summaryrefslogtreecommitdiffstats
path: root/src/lib/gssapi/krb5/init_sec_context.c
blob: 13a971ffa61f22d26c877618505576a0bf995c03 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
/*
 * Copyright 2000 by the Massachusetts Institute of Technology.
 * All Rights Reserved.
 *
 * Export of this software from the United States of America may
 *   require a specific license from the United States Government.
 *   It is the responsibility of any person or organization contemplating
 *   export to obtain such a license before exporting.
 * 
 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
 * distribute this software and its documentation for any purpose and
 * without fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright notice and
 * this permission notice appear in supporting documentation, and that
 * the name of M.I.T. not be used in advertising or publicity pertaining
 * to distribution of the software without specific, written prior
 * permission.  Furthermore if you modify this software you must label
 * your software as modified software and not distribute it in such a
 * fashion that it might be confused with the original M.I.T. software.
 * M.I.T. makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is" without express
 * or implied warranty.
 * 
 */
/*
 * Copyright 1993 by OpenVision Technologies, Inc.
 * 
 * Permission to use, copy, modify, distribute, and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appears in all copies and
 * that both that copyright notice and this permission notice appear in
 * supporting documentation, and that the name of OpenVision not be used
 * in advertising or publicity pertaining to distribution of the software
 * without specific, written prior permission. OpenVision makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 * 
 * OPENVISION DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
 * EVENT SHALL OPENVISION BE LIABLE FOR ANY SPECIAL, INDIRECT OR
 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
 * USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
 * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

/*
 * Copyright (C) 1998 by the FundsXpress, INC.
 * 
 * All rights reserved.
 * 
 * Export of this software from the United States of America may require
 * a specific license from the United States Government.  It is the
 * responsibility of any person or organization contemplating export to
 * obtain such a license before exporting.
 * 
 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
 * distribute this software and its documentation for any purpose and
 * without fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright notice and
 * this permission notice appear in supporting documentation, and that
 * the name of FundsXpress. not be used in advertising or publicity pertaining
 * to distribution of the software without specific, written prior
 * permission.  FundsXpress makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is" without express
 * or implied warranty.
 * 
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#include "gssapiP_krb5.h"
#ifdef HAVE_MEMORY_H
#include <memory.h>
#endif
#include <stdlib.h>
#include <assert.h>

/* XXX This is for debugging only!!!  Should become a real bitfield
   at some point */
int krb5_gss_dbg_client_expcreds = 0;

/*
 * Common code which fetches the correct krb5 credentials from the
 * ccache.
 */
static krb5_error_code get_credentials(context, cred, server, now,
				       endtime, enctypes, out_creds)
    krb5_context context;
    krb5_gss_cred_id_t cred;
    krb5_principal server;
    krb5_timestamp now;
    krb5_timestamp endtime;
    const krb5_enctype *enctypes;
    krb5_creds **out_creds;
{
    krb5_error_code	code;
    krb5_creds 		in_creds;
    int i;
    
    memset((char *) &in_creds, 0, sizeof(krb5_creds));

    if ((code = krb5_copy_principal(context, cred->princ, &in_creds.client)))
	goto cleanup;
    if ((code = krb5_copy_principal(context, server, &in_creds.server)))
	goto cleanup;
    in_creds.times.endtime = endtime;

    in_creds.keyblock.enctype = 0;

    for (i = 0; enctypes[i]; i++) {
	in_creds.keyblock.enctype = enctypes[i];
	code = krb5_get_credentials(context, 0, cred->ccache, 
				    &in_creds, out_creds);
	if (code != KRB5_CC_NOT_KTYPE && code != KRB5KDC_ERR_ETYPE_NOSUPP)
	    break;
    }
    if (enctypes[i] == 0) {
	code = KRB5_CONFIG_ETYPE_NOSUPP;
	goto cleanup;
    }
    if (code)
	goto cleanup;

