freebsd-dev/lib/libradius/libradius.3

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.Dd July 29, 1998
.Dt LIBRADIUS 3
.Os FreeBSD
.Sh NAME
.Nm libradius
.Nd RADIUS client library
.Sh SYNOPSIS
.Fd #include <radlib.h>
.Ft int
.Fn rad_add_server "struct rad_handle *h" "const char *host" "int port" "const char *secret" "int timeout" "int max_tries"
.Ft void
.Fn rad_close "struct rad_handle *h"
.Ft int
.Fn rad_config "struct rad_handle *h" "const char *file"
.Ft int
.Fn rad_continue_send_request "struct rad_handle *h" "int selected" "int *fd" "struct timeval *tv"
.Ft int
.Fn rad_create_request "struct rad_handle *h" "int code"
.Ft struct in_addr
.Fn rad_cvt_addr "const void *data"
.Ft u_int32_t
.Fn rad_cvt_int "const void *data"
.Ft char *
.Fn rad_cvt_string "const void *data" "size_t len"
.Ft int
.Fn rad_get_attr "struct rad_handle *h" "const void **data" "size_t *len"
.Ft int
.Fn rad_init_send_request "struct rad_handle *h" "int *fd" "struct timeval *tv"
.Ft struct rad_handle *
.Fn rad_open "void"
.Ft int
.Fn rad_put_addr "struct rad_handle *h" "int type" "struct in_addr addr"
.Ft int
.Fn rad_put_attr "struct rad_handle *h" "int type" "const void *data" "size_t len"
.Ft int
.Fn rad_put_int "struct rad_handle *h" "int type" "u_int32_t value"
.Ft int
.Fn rad_put_string "struct rad_handle *h" "int type" "const char *str"
.Ft int
.Fn rad_send_request "struct rad_handle *h"
.Ft const char *
.Fn rad_strerror "struct rad_handle *h"
.Sh DESCRIPTION
The
.Nm
library implements the client side of the Remote Authentication
Dial In User Service (RADIUS).  RADIUS, defined in RFC 2138, allows
clients to perform authentication by means of network requests to
remote authentication servers.
.Sh INITIALIZATION
To use the library, an application must first call
.Fn rad_open
to obtain a
.Va struct rad_handle * ,
which provides the context for subsequent operations.
Calls to
.Fn rad_open
always succeed unless insufficient virtual memory is available.  If
the necessary memory cannot be allocated,
.Fn rad_open
returns
.Dv NULL .
.Pp
Before issuing any RADIUS requests, the library must be made aware
of the servers it can contact.  The easiest way to configure the
library is to call
.Fn rad_config .
.Fn rad_config
causes the library to read a configuration file whose format is
described in
.Xr radius.conf 5 .
The pathname of the configuration file is passed as the
.Va file
argument to
.Fn rad_config .
This argument may also be given as
.Dv NULL ,
in which case the standard configuration file
.Pa /etc/radius.conf
is used.
.Fn rad_config
returns 0 on success, or -1 if an error occurs.
.Pp
The library can also be configured programmatically by calls to
.Fn rad_add_server .
The
.Va host
parameter specifies the server host, either as a fully qualified
domain name or as a dotted-quad IP address in text form.
The
.Va port
parameter specifies the UDP port to contact on the server.  If
.Va port
is given as 0, the library looks up the
.Ql radius/udp
service in the network services database, and uses the port found
there.  If no entry is found, the library uses port 1812, the standard
RADIUS port.  The shared secret for the server host is passed to the
.Va secret
parameter.
It may be any NUL-terminated string of bytes.  The RADIUS protocol
ignores all but the leading 128 bytes of the shared secret.
The timeout for receiving replies from the server is passed to the
.Va timeout
parameter, in units of seconds.  The maximum number of repeated
requests to make before giving up is passed into the
.Va max_tries
parameter.
.Fn rad_add_server
returns 0 on success, or -1 if an error occurs.
.Pp
.Fn rad_add_server
may be called multiple times, and it may be used together with
.Fn rad_config .
At most 10 servers may be specified.
When multiple servers are given, they are tried in round-robin
fashion until a valid response is received, or until each server's
.Va max_tries
limit has been reached.
.Sh CREATING A RADIUS REQUEST
A RADIUS request consists of a code specifying the kind of request,
and zero or more attributes which provide additional information.  To
begin constructing a new request, call
.Fn rad_create_request .
In addition to the usual
.Va struct rad_handle * ,
this function takes a
.Va code
parameter which specifies the type of the request.  Most often this
will be
.Dv RAD_ACCESS_REQUEST .
.Fn rad_create_request
returns 0 on success, or -1 on if an error occurs.
.Pp
After the request has been created with
.Fn rad_create_request ,
attributes can be attached to it.  This is done through calls to
.Fn rad_put_addr ,
.Fn rad_put_int ,
and
.Fn rad_put_string .
Each accepts a
.Va type
parameter identifying the attribute, and a value which may be
an Internet address, an integer, or a NUL-terminated string,
respectively.
.Pp
The library also provides a function
.Fn rad_put_attr
which can be used to supply a raw, uninterpreted attribute.  The
.Va data
argument points to an array of bytes, and the
.Va len
argument specifies its length.
