xref: /linux/crypto/asymmetric_keys/x509_cert_parser.c (revision 4999999ed7e099fcc2476c8b3a245c4c2c9026c0)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* X.509 certificate parser
3  *
4  * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
5  * Written by David Howells (dhowells@redhat.com)
6  */
7 
8 #define pr_fmt(fmt) "X.509: "fmt
9 #include <linux/kernel.h>
10 #include <linux/export.h>
11 #include <linux/slab.h>
12 #include <linux/err.h>
13 #include <linux/oid_registry.h>
14 #include <crypto/public_key.h>
15 #include "x509_parser.h"
16 #include "x509.asn1.h"
17 #include "x509_akid.asn1.h"
18 
19 struct x509_parse_context {
20 	struct x509_certificate	*cert;		/* Certificate being constructed */
21 	unsigned long	data;			/* Start of data */
22 	const void	*key;			/* Key data */
23 	size_t		key_size;		/* Size of key data */
24 	const void	*params;		/* Key parameters */
25 	size_t		params_size;		/* Size of key parameters */
26 	enum OID	key_algo;		/* Algorithm used by the cert's key */
27 	enum OID	last_oid;		/* Last OID encountered */
28 	enum OID	sig_algo;		/* Algorithm used to sign the cert */
29 	u8		o_size;			/* Size of organizationName (O) */
30 	u8		cn_size;		/* Size of commonName (CN) */
31 	u8		email_size;		/* Size of emailAddress */
32 	u16		o_offset;		/* Offset of organizationName (O) */
33 	u16		cn_offset;		/* Offset of commonName (CN) */
34 	u16		email_offset;		/* Offset of emailAddress */
35 	unsigned	raw_akid_size;
36 	const void	*raw_akid;		/* Raw authorityKeyId in ASN.1 */
37 	const void	*akid_raw_issuer;	/* Raw directoryName in authorityKeyId */
38 	unsigned	akid_raw_issuer_size;
39 };
40 
41 /*
42  * Free an X.509 certificate
43  */
44 void x509_free_certificate(struct x509_certificate *cert)
45 {
46 	if (cert) {
47 		public_key_free(cert->pub);
48 		public_key_signature_free(cert->sig);
49 		kfree(cert->issuer);
50 		kfree(cert->subject);
51 		kfree(cert->id);
52 		kfree(cert->skid);
53 		kfree(cert);
54 	}
55 }
56 EXPORT_SYMBOL_GPL(x509_free_certificate);
57 
58 /*
59  * Parse an X.509 certificate
60  */
61 struct x509_certificate *x509_cert_parse(const void *data, size_t datalen)
62 {
63 	struct x509_certificate *cert;
64 	struct x509_parse_context *ctx;
65 	struct asymmetric_key_id *kid;
66 	long ret;
67 
68 	ret = -ENOMEM;
69 	cert = kzalloc(sizeof(struct x509_certificate), GFP_KERNEL);
70 	if (!cert)
71 		goto error_no_cert;
72 	cert->pub = kzalloc(sizeof(struct public_key), GFP_KERNEL);
73 	if (!cert->pub)
74 		goto error_no_ctx;
75 	cert->sig = kzalloc(sizeof(struct public_key_signature), GFP_KERNEL);
76 	if (!cert->sig)
77 		goto error_no_ctx;
78 	ctx = kzalloc(sizeof(struct x509_parse_context), GFP_KERNEL);
79 	if (!ctx)
80 		goto error_no_ctx;
81 
82 	ctx->cert = cert;
83 	ctx->data = (unsigned long)data;
84 
85 	/* Attempt to decode the certificate */
86 	ret = asn1_ber_decoder(&x509_decoder, ctx, data, datalen);
