1 \ Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
3 \ Permission is hereby granted, free of charge, to any person obtaining
4 \ a copy of this software and associated documentation files (the
5 \ "Software"), to deal in the Software without restriction, including
6 \ without limitation the rights to use, copy, modify, merge, publish,
7 \ distribute, sublicense, and/or sell copies of the Software, and to
8 \ permit persons to whom the Software is furnished to do so, subject to
9 \ the following conditions:
11 \ The above copyright notice and this permission notice shall be
12 \ included in all copies or substantial portions of the Software.
14 \ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
15 \ EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
16 \ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
17 \ NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
18 \ BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
19 \ ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
20 \ CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
28 * Implementation Notes
29 * --------------------
31 * The C code pushes the data by chunks; all decoding is done in the
32 * T0 code. The cert_length value is set to the certificate length when
33 * a new certificate is started; the T0 code picks it up as outer limit,
34 * and decoding functions use it to ensure that no attempt is made at
35 * reading past it. The T0 code also checks that once the certificate is
36 * decoded, there are no trailing bytes.
38 * The T0 code sets cert_length to 0 when the certificate is fully
41 * The C code must still perform two checks:
43 * -- If the certificate length is 0, then the T0 code will not be
44 * invoked at all. This invalid condition must thus be reported by the
47 * -- When reaching the end of certificate, the C code must verify that
48 * the certificate length has been set to 0, thereby signaling that
49 * the T0 code properly decoded a certificate.
51 * Processing of a chain works in the following way:
53 * -- The error flag is set to a non-zero value when validation is
54 * finished. The value is either BR_ERR_X509_OK (validation is
55 * successful) or another non-zero error code. When a non-zero error
56 * code is obtained, the remaining bytes in the current certificate and
57 * the subsequent certificates (if any) are completely ignored.
59 * -- Each certificate is decoded in due course, with the following
60 * "interesting points":
62 * -- Start of the TBS: the multihash engine is reset and activated.
64 * -- Start of the issuer DN: the secondary hash engine is started,
65 * to process the encoded issuer DN.
67 * -- End of the issuer DN: the secondary hash engine is stopped. The
68 * resulting hash value is computed and then copied into the
69 * next_dn_hash[] buffer.
71 * -- Start of the subject DN: the secondary hash engine is started,
72 * to process the encoded subject DN.
74 * -- For the EE certificate only: the Common Name, if any, is matched
75 * against the expected server name.
77 * -- End of the subject DN: the secondary hash engine is stopped. The
78 * resulting hash value is computed into the pad. It is then processed:
80 * -- If this is the EE certificate, then the hash is ignored
81 * (except for direct trust processing, see later; the hash is
82 * simply left in current_dn_hash[]).
84 * -- Otherwise, the hashed subject DN is compared with the saved
85 * hash value (in saved_dn_hash[]). They must match.
87 * Either way, the next_dn_hash[] value is then copied into the
88 * saved_dn_hash[] value. Thus, at that point, saved_dn_hash[]
89 * contains the hash of the issuer DN for the current certificate,
90 * and current_dn_hash[] contains the hash of the subject DN for the
91 * current certificate.
93 * -- Public key: it is decoded into the cert_pkey[] buffer. Unknown
94 * key types are reported at that point.
96 * -- If this is the EE certificate, then the key type is compared
97 * with the expected key type (initialization parameter). The public
98 * key data is copied to ee_pkey_data[]. The key and hashed subject
99 * DN are also compared with the "direct trust" keys; if the key
100 * and DN are matched, then validation ends with a success.
102 * -- Otherwise, the saved signature (cert_sig[]) is verified
103 * against the saved TBS hash (tbs_hash[]) and that freshly
104 * decoded public key. Failure here ends validation with an error.
106 * -- Extensions: extension values are processed in due order.
108 * -- Basic Constraints: for all certificates except EE, must be
109 * present, indicate a CA, and have a path legnth compatible with
110 * the chain length so far.
112 * -- Key Usage: for the EE, if present, must allow signatures
113 * or encryption/key exchange, as required for the cipher suite.
114 * For non-EE, if present, must have the "certificate sign" bit.
116 * -- Subject Alt Name: for the EE, dNSName names are matched
117 * against the server name. Ignored for non-EE.
119 * -- Authority Key Identifier, Subject Key Identifier, Issuer
120 * Alt Name, Subject Directory Attributes, CRL Distribution Points
121 * Freshest CRL, Authority Info Access and Subject Info Access
122 * extensions are always ignored: they either contain only
123 * informative data, or they relate to revocation processing, which
124 * we explicitly do not support.
