summaryrefslogtreecommitdiff
path: root/axTLS/src/ssl/x509.c
blob: 116fa00bdb0d01aa43fcf62df3660b1af0c20e4c (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
/*
 * Copyright (c) 2007, Cameron Rich
 * 
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions are met:
 *
 * * Redistributions of source code must retain the above copyright notice, 
 *   this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright notice, 
 *   this list of conditions and the following disclaimer in the documentation 
 *   and/or other materials provided with the distribution.
 * * Neither the name of the axTLS project nor the names of its contributors 
 *   may be used to endorse or promote products derived from this software 
 *   without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * @file x509.c
 * 
 * Certificate processing.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include "os_port.h"
#include "crypto_misc.h"

#ifdef CONFIG_SSL_CERT_VERIFICATION
/**
 * Retrieve the signature from a certificate.
 */
static const uint8_t *get_signature(const uint8_t *asn1_sig, int *len)
{
    int offset = 0;
    const uint8_t *ptr = NULL;

    if (asn1_next_obj(asn1_sig, &offset, ASN1_SEQUENCE) < 0 || 
            asn1_skip_obj(asn1_sig, &offset, ASN1_SEQUENCE))
        goto end_get_sig;

    if (asn1_sig[offset++] != ASN1_OCTET_STRING)
        goto end_get_sig;
    *len = get_asn1_length(asn1_sig, &offset);
    ptr = &asn1_sig[offset];          /* all ok */

end_get_sig:
    return ptr;
}

#endif

/**
 * Construct a new x509 object.
 * @return 0 if ok. < 0 if there was a problem.
 */
int x509_new(const uint8_t *cert, int *len, X509_CTX **ctx)
{
    int begin_tbs, end_tbs;
    int ret = X509_NOT_OK, offset = 0, cert_size = 0;
    X509_CTX *x509_ctx;
    BI_CTX *bi_ctx;
    SHA1_CTX sha_ctx_fp;

    *ctx = (X509_CTX *)calloc(1, sizeof(X509_CTX));
    x509_ctx = *ctx;

    /* get the certificate size */
    asn1_skip_obj(cert, &cert_size, ASN1_SEQUENCE); 

    if (asn1_next_obj(cert, &offset, ASN1_SEQUENCE) < 0)
        goto end_cert;

    begin_tbs = offset;         /* start of the tbs */
    end_tbs = begin_tbs;        /* work out the end of the tbs */
    asn1_skip_obj(cert, &end_tbs, ASN1_SEQUENCE);

    if (asn1_next_obj(cert, &offset, ASN1_SEQUENCE) < 0)
        goto end_cert;

    if (cert[offset] == ASN1_EXPLICIT_TAG)   /* optional version */
    {
        if (asn1_version(cert, &offset, x509_ctx))
            goto end_cert;
    }

    if (asn1_skip_obj(cert, &offset, ASN1_INTEGER) || /* serial number */ 
            asn1_next_obj(cert, &offset, ASN1_SEQUENCE) < 0)
        goto end_cert;

    /* make sure the signature is ok */
    if (asn1_signature_type(cert, &offset, x509_ctx))
    {
        ret = X509_VFY_ERROR_UNSUPPORTED_DIGEST;
        goto end_cert;
    }

    if (asn1_name(cert, &offset, x509_ctx->ca_cert_dn) || 
            asn1_validity(cert, &offset, x509_ctx) ||
            asn1_name(cert, &offset, x509_ctx->cert_dn) ||
            asn1_public_key(cert, &offset, x509_ctx))
    {
        goto end_cert;
    }

    bi_ctx = x509_ctx->rsa_ctx->bi_ctx;

    SHA1_Init(&sha_ctx_fp);
    SHA1_Update(&sha_ctx_fp, cert, cert_size);
    SHA1_Final(x509_ctx->sha1_fingerprint, &sha_ctx_fp);