    /*
     * Enforce a stricter limit (without timeskew forgiveness at the
     * boundaries) because accept_sec_context code is also similarly
     * non-forgiving.
     */
    if (!krb5_gss_dbg_client_expcreds && *out_creds != NULL &&
	(*out_creds)->times.endtime < now) {
	code = KRB5KRB_AP_ERR_TKT_EXPIRED;
	goto cleanup;
    }
    
cleanup:
    if (in_creds.client)
	    krb5_free_principal(context, in_creds.client);
    if (in_creds.server)
	    krb5_free_principal(context, in_creds.server);
    return code;
}


static krb5_error_code
make_ap_req_v2(context, ctx, cred, k_cred, chan_bindings, mech_type, token)
    krb5_context context;
    krb5_gss_ctx_id_rec *ctx;
    krb5_creds *k_cred;
    krb5_gss_cred_id_t cred;
    gss_channel_bindings_t chan_bindings;
    gss_OID mech_type;
    gss_buffer_t token;
{
    int krb5_mech2_supported = 0;
    assert(krb5_mech2_supported);
}

static krb5_error_code
make_ap_req_v1(context, ctx, cred, k_cred, chan_bindings, mech_type, token)
    krb5_context context;
    krb5_gss_ctx_id_rec *ctx;
    krb5_gss_cred_id_t cred;
    krb5_creds *k_cred;
    gss_channel_bindings_t chan_bindings;
    gss_OID mech_type;
    gss_buffer_t token;
{
    krb5_flags mk_req_flags = 0;
    krb5_error_code code;
    krb5_data checksum_data;
    krb5_checksum md5;
    krb5_data ap_req;
    unsigned char *ptr;
    krb5_data credmsg;
    unsigned char *t;
    int tlen;
    krb5_int32 con_flags;

    ap_req.data = 0;
    checksum_data.data = 0;
    credmsg.data = 0;

    /* build the checksum buffer */
 
    /* compute the hash of the channel bindings */

    if ((code = kg_checksum_channel_bindings(context, chan_bindings, &md5, 0)))
        return(code);

    krb5_auth_con_set_req_cksumtype(context, ctx->auth_context,
				    CKSUMTYPE_KG_CB);

    /* build the checksum field */

    if (ctx->gss_flags & GSS_C_DELEG_FLAG) {
	/* first get KRB_CRED message, so we know its length */

	/* clear the time check flag that was set in krb5_auth_con_init() */
	krb5_auth_con_getflags(context, ctx->auth_context, &con_flags);
	krb5_auth_con_setflags(context, ctx->auth_context,
			       con_flags & ~KRB5_AUTH_CONTEXT_DO_TIME);

	code = krb5_fwd_tgt_creds(context, ctx->auth_context, 0,
				  cred->princ, ctx->there, cred->ccache, 1,
				  &credmsg);

	/* turn KRB5_AUTH_CONTEXT_DO_TIME back on */
	krb5_auth_con_setflags(context, ctx->auth_context, con_flags);

	if (code) {
	    /* don't fail here; just don't accept/do the delegation
               request */
	    ctx->gss_flags &= ~GSS_C_DELEG_FLAG;

	    checksum_data.length = 24;
	} else {
	    if (credmsg.length+28 > KRB5_INT16_MAX) {
		krb5_free_data_contents(context, &credmsg);
		return(KRB5KRB_ERR_FIELD_TOOLONG);
	    }

	    checksum_data.length = 28+credmsg.length;
	}
    } else {
	checksum_data.length = 24;
    }

    /* now allocate a buffer to hold the checksum data and
       (maybe) KRB_CRED msg */

    if ((checksum_data.data =
	 (char *) xmalloc(checksum_data.length)) == NULL) {
	if (credmsg.data)
	    krb5_free_data_contents(context, &credmsg);
	return(ENOMEM);
    }

    ptr = checksum_data.data;

    TWRITE_INT(ptr, md5.length, 0);
    TWRITE_STR(ptr, (unsigned char *) md5.contents, md5.length);
    TWRITE_INT(ptr, ctx->gss_flags, 0);

    /* done with this, free it */
    xfree(md5.contents);

    if (credmsg.data) {
	TWRITE_INT16(ptr, KRB5_GSS_FOR_CREDS_OPTION, 0);
	TWRITE_INT16(ptr, credmsg.length, 0);
	TWRITE_STR(ptr, (unsigned char *) credmsg.data, credmsg.length);

