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David Howellsc26fd692012-09-24 17:11:48 +01001/* 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/slab.h>
15#include <linux/err.h>
16#include <linux/oid_registry.h>
17#include "public_key.h"
18#include "x509_parser.h"
19#include "x509-asn1.h"
20#include "x509_rsakey-asn1.h"
21
22struct x509_parse_context {
23 struct x509_certificate *cert; /* Certificate being constructed */
24 unsigned long data; /* Start of data */
25 const void *cert_start; /* Start of cert content */
26 const void *key; /* Key data */
27 size_t key_size; /* Size of key data */
28 enum OID last_oid; /* Last OID encountered */
29 enum OID algo_oid; /* Algorithm OID */
30 unsigned char nr_mpi; /* Number of MPIs stored */
31 u8 o_size; /* Size of organizationName (O) */
32 u8 cn_size; /* Size of commonName (CN) */
33 u8 email_size; /* Size of emailAddress */
34 u16 o_offset; /* Offset of organizationName (O) */
35 u16 cn_offset; /* Offset of commonName (CN) */
36 u16 email_offset; /* Offset of emailAddress */
37};
38
39/*
40 * Free an X.509 certificate
41 */
42void x509_free_certificate(struct x509_certificate *cert)
43{
44 if (cert) {
45 public_key_destroy(cert->pub);
46 kfree(cert->issuer);
47 kfree(cert->subject);
48 kfree(cert->fingerprint);
49 kfree(cert->authority);
David Howellsb426beb2013-08-30 16:18:02 +010050 kfree(cert->sig.digest);
51 mpi_free(cert->sig.rsa.s);
David Howellsc26fd692012-09-24 17:11:48 +010052 kfree(cert);
53 }
54}
55
56/*
57 * Parse an X.509 certificate
58 */
59struct x509_certificate *x509_cert_parse(const void *data, size_t datalen)
60{
61 struct x509_certificate *cert;
62 struct x509_parse_context *ctx;
63 long ret;
64
65 ret = -ENOMEM;
66 cert = kzalloc(sizeof(struct x509_certificate), GFP_KERNEL);
67 if (!cert)
68 goto error_no_cert;
69 cert->pub = kzalloc(sizeof(struct public_key), GFP_KERNEL);
70 if (!cert->pub)
71 goto error_no_ctx;
72 ctx = kzalloc(sizeof(struct x509_parse_context), GFP_KERNEL);
73 if (!ctx)
74 goto error_no_ctx;
75
76 ctx->cert = cert;
77 ctx->data = (unsigned long)data;
78
79 /* Attempt to decode the certificate */
80 ret = asn1_ber_decoder(&x509_decoder, ctx, data, datalen);
81 if (ret < 0)
82 goto error_decode;
83
84 /* Decode the public key */
85 ret = asn1_ber_decoder(&x509_rsakey_decoder, ctx,
86 ctx->key, ctx->key_size);
87 if (ret < 0)
88 goto error_decode;
89
90 kfree(ctx);
91 return cert;
92
93error_decode:
94 kfree(ctx);
95error_no_ctx:
96 x509_free_certificate(cert);
97error_no_cert:
98 return ERR_PTR(ret);
99}
100
101/*
102 * Note an OID when we find one for later processing when we know how
103 * to interpret it.
104 */
105int x509_note_OID(void *context, size_t hdrlen,
106 unsigned char tag,
107 const void *value, size_t vlen)
108{
109 struct x509_parse_context *ctx = context;
110
111 ctx->last_oid = look_up_OID(value, vlen);
112 if (ctx->last_oid == OID__NR) {
113 char buffer[50];
114 sprint_oid(value, vlen, buffer, sizeof(buffer));
Randy Dunlapcf754462012-10-03 16:04:46 -0700115 pr_debug("Unknown OID: [%lu] %s\n",
David Howellsc26fd692012-09-24 17:11:48 +0100116 (unsigned long)value - ctx->data, buffer);
117 }
118 return 0;
119}
120
121/*
122 * Save the position of the TBS data so that we can check the signature over it
123 * later.