126 * -- All other extensions are ignored if non-critical. If a
127 * critical extension other than the ones above is encountered,
128 * then a failure is reported.
130 * -- End of the TBS: the multihash engine is stopped.
132 * -- Signature algorithm: the signature algorithm on the
133 * certificate is decoded. A failure is reported if that algorithm
134 * is unknown. The hashed TBS corresponding to the signature hash
135 * function is computed and stored in tbs_hash[] (if not supported,
136 * then a failure is reported). The hash OID and length are stored
137 * in cert_sig_hash_oid and cert_sig_hash_len.
139 * -- Signature value: the signature value is copied into the
142 * -- Certificate end: the hashed issuer DN (saved_dn_hash[]) is
143 * looked up in the trust store (CA trust anchors only); for all
144 * that match, the signature (cert_sig[]) is verified against the
145 * anchor public key (hashed TBS is in tbs_hash[]). If one of these
146 * signatures is valid, then validation ends with a success.
148 * -- If the chain end is reached without obtaining a validation success,
149 * then validation is reported as failed.
152 #ifndef BR_USE_UNIX_TIME
153 #if defined __unix__ || defined __linux__ \
154 || defined _POSIX_SOURCE || defined _POSIX_C_SOURCE \
155 || (defined __APPLE__ && defined __MACH__)
156 #define BR_USE_UNIX_TIME 1
160 #ifndef BR_USE_WIN32_TIME
161 #if defined _WIN32 || defined _WIN64
162 #define BR_USE_WIN32_TIME 1
170 #if BR_USE_WIN32_TIME
174 void br_x509_minimal_init_main(void *ctx);
175 void br_x509_minimal_run(void *ctx);
177 /* see bearssl_x509.h */
179 br_x509_minimal_init(br_x509_minimal_context *ctx,
180 const br_hash_class *dn_hash_impl,
181 const br_x509_trust_anchor *trust_anchors, size_t trust_anchors_num)
183 memset(ctx, 0, sizeof *ctx);
184 ctx->vtable = &br_x509_minimal_vtable;
185 ctx->dn_hash_impl = dn_hash_impl;
186 ctx->trust_anchors = trust_anchors;
187 ctx->trust_anchors_num = trust_anchors_num;
191 xm_start_chain(const br_x509_class **ctx, const char *server_name)
193 br_x509_minimal_context *cc;
195 cc = (br_x509_minimal_context *)ctx;
196 memset(&cc->pkey, 0, sizeof cc->pkey);
199 cc->cpu.dp = cc->dp_stack;
200 cc->cpu.rp = cc->rp_stack;
201 br_x509_minimal_init_main(&cc->cpu);
202 if (server_name == NULL || *server_name == 0) {
203 cc->server_name = NULL;
205 cc->server_name = server_name;
210 xm_start_cert(const br_x509_class **ctx, uint32_t length)
212 br_x509_minimal_context *cc;
214 cc = (br_x509_minimal_context *)ctx;
219 cc->err = BR_ERR_X509_TRUNCATED;
222 cc->cert_length = length;
226 xm_append(const br_x509_class **ctx, const unsigned char *buf, size_t len)
228 br_x509_minimal_context *cc;
230 cc = (br_x509_minimal_context *)ctx;
236 br_x509_minimal_run(&cc->cpu);
240 xm_end_cert(const br_x509_class **ctx)
242 br_x509_minimal_context *cc;
244 cc = (br_x509_minimal_context *)ctx;
245 if (cc->err == 0 && cc->cert_length != 0) {
246 cc->err = BR_ERR_X509_TRUNCATED;
252 xm_end_chain(const br_x509_class **ctx)
254 br_x509_minimal_context *cc;
256 cc = (br_x509_minimal_context *)ctx;
258 if (cc->num_certs == 0) {
259 cc->err = BR_ERR_X509_EMPTY_CHAIN;
261 cc->err = BR_ERR_X509_NOT_TRUSTED;
263 } else if (cc->err == BR_ERR_X509_OK) {
266 return (unsigned)cc->err;
269 static const br_x509_pkey *
270 xm_get_pkey(const br_x509_class *const *ctx, unsigned *usages)
272 br_x509_minimal_context *cc;
274 cc = (br_x509_minimal_context *)ctx;
275 if (cc->err == BR_ERR_X509_OK
276 || cc->err == BR_ERR_X509_NOT_TRUSTED)
278 if (usages != NULL) {
279 *usages = cc->key_usages;
281 return &((br_x509_minimal_context *)ctx)->pkey;
287 /* see bearssl_x509.h */
288 const br_x509_class br_x509_minimal_vtable = {
289 sizeof(br_x509_minimal_context),
298 #define CTX ((br_x509_minimal_context *)((unsigned char *)t0ctx - offsetof(br_x509_minimal_context, cpu)))
299 #define CONTEXT_NAME br_x509_minimal_context
301 #define DNHASH_LEN ((CTX->dn_hash_impl->desc >> BR_HASHDESC_OUT_OFF) & BR_HASHDESC_OUT_MASK)
304 * Hash a DN (from a trust anchor) into the provided buffer. This uses the
305 * DN hash implementation and context structure from the X.509 engine
309 hash_dn(br_x509_minimal_context *ctx, const void *dn, size_t len,
312 ctx->dn_hash_impl->init(&ctx->dn_hash.vtable);
313 ctx->dn_hash_impl->update(&ctx->dn_hash.vtable, dn, len);
314 ctx->dn_hash_impl->out(&ctx->dn_hash.vtable, out);
318 * Compare two big integers for equality. The integers use unsigned big-endian
319 * encoding; extra leading bytes (of value 0) are allowed.
