File: dh.c

package info (click to toggle)
libssh 0.4.5-3+squeeze3
  • links: PTS, VCS
  • area: main
  • in suites: squeeze-lts
  • size: 2,016 kB
  • ctags: 2,390
  • sloc: ansic: 22,011; sh: 22; makefile: 20; python: 9
file content (1049 lines) | stat: -rw-r--r-- 26,406 bytes parent folder | download
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
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
/*
 * dh.c - Diffie-Helman algorithm code against SSH 2
 *
 * This file is part of the SSH Library
 *
 * Copyright (c) 2003-2008 by Aris Adamantiadis
 * Copyright (c) 2009      by Andreas Schneider <mail@cynapses.org>
 *
 * The SSH Library is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or (at your
 * option) any later version.
 *
 * The SSH Library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with the SSH Library; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

/*
 * Let us resume the dh protocol.
 * Each side computes a private prime number, x at client side, y at server
 * side.
 * g and n are two numbers common to every ssh software.
 * client's public key (e) is calculated by doing:
 * e = g^x mod p
 * client sents e to the server.
 * the server computes his own public key, f
 * f = g^y mod p
 * it sents it to the client
 * the common key K is calculated by the client by doing
 * k = f^x mod p
 * the server does the same with the client public key e
 * k' = e^y mod p
 * if everything went correctly, k and k' are equal
 */

#include "config.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>

#ifndef _WIN32
#include <arpa/inet.h>
#endif

#include "libssh/priv.h"
#include "libssh/crypto.h"
#include "libssh/buffer.h"
#include "libssh/session.h"
#include "libssh/keys.h"
#include "libssh/dh.h"

/* todo: remove it */
#include "libssh/string.h"
#ifdef HAVE_LIBCRYPTO
#include <openssl/rand.h>
#include <openssl/evp.h>
#include <openssl/err.h>
#endif

static unsigned char p_value[] = {
        0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC9, 0x0F, 0xDA, 0xA2,
        0x21, 0x68, 0xC2, 0x34, 0xC4, 0xC6, 0x62, 0x8B, 0x80, 0xDC, 0x1C, 0xD1,
        0x29, 0x02, 0x4E, 0x08, 0x8A, 0x67, 0xCC, 0x74, 0x02, 0x0B, 0xBE, 0xA6,
        0x3B, 0x13, 0x9B, 0x22, 0x51, 0x4A, 0x08, 0x79, 0x8E, 0x34, 0x04, 0xDD,
        0xEF, 0x95, 0x19, 0xB3, 0xCD, 0x3A, 0x43, 0x1B, 0x30, 0x2B, 0x0A, 0x6D,
        0xF2, 0x5F, 0x14, 0x37, 0x4F, 0xE1, 0x35, 0x6D, 0x6D, 0x51, 0xC2, 0x45,
        0xE4, 0x85, 0xB5, 0x76, 0x62, 0x5E, 0x7E, 0xC6, 0xF4, 0x4C, 0x42, 0xE9,
        0xA6, 0x37, 0xED, 0x6B, 0x0B, 0xFF, 0x5C, 0xB6, 0xF4, 0x06, 0xB7, 0xED,
        0xEE, 0x38, 0x6B, 0xFB, 0x5A, 0x89, 0x9F, 0xA5, 0xAE, 0x9F, 0x24, 0x11,
        0x7C, 0x4B, 0x1F, 0xE6, 0x49, 0x28, 0x66, 0x51, 0xEC, 0xE6, 0x53, 0x81,
        0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
#define P_LEN 128	/* Size in bytes of the p number */

static unsigned long g_int = 2 ;	/* G is defined as 2 by the ssh2 standards */
static bignum g;
static bignum p;
static int ssh_crypto_initialized;

int ssh_get_random(void *where, int len, int strong){

#ifdef HAVE_LIBGCRYPT
  /* variable not used in gcrypt */
  (void) strong;
  /* not using GCRY_VERY_STRONG_RANDOM which is a bit overkill */
  gcry_randomize(where,len,GCRY_STRONG_RANDOM);

  return 1;
#elif defined HAVE_LIBCRYPTO
  if (strong) {
    return RAND_bytes(where,len);
  } else {
    return RAND_pseudo_bytes(where,len);
  }
#endif