#ifdef CONFIG_SSL_CERT_VERIFICATION /* only care if doing verification */
    /* use the appropriate signature algorithm (SHA1/MD5/MD2) */
    if (x509_ctx->sig_type == SIG_TYPE_MD5)
    {
        MD5_CTX md5_ctx;
        uint8_t md5_dgst[MD5_SIZE];
        MD5_Init(&md5_ctx);
        MD5_Update(&md5_ctx, &cert[begin_tbs], end_tbs-begin_tbs);
        MD5_Final(md5_dgst, &md5_ctx);
        x509_ctx->digest = bi_import(bi_ctx, md5_dgst, MD5_SIZE);
    }
    else if (x509_ctx->sig_type == SIG_TYPE_SHA1)
    {
        SHA1_CTX sha_ctx;
        uint8_t sha_dgst[SHA1_SIZE];
        SHA1_Init(&sha_ctx);
        SHA1_Update(&sha_ctx, &cert[begin_tbs], end_tbs-begin_tbs);
        SHA1_Final(sha_dgst, &sha_ctx);
        x509_ctx->digest = bi_import(bi_ctx, sha_dgst, SHA1_SIZE);
    }
    else if (x509_ctx->sig_type == SIG_TYPE_MD2)
    {
        MD2_CTX md2_ctx;
        uint8_t md2_dgst[MD2_SIZE];
        MD2_Init(&md2_ctx);
        MD2_Update(&md2_ctx, &cert[begin_tbs], end_tbs-begin_tbs);
        MD2_Final(md2_dgst, &md2_ctx);
        x509_ctx->digest = bi_import(bi_ctx, md2_dgst, MD2_SIZE);
    }

    if (cert[offset] == ASN1_V3_DATA)
    {
        int suboffset;

        ++offset;
        get_asn1_length(cert, &offset);

        if ((suboffset = asn1_find_subjectaltname(cert, offset)) > 0)
        {
            if (asn1_next_obj(cert, &suboffset, ASN1_OCTET_STRING) > 0)
            {
                int altlen;

                if ((altlen = asn1_next_obj(cert, 
                                            &suboffset, ASN1_SEQUENCE)) > 0)
                {
                    int endalt = suboffset + altlen;
                    int totalnames = 0;

                    while (suboffset < endalt)
                    {
                        int type = cert[suboffset++];
                        int dnslen = get_asn1_length(cert, &suboffset);

                        if (type == ASN1_CONTEXT_DNSNAME)
                        {
                            x509_ctx->subject_alt_dnsnames = (char**)
                                    realloc(x509_ctx->subject_alt_dnsnames, 
                                       (totalnames + 2) * sizeof(char*));
                            x509_ctx->subject_alt_dnsnames[totalnames] = 
                                    (char*)malloc(dnslen + 1);
                            x509_ctx->subject_alt_dnsnames[totalnames+1] = NULL;
                            memcpy(x509_ctx->subject_alt_dnsnames[totalnames], 
                                    cert + suboffset, dnslen);
                            x509_ctx->subject_alt_dnsnames[
                                    totalnames][dnslen] = 0;
                            ++totalnames;
                        }

                        suboffset += dnslen;
                    }
                }
            }
        }
    }

    offset = end_tbs;   /* skip the rest of v3 data */
    if (asn1_skip_obj(cert, &offset, ASN1_SEQUENCE) || 
            asn1_signature(cert, &offset, x509_ctx))
        goto end_cert;
#endif
    ret = X509_OK;
end_cert:
    if (len)
    {
        *len = cert_size;
    }

    if (ret)
    {
#ifdef CONFIG_SSL_FULL_MODE
        printf("Error: Invalid X509 ASN.1 file (%s)\n",
                        x509_display_error(ret));
#endif
        x509_free(x509_ctx);
        *ctx = NULL;
    }

    return ret;
}

/**
 * Free an X.509 object's resources.
 */
void x509_free(X509_CTX *x509_ctx)
{
    X509_CTX *next;
    int i;

    if (x509_ctx == NULL)       /* if already null, then don't bother */
        return;

    for (i = 0; i < X509_NUM_DN_TYPES; i++)
    {
        free(x509_ctx->ca_cert_dn[i]);
        free(x509_ctx->cert_dn[i]);
    }

    free(x509_ctx->signature);

#ifdef CONFIG_SSL_CERT_VERIFICATION 
    if (x509_ctx->digest)
    {
        bi_free(x509_ctx->rsa_ctx->bi_ctx, x509_ctx->digest);
    }

    if (x509_ctx->subject_alt_dnsnames)
    {
        for (i = 0; x509_ctx->subject_alt_dnsnames[i]; ++i)
            free(x509_ctx->subject_alt_dnsnames[i]);

        free(x509_ctx->subject_alt_dnsnames);
    }
#endif

    RSA_free(x509_ctx->rsa_ctx);
    next = x509_ctx->next;
    free(x509_ctx);
    x509_free(next);        /* clear the chain */
}

#ifdef CONFIG_SSL_CERT_VERIFICATION
/**
 * Take a signature and decrypt it.
 */
static bigint *sig_verify(BI_CTX *ctx, const uint8_t *sig, int sig_len,
        bigint *modulus, bigint *pub_exp)
{
    int i, size;
    bigint *decrypted_bi, *dat_bi;
    bigint *bir = NULL;
    uint8_t *block = (uint8_t *)alloca(sig_len);

