1 /* X.509 certificate parser
2 *
3 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
10 */
11
12 #define pr_fmt(fmt) "X.509: "fmt
13 #include <linux/kernel.h>
14 #include <linux/export.h>
15 #include <linux/slab.h>
16 #include <linux/err.h>
17 #include <linux/oid_registry.h>
18 #include <crypto/public_key.h>
19 #include "x509_parser.h"
20 #include "x509.asn1.h"
21 #include "x509_akid.asn1.h"
22
23 struct x509_parse_context {
24 struct x509_certificate *cert; /* Certificate being constructed */
25 unsigned long data; /* Start of data */
26 const void *cert_start; /* Start of cert content */
27 const void *key; /* Key data */
28 size_t key_size; /* Size of key data */
29 enum OID last_oid; /* Last OID encountered */
30 enum OID algo_oid; /* Algorithm OID */
31 unsigned char nr_mpi; /* Number of MPIs stored */
32 u8 o_size; /* Size of organizationName (O) */
33 u8 cn_size; /* Size of commonName (CN) */
34 u8 email_size; /* Size of emailAddress */
35 u16 o_offset; /* Offset of organizationName (O) */
36 u16 cn_offset; /* Offset of commonName (CN) */
37 u16 email_offset; /* Offset of emailAddress */
38 unsigned raw_akid_size;
39 const void *raw_akid; /* Raw authorityKeyId in ASN.1 */
40 const void *akid_raw_issuer; /* Raw directoryName in authorityKeyId */
41 unsigned akid_raw_issuer_size;
42 };
43
44 /*
45 * Free an X.509 certificate
46 */
x509_free_certificate(struct x509_certificate * cert)47 void x509_free_certificate(struct x509_certificate *cert)
48 {
49 if (cert) {
50 public_key_free(cert->pub);
51 public_key_signature_free(cert->sig);
52 kfree(cert->issuer);
53 kfree(cert->subject);
54 kfree(cert->id);
55 kfree(cert->skid);
56 kfree(cert);
57 }
58 }
59 EXPORT_SYMBOL_GPL(x509_free_certificate);
60
61 /*
62 * Parse an X.509 certificate
63 */
x509_cert_parse(const void * data,size_t datalen)64 struct x509_certificate *x509_cert_parse(const void *data, size_t datalen)
65 {
66 struct x509_certificate *cert;
67 struct x509_parse_context *ctx;
68 struct asymmetric_key_id *kid;
69 long ret;
70
71 ret = -ENOMEM;
72 cert = kzalloc(sizeof(struct x509_certificate), GFP_KERNEL);
73 if (!cert)
74 goto error_no_cert;
75 cert->pub = kzalloc(sizeof(struct public_key), GFP_KERNEL);
76 if (!cert->pub)
77 goto error_no_ctx;
78 cert->sig = kzalloc(sizeof(struct public_key_signature), GFP_KERNEL);
79 if (!cert->sig)
80 goto error_no_ctx;
81 ctx = kzalloc(sizeof(struct x509_parse_context), GFP_KERNEL);
82 if (!ctx)
83 goto error_no_ctx;
84
85 ctx->cert = cert;
86 ctx->data = (unsigned long)data;
87
88 /* Attempt to decode the certificate */
89 ret = asn1_ber_decoder(&x509_decoder, ctx, data, datalen);
90 if (ret < 0)
91 goto error_decode;
92
93 /* Decode the AuthorityKeyIdentifier */
94 if (ctx->raw_akid) {
95 pr_devel("AKID: %u %*phN\n",
96 ctx->raw_akid_size, ctx->raw_akid_size, ctx->raw_akid);
97 ret = asn1_ber_decoder(&x509_akid_decoder, ctx,
98 ctx->raw_akid, ctx->raw_akid_size);
99 if (ret < 0) {
100 pr_warn("Couldn't decode AuthKeyIdentifier\n");
101 goto error_decode;
102 }
103 }
104
105 ret = -ENOMEM;
106 cert->pub->key = kmemdup(ctx->key, ctx->key_size, GFP_KERNEL);
107 if (!cert->pub->key)
108 goto error_decode;
109
110 cert->pub->keylen = ctx->key_size;
111
112 /* Grab the signature bits */
113 ret = x509_get_sig_params(cert);
114 if (ret < 0)
115 goto error_decode;
116
117 /* Generate cert issuer + serial number key ID */
118 kid = asymmetric_key_generate_id(cert->raw_serial,
119 cert->raw_serial_size,
120 cert->raw_issuer,
121 cert->raw_issuer_size);
122 if (IS_ERR(kid)) {
123 ret = PTR_ERR(kid);
124 goto error_decode;
125 }
126 cert->id = kid;
127
128 /* Detect self-signed certificates */
129 ret = x509_check_for_self_signed(cert);
130 if (ret < 0)
131 goto error_decode;
132
133 kfree(ctx);
134 return cert;
135
136 error_decode:
137 kfree(ctx);
138 error_no_ctx:
139 x509_free_certificate(cert);
140 error_no_cert:
141 return ERR_PTR(ret);
142 }
143 EXPORT_SYMBOL_GPL(x509_cert_parse);
144
145 /*
146 * Note an OID when we find one for later processing when we know how
147 * to interpret it.
