1 /* PKCS#7 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) "PKCS7: "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 "pkcs7_parser.h"
20 #include "pkcs7-asn1.h"
21 
22 struct pkcs7_parse_context {
23 	struct pkcs7_message	*msg;		/* Message being constructed */
24 	struct pkcs7_signed_info *sinfo;	/* SignedInfo being constructed */
25 	struct pkcs7_signed_info **ppsinfo;
26 	struct x509_certificate *certs;		/* Certificate cache */
27 	struct x509_certificate **ppcerts;
28 	unsigned long	data;			/* Start of data */
29 	enum OID	last_oid;		/* Last OID encountered */
30 	unsigned	x509_index;
31 	unsigned	sinfo_index;
32 	const void	*raw_serial;
33 	unsigned	raw_serial_size;
34 	unsigned	raw_issuer_size;
35 	const void	*raw_issuer;
36 	const void	*raw_skid;
37 	unsigned	raw_skid_size;
38 	bool		expect_skid;
39 };
40 
41 /*
42  * Free a signed information block.
43  */
44 static void pkcs7_free_signed_info(struct pkcs7_signed_info *sinfo)
45 {
46 	if (sinfo) {
47 		public_key_signature_free(sinfo->sig);
48 		kfree(sinfo);
49 	}
50 }
51 
52 /**
53  * pkcs7_free_message - Free a PKCS#7 message
54  * @pkcs7: The PKCS#7 message to free
55  */
56 void pkcs7_free_message(struct pkcs7_message *pkcs7)
57 {
58 	struct x509_certificate *cert;
59 	struct pkcs7_signed_info *sinfo;
60 
61 	if (pkcs7) {
62 		while (pkcs7->certs) {
63 			cert = pkcs7->certs;
64 			pkcs7->certs = cert->next;
65 			x509_free_certificate(cert);
66 		}
67 		while (pkcs7->crl) {
68 			cert = pkcs7->crl;
69 			pkcs7->crl = cert->next;
70 			x509_free_certificate(cert);
71 		}
72 		while (pkcs7->signed_infos) {
73 			sinfo = pkcs7->signed_infos;
74 			pkcs7->signed_infos = sinfo->next;
75 			pkcs7_free_signed_info(sinfo);
76 		}
77 		kfree(pkcs7);
78 	}
79 }
80 EXPORT_SYMBOL_GPL(pkcs7_free_message);
81 
82 /*
83  * Check authenticatedAttributes are provided or not provided consistently.
84  */
85 static int pkcs7_check_authattrs(struct pkcs7_message *msg)
86 {
87 	struct pkcs7_signed_info *sinfo;
88 	bool want = false;
89 
90 	sinfo = msg->signed_infos;
91 	if (!sinfo)
92 		goto inconsistent;
93 
94 	if (sinfo->authattrs) {
95 		want = true;
96 		msg->have_authattrs = true;
97 	}
98 
99 	for (sinfo = sinfo->next; sinfo; sinfo = sinfo->next)
100 		if (!!sinfo->authattrs != want)
101 			goto inconsistent;
102 	return 0;
103 
104 inconsistent:
105 	pr_warn("Inconsistently supplied authAttrs\n");
106 	return -EINVAL;
107 }
108 
109 /**
110  * pkcs7_parse_message - Parse a PKCS#7 message
111  * @data: The raw binary ASN.1 encoded message to be parsed
112  * @datalen: The size of the encoded message
113  */
114 struct pkcs7_message *pkcs7_parse_message(const void *data, size_t datalen)
115 {
116 	struct pkcs7_parse_context *ctx;
117 	struct pkcs7_message *msg = ERR_PTR(-ENOMEM);
118 	int ret;
119 
120 	ctx = kzalloc(sizeof(struct pkcs7_parse_context), GFP_KERNEL);
121 	if (!ctx)
