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25 .\" $FreeBSD: src/lib/libtacplus/libtacplus.3,v 1.3.2.7 2002/10/09 08:50:42 pst Exp $
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28 .Dd September 2, 1998
29 .Dt LIBTACPLUS 3
30 .Os
31 .Sh NAME
32 .Nm libtacplus
33 .Nd TACACS+ client library
34 .Sh LIBRARY
35 .Lb libtacplus
36 .Sh SYNOPSIS
37 .In taclib.h
38 .Ft int
39 .Fn tac_add_server "struct tac_handle *h" "const char *host" "int port" "const char *secret" "int timeout" "int flags"
40 .Ft void
41 .Fn tac_clear_avs "struct tac_handle *h"
42 .Ft void
43 .Fn tac_close "struct tac_handle *h"
44 .Ft int
45 .Fn tac_config "struct tac_handle *h" "const char *path"
46 .Ft int
47 .Fn tac_create_authen "struct tac_handle *h" "int action" "int type" "int service"
48 .Ft int
49 .Fn tac_create_author "struct tac_handle *h" "int method" "int type" "int service"
50 .Ft char *
51 .Fn tac_get_av "struct tac_handle *h" "u_int index"
52 .Ft char *
53 .Fn tac_get_av_value "struct tac_handle *h" "const char *attribute"
54 .Ft void *
55 .Fn tac_get_data "struct tac_handle *h" "size_t *len"
56 .Ft char *
57 .Fn tac_get_msg "struct tac_handle *h"
58 .Ft struct tac_handle *
59 .Fn tac_open "void"
60 .Ft int
61 .Fn tac_send_authen "struct tac_handle *h"
62 .Ft int
63 .Fn tac_send_author "struct tac_handle *h"
64 .Ft int
65 .Fn tac_set_av "struct tac_handle *h" "u_int index" "const char *av_pair"
66 .Ft int
67 .Fn tac_set_data "struct tac_handle *h" "const void *data" "size_t data_len"
68 .Ft int
69 .Fn tac_set_msg "struct tac_handle *h" "const char *msg"
70 .Ft int
71 .Fn tac_set_port "struct tac_handle *h" "const char *port"
72 .Ft int
73 .Fn tac_set_priv "struct tac_handle *h" "int priv"
74 .Ft int
75 .Fn tac_set_rem_addr "struct tac_handle *h" "const char *addr"
76 .Ft int
77 .Fn tac_set_user "struct tac_handle *h" "const char *user"
78 .Ft const char *
79 .Fn tac_strerror "struct tac_handle *h"
80 .Sh DESCRIPTION
81 The
82 .Nm
83 library implements the client side of the TACACS+ network access
84 control protocol. TACACS+ allows clients to perform authentication,
85 authorization, and accounting by means of network requests to remote
86 servers. This library currently supports only the authentication
87 and authorization portion of the protocol.
88 .Sh INITIALIZATION
89 To use the library, an application must first call
90 .Fn tac_open
91 to obtain a
92 .Va struct tac_handle * ,
93 which provides context for subsequent operations.
94 Calls to
95 .Fn tac_open
96 always succeed unless insufficient virtual memory is available. If
97 the necessary memory cannot be allocated,
98 .Fn tac_open
99 returns
100 .Dv NULL .
101 .Pp
102 Before issuing any TACACS+ requests, the library must be made aware
103 of the servers it can contact. The easiest way to configure the
104 library is to call
105 .Fn tac_config .
106 .Fn tac_config
107 causes the library to read a configuration file whose format is
108 described in
109 .Xr tacplus.conf 5 .
110 The pathname of the configuration file is passed as the
111 .Va file
112 argument to
113 .Fn tac_config .
114 This argument may also be given as
115 .Dv NULL ,
116 in which case the standard configuration file
117 .Pa /etc/tacplus.conf
118 is used.
119 .Fn tac_config
120 returns 0 on success, or -1 if an error occurs.
121 .Pp
122 The library can also be configured programmatically by calls to
123 .Fn tac_add_server .
