings be kept to a minimum. Executing external programs is
relatively expensive, and executing a large number of programs for
every request can quickly use all of the CPU time in a server. If you
believe that you need to execute many programs, we suggest finding
alternative ways to achieve the same result. In some cases, using a
real language may be sufficient.
.IP /regex/i
These strings are valid only on the right-hand side of a comparison,
and then only when the comparison operator is "=~" or "!~". They are
regular expressions, as implemented by the local regular expression
library on the system. This is usually Posix regular expressions.
The trailing 'i' is optional, and indicates that the regular
expression match should be done in a case-insensitive fashion.
If the comparison operator is "=~", then parantheses in the regular
expression will define variables containing the matching text, as
described below in the VARIABLES section.
.SH VARIABLES
Run-time variables are referenced using the following syntax
.DS
%{Variable-Name}
.DE
Note that unlike C, there is no way to declare variables, or to refer
to them outside of a string context. All references to variables MUST
be contained inside of a double-quoted or back-quoted string.
Many potential variables are defined in the dictionaries that
accompany the server. These definitions define only the name and
type, and do not define the value of the variable. When the server
receives a packet, it uses the packet contents to look up entries in
the dictionary, and instantiates variables with a name taken from the
dictionaries, and a value taken from the packet contents. This
process means that if a variable does not exist, it is usually because
it was not mentioned in a packet that the server received.
Once the variable is instantiated, it is added to an appropriate
attribute list, as described below. In many cases, attributes and
variables are inter-changeble, and are often talked about that way.
However, variables can also refer to run-time calls to modules, which
may perform operations like SQL SELECTs, and which may return the
result as the value of the variable.
.PP
Referencing attribute lists
.RS
Attribute lists may be referenced via the following syntax
.DS
%{<list>:Attribute-Name}
.DE
Where <list> is one of "request", "reply", "control", "proxy-request",
"proxy-reply", or "outer.request", "outer.reply", "outer.control",
"outer.proxy-request", or "outer.proxy-reply". just as with the
"update" section, above. The "<list>:" prefix is optional, and if
omitted, is assumed to refer to the "request" list.
When a variable is encountered, the given list is examined for an
attribute of the given name. If found, the variable reference in the
string is replaced with the value of that attribute. Some examples are:
.DS
%{User-Name}
.br
%{request:User-Name} # same as above
.br
%{reply:User-Name}
.br
%{outer.reqest:User-Name} # from inside of a TTLS/PEAP tunnel
.DE
.RE
.PP
Results of regular expression matches
.RS
If a regular expression match has previously been performed, then the
special variable %{0} will contain a copy of the input string. The
variables %{1} through %{8} will contain the substring matches,
starting from the left-most parantheses, and onwards. If there are
more than 8 parantheses, the additional results will not be placed
into any variables.
.RE
.PP
Obtaining results from databases
.RS
It is useful to query a database for some information, and to use the
result in a condition. The following syntax will call a module, pass
it the given string, and replace the variable reference with the
resulting string returned from the module.
.DS
%{module: string ...}
.DE
The syntax of the string is module-specific. Please read the module
documentation for additional details.
.RE
.PP
Conditional Syntax
.RS
Conditional syntax similar to that used in Unix shells may also be
used.
.IP %{%{Foo}:-bar}
If %{Foo} has a value, returns that value.
.br
Otherwise, returns literal string "bar".
.IP %{%{Foo}:-%{Bar}}
If %{Foo} has a value, returns that value.
.br
Otherwise, returns the expansion of %{Bar}.
These conditional expansions can be nested to almost any depth, such
as with %{%{One}:-%{%{Two}:-%{Three}}}
.RE
.PP
String lengths and arrays
.RS
Similar to a Unix shell, there are ways to reference string lenths,
and the second or more instance of an attribute in a list. If you
need this functionality, we recommend using a real language.
.IP %{#string}
The number of characters in %{string}. If %{string} is not
set, then the length is not set.
e.g. %{#Junk-junk:-foo} will yeild the string "foo".
.IP %{Attribute-Name[index]}
Reference the N'th occurance of the given attribute. The syntax
%{<list>:Attribute-Name[index]} may also be used. The indexes start
at zero. This feature is NOT available for non-attribute dynamic
translations, like %{sql:...}.
For example, %{User-Name[0]} is the same as %{User-Name}
The variable %{Cisco-AVPair[2]} will reference the value of the
THIRD Cisco-AVPair attribute (if it exists) in the request packet,
.IP %{Attribute-Name[#]}
Returns the total number of attributes of that name in the relevant
attribute list. The number will usually be between 0 and 200.