148 */
x509_note_OID(void * context,size_t hdrlen,unsigned char tag,const void * value,size_t vlen)149 int x509_note_OID(void *context, size_t hdrlen,
150 unsigned char tag,
151 const void *value, size_t vlen)
152 {
153 struct x509_parse_context *ctx = context;
154
155 ctx->last_oid = look_up_OID(value, vlen);
156 if (ctx->last_oid == OID__NR) {
157 char buffer[50];
158 sprint_oid(value, vlen, buffer, sizeof(buffer));
159 pr_debug("Unknown OID: [%lu] %s\n",
160 (unsigned long)value - ctx->data, buffer);
161 }
162 return 0;
163 }
164
165 /*
166 * Save the position of the TBS data so that we can check the signature over it
167 * later.
168 */
x509_note_tbs_certificate(void * context,size_t hdrlen,unsigned char tag,const void * value,size_t vlen)169 int x509_note_tbs_certificate(void *context, size_t hdrlen,
170 unsigned char tag,
171 const void *value, size_t vlen)
172 {
173 struct x509_parse_context *ctx = context;
174
175 pr_debug("x509_note_tbs_certificate(,%zu,%02x,%ld,%zu)!\n",
176 hdrlen, tag, (unsigned long)value - ctx->data, vlen);
177
178 ctx->cert->tbs = value - hdrlen;
179 ctx->cert->tbs_size = vlen + hdrlen;
180 return 0;
181 }
182
183 /*
184 * Record the public key algorithm
185 */
x509_note_pkey_algo(void * context,size_t hdrlen,unsigned char tag,const void * value,size_t vlen)186 int x509_note_pkey_algo(void *context, size_t hdrlen,
187 unsigned char tag,
188 const void *value, size_t vlen)
189 {
190 struct x509_parse_context *ctx = context;
191
192 pr_debug("PubKey Algo: %u\n", ctx->last_oid);
193
194 switch (ctx->last_oid) {
195 case OID_md2WithRSAEncryption:
196 case OID_md3WithRSAEncryption:
197 default:
198 return -ENOPKG; /* Unsupported combination */
199
200 case OID_md4WithRSAEncryption:
201 ctx->cert->sig->hash_algo = "md4";
202 ctx->cert->sig->pkey_algo = "rsa";
203 break;
204
205 case OID_sha1WithRSAEncryption:
206 ctx->cert->sig->hash_algo = "sha1";
207 ctx->cert->sig->pkey_algo = "rsa";
208 break;
209
210 case OID_sha256WithRSAEncryption:
211 ctx->cert->sig->hash_algo = "sha256";
212 ctx->cert->sig->pkey_algo = "rsa";
213 break;
214
215 case OID_sha384WithRSAEncryption:
216 ctx->cert->sig->hash_algo = "sha384";
217 ctx->cert->sig->pkey_algo = "rsa";
218 break;
219
220 case OID_sha512WithRSAEncryption:
221 ctx->cert->sig->hash_algo = "sha512";
222 ctx->cert->sig->pkey_algo = "rsa";
223 break;
224
225 case OID_sha224WithRSAEncryption:
226 ctx->cert->sig->hash_algo = "sha224";
227 ctx->cert->sig->pkey_algo = "rsa";
228 break;
229 }
230
231 ctx->algo_oid = ctx->last_oid;
232 return 0;
233 }
234
235 /*
236 * Note the whereabouts and type of the signature.