  /* never reached */
  return 1;
}


/*
 * This inits the values g and p which are used for DH key agreement
 * FIXME: Make the function thread safe by adding a semaphore or mutex.
 */
int ssh_crypto_init(void) {
  if (ssh_crypto_initialized == 0) {
#ifdef HAVE_LIBGCRYPT
    gcry_check_version(NULL);

    if (!gcry_control(GCRYCTL_INITIALIZATION_FINISHED_P,0)) {
      gcry_control(GCRYCTL_INIT_SECMEM, 4096);
      gcry_control(GCRYCTL_INITIALIZATION_FINISHED,0);
    }
#endif

    g = bignum_new();
    if (g == NULL) {
      return -1;
    }
    bignum_set_word(g,g_int);

#ifdef HAVE_LIBGCRYPT
    bignum_bin2bn(p_value, P_LEN, &p);
    if (p == NULL) {
      bignum_free(g);
      g = NULL;
      return -1;
    }
#elif defined HAVE_LIBCRYPTO
    p = bignum_new();
    if (p == NULL) {
      bignum_free(g);
      g = NULL;
      return -1;
    }
    bignum_bin2bn(p_value, P_LEN, p);
    OpenSSL_add_all_algorithms();
#endif

    ssh_crypto_initialized = 1;
  }

  return 0;
}

void ssh_crypto_finalize(void) {
  if (ssh_crypto_initialized) {
    bignum_free(g);
    g = NULL;
    bignum_free(p);
    p = NULL;
    ssh_crypto_initialized=0;
  }
}

/* prints the bignum on stderr */
void ssh_print_bignum(const char *which, bignum num) {
#ifdef HAVE_LIBGCRYPT
  unsigned char *hex = NULL;
  bignum_bn2hex(num, &hex);
#elif defined HAVE_LIBCRYPTO
  char *hex = NULL;
  hex = bignum_bn2hex(num);
#endif
  fprintf(stderr, "%s value: ", which);
  fprintf(stderr, "%s\n", (hex == NULL) ? "(null)" : (char *) hex);
  SAFE_FREE(hex);
}

/**
 * @brief Convert a buffer into a colon separated hex string.
 * The caller has to free the memory.
 *
 * @param  what         What should be converted to a hex string.
 *
 * @param  len          Length of the buffer to convert.
 *
 * @return              The hex string or NULL on error.
 */
char *ssh_get_hexa(const unsigned char *what, size_t len) {
  char *hexa = NULL;
  size_t i;

  if (len > (UINT_MAX - 1) / 3)
    return NULL;

  hexa = malloc(len * 3 + 1);
  if (hexa == NULL) {
    return NULL;
  }

  ZERO_STRUCTP(hexa);

  for (i = 0; i < len; i++) {
    char hex[4];
    snprintf(hex, sizeof(hex), "%02x:", what[i]);
    strcat(hexa, hex);
  }

  hexa[(len * 3) - 1] = '\0';

  return hexa;
}

/**
 * @brief Print a buffer as colon separated hex string.
 *
 * @param  descr        Description printed infront of the hex string.
 *
 * @param  what         What should be converted to a hex string.
 *
 * @param  len          Length of the buffer to convert.
 */
void ssh_print_hexa(const char *descr, const unsigned char *what, size_t len) {
    char *hexa = ssh_get_hexa(what, len);

    if (hexa == NULL) {
      return;
    }
    printf("%s: %s\n", descr, hexa);
}

int dh_generate_x(ssh_session session) {
  int keysize = 1023;

  session->next_crypto->x = bignum_new();
  if (session->next_crypto->x == NULL) {
    return -1;
  }

#ifdef HAVE_LIBGCRYPT
  bignum_rand(session->next_crypto->x, keysize);
#elif defined HAVE_LIBCRYPTO
  bignum_rand(session->next_crypto->x, keysize, -1, 0);
#endif