.Pp
The
.Fn rad_put_X
functions return 0 on success, or -1 if an error occurs.
.Sh SENDING THE REQUEST AND RECEIVING THE RESPONSE
After the RADIUS request has been constructed, it is sent either by means of
.Fn rad_send_request
or by a combination of calls to
.Fn rad_init_send_request
and
.Fn rad_continue_send_request .
.Pp
The
.Fn rad_send_request
function sends the request and waits for a valid reply,
retrying the defined servers in round-robin fashion as necessary.
If a valid response is received,
.Fn rad_send_request
returns the RADIUS code which specifies the type of the response.
This will typically be
.Dv RAD_ACCESS_ACCEPT ,
.Dv RAD_ACCESS_REJECT ,
or
.Dv RAD_ACCESS_CHALLENGE .
If no valid response is received,
.Fn rad_send_request
returns -1.
.Pp
As an alternative, if you do not wish to block waiting for a response,
.Fn rad_init_send_request
and
.Fn rad_continue_send_request
may be used instead.  If a reply is received from the RADIUS server or a
timeout occurs, these functions return a value as described for
.Fn rad_send_request .
Otherwise, a value of zero is returned and the values pointed to by
.Ar fd
and
.Ar tv
are set to the descriptor and timeout that should be passed to
.Xr select 2 .
.Pp
.Fn rad_init_send_request
must be called first, followed by repeated calls to
.Fn rad_continue_send_request
as long as a return value of zero is given.
Between each call, the application should call
.Xr select 2 ,
passing
.Ar *fd
as a read descriptor and timing out after the interval specified by
.Ar tv .
When select returns,
.Fn rad_continue_send_request
should be called with
.Ar selected
set to a non-zero value if
.Xr select 2
indicated that the descriptor is readable.
.Pp
Like RADIUS requests, each response may contain zero or more
attributes.  After a response has been received successfully by
.Fn rad_send_request
or
.Fn rad_continue_send_request ,
its attributes can be extracted one by one using
.Fn rad_get_attr .
Each time
.Fn rad_get_attr
is called, it gets the next attribute from the current response, and
stores a pointer to the data and the length of the data via the
reference parameters
.Va data
and
.Va len ,
respectively.  Note that the data resides in the response itself,
and must not be modified.
A successful call to
.Fn rad_get_attr
returns the RADIUS attribute type.
If no more attributes remain in the current response,
.Fn rad_get_attr
returns 0.
If an error such as a malformed attribute is detected, -1 is
returned.
.Pp
The common types of attributes can be decoded using
.Fn rad_cvt_addr ,
.Fn rad_cvt_int ,
and
.Fn rad_cvt_string .
These functions accept a pointer to the attribute data, which should
have been obtained using
.Fn rad_get_attr .
In the case of
.Fn rad_cvt_string ,
the length
.Va len
must also be given.  These functions interpret the attribute as an
Internet address, an integer, or a string, respectively, and return
its value.
.Fn rad_cvt_string
returns its value as a NUL-terminated string in dynamically
allocated memory.  The application should free the string using
.Xr free 3
when it is no longer needed.
.Pp
If insufficient virtual memory is available,
.Fn rad_cvt_string
returns
.Dv NULL .
.Fn rad_cvt_addr
and
.Fn rad_cvt_int
cannot fail.
.Sh OBTAINING ERROR MESSAGES
Those functions which accept a
.Va struct rad_handle *
argument record an error message if they fail.  The error message
can be retrieved by calling
.Fn rad_strerror .
The message text is overwritten on each new error for the given
.Va struct rad_handle * .
Thus the message must be copied if it is to be preserved through
subsequent library calls using the same handle.
.Sh CLEANUP
To free the resources used by the RADIUS library, call
.Fn rad_close .
.Sh RETURN VALUES
The following functions return a non-negative value on success.  If
they detect an error, they return -1 and record an error message
which can be retrieved using
.Fn rad_strerror .
.Pp
.Bl -item -offset indent -compact
.It
.Fn rad_add_server
.It
.Fn rad_config
.It
.Fn rad_create_request
.It
.Fn rad_get_attr
.It
.Fn rad_put_addr
.It
.Fn rad_put_attr
.It
.Fn rad_put_int
.It
.Fn rad_put_string
.It
.Fn rad_init_send_request
.It
.Fn rad_continue_send_request
.It
.Fn rad_send_request
.El
.Pp
The following functions return a
.No non- Ns Dv NULL
pointer on success.  If they are unable to allocate sufficient
virtual memory, they return
.Dv NULL ,
without recording an error message.
.Pp
.Bl -item -offset indent -compact
.It
.Fn rad_cvt_string
.It
.Fn rad_open
.El
.Sh FILES
.Pa /etc/radius.conf
.Sh SEE ALSO
.Xr radius.conf 5
.Rs
.%A C. Rigney, et al
.%T Remote Authentication Dial In User Service (RADIUS)
.%O RFC 2138
.Re
.Sh AUTHORS
This software was written by
.An John Polstra ,
and donated to the FreeBSD project by Juniper Networks, Inc.