LIBRADIUS(3)

NAME
libradius - RADIUS client library

SYNOPSIS
#include <radlib.h>
struct rad_handle *
rad_acct_open(void);
int
rad_add_server(struct rad_handle *h, const char *host, int port, const char *secret, int timeout, int max_tries);
struct rad_handle *
rad_auth_open(void);
void
rad_close(struct rad_handle *h);
int
rad_config(struct rad_handle *h, const char *file);
int
rad_continue_send_request(struct rad_handle *h, int selected, int *fd, struct timeval *tv);
int
rad_create_request(struct rad_handle *h, int code);
struct in_addr
rad_cvt_addr(const void *data);
u_int32_t
rad_cvt_int(const void *data);
char *
rad_cvt_string(const void *data, size_t len);
int
rad_get_attr(struct rad_handle *h, const void **data, size_t *len);
int
rad_init_send_request(struct rad_handle *h, int *fd, struct timeval *tv);
int
rad_put_addr(struct rad_handle *h, int type, struct in_addr addr);
int
rad_put_attr(struct rad_handle *h, int type, const void *data, size_t len);
int
rad_put_int(struct rad_handle *h, int type, u_int32_t value);
int
rad_put_string(struct rad_handle *h, int type, const char *str);
int
rad_send_request(struct rad_handle *h);
const char *
rad_strerror(struct rad_handle *h);

DESCRIPTION
The libradius library implements the client side of the Remote Authentication Dial In User Service (RADIUS). RADIUS, defined in RFCs 2138 and 2139, allows clients to perform authentication and accounting by means of network requests to remote servers.

INITIALIZATION
To use the library, an application must first call rad_auth_open() or rad_acct_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() and rad_acct_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(). 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 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 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 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 identifying the attribute, and a value which may be an Internet address, an integer, or a NUL-terminated string, respectively.

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.

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 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 specified by tv. When select 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.

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(). 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.

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.

CLEANUP
To free the resources used by the RADIUS library, call rad_close().

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 rad_strerror().

rad_add_server()
rad_config()
rad_create_request()
rad_get_attr()
rad_put_addr()
rad_put_attr()
rad_put_int()
rad_put_string()
rad_init_send_request()
rad_continue_send_request()
rad_send_request()

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.

rad_acct_open()
rad_auth_open()
rad_cvt_string()

FILES
/etc/radius.conf

SEE ALSO
radius.conf(5) C. Rigney, et al, Remote Authentication Dial In User Service (RADIUS), RFC 2138. C. Rigney, RADIUS Accounting, RFC 2139.

AUTHORS
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.