322 eqbigint(const unsigned char *b1, size_t len1,
323 const unsigned char *b2, size_t len2)
325 while (len1 > 0 && *b1 == 0) {
329 while (len2 > 0 && *b2 == 0) {
336 return memcmp(b1, b2, len1) == 0;
340 * Verify the signature on the certificate with the provided public key.
341 * This function checks the public key type with regards to the expected
342 * type. Returned value is either 0 on success, or a non-zero error code.
345 verify_signature(br_x509_minimal_context *ctx, const br_x509_pkey *pk)
349 kt = ctx->cert_signer_key_type;
350 if ((pk->key_type & 0x0F) != kt) {
351 return BR_ERR_X509_WRONG_KEY_TYPE;
354 unsigned char tmp[64];
357 if (ctx->irsa == 0) {
358 return BR_ERR_X509_UNSUPPORTED;
360 if (!ctx->irsa(ctx->cert_sig, ctx->cert_sig_len,
361 &t0_datablock[ctx->cert_sig_hash_oid],
362 ctx->cert_sig_hash_len, &pk->key.rsa, tmp))
364 return BR_ERR_X509_BAD_SIGNATURE;
366 if (memcmp(ctx->tbs_hash, tmp, ctx->cert_sig_hash_len) != 0) {
367 return BR_ERR_X509_BAD_SIGNATURE;
372 if (ctx->iecdsa == 0) {
373 return BR_ERR_X509_UNSUPPORTED;
375 if (!ctx->iecdsa(ctx->iec, ctx->tbs_hash,
376 ctx->cert_sig_hash_len, &pk->key.ec,
377 ctx->cert_sig, ctx->cert_sig_len))
379 return BR_ERR_X509_BAD_SIGNATURE;
384 return BR_ERR_X509_UNSUPPORTED;
389 * Compare two strings for equality, in a case-insensitive way. This
390 * function handles casing only for ASCII letters.
393 eqnocase(const void *s1, const void *s2, size_t len)
395 const unsigned char *buf1, *buf2;
404 if (x1 >= 'A' && x1 <= 'Z') {
407 if (x2 >= 'A' && x2 <= 'Z') {
419 cc: read8-low ( -- x ) {
420 if (CTX->hlen == 0) {
423 unsigned char x = *CTX->hbuf ++;
425 br_multihash_update(&CTX->mhash, &x, 1);
427 if (CTX->do_dn_hash) {
428 CTX->dn_hash_impl->update(&CTX->dn_hash.vtable, &x, 1);
438 cc: read-blob-inner ( addr len -- addr len ) {
439 uint32_t len = T0_POP();
440 uint32_t addr = T0_POP();
441 size_t clen = CTX->hlen;
446 memcpy((unsigned char *)CTX + addr, CTX->hbuf, clen);
449 br_multihash_update(&CTX->mhash, CTX->hbuf, clen);
451 if (CTX->do_dn_hash) {
452 CTX->dn_hash_impl->update(
453 &CTX->dn_hash.vtable, CTX->hbuf, clen);
457 T0_PUSH(addr + clen);
461 \ Compute the TBS hash, using the provided hash ID. The hash value is
462 \ written in the tbs_hash[] array, and the hash length is returned. If
463 \ the requested hash function is not supported, then 0 is returned.
464 cc: compute-tbs-hash ( id -- hashlen ) {
467 len = br_multihash_out(&CTX->mhash, id, CTX->tbs_hash);
471 \ Push true (-1) if no server name is expected in the EE certificate.
