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25 .\" $FreeBSD: src/lib/libtacplus/libtacplus.3,v 1.3.2.7 2002/10/09 08:50:42 pst Exp $
32 .Nd TACACS+ client library
36 .Fn tac_add_server "struct tac_handle *h" "const char *host" "int port" "const char *secret" "int timeout" "int flags"
38 .Fn tac_clear_avs "struct tac_handle *h"
40 .Fn tac_close "struct tac_handle *h"
42 .Fn tac_config "struct tac_handle *h" "const char *path"
44 .Fn tac_create_authen "struct tac_handle *h" "int action" "int type" "int service"
46 .Fn tac_create_author "struct tac_handle *h" "int method" "int type" "int service"
48 .Fn tac_get_av "struct tac_handle *h" "u_int index"
50 .Fn tac_get_av_value "struct tac_handle *h" "const char *attribute"
52 .Fn tac_get_data "struct tac_handle *h" "size_t *len"
54 .Fn tac_get_msg "struct tac_handle *h"
55 .Ft struct tac_handle *
58 .Fn tac_send_authen "struct tac_handle *h"
60 .Fn tac_send_author "struct tac_handle *h"
62 .Fn tac_set_av "struct tac_handle *h" "u_int index" "const char *av_pair"
64 .Fn tac_set_data "struct tac_handle *h" "const void *data" "size_t data_len"
66 .Fn tac_set_msg "struct tac_handle *h" "const char *msg"
68 .Fn tac_set_port "struct tac_handle *h" "const char *port"
70 .Fn tac_set_priv "struct tac_handle *h" "int priv"
72 .Fn tac_set_rem_addr "struct tac_handle *h" "const char *addr"
74 .Fn tac_set_user "struct tac_handle *h" "const char *user"
76 .Fn tac_strerror "struct tac_handle *h"
80 library implements the client side of the TACACS+ network access
81 control protocol. TACACS+ allows clients to perform authentication,
82 authorization, and accounting by means of network requests to remote
83 servers. This library currently supports only the authentication
84 and authorization portion of the protocol.
86 To use the library, an application must first call
89 .Va struct tac_handle * ,
90 which provides context for subsequent operations.
93 always succeed unless insufficient virtual memory is available. If
94 the necessary memory cannot be allocated,
99 Before issuing any TACACS+ requests, the library must be made aware
100 of the servers it can contact. The easiest way to configure the
104 causes the library to read a configuration file whose format is
107 The pathname of the configuration file is passed as the
111 This argument may also be given as
113 in which case the standard configuration file
114 .Pa /etc/tacplus.conf
117 returns 0 on success, or -1 if an error occurs.
119 The library can also be configured programmatically by calls to
123 parameter specifies the server host, either as a fully qualified
124 domain name or as a dotted-quad IP address in text form.
127 parameter specifies the TCP port to contact on the server. If
129 is given as 0, the library uses port 49, the standard TACACS+ port.
130 The shared secret for the server host is passed to the
132 parameter. It may be any null-terminated string of bytes.
133 The timeout for receiving replies from the server is passed to the
135 parameter, in units of seconds.
138 parameter is a bit mask of flags to specify various characteristics of
139 the server. It may contain:
142 .It Dv TAC_SRVR_SINGLE_CONNECT
143 Causes the library to attempt to negotiate single connection mode
144 when communicating with the server. In single connection mode, the
145 original TCP connection is held open for multiple TACACS+ sessions.
146 Older servers do not support this mode, and some of them become
147 confused if the client attempts to negotiate it.
151 returns 0 on success, or -1 if an error occurs.
154 may be called multiple times, and it may be used together with
156 At most 10 servers may be specified.
157 When multiple servers are given, they are tried in round-robin
158 fashion until a working, accessible server is found. Once the
159 library finds such a server, it continues to use it as long as it
161 .Sh CREATING A TACACS+ AUTHENTICATION REQUEST
162 To begin constructing a new authentication request, call
163 .Fn tac_create_authen .
169 arguments must be set to appropriate values as defined in the
170 TACACS+ protocol specification. The
172 header file contains symbolic constants for these values.
173 .Sh CREATING A TACACS+ AUTHORIZATION REQUEST
174 To begin constructing a new authorization request, call
175 .Fn tac_create_author .
181 arguments must be set to appropriate values as defined in the
182 TACACS+ protocol specification. The
184 header file contains symbolic constants for these values.
185 .Sh SETTING OPTIONAL PARAMETERS ON A REQUEST
186 After creating a request,
187 various optional parameters may be attached to it through calls to
192 .Fn tac_set_rem_addr ,
195 The library creates its own copies of any strings provided to these
196 functions, so that it is not necessary for the caller to preserve
197 them. By default, each of these parameters is empty except for the
198 privilege level, which defaults to
203 only applies to the context of an authorization request. The format
204 for an attribute value pair is defined in the TACACS+ protocol
205 specification. The index specified can be any value between 0 and
206 255 inclusive and indicates the position in the list to place the
207 attribute value pair. Calling
209 with same index twice effectively replaces the value at that position.
212 to clear all attribute value pairs that may have been set.
213 .Sh SENDING THE AUTHENTICATION REQUEST AND RECEIVING THE RESPONSE
214 After the TACACS+ authentication request has been constructed, it is
216 .Fn tac_send_authen .
217 This function connects to a server if not already connected, sends
218 the request, and waits for a reply. On failure,
220 returns -1. Otherwise, it returns the TACACS+ status code and flags,
221 packed into an integer value. The status can be extracted using the
223 .Fn TAC_AUTHEN_STATUS .