124 */
125int x509_note_tbs_certificate(void *context, size_t hdrlen,
126 unsigned char tag,
127 const void *value, size_t vlen)
128{
129 struct x509_parse_context *ctx = context;
130
131 pr_debug("x509_note_tbs_certificate(,%zu,%02x,%ld,%zu)!\n",
132 hdrlen, tag, (unsigned long)value - ctx->data, vlen);
133
134 ctx->cert->tbs = value - hdrlen;
135 ctx->cert->tbs_size = vlen + hdrlen;
136 return 0;
137}
138
139/*
140 * Record the public key algorithm
141 */
142int x509_note_pkey_algo(void *context, size_t hdrlen,
143 unsigned char tag,
144 const void *value, size_t vlen)
145{
146 struct x509_parse_context *ctx = context;
147
148 pr_debug("PubKey Algo: %u\n", ctx->last_oid);
149
150 switch (ctx->last_oid) {
151 case OID_md2WithRSAEncryption:
152 case OID_md3WithRSAEncryption:
153 default:
154 return -ENOPKG; /* Unsupported combination */
155
156 case OID_md4WithRSAEncryption:
Dmitry Kasatkin3fe78ca2013-05-06 15:58:15 +0300157 ctx->cert->sig.pkey_hash_algo = HASH_ALGO_MD5;
David Howellsb426beb2013-08-30 16:18:02 +0100158 ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
David Howellsc26fd692012-09-24 17:11:48 +0100159 break;
160
161 case OID_sha1WithRSAEncryption:
Dmitry Kasatkin3fe78ca2013-05-06 15:58:15 +0300162 ctx->cert->sig.pkey_hash_algo = HASH_ALGO_SHA1;
David Howellsb426beb2013-08-30 16:18:02 +0100163 ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
David Howellsc26fd692012-09-24 17:11:48 +0100164 break;
165
166 case OID_sha256WithRSAEncryption:
Dmitry Kasatkin3fe78ca2013-05-06 15:58:15 +0300167 ctx->cert->sig.pkey_hash_algo = HASH_ALGO_SHA256;
David Howellsb426beb2013-08-30 16:18:02 +0100168 ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
David Howellsc26fd692012-09-24 17:11:48 +0100169 break;
170
171 case OID_sha384WithRSAEncryption:
Dmitry Kasatkin3fe78ca2013-05-06 15:58:15 +0300172 ctx->cert->sig.pkey_hash_algo = HASH_ALGO_SHA384;
David Howellsb426beb2013-08-30 16:18:02 +0100173 ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
David Howellsc26fd692012-09-24 17:11:48 +0100174 break;
175
176 case OID_sha512WithRSAEncryption:
Dmitry Kasatkin3fe78ca2013-05-06 15:58:15 +0300177 ctx->cert->sig.pkey_hash_algo = HASH_ALGO_SHA512;
David Howellsb426beb2013-08-30 16:18:02 +0100178 ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
David Howellsc26fd692012-09-24 17:11:48 +0100179 break;
180
181 case OID_sha224WithRSAEncryption:
Dmitry Kasatkin3fe78ca2013-05-06 15:58:15 +0300182 ctx->cert->sig.pkey_hash_algo = HASH_ALGO_SHA224;
David Howellsb426beb2013-08-30 16:18:02 +0100183 ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
David Howellsc26fd692012-09-24 17:11:48 +0100184 break;
185 }
186
187 ctx->algo_oid = ctx->last_oid;
188 return 0;
189}
190
191/*
192 * Note the whereabouts and type of the signature.
193 */
194int x509_note_signature(void *context, size_t hdrlen,
195 unsigned char tag,
196 const void *value, size_t vlen)
197{
198 struct x509_parse_context *ctx = context;
199
200 pr_debug("Signature type: %u size %zu\n", ctx->last_oid, vlen);
201
202 if (ctx->last_oid != ctx->algo_oid) {
203 pr_warn("Got cert with pkey (%u) and sig (%u) algorithm OIDs\n",
204 ctx->algo_oid, ctx->last_oid);
205 return -EINVAL;
206 }
207
David Howellsb426beb2013-08-30 16:18:02 +0100208 ctx->cert->raw_sig = value;
209 ctx->cert->raw_sig_size = vlen;
David Howellsc26fd692012-09-24 17:11:48 +0100210 return 0;
211}
212
213/*
214 * Note some of the name segments from which we'll fabricate a name.