472 cc: zero-server-name ( -- bool ) {
473 T0_PUSHi(-(CTX->server_name == NULL));
479 addr: cert_signer_key_type
480 addr: cert_sig_hash_oid
481 addr: cert_sig_hash_len
485 \ Start TBS hash computation. The hash functions are reinitialised.
486 cc: start-tbs-hash ( -- ) {
487 br_multihash_init(&CTX->mhash);
491 \ Stop TBS hash computation.
492 cc: stop-tbs-hash ( -- ) {
496 \ Start DN hash computation.
497 cc: start-dn-hash ( -- ) {
498 CTX->dn_hash_impl->init(&CTX->dn_hash.vtable);
502 \ Terminate DN hash computation and write the DN hash into the
503 \ current_dn_hash buffer.
504 cc: compute-dn-hash ( -- ) {
505 CTX->dn_hash_impl->out(&CTX->dn_hash.vtable, CTX->current_dn_hash);
509 \ Get the length of hash values obtained with the DN hasher.
510 cc: dn-hash-length ( -- len ) {
514 \ Copy data between two areas in the context.
515 cc: blobcopy ( addr-dst addr-src len -- ) {
516 size_t len = T0_POP();
517 unsigned char *src = (unsigned char *)CTX + T0_POP();
518 unsigned char *dst = (unsigned char *)CTX + T0_POP();
519 memcpy(dst, src, len);
522 addr: current_dn_hash
526 \ Read a DN. The normalized DN hash is computed and stored in the
527 \ current_dn_hash. The Common Name is also extracted to the pad, if
528 \ it is present and small enough (255 bytes at most); the CN length is
529 \ then written in pad[0]. If these conditions are not met, then pad[0]
531 : read-DN ( lim -- lim )
532 \ Activate DN hashing.
538 \ Parse the DN structure: it is a SEQUENCE of SET of
539 \ AttributeTypeAndValue. Each AttributeTypeAndValue is a
540 \ SEQUENCE { OBJECT IDENTIFIER, ANY }.
545 read-tag 0x11 check-tag-constructed read-length-open-elt
546 dup ifnot ERR_X509_BAD_DN fail then
551 \ We want to recognize the OID for Common Name,
552 \ but we don't want to use read-OID because we
553 \ need to preserve the pad contents. Instead, we
554 \ use the fact that the encoding for the value of
555 \ id-at-commonName is 55 04 03 (three bytes).
556 read-tag 0x06 check-tag-primitive read-length-open-elt
559 read8 8 << tmp + >tmp
565 \ If this is a Common Name, then we want to copy
566 \ it to the pad, but only if it uses a mono-byte
567 \ encoding (Printable, Teletex or UTF-8).
570 dup dup 0x0C = swap 0x13 = or swap 0x14 = or if
572 read-small-value drop
587 \ Compute DN hash and deactivate DN hashing.
590 \ Get the validation date and time from the context or system.
591 cc: get-system-date ( -- days seconds ) {
592 if (CTX->days == 0 && CTX->seconds == 0) {
594 time_t x = time(NULL);
596 T0_PUSH((uint32_t)(x / 86400) + 719528);
597 T0_PUSH((uint32_t)(x % 86400));
598 #elif BR_USE_WIN32_TIME
602 GetSystemTimeAsFileTime(&ft);
603 x = ((uint64_t)ft.dwHighDateTime << 32)
604 + (uint64_t)ft.dwLowDateTime;
606 T0_PUSH((uint32_t)(x / 86400) + 584754);
607 T0_PUSH((uint32_t)(x % 86400));
609 CTX->err = BR_ERR_X509_TIME_UNKNOWN;
614 T0_PUSH(CTX->seconds);
618 \ Compare two dates (days+seconds) together.
619 : before ( days1 seconds1 days2 seconds2 -- bool )
621 d1 d2 = if s1 s2 < else d1 d2 < then ;
623 : after ( days1 seconds1 days2 seconds2 -- bool )
626 \ Swap the top two elements with the two elements immediately below.
627 : swap2 ( a b c d -- c d a b )
630 \ Match the name in the pad with the expected server name. Returned value
631 \ is true (-1) on match, false (0) otherwise. If there is no expected
632 \ server name, then 0 is returned.
633 \ Match conditions: either an exact match (case insensitive), or a
634 \ wildcard match, if the found name starts with "*.". We only match a
635 \ starting wildcard, and only against a complete DN name component.
