summaryrefslogtreecommitdiffstats
path: root/src/ntlm_crypto.c
blob: a51b03e706d543fde03d29793dba2560419b6459 (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
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
/*
   Copyright (C) 2013 Simo Sorce <simo@samba.org>

   This 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 3 of the License, or (at your option) any later version.

   This 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 this library; if not, see <http://www.gnu.org/licenses/>.
*/


/* This File implements the NTLM protocol as specified by:
 *      [MS-NLMP]: NT LAN Manager (NTLM) Authentication Protocol
 *
 * Additional cross checking with:
 * http://davenport.sourceforge.net/ntlm.html
 */

#include <errno.h>
#include <stddef.h>
#include <string.h>

#include <unicase.h>
#include <uniconv.h>

#include "ntlm.h"
#include "crypto.h"

/* lm response, v1 or v2 */
#pragma pack(push, 1)
union wire_lm_response {
    struct {
        uint8_t resp[24];
    } v1;
    struct {
        uint8_t resp[16];
        uint8_t cli_chal[8];
    } v2;
};
#pragma pack(pop)

/* ntlm response, v1 or v2 */
#pragma pack(push, 1)
union wire_ntlm_response {
    struct {
        uint8_t resp[24];
    } v1;
    struct {
        uint8_t resp[16];
        uint8_t cli_chal[];
    } v2;
};
#pragma pack(pop)

#pragma pack(push, 1)
struct wire_ntlmv2_cli_chal {
    uint8_t resp_version;
    uint8_t hi_resp_version;
    uint8_t zero_6[6];
    uint64_t timestamp;
    uint8_t client_chal[8];
    uint8_t zero_4[4];
    uint8_t target_info[];
        /* NOTE: the target_info array must terminate with 4 zero bytes.
         * This is consistent with just copying the target_info array
         * returned in the challenge message as the last AV_PAIR there is
         * always MSV_AV_EOL which happens to be 4 bytes of zeros */
};
#pragma pack(pop)

/* the max username is 20 chars, max NB domain len is 15, so 128 should be
 * plenty including conversion to UTF8 using max lenght for each code point
 */
#define MAX_USER_DOM_LEN 512


int NTOWFv1(const char *password, struct ntlm_key *result)
{
    struct ntlm_buffer payload;
    struct ntlm_buffer hash;
    char *retstr;
    size_t out;
    size_t len;
    int ret;

    len = strlen(password);
    retstr = u8_conv_to_encoding("UCS-2LE", iconveh_error,
                                 (const uint8_t *)password, len,
                                 NULL, NULL, &out);
    if (!retstr) return ERR_CRYPTO;

    payload.data = (uint8_t *)retstr;
    payload.length = out;
    hash.data = result->data;
    hash.length = result->length;

    ret = MD4_HASH(&payload, &hash);
    free(retstr);
    return ret;
}

#define DES_CONST "KGS!@#$%"
int LMOWFv1(const char *password, struct ntlm_key *result)
{
    struct ntlm_buffer key;
    struct ntlm_buffer plain;
    struct ntlm_buffer cipher;
    char upcased[15];
    char *retstr;
    size_t out;
    size_t len;
    int ret;

    if (result->length != 16) return EINVAL;

    len = strlen(password);
    if (len > 14) return ERANGE;

    out = 15;
    retstr = (char *)u8_toupper((const uint8_t *)password, len,
                                NULL, NULL, (uint8_t *)upcased, &out);
    if (!retstr) return ERR_CRYPTO;
    if (retstr != upcased) {
        free(retstr);
        ret = EINVAL;
    }
    memset(&upcased[len], 0, 15 - len);

    /* part1 */
    key.data = (uint8_t *)upcased;
    key.length = 7;
    plain.data = discard_const(DES_CONST);
    plain.length = 8;
    cipher.data = result->data;
    cipher.length = 8;
    ret = WEAK_DES(&key, &plain, &cipher);
    if (ret) return ret;