  /* not harder than this */
#ifdef DEBUG_CRYPTO
  ssh_print_bignum("x", session->next_crypto->x);
#endif

  return 0;
}

/* used by server */
int dh_generate_y(ssh_session session) {
  int keysize = 1023;

    session->next_crypto->y = bignum_new();
  if (session->next_crypto->y == NULL) {
    return -1;
  }

#ifdef HAVE_LIBGCRYPT
  bignum_rand(session->next_crypto->y, keysize);
#elif defined HAVE_LIBCRYPTO
  bignum_rand(session->next_crypto->y, keysize, -1, 0);
#endif

  /* not harder than this */
#ifdef DEBUG_CRYPTO
  ssh_print_bignum("y", session->next_crypto->y);
#endif

  return 0;
}

/* used by server */
int dh_generate_e(ssh_session session) {
#ifdef HAVE_LIBCRYPTO
  bignum_CTX ctx = bignum_ctx_new();
  if (ctx == NULL) {
    return -1;
  }
#endif

  session->next_crypto->e = bignum_new();
  if (session->next_crypto->e == NULL) {
#ifdef HAVE_LIBCRYPTO
    bignum_ctx_free(ctx);
#endif
    return -1;
  }

#ifdef HAVE_LIBGCRYPT
  bignum_mod_exp(session->next_crypto->e, g, session->next_crypto->x, p);
#elif defined HAVE_LIBCRYPTO
  bignum_mod_exp(session->next_crypto->e, g, session->next_crypto->x, p, ctx);
#endif

#ifdef DEBUG_CRYPTO
  ssh_print_bignum("e", session->next_crypto->e);
#endif

#ifdef HAVE_LIBCRYPTO
  bignum_ctx_free(ctx);
#endif

  return 0;
}

int dh_generate_f(ssh_session session) {
#ifdef HAVE_LIBCRYPTO
  bignum_CTX ctx = bignum_ctx_new();
  if (ctx == NULL) {
    return -1;
  }
#endif

  session->next_crypto->f = bignum_new();
  if (session->next_crypto->f == NULL) {
#ifdef HAVE_LIBCRYPTO
    bignum_ctx_free(ctx);
#endif
    return -1;
  }

#ifdef HAVE_LIBGCRYPT
  bignum_mod_exp(session->next_crypto->f, g, session->next_crypto->y, p);
#elif defined HAVE_LIBCRYPTO
  bignum_mod_exp(session->next_crypto->f, g, session->next_crypto->y, p, ctx);
#endif

#ifdef DEBUG_CRYPTO
  ssh_print_bignum("f", session->next_crypto->f);
#endif

#ifdef HAVE_LIBCRYPTO
  bignum_ctx_free(ctx);
#endif

  return 0;
}

ssh_string make_bignum_string(bignum num) {
  ssh_string ptr = NULL;
  int pad = 0;
  unsigned int len = bignum_num_bytes(num);
  unsigned int bits = bignum_num_bits(num);

  /* Remember if the fist bit is set, it is considered as a
   * negative number. So 0's must be appended */
  if (!(bits % 8) && bignum_is_bit_set(num, bits - 1)) {
    pad++;
  }

#ifdef DEBUG_CRYPTO
  fprintf(stderr, "%d bits, %d bytes, %d padding\n", bits, len, pad);
#endif /* DEBUG_CRYPTO */
/* TODO: fix that crap !! */
  ptr = malloc(4 + len + pad);
  if (ptr == NULL) {
    return NULL;
  }
  ptr->size = htonl(len + pad);
  if (pad) {
    ptr->string[0] = 0;
  }

#ifdef HAVE_LIBGCRYPT
  bignum_bn2bin(num, len, ptr->string + pad);
#elif HAVE_LIBCRYPTO
  bignum_bn2bin(num, ptr->string + pad);
#endif

  return ptr;
}

bignum make_string_bn(ssh_string string){
  bignum bn = NULL;
  unsigned int len = string_len(string);

#ifdef DEBUG_CRYPTO
  fprintf(stderr, "Importing a %d bits, %d bytes object ...\n",
      len * 8, len);
#endif /* DEBUG_CRYPTO */

