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
23 \ ----------------------------------------------------------------------
24 \ Handshake processing code, for the server.
25 \ The common T0 code (ssl_hs_common.t0) shall be read first.
30 * This macro evaluates to a pointer to the server context, under that
31 * specific name. It must be noted that since the engine context is the
32 * first field of the br_ssl_server_context structure ('eng'), then
33 * pointers values of both types are interchangeable, modulo an
34 * appropriate cast. This also means that "adresses" computed as offsets
35 * within the structure work for both kinds of context.
37 #define CTX ((br_ssl_server_context *)ENG)
40 * Decrypt the pre-master secret (RSA key exchange).
43 do_rsa_decrypt(br_ssl_server_context *ctx, int prf_id,
44 unsigned char *epms, size_t len)
47 unsigned char rpms[48];
52 x = (*ctx->policy_vtable)->do_keyx(ctx->policy_vtable, epms, &len);
55 * Set the first two bytes to the maximum supported client
56 * protocol version. These bytes are used for version rollback
57 * detection; forceing the two bytes will make the master secret
58 * wrong if the bytes are not correct. This process is
59 * recommended by RFC 5246 (section 7.4.7.1).
61 br_enc16be(epms, ctx->client_max_version);
64 * Make a random PMS and copy it above the decrypted value if the
65 * decryption failed. Note that we use a constant-time conditional
68 br_hmac_drbg_generate(&ctx->eng.rng, rpms, sizeof rpms);
69 br_ccopy(x ^ 1, epms, rpms, sizeof rpms);
72 * Compute master secret.
74 br_ssl_engine_compute_master(&ctx->eng, prf_id, epms, 48);
77 * Clear the pre-master secret from RAM: it is normally a buffer
78 * in the context, hence potentially long-lived.
84 * Common part for ECDH and ECDHE.
87 ecdh_common(br_ssl_server_context *ctx, int prf_id,
88 unsigned char *xcoor, size_t xcoor_len, uint32_t ctl)
90 unsigned char rpms[80];
92 if (xcoor_len > sizeof rpms) {
93 xcoor_len = sizeof rpms;
98 * Make a random PMS and copy it above the decrypted value if the
99 * decryption failed. Note that we use a constant-time conditional
102 br_hmac_drbg_generate(&ctx->eng.rng, rpms, xcoor_len);
103 br_ccopy(ctl ^ 1, xcoor, rpms, xcoor_len);
106 * Compute master secret.
108 br_ssl_engine_compute_master(&ctx->eng, prf_id, xcoor, xcoor_len);
111 * Clear the pre-master secret from RAM: it is normally a buffer
112 * in the context, hence potentially long-lived.
114 memset(xcoor, 0, xcoor_len);
118 * Do the ECDH key exchange (not ECDHE).
121 do_ecdh(br_ssl_server_context *ctx, int prf_id,
122 unsigned char *cpoint, size_t cpoint_len)
127 * Finalise the key exchange.
129 x = (*ctx->policy_vtable)->do_keyx(ctx->policy_vtable,
130 cpoint, &cpoint_len);
131 ecdh_common(ctx, prf_id, cpoint, cpoint_len, x);
135 * Do the full static ECDH key exchange. When this function is called,
136 * it has already been verified that the cipher suite uses ECDH (not ECDHE),
137 * and the client's public key (from its certificate) has type EC and is
138 * apt for key exchange.
141 do_static_ecdh(br_ssl_server_context *ctx, int prf_id)
143 unsigned char cpoint[133];
145 const br_x509_class **xc;
146 const br_x509_pkey *pk;
148 xc = ctx->eng.x509ctx;
149 pk = (*xc)->get_pkey(xc, NULL);
150 cpoint_len = pk->key.ec.qlen;
151 if (cpoint_len > sizeof cpoint) {
153 * If the point is larger than our buffer then we need to
154 * restrict it. Length 2 is not a valid point length, so
155 * the ECDH will fail.