124 The
125 .Va host
126 parameter specifies the server host, either as a fully qualified
127 domain name or as a dotted-quad IP address in text form.
128 The
129 .Va port
130 parameter specifies the TCP port to contact on the server. If
131 .Va port
132 is given as 0, the library uses port 49, the standard TACACS+ port.
133 The shared secret for the server host is passed to the
134 .Va secret
135 parameter. It may be any null-terminated string of bytes.
136 The timeout for receiving replies from the server is passed to the
137 .Va timeout
138 parameter, in units of seconds.
139 The
140 .Va flags
141 parameter is a bit mask of flags to specify various characteristics of
142 the server. It may contain:
143 .Bl -tag -width Fl
144 .It Dv TAC_SRVR_SINGLE_CONNECT
145 Causes the library to attempt to negotiate single connection mode
146 when communicating with the server. In single connection mode, the
147 original TCP connection is held open for multiple TACACS+ sessions.
148 Older servers do not support this mode, and some of them become
149 confused if the client attempts to negotiate it.
150 .El
151 .Pp
152 .Fn tac_add_server
153 returns 0 on success, or -1 if an error occurs.
154 .Pp
155 .Fn tac_add_server
156 may be called multiple times, and it may be used together with
157 .Fn tac_config .
158 At most 10 servers may be specified.
159 When multiple servers are given, they are tried in round-robin
160 fashion until a working, accessible server is found. Once the
161 library finds such a server, it continues to use it as long as it
162 works.
163 .Sh CREATING A TACACS+ AUTHENTICATION REQUEST
164 To begin constructing a new authentication request, call
165 .Fn tac_create_authen .
166 The
167 .Va action ,
168 .Va type ,
169 and
170 .Va service
171 arguments must be set to appropriate values as defined in the
172 TACACS+ protocol specification. The
173 .In taclib.h
174 header file contains symbolic constants for these values.
175 .Sh CREATING A TACACS+ AUTHORIZATION REQUEST
176 To begin constructing a new authorization request, call
177 .Fn tac_create_author .
178 The
179 .Va method ,
180 .Va type ,
181 and
182 .Va service
183 arguments must be set to appropriate values as defined in the
184 TACACS+ protocol specification. The
185 .In taclib.h
186 header file contains symbolic constants for these values.
187 .Sh SETTING OPTIONAL PARAMETERS ON A REQUEST
188 After creating a request,
189 various optional parameters may be attached to it through calls to
190 .Fn tac_set_av ,
191 .Fn tac_set_data ,
192 .Fn tac_set_port ,
193 .Fn tac_set_priv ,
194 .Fn tac_set_rem_addr ,
195 and
196 .Fn tac_set_user .
197 The library creates its own copies of any strings provided to these
198 functions, so that it is not necessary for the caller to preserve
199 them. By default, each of these parameters is empty except for the
200 privilege level, which defaults to
201 .Ql USER
202 privilege.
203 .Pp
204 .Fn tac_set_av
205 only applies to the context of an authorization request. The format
206 for an attribute value pair is defined in the TACACS+ protocol
207 specification. The index specified can be any value between 0 and
208 255 inclusive and indicates the position in the list to place the
209 attribute value pair. Calling
210 .Fn tac_set_av
211 with same index twice effectively replaces the value at that position.
212 Use
213 .Fn tac_clear_avs
214 to clear all attribute value pairs that may have been set.
215 .Sh SENDING THE AUTHENTICATION REQUEST AND RECEIVING THE RESPONSE
216 After the TACACS+ authentication request has been constructed, it is
217 sent by means of
218 .Fn tac_send_authen .
219 This function connects to a server if not already connected, sends
220 the request, and waits for a reply. On failure,
221 .Fn tac_send_authen
222 returns -1. Otherwise, it returns the TACACS+ status code and flags,
223 packed into an integer value. The status can be extracted using the
224 macro
225 .Fn TAC_AUTHEN_STATUS .
