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/module.h>
15 #include <linux/export.h>
16 #include <linux/slab.h>
17 #include <linux/err.h>
18 #include <linux/oid_registry.h>
19 #include <crypto/public_key.h>
20 #include "pkcs7_parser.h"
21 #include "pkcs7.asn1.h"
22 
23 MODULE_DESCRIPTION("PKCS#7 parser");
24 MODULE_AUTHOR("Red Hat, Inc.");
25 MODULE_LICENSE("GPL");
26 
27 struct pkcs7_parse_context {
28 	struct pkcs7_message	*msg;		/* Message being constructed */
29 	struct pkcs7_signed_info *sinfo;	/* SignedInfo being constructed */
30 	struct pkcs7_signed_info **ppsinfo;
31 	struct x509_certificate *certs;		/* Certificate cache */
32 	struct x509_certificate **ppcerts;
33 	unsigned long	data;			/* Start of data */
34 	enum OID	last_oid;		/* Last OID encountered */
35 	unsigned	x509_index;
36 	unsigned	sinfo_index;
37 	const void	*raw_serial;
38 	unsigned	raw_serial_size;
39 	unsigned	raw_issuer_size;
40 	const void	*raw_issuer;
41 	const void	*raw_skid;
42 	unsigned	raw_skid_size;
43 	bool		expect_skid;
44 };
45 
46 /*
47  * Free a signed information block.
48  */
49 static void pkcs7_free_signed_info(struct pkcs7_signed_info *sinfo)
50 {
51 	if (sinfo) {
52 		public_key_signature_free(sinfo->sig);
53 		kfree(sinfo);
54 	}
55 }
56 
57 /**
58  * pkcs7_free_message - Free a PKCS#7 message
59  * @pkcs7: The PKCS#7 message to free
60  */
61 void pkcs7_free_message(struct pkcs7_message *pkcs7)
62 {
63 	struct x509_certificate *cert;
64 	struct pkcs7_signed_info *sinfo;
65 
66 	if (pkcs7) {
67 		while (pkcs7->certs) {
68 			cert = pkcs7->certs;
69 			pkcs7->certs = cert->next;
70 			x509_free_certificate(cert);
71 		}
72 		while (pkcs7->crl) {
73 			cert = pkcs7->crl;
74 			pkcs7->crl = cert->next;
75 			x509_free_certificate(cert);
76 		}
77 		while (pkcs7->signed_infos) {
78 			sinfo = pkcs7->signed_infos;
79 			pkcs7->signed_infos = sinfo->next;
80 			pkcs7_free_signed_info(sinfo);
81 		}
82 		kfree(pkcs7);
83 	}
84 }
85 EXPORT_SYMBOL_GPL(pkcs7_free_message);
86 
87 /*
88  * Check authenticatedAttributes are provided or not provided consistently.
89  */
90 static int pkcs7_check_authattrs(struct pkcs7_message *msg)
91 {
92 	struct pkcs7_signed_info *sinfo;
93 	bool want = false;
94 
95 	sinfo = msg->signed_infos;
96 	if (!sinfo)
97 		goto inconsistent;
98 
99 	if (sinfo->authattrs) {
100 		want = true;
101 		msg->have_authattrs = true;
102 	}
103 
104 	for (sinfo = sinfo->next; sinfo; sinfo = sinfo->next)
105 		if (!!sinfo->authattrs != want)
106 			goto inconsistent;
107 	return 0;
108 
109 inconsistent:
110 	pr_warn("Inconsistently supplied authAttrs\n");
111 	return -EINVAL;
112 }
113 
114 /**
115  * pkcs7_parse_message - Parse a PKCS#7 message
116  * @data: The raw binary ASN.1 encoded message to be parsed
117  * @datalen: The size of the encoded message
118  */
119 struct pkcs7_message *pkcs7_parse_message(const void *data, size_t datalen)
120 {
121 	struct pkcs7_parse_context *ctx;
122 	struct pkcs7_message *msg = ERR_PTR(-ENOMEM);
123 	int ret;