122 		goto out_no_ctx;
123 	ctx->msg = kzalloc(sizeof(struct pkcs7_message), GFP_KERNEL);
124 	if (!ctx->msg)
125 		goto out_no_msg;
126 	ctx->sinfo = kzalloc(sizeof(struct pkcs7_signed_info), GFP_KERNEL);
127 	if (!ctx->sinfo)
128 		goto out_no_sinfo;
129 	ctx->sinfo->sig = kzalloc(sizeof(struct public_key_signature),
130 				  GFP_KERNEL);
131 	if (!ctx->sinfo->sig)
132 		goto out_no_sig;
133 
134 	ctx->data = (unsigned long)data;
135 	ctx->ppcerts = &ctx->certs;
136 	ctx->ppsinfo = &ctx->msg->signed_infos;
137 
138 	/* Attempt to decode the signature */
139 	ret = asn1_ber_decoder(&pkcs7_decoder, ctx, data, datalen);
140 	if (ret < 0) {
141 		msg = ERR_PTR(ret);
142 		goto out;
143 	}
144 
145 	ret = pkcs7_check_authattrs(ctx->msg);
146 	if (ret < 0)
147 		goto out;
148 
149 	msg = ctx->msg;
150 	ctx->msg = NULL;
151 
152 out:
153 	while (ctx->certs) {
154 		struct x509_certificate *cert = ctx->certs;
155 		ctx->certs = cert->next;
156 		x509_free_certificate(cert);
157 	}
158 out_no_sig:
159 	pkcs7_free_signed_info(ctx->sinfo);
160 out_no_sinfo:
161 	pkcs7_free_message(ctx->msg);
162 out_no_msg:
163 	kfree(ctx);
164 out_no_ctx:
165 	return msg;
166 }
167 EXPORT_SYMBOL_GPL(pkcs7_parse_message);
168 
169 /**
170  * pkcs7_get_content_data - Get access to the PKCS#7 content
171  * @pkcs7: The preparsed PKCS#7 message to access
172  * @_data: Place to return a pointer to the data
173  * @_data_len: Place to return the data length
174  * @_headerlen: Size of ASN.1 header not included in _data
175  *
176  * Get access to the data content of the PKCS#7 message.  The size of the
177  * header of the ASN.1 object that contains it is also provided and can be used
178  * to adjust *_data and *_data_len to get the entire object.
179  *
180  * Returns -ENODATA if the data object was missing from the message.
181  */
182 int pkcs7_get_content_data(const struct pkcs7_message *pkcs7,
183 			   const void **_data, size_t *_data_len,
184 			   size_t *_headerlen)
185 {
186 	if (!pkcs7->data)
187 		return -ENODATA;
188 
189 	*_data = pkcs7->data;
190 	*_data_len = pkcs7->data_len;
191 	if (_headerlen)
192 		*_headerlen = pkcs7->data_hdrlen;
193 	return 0;
194 }
195 EXPORT_SYMBOL_GPL(pkcs7_get_content_data);
196 
197 /*
198  * Note an OID when we find one for later processing when we know how
199  * to interpret it.
200  */
201 int pkcs7_note_OID(void *context, size_t hdrlen,
202 		   unsigned char tag,
203 		   const void *value, size_t vlen)
204 {
205 	struct pkcs7_parse_context *ctx = context;
206 
207 	ctx->last_oid = look_up_OID(value, vlen);
208 	if (ctx->last_oid == OID__NR) {
209 		char buffer[50];
210 		sprint_oid(value, vlen, buffer, sizeof(buffer));
211 		printk("PKCS7: Unknown OID: [%lu] %s\n",
212 		       (unsigned long)value - ctx->data, buffer);
213 	}
214 	return 0;
215 }
216 
217 /*
218  * Note the digest algorithm for the signature.