159 memcpy(cpoint, pk->key.ec.q, cpoint_len);
160 do_ecdh(ctx, prf_id, cpoint, cpoint_len);
164 hash_data(br_ssl_server_context *ctx,
165 void *dst, int hash_id, const void *src, size_t len)
167 const br_hash_class *hf;
168 br_hash_compat_context hc;
171 unsigned char tmp[36];
173 hf = br_multihash_getimpl(&ctx->eng.mhash, br_md5_ID);
177 hf->init(&hc.vtable);
178 hf->update(&hc.vtable, src, len);
179 hf->out(&hc.vtable, tmp);
180 hf = br_multihash_getimpl(&ctx->eng.mhash, br_sha1_ID);
184 hf->init(&hc.vtable);
185 hf->update(&hc.vtable, src, len);
186 hf->out(&hc.vtable, tmp + 16);
187 memcpy(dst, tmp, 36);
190 hf = br_multihash_getimpl(&ctx->eng.mhash, hash_id);
194 hf->init(&hc.vtable);
195 hf->update(&hc.vtable, src, len);
196 hf->out(&hc.vtable, dst);
197 return (hf->desc >> BR_HASHDESC_OUT_OFF) & BR_HASHDESC_OUT_MASK;
202 * Do the ECDHE key exchange (part 1: generation of transient key, and
203 * computing of the point to send to the client). Returned value is the
204 * signature length (in bytes), or -x on error (with x being an error
205 * code). The encoded point is written in the ecdhe_point[] context buffer
206 * (length in ecdhe_point_len).
209 do_ecdhe_part1(br_ssl_server_context *ctx, int curve)
213 const unsigned char *order;
215 size_t hv_len, sig_len;
217 if (!((ctx->eng.iec->supported_curves >> curve) & 1)) {
218 return -BR_ERR_INVALID_ALGORITHM;
220 ctx->eng.ecdhe_curve = curve;
223 * Generate our private key. We need a non-zero random value
224 * which is lower than the curve order, in a "large enough"
225 * range. We force the top bit to 0 and bottom bit to 1, which
226 * does the trick. Note that contrary to what happens in ECDSA,
227 * this is not a problem if we do not cover the full range of
230 order = ctx->eng.iec->order(curve, &olen);
232 while (mask >= order[0]) {
235 br_hmac_drbg_generate(&ctx->eng.rng, ctx->ecdhe_key, olen);
236 ctx->ecdhe_key[0] &= mask;
237 ctx->ecdhe_key[olen - 1] |= 0x01;
238 ctx->ecdhe_key_len = olen;
241 * Compute our ECDH point.
243 glen = ctx->eng.iec->mulgen(ctx->eng.ecdhe_point,
244 ctx->ecdhe_key, olen, curve);
245 ctx->eng.ecdhe_point_len = glen;
248 * Assemble the message to be signed, and possibly hash it.
250 memcpy(ctx->eng.pad, ctx->eng.client_random, 32);
251 memcpy(ctx->eng.pad + 32, ctx->eng.server_random, 32);
252 ctx->eng.pad[64 + 0] = 0x03;
253 ctx->eng.pad[64 + 1] = 0x00;
254 ctx->eng.pad[64 + 2] = curve;
255 ctx->eng.pad[64 + 3] = ctx->eng.ecdhe_point_len;
256 memcpy(ctx->eng.pad + 64 + 4,
257 ctx->eng.ecdhe_point, ctx->eng.ecdhe_point_len);
258 hv_len = 64 + 4 + ctx->eng.ecdhe_point_len;
259 algo_id = ctx->sign_hash_id;
260 if (algo_id >= (unsigned)0xFF00) {
261 hv_len = hash_data(ctx, ctx->eng.pad, algo_id & 0xFF,
262 ctx->eng.pad, hv_len);
264 return -BR_ERR_INVALID_ALGORITHM;
268 sig_len = (*ctx->policy_vtable)->do_sign(ctx->policy_vtable,
269 algo_id, ctx->eng.pad, hv_len, sizeof ctx->eng.pad);
270 return sig_len ? (int)sig_len : -BR_ERR_INVALID_ALGORITHM;
274 * Do the ECDHE key exchange (part 2: computation of the shared secret
275 * from the point sent by the client).
278 do_ecdhe_part2(br_ssl_server_context *ctx, int prf_id,
279 unsigned char *cpoint, size_t cpoint_len)
285 curve = ctx->eng.ecdhe_curve;
288 * Finalise the key exchange.