87 	if (ret < 0)
88 		goto error_decode;
89 
90 	/* Decode the AuthorityKeyIdentifier */
91 	if (ctx->raw_akid) {
92 		pr_devel("AKID: %u %*phN\n",
93 			 ctx->raw_akid_size, ctx->raw_akid_size, ctx->raw_akid);
94 		ret = asn1_ber_decoder(&x509_akid_decoder, ctx,
95 				       ctx->raw_akid, ctx->raw_akid_size);
96 		if (ret < 0) {
97 			pr_warn("Couldn't decode AuthKeyIdentifier\n");
98 			goto error_decode;
99 		}
100 	}
101 
102 	ret = -ENOMEM;
103 	cert->pub->key = kmemdup(ctx->key, ctx->key_size, GFP_KERNEL);
104 	if (!cert->pub->key)
105 		goto error_decode;
106 
107 	cert->pub->keylen = ctx->key_size;
108 
109 	cert->pub->params = kmemdup(ctx->params, ctx->params_size, GFP_KERNEL);
110 	if (!cert->pub->params)
111 		goto error_decode;
112 
113 	cert->pub->paramlen = ctx->params_size;
114 	cert->pub->algo = ctx->key_algo;
115 
116 	/* Grab the signature bits */
117 	ret = x509_get_sig_params(cert);
118 	if (ret < 0)
119 		goto error_decode;
120 
121 	/* Generate cert issuer + serial number key ID */
122 	kid = asymmetric_key_generate_id(cert->raw_serial,
123 					 cert->raw_serial_size,
124 					 cert->raw_issuer,
125 					 cert->raw_issuer_size);
126 	if (IS_ERR(kid)) {
127 		ret = PTR_ERR(kid);
128 		goto error_decode;
129 	}
130 	cert->id = kid;
131 
132 	/* Detect self-signed certificates */
133 	ret = x509_check_for_self_signed(cert);
134 	if (ret < 0)
135 		goto error_decode;
136 
137 	kfree(ctx);
138 	return cert;
139 
140 error_decode:
141 	kfree(ctx);
142 error_no_ctx:
143 	x509_free_certificate(cert);
144 error_no_cert:
145 	return ERR_PTR(ret);
146 }
147 EXPORT_SYMBOL_GPL(x509_cert_parse);
148 
149 /*
150  * Note an OID when we find one for later processing when we know how
151  * to interpret it.
152  */
153 int x509_note_OID(void *context, size_t hdrlen,
154 	     unsigned char tag,
155 	     const void *value, size_t vlen)
156 {
157 	struct x509_parse_context *ctx = context;
158 
159 	ctx->last_oid = look_up_OID(value, vlen);
160 	if (ctx->last_oid == OID__NR) {
161 		char buffer[50];
162 		sprint_oid(value, vlen, buffer, sizeof(buffer));
163 		pr_debug("Unknown OID: [%lu] %s\n",
164 			 (unsigned long)value - ctx->data, buffer);
165 	}
166 	return 0;
167 }
168 
169 /*
170  * Save the position of the TBS data so that we can check the signature over it
171  * later.
172  */
173 int x509_note_tbs_certificate(void *context, size_t hdrlen,
174 			      unsigned char tag,
175 			      const void *value, size_t vlen)
176 {
177 	struct x509_parse_context *ctx = context;
178 
179 	pr_debug("x509_note_tbs_certificate(,%zu,%02x,%ld,%zu)!\n",
180 		 hdrlen, tag, (unsigned long)value - ctx->data, vlen);
181 
182 	ctx->cert->tbs = value - hdrlen;
183 	ctx->cert->tbs_size = vlen + hdrlen;
184 	return 0;
185 }
186 
187 /*
188  * Record the algorithm that was used to sign this certificate.
