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30 .Dd October 30, 2007
31 .Os
32 .Dt GSS_ACCEPT_SEC_CONTEXT 3 PRM
33 .Sh NAME
34 .Nm gss_accept_sec_context
35 .Nd Accept a security context initiated by a peer application
36 .\" This next command is for sections 2 and 3 only.
37 .\" .Sh LIBRARY
38 .Sh SYNOPSIS
39 .In "gssapi/gssapi.h"
40 .Ft OM_uint32
41 .Fo gss_accept_sec_context
42 .Fa "OM_uint32 *minor_status
43 .Fa "gss_ctx_id_t *context_handle"
44 .Fa "const gss_cred_id_t acceptor_cred_handle"
45 .Fa "const gss_buffer_t input_token_buffer"
46 .Fa "const gss_channel_bindings_t input_chan_bindings"
47 .Fa "const gss_name_t *src_name"
48 .Fa "gss_OID *mech_type"
49 .Fa "gss_buffer_t output_token"
50 .Fa "OM_uint32 *ret_flags"
51 .Fa "OM_uint32 *time_rec"
52 .Fa "gss_cred_id_t *delegated_cred_handle"
53 .Fc
54 .Sh DESCRIPTION
55 Allows a remotely initiated security context between the application
56 and a remote peer to be established. The routine may return a
57 .Fa output_token
58 which should be transferred to the peer application,
59 where the peer application will present it to
60 .Xr gss_init_sec_context 3 .
61 If no token need be sent,
62 .Fn gss_accept_sec_context
63 will indicate this
64 by setting the length field of the
65 .Fa output_token
66 argument to zero.
67 To complete the context establishment, one or more reply tokens may be
68 required from the peer application; if so,
69 .Fn gss_accept_sec_context
70 will return a status flag of
71 .Dv GSS_S_CONTINUE_NEEDED , in which case it
72 should be called again when the reply token is received from the peer
73 application, passing the token to
74 .Fn gss_accept_sec_context
75 via the
76 .Fa input_token
77 parameters.
78 .Pp
79 Portable applications should be constructed to use the token length
80 and return status to determine whether a token needs to be sent or
81 waited for. Thus a typical portable caller should always invoke
82 .Fn gss_accept_sec_context
83 within a loop:
84 .Bd -literal
85 gss_ctx_id_t context_hdl = GSS_C_NO_CONTEXT;
87 do {
88 receive_token_from_peer(input_token);
89 maj_stat = gss_accept_sec_context(&min_stat,
90 &context_hdl,
91 cred_hdl,
92 input_token,
93 input_bindings,
94 &client_name,
95 &mech_type,
96 output_token,
97 &ret_flags,
98 &time_rec,
99 &deleg_cred);
100 if (GSS_ERROR(maj_stat)) {
101 report_error(maj_stat, min_stat);
102 };
103 if (output_token->length != 0) {
104 send_token_to_peer(output_token);
106 gss_release_buffer(&min_stat, output_token);
107 };
108 if (GSS_ERROR(maj_stat)) {
109 if (context_hdl != GSS_C_NO_CONTEXT)
110 gss_delete_sec_context(&min_stat,
111 &context_hdl,
112 GSS_C_NO_BUFFER);
113 break;
114 };
115 } while (maj_stat & GSS_S_CONTINUE_NEEDED);
116 .Ed
117 .Pp
118 Whenever the routine returns a major status that includes the value
119 .Dv GSS_S_CONTINUE_NEEDED , the context is not fully established and the
120 following restrictions apply to the output parameters:
121 .Pp
122 The value returned via the
123 .Fa time_rec
124 parameter is undefined Unless the
125 accompanying
126 .Fa ret_flags
127 parameter contains the bit
128 .Dv GSS_C_PROT_READY_FLAG , indicating that per-message services may be
129 applied in advance of a successful completion status, the value
130 returned via the
131 .Fa mech_type
132 parameter may be undefined until the
133 routine returns a major status value of
134 .Dv GSS_S_COMPLETE .