636 cc: match-server-name ( -- bool ) {
639 if (CTX->server_name == NULL) {
643 n1 = strlen(CTX->server_name);
645 if (n1 == n2 && eqnocase(&CTX->pad[1], CTX->server_name, n1)) {
649 if (n2 >= 2 && CTX->pad[1] == '*' && CTX->pad[2] == '.') {
653 while (u < n1 && CTX->server_name[u] != '.') {
659 && eqnocase(&CTX->pad[3], CTX->server_name + u, n1))
668 \ Get the address and length for the pkey_data buffer.
669 : addr-len-pkey_data ( -- addr len )
670 CX 0 8191 { offsetof(br_x509_minimal_context, pkey_data) }
671 CX 0 8191 { BR_X509_BUFSIZE_KEY } ;
673 \ Copy the EE public key to the permanent buffer (RSA).
674 cc: copy-ee-rsa-pkey ( nlen elen -- ) {
675 size_t elen = T0_POP();
676 size_t nlen = T0_POP();
677 memcpy(CTX->ee_pkey_data, CTX->pkey_data, nlen + elen);
678 CTX->pkey.key_type = BR_KEYTYPE_RSA;
679 CTX->pkey.key.rsa.n = CTX->ee_pkey_data;
680 CTX->pkey.key.rsa.nlen = nlen;
681 CTX->pkey.key.rsa.e = CTX->ee_pkey_data + nlen;
682 CTX->pkey.key.rsa.elen = elen;
685 \ Copy the EE public key to the permanent buffer (EC).
686 cc: copy-ee-ec-pkey ( curve qlen -- ) {
687 size_t qlen = T0_POP();
688 uint32_t curve = T0_POP();
689 memcpy(CTX->ee_pkey_data, CTX->pkey_data, qlen);
690 CTX->pkey.key_type = BR_KEYTYPE_EC;
691 CTX->pkey.key.ec.curve = curve;
692 CTX->pkey.key.ec.q = CTX->ee_pkey_data;
693 CTX->pkey.key.ec.qlen = qlen;
696 \ Check whether the current certificate (EE) is directly trusted.
697 cc: check-direct-trust ( -- ) {
700 for (u = 0; u < CTX->trust_anchors_num; u ++) {
701 const br_x509_trust_anchor *ta;
702 unsigned char hashed_DN[64];
705 ta = &CTX->trust_anchors[u];
706 if (ta->flags & BR_X509_TA_CA) {
709 hash_dn(CTX, ta->dn.data, ta->dn.len, hashed_DN);
710 if (memcmp(hashed_DN, CTX->current_dn_hash, DNHASH_LEN)) {
713 kt = CTX->pkey.key_type;
714 if ((ta->pkey.key_type & 0x0F) != kt) {
720 if (!eqbigint(CTX->pkey.key.rsa.n,
721 CTX->pkey.key.rsa.nlen,
723 ta->pkey.key.rsa.nlen)
724 || !eqbigint(CTX->pkey.key.rsa.e,
725 CTX->pkey.key.rsa.elen,
727 ta->pkey.key.rsa.elen))
734 if (CTX->pkey.key.ec.curve != ta->pkey.key.ec.curve
735 || CTX->pkey.key.ec.qlen != ta->pkey.key.ec.qlen
736 || memcmp(CTX->pkey.key.ec.q,
738 ta->pkey.key.ec.qlen) != 0)
749 * Direct trust match!
751 CTX->err = BR_ERR_X509_OK;
756 \ Check the signature on the certificate with regards to all trusted CA.
757 \ We use the issuer hash (in saved_dn_hash[]) as CA identifier.
758 cc: check-trust-anchor-CA ( -- ) {
761 for (u = 0; u < CTX->trust_anchors_num; u ++) {
762 const br_x509_trust_anchor *ta;
763 unsigned char hashed_DN[64];
765 ta = &CTX->trust_anchors[u];
766 if (!(ta->flags & BR_X509_TA_CA)) {
769 hash_dn(CTX, ta->dn.data, ta->dn.len, hashed_DN);
770 if (memcmp(hashed_DN, CTX->saved_dn_hash, DNHASH_LEN)) {
773 if (verify_signature(CTX, &ta->pkey) == 0) {
774 CTX->err = BR_ERR_X509_OK;
780 \ Verify RSA signature. This uses the public key that was just decoded
781 \ into CTX->pkey_data; the modulus and exponent length are provided as
782 \ parameters. The resulting hash value is compared with the one in
783 \ tbs_hash. Returned value is 0 on success, or a non-zero error code.