290 ctl = ctx->eng.iec->mul(cpoint, cpoint_len,
291 ctx->ecdhe_key, ctx->ecdhe_key_len, curve);
292 xoff = ctx->eng.iec->xoff(curve, &xlen);
293 ecdh_common(ctx, prf_id, cpoint + xoff, xlen, ctl);
296 * Clear the ECDHE private key. Forward Secrecy is achieved insofar
297 * as that key does not get stolen, so we'd better destroy it
298 * as soon as it ceases to be useful.
300 memset(ctx->ecdhe_key, 0, ctx->ecdhe_key_len);
304 * Offset for hash value within the pad (when obtaining all hash values,
305 * in preparation for verification of the CertificateVerify message).
306 * Order is MD5, SHA-1, SHA-224, SHA-256, SHA-384, SHA-512; last value
307 * is used to get the total length.
309 static const unsigned char HASH_PAD_OFF[] = { 0, 16, 36, 64, 96, 144, 208 };
312 * OID for hash functions in RSA signatures.
314 static const unsigned char HASH_OID_SHA1[] = {
315 0x05, 0x2B, 0x0E, 0x03, 0x02, 0x1A
318 static const unsigned char HASH_OID_SHA224[] = {
319 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x04
322 static const unsigned char HASH_OID_SHA256[] = {
323 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01
326 static const unsigned char HASH_OID_SHA384[] = {
327 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x02
330 static const unsigned char HASH_OID_SHA512[] = {
331 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03
334 static const unsigned char *HASH_OID[] = {
343 * Verify the signature in CertificateVerify. Returned value is 0 on
344 * success, or a non-zero error code. Lack of implementation of the
345 * designated signature algorithm is reported as a "bad signature"
346 * error (because it means that the peer did not honour our advertised
347 * set of supported signature algorithms).
350 verify_CV_sig(br_ssl_server_context *ctx, size_t sig_len)
352 const br_x509_class **xc;
353 const br_x509_pkey *pk;
356 id = ctx->hash_CV_id;
357 xc = ctx->eng.x509ctx;
358 pk = (*xc)->get_pkey(xc, NULL);
359 if (pk->key_type == BR_KEYTYPE_RSA) {
360 unsigned char tmp[64];
361 const unsigned char *hash_oid;
366 hash_oid = HASH_OID[id - 2];
368 if (ctx->eng.irsavrfy == 0) {
369 return BR_ERR_BAD_SIGNATURE;
371 if (!ctx->eng.irsavrfy(ctx->eng.pad, sig_len,
372 hash_oid, ctx->hash_CV_len, &pk->key.rsa, tmp)
373 || memcmp(tmp, ctx->hash_CV, ctx->hash_CV_len) != 0)
375 return BR_ERR_BAD_SIGNATURE;
378 if (ctx->eng.iecdsa == 0) {
379 return BR_ERR_BAD_SIGNATURE;
381 if (!ctx->eng.iecdsa(ctx->eng.iec,
382 ctx->hash_CV, ctx->hash_CV_len,
383 &pk->key.ec, ctx->eng.pad, sig_len))
385 return BR_ERR_BAD_SIGNATURE;
393 \ =======================================================================
397 "addr-" field + 0 1 define-word
398 0 8191 "offsetof(br_ssl_server_context, " field + ")" + make-CX
399 postpone literal postpone ; ;
401 addr-ctx: client_max_version
402 addr-ctx: client_suites
403 addr-ctx: client_suites_num
406 addr-ctx: sign_hash_id
408 \ Get address and length of the client_suites[] buffer. Length is expressed
410 : addr-len-client_suites ( -- addr len )
412 CX 0 1023 { BR_MAX_CIPHER_SUITES * sizeof(br_suite_translated) } ;
414 \ Read the client SNI extension.
415 : read-client-sni ( lim -- lim )
416 \ Open extension value.
419 \ Open ServerNameList.
422 \ Find if there is a name of type 0 (host_name) with a length
423 \ that fits in our dedicated buffer.
430 dup addr-server_name + 0 swap set8
431 addr-server_name swap read-blob
438 \ Close ServerNameList.