226 Possible status codes, defined in
227 .In taclib.h ,
228 include:
229 .Pp
230 .Bl -item -compact -offset indent
231 .It
232 .Dv TAC_AUTHEN_STATUS_PASS
233 .It
234 .Dv TAC_AUTHEN_STATUS_FAIL
235 .It
236 .Dv TAC_AUTHEN_STATUS_GETDATA
237 .It
238 .Dv TAC_AUTHEN_STATUS_GETUSER
239 .It
240 .Dv TAC_AUTHEN_STATUS_GETPASS
241 .It
242 .Dv TAC_AUTHEN_STATUS_RESTART
243 .It
244 .Dv TAC_AUTHEN_STATUS_ERROR
245 .It
246 .Dv TAC_AUTHEN_STATUS_FOLLOW
247 .El
248 .Pp
249 The only flag is the no-echo flag, which can be tested using the
250 macro
251 .Fn TAC_AUTHEN_NOECHO .
252 .Sh EXTRACTING INFORMATION FROM THE SERVER'S AUTHENTICATION RESPONSE
253 An authentication response packet from the server may contain a
254 server message, a data string, or both. After a successful call to
255 .Fn tac_send_authen ,
256 this information may be retrieved from the response by calling
257 .Fn tac_get_msg
258 and
259 .Fn tac_get_data .
260 These functions return dynamically-allocated copies of the
261 information from the packet. The caller is responsible for freeing
262 the copies when it no longer needs them. The data returned from
263 these functions is guaranteed to be terminated by a null byte.
264 .Pp
265 In the case of
266 .Fn tac_get_data ,
267 the
268 .Va len
269 argument points to a location into which the library will store the
270 actual length of the received data, not including the null
271 terminator. This argument may be given as
272 .Dv NULL
273 if the caller is not interested in the length.
274 .Sh SENDING AUTHENTICATION CONTINUE PACKETS
275 If
276 .Fn tac_send_authen
277 returns a value containing one of the status codes
278 .Dv TAC_AUTHEN_STATUS_GETDATA ,
279 .Dv TAC_AUTHEN_STATUS_GETUSER ,
280 or
281 .Dv TAC_AUTHEN_STATUS_GETPASS ,
282 then the client must provide additional information to the server by
283 means of a TACACS+ CONTINUE packet. To do so, the application must
284 first set the packet's user message and/or data fields using
285 .Fn tac_set_msg
286 and
287 .Fn tac_set_data .
288 The client then sends the CONTINUE packet with
289 .Fn tac_send_authen .
290 N.B.,
291 .Fn tac_create_authen
292 should
293 .Em not
294 be called to construct a CONTINUE packet; it is used only for the
295 initial authentication request.
296 .Pp
297 When it receives the CONTINUE packet, the server may again request
298 more information by returning
299 .Dv TAC_AUTHEN_STATUS_GETDATA ,
300 .Dv TAC_AUTHEN_STATUS_GETUSER ,
301 or
302 .Dv TAC_AUTHEN_STATUS_GETPASS .
303 The application should send further CONTINUEs until some other
304 status is received from the server.
305 .Sh SENDING THE AUTHORIZATION REQUEST AND RECEIVING THE RESPONSE
306 After the TACACS+ authorization request has been constructed, it
307 is sent by means of
308 .Fn tac_send_author .
309 This function connects to a server if not already connected, sends
310 the request, and waits for a reply. On failure,
311 .Fn tac_send_author
312 returns -1. Otherwise, it returns the TACACS+ status code and
313 number of attribute value (AV) pairs received packed into an
314 integer value. The status can be extracted using the macro
315 .Fn TAC_AUTHOR_STATUS .
316 Possible status codes, defined in
317 .In taclib.h ,
318 include:
319 .Pp
320 .Bl -item -compact -offset indent
321 .It
322 .Dv TAC_AUTHOR_STATUS_PASS_ADD
323 .It
324 .Dv TAC_AUTHOR_STATUS_PASS_REPL
325 .It
326 .Dv TAC_AUTHOR_STATUS_FAIL
327 .It
328 .Dv TAC_AUTHOR_STATUS_ERROR
329 .El
330 .Pp
331 The number of AV pairs received is obtained using
332 .Fn TAC_AUTHEN_AV_COUNT .