    /* part2 */
    key.data = (uint8_t *)&upcased[7];
    key.length = 7;
    plain.data = discard_const(DES_CONST);
    plain.length = 8;
    cipher.data = &result->data[8];
    cipher.length = 8;
    return WEAK_DES(&key, &plain, &cipher);
}

int ntlm_compute_nt_response(struct ntlm_key *nt_key, bool ext_sec,
                             uint8_t server_chal[8], uint8_t client_chal[8],
                             struct ntlm_buffer *nt_response)
{
    struct ntlm_buffer key = { nt_key->data, nt_key->length };
    struct ntlm_buffer payload;
    struct ntlm_buffer result;
    uint8_t buf1[16];
    uint8_t buf2[16];
    int ret;

    memcpy(buf1, server_chal, 8);
    if (ext_sec) {
        memcpy(&buf1[8], client_chal, 8);
        payload.data = buf1;
        payload.length = 16;
        result.data = buf2;
        result.length = 16;
        ret = MD5_HASH(&payload, &result);
        if (ret) return ret;
        memcpy(buf1, result.data, 8);
    }
    payload.data = buf1;
    payload.length = 8;

    return DESL(&key, &payload, nt_response);
}

int ntlm_compute_lm_response(struct ntlm_key *lm_key, bool ext_sec,
                             uint8_t server_chal[8], uint8_t client_chal[8],
                             struct ntlm_buffer *lm_response)
{
    struct ntlm_buffer key = { lm_key->data, lm_key->length };
    struct ntlm_buffer payload = { server_chal, 8 };

    if (ext_sec) {
        memcpy(lm_response->data, client_chal, 8);
        memset(&lm_response->data[8], 0, 16);
        return 0;
    }
    return DESL(&key, &payload, lm_response);
}

int ntlm_session_base_key(struct ntlm_key *nt_key,
                          struct ntlm_key *session_base_key)
{
    struct ntlm_buffer payload = { nt_key->data, nt_key->length };
    struct ntlm_buffer hash = { session_base_key->data,
                                session_base_key->length };

    return MD4_HASH(&payload, &hash);
}

int KXKEY(struct ntlm_ctx *ctx,
          bool ext_sec,
          bool neg_lm_key,
          bool non_nt_sess_key,
          uint8_t server_chal[8],
          struct ntlm_key *lm_key,
          struct ntlm_key *session_base_key,
          struct ntlm_buffer *lm_response,
          struct ntlm_key *key_exchange_key)
{
    struct ntlm_buffer payload;
    struct ntlm_buffer result;
    struct ntlm_buffer key;
    uint8_t buf[16];
    int ret = 0;

    if (ext_sec) {
        key.data = session_base_key->data;
        key.length = session_base_key->length;
        memcpy(buf, server_chal, 8);
        memcpy(&buf[8], lm_response->data, 8);
        payload.data = buf;
        payload.length = 16;
        result.data = key_exchange_key->data;
        result.length = key_exchange_key->length;
        ret = HMAC_MD5(&key, &payload, &result);
    } else if (neg_lm_key) {
        payload.data = lm_response->data;
        payload.length = 8;
        key.data = lm_key->data;
        key.length = 7;
        result.data = key_exchange_key->data;
        result.length = 8;
        ret = WEAK_DES(&key, &payload, &result);
        if (ret) return ret;
        buf[0] = lm_key->data[7];
        memset(&buf[1], 0xbd, 6);
        key.data = buf;
        result.data = &key_exchange_key->data[8];
        result.length = 8;
        ret = WEAK_DES(&key, &payload, &result);
    } else if (non_nt_sess_key) {
        memcpy(key_exchange_key->data, lm_key, 8);
        memset(&key_exchange_key->data[8], 0, 8);
    } else {
        memcpy(key_exchange_key->data, session_base_key->data, 16);
    }
    return ret;
}

int NTOWFv2(struct ntlm_ctx *ctx, struct ntlm_key *nt_hash,
            const char *user, const char *domain, struct ntlm_key *result)
{
    struct ntlm_buffer key = { nt_hash->data, nt_hash->length };
    struct ntlm_buffer hmac = { result->data, result->length };
    struct ntlm_buffer payload;
    uint8_t upcased[MAX_USER_DOM_LEN];
    uint8_t *retstr;
    size_t offs;
    size_t out;
    size_t len;
    int ret;

    len = strlen(user);
    out = MAX_USER_DOM_LEN;
    retstr = u8_toupper((const uint8_t *)user, len,
                        NULL, NULL, upcased, &out);
    if (!retstr) return ERR_CRYPTO;
    offs = out;

    if (domain) {
        len = strlen(domain);
        memcpy(&upcased[offs], domain, len);
        offs += len;
    }