237 */
x509_note_signature(void * context,size_t hdrlen,unsigned char tag,const void * value,size_t vlen)238 int x509_note_signature(void *context, size_t hdrlen,
239 unsigned char tag,
240 const void *value, size_t vlen)
241 {
242 struct x509_parse_context *ctx = context;
243
244 pr_debug("Signature type: %u size %zu\n", ctx->last_oid, vlen);
245
246 if (ctx->last_oid != ctx->algo_oid) {
247 pr_warn("Got cert with pkey (%u) and sig (%u) algorithm OIDs\n",
248 ctx->algo_oid, ctx->last_oid);
249 return -EINVAL;
250 }
251
252 if (strcmp(ctx->cert->sig->pkey_algo, "rsa") == 0) {
253 /* Discard the BIT STRING metadata */
254 if (vlen < 1 || *(const u8 *)value != 0)
255 return -EBADMSG;
256
257 value++;
258 vlen--;
259 }
260
261 ctx->cert->raw_sig = value;
262 ctx->cert->raw_sig_size = vlen;
263 return 0;
264 }
265
266 /*
267 * Note the certificate serial number
268 */
x509_note_serial(void * context,size_t hdrlen,unsigned char tag,const void * value,size_t vlen)269 int x509_note_serial(void *context, size_t hdrlen,
270 unsigned char tag,
271 const void *value, size_t vlen)
272 {
273 struct x509_parse_context *ctx = context;
274 ctx->cert->raw_serial = value;
275 ctx->cert->raw_serial_size = vlen;
276 return 0;
277 }
278
279 /*
280 * Note some of the name segments from which we'll fabricate a name.
281 */
x509_extract_name_segment(void * context,size_t hdrlen,unsigned char tag,const void * value,size_t vlen)282 int x509_extract_name_segment(void *context, size_t hdrlen,
283 unsigned char tag,
284 const void *value, size_t vlen)
285 {
286 struct x509_parse_context *ctx = context;
287
288 switch (ctx->last_oid) {
289 case OID_commonName:
290 ctx->cn_size = vlen;
291 ctx->cn_offset = (unsigned long)value - ctx->data;
292 break;
293 case OID_organizationName:
294 ctx->o_size = vlen;
295 ctx->o_offset = (unsigned long)value - ctx->data;
296 break;
297 case OID_email_address:
298 ctx->email_size = vlen;
299 ctx->email_offset = (unsigned long)value - ctx->data;
300 break;
301 default:
302 break;
303 }
304
305 return 0;
306 }
307
308 /*
309 * Fabricate and save the issuer and subject names
310 */
x509_fabricate_name(struct x509_parse_context * ctx,size_t hdrlen,unsigned char tag,char ** _name,size_t vlen)311 static int x509_fabricate_name(struct x509_parse_context *ctx, size_t hdrlen,
312 unsigned char tag,
313 char **_name, size_t vlen)
314 {
315 const void *name, *data = (const void *)ctx->data;
316 size_t namesize;
317 char *buffer;
318
319 if (*_name)
320 return -EINVAL;
321
322 /* Empty name string if no material */
323 if (!ctx->cn_size && !ctx->o_size && !ctx->email_size) {
324 buffer = kmalloc(1, GFP_KERNEL);
325 if (!buffer)
326 return -ENOMEM;
327 buffer[0] = 0;
328 goto done;
329 }
330
331 if (ctx->cn_size && ctx->o_size) {
332 /* Consider combining O and CN, but use only the CN if it is
333 * prefixed by the O, or a significant portion thereof.