784 cc: do-rsa-vrfy ( nlen elen -- err ) {
785 size_t elen = T0_POP();
786 size_t nlen = T0_POP();
789 pk.key_type = BR_KEYTYPE_RSA;
790 pk.key.rsa.n = CTX->pkey_data;
791 pk.key.rsa.nlen = nlen;
792 pk.key.rsa.e = CTX->pkey_data + nlen;
793 pk.key.rsa.elen = elen;
794 T0_PUSH(verify_signature(CTX, &pk));
797 \ Verify ECDSA signature. This uses the public key that was just decoded
798 \ into CTX->pkey_dayta; the curve ID and public point length are provided
799 \ as parameters. The hash value in tbs_hash is used. Returned value is 0
800 \ on success, or non-zero error code.
801 cc: do-ecdsa-vrfy ( curve qlen -- err ) {
802 size_t qlen = T0_POP();
803 int curve = T0_POP();
806 pk.key_type = BR_KEYTYPE_EC;
807 pk.key.ec.curve = curve;
808 pk.key.ec.q = CTX->pkey_data;
809 pk.key.ec.qlen = qlen;
810 T0_PUSH(verify_signature(CTX, &pk));
813 cc: print-bytes ( addr len -- ) {
814 extern int printf(const char *fmt, ...);
815 size_t len = T0_POP();
816 unsigned char *buf = (unsigned char *)CTX + T0_POP();
819 for (u = 0; u < len; u ++) {
820 printf("%02X", buf[u]);
824 cc: printOID ( -- ) {
825 extern int printf(const char *fmt, ...);
833 printf("%u.%u", CTX->pad[1] / 40, CTX->pad[1] % 40);
847 ul = (ul << 7) + (x & 0x7F);
856 \ Extensions with specific processing.
857 OID: basicConstraints 2.5.29.19
858 OID: keyUsage 2.5.29.15
859 OID: subjectAltName 2.5.29.17
861 \ Extensions which are ignored when encountered, even if critical.
862 OID: authorityKeyIdentifier 2.5.29.35
863 OID: subjectKeyIdentifier 2.5.29.14
864 OID: issuerAltName 2.5.29.18
865 OID: subjectDirectoryAttributes 2.5.29.9
866 OID: crlDistributionPoints 2.5.29.31
867 OID: freshestCRL 2.5.29.46
868 OID: authorityInfoAccess 1.3.6.1.5.5.7.1.1
869 OID: subjectInfoAccess 1.3.6.1.5.5.7.1.11
871 \ Process a Basic Constraints extension. This should be called only if
872 \ the certificate is not the EE. We check that the extension contains
873 \ the "CA" flag, and that the path length, if specified, is compatible
874 \ with the current chain length.
875 : process-basicConstraints ( lim -- lim )
879 read-boolean ifnot ERR_X509_NOT_CA fail then
885 drop check-primitive read-small-int-value
886 addr-num_certs get32 1- < if ERR_X509_NOT_CA fail then
889 -1 <> if ERR_X509_UNEXPECTED fail then
894 \ Process a Key Usage extension.
895 \ For the EE certificate:
896 \ -- if the key usage contains keyEncipherment (2), dataEncipherment (3)
897 \ or keyAgreement (4), then the "key exchange" usage is allowed;
898 \ -- if the key usage contains digitalSignature (0) or nonRepudiation (1),
899 \ then the "signature" usage is allowed.
900 \ For CA certificates, the extension must contain keyCertSign (5).
901 : process-keyUsage ( lim ee -- lim )
904 \ Read tag for the BIT STRING and open it.
905 read-tag 0x03 check-tag-primitive
907 \ First byte indicates number of ignored bits in the last byte. It
908 \ must be between 0 and 7.
910 ign 7 > if ERR_X509_UNEXPECTED fail then
911 \ Depending on length, we have either 0, 1 or more bytes to read.
913 0 of ERR_X509_FORBIDDEN_KEY_USAGE fail endof
914 1 of read8 ign >> ign << endof
922 over 0x38 and if 0x10 or then
923 swap 0xC0 and if 0x20 or then
926 \ Not EE: keyCertSign must be set.
927 0x04 and ifnot ERR_X509_FORBIDDEN_KEY_USAGE fail then
930 \ We don't care about subsequent bytes.
933 \ Process a Subject Alt Name extension. Returned value is a boolean set
934 \ to true if the expected server name was matched against a dNSName in
936 : process-SAN ( lim -- lim bool )
940 \ We check only names of type dNSName; they use IA5String,
941 \ which is basically ASCII.
944 read-small-value drop
945 match-server-name m or >m
947 drop read-length-skip
953 \ Decode a certificate. The "ee" boolean must be true for the EE.
954 : decode-certificate ( ee -- )
957 \ Obtain the total certificate length.