219  */
220 int pkcs7_sig_note_digest_algo(void *context, size_t hdrlen,
221 			       unsigned char tag,
222 			       const void *value, size_t vlen)
223 {
224 	struct pkcs7_parse_context *ctx = context;
225 
226 	switch (ctx->last_oid) {
227 	case OID_md4:
228 		ctx->sinfo->sig->hash_algo = "md4";
229 		break;
230 	case OID_md5:
231 		ctx->sinfo->sig->hash_algo = "md5";
232 		break;
233 	case OID_sha1:
234 		ctx->sinfo->sig->hash_algo = "sha1";
235 		break;
236 	case OID_sha256:
237 		ctx->sinfo->sig->hash_algo = "sha256";
238 		break;
239 	case OID_sha384:
240 		ctx->sinfo->sig->hash_algo = "sha384";
241 		break;
242 	case OID_sha512:
243 		ctx->sinfo->sig->hash_algo = "sha512";
244 		break;
245 	case OID_sha224:
246 		ctx->sinfo->sig->hash_algo = "sha224";
247 		break;
248 	default:
249 		printk("Unsupported digest algo: %u\n", ctx->last_oid);
250 		return -ENOPKG;
251 	}
252 	return 0;
253 }
254 
255 /*
256  * Note the public key algorithm for the signature.
257  */
258 int pkcs7_sig_note_pkey_algo(void *context, size_t hdrlen,
259 			     unsigned char tag,
260 			     const void *value, size_t vlen)
261 {
262 	struct pkcs7_parse_context *ctx = context;
263 
264 	switch (ctx->last_oid) {
265 	case OID_rsaEncryption:
266 		ctx->sinfo->sig->pkey_algo = "rsa";
267 		break;
268 	default:
269 		printk("Unsupported pkey algo: %u\n", ctx->last_oid);
270 		return -ENOPKG;
271 	}
272 	return 0;
273 }
274 
275 /*
276  * We only support signed data [RFC2315 sec 9].
277  */
278 int pkcs7_check_content_type(void *context, size_t hdrlen,
279 			     unsigned char tag,
280 			     const void *value, size_t vlen)
281 {
282 	struct pkcs7_parse_context *ctx = context;
283 
284 	if (ctx->last_oid != OID_signed_data) {
285 		pr_warn("Only support pkcs7_signedData type\n");
286 		return -EINVAL;
287 	}
288 
289 	return 0;
290 }
291 
292 /*
293  * Note the SignedData version
294  */
295 int pkcs7_note_signeddata_version(void *context, size_t hdrlen,
296 				  unsigned char tag,
297 				  const void *value, size_t vlen)
298 {
299 	struct pkcs7_parse_context *ctx = context;
300 	unsigned version;
301 
302 	if (vlen != 1)
303 		goto unsupported;
304 
305 	ctx->msg->version = version = *(const u8 *)value;
306 	switch (version) {
307 	case 1:
308 		/* PKCS#7 SignedData [RFC2315 sec 9.1]
309 		 * CMS ver 1 SignedData [RFC5652 sec 5.1]
310 		 */
311 		break;
312 	case 3:
313 		/* CMS ver 3 SignedData [RFC2315 sec 5.1] */
314 		break;
315 	default:
316 		goto unsupported;
317 	}
318 
319 	return 0;
320 
321 unsupported:
322 	pr_warn("Unsupported SignedData version\n");
323 	return -EINVAL;
324 }
325 
326 /*
327  * Note the SignerInfo version
328  */
329 int pkcs7_note_signerinfo_version(void *context, size_t hdrlen,
330 				  unsigned char tag,
331 				  const void *value, size_t vlen)
332 {
333 	struct pkcs7_parse_context *ctx = context;
334 	unsigned version;
335 
336 	if (vlen != 1)
337 		goto unsupported;
338 
339 	version = *(const u8 *)value;
340 	switch (version) {
341 	case 1:
342 		/* PKCS#7 SignerInfo [RFC2315 sec 9.2]
343 		 * CMS ver 1 SignerInfo [RFC5652 sec 5.3]
344 		 */
345 		if (ctx->msg->version != 1)
346 			goto version_mismatch;
347 		ctx->expect_skid = false;
348 		break;
349 	case 3:
350 		/* CMS ver 3 SignerInfo [RFC2315 sec 5.3] */
351 		if (ctx->msg->version == 1)
352 			goto version_mismatch;
353 		ctx->expect_skid = true;
354 		break;
355 	default:
356 		goto unsupported;
357 	}
358 
359 	return 0;
360 
361 unsupported:
362 	pr_warn("Unsupported SignerInfo version\n");
363 	return -EINVAL;
364 version_mismatch:
365 	pr_warn("SignedData-SignerInfo version mismatch\n");
366 	return -EBADMSG;
367 }
368 
369 /*
370  * Extract a certificate and store it in the context.