334 */
335 namesize = ctx->cn_size;
336 name = data + ctx->cn_offset;
337 if (ctx->cn_size >= ctx->o_size &&
338 memcmp(data + ctx->cn_offset, data + ctx->o_offset,
339 ctx->o_size) == 0)
340 goto single_component;
341 if (ctx->cn_size >= 7 &&
342 ctx->o_size >= 7 &&
343 memcmp(data + ctx->cn_offset, data + ctx->o_offset, 7) == 0)
344 goto single_component;
345
346 buffer = kmalloc(ctx->o_size + 2 + ctx->cn_size + 1,
347 GFP_KERNEL);
348 if (!buffer)
349 return -ENOMEM;
350
351 memcpy(buffer,
352 data + ctx->o_offset, ctx->o_size);
353 buffer[ctx->o_size + 0] = ':';
354 buffer[ctx->o_size + 1] = ' ';
355 memcpy(buffer + ctx->o_size + 2,
356 data + ctx->cn_offset, ctx->cn_size);
357 buffer[ctx->o_size + 2 + ctx->cn_size] = 0;
358 goto done;
359
360 } else if (ctx->cn_size) {
361 namesize = ctx->cn_size;
362 name = data + ctx->cn_offset;
363 } else if (ctx->o_size) {
364 namesize = ctx->o_size;
365 name = data + ctx->o_offset;
366 } else {
367 namesize = ctx->email_size;
368 name = data + ctx->email_offset;
369 }
370
371 single_component:
372 buffer = kmalloc(namesize + 1, GFP_KERNEL);
373 if (!buffer)
374 return -ENOMEM;
375 memcpy(buffer, name, namesize);
376 buffer[namesize] = 0;
377
378 done:
379 *_name = buffer;
380 ctx->cn_size = 0;
381 ctx->o_size = 0;
382 ctx->email_size = 0;
383 return 0;
384 }
385
x509_note_issuer(void * context,size_t hdrlen,unsigned char tag,const void * value,size_t vlen)386 int x509_note_issuer(void *context, size_t hdrlen,
387 unsigned char tag,
388 const void *value, size_t vlen)
389 {
390 struct x509_parse_context *ctx = context;
391 ctx->cert->raw_issuer = value;
392 ctx->cert->raw_issuer_size = vlen;
393 return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->issuer, vlen);
394 }
395
x509_note_subject(void * context,size_t hdrlen,unsigned char tag,const void * value,size_t vlen)396 int x509_note_subject(void *context, size_t hdrlen,
397 unsigned char tag,
398 const void *value, size_t vlen)
399 {
400 struct x509_parse_context *ctx = context;
401 ctx->cert->raw_subject = value;
402 ctx->cert->raw_subject_size = vlen;
403 return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->subject, vlen);
404 }
405
406 /*
407 * Extract the data for the public key algorithm
408 */
x509_extract_key_data(void * context,size_t hdrlen,unsigned char tag,const void * value,size_t vlen)409 int x509_extract_key_data(void *context, size_t hdrlen,
410 unsigned char tag,
411 const void *value, size_t vlen)
412 {
413 struct x509_parse_context *ctx = context;
414
415 if (ctx->last_oid != OID_rsaEncryption)
416 return -ENOPKG;
417
418 ctx->cert->pub->pkey_algo = "rsa";
419
420 /* Discard the BIT STRING metadata */
421 if (vlen < 1 || *(const u8 *)value != 0)
422 return -EBADMSG;
423 ctx->key = value + 1;
424 ctx->key_size = vlen - 1;
425 return 0;
426 }
427
428 /* The keyIdentifier in AuthorityKeyIdentifier SEQUENCE is tag(CONT,PRIM,0) */
429 #define SEQ_TAG_KEYID (ASN1_CONT << 6)
430
431 /*
432 * Process certificate extensions that are used to qualify the certificate.