124 
125 	ctx = kzalloc(sizeof(struct pkcs7_parse_context), GFP_KERNEL);
126 	if (!ctx)
127 		goto out_no_ctx;
128 	ctx->msg = kzalloc(sizeof(struct pkcs7_message), GFP_KERNEL);
129 	if (!ctx->msg)
130 		goto out_no_msg;
131 	ctx->sinfo = kzalloc(sizeof(struct pkcs7_signed_info), GFP_KERNEL);
132 	if (!ctx->sinfo)
133 		goto out_no_sinfo;
134 	ctx->sinfo->sig = kzalloc(sizeof(struct public_key_signature),
135 				  GFP_KERNEL);
136 	if (!ctx->sinfo->sig)
137 		goto out_no_sig;
138 
139 	ctx->data = (unsigned long)data;
140 	ctx->ppcerts = &ctx->certs;
141 	ctx->ppsinfo = &ctx->msg->signed_infos;
142 
143 	/* Attempt to decode the signature */
144 	ret = asn1_ber_decoder(&pkcs7_decoder, ctx, data, datalen);
145 	if (ret < 0) {
146 		msg = ERR_PTR(ret);
147 		goto out;
148 	}
149 
150 	ret = pkcs7_check_authattrs(ctx->msg);
151 	if (ret < 0) {
152 		msg = ERR_PTR(ret);
153 		goto out;
154 	}
155 
156 	msg = ctx->msg;
157 	ctx->msg = NULL;
158 
159 out:
160 	while (ctx->certs) {
161 		struct x509_certificate *cert = ctx->certs;
162 		ctx->certs = cert->next;
163 		x509_free_certificate(cert);
164 	}
165 out_no_sig:
166 	pkcs7_free_signed_info(ctx->sinfo);
167 out_no_sinfo:
168 	pkcs7_free_message(ctx->msg);
169 out_no_msg:
170 	kfree(ctx);
171 out_no_ctx:
172 	return msg;
173 }
174 EXPORT_SYMBOL_GPL(pkcs7_parse_message);
175 
176 /**
177  * pkcs7_get_content_data - Get access to the PKCS#7 content
178  * @pkcs7: The preparsed PKCS#7 message to access
179  * @_data: Place to return a pointer to the data
180  * @_data_len: Place to return the data length
181  * @_headerlen: Size of ASN.1 header not included in _data
182  *
183  * Get access to the data content of the PKCS#7 message.  The size of the
184  * header of the ASN.1 object that contains it is also provided and can be used
185  * to adjust *_data and *_data_len to get the entire object.
186  *
187  * Returns -ENODATA if the data object was missing from the message.
188  */
189 int pkcs7_get_content_data(const struct pkcs7_message *pkcs7,
190 			   const void **_data, size_t *_data_len,
191 			   size_t *_headerlen)
192 {
193 	if (!pkcs7->data)
194 		return -ENODATA;
195 
196 	*_data = pkcs7->data;
197 	*_data_len = pkcs7->data_len;
198 	if (_headerlen)
199 		*_headerlen = pkcs7->data_hdrlen;
200 	return 0;
201 }
202 EXPORT_SYMBOL_GPL(pkcs7_get_content_data);
203 
204 /*
205  * Note an OID when we find one for later processing when we know how
206  * to interpret it.
207  */
208 int pkcs7_note_OID(void *context, size_t hdrlen,
209 		   unsigned char tag,
210 		   const void *value, size_t vlen)
211 {
212 	struct pkcs7_parse_context *ctx = context;
213 
214 	ctx->last_oid = look_up_OID(value, vlen);
215 	if (ctx->last_oid == OID__NR) {
216 		char buffer[50];
217 		sprint_oid(value, vlen, buffer, sizeof(buffer));
218 		printk("PKCS7: Unknown OID: [%lu] %s\n",
219 		       (unsigned long)value - ctx->data, buffer);
220 	}
221 	return 0;
222 }
223 
224 /*
225  * Note the digest algorithm for the signature.