    retstr = (uint8_t *)u8_conv_to_encoding("UCS-2LE", iconveh_error,
                                            upcased, offs, NULL, NULL, &out);
    if (!retstr) return ERR_CRYPTO;

    payload.data = (uint8_t *)retstr;
    payload.length = out;

    ret = HMAC_MD5(&key, &payload, &hmac);
    free(retstr);
    return ret;
}

int ntlmv2_compute_nt_response(struct ntlm_key *ntlmv2_key,
                               uint8_t server_chal[8], uint8_t client_chal[8],
                               uint64_t timestamp,
                               struct ntlm_buffer *target_info,
                               struct ntlm_buffer *nt_response)
{
    union wire_ntlm_response *nt_resp = NULL;
    struct wire_ntlmv2_cli_chal *r;
    struct ntlm_buffer key = { ntlmv2_key->data, ntlmv2_key->length };
    struct ntlm_buffer payload;
    struct ntlm_buffer nt_proof;
    size_t r_len;
    int ret;

    /* add additional 4 0s trailing target_info */
    r_len = sizeof(struct wire_ntlmv2_cli_chal) + target_info->length + 4;
    nt_resp = calloc(1, sizeof(nt_resp->v2) + r_len);
    if (!nt_resp) return ENOMEM;

    r = (struct wire_ntlmv2_cli_chal *)nt_resp->v2.cli_chal;
    r->resp_version = 1;
    r->hi_resp_version = 1;
    r->timestamp = htole64(timestamp);
    memcpy(r->client_chal, client_chal, 8);
    memcpy(r->target_info, target_info->data, target_info->length);

    /* use nt_resp as a buffer to calculate the NT proof as they share
     * the cli_chal part */
    payload.data = &nt_resp->v2.resp[8];
    payload.length = 8 + r_len;
    memcpy(payload.data, server_chal, 8);
    nt_proof.data = nt_resp->v2.resp;
    nt_proof.length = 16;
    ret = HMAC_MD5(&key, &payload, &nt_proof);

    if (ret) {
        safefree(nt_resp);
    } else {
        nt_response->data = (uint8_t *)nt_resp;
        nt_response->length = 16 + r_len;
    }
    return ret;
}

int ntlmv2_compute_lm_response(struct ntlm_key *ntlmv2_key,
                               uint8_t server_chal[8], uint8_t client_chal[8],
                               struct ntlm_buffer *lm_response)
{
    union wire_lm_response *lm_resp = NULL;
    struct ntlm_buffer key = { ntlmv2_key->data, ntlmv2_key->length };
    uint8_t payload_buf[16];
    struct ntlm_buffer payload = { payload_buf, 16 };
    struct ntlm_buffer lm_proof;
    int ret;

    /* now caluclate the LM Proof */
    lm_resp = malloc(sizeof(union wire_lm_response));
    if (!lm_resp) {
        ret = ENOMEM;
        goto done;
    }

    memcpy(payload.data, server_chal, 8);
    memcpy(&payload.data[8], client_chal, 8);
    lm_proof.data = lm_resp->v2.resp;
    lm_proof.length = 16;
    ret = HMAC_MD5(&key, &payload, &lm_proof);

done:
    if (ret) {
        safefree(lm_resp);
    } else {
        memcpy(lm_resp->v2.cli_chal, client_chal, 8);

        lm_response->data = (uint8_t *)lm_resp;
        lm_response->length = 24;
    }
    return ret;
}

int ntlmv2_session_base_key(struct ntlm_key *ntlmv2_key,
                            struct ntlm_buffer *nt_response,
                            struct ntlm_key *session_base_key)
{
    struct ntlm_buffer key = { ntlmv2_key->data, ntlmv2_key->length };
    struct ntlm_buffer hmac = { session_base_key->data,
                                session_base_key->length };

    if (session_base_key->length != 16) return EINVAL;

    return HMAC_MD5(&key, nt_response, &hmac);
}

int ntlm_exported_session_key(struct ntlm_key *key_exchange_key,
                              bool key_exch,
                              struct ntlm_key *exported_session_key)
{
    struct ntlm_buffer nonce;

    if (!key_exch) {
        *exported_session_key = *key_exchange_key;
        return 0;
    }

    exported_session_key->length = 16;
    nonce.data = exported_session_key->data;
    nonce.length = exported_session_key->length;
    return RAND_BUFFER(&nonce);
}