224 Possible status codes, defined in
228 .Bl -item -compact -offset indent
230 .Dv TAC_AUTHEN_STATUS_PASS
232 .Dv TAC_AUTHEN_STATUS_FAIL
234 .Dv TAC_AUTHEN_STATUS_GETDATA
236 .Dv TAC_AUTHEN_STATUS_GETUSER
238 .Dv TAC_AUTHEN_STATUS_GETPASS
240 .Dv TAC_AUTHEN_STATUS_RESTART
242 .Dv TAC_AUTHEN_STATUS_ERROR
244 .Dv TAC_AUTHEN_STATUS_FOLLOW
247 The only flag is the no-echo flag, which can be tested using the
249 .Fn TAC_AUTHEN_NOECHO .
250 .Sh EXTRACTING INFORMATION FROM THE SERVER'S AUTHENTICATION RESPONSE
251 An authentication response packet from the server may contain a
252 server message, a data string, or both. After a successful call to
253 .Fn tac_send_authen ,
254 this information may be retrieved from the response by calling
258 These functions return dynamically-allocated copies of the
259 information from the packet. The caller is responsible for freeing
260 the copies when it no longer needs them. The data returned from
261 these functions is guaranteed to be terminated by a null byte.
267 argument points to a location into which the library will store the
268 actual length of the received data, not including the null
269 terminator. This argument may be given as
271 if the caller is not interested in the length.
272 .Sh SENDING AUTHENTICATION CONTINUE PACKETS
275 returns a value containing one of the status codes
276 .Dv TAC_AUTHEN_STATUS_GETDATA ,
277 .Dv TAC_AUTHEN_STATUS_GETUSER ,
279 .Dv TAC_AUTHEN_STATUS_GETPASS ,
280 then the client must provide additional information to the server by
281 means of a TACACS+ CONTINUE packet. To do so, the application must
282 first set the packet's user message and/or data fields using
286 The client then sends the CONTINUE packet with
287 .Fn tac_send_authen .
289 .Fn tac_create_authen
292 be called to construct a CONTINUE packet; it is used only for the
293 initial authentication request.
295 When it receives the CONTINUE packet, the server may again request
296 more information by returning
297 .Dv TAC_AUTHEN_STATUS_GETDATA ,
298 .Dv TAC_AUTHEN_STATUS_GETUSER ,
300 .Dv TAC_AUTHEN_STATUS_GETPASS .
301 The application should send further CONTINUEs until some other
302 status is received from the server.
303 .Sh SENDING THE AUTHORIZATION REQUEST AND RECEIVING THE RESPONSE
304 After the TACACS+ authorization request has been constructed, it
306 .Fn tac_send_author .
307 This function connects to a server if not already connected, sends
308 the request, and waits for a reply. On failure,
310 returns -1. Otherwise, it returns the TACACS+ status code and
311 number of attribute value (AV) pairs received packed into an
312 integer value. The status can be extracted using the macro
313 .Fn TAC_AUTHOR_STATUS .
314 Possible status codes, defined in
318 .Bl -item -compact -offset indent
320 .Dv TAC_AUTHOR_STATUS_PASS_ADD
322 .Dv TAC_AUTHOR_STATUS_PASS_REPL
324 .Dv TAC_AUTHOR_STATUS_FAIL
326 .Dv TAC_AUTHOR_STATUS_ERROR
329 The number of AV pairs received is obtained using
330 .Fn TAC_AUTHEN_AV_COUNT .
331 .Sh EXTRACTING INFORMATION FROM THE SERVER'S AUTHORIZATION RESPONSE
332 Like an authentication response packet, an authorization
333 response packet from the
334 server may contain a server message, a data string, or both. Refer
335 to EXTRACTING INFORMATION FROM THE SERVER'S AUTHENTICATION RESPONSE
336 for instruction on extraction of those values.
338 An authorization response packet from the server may also contain
339 attribute value (AV) pairs. To extract these, use
342 .Fn tac_get_av_value .
344 takes the index of the AV pair as it is positioned in the list.
345 The indexes start at 0 (use
346 .Fn TAC_AUTHEN_AV_COUNT
347 on the return value of
349 to get the total number of items in this list).
354 takes the attribute name and returns the
355 corresponding value only, not the AV pair. These functions return
356 dynamically-allocated copies of the information from the packet.
357 The caller is responsible for freeing the copies when it no longer
358 needs them. The data returned from these functions is guaranteed
359 to be terminated by a null byte.
360 .Sh OBTAINING ERROR MESSAGES
361 Those functions which accept a
362 .Va struct tac_handle *
363 argument record an error message if they fail. The error message
364 can be retrieved by calling
366 The message text is overwritten on each new error for the given
367 .Va struct tac_handle * .
368 Thus the message must be copied if it is to be preserved through
369 subsequent library calls using the same handle.
371 To free the resources used by the TACACS+ library, call
374 The following functions return a non-negative value on success. If
375 they detect an error, they return -1 and record an error message
376 which can be retrieved using
379 .Bl -item -offset indent -compact
385 .Fn tac_create_authen
387 .Fn tac_create_author
408 The following functions return a
410 pointer on success. If they are unable to allocate sufficient
411 virtual memory, they return
413 and record an error message which can be retrieved using
416 .Bl -item -offset indent -compact
427 The following functions return a
429 pointer on success. If they are unable to allocate sufficient
430 virtual memory, they return
432 without recording an error message.
434 .Bl -item -offset indent -compact
439 .Pa /etc/tacplus.conf
445 .%T The TACACS+ Protocol, Version 1.78
446 .%O draft-grant-tacacs-02.txt (Internet Draft)
449 This software was written by
455 project by Juniper Networks, Inc.