371  */
372 int pkcs7_extract_cert(void *context, size_t hdrlen,
373 		       unsigned char tag,
374 		       const void *value, size_t vlen)
375 {
376 	struct pkcs7_parse_context *ctx = context;
377 	struct x509_certificate *x509;
378 
379 	if (tag != ((ASN1_UNIV << 6) | ASN1_CONS_BIT | ASN1_SEQ)) {
380 		pr_debug("Cert began with tag %02x at %lu\n",
381 			 tag, (unsigned long)ctx - ctx->data);
382 		return -EBADMSG;
383 	}
384 
385 	/* We have to correct for the header so that the X.509 parser can start
386 	 * from the beginning.  Note that since X.509 stipulates DER, there
387 	 * probably shouldn't be an EOC trailer - but it is in PKCS#7 (which
388 	 * stipulates BER).
389 	 */
390 	value -= hdrlen;
391 	vlen += hdrlen;
392 
393 	if (((u8*)value)[1] == 0x80)
394 		vlen += 2; /* Indefinite length - there should be an EOC */
395 
396 	x509 = x509_cert_parse(value, vlen);
397 	if (IS_ERR(x509))
398 		return PTR_ERR(x509);
399 
400 	x509->index = ++ctx->x509_index;
401 	pr_debug("Got cert %u for %s\n", x509->index, x509->subject);
402 	pr_debug("- fingerprint %*phN\n", x509->id->len, x509->id->data);
403 
404 	*ctx->ppcerts = x509;
405 	ctx->ppcerts = &x509->next;
406 	return 0;
407 }
408 
409 /*
410  * Save the certificate list
411  */
412 int pkcs7_note_certificate_list(void *context, size_t hdrlen,
413 				unsigned char tag,
414 				const void *value, size_t vlen)
415 {
416 	struct pkcs7_parse_context *ctx = context;
417 
418 	pr_devel("Got cert list (%02x)\n", tag);
419 
420 	*ctx->ppcerts = ctx->msg->certs;
421 	ctx->msg->certs = ctx->certs;
422 	ctx->certs = NULL;
423 	ctx->ppcerts = &ctx->certs;
424 	return 0;
425 }
426 
427 /*
428  * Note the content type.
429  */
430 int pkcs7_note_content(void *context, size_t hdrlen,
431 		       unsigned char tag,
432 		       const void *value, size_t vlen)
433 {
434 	struct pkcs7_parse_context *ctx = context;
435 
436 	if (ctx->last_oid != OID_data &&
437 	    ctx->last_oid != OID_msIndirectData) {
438 		pr_warn("Unsupported data type %d\n", ctx->last_oid);
439 		return -EINVAL;
440 	}
441 
442 	ctx->msg->data_type = ctx->last_oid;
443 	return 0;
444 }
445 
446 /*
447  * Extract the data from the message and store that and its content type OID in
448  * the context.
449  */
450 int pkcs7_note_data(void *context, size_t hdrlen,
451 		    unsigned char tag,
452 		    const void *value, size_t vlen)
453 {
454 	struct pkcs7_parse_context *ctx = context;
455 
456 	pr_debug("Got data\n");
457 
458 	ctx->msg->data = value;
459 	ctx->msg->data_len = vlen;
460 	ctx->msg->data_hdrlen = hdrlen;
461 	return 0;
462 }
463 
464 /*
465  * Parse authenticated attributes.