215 */
216int x509_extract_name_segment(void *context, size_t hdrlen,
217 unsigned char tag,
218 const void *value, size_t vlen)
219{
220 struct x509_parse_context *ctx = context;
221
222 switch (ctx->last_oid) {
223 case OID_commonName:
224 ctx->cn_size = vlen;
225 ctx->cn_offset = (unsigned long)value - ctx->data;
226 break;
227 case OID_organizationName:
228 ctx->o_size = vlen;
229 ctx->o_offset = (unsigned long)value - ctx->data;
230 break;
231 case OID_email_address:
232 ctx->email_size = vlen;
233 ctx->email_offset = (unsigned long)value - ctx->data;
234 break;
235 default:
236 break;
237 }
238
239 return 0;
240}
241
242/*
243 * Fabricate and save the issuer and subject names
244 */
245static int x509_fabricate_name(struct x509_parse_context *ctx, size_t hdrlen,
246 unsigned char tag,
247 char **_name, size_t vlen)
248{
249 const void *name, *data = (const void *)ctx->data;
250 size_t namesize;
251 char *buffer;
252
253 if (*_name)
254 return -EINVAL;
255
256 /* Empty name string if no material */
257 if (!ctx->cn_size && !ctx->o_size && !ctx->email_size) {
258 buffer = kmalloc(1, GFP_KERNEL);
259 if (!buffer)
260 return -ENOMEM;
261 buffer[0] = 0;
262 goto done;
263 }
264
265 if (ctx->cn_size && ctx->o_size) {
266 /* Consider combining O and CN, but use only the CN if it is
267 * prefixed by the O, or a significant portion thereof.
268 */
269 namesize = ctx->cn_size;
270 name = data + ctx->cn_offset;
271 if (ctx->cn_size >= ctx->o_size &&
272 memcmp(data + ctx->cn_offset, data + ctx->o_offset,
273 ctx->o_size) == 0)
274 goto single_component;
275 if (ctx->cn_size >= 7 &&
276 ctx->o_size >= 7 &&
277 memcmp(data + ctx->cn_offset, data + ctx->o_offset, 7) == 0)
278 goto single_component;
279
280 buffer = kmalloc(ctx->o_size + 2 + ctx->cn_size + 1,
281 GFP_KERNEL);
282 if (!buffer)
283 return -ENOMEM;
284
285 memcpy(buffer,
286 data + ctx->o_offset, ctx->o_size);
287 buffer[ctx->o_size + 0] = ':';
288 buffer[ctx->o_size + 1] = ' ';
289 memcpy(buffer + ctx->o_size + 2,
290 data + ctx->cn_offset, ctx->cn_size);
291 buffer[ctx->o_size + 2 + ctx->cn_size] = 0;
292 goto done;
293
294 } else if (ctx->cn_size) {
295 namesize = ctx->cn_size;
296 name = data + ctx->cn_offset;
297 } else if (ctx->o_size) {
298 namesize = ctx->o_size;
299 name = data + ctx->o_offset;
300 } else {
301 namesize = ctx->email_size;
302 name = data + ctx->email_offset;
303 }
304
305single_component:
306 buffer = kmalloc(namesize + 1, GFP_KERNEL);
307 if (!buffer)
308 return -ENOMEM;
309 memcpy(buffer, name, namesize);
310 buffer[namesize] = 0;
311
312done:
313 *_name = buffer;
314 ctx->cn_size = 0;
315 ctx->o_size = 0;
316 ctx->email_size = 0;
317 return 0;
318}
319
320int x509_note_issuer(void *context, size_t hdrlen,
321 unsigned char tag,
322 const void *value, size_t vlen)
323{
324 struct x509_parse_context *ctx = context;
325 return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->issuer, vlen);
326}
327
328int x509_note_subject(void *context, size_t hdrlen,
329 unsigned char tag,
330 const void *value, size_t vlen)
331{
332 struct x509_parse_context *ctx = context;
333 return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->subject, vlen);
334}
335
336/*
337 * Extract the data for the public key algorithm
338 */
339int x509_extract_key_data(void *context, size_t hdrlen,
340 unsigned char tag,
341 const void *value, size_t vlen)
342{
343 struct x509_parse_context *ctx = context;
344
345 if (ctx->last_oid != OID_rsaEncryption)
346 return -ENOPKG;
347
David Howells67f7d60b2013-08-30 16:15:24 +0100348 ctx->cert->pub->pkey_algo = PKEY_ALGO_RSA;