189  */
190 int x509_note_sig_algo(void *context, size_t hdrlen, unsigned char tag,
191 		       const void *value, size_t vlen)
192 {
193 	struct x509_parse_context *ctx = context;
194 
195 	pr_debug("PubKey Algo: %u\n", ctx->last_oid);
196 
197 	switch (ctx->last_oid) {
198 	default:
199 		return -ENOPKG; /* Unsupported combination */
200 
201 	case OID_sha1WithRSAEncryption:
202 		ctx->cert->sig->hash_algo = "sha1";
203 		goto rsa_pkcs1;
204 
205 	case OID_sha256WithRSAEncryption:
206 		ctx->cert->sig->hash_algo = "sha256";
207 		goto rsa_pkcs1;
208 
209 	case OID_sha384WithRSAEncryption:
210 		ctx->cert->sig->hash_algo = "sha384";
211 		goto rsa_pkcs1;
212 
213 	case OID_sha512WithRSAEncryption:
214 		ctx->cert->sig->hash_algo = "sha512";
215 		goto rsa_pkcs1;
216 
217 	case OID_sha224WithRSAEncryption:
218 		ctx->cert->sig->hash_algo = "sha224";
219 		goto rsa_pkcs1;
220 
221 	case OID_id_ecdsa_with_sha1:
222 		ctx->cert->sig->hash_algo = "sha1";
223 		goto ecdsa;
224 
225 	case OID_id_ecdsa_with_sha224:
226 		ctx->cert->sig->hash_algo = "sha224";
227 		goto ecdsa;
228 
229 	case OID_id_ecdsa_with_sha256:
230 		ctx->cert->sig->hash_algo = "sha256";
231 		goto ecdsa;
232 
233 	case OID_id_ecdsa_with_sha384:
234 		ctx->cert->sig->hash_algo = "sha384";
235 		goto ecdsa;
236 
237 	case OID_id_ecdsa_with_sha512:
238 		ctx->cert->sig->hash_algo = "sha512";
239 		goto ecdsa;
240 
241 	case OID_gost2012Signature256:
242 		ctx->cert->sig->hash_algo = "streebog256";
243 		goto ecrdsa;
244 
245 	case OID_gost2012Signature512:
246 		ctx->cert->sig->hash_algo = "streebog512";
247 		goto ecrdsa;
248 
249 	case OID_SM2_with_SM3:
250 		ctx->cert->sig->hash_algo = "sm3";
251 		goto sm2;
252 	}
253 
254 rsa_pkcs1:
255 	ctx->cert->sig->pkey_algo = "rsa";
256 	ctx->cert->sig->encoding = "pkcs1";
257 	ctx->sig_algo = ctx->last_oid;
258 	return 0;
259 ecrdsa:
260 	ctx->cert->sig->pkey_algo = "ecrdsa";
261 	ctx->cert->sig->encoding = "raw";
262 	ctx->sig_algo = ctx->last_oid;
263 	return 0;
264 sm2:
265 	ctx->cert->sig->pkey_algo = "sm2";
266 	ctx->cert->sig->encoding = "raw";
267 	ctx->sig_algo = ctx->last_oid;
268 	return 0;
269 ecdsa:
270 	ctx->cert->sig->pkey_algo = "ecdsa";
271 	ctx->cert->sig->encoding = "x962";
272 	ctx->sig_algo = ctx->last_oid;
273 	return 0;
274 }
275 
276 /*
277  * Note the whereabouts and type of the signature.
278  */
279 int x509_note_signature(void *context, size_t hdrlen,
280 			unsigned char tag,
281 			const void *value, size_t vlen)
282 {
283 	struct x509_parse_context *ctx = context;
284 
285 	pr_debug("Signature: alg=%u, size=%zu\n", ctx->last_oid, vlen);
286 
287 	/*
288 	 * In X.509 certificates, the signature's algorithm is stored in two
289 	 * places: inside the TBSCertificate (the data that is signed), and
290 	 * alongside the signature.  These *must* match.