466  */
467 int pkcs7_sig_note_authenticated_attr(void *context, size_t hdrlen,
468 				      unsigned char tag,
469 				      const void *value, size_t vlen)
470 {
471 	struct pkcs7_parse_context *ctx = context;
472 	struct pkcs7_signed_info *sinfo = ctx->sinfo;
473 	enum OID content_type;
474 
475 	pr_devel("AuthAttr: %02x %zu [%*ph]\n", tag, vlen, (unsigned)vlen, value);
476 
477 	switch (ctx->last_oid) {
478 	case OID_contentType:
479 		if (__test_and_set_bit(sinfo_has_content_type, &sinfo->aa_set))
480 			goto repeated;
481 		content_type = look_up_OID(value, vlen);
482 		if (content_type != ctx->msg->data_type) {
483 			pr_warn("Mismatch between global data type (%d) and sinfo %u (%d)\n",
484 				ctx->msg->data_type, sinfo->index,
485 				content_type);
486 			return -EBADMSG;
487 		}
488 		return 0;
489 
490 	case OID_signingTime:
491 		if (__test_and_set_bit(sinfo_has_signing_time, &sinfo->aa_set))
492 			goto repeated;
493 		/* Should we check that the signing time is consistent
494 		 * with the signer's X.509 cert?
495 		 */
496 		return x509_decode_time(&sinfo->signing_time,
497 					hdrlen, tag, value, vlen);
498 
499 	case OID_messageDigest:
500 		if (__test_and_set_bit(sinfo_has_message_digest, &sinfo->aa_set))
501 			goto repeated;
502 		if (tag != ASN1_OTS)
503 			return -EBADMSG;
504 		sinfo->msgdigest = value;
505 		sinfo->msgdigest_len = vlen;
506 		return 0;
507 
508 	case OID_smimeCapabilites:
509 		if (__test_and_set_bit(sinfo_has_smime_caps, &sinfo->aa_set))
510 			goto repeated;
511 		if (ctx->msg->data_type != OID_msIndirectData) {
512 			pr_warn("S/MIME Caps only allowed with Authenticode\n");
513 			return -EKEYREJECTED;
514 		}
515 		return 0;
516 
517 		/* Microsoft SpOpusInfo seems to be contain cont[0] 16-bit BE
518 		 * char URLs and cont[1] 8-bit char URLs.
519 		 *
520 		 * Microsoft StatementType seems to contain a list of OIDs that
521 		 * are also used as extendedKeyUsage types in X.509 certs.
522 		 */
523 	case OID_msSpOpusInfo:
524 		if (__test_and_set_bit(sinfo_has_ms_opus_info, &sinfo->aa_set))
525 			goto repeated;
526 		goto authenticode_check;
527 	case OID_msStatementType:
528 		if (__test_and_set_bit(sinfo_has_ms_statement_type, &sinfo->aa_set))
529 			goto repeated;
530 	authenticode_check:
531 		if (ctx->msg->data_type != OID_msIndirectData) {
532 			pr_warn("Authenticode AuthAttrs only allowed with Authenticode\n");
533 			return -EKEYREJECTED;
534 		}
535 		/* I'm not sure how to validate these */
536 		return 0;
537 	default:
538 		return 0;
539 	}
540 
541 repeated:
542 	/* We permit max one item per AuthenticatedAttribute and no repeats */
543 	pr_warn("Repeated/multivalue AuthAttrs not permitted\n");
544 	return -EKEYREJECTED;
545 }
546 
547 /*
548  * Note the set of auth attributes for digestion purposes [RFC2315 sec 9.3]
549  */
550 int pkcs7_sig_note_set_of_authattrs(void *context, size_t hdrlen,
551 				    unsigned char tag,
552 				    const void *value, size_t vlen)
553 {
554 	struct pkcs7_parse_context *ctx = context;
555 	struct pkcs7_signed_info *sinfo = ctx->sinfo;
556 
557 	if (!test_bit(sinfo_has_content_type, &sinfo->aa_set) ||
558 	    !test_bit(sinfo_has_message_digest, &sinfo->aa_set)) {
559 		pr_warn("Missing required AuthAttr\n");
560 		return -EBADMSG;
561 	}
562 