#ifdef HAVE_LIBGCRYPT
  bignum_bin2bn(string->string, len, &bn);
#elif defined HAVE_LIBCRYPTO
  bn = bignum_bin2bn(string->string, len, NULL);
#endif

  return bn;
}

ssh_string dh_get_e(ssh_session session) {
  return make_bignum_string(session->next_crypto->e);
}

/* used by server */
ssh_string dh_get_f(ssh_session session) {
  return make_bignum_string(session->next_crypto->f);
}

void dh_import_pubkey(ssh_session session, ssh_string pubkey_string) {
  session->next_crypto->server_pubkey = pubkey_string;
}

int dh_import_f(ssh_session session, ssh_string f_string) {
  session->next_crypto->f = make_string_bn(f_string);
  if (session->next_crypto->f == NULL) {
    return -1;
  }

#ifdef DEBUG_CRYPTO
  ssh_print_bignum("f",session->next_crypto->f);
#endif

  return 0;
}

/* used by the server implementation */
int dh_import_e(ssh_session session, ssh_string e_string) {
  session->next_crypto->e = make_string_bn(e_string);
  if (session->next_crypto->e == NULL) {
    return -1;
  }

#ifdef DEBUG_CRYPTO
    ssh_print_bignum("e",session->next_crypto->e);
#endif

  return 0;
}

int dh_build_k(ssh_session session) {
#ifdef HAVE_LIBCRYPTO
  bignum_CTX ctx = bignum_ctx_new();
  if (ctx == NULL) {
    return -1;
  }
#endif

  session->next_crypto->k = bignum_new();
  if (session->next_crypto->k == NULL) {
#ifdef HAVE_LIBCRYPTO
    bignum_ctx_free(ctx);
#endif
    return -1;
  }

    /* the server and clients don't use the same numbers */
#ifdef HAVE_LIBGCRYPT
  if(session->client) {
    bignum_mod_exp(session->next_crypto->k, session->next_crypto->f,
        session->next_crypto->x, p);
  } else {
    bignum_mod_exp(session->next_crypto->k, session->next_crypto->e,
        session->next_crypto->y, p);
  }
#elif defined HAVE_LIBCRYPTO
  if (session->client) {
    bignum_mod_exp(session->next_crypto->k, session->next_crypto->f,
        session->next_crypto->x, p, ctx);
  } else {
    bignum_mod_exp(session->next_crypto->k, session->next_crypto->e,
        session->next_crypto->y, p, ctx);
  }
#endif

#ifdef DEBUG_CRYPTO
  ssh_print_hexa("Session server cookie", session->server_kex.cookie, 16);
  ssh_print_hexa("Session client cookie", session->client_kex.cookie, 16);
  ssh_print_bignum("Shared secret key", session->next_crypto->k);
#endif

#ifdef HAVE_LIBCRYPTO
  bignum_ctx_free(ctx);
#endif

  return 0;
}

/*
static void sha_add(ssh_string str,SHACTX ctx){
    sha1_update(ctx,str,string_len(str)+4);
#ifdef DEBUG_CRYPTO
    ssh_print_hexa("partial hashed sessionid",str,string_len(str)+4);
#endif
}
*/

int make_sessionid(ssh_session session) {
  SHACTX ctx;
  ssh_string num = NULL;
  ssh_string str = NULL;
  ssh_buffer server_hash = NULL;
  ssh_buffer client_hash = NULL;
  ssh_buffer buf = NULL;
  uint32_t len;
  int rc = SSH_ERROR;

  enter_function();

  ctx = sha1_init();
  if (ctx == NULL) {
    return rc;
  }

  buf = buffer_new();
  if (buf == NULL) {
    return rc;
  }

  str = string_from_char(session->clientbanner);
  if (str == NULL) {
    goto error;
  }

  if (buffer_add_ssh_string(buf, str) < 0) {
    goto error;
  }
  string_free(str);

  str = string_from_char(session->serverbanner);
  if (str == NULL) {
    goto error;
  }