226  */
227 int pkcs7_sig_note_digest_algo(void *context, size_t hdrlen,
228 			       unsigned char tag,
229 			       const void *value, size_t vlen)
230 {
231 	struct pkcs7_parse_context *ctx = context;
232 
233 	switch (ctx->last_oid) {
234 	case OID_md4:
235 		ctx->sinfo->sig->hash_algo = "md4";
236 		break;
237 	case OID_md5:
238 		ctx->sinfo->sig->hash_algo = "md5";
239 		break;
240 	case OID_sha1:
241 		ctx->sinfo->sig->hash_algo = "sha1";
242 		break;
243 	case OID_sha256:
244 		ctx->sinfo->sig->hash_algo = "sha256";
245 		break;
246 	case OID_sha384:
247 		ctx->sinfo->sig->hash_algo = "sha384";
248 		break;
249 	case OID_sha512:
250 		ctx->sinfo->sig->hash_algo = "sha512";
251 		break;
252 	case OID_sha224:
253 		ctx->sinfo->sig->hash_algo = "sha224";
254 		break;
255 	default:
256 		printk("Unsupported digest algo: %u\n", ctx->last_oid);
257 		return -ENOPKG;
258 	}
259 	return 0;
260 }
261 
262 /*
263  * Note the public key algorithm for the signature.
264  */
265 int pkcs7_sig_note_pkey_algo(void *context, size_t hdrlen,
266 			     unsigned char tag,
267 			     const void *value, size_t vlen)
268 {
269 	struct pkcs7_parse_context *ctx = context;
270 
271 	switch (ctx->last_oid) {
272 	case OID_rsaEncryption:
273 		ctx->sinfo->sig->pkey_algo = "rsa";
274 		break;
275 	default:
276 		printk("Unsupported pkey algo: %u\n", ctx->last_oid);
277 		return -ENOPKG;
278 	}
279 	return 0;
280 }
281 
282 /*
283  * We only support signed data [RFC2315 sec 9].
284  */
285 int pkcs7_check_content_type(void *context, size_t hdrlen,
286 			     unsigned char tag,
287 			     const void *value, size_t vlen)
288 {
289 	struct pkcs7_parse_context *ctx = context;
290 
291 	if (ctx->last_oid != OID_signed_data) {
292 		pr_warn("Only support pkcs7_signedData type\n");
293 		return -EINVAL;
294 	}
295 
296 	return 0;
297 }
298 
299 /*
300  * Note the SignedData version
301  */
302 int pkcs7_note_signeddata_version(void *context, size_t hdrlen,
303 				  unsigned char tag,
304 				  const void *value, size_t vlen)
305 {
306 	struct pkcs7_parse_context *ctx = context;
307 	unsigned version;
308 
309 	if (vlen != 1)
310 		goto unsupported;
311 
312 	ctx->msg->version = version = *(const u8 *)value;
313 	switch (version) {
314 	case 1:
315 		/* PKCS#7 SignedData [RFC2315 sec 9.1]
316 		 * CMS ver 1 SignedData [RFC5652 sec 5.1]
317 		 */
318 		break;
319 	case 3:
320 		/* CMS ver 3 SignedData [RFC2315 sec 5.1] */
321 		break;
322 	default:
323 		goto unsupported;
324 	}
325 
326 	return 0;
327 
328 unsupported:
329 	pr_warn("Unsupported SignedData version\n");
330 	return -EINVAL;
331 }
332 
333 /*
334  * Note the SignerInfo version
335  */
336 int pkcs7_note_signerinfo_version(void *context, size_t hdrlen,
337 				  unsigned char tag,
338 				  const void *value, size_t vlen)
339 {
340 	struct pkcs7_parse_context *ctx = context;
341 	unsigned version;
342 
343 	if (vlen != 1)
344 		goto unsupported;
345 
346 	version = *(const u8 *)value;
347 	switch (version) {
348 	case 1:
349 		/* PKCS#7 SignerInfo [RFC2315 sec 9.2]
350 		 * CMS ver 1 SignerInfo [RFC5652 sec 5.3]
351 		 */
352 		if (ctx->msg->version != 1)
353 			goto version_mismatch;
354 		ctx->expect_skid = false;
355 		break;
356 	case 3:
357 		/* CMS ver 3 SignerInfo [RFC2315 sec 5.3] */
358 		if (ctx->msg->version == 1)
359 			goto version_mismatch;
360 		ctx->expect_skid = true;
361 		break;
362 	default:
363 		goto unsupported;
364 	}
365 
366 	return 0;
367 
368 unsupported:
369 	pr_warn("Unsupported SignerInfo version\n");
370 	return -EINVAL;
371 version_mismatch:
372 	pr_warn("SignedData-SignerInfo version mismatch\n");
373 	return -EBADMSG;
374 }
375 
376 /*
377  * Extract a certificate and store it in the context.