291 	 */
292 	if (ctx->last_oid != ctx->sig_algo) {
293 		pr_warn("signatureAlgorithm (%u) differs from tbsCertificate.signature (%u)\n",
294 			ctx->last_oid, ctx->sig_algo);
295 		return -EINVAL;
296 	}
297 
298 	if (strcmp(ctx->cert->sig->pkey_algo, "rsa") == 0 ||
299 	    strcmp(ctx->cert->sig->pkey_algo, "ecrdsa") == 0 ||
300 	    strcmp(ctx->cert->sig->pkey_algo, "sm2") == 0 ||
301 	    strcmp(ctx->cert->sig->pkey_algo, "ecdsa") == 0) {
302 		/* Discard the BIT STRING metadata */
303 		if (vlen < 1 || *(const u8 *)value != 0)
304 			return -EBADMSG;
305 
306 		value++;
307 		vlen--;
308 	}
309 
310 	ctx->cert->raw_sig = value;
311 	ctx->cert->raw_sig_size = vlen;
312 	return 0;
313 }
314 
315 /*
316  * Note the certificate serial number
317  */
318 int x509_note_serial(void *context, size_t hdrlen,
319 		     unsigned char tag,
320 		     const void *value, size_t vlen)
321 {
322 	struct x509_parse_context *ctx = context;
323 	ctx->cert->raw_serial = value;
324 	ctx->cert->raw_serial_size = vlen;
325 	return 0;
326 }
327 
328 /*
329  * Note some of the name segments from which we'll fabricate a name.
330  */
331 int x509_extract_name_segment(void *context, size_t hdrlen,
332 			      unsigned char tag,
333 			      const void *value, size_t vlen)
334 {
335 	struct x509_parse_context *ctx = context;
336 
337 	switch (ctx->last_oid) {
338 	case OID_commonName:
339 		ctx->cn_size = vlen;
340 		ctx->cn_offset = (unsigned long)value - ctx->data;
341 		break;
342 	case OID_organizationName:
343 		ctx->o_size = vlen;
344 		ctx->o_offset = (unsigned long)value - ctx->data;
345 		break;
346 	case OID_email_address:
347 		ctx->email_size = vlen;
348 		ctx->email_offset = (unsigned long)value - ctx->data;
349 		break;
350 	default:
351 		break;
352 	}
353 
354 	return 0;
355 }
356 
357 /*
358  * Fabricate and save the issuer and subject names
359  */
360 static int x509_fabricate_name(struct x509_parse_context *ctx, size_t hdrlen,
361 			       unsigned char tag,
362 			       char **_name, size_t vlen)
363 {
364 	const void *name, *data = (const void *)ctx->data;
365 	size_t namesize;
366 	char *buffer;
367 
368 	if (*_name)
369 		return -EINVAL;
370 
371 	/* Empty name string if no material */
372 	if (!ctx->cn_size && !ctx->o_size && !ctx->email_size) {
373 		buffer = kmalloc(1, GFP_KERNEL);
374 		if (!buffer)
375 			return -ENOMEM;
376 		buffer[0] = 0;
377 		goto done;
378 	}
379 
380 	if (ctx->cn_size && ctx->o_size) {
381 		/* Consider combining O and CN, but use only the CN if it is
382 		 * prefixed by the O, or a significant portion thereof.