135 .Pp
136 The values of the
137 .Dv GSS_C_DELEG_FLAG ,
138 .Dv GSS_C_MUTUAL_FLAG ,
139 .Dv GSS_C_REPLAY_FLAG ,
140 .Dv GSS_C_SEQUENCE_FLAG ,
141 .Dv GSS_C_CONF_FLAG ,
142 .Dv GSS_C_INTEG_FLAG
143 and
144 .Dv GSS_C_ANON_FLAG bits returned
145 via the
146 .Fa ret_flags
147 parameter should contain the values that the
148 implementation expects would be valid if context establishment were
149 to succeed.
150 .Pp
151 The values of the
152 .Dv GSS_C_PROT_READY_FLAG
153 and
154 .Dv GSS_C_TRANS_FLAG bits
155 within
156 .Fa ret_flags
157 should indicate the actual state at the time
158 .Fn gss_accept_sec_context
159 returns, whether or not the context is fully established.
160 .Pp
161 Although this requires that GSS-API implementations set the
162 .Dv GSS_C_PROT_READY_FLAG
163 in the final
164 .Fa ret_flags
165 returned to a caller
166 (i.e. when accompanied by a
167 .Dv GSS_S_COMPLETE
168 status code), applications
169 should not rely on this behavior as the flag was not defined in
170 Version 1 of the GSS-API. Instead, applications should be prepared to
171 use per-message services after a successful context establishment,
172 according to the
173 .Dv GSS_C_INTEG_FLAG
174 and
175 .Dv GSS_C_CONF_FLAG values.
176 .Pp
177 All other bits within the
178 .Fa ret_flags
179 argument should be set to zero.
180 While the routine returns
181 .Dv GSS_S_CONTINUE_NEEDED , the values returned
182 via the
183 .Fa ret_flags
184 argument indicate the services that the
185 implementation expects to be available from the established context.
186 .Pp
187 If the initial call of
188 .Fn gss_accept_sec_context
189 fails, the
190 implementation should not create a context object, and should leave
191 the value of the context_handle parameter set to
192 .Dv GSS_C_NO_CONTEXT to
193 indicate this. In the event of a failure on a subsequent call, the
194 implementation is permitted to delete the "half-built" security
195 context (in which case it should set the
196 .Fa context_handle
197 parameter to
198 .Dv GSS_C_NO_CONTEXT ), but the preferred behavior is to leave the
199 security context (and the context_handle parameter) untouched for the
200 application to delete (using
201 .Xr gss_delete_sec_context 3 ).
202 .Pp
203 During context establishment, the informational status bits
204 .Dv GSS_S_OLD_TOKEN
205 and
206 .Dv GSS_S_DUPLICATE_TOKEN
207 indicate fatal errors, and
208 GSS-API mechanisms should always return them in association with a
209 routine error of
210 .Dv GSS_S_FAILURE . This requirement for pairing did not
211 exist in version 1 of the GSS-API specification, so applications that
212 wish to run over version 1 implementations must special-case these
213 codes.
214 .Sh PARAMETERS
215 .Bl -tag
216 .It context_handle
217 Context handle for new context.
218 Supply
219 .Dv GSS_C_NO_CONTEXT for first
220 call; use value returned in subsequent calls.
221 Once
222 .Fn gss_accept_sec_context
223 has returned a
224 value via this parameter, resources have been
225 assigned to the corresponding context, and must
226 be freed by the application after use with a
227 call to
228 .Xr gss_delete_sec_context 3 .
229 .It acceptor_cred_handle
230 Credential handle claimed by context acceptor.
231 Specify
232 .Dv GSS_C_NO_CREDENTIAL to accept the context as a
233 default principal.
234 If
235 .Dv GSS_C_NO_CREDENTIAL is
236 specified, but no default acceptor principal is
237 defined,
238 .Dv GSS_S_NO_CRED will be returned.