378  */
379 int pkcs7_extract_cert(void *context, size_t hdrlen,
380 		       unsigned char tag,
381 		       const void *value, size_t vlen)
382 {
383 	struct pkcs7_parse_context *ctx = context;
384 	struct x509_certificate *x509;
385 
386 	if (tag != ((ASN1_UNIV << 6) | ASN1_CONS_BIT | ASN1_SEQ)) {
387 		pr_debug("Cert began with tag %02x at %lu\n",
388 			 tag, (unsigned long)ctx - ctx->data);
389 		return -EBADMSG;
390 	}
391 
392 	/* We have to correct for the header so that the X.509 parser can start
393 	 * from the beginning.  Note that since X.509 stipulates DER, there
394 	 * probably shouldn't be an EOC trailer - but it is in PKCS#7 (which
395 	 * stipulates BER).
396 	 */
397 	value -= hdrlen;
398 	vlen += hdrlen;
399 
400 	if (((u8*)value)[1] == 0x80)
401 		vlen += 2; /* Indefinite length - there should be an EOC */
402 
403 	x509 = x509_cert_parse(value, vlen);
404 	if (IS_ERR(x509))
405 		return PTR_ERR(x509);
406 
407 	x509->index = ++ctx->x509_index;
408 	pr_debug("Got cert %u for %s\n", x509->index, x509->subject);
409 	pr_debug("- fingerprint %*phN\n", x509->id->len, x509->id->data);
410 
411 	*ctx->ppcerts = x509;
412 	ctx->ppcerts = &x509->next;
413 	return 0;
414 }
415 
416 /*
417  * Save the certificate list
418  */
419 int pkcs7_note_certificate_list(void *context, size_t hdrlen,
420 				unsigned char tag,
421 				const void *value, size_t vlen)
422 {
423 	struct pkcs7_parse_context *ctx = context;
424 
425 	pr_devel("Got cert list (%02x)\n", tag);
426 
427 	*ctx->ppcerts = ctx->msg->certs;
428 	ctx->msg->certs = ctx->certs;
429 	ctx->certs = NULL;
430 	ctx->ppcerts = &ctx->certs;
431 	return 0;
432 }
433 
434 /*
435  * Note the content type.
436  */
437 int pkcs7_note_content(void *context, size_t hdrlen,
438 		       unsigned char tag,
439 		       const void *value, size_t vlen)
440 {
441 	struct pkcs7_parse_context *ctx = context;
442 
443 	if (ctx->last_oid != OID_data &&
444 	    ctx->last_oid != OID_msIndirectData) {
445 		pr_warn("Unsupported data type %d\n", ctx->last_oid);
446 		return -EINVAL;
447 	}
448 
449 	ctx->msg->data_type = ctx->last_oid;
450 	return 0;
451 }
452 
453 /*
454  * Extract the data from the message and store that and its content type OID in
455  * the context.
456  */
457 int pkcs7_note_data(void *context, size_t hdrlen,
458 		    unsigned char tag,
459 		    const void *value, size_t vlen)
460 {
461 	struct pkcs7_parse_context *ctx = context;
462 
463 	pr_debug("Got data\n");
464 
465 	ctx->msg->data = value;
466 	ctx->msg->data_len = vlen;
467 	ctx->msg->data_hdrlen = hdrlen;
468 	return 0;
469 }
470 
471 /*
472  * Parse authenticated attributes.