441 \ Close extension value.
444 \ Set the new maximum fragment length. BEWARE: this shall be called only
445 \ after reading the ClientHello and before writing the ServerHello.
446 cc: set-max-frag-len ( len -- ) {
447 size_t max_frag_len = T0_POP();
449 br_ssl_engine_new_max_frag_len(ENG, max_frag_len);
452 * We must adjust our own output limit. Since we call this only
453 * after receiving a ClientHello and before beginning to send
454 * the ServerHello, the next output record should be empty at
455 * that point, so we can use max_frag_len as a limit.
457 if (ENG->hlen_out > max_frag_len) {
458 ENG->hlen_out = max_frag_len;
462 \ Read the client Max Frag Length extension.
463 : read-client-frag ( lim -- lim )
464 \ Extension value must have length exactly 1 byte.
465 read16 1 <> if ERR_BAD_FRAGLEN fail then
468 \ The byte value must be 1, 2, 3 or 4.
469 dup dup 0= swap 5 >= or if ERR_BAD_FRAGLEN fail then
471 \ If our own maximum fragment length is greater, then we reduce
473 8 + dup addr-log_max_frag_len get8 < if
474 dup 1 swap << set-max-frag-len
475 dup addr-log_max_frag_len set8
476 addr-peer_log_max_frag_len set8
481 \ Read the Secure Renegotiation extension from the client.
482 : read-client-reneg ( lim -- lim )
486 \ The "reneg" value is one of:
487 \ 0 on first handshake, client support is unknown
488 \ 1 client does not support secure renegotiation
489 \ 2 client supports secure renegotiation
492 \ First handshake, value length shall be 1.
493 1 = ifnot ERR_BAD_SECRENEG fail then
494 read8 if ERR_BAD_SECRENEG fail then
498 \ Renegotiation, value shall consist of 13 bytes
499 \ (header + copy of the saved client "Finished").
500 13 = ifnot ERR_BAD_SECRENEG fail then
501 read8 12 = ifnot ERR_BAD_SECRENEG fail then
502 addr-pad 12 read-blob
503 addr-saved_finished addr-pad 12 memcmp ifnot
504 ERR_BAD_SECRENEG fail
508 \ If "reneg" is 1 then the client is not supposed to support
509 \ the extension, and it sends it nonetheless, which means
511 ERR_BAD_SECRENEG fail
514 \ Read the Signature Algorithms extension.
515 : read-signatures ( lim -- lim )
516 \ Open extension value.
519 read-list-sign-algos addr-hashes set32
521 \ Close extension value.
524 \ Read the Supported Curves extension.
525 : read-supported-curves ( lim -- lim )
526 \ Open extension value.
529 \ Open list of curve identifiers.
532 \ Get all supported curves.
536 1 swap << addr-curves get32 or addr-curves set32
544 \ Read the ALPN extension from client.
545 : read-ALPN-from-client ( lim -- lim )
546 \ If we do not have configured names, then we just ignore the
548 addr-protocol_names_num get16 ifnot read-ignore-16 ret then
550 \ Open extension value.
553 \ Open list of protocol names.
556 \ Get all names and test for their support. We keep the one with
557 \ the lowest index (because we apply server's preferences, as
558 \ recommended by RFC 7301, section 3.2. We set the 'found' variable
559 \ to -2 and use an unsigned comparison, making -2 a huge value.
562 read8 dup { len } addr-pad swap read-blob
563 len test-protocol-name dup found u< if
574 \ Write back found name index (or not). If no match was found,
575 \ then we write -1 (0xFFFF) in the index value, not 0, so that
576 \ the caller knows that we tried to match, and failed.
577 found 1+ addr-selected_protocol set16 ;
579 \ Call policy handler to get cipher suite, hash function identifier and
580 \ certificate chain. Returned value is 0 (false) on failure.
581 cc: call-policy-handler ( -- bool ) {
583 br_ssl_server_choices choices;
585 x = (*CTX->policy_vtable)->choose(
586 CTX->policy_vtable, CTX, &choices);
587 ENG->session.cipher_suite = choices.cipher_suite;
588 CTX->sign_hash_id = choices.algo_id;
589 ENG->chain = choices.chain;
590 ENG->chain_len = choices.chain_len;
594 \ Check for a remembered session.