  if (buffer_add_ssh_string(buf, str) < 0) {
    goto error;
  }

  if (session->client) {
    server_hash = session->in_hashbuf;
    client_hash = session->out_hashbuf;
  } else {
    server_hash = session->out_hashbuf;
    client_hash = session->in_hashbuf;
  }

  if (buffer_add_u32(server_hash, 0) < 0) {
    goto error;
  }
  if (buffer_add_u8(server_hash, 0) < 0) {
    goto error;
  }
  if (buffer_add_u32(client_hash, 0) < 0) {
    goto error;
  }
  if (buffer_add_u8(client_hash, 0) < 0) {
    goto error;
  }

  len = ntohl(buffer_get_len(client_hash));
  if (buffer_add_u32(buf,len) < 0) {
    goto error;
  }
  if (buffer_add_data(buf, buffer_get(client_hash),
        buffer_get_len(client_hash)) < 0) {
    goto error;
  }

  len = ntohl(buffer_get_len(server_hash));
  if (buffer_add_u32(buf, len) < 0) {
    goto error;
  }
  if (buffer_add_data(buf, buffer_get(server_hash),
        buffer_get_len(server_hash)) < 0) {
    goto error;
  }

  len = string_len(session->next_crypto->server_pubkey) + 4;
  if (buffer_add_data(buf, session->next_crypto->server_pubkey, len) < 0) {
    goto error;
  }

  num = make_bignum_string(session->next_crypto->e);
  if (num == NULL) {
    goto error;
  }

  len = string_len(num) + 4;
  if (buffer_add_data(buf, num, len) < 0) {
    goto error;
  }

  string_free(num);
  num = make_bignum_string(session->next_crypto->f);
  if (num == NULL) {
    goto error;
  }

  len = string_len(num) + 4;
  if (buffer_add_data(buf, num, len) < 0) {
    goto error;
  }

  string_free(num);
  num = make_bignum_string(session->next_crypto->k);
  if (num == NULL) {
    goto error;
  }

  len = string_len(num) + 4;
  if (buffer_add_data(buf, num, len) < 0) {
    goto error;
  }

#ifdef DEBUG_CRYPTO
  ssh_print_hexa("hash buffer", buffer_get(buf), buffer_get_len(buf));
#endif

  sha1_update(ctx, buffer_get(buf), buffer_get_len(buf));
  sha1_final(session->next_crypto->session_id, ctx);

#ifdef DEBUG_CRYPTO
  printf("Session hash: ");
  ssh_print_hexa("session id", session->next_crypto->session_id, SHA_DIGEST_LEN);
#endif

  rc = SSH_OK;
error:
  buffer_free(buf);
  buffer_free(client_hash);
  buffer_free(server_hash);

  session->in_hashbuf = NULL;
  session->out_hashbuf = NULL;

  string_free(str);
  string_free(num);

  leave_function();

  return rc;
}

int hashbufout_add_cookie(ssh_session session) {
  session->out_hashbuf = buffer_new();
  if (session->out_hashbuf == NULL) {
    return -1;
  }

  if (buffer_add_u8(session->out_hashbuf, 20) < 0) {
    buffer_reinit(session->out_hashbuf);
    return -1;
  }

  if (session->server) {
    if (buffer_add_data(session->out_hashbuf,
          session->server_kex.cookie, 16) < 0) {
      buffer_reinit(session->out_hashbuf);
      return -1;
    }
  } else {
    if (buffer_add_data(session->out_hashbuf,
          session->client_kex.cookie, 16) < 0) {
      buffer_reinit(session->out_hashbuf);
      return -1;
    }
  }

  return 0;
}

int hashbufin_add_cookie(ssh_session session, unsigned char *cookie) {
  session->in_hashbuf = buffer_new();
  if (session->in_hashbuf == NULL) {
    return -1;
  }

  if (buffer_add_u8(session->in_hashbuf, 20) < 0) {
    buffer_reinit(session->in_hashbuf);
    return -1;
  }
  if (buffer_add_data(session->in_hashbuf,cookie, 16) < 0) {
    buffer_reinit(session->in_hashbuf);
    return -1;
  }