383 		 */
384 		namesize = ctx->cn_size;
385 		name = data + ctx->cn_offset;
386 		if (ctx->cn_size >= ctx->o_size &&
387 		    memcmp(data + ctx->cn_offset, data + ctx->o_offset,
388 			   ctx->o_size) == 0)
389 			goto single_component;
390 		if (ctx->cn_size >= 7 &&
391 		    ctx->o_size >= 7 &&
392 		    memcmp(data + ctx->cn_offset, data + ctx->o_offset, 7) == 0)
393 			goto single_component;
394 
395 		buffer = kmalloc(ctx->o_size + 2 + ctx->cn_size + 1,
396 				 GFP_KERNEL);
397 		if (!buffer)
398 			return -ENOMEM;
399 
400 		memcpy(buffer,
401 		       data + ctx->o_offset, ctx->o_size);
402 		buffer[ctx->o_size + 0] = ':';
403 		buffer[ctx->o_size + 1] = ' ';
404 		memcpy(buffer + ctx->o_size + 2,
405 		       data + ctx->cn_offset, ctx->cn_size);
406 		buffer[ctx->o_size + 2 + ctx->cn_size] = 0;
407 		goto done;
408 
409 	} else if (ctx->cn_size) {
410 		namesize = ctx->cn_size;
411 		name = data + ctx->cn_offset;
412 	} else if (ctx->o_size) {
413 		namesize = ctx->o_size;
414 		name = data + ctx->o_offset;
415 	} else {
416 		namesize = ctx->email_size;
417 		name = data + ctx->email_offset;
418 	}
419 
420 single_component:
421 	buffer = kmalloc(namesize + 1, GFP_KERNEL);
422 	if (!buffer)
423 		return -ENOMEM;
424 	memcpy(buffer, name, namesize);
425 	buffer[namesize] = 0;
426 
427 done:
428 	*_name = buffer;
429 	ctx->cn_size = 0;
430 	ctx->o_size = 0;
431 	ctx->email_size = 0;
432 	return 0;
433 }
434 
435 int x509_note_issuer(void *context, size_t hdrlen,
436 		     unsigned char tag,
437 		     const void *value, size_t vlen)
438 {
439 	struct x509_parse_context *ctx = context;
440 	struct asymmetric_key_id *kid;
441 
442 	ctx->cert->raw_issuer = value;
443 	ctx->cert->raw_issuer_size = vlen;
444 
445 	if (!ctx->cert->sig->auth_ids[2]) {
446 		kid = asymmetric_key_generate_id(value, vlen, "", 0);
447 		if (IS_ERR(kid))
448 			return PTR_ERR(kid);
449 		ctx->cert->sig->auth_ids[2] = kid;
450 	}
451 
452 	return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->issuer, vlen);
453 }
454 
455 int x509_note_subject(void *context, size_t hdrlen,
456 		      unsigned char tag,
457 		      const void *value, size_t vlen)
458 {
459 	struct x509_parse_context *ctx = context;
460 	ctx->cert->raw_subject = value;
461 	ctx->cert->raw_subject_size = vlen;
462 	return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->subject, vlen);
463 }
464 
465 /*
466  * Extract the parameters for the public key
467  */
468 int x509_note_params(void *context, size_t hdrlen,
469 		     unsigned char tag,
470 		     const void *value, size_t vlen)
471 {
472 	struct x509_parse_context *ctx = context;
473 
474 	/*
475 	 * AlgorithmIdentifier is used three times in the x509, we should skip
476 	 * first and ignore third, using second one which is after subject and
477 	 * before subjectPublicKey.
478 	 */
479 	if (!ctx->cert->raw_subject || ctx->key)
480 		return 0;
481 	ctx->params = value - hdrlen;
482 	ctx->params_size = vlen + hdrlen;
483 	return 0;
484 }
485 
486 /*
487  * Extract the data for the public key algorithm
488  */
489 int x509_extract_key_data(void *context, size_t hdrlen,
490 			  unsigned char tag,
491 			  const void *value, size_t vlen)
492 {
493 	struct x509_parse_context *ctx = context;
494 	enum OID oid;
495 
496 	ctx->key_algo = ctx->last_oid;
497 	switch (ctx->last_oid) {
498 	case OID_rsaEncryption:
499 		ctx->cert->pub->pkey_algo = "rsa";
500 		break;
501 	case OID_gost2012PKey256:
502 	case OID_gost2012PKey512:
503 		ctx->cert->pub->pkey_algo = "ecrdsa";
504 		break;
505 	case OID_sm2:
506 		ctx->cert->pub->pkey_algo = "sm2";
507 		break;
508 	case OID_id_ecPublicKey:
509 		if (parse_OID(ctx->params, ctx->params_size, &oid) != 0)
510 			return -EBADMSG;
511 
512 		switch (oid) {
513 		case OID_sm2:
514 			ctx->cert->pub->pkey_algo = "sm2";
515 			break;
516 		case OID_id_prime192v1:
517 			ctx->cert->pub->pkey_algo = "ecdsa-nist-p192";
518 			break;
519 		case OID_id_prime256v1:
520 			ctx->cert->pub->pkey_algo = "ecdsa-nist-p256";
521 			break;
522 		case OID_id_ansip384r1:
523 			ctx->cert->pub->pkey_algo = "ecdsa-nist-p384";
524 			break;
525 		default:
526 			return -ENOPKG;
527 		}
528 		break;
529 	default:
530 		return -ENOPKG;
531 	}
532 
533 	/* Discard the BIT STRING metadata */
534 	if (vlen < 1 || *(const u8 *)value != 0)
535 		return -EBADMSG;
536 	ctx->key = value + 1;
537 	ctx->key_size = vlen - 1;
538 	return 0;
539 }
540 
541 /* The keyIdentifier in AuthorityKeyIdentifier SEQUENCE is tag(CONT,PRIM,0) */
542 #define SEQ_TAG_KEYID (ASN1_CONT << 6)
543 
544 /*
545  * Process certificate extensions that are used to qualify the certificate.