    /* decrypt */
    dat_bi = bi_import(ctx, sig, sig_len);
    ctx->mod_offset = BIGINT_M_OFFSET;

    /* convert to a normal block */
    decrypted_bi = bi_mod_power2(ctx, dat_bi, modulus, pub_exp);

    bi_export(ctx, decrypted_bi, block, sig_len);
    ctx->mod_offset = BIGINT_M_OFFSET;

    i = 10; /* start at the first possible non-padded byte */
    while (block[i++] && i < sig_len);
    size = sig_len - i;

    /* get only the bit we want */
    if (size > 0)
    {
        int len;
        const uint8_t *sig_ptr = get_signature(&block[i], &len);

        if (sig_ptr)
        {
            bir = bi_import(ctx, sig_ptr, len);
        }
    }

    /* save a few bytes of memory */
    bi_clear_cache(ctx);
    return bir;
}

/**
 * Do some basic checks on the certificate chain.
 *
 * Certificate verification consists of a number of checks:
 * - The date of the certificate is after the start date.
 * - The date of the certificate is before the finish date.
 * - A root certificate exists in the certificate store.
 * - That the certificate(s) are not self-signed.
 * - The certificate chain is valid.
 * - The signature of the certificate is valid.
 */
int x509_verify(const CA_CERT_CTX *ca_cert_ctx, const X509_CTX *cert) 
{
    int ret = X509_OK, i = 0;
    bigint *cert_sig;
    X509_CTX *next_cert = NULL;
    BI_CTX *ctx = NULL;
    bigint *mod = NULL, *expn = NULL;
    int match_ca_cert = 0;
    struct timeval tv;
    uint8_t is_self_signed = 0;

    if (cert == NULL)
    {
        ret = X509_VFY_ERROR_NO_TRUSTED_CERT;       
        goto end_verify;
    }

    /* a self-signed certificate that is not in the CA store - use this 
       to check the signature */
    if (asn1_compare_dn(cert->ca_cert_dn, cert->cert_dn) == 0)
    {
        is_self_signed = 1;
        ctx = cert->rsa_ctx->bi_ctx;
        mod = cert->rsa_ctx->m;
        expn = cert->rsa_ctx->e;
    }

    gettimeofday(&tv, NULL);

    /* check the not before date */
    if (tv.tv_sec < cert->not_before)
    {
        ret = X509_VFY_ERROR_NOT_YET_VALID;
        goto end_verify;
    }

    /* check the not after date */
    if (tv.tv_sec > cert->not_after)
    {
        ret = X509_VFY_ERROR_EXPIRED;
        goto end_verify;
    }

    next_cert = cert->next;

    /* last cert in the chain - look for a trusted cert */
    if (next_cert == NULL)
    {
       if (ca_cert_ctx != NULL) 
       {
            /* go thu the CA store */
            while (i < CONFIG_X509_MAX_CA_CERTS && ca_cert_ctx->cert[i])
            {
                if (asn1_compare_dn(cert->ca_cert_dn,
                                            ca_cert_ctx->cert[i]->cert_dn) == 0)
                {
                    /* use this CA certificate for signature verification */
                    match_ca_cert = 1;
                    ctx = ca_cert_ctx->cert[i]->rsa_ctx->bi_ctx;
                    mod = ca_cert_ctx->cert[i]->rsa_ctx->m;
                    expn = ca_cert_ctx->cert[i]->rsa_ctx->e;
                    break;
                }

                i++;
            }
        }

        /* couldn't find a trusted cert (& let self-signed errors 
           be returned) */
        if (!match_ca_cert && !is_self_signed)
        {
            ret = X509_VFY_ERROR_NO_TRUSTED_CERT;       
            goto end_verify;
        }
    }
    else if (asn1_compare_dn(cert->ca_cert_dn, next_cert->cert_dn) != 0)
    {
        /* check the chain */
        ret = X509_VFY_ERROR_INVALID_CHAIN;
        goto end_verify;
    }
    else /* use the next certificate in the chain for signature verify */
    {
        ctx = next_cert->rsa_ctx->bi_ctx;
        mod = next_cert->rsa_ctx->m;
        expn = next_cert->rsa_ctx->e;
    }

    /* cert is self signed */
    if (!match_ca_cert && is_self_signed)
    {
        ret = X509_VFY_ERROR_SELF_SIGNED;
        goto end_verify;
    }