int ntlm_encrypted_session_key(struct ntlm_key *key,
                               struct ntlm_key *in, struct ntlm_key *out)
{
    struct ntlm_buffer _key = { key->data, key->length };
    struct ntlm_buffer data = { in->data, in->length };
    struct ntlm_buffer result = { out->data, out->length };

    return RC4K(&_key, NTLM_CIPHER_ENCRYPT, &data, &result);
}

static int ntlm_key_derivation_function(struct ntlm_key *key,
                                        const char *magic_constant,
                                        struct ntlm_key *derived_key)
{
    uint8_t buf[80]; /* key + constant is never larger than 80 */
    struct ntlm_buffer payload = { buf, 0 };
    struct ntlm_buffer result = { derived_key->data, 16 };
    size_t len;
    int ret;

    if (key->length > 16) return ERR_CRYPTO;
    len = strlen(magic_constant) + 1;
    if (len > 64) return ERR_CRYPTO;

    payload.length = key->length;
    memcpy(payload.data, key->data, key->length);
    memcpy(&payload.data[payload.length], magic_constant, len);
    payload.length += len;

    ret = MD5_HASH(&payload, &result);
    if (ret == 0) {
        derived_key->length = 16;
    }
    return ret;
}

#define NTLM_MODE_CLIENT true
#define NTLM_MODE_SERVER false

static int ntlm_signkey(uint32_t flags, bool mode,
                        struct ntlm_key *random_session_key,
                        struct ntlm_key *signing_key)
{
    const char *mc;

    if (flags & NTLMSSP_NEGOTIATE_EXTENDED_SESSIONSECURITY) {
        if (mode == NTLM_MODE_CLIENT) {
            mc = "session key to client-to-server signing key magic constant";
        } else {
            mc = "session key to server-to-client signing key magic constant";
        }
        return ntlm_key_derivation_function(random_session_key,
                                            mc, signing_key);
    } else {
        signing_key->length = 0;
    }
    return 0;
}

static int ntlm_sealkey(uint32_t flags, bool mode,
                        struct ntlm_key *random_session_key,
                        struct ntlm_key *sealing_key)
{
    struct ntlm_key key;
    const char *mc;

    if (flags & NTLMSSP_NEGOTIATE_EXTENDED_SESSIONSECURITY) {
        if (flags & NTLMSSP_NEGOTIATE_128) {
            key.length = 16;
        } else if (flags & NTLMSSP_NEGOTIATE_56) {
            key.length = 7;
        } else {
            key.length = 5;
        }
        memcpy(key.data, random_session_key->data, key.length);

        if (mode == NTLM_MODE_CLIENT) {
            mc = "session key to client-to-server sealing key magic constant";
        } else {
            mc = "session key to server-to-client sealing key magic constant";
        }

        return ntlm_key_derivation_function(&key, mc, sealing_key);

    } else if (flags & NTLMSSP_NEGOTIATE_LM_KEY) {
        if (flags & NTLMSSP_NEGOTIATE_56) {
            memcpy(sealing_key->data, random_session_key->data, 7);
            sealing_key->data[7] = 0xA0;
        } else {
            memcpy(sealing_key->data, random_session_key->data, 5);
            sealing_key->data[5] = 0xE5;
            sealing_key->data[6] = 0x38;
            sealing_key->data[7] = 0xB0;
        }
        sealing_key->length = 8;
    } else {
        *sealing_key = *random_session_key;
    }
    return 0;
}

int ntlm_signseal_keys(uint32_t flags, bool client,
                       struct ntlm_key *random_session_key,
                       struct ntlm_key *sign_send_key,
                       struct ntlm_key *sign_recv_key,
                       struct ntlm_key *seal_send_key,
                       struct ntlm_key *seal_recv_key,
                       struct ntlm_rc4_handle **seal_send_handle,
                       struct ntlm_rc4_handle **seal_recv_handle)
{
    struct ntlm_buffer rc4_key;
    bool mode;
    int ret;

    /* send key */
    mode = client ? NTLM_MODE_CLIENT : NTLM_MODE_SERVER;
    ret = ntlm_signkey(flags, mode, random_session_key, sign_send_key);
    if (ret) return ret;
    /* recv key */
    mode = client ? NTLM_MODE_SERVER : NTLM_MODE_CLIENT;
    ret = ntlm_signkey(flags, mode, random_session_key, sign_recv_key);
    if (ret) return ret;