546  */
547 int x509_process_extension(void *context, size_t hdrlen,
548 			   unsigned char tag,
549 			   const void *value, size_t vlen)
550 {
551 	struct x509_parse_context *ctx = context;
552 	struct asymmetric_key_id *kid;
553 	const unsigned char *v = value;
554 
555 	pr_debug("Extension: %u\n", ctx->last_oid);
556 
557 	if (ctx->last_oid == OID_subjectKeyIdentifier) {
558 		/* Get hold of the key fingerprint */
559 		if (ctx->cert->skid || vlen < 3)
560 			return -EBADMSG;
561 		if (v[0] != ASN1_OTS || v[1] != vlen - 2)
562 			return -EBADMSG;
563 		v += 2;
564 		vlen -= 2;
565 
566 		ctx->cert->raw_skid_size = vlen;
567 		ctx->cert->raw_skid = v;
568 		kid = asymmetric_key_generate_id(v, vlen, "", 0);
569 		if (IS_ERR(kid))
570 			return PTR_ERR(kid);
571 		ctx->cert->skid = kid;
572 		pr_debug("subjkeyid %*phN\n", kid->len, kid->data);
573 		return 0;
574 	}
575 
576 	if (ctx->last_oid == OID_keyUsage) {
577 		/*
578 		 * Get hold of the keyUsage bit string
579 		 * v[1] is the encoding size
580 		 *       (Expect either 0x02 or 0x03, making it 1 or 2 bytes)
581 		 * v[2] is the number of unused bits in the bit string
582 		 *       (If >= 3 keyCertSign is missing when v[1] = 0x02)
583 		 * v[3] and possibly v[4] contain the bit string
584 		 *
585 		 * From RFC 5280 4.2.1.3:
586 		 *   0x04 is where keyCertSign lands in this bit string
587 		 *   0x80 is where digitalSignature lands in this bit string
588 		 */
589 		if (v[0] != ASN1_BTS)
590 			return -EBADMSG;
591 		if (vlen < 4)
592 			return -EBADMSG;
593 		if (v[2] >= 8)
594 			return -EBADMSG;
595 		if (v[3] & 0x80)
596 			ctx->cert->pub->key_eflags |= 1 << KEY_EFLAG_DIGITALSIG;
597 		if (v[1] == 0x02 && v[2] <= 2 && (v[3] & 0x04))
598 			ctx->cert->pub->key_eflags |= 1 << KEY_EFLAG_KEYCERTSIGN;
599 		else if (vlen > 4 && v[1] == 0x03 && (v[3] & 0x04))
600 			ctx->cert->pub->key_eflags |= 1 << KEY_EFLAG_KEYCERTSIGN;
601 		return 0;
602 	}
603 
604 	if (ctx->last_oid == OID_authorityKeyIdentifier) {
605 		/* Get hold of the CA key fingerprint */
606 		ctx->raw_akid = v;
607 		ctx->raw_akid_size = vlen;
608 		return 0;
609 	}
610 
611 	if (ctx->last_oid == OID_basicConstraints) {
612 		/*
613 		 * Get hold of the basicConstraints
614 		 * v[1] is the encoding size
615 		 *	(Expect 0x2 or greater, making it 1 or more bytes)
616 		 * v[2] is the encoding type
617 		 *	(Expect an ASN1_BOOL for the CA)
618 		 * v[3] is the contents of the ASN1_BOOL
619 		 *      (Expect 1 if the CA is TRUE)
620 		 * vlen should match the entire extension size
621 		 */
622 		if (v[0] != (ASN1_CONS_BIT | ASN1_SEQ))
623 			return -EBADMSG;
624 		if (vlen < 2)
625 			return -EBADMSG;
626 		if (v[1] != vlen - 2)
627 			return -EBADMSG;