239 .It input_token_buffer
240 Token obtained from remote application.
241 .It input_chan_bindings
242 Application-specified bindings.
243 Allows application to securely bind channel identification information
244 to the security context.
245 If channel bindings are not used, specify
246 .Dv GSS_C_NO_CHANNEL_BINDINGS .
247 .It src_name
248 Authenticated name of context initiator.
249 After use, this name should be deallocated by passing it to
250 .Xr gss_release_name 3 .
251 If not required, specify
252 .Dv NULL .
253 .It mech_type
254 Security mechanism used.
255 The returned OID value will be a pointer into static storage,
256 and should be treated as read-only by the caller
257 (in particular, it does not need to be freed).
258 If not required, specify
259 .Dv NULL .
260 .It output_token
261 Token to be passed to peer application.
262 If the length field of the returned token buffer is 0,
263 then no token need be passed to the peer application.
264 If a non-zero length field is returned,
265 the associated storage must be freed after use by the
266 application with a call to
267 .Xr gss_release_buffer 3 .
268 .It ret_flags
269 Contains various independent flags,
270 each of which indicates that the context supports a specific service option.
271 If not needed, specify
272 .Dv NULL .
273 Symbolic names are provided for each flag,
274 and the symbolic names corresponding to the required flags should be
275 logically-ANDed with the
276 .Fa ret_flags
277 value to test whether a given option is supported by the context.
278 The flags are:
279 .Bl -tag -width "WW"
280 .It GSS_C_DELEG_FLAG
281 .Bl -tag -width "False"
282 .It True
283 Delegated credentials are available via the delegated_cred_handle parameter
284 .It False
285 No credentials were delegated
286 .El
287 .It GSS_C_MUTUAL_FLAG
288 .Bl -tag -width "False"
289 .It True
290 Remote peer asked for mutual authentication
291 .It False
292 Remote peer did not ask for mutual authentication
293 .El
294 .It GSS_C_REPLAY_FLAG
295 .Bl -tag -width "False"
296 .It True
297 Replay of protected messages will be detected
298 .It False
299 Replayed messages will not be detected
300 .El
301 .It GSS_C_SEQUENCE_FLAG
302 .Bl -tag -width "False"
303 .It True
304 Out-of-sequence protected messages will be detected
305 .It False
306 Out-of-sequence messages will not be detected
307 .El
308 .It GSS_C_CONF_FLAG
309 .Bl -tag -width "False"
310 .It True
311 Confidentiality service may be invoked by calling the
312 .Xr gss_wrap 3
313 routine
314 .It False
315 No confidentiality service (via
316 .Xr gss_wrap 3 )
317 available.
318 .Xr gss_wrap 3
319 will provide message encapsulation,
320 data-origin authentication and integrity services only.
321 .El
322 .It GSS_C_INTEG_FLAG
323 .Bl -tag -width "False"
324 .It True
325 Integrity service may be invoked by calling either
326 .Xr gss_get_mic 3
327 or
328 .Xr gss_wrap 3
329 routines.
330 .It False
331 Per-message integrity service unavailable.
332 .El
333 .It GSS_C_ANON_FLAG
334 .Bl -tag -width "False"
335 .It True
336 The initiator does not wish to be authenticated; the
337 .Fa src_name
338 parameter (if requested) contains an anonymous internal name.
339 .It False
340 The initiator has been authenticated normally.
341 .El
342 .It GSS_C_PROT_READY_FLAG
343 .Bl -tag -width "False"
344 .It True
345 Protection services (as specified by the states of the
346 .Dv GSS_C_CONF_FLAG
347 and
348 .Dv GSS_C_INTEG_FLAG )
349 are available if the accompanying major status return value is either
350 .Dv GSS_S_COMPLETE
351 or
352 .Dv GSS_S_CONTINUE_NEEDED.
353 .It False
354 Protection services (as specified by the states of the
355 .Dv GSS_C_CONF_FLAG
356 and
357 .Dv GSS_C_INTEG_FLAG )
358 are available only if the accompanying major status return value is
359 .Dv GSS_S_COMPLETE .