433 */
x509_process_extension(void * context,size_t hdrlen,unsigned char tag,const void * value,size_t vlen)434 int x509_process_extension(void *context, size_t hdrlen,
435 unsigned char tag,
436 const void *value, size_t vlen)
437 {
438 struct x509_parse_context *ctx = context;
439 struct asymmetric_key_id *kid;
440 const unsigned char *v = value;
441
442 pr_debug("Extension: %u\n", ctx->last_oid);
443
444 if (ctx->last_oid == OID_subjectKeyIdentifier) {
445 /* Get hold of the key fingerprint */
446 if (ctx->cert->skid || vlen < 3)
447 return -EBADMSG;
448 if (v[0] != ASN1_OTS || v[1] != vlen - 2)
449 return -EBADMSG;
450 v += 2;
451 vlen -= 2;
452
453 ctx->cert->raw_skid_size = vlen;
454 ctx->cert->raw_skid = v;
455 kid = asymmetric_key_generate_id(v, vlen, "", 0);
456 if (IS_ERR(kid))
457 return PTR_ERR(kid);
458 ctx->cert->skid = kid;
459 pr_debug("subjkeyid %*phN\n", kid->len, kid->data);
460 return 0;
461 }
462
463 if (ctx->last_oid == OID_authorityKeyIdentifier) {
464 /* Get hold of the CA key fingerprint */
465 ctx->raw_akid = v;
466 ctx->raw_akid_size = vlen;
467 return 0;
468 }
469
470 return 0;
471 }
472
473 /**
474 * x509_decode_time - Decode an X.509 time ASN.1 object
475 * @_t: The time to fill in
476 * @hdrlen: The length of the object header
477 * @tag: The object tag
478 * @value: The object value
479 * @vlen: The size of the object value
480 *
481 * Decode an ASN.1 universal time or generalised time field into a struct the
482 * kernel can handle and check it for validity. The time is decoded thus:
483 *
484 * [RFC5280 §4.1.2.5]
485 * CAs conforming to this profile MUST always encode certificate validity
486 * dates through the year 2049 as UTCTime; certificate validity dates in
487 * 2050 or later MUST be encoded as GeneralizedTime. Conforming
488 * applications MUST be able to process validity dates that are encoded in
489 * either UTCTime or GeneralizedTime.
490 */
x509_decode_time(time64_t * _t,size_t hdrlen,unsigned char tag,const unsigned char * value,size_t vlen)491 int x509_decode_time(time64_t *_t, size_t hdrlen,
492 unsigned char tag,
493 const unsigned char *value, size_t vlen)
494 {
495 static const unsigned char month_lengths[] = { 31, 28, 31, 30, 31, 30,
496 31, 31, 30, 31, 30, 31 };
497 const unsigned char *p = value;
498 unsigned year, mon, day, hour, min, sec, mon_len;
499
500 #define dec2bin(X) ({ unsigned char x = (X) - '0'; if (x > 9) goto invalid_time; x; })
501 #define DD2bin(P) ({ unsigned x = dec2bin(P[0]) * 10 + dec2bin(P[1]); P += 2; x; })
502
503 if (tag == ASN1_UNITIM) {
504 /* UTCTime: YYMMDDHHMMSSZ */
505 if (vlen != 13)
506 goto unsupported_time;
507 year = DD2bin(p);
508 if (year >= 50)
509 year += 1900;
510 else
511 year += 2000;
512 } else if (tag == ASN1_GENTIM) {
513 /* GenTime: YYYYMMDDHHMMSSZ */
514 if (vlen != 15)
515 goto unsupported_time;
516 year = DD2bin(p) * 100 + DD2bin(p);
517 if (year >= 1950 && year <= 2049)
518 goto invalid_time;
519 } else {
520 goto unsupported_time;
521 }
522
523 mon = DD2bin(p);
524 day = DD2bin(p);
525 hour = DD2bin(p);
526 min = DD2bin(p);
527 sec = DD2bin(p);
528
529 if (*p != 'Z')
530 goto unsupported_time;
531
532 if (year < 1970 ||
533 mon < 1 || mon > 12)
534 goto invalid_time;
535
536 mon_len = month_lengths[mon - 1];
537 if (mon == 2) {
538 if (year % 4 == 0) {
539 mon_len = 29;
540 if (year % 100 == 0) {
541 mon_len = 28;