  return 0;
}

static int generate_one_key(ssh_string k,
    unsigned char session_id[SHA_DIGEST_LEN],
    unsigned char output[SHA_DIGEST_LEN],
    char letter) {
  SHACTX ctx = NULL;

  ctx = sha1_init();
  if (ctx == NULL) {
    return -1;
  }

  sha1_update(ctx, k, string_len(k) + 4);
  sha1_update(ctx, session_id, SHA_DIGEST_LEN);
  sha1_update(ctx, &letter, 1);
  sha1_update(ctx, session_id, SHA_DIGEST_LEN);
  sha1_final(output, ctx);

  return 0;
}

int generate_session_keys(ssh_session session) {
  ssh_string k_string = NULL;
  SHACTX ctx = NULL;
  int rc = -1;

  enter_function();

  k_string = make_bignum_string(session->next_crypto->k);
  if (k_string == NULL) {
    goto error;
  }

  /* IV */
  if (session->client) {
    if (generate_one_key(k_string, session->next_crypto->session_id,
          session->next_crypto->encryptIV, 'A') < 0) {
      goto error;
    }
    if (generate_one_key(k_string, session->next_crypto->session_id,
          session->next_crypto->decryptIV, 'B') < 0) {
      goto error;
    }
  } else {
    if (generate_one_key(k_string, session->next_crypto->session_id,
          session->next_crypto->decryptIV, 'A') < 0) {
      goto error;
    }
    if (generate_one_key(k_string, session->next_crypto->session_id,
          session->next_crypto->encryptIV, 'B') < 0) {
      goto error;
    }
  }
  if (session->client) {
    if (generate_one_key(k_string, session->next_crypto->session_id,
          session->next_crypto->encryptkey, 'C') < 0) {
      goto error;
    }
    if (generate_one_key(k_string, session->next_crypto->session_id,
          session->next_crypto->decryptkey, 'D') < 0) {
      goto error;
    }
  } else {
    if (generate_one_key(k_string, session->next_crypto->session_id,
          session->next_crypto->decryptkey, 'C') < 0) {
      goto error;
    }
    if (generate_one_key(k_string, session->next_crypto->session_id,
          session->next_crypto->encryptkey, 'D') < 0) {
      goto error;
    }
  }

  /* some ciphers need more than 20 bytes of input key */
  /* XXX verify it's ok for server implementation */
  if (session->next_crypto->out_cipher->keysize > SHA_DIGEST_LEN * 8) {
    ctx = sha1_init();
    if (ctx == NULL) {
      goto error;
    }
    sha1_update(ctx, k_string, string_len(k_string) + 4);
    sha1_update(ctx, session->next_crypto->session_id, SHA_DIGEST_LEN);
    sha1_update(ctx, session->next_crypto->encryptkey, SHA_DIGEST_LEN);
    sha1_final(session->next_crypto->encryptkey + SHA_DIGEST_LEN, ctx);
  }

  if (session->next_crypto->in_cipher->keysize > SHA_DIGEST_LEN * 8) {
    ctx = sha1_init();
    sha1_update(ctx, k_string, string_len(k_string) + 4);
    sha1_update(ctx, session->next_crypto->session_id, SHA_DIGEST_LEN);
    sha1_update(ctx, session->next_crypto->decryptkey, SHA_DIGEST_LEN);
    sha1_final(session->next_crypto->decryptkey + SHA_DIGEST_LEN, ctx);
  }
  if(session->client) {
    if (generate_one_key(k_string, session->next_crypto->session_id,
          session->next_crypto->encryptMAC, 'E') < 0) {
      goto error;
    }
    if (generate_one_key(k_string, session->next_crypto->session_id,
          session->next_crypto->decryptMAC, 'F') < 0) {
      goto error;
    }
  } else {
    if (generate_one_key(k_string, session->next_crypto->session_id,
          session->next_crypto->decryptMAC, 'E') < 0) {
      goto error;
    }
    if (generate_one_key(k_string, session->next_crypto->session_id,
          session->next_crypto->encryptMAC, 'F') < 0) {
      goto error;
    }
  }