349
350 /* Discard the BIT STRING metadata */
David Howellsc26fd692012-09-24 17:11:48 +0100351 ctx->key = value + 1;
352 ctx->key_size = vlen - 1;
353 return 0;
354}
355
356/*
357 * Extract a RSA public key value
358 */
359int rsa_extract_mpi(void *context, size_t hdrlen,
360 unsigned char tag,
361 const void *value, size_t vlen)
362{
363 struct x509_parse_context *ctx = context;
364 MPI mpi;
365
366 if (ctx->nr_mpi >= ARRAY_SIZE(ctx->cert->pub->mpi)) {
367 pr_err("Too many public key MPIs in certificate\n");
368 return -EBADMSG;
369 }
370
371 mpi = mpi_read_raw_data(value, vlen);
372 if (!mpi)
373 return -ENOMEM;
374
375 ctx->cert->pub->mpi[ctx->nr_mpi++] = mpi;
376 return 0;
377}
378
Chun-Yi Lee04b00bd2013-04-22 10:56:55 +0930379/* The keyIdentifier in AuthorityKeyIdentifier SEQUENCE is tag(CONT,PRIM,0) */
380#define SEQ_TAG_KEYID (ASN1_CONT << 6)
381
David Howellsc26fd692012-09-24 17:11:48 +0100382/*
383 * Process certificate extensions that are used to qualify the certificate.
384 */
385int x509_process_extension(void *context, size_t hdrlen,
386 unsigned char tag,
387 const void *value, size_t vlen)
388{
389 struct x509_parse_context *ctx = context;
390 const unsigned char *v = value;
391 char *f;
392 int i;
393
394 pr_debug("Extension: %u\n", ctx->last_oid);
395
396 if (ctx->last_oid == OID_subjectKeyIdentifier) {
397 /* Get hold of the key fingerprint */
398 if (vlen < 3)
399 return -EBADMSG;
400 if (v[0] != ASN1_OTS || v[1] != vlen - 2)
401 return -EBADMSG;
402 v += 2;
403 vlen -= 2;
404
405 f = kmalloc(vlen * 2 + 1, GFP_KERNEL);
406 if (!f)
407 return -ENOMEM;
408 for (i = 0; i < vlen; i++)
409 sprintf(f + i * 2, "%02x", v[i]);
410 pr_debug("fingerprint %s\n", f);
411 ctx->cert->fingerprint = f;
412 return 0;
413 }
414
415 if (ctx->last_oid == OID_authorityKeyIdentifier) {
Chun-Yi Lee04b00bd2013-04-22 10:56:55 +0930416 size_t key_len;
417
David Howellsc26fd692012-09-24 17:11:48 +0100418 /* Get hold of the CA key fingerprint */
419 if (vlen < 5)
420 return -EBADMSG;
David Howellsc26fd692012-09-24 17:11:48 +0100421
Chun-Yi Lee04b00bd2013-04-22 10:56:55 +0930422 /* Authority Key Identifier must be a Constructed SEQUENCE */
423 if (v[0] != (ASN1_SEQ | (ASN1_CONS << 5)))
424 return -EBADMSG;
425
426 /* Authority Key Identifier is not indefinite length */
427 if (unlikely(vlen == ASN1_INDEFINITE_LENGTH))
428 return -EBADMSG;
429
430 if (vlen < ASN1_INDEFINITE_LENGTH) {
431 /* Short Form length */
432 if (v[1] != vlen - 2 ||
433 v[2] != SEQ_TAG_KEYID ||
434 v[3] > vlen - 4)
435 return -EBADMSG;
436
437 key_len = v[3];
438 v += 4;
439 } else {
440 /* Long Form length */
441 size_t seq_len = 0;
442 size_t sub = v[1] - ASN1_INDEFINITE_LENGTH;
443
444 if (sub > 2)
445 return -EBADMSG;
446
447 /* calculate the length from subsequent octets */
448 v += 2;
449 for (i = 0; i < sub; i++) {
450 seq_len <<= 8;
451 seq_len |= v[i];
452 }
453
454 if (seq_len != vlen - 2 - sub ||
455 v[sub] != SEQ_TAG_KEYID ||
456 v[sub + 1] > vlen - 4 - sub)
457 return -EBADMSG;
458
459 key_len = v[sub + 1];
460 v += (sub + 2);
461 }
462
463 f = kmalloc(key_len * 2 + 1, GFP_KERNEL);
David Howellsc26fd692012-09-24 17:11:48 +0100464 if (!f)
465 return -ENOMEM;
Chun-Yi Lee04b00bd2013-04-22 10:56:55 +0930466 for (i = 0; i < key_len; i++)
David Howellsc26fd692012-09-24 17:11:48 +0100467 sprintf(f + i * 2, "%02x", v[i]);
468 pr_debug("authority %s\n", f);
469 ctx->cert->authority = f;
470 return 0;
471 }
472
473 return 0;
474}
475
476/*
477 * Record a certificate time.