595 cc: check-resume ( -- bool ) {
596 if (ENG->session.session_id_len == 32
597 && CTX->cache_vtable != NULL && (*CTX->cache_vtable)->load(
598 CTX->cache_vtable, CTX, &ENG->session))
606 \ Save the current session.
607 cc: save-session ( -- ) {
608 if (CTX->cache_vtable != NULL) {
609 (*CTX->cache_vtable)->save(
610 CTX->cache_vtable, CTX, &ENG->session);
614 \ Read ClientHello. If the session is resumed, then -1 is returned.
615 : read-ClientHello ( -- resume )
616 \ Get header, and check message type.
617 read-handshake-header 1 = ifnot ERR_UNEXPECTED fail then
619 \ Get maximum protocol version from client.
620 read16 dup { client-version-max } addr-client_max_version set16
623 addr-client_random 32 read-blob
626 read8 dup 32 > if ERR_OVERSIZED_ID fail then
627 dup addr-session_id_len set8
628 addr-session_id swap read-blob
630 \ Lookup session for resumption. We should do that here because
631 \ we need to verify that the remembered cipher suite is still
632 \ matched by this ClientHello.
633 check-resume { resume }
635 \ Cipher suites. We read all cipher suites from client, each time
636 \ matching against our own list. We accumulate suites in the
637 \ client_suites[] context buffer: we keep suites that are
638 \ supported by both the client and the server (so the list size
639 \ cannot exceed that of the server list), and we keep them in
640 \ either client or server preference order (depending on the
643 \ We also need to identify the pseudo cipher suite for secure
644 \ renegotiation here.
648 addr-len-client_suites dup2 bzero
649 over + { css-off css-max }
654 \ Check that when resuming a session, the requested
655 \ suite is still valid.
657 dup addr-cipher_suite get16 = if
662 \ Special handling for TLS_EMPTY_RENEGOTIATION_INFO_SCSV.
663 \ This fake cipher suite may occur only in the first
666 addr-reneg get8 if ERR_BAD_SECRENEG fail then
670 \ Special handling for TLS_FALLBACK_SCSV. If the client
671 \ maximum version is less than our own maximum version,
672 \ then this is an undue downgrade. We mark it by setting
673 \ the client max version to 0x10000.
675 client-version-max addr-version_min get16 >=
676 client-version-max addr-version_max get16 < and if
677 -1 >client-version-max
681 \ Test whether the suite is supported by the server.
683 \ We do not support this cipher suite. Note
684 \ that this also covers the case of pseudo
688 \ If we use server order, then we place the
689 \ suite at the computed offset; otherwise, we
690 \ append it to the list at the current place.
692 2 << addr-client_suites + suite swap set16
695 \ We need to test for list length because
696 \ the client list may have duplicates,
697 \ that we do not filter. Duplicates are
698 \ invalid so this is not a problem if we
699 \ reject such clients.
700 css-off css-max >= if
701 ERR_BAD_HANDSHAKE fail
710 \ Compression methods. We need method 0 (no compression).
714 read8 ifnot -1 >ok-compression then
718 \ Set default values for parameters that may be affected by
720 \ -- server name is empty
721 \ -- client is reputed to know RSA and ECDSA, both with SHA-1
722 \ -- the default elliptic curve is P-256 (secp256r1, id = 23)
723 0 addr-server_name set8
724 0x0404 addr-hashes set32
725 0x800000 addr-curves set32
727 \ Process extensions, if any.
732 \ Server Name Indication.
740 \ Secure Renegotiation.
744 \ Signature Algorithms.
750 read-supported-curves
752 \ Supported Point Formats.
753 \ We only support "uncompressed", that all
754 \ implementations are supposed to support,
755 \ so we can simply ignore that extension.
762 read-ALPN-from-client
765 \ Other extensions are ignored.
766 drop read-ignore-16 0
775 \ Cancel session resumption if the cipher suite was not found.
776 resume resume-suite and >resume
778 \ Now check the received data. Since the client is expecting an
779 \ answer, we can send an appropriate fatal alert on any error.