628 		if (vlen >= 4 && v[1] != 0 && v[2] == ASN1_BOOL && v[3] == 1)
629 			ctx->cert->pub->key_eflags |= 1 << KEY_EFLAG_CA;
630 		return 0;
631 	}
632 
633 	return 0;
634 }
635 
636 /**
637  * x509_decode_time - Decode an X.509 time ASN.1 object
638  * @_t: The time to fill in
639  * @hdrlen: The length of the object header
640  * @tag: The object tag
641  * @value: The object value
642  * @vlen: The size of the object value
643  *
644  * Decode an ASN.1 universal time or generalised time field into a struct the
645  * kernel can handle and check it for validity.  The time is decoded thus:
646  *
647  *	[RFC5280 §4.1.2.5]
648  *	CAs conforming to this profile MUST always encode certificate validity
649  *	dates through the year 2049 as UTCTime; certificate validity dates in
650  *	2050 or later MUST be encoded as GeneralizedTime.  Conforming
651  *	applications MUST be able to process validity dates that are encoded in
652  *	either UTCTime or GeneralizedTime.
653  */
654 int x509_decode_time(time64_t *_t,  size_t hdrlen,
655 		     unsigned char tag,
656 		     const unsigned char *value, size_t vlen)
657 {
658 	static const unsigned char month_lengths[] = { 31, 28, 31, 30, 31, 30,
659 						       31, 31, 30, 31, 30, 31 };
660 	const unsigned char *p = value;
661 	unsigned year, mon, day, hour, min, sec, mon_len;
662 
663 #define dec2bin(X) ({ unsigned char x = (X) - '0'; if (x > 9) goto invalid_time; x; })
664 #define DD2bin(P) ({ unsigned x = dec2bin(P[0]) * 10 + dec2bin(P[1]); P += 2; x; })
665 
666 	if (tag == ASN1_UNITIM) {
667 		/* UTCTime: YYMMDDHHMMSSZ */
668 		if (vlen != 13)
669 			goto unsupported_time;
670 		year = DD2bin(p);
671 		if (year >= 50)
672 			year += 1900;
673 		else
674 			year += 2000;
675 	} else if (tag == ASN1_GENTIM) {
676 		/* GenTime: YYYYMMDDHHMMSSZ */
677 		if (vlen != 15)
678 			goto unsupported_time;
679 		year = DD2bin(p) * 100 + DD2bin(p);
680 		if (year >= 1950 && year <= 2049)
681 			goto invalid_time;
682 	} else {
683 		goto unsupported_time;
684 	}
685 
686 	mon  = DD2bin(p);
687 	day = DD2bin(p);
688 	hour = DD2bin(p);
689 	min  = DD2bin(p);
690 	sec  = DD2bin(p);
691 
692 	if (*p != 'Z')
693 		goto unsupported_time;
694 
695 	if (year < 1970 ||
696 	    mon < 1 || mon > 12)
697 		goto invalid_time;
698 
699 	mon_len = month_lengths[mon - 1];
700 	if (mon == 2) {
701 		if (year % 4 == 0) {
702 			mon_len = 29;
703 			if (year % 100 == 0) {
704 				mon_len = 28;
705 				if (year % 400 == 0)
706 					mon_len = 29;
707 			}
708 		}
709 	}
710 
711 	if (day < 1 || day > mon_len ||
712 	    hour > 24 || /* ISO 8601 permits 24:00:00 as midnight tomorrow */
713 	    min > 59 ||
714 	    sec > 60) /* ISO 8601 permits leap seconds [X.680 46.3] */
715 		goto invalid_time;