478 */
David Howellsa5752d12012-10-02 14:36:16 +0100479static int x509_note_time(struct tm *tm, size_t hdrlen,
David Howellsc26fd692012-09-24 17:11:48 +0100480 unsigned char tag,
481 const unsigned char *value, size_t vlen)
482{
David Howellsc26fd692012-09-24 17:11:48 +0100483 const unsigned char *p = value;
484
485#define dec2bin(X) ((X) - '0')
486#define DD2bin(P) ({ unsigned x = dec2bin(P[0]) * 10 + dec2bin(P[1]); P += 2; x; })
487
488 if (tag == ASN1_UNITIM) {
489 /* UTCTime: YYMMDDHHMMSSZ */
490 if (vlen != 13)
491 goto unsupported_time;
David Howellsa5752d12012-10-02 14:36:16 +0100492 tm->tm_year = DD2bin(p);
493 if (tm->tm_year >= 50)
494 tm->tm_year += 1900;
David Howellsc26fd692012-09-24 17:11:48 +0100495 else
David Howellsa5752d12012-10-02 14:36:16 +0100496 tm->tm_year += 2000;
David Howellsc26fd692012-09-24 17:11:48 +0100497 } else if (tag == ASN1_GENTIM) {
498 /* GenTime: YYYYMMDDHHMMSSZ */
499 if (vlen != 15)
500 goto unsupported_time;
David Howellsa5752d12012-10-02 14:36:16 +0100501 tm->tm_year = DD2bin(p) * 100 + DD2bin(p);
David Howellsc26fd692012-09-24 17:11:48 +0100502 } else {
503 goto unsupported_time;
504 }
505
David Howellsa5752d12012-10-02 14:36:16 +0100506 tm->tm_year -= 1900;
507 tm->tm_mon = DD2bin(p) - 1;
508 tm->tm_mday = DD2bin(p);
509 tm->tm_hour = DD2bin(p);
510 tm->tm_min = DD2bin(p);
511 tm->tm_sec = DD2bin(p);
David Howellsc26fd692012-09-24 17:11:48 +0100512
513 if (*p != 'Z')
514 goto unsupported_time;
515
David Howellsc26fd692012-09-24 17:11:48 +0100516 return 0;
517
518unsupported_time:
519 pr_debug("Got unsupported time [tag %02x]: '%*.*s'\n",
520 tag, (int)vlen, (int)vlen, value);
521 return -EBADMSG;
522}
523
524int x509_note_not_before(void *context, size_t hdrlen,
525 unsigned char tag,
526 const void *value, size_t vlen)
527{
528 struct x509_parse_context *ctx = context;
529 return x509_note_time(&ctx->cert->valid_from, hdrlen, tag, value, vlen);
530}
531
532int x509_note_not_after(void *context, size_t hdrlen,
533 unsigned char tag,
534 const void *value, size_t vlen)
535{
536 struct x509_parse_context *ctx = context;
537 return x509_note_time(&ctx->cert->valid_to, hdrlen, tag, value, vlen);
538}