473  */
474 int pkcs7_sig_note_authenticated_attr(void *context, size_t hdrlen,
475 				      unsigned char tag,
476 				      const void *value, size_t vlen)
477 {
478 	struct pkcs7_parse_context *ctx = context;
479 	struct pkcs7_signed_info *sinfo = ctx->sinfo;
480 	enum OID content_type;
481 
482 	pr_devel("AuthAttr: %02x %zu [%*ph]\n", tag, vlen, (unsigned)vlen, value);
483 
484 	switch (ctx->last_oid) {
485 	case OID_contentType:
486 		if (__test_and_set_bit(sinfo_has_content_type, &sinfo->aa_set))
487 			goto repeated;
488 		content_type = look_up_OID(value, vlen);
489 		if (content_type != ctx->msg->data_type) {
490 			pr_warn("Mismatch between global data type (%d) and sinfo %u (%d)\n",
491 				ctx->msg->data_type, sinfo->index,
492 				content_type);
493 			return -EBADMSG;
494 		}
495 		return 0;
496 
497 	case OID_signingTime:
498 		if (__test_and_set_bit(sinfo_has_signing_time, &sinfo->aa_set))
499 			goto repeated;
500 		/* Should we check that the signing time is consistent
501 		 * with the signer's X.509 cert?
502 		 */
503 		return x509_decode_time(&sinfo->signing_time,
504 					hdrlen, tag, value, vlen);
505 
506 	case OID_messageDigest:
507 		if (__test_and_set_bit(sinfo_has_message_digest, &sinfo->aa_set))
508 			goto repeated;
509 		if (tag != ASN1_OTS)
510 			return -EBADMSG;
511 		sinfo->msgdigest = value;
512 		sinfo->msgdigest_len = vlen;
513 		return 0;
514 
515 	case OID_smimeCapabilites:
516 		if (__test_and_set_bit(sinfo_has_smime_caps, &sinfo->aa_set))
517 			goto repeated;
518 		if (ctx->msg->data_type != OID_msIndirectData) {
519 			pr_warn("S/MIME Caps only allowed with Authenticode\n");
520 			return -EKEYREJECTED;
521 		}
522 		return 0;
523 
524 		/* Microsoft SpOpusInfo seems to be contain cont[0] 16-bit BE
525 		 * char URLs and cont[1] 8-bit char URLs.
526 		 *
527 		 * Microsoft StatementType seems to contain a list of OIDs that
528 		 * are also used as extendedKeyUsage types in X.509 certs.
529 		 */
530 	case OID_msSpOpusInfo:
531 		if (__test_and_set_bit(sinfo_has_ms_opus_info, &sinfo->aa_set))
532 			goto repeated;
533 		goto authenticode_check;
534 	case OID_msStatementType:
535 		if (__test_and_set_bit(sinfo_has_ms_statement_type, &sinfo->aa_set))
536 			goto repeated;
537 	authenticode_check:
538 		if (ctx->msg->data_type != OID_msIndirectData) {
539 			pr_warn("Authenticode AuthAttrs only allowed with Authenticode\n");
540 			return -EKEYREJECTED;
541 		}
542 		/* I'm not sure how to validate these */
543 		return 0;
544 	default:
545 		return 0;
546 	}
547 
548 repeated:
549 	/* We permit max one item per AuthenticatedAttribute and no repeats */
550 	pr_warn("Repeated/multivalue AuthAttrs not permitted\n");
551 	return -EKEYREJECTED;
552 }
553 
554 /*
555  * Note the set of auth attributes for digestion purposes [RFC2315 sec 9.3]
556  */
557 int pkcs7_sig_note_set_of_authattrs(void *context, size_t hdrlen,
558 				    unsigned char tag,
559 				    const void *value, size_t vlen)
560 {
561 	struct pkcs7_parse_context *ctx = context;
562 	struct pkcs7_signed_info *sinfo = ctx->sinfo;
563 
564 	if (!test_bit(sinfo_has_content_type, &sinfo->aa_set) ||
565 	    !test_bit(sinfo_has_message_digest, &sinfo->aa_set)) {
566 		pr_warn("Missing required AuthAttr\n");
567 		return -EBADMSG;
568 	}
569 