716 
717 	*_t = mktime64(year, mon, day, hour, min, sec);
718 	return 0;
719 
720 unsupported_time:
721 	pr_debug("Got unsupported time [tag %02x]: '%*phN'\n",
722 		 tag, (int)vlen, value);
723 	return -EBADMSG;
724 invalid_time:
725 	pr_debug("Got invalid time [tag %02x]: '%*phN'\n",
726 		 tag, (int)vlen, value);
727 	return -EBADMSG;
728 }
729 EXPORT_SYMBOL_GPL(x509_decode_time);
730 
731 int x509_note_not_before(void *context, size_t hdrlen,
732 			 unsigned char tag,
733 			 const void *value, size_t vlen)
734 {
735 	struct x509_parse_context *ctx = context;
736 	return x509_decode_time(&ctx->cert->valid_from, hdrlen, tag, value, vlen);
737 }
738 
739 int x509_note_not_after(void *context, size_t hdrlen,
740 			unsigned char tag,
741 			const void *value, size_t vlen)
742 {
743 	struct x509_parse_context *ctx = context;
744 	return x509_decode_time(&ctx->cert->valid_to, hdrlen, tag, value, vlen);
745 }
746 
747 /*
748  * Note a key identifier-based AuthorityKeyIdentifier
749  */
750 int x509_akid_note_kid(void *context, size_t hdrlen,
751 		       unsigned char tag,
752 		       const void *value, size_t vlen)
753 {
754 	struct x509_parse_context *ctx = context;
755 	struct asymmetric_key_id *kid;
756 
757 	pr_debug("AKID: keyid: %*phN\n", (int)vlen, value);
758 
759 	if (ctx->cert->sig->auth_ids[1])
760 		return 0;
761 
762 	kid = asymmetric_key_generate_id(value, vlen, "", 0);
763 	if (IS_ERR(kid))
764 		return PTR_ERR(kid);
765 	pr_debug("authkeyid %*phN\n", kid->len, kid->data);
766 	ctx->cert->sig->auth_ids[1] = kid;
767 	return 0;
768 }
769 
770 /*
771  * Note a directoryName in an AuthorityKeyIdentifier
772  */
773 int x509_akid_note_name(void *context, size_t hdrlen,
774 			unsigned char tag,
775 			const void *value, size_t vlen)
776 {
777 	struct x509_parse_context *ctx = context;
778 
779 	pr_debug("AKID: name: %*phN\n", (int)vlen, value);
780 
781 	ctx->akid_raw_issuer = value;
782 	ctx->akid_raw_issuer_size = vlen;
783 	return 0;
784 }
785 
786 /*
787  * Note a serial number in an AuthorityKeyIdentifier
788  */
789 int x509_akid_note_serial(void *context, size_t hdrlen,
790 			  unsigned char tag,
791 			  const void *value, size_t vlen)
792 {
793 	struct x509_parse_context *ctx = context;
794 	struct asymmetric_key_id *kid;
795 
796 	pr_debug("AKID: serial: %*phN\n", (int)vlen, value);
797 
798 	if (!ctx->akid_raw_issuer || ctx->cert->sig->auth_ids[0])
799 		return 0;
800 
801 	kid = asymmetric_key_generate_id(value,
802 					 vlen,
803 					 ctx->akid_raw_issuer,
804 					 ctx->akid_raw_issuer_size);
805 	if (IS_ERR(kid))
806 		return PTR_ERR(kid);
807 
808 	pr_debug("authkeyid %*phN\n", kid->len, kid->data);
809 	ctx->cert->sig->auth_ids[0] = kid;
810 	return 0;
811 }
812