#ifdef DEBUG_CRYPTO
  ssh_print_hexa("Encrypt IV", session->next_crypto->encryptIV, SHA_DIGEST_LEN);
  ssh_print_hexa("Decrypt IV", session->next_crypto->decryptIV, SHA_DIGEST_LEN);
  ssh_print_hexa("Encryption key", session->next_crypto->encryptkey,
      session->next_crypto->out_cipher->keysize);
  ssh_print_hexa("Decryption key", session->next_crypto->decryptkey,
      session->next_crypto->in_cipher->keysize);
  ssh_print_hexa("Encryption MAC", session->next_crypto->encryptMAC, SHA_DIGEST_LEN);
  ssh_print_hexa("Decryption MAC", session->next_crypto->decryptMAC, 20);
#endif

  rc = 0;
error:
  string_free(k_string);
  leave_function();

  return rc;
}

/** \addtogroup ssh_session
 * @{ */
/**
 * @brief Allocates a buffer with the MD5 hash of the server public key.
 *
 * @param  session      The SSH session to use.
 *
 * @param  hash         The buffer to allocate.
 *
 * @return The bytes allocated or < 0 on error.
 *
 * @warning It is very important that you verify at some moment that the hash
 *          matches a known server. If you don't do it, cryptography wont help
 *          you at making things secure
 *
 * @see ssh_is_server_known()
 * @see ssh_get_hexa()
 * @see ssh_print_hexa()
 */
int ssh_get_pubkey_hash(ssh_session session, unsigned char **hash) {
  ssh_string pubkey;
  MD5CTX ctx;
  unsigned char *h;

  if (session == NULL || hash == NULL) {
    return -1;
  }

  *hash = NULL;

  h = malloc(sizeof(unsigned char *) * MD5_DIGEST_LEN);
  if (h == NULL) {
    return -1;
  }

  ctx = md5_init();
  if (ctx == NULL) {
    SAFE_FREE(h);
    return -1;
  }

  pubkey = session->current_crypto->server_pubkey;

  md5_update(ctx, pubkey->string, string_len(pubkey));
  md5_final(h, ctx);

  *hash = h;

  return MD5_DIGEST_LEN;
}

/**
 * @brief Deallocate the hash obtained by ssh_get_pubkey_hash.
 * This is required under Microsoft platform as this library might use a 
 * different C library than your software, hence a different heap.
 *
 * @param  hash         The buffer to deallocate.
 *
 * @see ssh_get_pubkey_hash()
 */
void ssh_clean_pubkey_hash(unsigned char **hash) {
  SAFE_FREE(*hash);
  *hash = NULL;
}

ssh_string ssh_get_pubkey(ssh_session session){
    return string_copy(session->current_crypto->server_pubkey);
}

static int match(const char *group, const char *object){
  const char *a;
  const char *z;

  a = z = group;
  do {
    a = strchr(z, ',');
    if (a == NULL) {
      if (strcmp(z, object) == 0) {
        return 1;
      }
      return 0;
    } else {
      if (strncmp(z, object, a - z) == 0) {
        return 1;
      }
    }
    z = a + 1;
  } while(1);

  /* not reached */
  return 0;
}

int sig_verify(ssh_session session, ssh_public_key pubkey,
    SIGNATURE *signature, unsigned char *digest, int size) {
#ifdef HAVE_LIBGCRYPT
  gcry_error_t valid = 0;
  gcry_sexp_t gcryhash;
#elif defined HAVE_LIBCRYPTO
  int valid = 0;
#endif
  unsigned char hash[SHA_DIGEST_LEN + 1] = {0};

  sha1(digest, size, hash + 1);