    /* send key */
    mode = client ? NTLM_MODE_CLIENT : NTLM_MODE_SERVER;
    ret = ntlm_sealkey(flags, mode, random_session_key, seal_send_key);
    if (ret) return ret;
    /* recv key */
    mode = client ? NTLM_MODE_SERVER : NTLM_MODE_CLIENT;
    ret = ntlm_sealkey(flags, mode, random_session_key, seal_recv_key);
    if (ret) return ret;

    rc4_key.data = seal_send_key->data;
    rc4_key.length = seal_send_key->length;
    ret = RC4_INIT(&rc4_key, NTLM_CIPHER_ENCRYPT, seal_send_handle);
    if (ret) return ret;

    rc4_key.data = seal_recv_key->data;
    rc4_key.length = seal_recv_key->length;
    ret = RC4_INIT(&rc4_key, NTLM_CIPHER_DECRYPT, seal_recv_handle);
    if (ret) return ret;

    return 0;
}

int ntlm_seal_regen(struct ntlm_key *seal_key,
                    struct ntlm_rc4_handle **seal_handle,
                    uint32_t seq_num)
{
    struct ntlm_buffer payload;
    struct ntlm_buffer result;
    uint8_t inbuf[20];
    uint8_t outbuf[16];
    uint32_t le;
    int ret;

    RC4_FREE(seal_handle);

    memcpy(inbuf, seal_key->data, seal_key->length);
    le = htole32(seq_num);
    memcpy(&inbuf[16], &le, 4);

    payload.data = inbuf;
    payload.length = 20;
    result.data = outbuf;
    result.length = 16;

    ret = MD5_HASH(&payload, &result);
    if (ret) return ret;

    ret = RC4_INIT(&result, NTLM_CIPHER_ENCRYPT, seal_handle);
    return ret;
}

int ntlmv2_verify_nt_response(struct ntlm_buffer *nt_response,
                              struct ntlm_key *ntlmv2_key,
                              uint8_t server_chal[8])
{
    union wire_ntlm_response *nt_resp = NULL;
    struct ntlm_buffer key = { ntlmv2_key->data, ntlmv2_key->length };
    uint8_t proof[16];
    struct ntlm_buffer nt_proof = { proof, 16 };
    struct ntlm_buffer payload;
    int ret;

    if (nt_response->length < 24) return EINVAL;

    nt_resp = (union wire_ntlm_response *)nt_response->data;

    payload.length = 8;
    payload.data = server_chal;

    payload.length = nt_response->length - 8;
    payload.data = malloc(payload.length);
    if (!payload.data) return ENOMEM;
    memcpy(payload.data, server_chal, 8);
    memcpy(&payload.data[8], nt_resp->v2.cli_chal, payload.length - 8);

    ret = HMAC_MD5(&key, &payload, &nt_proof);

    if (ret) goto done;

    ret = EINVAL;
    if (memcmp(nt_resp->v2.resp, proof, 16) == 0) {
        ret = 0;
    }

done:
    safefree(payload.data);
    return ret;
}

int ntlmv2_verify_lm_response(struct ntlm_buffer *lm_response,
                              struct ntlm_key *ntlmv2_key,
                              uint8_t server_chal[8])
{
    struct ntlm_buffer key = { ntlmv2_key->data, ntlmv2_key->length };
    union wire_lm_response *lm_resp = NULL;
    uint8_t payload_buf[16];
    struct ntlm_buffer payload = { payload_buf, 16 };
    uint8_t proof[16];
    struct ntlm_buffer lm_proof = { proof, 16 };
    int ret;

    if (lm_response->length != 24) return EINVAL;

    /* now caluclate the LM Proof */
    lm_resp = (union wire_lm_response *)lm_response->data;

    memcpy(payload.data, server_chal, 8);
    memcpy(&payload.data[8], lm_resp->v2.cli_chal, 8);
    ret = HMAC_MD5(&key, &payload, &lm_proof);

    if (ret) return ret;

    if (memcmp(lm_resp->v2.resp, proof, 16) == 0) return 0;