781 \ Compute protocol version as the minimum of our maximum version,
782 \ and the maximum version sent by the client. If that is less than
783 \ 0x0300 (SSL-3.0), then fail. Otherwise, we may at least send an
784 \ alert with that version. We still reject versions lower than our
785 \ configured minimum.
786 \ As a special case, in case of undue downgrade, we send a specific
787 \ alert (see RFC 7507). Note that this case may happen only if
788 \ we would otherwise accept the client's version.
789 client-version-max 0< if
790 addr-client_max_version get16 addr-version_out set16
793 addr-version_max get16
794 dup client-version-max > if drop client-version-max then
795 dup 0x0300 < if ERR_BAD_VERSION fail then
796 client-version-max addr-version_min get16 < if
799 \ If resuming the session, then enforce the previously negotiated
800 \ version (if still possible).
802 addr-version get16 client-version-max <= if
803 drop addr-version get16
808 dup addr-version set16
809 dup addr-version_in set16
810 dup addr-version_out set16
811 0x0303 >= { can-tls12 }
813 \ If the client sent TLS_EMPTY_RENEGOTIATION_INFO_SCSV, then
814 \ we should mark the client as "supporting secure renegotiation".
815 reneg-scsv if 2 addr-reneg set8 then
818 ok-compression ifnot 40 fail-alert then
820 \ Filter hash function support by what the server also supports.
821 \ If no common hash function remains with RSA and/or ECDSA, then
822 \ the corresponding ECDHE suites are not possible.
823 supported-hash-functions drop 257 * 0xFFFF0000 or
824 addr-hashes get32 and dup addr-hashes set32
825 \ In 'can-ecdhe', bit 12 is set if ECDHE_RSA is possible, bit 13 is
826 \ set if ECDHE_ECDSA is possible.
828 swap 8 >> 0<> 2 and or 12 << { can-ecdhe }
830 \ Filter supported curves. If there is no common curve between
831 \ client and us, then ECDHE suites cannot be used. Note that we
832 \ may still allow ECDH, depending on the EC key handler.
833 addr-curves get32 supported-curves and dup addr-curves set32
834 ifnot 0 >can-ecdhe then
836 \ If resuming a session, then the next steps are not necessary;
837 \ we won't invoke the policy handler.
838 resume if -1 ret then
840 \ We are not resuming, so a new session ID should be generated.
841 \ We don't check that the new ID is distinct from the one sent
842 \ by the client because probability of such an event is 2^(-256),
843 \ i.e. much (much) lower than that of an undetected transmission
844 \ error or hardware miscomputation, and with similar consequences
845 \ (handshake simply fails).
846 addr-session_id 32 mkrand
847 32 addr-session_id_len set8
849 \ Translate common cipher suites, then squeeze out holes: there
850 \ may be holes because of the way we fill the list when the
851 \ server preference order is enforced, and also in case some
852 \ suites are filtered out. In particular:
853 \ -- ECDHE suites are removed if there is no common hash function
854 \ (for the relevant signature algorithm) or no common curve.
855 \ -- TLS-1.2-only suites are removed if the negociated version is
857 addr-client_suites dup >css-off
858 begin dup css-max < while
859 dup get16 dup cipher-suite-to-elements
860 dup 12 >> dup 1 = swap 2 = or if
861 dup can-ecdhe and ifnot
866 \ Suites compatible with TLS-1.0 and TLS-1.1 are
867 \ exactly the ones that use HMAC/SHA-1.
868 dup 0xF0 and 0x20 <> if
873 css-off 2+ set16 css-off set16
881 css-off addr-client_suites - 2 >>
883 \ No common cipher suite: handshake failure.
886 addr-client_suites_num set8
889 addr-selected_protocol get16 0xFFFF = if
890 3 flag? if 120 fail-alert then
891 0 addr-selected_protocol set16
894 \ Call policy handler to obtain the cipher suite and other
896 call-policy-handler ifnot 40 fail-alert then
898 \ We are not resuming a session.
902 : write-ServerHello ( initial -- )
904 \ Compute ServerHello length.
907 \ Compute length of Secure Renegotiation extension.