	/* free credmsg data */
	krb5_free_data_contents(context, &credmsg);
    }

    /* call mk_req.  subkey and ap_req need to be used or destroyed */

    mk_req_flags = AP_OPTS_USE_SUBKEY;

    if (ctx->gss_flags & GSS_C_MUTUAL_FLAG)
	mk_req_flags |= AP_OPTS_MUTUAL_REQUIRED;

    if ((code = krb5_mk_req_extended(context, &ctx->auth_context, mk_req_flags,
				     &checksum_data, k_cred, &ap_req)))
	goto cleanup;

   /* store the interesting stuff from creds and authent */
   ctx->endtime = k_cred->times.endtime;
   ctx->krb_flags = k_cred->ticket_flags;

   /* build up the token */

   /* allocate space for the token */
   tlen = g_token_size((gss_OID) mech_type, ap_req.length);

   if ((t = (unsigned char *) xmalloc(tlen)) == NULL) {
      code = ENOMEM;
      goto cleanup;
   }

   /* fill in the buffer */

   ptr = t;

   g_make_token_header((gss_OID) mech_type, ap_req.length,
		       &ptr, KG_TOK_CTX_AP_REQ);

   TWRITE_STR(ptr, (unsigned char *) ap_req.data, ap_req.length);

   /* pass it back */

   token->length = tlen;
   token->value = (void *) t;

   code = 0;
    
cleanup:
   if (checksum_data.data)
       free(checksum_data.data);
   if (ap_req.data)
       xfree(ap_req.data);

   return (code);
}

OM_uint32
krb5_gss_init_sec_context(minor_status, claimant_cred_handle,
			  context_handle, target_name, mech_type,
			  req_flags, time_req, input_chan_bindings,
			  input_token, actual_mech_type, output_token,
			  ret_flags, time_rec)
    OM_uint32 *minor_status;
    gss_cred_id_t claimant_cred_handle;
    gss_ctx_id_t *context_handle;
    gss_name_t target_name;
    gss_OID mech_type;
    OM_uint32 req_flags;
    OM_uint32 time_req;
    gss_channel_bindings_t input_chan_bindings;
    gss_buffer_t input_token;
    gss_OID *actual_mech_type;
    gss_buffer_t output_token;
    OM_uint32 *ret_flags;
    OM_uint32 *time_rec;
{
   krb5_context context;
   krb5_gss_cred_id_t cred;
   krb5_creds *k_cred = 0;
   static const krb5_enctype wanted_enctypes[] = {
#if 1
     ENCTYPE_DES3_CBC_SHA1,
#endif
     ENCTYPE_DES_CBC_CRC,
     ENCTYPE_DES_CBC_MD5, ENCTYPE_DES_CBC_MD4,
     0
   };
   krb5_error_code code; 
   krb5_gss_ctx_id_rec *ctx, *ctx_free;
   krb5_timestamp now;
   gss_buffer_desc token;
   int i, j, err;
   int default_mech = 0;
   krb5_ui_4 resp_flags;
   OM_uint32 major_status;

   if (GSS_ERROR(kg_get_context(minor_status, &context)))
      return(GSS_S_FAILURE);

   /* set up return values so they can be "freed" successfully */

   major_status = GSS_S_FAILURE; /* Default major code */
   output_token->length = 0;
   output_token->value = NULL;
   if (actual_mech_type)
      *actual_mech_type = NULL;
   token.value = 0;
   ctx_free = 0;

   /* verify the credential, or use the default */
   /*SUPPRESS 29*/
   if (claimant_cred_handle == GSS_C_NO_CREDENTIAL) {
      OM_uint32 major;

      if ((major = kg_get_defcred(minor_status, &claimant_cred_handle)) &&
	  GSS_ERROR(major)) {
	 return(major);
      }
   } else {
      OM_uint32 major;
	   
      major = krb5_gss_validate_cred(minor_status, claimant_cred_handle);
      if (GSS_ERROR(major))
	  return(major);
   }

   cred = (krb5_gss_cred_id_t) claimant_cred_handle;