570 	if (ctx->msg->data_type != OID_msIndirectData &&
571 	    test_bit(sinfo_has_ms_opus_info, &sinfo->aa_set)) {
572 		pr_warn("Unexpected Authenticode AuthAttr\n");
573 		return -EBADMSG;
574 	}
575 
576 	/* We need to switch the 'CONT 0' to a 'SET OF' when we digest */
577 	sinfo->authattrs = value - (hdrlen - 1);
578 	sinfo->authattrs_len = vlen + (hdrlen - 1);
579 	return 0;
580 }
581 
582 /*
583  * Note the issuing certificate serial number
584  */
585 int pkcs7_sig_note_serial(void *context, size_t hdrlen,
586 			  unsigned char tag,
587 			  const void *value, size_t vlen)
588 {
589 	struct pkcs7_parse_context *ctx = context;
590 	ctx->raw_serial = value;
591 	ctx->raw_serial_size = vlen;
592 	return 0;
593 }
594 
595 /*
596  * Note the issuer's name
597  */
598 int pkcs7_sig_note_issuer(void *context, size_t hdrlen,
599 			  unsigned char tag,
600 			  const void *value, size_t vlen)
601 {
602 	struct pkcs7_parse_context *ctx = context;
603 	ctx->raw_issuer = value;
604 	ctx->raw_issuer_size = vlen;
605 	return 0;
606 }
607 
608 /*
609  * Note the issuing cert's subjectKeyIdentifier
610  */
611 int pkcs7_sig_note_skid(void *context, size_t hdrlen,
612 			unsigned char tag,
613 			const void *value, size_t vlen)
614 {
615 	struct pkcs7_parse_context *ctx = context;
616 
617 	pr_devel("SKID: %02x %zu [%*ph]\n", tag, vlen, (unsigned)vlen, value);
618 
619 	ctx->raw_skid = value;
620 	ctx->raw_skid_size = vlen;
621 	return 0;
622 }
623 
624 /*
625  * Note the signature data
626  */
627 int pkcs7_sig_note_signature(void *context, size_t hdrlen,
628 			     unsigned char tag,
629 			     const void *value, size_t vlen)
630 {
631 	struct pkcs7_parse_context *ctx = context;
632 
633 	ctx->sinfo->sig->s = kmemdup(value, vlen, GFP_KERNEL);
634 	if (!ctx->sinfo->sig->s)
635 		return -ENOMEM;
636 
637 	ctx->sinfo->sig->s_size = vlen;
638 	return 0;
639 }
640 
641 /*
642  * Note a signature information block
643  */
644 int pkcs7_note_signed_info(void *context, size_t hdrlen,
645 			   unsigned char tag,
646 			   const void *value, size_t vlen)
647 {
648 	struct pkcs7_parse_context *ctx = context;
649 	struct pkcs7_signed_info *sinfo = ctx->sinfo;
650 	struct asymmetric_key_id *kid;
651 
652 	if (ctx->msg->data_type == OID_msIndirectData && !sinfo->authattrs) {
653 		pr_warn("Authenticode requires AuthAttrs\n");
654 		return -EBADMSG;
655 	}
656 
657 	/* Generate cert issuer + serial number key ID */
658 	if (!ctx->expect_skid) {
659 		kid = asymmetric_key_generate_id(ctx->raw_serial,
660 						 ctx->raw_serial_size,
661 						 ctx->raw_issuer,
662 						 ctx->raw_issuer_size);
663 	} else {
664 		kid = asymmetric_key_generate_id(ctx->raw_skid,
665 						 ctx->raw_skid_size,
666 						 "", 0);
667 	}
668 	if (IS_ERR(kid))
669 		return PTR_ERR(kid);
670 
671 	pr_devel("SINFO KID: %u [%*phN]\n", kid->len, kid->len, kid->data);
672 
673 	sinfo->sig->auth_ids[0] = kid;
674 	sinfo->index = ++ctx->sinfo_index;
675 	*ctx->ppsinfo = sinfo;
676 	ctx->ppsinfo = &sinfo->next;
677 	ctx->sinfo = kzalloc(sizeof(struct pkcs7_signed_info), GFP_KERNEL);
678 	if (!ctx->sinfo)
679 		return -ENOMEM;
680 	ctx->sinfo->sig = kzalloc(sizeof(struct public_key_signature),
681 				  GFP_KERNEL);
682 	if (!ctx->sinfo->sig)
683 		return -ENOMEM;
684 	return 0;
685 }
686