    /* check the signature */
    cert_sig = sig_verify(ctx, cert->signature, cert->sig_len, 
                        bi_clone(ctx, mod), bi_clone(ctx, expn));

    if (cert_sig && cert->digest)
    {
        if (bi_compare(cert_sig, cert->digest) != 0)
            ret = X509_VFY_ERROR_BAD_SIGNATURE;


        bi_free(ctx, cert_sig);
    }
    else
    {
        ret = X509_VFY_ERROR_BAD_SIGNATURE;
    }

    if (ret)
        goto end_verify;

    /* go down the certificate chain using recursion. */
    if (next_cert != NULL)
    {
        ret = x509_verify(ca_cert_ctx, next_cert);
    }

end_verify:
    return ret;
}
#endif

#if defined (CONFIG_SSL_FULL_MODE)
/**
 * Used for diagnostics.
 */
static const char *not_part_of_cert = "<Not Part Of Certificate>";
void x509_print(const X509_CTX *cert, CA_CERT_CTX *ca_cert_ctx) 
{
    if (cert == NULL)
        return;

    printf("=== CERTIFICATE ISSUED TO ===\n");
    printf("Common Name (CN):\t\t");
    printf("%s\n", cert->cert_dn[X509_COMMON_NAME] ?
                    cert->cert_dn[X509_COMMON_NAME] : not_part_of_cert);

    printf("Organization (O):\t\t");
    printf("%s\n", cert->cert_dn[X509_ORGANIZATION] ?
        cert->cert_dn[X509_ORGANIZATION] : not_part_of_cert);

    printf("Organizational Unit (OU):\t");
    printf("%s\n", cert->cert_dn[X509_ORGANIZATIONAL_UNIT] ?
        cert->cert_dn[X509_ORGANIZATIONAL_UNIT] : not_part_of_cert);

    printf("=== CERTIFICATE ISSUED BY ===\n");
    printf("Common Name (CN):\t\t");
    printf("%s\n", cert->ca_cert_dn[X509_COMMON_NAME] ?
                    cert->ca_cert_dn[X509_COMMON_NAME] : not_part_of_cert);

    printf("Organization (O):\t\t");
    printf("%s\n", cert->ca_cert_dn[X509_ORGANIZATION] ?
        cert->ca_cert_dn[X509_ORGANIZATION] : not_part_of_cert);

    printf("Organizational Unit (OU):\t");
    printf("%s\n", cert->ca_cert_dn[X509_ORGANIZATIONAL_UNIT] ?
        cert->ca_cert_dn[X509_ORGANIZATIONAL_UNIT] : not_part_of_cert);

    printf("Not Before:\t\t\t%s", ctime(&cert->not_before));
    printf("Not After:\t\t\t%s", ctime(&cert->not_after));
    printf("RSA bitsize:\t\t\t%d\n", cert->rsa_ctx->num_octets*8);
    printf("Sig Type:\t\t\t");
    switch (cert->sig_type)
    {
        case SIG_TYPE_MD5:
            printf("MD5\n");
            break;
        case SIG_TYPE_SHA1:
            printf("SHA1\n");
            break;
        case SIG_TYPE_MD2:
            printf("MD2\n");
            break;
        default:
            printf("Unrecognized: %d\n", cert->sig_type);
            break;
    }

    if (ca_cert_ctx)
    {
        printf("Verify:\t\t\t\t%s\n",
                x509_display_error(x509_verify(ca_cert_ctx, cert)));
    }

#if 0
    print_blob("Signature", cert->signature, cert->sig_len);
    bi_print("Modulus", cert->rsa_ctx->m);
    bi_print("Pub Exp", cert->rsa_ctx->e);
#endif

    if (ca_cert_ctx)
    {
        x509_print(cert->next, ca_cert_ctx);
    }

    TTY_FLUSH();
}

const char * x509_display_error(int error)
{
    switch (error)
    {
        case X509_OK:
            return "Certificate verify successful";

        case X509_NOT_OK:
            return "X509 not ok";

        case X509_VFY_ERROR_NO_TRUSTED_CERT:
            return "No trusted cert is available";

        case X509_VFY_ERROR_BAD_SIGNATURE:
            return "Bad signature";

        case X509_VFY_ERROR_NOT_YET_VALID:
            return "Cert is not yet valid";

        case X509_VFY_ERROR_EXPIRED:
            return "Cert has expired";

        case X509_VFY_ERROR_SELF_SIGNED:
            return "Cert is self-signed";

        case X509_VFY_ERROR_INVALID_CHAIN:
            return "Chain is invalid (check order of certs)";

        case X509_VFY_ERROR_UNSUPPORTED_DIGEST:
            return "Unsupported digest";

        case X509_INVALID_PRIV_KEY:
            return "Invalid private key";

        default:
            return "Unknown";
    }
}
#endif      /* CONFIG_SSL_FULL_MODE */