542 if (year % 400 == 0)
543 mon_len = 29;
544 }
545 }
546 }
547
548 if (day < 1 || day > mon_len ||
549 hour > 24 || /* ISO 8601 permits 24:00:00 as midnight tomorrow */
550 min > 59 ||
551 sec > 60) /* ISO 8601 permits leap seconds [X.680 46.3] */
552 goto invalid_time;
553
554 *_t = mktime64(year, mon, day, hour, min, sec);
555 return 0;
556
557 unsupported_time:
558 pr_debug("Got unsupported time [tag %02x]: '%*phN'\n",
559 tag, (int)vlen, value);
560 return -EBADMSG;
561 invalid_time:
562 pr_debug("Got invalid time [tag %02x]: '%*phN'\n",
563 tag, (int)vlen, value);
564 return -EBADMSG;
565 }
566 EXPORT_SYMBOL_GPL(x509_decode_time);
567
x509_note_not_before(void * context,size_t hdrlen,unsigned char tag,const void * value,size_t vlen)568 int x509_note_not_before(void *context, size_t hdrlen,
569 unsigned char tag,
570 const void *value, size_t vlen)
571 {
572 struct x509_parse_context *ctx = context;
573 return x509_decode_time(&ctx->cert->valid_from, hdrlen, tag, value, vlen);
574 }
575
x509_note_not_after(void * context,size_t hdrlen,unsigned char tag,const void * value,size_t vlen)576 int x509_note_not_after(void *context, size_t hdrlen,
577 unsigned char tag,
578 const void *value, size_t vlen)
579 {
580 struct x509_parse_context *ctx = context;
581 return x509_decode_time(&ctx->cert->valid_to, hdrlen, tag, value, vlen);
582 }
583
584 /*
585 * Note a key identifier-based AuthorityKeyIdentifier
586 */
x509_akid_note_kid(void * context,size_t hdrlen,unsigned char tag,const void * value,size_t vlen)587 int x509_akid_note_kid(void *context, size_t hdrlen,
588 unsigned char tag,
589 const void *value, size_t vlen)
590 {
591 struct x509_parse_context *ctx = context;
592 struct asymmetric_key_id *kid;
593
594 pr_debug("AKID: keyid: %*phN\n", (int)vlen, value);
595
596 if (ctx->cert->sig->auth_ids[1])
597 return 0;
598
599 kid = asymmetric_key_generate_id(value, vlen, "", 0);
600 if (IS_ERR(kid))
601 return PTR_ERR(kid);
602 pr_debug("authkeyid %*phN\n", kid->len, kid->data);
603 ctx->cert->sig->auth_ids[1] = kid;
604 return 0;
605 }
606
607 /*
608 * Note a directoryName in an AuthorityKeyIdentifier
609 */
x509_akid_note_name(void * context,size_t hdrlen,unsigned char tag,const void * value,size_t vlen)610 int x509_akid_note_name(void *context, size_t hdrlen,
611 unsigned char tag,
612 const void *value, size_t vlen)
613 {
614 struct x509_parse_context *ctx = context;
615
616 pr_debug("AKID: name: %*phN\n", (int)vlen, value);
617
618 ctx->akid_raw_issuer = value;
619 ctx->akid_raw_issuer_size = vlen;
620 return 0;
621 }
622
623 /*
624 * Note a serial number in an AuthorityKeyIdentifier
625 */
x509_akid_note_serial(void * context,size_t hdrlen,unsigned char tag,const void * value,size_t vlen)626 int x509_akid_note_serial(void *context, size_t hdrlen,
627 unsigned char tag,
628 const void *value, size_t vlen)
629 {
630 struct x509_parse_context *ctx = context;
631 struct asymmetric_key_id *kid;
632
633 pr_debug("AKID: serial: %*phN\n", (int)vlen, value);
634
635 if (!ctx->akid_raw_issuer || ctx->cert->sig->auth_ids[0])
636 return 0;
637
638 kid = asymmetric_key_generate_id(value,
639 vlen,
640 ctx->akid_raw_issuer,
641 ctx->akid_raw_issuer_size);
642 if (IS_ERR(kid))
643 return PTR_ERR(kid);
644
645 pr_debug("authkeyid %*phN\n", kid->len, kid->data);
646 ctx->cert->sig->auth_ids[0] = kid;
647 return 0;
648 }
649