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LIBRADIUS(3) DragonFly Library Functions Manual LIBRADIUS(3)
libradius -- RADIUS client/server library
RADIUS Client and Server Library (libradius, -lradius)
struct rad_handle *
rad_add_server(struct rad_handle *h, const char *host, int port,
const char *secret, int timeout, int max_tries);
struct rad_handle *
rad_close(struct rad_handle *h);
rad_config(struct rad_handle *h, const char *file);
rad_continue_send_request(struct rad_handle *h, int selected, int *fd,
struct timeval *tv);
rad_create_request(struct rad_handle *h, int code);
rad_create_response(struct rad_handle *h, int code);
rad_cvt_addr(const void *data);
rad_cvt_int(const void *data);
rad_cvt_string(const void *data, size_t len);
rad_get_attr(struct rad_handle *h, const void **data, size_t *len);
rad_get_vendor_attr(u_int32_t *vendor, const void **data, size_t *len);
rad_init_send_request(struct rad_handle *h, int *fd, struct timeval *tv);
rad_put_addr(struct rad_handle *h, int type, struct in_addr addr);
rad_put_attr(struct rad_handle *h, int type, const void *data,
rad_put_int(struct rad_handle *h, int type, u_int32_t value);
rad_put_string(struct rad_handle *h, int type, const char *str);
rad_put_message_authentic(struct rad_handle *h);
rad_put_vendor_addr(struct rad_handle *h, int vendor, int type,
struct in_addr addr);
rad_put_vendor_attr(struct rad_handle *h, int vendor, int type,
const void *data, size_t len);
rad_put_vendor_int(struct rad_handle *h, int vendor, int type,
rad_put_vendor_string(struct rad_handle *h, int vendor, int type,
const char *str);
rad_request_authenticator(struct rad_handle *h, char *buf, size_t len);
rad_receive_request(struct rad_handle *h);
rad_send_request(struct rad_handle *h);
rad_send_response(struct rad_handle *h);
struct rad_handle *
const char *
rad_server_secret(struct rad_handle *h);
rad_demangle(struct rad_handle *h, const void *mangled, size_t mlen);
rad_demangle_mppe_key(struct rad_handle *h, const void *mangled,
size_t mlen, size_t *len);
const char *
rad_strerror(struct rad_handle *h);
The libradius library implements the Remote Authentication Dial In User
Service (RADIUS). RADIUS, defined in RFCs 2865 and 2866, allows clients
to perform authentication and accounting by means of network requests to
To use the library, an application must first call rad_auth_open() ,
rad_acct_open() or rad_server_open() to obtain a struct rad_handle *,
which provides the context for subsequent operations. The former func-
tion is used for RADIUS authentication and the latter is used for RADIUS
accounting. Calls to rad_auth_open() , rad_acct_open() and
rad_server_open() always succeed unless insufficient virtual memory is
available. If the necessary memory cannot be allocated, the functions
return NULL. For compatibility with earlier versions of this library,
rad_open() is provided as a synonym for rad_auth_open().
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 rad_config(). rad_config() causes the library to read a configura-
tion file whose format is described in radius.conf(5). The pathname of
the configuration file is passed as the file argument to rad_config().
This argument may also be given as NULL, in which case the standard con-
figuration file /etc/radius.conf is used. rad_config() returns 0 on suc-
cess, or -1 if an error occurs.
The library can also be configured programmatically by calls to
rad_add_server(). The host parameter specifies the server host, either
as a fully qualified domain name or as a dotted-quad IP address in text
form. The port parameter specifies the UDP port to contact on the
server. If port is given as 0, the library looks up the `radius/udp' or
`radacct/udp' service in the network services(5) database, and uses the
port found there. If no entry is found, the library uses the standard
RADIUS ports, 1812 for authentication and 1813 for accounting. The
shared secret for the server host is passed to the 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 timeout parameter, in
units of seconds. The maximum number of repeated requests to make before
giving up is passed into the max_tries parameter. rad_add_server()
returns 0 on success, or -1 if an error occurs.
rad_add_server() may be called multiple times, and it may be used
together with 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 max_tries limit has
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 rad_create_request(). In addition to
the usual struct rad_handle *, this function takes a code parameter which
specifies the type of the request. Most often this will be
RAD_ACCESS_REQUEST. rad_create_request() returns 0 on success, or -1 on
if an error occurs.
After the request has been created with rad_create_request(), attributes
can be attached to it. This is done through calls to rad_put_addr(),
rad_put_int(), and rad_put_string(). Each accepts a type parameter iden-
tifying the attribute, and a value which may be an Internet address, an
integer, or a NUL-terminated string, respectively. Alternatively,
rad_put_vendor_addr(), rad_put_vendor_int() or rad_put_vendor_string()
may be used to specify vendor specific attributes. Vendor specific defi-
nitions may be found in <radlib_vs.h>
The library also provides a function rad_put_attr() which can be used to
supply a raw, uninterpreted attribute. The data argument points to an
array of bytes, and the len argument specifies its length.
It is possible adding the Message-Authenticator to the request. This is
an HMAC-MD5 hash of the entire Access-Request packet (see RFC 3579).
This attribute must be present in any packet that includes an EAP-Message
attribute. It can be added by using the rad_put_message_authentic()
function. The libradius library calculates the HMAC-MD5 hash implicitly
before sending the request. If the Message-Authenticator was found
inside the response packet, then the packet is silently dropped, if the
validation failed. In order to get this feature, the library should be
compiled with OpenSSL support.