   /* verify the mech_type */

   err = 0;
   if (mech_type == GSS_C_NULL_OID) {
       default_mech = 1;
       if (cred->rfc_mech) {
	   mech_type = gss_mech_krb5;
       } else if (cred->prerfc_mech) {
	   mech_type = gss_mech_krb5_old;
       } else {
	   err = 1;
       }
   } else if (g_OID_equal(mech_type, gss_mech_krb5)) {
       if (!cred->rfc_mech)
	   err = 1;
   } else if (g_OID_equal(mech_type, gss_mech_krb5_old)) {
       if (!cred->prerfc_mech)
	   err = 1;
   } else {
       err = 1;
   }
   
   if (err) {
      *minor_status = 0;
      return(GSS_S_BAD_MECH);
   }

   /* verify that the target_name is valid and usable */

   if (! kg_validate_name(target_name)) {
      *minor_status = (OM_uint32) G_VALIDATE_FAILED;
      return(GSS_S_CALL_BAD_STRUCTURE|GSS_S_BAD_NAME);
   }

   /* is this a new connection or not? */

   /*SUPPRESS 29*/
   if (*context_handle == GSS_C_NO_CONTEXT) {
      /* make sure the cred is usable for init */

      if ((cred->usage != GSS_C_INITIATE) &&
	  (cred->usage != GSS_C_BOTH)) {
	 *minor_status = 0;
	 return(GSS_S_NO_CRED);
      }

      /* complain if the input token is non-null */

      if (input_token != GSS_C_NO_BUFFER && input_token->length != 0) {
	 *minor_status = 0;
	 return(GSS_S_DEFECTIVE_TOKEN);
      }

      /* create the ctx */

      if ((ctx = (krb5_gss_ctx_id_rec *) xmalloc(sizeof(krb5_gss_ctx_id_rec)))
	  == NULL) {
	 *minor_status = ENOMEM;
	 return(GSS_S_FAILURE);
      }

      /* fill in the ctx */
      memset(ctx, 0, sizeof(krb5_gss_ctx_id_rec));
      ctx_free = ctx;
      if ((code = krb5_auth_con_init(context, &ctx->auth_context)))
	  goto fail;
      ctx->initiate = 1;
      ctx->gss_flags = KG_IMPLFLAGS(req_flags);
      ctx->seed_init = 0;
      ctx->big_endian = 0;  /* all initiators do little-endian, as per spec */
      ctx->seqstate = 0;
      ctx->nctypes = 0;
      ctx->ctypes = 0;

      if ((code = krb5_timeofday(context, &now)))
	  goto fail;

      if (time_req == 0 || time_req == GSS_C_INDEFINITE) {
	 ctx->endtime = 0;
      } else {
	 ctx->endtime = now + time_req;
      }

      if ((code = krb5_copy_principal(context, cred->princ, &ctx->here)))
	  goto fail;
      
      if ((code = krb5_copy_principal(context, (krb5_principal) target_name,
				      &ctx->there)))
	  goto fail;

      if ((code = get_credentials(context, cred, ctx->there, now,
				  ctx->endtime, wanted_enctypes, &k_cred)))
	  goto fail;

      if (default_mech) {
	 mech_type = gss_mech_krb5;
      }

      if (generic_gss_copy_oid(minor_status, mech_type, &ctx->mech_used)
	  != GSS_S_COMPLETE) {
	  code = *minor_status;
	  goto fail;
      }
      /*
       * Now try to make it static if at all possible....
       */
      ctx->mech_used = krb5_gss_convert_static_mech_oid(ctx->mech_used);

      {
	  /* gsskrb5 v1 */
	  if ((code = make_ap_req_v1(context, ctx,
				     cred, k_cred, input_chan_bindings, 
				     mech_type, &token))) {
	      if ((code == KRB5_FCC_NOFILE) || (code == KRB5_CC_NOTFOUND) ||
		  (code == KG_EMPTY_CCACHE))
		  major_status = GSS_S_NO_CRED;
	      if (code == KRB5KRB_AP_ERR_TKT_EXPIRED)
		  major_status = GSS_S_CREDENTIALS_EXPIRED;
	      goto fail;
	  }

	  krb5_auth_con_getlocalseqnumber(context, ctx->auth_context,
					  &ctx->seq_send);
	  krb5_auth_con_getlocalsubkey(context, ctx->auth_context,
				       &ctx->subkey);