333 .Sh EXTRACTING INFORMATION FROM THE SERVER'S AUTHORIZATION RESPONSE
334 Like an authentication response packet, an authorization
335 response packet from the
336 server may contain a server message, a data string, or both. Refer
337 to EXTRACTING INFORMATION FROM THE SERVER'S AUTHENTICATION RESPONSE
338 for instruction on extraction of those values.
339 .Pp
340 An authorization response packet from the server may also contain
341 attribute value (AV) pairs. To extract these, use
342 .Fn tac_get_av
343 or
344 .Fn tac_get_av_value .
345 .Fn tac_get_av
346 takes the index of the AV pair as it is positioned in the list.
347 The indexes start at 0 (use
348 .Fn TAC_AUTHEN_AV_COUNT
349 on the return value of
350 .Fn tac_send_author
351 to get the total number of items in this list).
352 Alternatively,
353 .Fn tac_get_av_value
354 can be used.
355 .Fn tac_get_av_value
356 takes the attribute name and returns the
357 corresponding value only, not the AV pair. These functions return
358 dynamically-allocated copies of the information from the packet.
359 The caller is responsible for freeing the copies when it no longer
360 needs them. The data returned from these functions is guaranteed
361 to be terminated by a null byte.
362 .Sh OBTAINING ERROR MESSAGES
363 Those functions which accept a
364 .Va struct tac_handle *
365 argument record an error message if they fail. The error message
366 can be retrieved by calling
367 .Fn tac_strerror .
368 The message text is overwritten on each new error for the given
369 .Va struct tac_handle * .
370 Thus the message must be copied if it is to be preserved through
371 subsequent library calls using the same handle.
372 .Sh CLEANUP
373 To free the resources used by the TACACS+ library, call
374 .Fn tac_close .
375 .Sh RETURN VALUES
376 The following functions return a non-negative value on success. If
377 they detect an error, they return -1 and record an error message
378 which can be retrieved using
379 .Fn tac_strerror .
380 .Pp
381 .Bl -item -offset indent -compact
382 .It
383 .Fn tac_add_server
384 .It
385 .Fn tac_config
386 .It
387 .Fn tac_create_authen
388 .It
389 .Fn tac_create_author
390 .It
391 .Fn tac_send_authen
392 .It
393 .Fn tac_send_author
394 .It
395 .Fn tac_set_av
396 .It
397 .Fn tac_set_data
398 .It
399 .Fn tac_set_msg
400 .It
401 .Fn tac_set_port
402 .It
403 .Fn tac_set_priv
404 .It
405 .Fn tac_set_rem_addr
406 .It
407 .Fn tac_set_user
408 .El
409 .Pp
410 The following functions return a
411 .No non- Ns Dv NULL
412 pointer on success. If they are unable to allocate sufficient
413 virtual memory, they return
414 .Dv NULL
415 and record an error message which can be retrieved using
416 .Fn tac_strerror .
417 .Pp
418 .Bl -item -offset indent -compact
419 .It
420 .Fn tac_get_av
421 .It
422 .Fn tac_get_av_value
423 .It
424 .Fn tac_get_data
425 .It
426 .Fn tac_get_msg
427 .El
428 .Pp
429 The following functions return a
430 .No non- Ns Dv NULL
431 pointer on success. If they are unable to allocate sufficient
432 virtual memory, they return
433 .Dv NULL ,
434 without recording an error message.
435 .Pp
436 .Bl -item -offset indent -compact
437 .It
438 .Fn tac_open
439 .El
440 .Sh FILES
441 .Pa /etc/tacplus.conf
442 .Sh SEE ALSO
443 .Xr tacplus.conf 5
444 .Rs
445 .%A D. Carrel
446 .%A Lol Grant
447 .%T The TACACS+ Protocol, Version 1.78
448 .%O draft-grant-tacacs-02.txt (Internet Draft)
449 .Re
450 .Sh AUTHORS
451 .An -nosplit
452 This software was written by
453 .An John Polstra ,
454 and
455 .An Paul Fraley ,
456 and donated to the
457 .Fx
458 project by Juniper Networks, Inc.