LIBRADIUS(3) BSD Library Functions Manual LIBRADIUS(3)
libradius -- RADIUS client/server library
struct rad_handle *
rad_add_server(struct rad_handle *h, const char *host, int port, const char *secret, int timeout, int max_tries);
rad_add_server_ex(struct rad_handle *h, const char *host, int port, const char *secret, int timeout, int max_tries, int dead_time,
struct in_addr *bindto);
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(uint32_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, size_t len);
rad_put_int(struct rad_handle *h, int type, uint32_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, uint32_t value);
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_bind_to(struct rad_handle *h, in_addr_t addr);
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 remote servers.
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 function 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 configuration 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 configuration file /etc/radius.conf is used. rad_config() returns 0 on success, or -1 if an error occurs.
The library can also be configured programmatically by calls to rad_add_server() or rad_add_server_ex(). rad_add_server() is a backward com-
patible function, implemented via rad_add_server_ex(). 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 maxi-
mum number of repeated requests to make before giving up is passed into the max_tries parameter. Time interval in seconds when the server
will not be requested if it is marked as dead (did not answer on the last try) set with dead_time parameter. bindto parameter is an IP
address on the multihomed host that is used as a source address for all requests. rad_add_server() returns 0 on success, or -1 if an error
rad_add_server() or rad_add_server_ex() may be called multiple times, and they 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 been reached.
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 param-
eter 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 identifying 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 definitions 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 Mes-
sage-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 neces-
sary. If a valid response is received, rad_send_request() returns the RADIUS code which specifies the type of the response. This will typi-
cally 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 values 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 speci-
fied by tv. When select(2) returns, rad_continue_send_request() should be called with selected set to a non-zero value if select(2) indi-
cated 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 refer-
ence 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_bind_to() assigns a source address for all requests to the current RADIUS server.
The rad_demangle() function demangles attributes containing passwords and MS-CHAPv1 MPPE-Keys. 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.
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
calling 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 handle.
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,
without 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), RFC 2865.
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 subse-
quently added the ability to perform RADIUS accounting. Later additions and changes by Michael Bretterklieber. Server mode support was
added by Alexander Motin.
August 5, 2009 BSD