	  /* fill in the encryption descriptors */

	  switch(ctx->subkey->enctype) {
	  case ENCTYPE_DES_CBC_MD5:
	  case ENCTYPE_DES_CBC_MD4:
	  case ENCTYPE_DES_CBC_CRC:
	      ctx->subkey->enctype = ENCTYPE_DES_CBC_RAW;
	      ctx->signalg = SGN_ALG_DES_MAC_MD5;
	      ctx->cksum_size = 8;
	      ctx->sealalg = SEAL_ALG_DES;

	      /* The encryption key is the session key XOR
		 0xf0f0f0f0f0f0f0f0.  */
	      if ((code = krb5_copy_keyblock(context, ctx->subkey, &ctx->enc)))
		  goto fail;

	      for (i=0; i<ctx->enc->length; i++)
		  /*SUPPRESS 113*/
		  ctx->enc->contents[i] ^= 0xf0;

	      if ((code = krb5_copy_keyblock(context, ctx->subkey, &ctx->seq)))
		  goto fail;

	      break;

	  case ENCTYPE_DES3_CBC_SHA1:
	      ctx->subkey->enctype = ENCTYPE_DES3_CBC_RAW;
	      ctx->signalg = SGN_ALG_HMAC_SHA1_DES3_KD;
	      ctx->cksum_size = 20;
	      ctx->sealalg = SEAL_ALG_DES3KD;

	      code = krb5_copy_keyblock (context, ctx->subkey, &ctx->enc);
	      if (code)
		  goto fail;
	      code = krb5_copy_keyblock (context, ctx->subkey, &ctx->seq);
	      if (code) {
		  krb5_free_keyblock (context, ctx->enc);
		  goto fail;
	      }
	      break;
#if 0
	  case ENCTYPE_DES3_CBC_MD5:
	      enctype = ENCTYPE_DES3_CBC_RAW;
	      ctx->signalg = 3;
	      ctx->cksum_size = 16;
	      ctx->sealalg = 1;
	      break;
#endif
	  default:
	      *minor_status = KRB5_BAD_ENCTYPE;
	      return GSS_S_FAILURE;
	  }

      }

      if (k_cred) {
          krb5_free_creds(context, k_cred);
	  k_cred = 0;
      }
      
      /* at this point, the context is constructed and valid,
	 hence, releaseable */

      /* intern the context handle */

      if (! kg_save_ctx_id((gss_ctx_id_t) ctx)) {
	  code = G_VALIDATE_FAILED;
	  goto fail;
      }
      *context_handle = (gss_ctx_id_t) ctx;
      ctx_free = 0;

      /* compute time_rec */
      if (time_rec) {
	 if ((code = krb5_timeofday(context, &now)))
	     goto fail;
	 *time_rec = ctx->endtime - now;
      }

      /* set the other returns */
      *output_token = token;

      if (ret_flags)
	 *ret_flags = ctx->gss_flags;

      if (actual_mech_type)
	 *actual_mech_type = mech_type;

      /* return successfully */

      *minor_status = 0;
      if (ctx->gss_flags & GSS_C_MUTUAL_FLAG) {
	 ctx->established = 0;
	 return(GSS_S_CONTINUE_NEEDED);
      } else {
	 ctx->seq_recv = ctx->seq_send;
	 g_order_init(&(ctx->seqstate), ctx->seq_recv,
		      (ctx->gss_flags & GSS_C_REPLAY_FLAG) != 0, 
		      (ctx->gss_flags & GSS_C_SEQUENCE_FLAG) != 0);
	 ctx->established = 1;
	 /* fall through to GSS_S_COMPLETE */
      }
   } else {
      unsigned char *ptr;
      char *sptr;
      krb5_data ap_rep, mic;
      krb5_ap_rep_enc_part *ap_rep_data;
      krb5_error *krb_error;

      /* validate the context handle */
      /*SUPPRESS 29*/
      if (! kg_validate_ctx_id(*context_handle)) {
	 *minor_status = (OM_uint32) G_VALIDATE_FAILED;
	 return(GSS_S_NO_CONTEXT);
      }

      ctx = (gss_ctx_id_t) *context_handle;