958 addr-cert_length get32
960 \ Open the outer SEQUENCE.
968 \ First element may be an explicit version. We accept only
969 \ versions 0 to 2 (certificates v1 to v3).
970 read-tag dup 0x20 = if
971 drop check-constructed read-length-open-elt
973 0x02 check-tag-primitive
975 2 > if ERR_X509_UNSUPPORTED fail then
980 \ Serial number. We just check that the tag is correct.
981 0x02 check-tag-primitive
984 \ Signature algorithm. This structure is redundant with the one
985 \ on the outside; we just skip it.
986 read-sequence-open skip-close-elt
988 \ Issuer name: hashed, then copied into next_dn_hash[].
990 addr-next_dn_hash addr-current_dn_hash dn-hash-length blobcopy
994 read-date get-system-date after if ERR_X509_EXPIRED fail then
995 read-date get-system-date before if ERR_X509_EXPIRED fail then
1001 \ For the EE, we must check whether the Common Name, if
1002 \ any, matches the expected server name.
1003 match-server-name { eename }
1005 \ For a non-EE certificate, the hashed subject DN must match
1006 \ the saved hashed issuer DN from the previous certificate.
1007 addr-current_dn_hash addr-saved_dn_hash dn-hash-length eqblob
1008 ifnot ERR_X509_DN_MISMATCH fail then
1010 \ Move the hashed issuer DN for this certificate into the
1011 \ saved_dn_hash[] array.
1012 addr-saved_dn_hash addr-next_dn_hash dn-hash-length blobcopy
1016 \ Algorithm Identifier. Right now we are only interested in the
1017 \ OID, since we only support RSA keys.
1019 read-OID ifnot ERR_X509_UNSUPPORTED fail then
1023 rsaEncryption eqOID uf
1025 \ Public key itself: the BIT STRING contains bytes
1026 \ (no partial byte) and these bytes encode the
1029 \ RSA public key is a SEQUENCE of two
1030 \ INTEGER. We get both INTEGER values into
1031 \ the pkey_data[] buffer, if they fit.
1034 read-integer { nlen }
1035 addr-len-pkey_data swap nlen + swap nlen -
1036 read-integer { elen }
1039 \ Check that the public key fits our minimal
1040 \ size requirements. Note that the integer
1041 \ decoder already skipped the leading bytes
1042 \ of value 0, so we are working on the true
1043 \ modulus length here.
1044 addr-min_rsa_size get16 128 + nlen > if
1045 ERR_X509_WEAK_PUBLIC_KEY fail
1048 KEYTYPE_RSA >pkey-type
1052 id-ecPublicKey eqOID uf
1053 \ We support only named curves, for which the
1054 \ "parameters" field in the AlgorithmIdentifier
1055 \ field should be an OID.
1056 read-OID ifnot ERR_X509_UNSUPPORTED fail then
1058 ansix9p256r1 eqOID uf 23 enduf
1059 ansix9p384r1 eqOID uf 24 enduf
1060 ansix9p521r1 eqOID uf 25 enduf
1061 ERR_X509_UNSUPPORTED fail
1067 dup addr-len-pkey_data rot < if
1068 ERR_X509_LIMIT_EXCEEDED fail
1071 KEYTYPE_EC >pkey-type
1074 \ Not a recognised public key type.
1075 ERR_X509_UNSUPPORTED fail
1079 \ Process public key.
1081 \ For the EE certificate, copy the key data to the
1084 KEYTYPE_RSA of nlen elen copy-ee-rsa-pkey endof
1085 KEYTYPE_EC of curve qlen copy-ee-ec-pkey endof
1086 ERR_X509_UNSUPPORTED fail
1089 \ Verify signature on previous certificate. We invoke
1090 \ the RSA implementation.
1092 KEYTYPE_RSA of nlen elen do-rsa-vrfy endof
1093 KEYTYPE_EC of curve qlen do-ecdsa-vrfy endof
1094 ERR_X509_UNSUPPORTED fail
1100 \ This flag will be set to true if the Basic Constraints extension
1104 \ Skip issuerUniqueID and subjectUniqueID, and process extensions
1105 \ if present. Extensions are an explicit context tag of value 3
1106 \ around a SEQUENCE OF extensions. Each extension is a SEQUENCE
1107 \ with an OID, an optional boolean, and a value; the value is
1114 check-constructed read-length-open-elt
1120 read-tag dup 0x01 = if
1121 read-boolean >critical
1124 0x04 check-tag-primitive read-length-open-elt
1126 \ Extensions with specific processing.