#ifdef DEBUG_CRYPTO
  ssh_print_hexa("Hash to be verified with dsa", hash + 1, SHA_DIGEST_LEN);
#endif

  switch(pubkey->type) {
    case TYPE_DSS:
#ifdef HAVE_LIBGCRYPT
      valid = gcry_sexp_build(&gcryhash, NULL, "%b", SHA_DIGEST_LEN + 1, hash);
      if (valid != 0) {
        ssh_set_error(session, SSH_FATAL,
            "RSA error: %s", gcry_strerror(valid));
        return -1;
      }
      valid = gcry_pk_verify(signature->dsa_sign, gcryhash, pubkey->dsa_pub);
      gcry_sexp_release(gcryhash);
      if (valid == 0) {
        return 0;
      }

      if (gcry_err_code(valid) != GPG_ERR_BAD_SIGNATURE) {
        ssh_set_error(session, SSH_FATAL,
            "DSA error: %s", gcry_strerror(valid));
        return -1;
      }
#elif defined HAVE_LIBCRYPTO
      valid = DSA_do_verify(hash + 1, SHA_DIGEST_LEN, signature->dsa_sign,
          pubkey->dsa_pub);
      if (valid == 1) {
        return 0;
      }

      if (valid == -1) {
        ssh_set_error(session, SSH_FATAL,
            "DSA error: %s", ERR_error_string(ERR_get_error(), NULL));
        return -1;
      }
#endif
      ssh_set_error(session, SSH_FATAL, "Invalid DSA signature");
      return -1;

    case TYPE_RSA:
    case TYPE_RSA1:
#ifdef HAVE_LIBGCRYPT
      valid = gcry_sexp_build(&gcryhash, NULL,
          "(data(flags pkcs1)(hash sha1 %b))", SHA_DIGEST_LEN, hash + 1);
      if (valid != 0) {
        ssh_set_error(session, SSH_FATAL,
            "RSA error: %s", gcry_strerror(valid));
        return -1;
      }
      valid = gcry_pk_verify(signature->rsa_sign,gcryhash,pubkey->rsa_pub);
      gcry_sexp_release(gcryhash);
      if (valid == 0) {
        return 0;
      }
      if (gcry_err_code(valid) != GPG_ERR_BAD_SIGNATURE) {
        ssh_set_error(session, SSH_FATAL,
            "RSA error: %s", gcry_strerror(valid));
        return -1;
      }
#elif defined HAVE_LIBCRYPTO
      valid = RSA_verify(NID_sha1, hash + 1, SHA_DIGEST_LEN,
          signature->rsa_sign->string, string_len(signature->rsa_sign),
          pubkey->rsa_pub);
      if (valid == 1) {
        return 0;
      }
      if (valid == -1) {
        ssh_set_error(session, SSH_FATAL,
            "RSA error: %s", ERR_error_string(ERR_get_error(), NULL));
        return -1;
      }
#endif
      ssh_set_error(session, SSH_FATAL, "Invalid RSA signature");
      return -1;
    default:
      ssh_set_error(session, SSH_FATAL, "Unknown public key type");
      return -1;
  }

  return -1;
}

int signature_verify(ssh_session session, ssh_string signature) {
  ssh_public_key pubkey = NULL;
  SIGNATURE *sign = NULL;
  int err;

  enter_function();

  pubkey = publickey_from_string(session,session->next_crypto->server_pubkey);
  if(pubkey == NULL) {
    leave_function();
    return -1;
  }

  if (session->wanted_methods[SSH_HOSTKEYS]) {
    if(!match(session->wanted_methods[SSH_HOSTKEYS],pubkey->type_c)) {
      ssh_set_error(session, SSH_FATAL,
          "Public key from server (%s) doesn't match user preference (%s)",
          pubkey->type_c, session->wanted_methods[SSH_HOSTKEYS]);
      publickey_free(pubkey);
      leave_function();
      return -1;
    }
  }

  sign = signature_from_string(session, signature, pubkey, pubkey->type);
  if (sign == NULL) {
    ssh_set_error(session, SSH_FATAL, "Invalid signature blob");
    publickey_free(pubkey);
    leave_function();
    return -1;
  }

  ssh_log(session, SSH_LOG_FUNCTIONS,
      "Going to verify a %s type signature", pubkey->type_c);

  err = sig_verify(session,pubkey,sign,
                            session->next_crypto->session_id,SHA_DIGEST_LEN);
  signature_free(sign);
  session->next_crypto->server_pubkey_type = pubkey->type_c;
  publickey_free(pubkey);

  leave_function();
  return err;
}

/** @} */
/* vim: set ts=2 sw=2 et cindent: */