      /* make sure the context is non-established, and that certain
	 arguments are unchanged */

      if ((ctx->established) ||
	  (((gss_cred_id_t) cred) != claimant_cred_handle) ||
	  ((ctx->gss_flags & GSS_C_MUTUAL_FLAG) == 0)) {
	  code = KG_CONTEXT_ESTABLISHED;
	  goto fail;
      }

      if (! krb5_principal_compare(context, ctx->there, 
				   (krb5_principal) target_name)) {
	 (void)krb5_gss_delete_sec_context(minor_status, 
					   context_handle, NULL);
	 code = 0;
	 major_status = GSS_S_BAD_NAME;
	 goto fail;
      }

      /* verify the token and leave the AP_REP message in ap_rep */

      if (input_token == GSS_C_NO_BUFFER) {
	 (void)krb5_gss_delete_sec_context(minor_status, 
					   context_handle, NULL);
	 code = 0;
	 major_status = GSS_S_DEFECTIVE_TOKEN;
	 goto fail;
      }

      ptr = (unsigned char *) input_token->value;

      if ((err = g_verify_token_header((gss_OID) ctx->mech_used,
				       &(ap_rep.length),
				       &ptr, KG_TOK_CTX_AP_REP,
				       input_token->length))) {
	  if (g_verify_token_header((gss_OID) ctx->mech_used,
				    &(ap_rep.length),
				    &ptr, KG_TOK_CTX_ERROR,
				    input_token->length) == 0) {

	      /* Handle a KRB_ERROR message from the server */

	      sptr = (char *) ptr;           /* PC compiler bug */
	      TREAD_STR(sptr, ap_rep.data, ap_rep.length);
		      
	      code = krb5_rd_error(context, &ap_rep, &krb_error);
	      if (code)
		  goto fail;
	      if (krb_error->error)
		  code = krb_error->error + ERROR_TABLE_BASE_krb5;
	      else
		  code = 0;
	      krb5_free_error(context, krb_error);
	      goto fail;
	  } else {
	      *minor_status = 0;
	      return(GSS_S_DEFECTIVE_TOKEN);
	  }
      }

      sptr = (char *) ptr;                      /* PC compiler bug */
      TREAD_STR(sptr, ap_rep.data, ap_rep.length);

      /* decode the ap_rep */
      if ((code = krb5_rd_rep(context, ctx->auth_context, &ap_rep,
			      &ap_rep_data))) {
	  /*
	   * XXX A hack for backwards compatiblity.
	   * To be removed in 1999 -- proven 
	   */
	  krb5_auth_con_setuseruserkey(context, ctx->auth_context,
				       ctx->subkey);
	  if ((krb5_rd_rep(context, ctx->auth_context, &ap_rep,
			   &ap_rep_data)))
	      goto fail;
      }

      /* store away the sequence number */
      ctx->seq_recv = ap_rep_data->seq_number;
      g_order_init(&(ctx->seqstate), ctx->seq_recv,
		   (ctx->gss_flags & GSS_C_REPLAY_FLAG) != 0,
		   (ctx->gss_flags & GSS_C_SEQUENCE_FLAG) !=0);

      /* free the ap_rep_data */
      krb5_free_ap_rep_enc_part(context, ap_rep_data);

      /* set established */
      ctx->established = 1;

      /* set returns */

      if (time_rec) {
	 if ((code = krb5_timeofday(context, &now)))
		 goto fail;
	 *time_rec = ctx->endtime - now;
      }

      if (ret_flags)
	 *ret_flags = ctx->gss_flags;

      if (actual_mech_type)
	 *actual_mech_type = mech_type;

      /* success */

      *minor_status = 0;
      /* fall through to GSS_S_COMPLETE */
   }

   return(GSS_S_COMPLETE);

fail:
   if (ctx_free) {
       if (ctx_free->auth_context)
	   krb5_auth_con_free(context, ctx_free->auth_context);
       if (ctx_free->here)
	   krb5_free_principal(context, ctx_free->here);
       if (ctx_free->there)
	   krb5_free_principal(context, ctx_free->there);
       if (ctx_free->subkey)
	   krb5_free_keyblock(context, ctx_free->subkey);
       if (ctx_free->ctypes)
	   krb5_free_cksumtypes(context, ctx_free->ctypes);
       xfree(ctx_free);
   } else
	(void)krb5_gss_delete_sec_context(minor_status, context_handle, NULL);

   *minor_status = code;
   return (major_status);
}