    return EINVAL;
}

static int ntlmv2_sign(struct ntlm_key *sign_key, uint32_t seq_num,
                       struct ntlm_rc4_handle *handle, bool keyex,
                       struct ntlm_buffer *message,
                       struct ntlm_buffer *signature)
{
    uint32_t ver;
    struct ntlm_buffer key = { sign_key->data, sign_key->length };
    uint32_t le_seq;
    uint8_t le8seq[8];
    struct ntlm_buffer seq = { le8seq, 4 };
    struct ntlm_buffer *data[2];
    struct ntlm_iov iov;
    uint8_t hmac_sig[16];
    struct ntlm_buffer hmac = { hmac_sig, 16 };
    struct ntlm_buffer rc4buf;
    struct ntlm_buffer rc4res;
    int ret;

    if (signature->length != 16) {
        return EINVAL;
    }

    le_seq = htole32(seq_num);
    memcpy(seq.data, &le_seq, 4);
    data[0] = &seq;
    data[1] = message;
    iov.data = data;
    iov.num = 2;

    ret = HMAC_MD5_IOV(&key, &iov, &hmac);
    if (ret) return ret;

    /* put version */
    ver = htole32(NTLMSSP_MESSAGE_SIGNATURE_VERSION);
    memcpy(signature->data, &ver, 4);

    /* put actual MAC */
    if (keyex) {
        /* encrypt truncated hmac */
        rc4buf.data = hmac.data;
        rc4buf.length = 8;
        /* and put it in the middle of the output signature */
        rc4res.data = &signature->data[4];
        rc4res.length = 8;
        ret = RC4_UPDATE(handle, &rc4buf, &rc4res);
        if (ret) return ret;
    } else {
        memcpy(&signature->data[4], hmac.data, 8);
    }

    /* put used seq_num */
    memcpy(&signature->data[12], seq.data, 4);

    return 0;
}

int ntlm_sign(struct ntlm_key *sign_key, uint32_t seq_num,
              struct ntlm_rc4_handle *handle, uint32_t flags,
              struct ntlm_buffer *message, struct ntlm_buffer *signature)
{
    if ((flags & NTLMSSP_NEGOTIATE_EXTENDED_SESSIONSECURITY)
        && (flags & NTLMSSP_NEGOTIATE_SIGN)) {
        return ntlmv2_sign(sign_key, seq_num, handle,
                           (flags & NTLMSSP_NEGOTIATE_KEY_EXCH),
                           message, signature);
    } else if (flags & NTLMSSP_NEGOTIATE_SIGN) {
        /* FIXME: needs an implementation of CRC32 maybe use zlib ? */
    } else if (flags & NTLMSSP_NEGOTIATE_ALWAYS_SIGN) {
        uint32_t le_seq = htole32(seq_num);
        memcpy(signature->data, &le_seq, 4);
        memset(&signature->data[4], 0, 12);
        return 0;
    }

    return ENOTSUP;
}

int ntlm_seal(struct ntlm_rc4_handle *handle, uint32_t flags,
              struct ntlm_key *sign_key, uint32_t seq_num,
              struct ntlm_buffer *message, struct ntlm_buffer *output,
              struct ntlm_buffer *signature)
{
    int ret;

    if (!((flags & NTLMSSP_NEGOTIATE_EXTENDED_SESSIONSECURITY)
        && (flags & NTLMSSP_NEGOTIATE_SEAL))) {
        /* we only support v2 for now as we can't sign w/o session security
         * anyway */
        return ENOTSUP;
    }

    ret = RC4_UPDATE(handle, message, output);
    if (ret) return ret;

    return ntlmv2_sign(sign_key, seq_num, handle,
                       (flags & NTLMSSP_NEGOTIATE_KEY_EXCH),
                       message, signature);
}

int ntlm_unseal(struct ntlm_rc4_handle *handle, uint32_t flags,
                struct ntlm_key *sign_key, uint32_t seq_num,
                struct ntlm_buffer *message, struct ntlm_buffer *output,
                struct ntlm_buffer *signature)
{
    struct ntlm_buffer msg_buffer;
    int ret;

    if (!((flags & NTLMSSP_NEGOTIATE_EXTENDED_SESSIONSECURITY)
        && (flags & NTLMSSP_NEGOTIATE_SEAL))) {
        /* we only support v2 for now as we can't sign w/o session security
         * anyway */
        return ENOTSUP;
    }

    msg_buffer = *message;
    msg_buffer.length -= 16;

    ret = RC4_UPDATE(handle, &msg_buffer, output);
    if (ret) return ret;

    return ntlmv2_sign(sign_key, seq_num, handle,
                      (flags & NTLMSSP_NEGOTIATE_KEY_EXCH),
                      output, signature);
}