360 .El
361 .It GSS_C_TRANS_FLAG
362 .Bl -tag -width "False"
363 .It True
364 The resultant security context may be transferred to other processes
365 via a call to
366 .Xr gss_export_sec_context 3 .
367 .It False
368 The security context is not transferable.
369 .El
370 .El
371 .Pp
372 All other bits should be set to zero.
373 .It time_rec
374 Number of seconds for which the context will remain valid.
375 Specify
376 .Dv NULL
377 if not required.
378 .It delegated_cred_handle
379 Credential
380 handle for credentials received from context initiator.
381 Only valid if
382 .Dv GSS_C_DELEG_FLAG
383 in
384 .Fa ret_flags
385 is true,
386 in which case an explicit credential handle
387 (i.e. not
388 .Dv GSS_C_NO_CREDENTIAL )
389 will be returned; if false,
390 .Fn gss_accept_context
391 will set this parameter to
392 .Dv GSS_C_NO_CREDENTIAL .
393 If a credential handle is returned,
394 the associated resources must be released by the application after use
395 with a call to
396 .Xr gss_release_cred 3 .
397 Specify
398 .Dv NULL if not required.
399 .It minor_status
400 Mechanism specific status code.
401 .El
402 .Sh RETURN VALUES
403 .Bl -tag
404 .It GSS_S_CONTINUE_NEEDED
405 Indicates that a token from the peer application is required to
406 complete the context,
407 and that gss_accept_sec_context must be called again with that token.
408 .It GSS_S_DEFECTIVE_TOKEN
409 Indicates that consistency checks performed on the input_token failed.
410 .It GSS_S_DEFECTIVE_CREDENTIAL
411 Indicates that consistency checks performed on the credential failed.
412 .It GSS_S_NO_CRED
413 The supplied credentials were not valid for context acceptance,
414 or the credential handle did not reference any credentials.
415 .It GSS_S_CREDENTIALS_EXPIRED
416 The referenced credentials have expired.
417 .It GSS_S_BAD_BINDINGS
418 The input_token contains different channel bindings to those specified via the
419 input_chan_bindings parameter.
420 .It GSS_S_NO_CONTEXT
421 Indicates that the supplied context handle did not refer to a valid context.
422 .It GSS_S_BAD_SIG
423 The input_token contains an invalid MIC.
424 .It GSS_S_OLD_TOKEN
425 The input_token was too old.
426 This is a fatal error during context establishment.
427 .It GSS_S_DUPLICATE_TOKEN
428 The input_token is valid,
429 but is a duplicate of a token already processed.
430 This is a fatal error during context establishment.
431 .It GSS_S_BAD_MECH
432 The received token specified a mechanism that is not supported by
433 the implementation or the provided credential.
434 .El
435 .Sh SEE ALSO
436 .Xr gss_delete_sec_context 3 ,
437 .Xr gss_export_sec_context 3 ,
438 .Xr gss_get_mic 3 ,
439 .Xr gss_init_sec_context 3 ,
440 .Xr gss_release_buffer 3 ,
441 .Xr gss_release_cred 3 ,
442 .Xr gss_release_name 3 ,
443 .Xr gss_wrap 3
444 .Sh STANDARDS
445 .Bl -tag
446 .It RFC 2743
447 Generic Security Service Application Program Interface Version 2, Update 1
448 .It RFC 2744
449 Generic Security Service API Version 2 : C-bindings
450 .El
451 .Sh HISTORY
452 The
453 .Nm
454 manual page example first appeared in
455 .Fx 7.0 .
456 .Sh AUTHORS
457 John Wray, Iris Associates
458 .Sh COPYRIGHT
459 Copyright (C) The Internet Society (2000). All Rights Reserved.
460 .Pp
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466 included on all such copies and derivative works. However, this
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475 The limited permissions granted above are perpetual and will not be
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