563 	if (ctx->msg->data_type != OID_msIndirectData &&
564 	    test_bit(sinfo_has_ms_opus_info, &sinfo->aa_set)) {
565 		pr_warn("Unexpected Authenticode AuthAttr\n");
566 		return -EBADMSG;
567 	}
568 
569 	/* We need to switch the 'CONT 0' to a 'SET OF' when we digest */
570 	sinfo->authattrs = value - (hdrlen - 1);
571 	sinfo->authattrs_len = vlen + (hdrlen - 1);
572 	return 0;
573 }
574 
575 /*
576  * Note the issuing certificate serial number
577  */
578 int pkcs7_sig_note_serial(void *context, size_t hdrlen,
579 			  unsigned char tag,
580 			  const void *value, size_t vlen)
581 {
582 	struct pkcs7_parse_context *ctx = context;
583 	ctx->raw_serial = value;
584 	ctx->raw_serial_size = vlen;
585 	return 0;
586 }
587 
588 /*
589  * Note the issuer's name
590  */
591 int pkcs7_sig_note_issuer(void *context, size_t hdrlen,
592 			  unsigned char tag,
593 			  const void *value, size_t vlen)
594 {
595 	struct pkcs7_parse_context *ctx = context;
596 	ctx->raw_issuer = value;
597 	ctx->raw_issuer_size = vlen;
598 	return 0;
599 }
600 
601 /*
602  * Note the issuing cert's subjectKeyIdentifier
603  */
604 int pkcs7_sig_note_skid(void *context, size_t hdrlen,
605 			unsigned char tag,
606 			const void *value, size_t vlen)
607 {
608 	struct pkcs7_parse_context *ctx = context;
609 
610 	pr_devel("SKID: %02x %zu [%*ph]\n", tag, vlen, (unsigned)vlen, value);
611 
612 	ctx->raw_skid = value;
613 	ctx->raw_skid_size = vlen;
614 	return 0;
615 }
616 
617 /*
618  * Note the signature data
619  */
620 int pkcs7_sig_note_signature(void *context, size_t hdrlen,
621 			     unsigned char tag,
622 			     const void *value, size_t vlen)
623 {
624 	struct pkcs7_parse_context *ctx = context;
625 
626 	ctx->sinfo->sig->s = kmemdup(value, vlen, GFP_KERNEL);
627 	if (!ctx->sinfo->sig->s)
628 		return -ENOMEM;
629 
630 	ctx->sinfo->sig->s_size = vlen;
631 	return 0;
632 }
633 
634 /*
635  * Note a signature information block
636  */
637 int pkcs7_note_signed_info(void *context, size_t hdrlen,
638 			   unsigned char tag,
639 			   const void *value, size_t vlen)
640 {
641 	struct pkcs7_parse_context *ctx = context;
642 	struct pkcs7_signed_info *sinfo = ctx->sinfo;
643 	struct asymmetric_key_id *kid;
644 
645 	if (ctx->msg->data_type == OID_msIndirectData && !sinfo->authattrs) {
646 		pr_warn("Authenticode requires AuthAttrs\n");
647 		return -EBADMSG;
648 	}
649 
650 	/* Generate cert issuer + serial number key ID */
651 	if (!ctx->expect_skid) {
652 		kid = asymmetric_key_generate_id(ctx->raw_serial,
653 						 ctx->raw_serial_size,
654 						 ctx->raw_issuer,
655 						 ctx->raw_issuer_size);
656 	} else {
657 		kid = asymmetric_key_generate_id(ctx->raw_skid,
658 						 ctx->raw_skid_size,
659 						 "", 0);
660 	}
661 	if (IS_ERR(kid))
662 		return PTR_ERR(kid);
663 
664 	pr_devel("SINFO KID: %u [%*phN]\n", kid->len, kid->len, kid->data);
665 
666 	sinfo->sig->auth_ids[0] = kid;
667 	sinfo->index = ++ctx->sinfo_index;
668 	*ctx->ppsinfo = sinfo;
669 	ctx->ppsinfo = &sinfo->next;
670 	ctx->sinfo = kzalloc(sizeof(struct pkcs7_signed_info), GFP_KERNEL);
671 	if (!ctx->sinfo)
672 		return -ENOMEM;
673 	ctx->sinfo->sig = kzalloc(sizeof(struct public_key_signature),
674 				  GFP_KERNEL);
675 	if (!ctx->sinfo->sig)
676 		return -ENOMEM;
677 	return 0;
678 }
679