1127 basicConstraints eqOID uf
1131 process-basicConstraints
1138 subjectAltName eqOID uf
1147 \ Extensions which are always ignored,
1149 authorityKeyIdentifier eqOID uf
1152 subjectKeyIdentifier eqOID uf
1155 issuerAltName eqOID uf
1158 subjectDirectoryAttributes eqOID uf
1161 crlDistributionPoints eqOID uf
1164 freshestCRL eqOID uf
1167 authorityInfoAccess eqOID uf
1170 subjectInfoAccess eqOID uf
1174 \ Unrecognized extensions trigger a failure
1175 \ if critical; otherwise, they are just
1178 ERR_X509_CRITICAL_EXTENSION fail
1188 -1 = ifnot ERR_X509_UNEXPECTED fail then
1193 \ Terminate hashing.
1196 \ For the EE certificate, verify that the intended server name
1199 eename zero-server-name or ifnot
1200 ERR_X509_BAD_SERVER_NAME fail
1204 \ If this is the EE certificate, then direct trust may apply.
1205 \ Note: we do this at this point, not immediately after decoding
1206 \ the public key, because even in case of direct trust we still
1207 \ want to check the server name with regards to the SAN extension.
1208 \ However, we want to check direct trust before trying to decode
1209 \ the signature algorithm, because it should work even if that
1210 \ algorithm is not supported.
1211 ee if check-direct-trust then
1213 \ Non-EE certificates MUST have a Basic Constraints extension
1214 \ (that marks them as being CA).
1215 ee seenBC or ifnot ERR_X509_NOT_CA fail then
1217 \ signature algorithm
1218 read-tag check-sequence read-length-open-elt
1219 \ Read and understand the OID. Right now, we support only
1220 \ RSA with PKCS#1 v1.5 padding, and hash functions SHA-1,
1221 \ SHA-224, SHA-256, SHA-384 and SHA-512. We purposely do NOT
1223 \ TODO: add support for RSA/PSS
1225 \ Based on the signature OID, we get:
1226 \ -- the signing key type
1227 \ -- the hash function numeric identifier
1228 \ -- the hash function OID
1230 sha1WithRSAEncryption eqOID
1231 uf 2 KEYTYPE_RSA id-sha1 enduf
1232 sha224WithRSAEncryption eqOID
1233 uf 3 KEYTYPE_RSA id-sha224 enduf
1234 sha256WithRSAEncryption eqOID
1235 uf 4 KEYTYPE_RSA id-sha256 enduf
1236 sha384WithRSAEncryption eqOID
1237 uf 5 KEYTYPE_RSA id-sha384 enduf
1238 sha512WithRSAEncryption eqOID
1239 uf 6 KEYTYPE_RSA id-sha512 enduf
1241 ecdsa-with-SHA1 eqOID
1242 uf 2 KEYTYPE_EC id-sha1 enduf
1243 ecdsa-with-SHA224 eqOID
1244 uf 3 KEYTYPE_EC id-sha224 enduf
1245 ecdsa-with-SHA256 eqOID
1246 uf 4 KEYTYPE_EC id-sha256 enduf
1247 ecdsa-with-SHA384 eqOID
1248 uf 5 KEYTYPE_EC id-sha384 enduf
1249 ecdsa-with-SHA512 eqOID
1250 uf 6 KEYTYPE_EC id-sha512 enduf
1251 ERR_X509_UNSUPPORTED fail
1253 addr-cert_sig_hash_oid set16
1254 addr-cert_signer_key_type set8
1256 \ Compute the TBS hash into tbs_hash.
1258 dup ifnot ERR_X509_UNSUPPORTED fail then
1259 addr-cert_sig_hash_len set8
1261 ERR_X509_UNSUPPORTED fail
1263 \ We ignore the parameters, whether they are present or not,
1264 \ because we got all the information from the OID.
1269 dup CX 0 8191 { BR_X509_BUFSIZE_SIG } > if
1270 ERR_X509_LIMIT_EXCEEDED fail
1272 dup addr-cert_sig_len set16
1273 addr-cert_sig read-blob
1275 \ Close the outer SEQUENCE.
1278 \ Close the advertised total certificate length. This checks that
1279 \ there is no trailing garbage after the certificate.
1282 \ Flag the certificate as fully processed.
1283 0 addr-cert_length set32
1285 \ Check whether the issuer for the current certificate is known
1286 \ as a trusted CA; in which case, verify the signature.
1287 check-trust-anchor-CA ;
1290 \ Unless restricted by a Key Usage extension, all usages are
1292 0x30 addr-key_usages set8
1293 -1 decode-certificate
1296 0 decode-certificate co