For most requests, %{request:User-Name[#]} == 1
.IP %{Attribute-Name[*]}
Expands to a single string, with the value of each array
member separated by a newline.
.IP %{#Attribute-Name[index]}
Expands to the length of the string %{Attribute-Name[index]}.
.SH ATTRIBUTES
The attribute lists described above may be edited by listing one or
more attributes in an "update" section. Once the attributes have been
defined, they may be referenced as described above in the VARIABLES
section.
The following syntax defines attributes in an "update" section. Each
attribute and value has to be all on one line in the configuration
file. There is no need for commas or semi-colons after the value.
.DS
Attribute-Name = value
.DE
.PP
Attribute names
.RS
The Attribute-Name must be a name previously defined in a dictionary.
If an undefined name is used, the server will return an error, and
will not start.
.RE
.IP Operators
The operator used to assign the value of the attribute may be one of
the following, with the given meaning.
.RS
.IP =
Add the attribute to the list, if and only if an attribute of the same
name is already present in that list.
.IP :=
Add the attribute to the list. If any attribute of the same name is
already present in that list, its value is replaced with the value of
the current attribute.
.IP +=
Add the attribute to the tail of the list, even if attributes of the
same name are already present in the list.
.RE
.PP
Enforcement and Filtering Operators
.RS
The following operators may also be used in addition to the ones
listed above. Their function is to perform enforcement or filtering
on attributes in a list.
.IP -=
Remove all matching attributes from the list. Both the attribute name
and value have to match in order for the attribute to be removed from
the list.
.IP ==
Remove all non-matching attributes from the list. Both the attribute
name and value have to match in order for the attribute to remain in
the list.
Note that this operator is very different than the '=' operator listed
above!
.IP <=
Enforce that the integer value of the attribute is less than or equal
to the value given here. If there is no attribute of the same name in
the list, the attribute is added with the given value, is with "+=".
If an attribute in the list exists, and has value less than given
here, it's value is unchanged. If an attribute in the list exists,
and has a value greater than given here, then that value is replaced
with the one given here.
This operator is valid only for attributes of integer type.
.IP >=
Enforce that the integer value of the attribute is greater than or
equal to the value given here. If there is no attribute of the same
name in the list, the attribute is added with the given value, is with
"+=". If an attribute in the list exists, and has value greater than
given here, it's value is unchanged. If an attribute in the list
exists, and has value less than given here, then that value is
replaced with the one given here.
This operator is valid only for attributes of integer type.
.RE
.IP Values
.br
The format of the value is attribute-specific, and is usually a
string, integer, IP address, etc. Prior to the attribute being
instantiated, the value may be expanded as described above in the DATA
TYPES section, above. This flexibility means that, for example, you
can assign an IP address value to an attribute by specifying the IP
address directly, or by having the address returned from a database
query, or by having the address returned as the output of a program
that is executed.
When string values are finally assigned to a variable, they can have a
maximum length of 253 characters. This limit is due in part to both
protocol and internal server requirements. That is, the strings in
the language can be nearly 8k in length, say for a long SQL query.
However, the output of that SQL query should be no more than 253
characters in length.
.SH OTHER KEYWORDS
Other keywords in the language are taken from the names of modules
loaded by the server. These keywords are dependent on both the
modules, and the local configuration.
Some use keywords that are defined in the default configuration file
are:
.IP fail
Cause the request to be treated as if a database failure had occurred.
.IP noop
Do nothing. This also serves as an instruction to the configurable
failover tracking that nothing was done in the current section.
.IP ok
Instructs the server that the request was processed properly. This
keyword can be used to over-ride earlier failures, if the local
administrator determines that the faiures are not catastrophic.
.IP reject
Causes the request to be immediately rejected
.SH MODULE RETURN CODES
When a module is called, it returns one of the following codes to
"unlang", with the following meaning.
.DS
notfound information was not found
.br
noop the module did nothing
.br
ok the module succeeded
.br
updated the module updated the request
.br
fail the module failed
.br
reject the module rejected the request
.br
userlock the user was locked out
.br
invalid the configuration was invalid
.br
handled the module has handled the request itself
.DE
These return codes can be tested for in a condition, as described
above in the CONDITIONS section.
.SH FILES
/etc/raddb/radiusd.conf
.SH "SEE ALSO"
.BR radiusd.conf (5),
.BR dictionary (5)
.SH AUTHOR
Alan DeKok <aland@deployingradius.com>