The rad_put_X() functions return 0 on success, or -1 if an error occurs.
Sending the Request and Receiving the Response
After the RADIUS request has been constructed, it is sent either by means
of rad_send_request() or by a combination of calls to
rad_init_send_request() and rad_continue_send_request().
The 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, rad_send_request() returns the RADIUS
code which specifies the type of the response. This will typically be
RAD_ACCESS_ACCEPT, RAD_ACCESS_REJECT, or RAD_ACCESS_CHALLENGE. If no
valid response is received, rad_send_request() returns -1.
As an alternative, if you do not wish to block waiting for a response,
rad_init_send_request() and 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
rad_send_request(). Otherwise, a value of zero is returned and the val-
ues pointed to by fd and tv are set to the descriptor and timeout that
should be passed to select(2).
rad_init_send_request() must be called first, followed by repeated calls
to rad_continue_send_request() as long as a return value of zero is
given. Between each call, the application should call select(2), passing
*fd as a read descriptor and timing out after the interval specified by
tv. When select(2) returns, rad_continue_send_request() should be called
with selected set to a non-zero value if select(2) indicated that the
descriptor is readable.
Like RADIUS requests, each response may contain zero or more attributes.
After a response has been received successfully by rad_send_request() or
rad_continue_send_request(), its attributes can be extracted one by one
using rad_get_attr(). Each time 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 data and
len, respectively. Note that the data resides in the response itself,
and must not be modified. A successful call to rad_get_attr() returns
the RADIUS attribute type. If no more attributes remain in the current
response, rad_get_attr() returns 0. If an error such as a malformed
attribute is detected, -1 is returned.
If rad_get_attr() returns RAD_VENDOR_SPECIFIC, rad_get_vendor_attr() may
be called to determine the vendor. The vendor specific RADIUS attribute
type is returned. The reference parameters data and len (as returned
from rad_get_attr()) are passed to rad_get_vendor_attr(), and are
adjusted to point to the vendor specific attribute data.
The common types of attributes can be decoded using rad_cvt_addr(),
rad_cvt_int(), and rad_cvt_string(). These functions accept a pointer to
the attribute data, which should have been obtained using rad_get_attr()
and optionally rad_get_vendor_attr(). In the case of rad_cvt_string(),
the length len must also be given. These functions interpret the
attribute as an Internet address, an integer, or a string, respectively,
and return its value. rad_cvt_string() returns its value as a
NUL-terminated string in dynamically allocated memory. The application
should free the string using free(3) when it is no longer needed.
If insufficient virtual memory is available, rad_cvt_string() returns
NULL. rad_cvt_addr() and rad_cvt_int() cannot fail.
The rad_request_authenticator() function may be used to obtain the
Request-Authenticator attribute value associated with the current RADIUS
server according to the supplied rad_handle. The target buffer buf of
length len must be supplied and should be at least 16 bytes. The return
value is the number of bytes written to buf or -1 to indicate that len
was not large enough.
The rad_server_secret() returns the secret shared with the current RADIUS
server according to the supplied rad_handle.
The rad_demangle() function demangles attributes containing passwords and
MS-CHAPv1 MPPE-Keys. The return value is NULL on failure, or the plain-
text attribute. This value should be freed using free(3) when it is no
The rad_demangle_mppe_key() function demangles the send- and recv-keys
when using MPPE (see RFC 2548). The return value is NULL on failure, or
the plaintext attribute. This value should be freed using free(3) when
it is no longer needed.
Obtaining Error Messages
Those functions which accept a struct rad_handle * argument record an
error message if they fail. The error message can be retrieved by call-
ing rad_strerror(). The message text is overwritten on each new error
for the given struct rad_handle *. Thus the message must be copied if it
is to be preserved through subsequent library calls using the same han-
To free the resources used by the RADIUS library, call rad_close().
Server mode operates much alike to client mode, except packet send and
receive steps are swapped. To operate as server you should obtain server
context with rad_server_open() function, passing opened and bound UDP
socket file descriptor as argument. You should define allowed clients
and their secrets using rad_add_server() function. port, timeout and
max_tries arguments are ignored in server mode. You should call
rad_receive_request() function to receive request from client. If you do
not want to block on socket read, you are free to use any poll(),
select() or non-blocking sockets for the socket. Received request can be
parsed with same parsing functions as for client. To respond to the
request you should call rad_create_response() and fill response content
with same packet writing functions as for client. When packet is ready,
it should be sent with rad_send_response()
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 rad_strerror().
The following functions return a non-NULL pointer on success. If they
are unable to allocate sufficient virtual memory, they return NULL, with-
out recording an error message.
The following functions return a non-NULL pointer on success. If they
fail, they return NULL, with recording an error message.
C. Rigney, et al, Remote Authentication Dial In User Service (RADIUS),
C. Rigney, RADIUS Accounting, RFC 2866.
G. Zorn, Microsoft Vendor-specific RADIUS attributes, RFC 2548.
C. Rigney, et al, RADIUS extensions, RFC 2869.
This software was originally written by John Polstra, and donated to the
FreeBSD project by Juniper Networks, Inc. Oleg Semyonov subsequently
added the ability to perform RADIUS accounting. Later additions and
changes by Michael Bretterklieber. Server mode support was added by
DragonFly 4.9 September 24, 2010 DragonFly 4.9