908 addr-reneg get8 2 = if
909 initial if 5 else 29 then
915 \ Compute length of Max Fragment Length extension.
916 addr-peer_log_max_frag_len get8 if 5 else 0 then
919 \ Compute length of ALPN extension. This also copy the
920 \ selected protocol name into the pad.
921 addr-selected_protocol get16 dup if 1- copy-protocol-name 7 + then
924 \ Adjust ServerHello length to account for the extensions.
925 ext-reneg-len ext-max-frag-len + ext-ALPN-len + dup if 2 + then +
929 addr-version get16 write16
932 addr-server_random 4 bzero
933 addr-server_random 4 + 28 mkrand
934 addr-server_random 32 write-blob
937 \ TODO: if we have no session cache at all, we might send here
938 \ an empty session ID. This would save a bit of network
941 addr-session_id 32 write-blob
944 addr-cipher_suite get16 write16
950 ext-reneg-len ext-max-frag-len + ext-ALPN-len + dup if
955 1- addr-saved_finished swap write-blob-head8
961 1 write16 addr-peer_log_max_frag_len get8 8 - write8
964 \ Note: the selected protocol name was previously
965 \ copied into the pad.
969 1- addr-pad swap write-blob-head8
977 \ Do the first part of ECDHE. Returned value is the computed signature
978 \ length, or a negative error code on error.
979 cc: do-ecdhe-part1 ( curve -- len ) {
980 int curve = T0_POPi();
981 T0_PUSHi(do_ecdhe_part1(CTX, curve));
984 \ Get index of first bit set to 1 (in low to high order).
985 : lowest-1 ( bits -- n )
986 dup ifnot drop -1 ret then
987 0 begin dup2 >> 1 and 0= while 1+ repeat
990 \ Write the Server Key Exchange message (if applicable).
991 : write-ServerKeyExchange ( -- )
992 addr-cipher_suite get16 use-ecdhe? ifnot ret then
994 \ We must select an appropriate curve among the curves that
995 \ are supported both by us and the peer. Right now, we apply
996 \ a fixed preference order: Curve25519, P-256, P-384, P-521,
997 \ then the common curve with the lowest ID.
998 \ (TODO: add some option to make that behaviour configurable.)
1000 \ This loop always terminates because previous processing made
1001 \ sure that ECDHE suites are not selectable if there is no common
1004 dup 0x20000000 and if
1007 dup 0x38000000 and dup if swap then
1012 \ Compute the signed curve point to send.
1013 curve-id do-ecdhe-part1 dup 0< if neg fail then { sig-len }
1015 \ If using TLS-1.2+, then the hash function and signature
1016 \ algorithm are explicitly encoded in the message.
1017 addr-version get16 0x0303 >= { tls1.2+ }
1020 sig-len addr-ecdhe_point_len get8 + tls1.2+ 2 and + 6 + write24
1022 \ Curve parameters: named curve with 16-bit ID.
1023 3 write8 curve-id write16
1026 addr-ecdhe_point addr-ecdhe_point_len get8 write-blob-head8
1028 \ If TLS-1.2+, write hash and signature identifiers.
1030 \ sign_hash_id contains either a hash identifier,
1031 \ or the complete 16-bit value to write.
1032 addr-sign_hash_id get16
1037 \ 'use-rsa-ecdhe?' returns -1 for RSA, 0 for
1038 \ ECDSA. The byte on the wire shall be 1 for RSA,
1040 addr-cipher_suite get16 use-rsa-ecdhe? 1 << 3 + write8
1046 addr-pad sig-len write-blob ;
1048 \ Get length of the list of anchor names to send to the client. The length
1049 \ includes the per-name 2-byte header, but _not_ the 2-byte header for
1050 \ the list itself. If no client certificate is requested, then this
1052 cc: ta-names-total-length ( -- len ) {
1056 if (CTX->ta_names != NULL) {
1057 for (u = 0; u < CTX->num_tas; u ++) {
1058 len += CTX->ta_names[u].len + 2;
1060 } else if (CTX->tas != NULL) {
1061 for (u = 0; u < CTX->num_tas; u ++) {
1062 len += CTX->tas[u].dn.len + 2;
1068 \ Compute length and optionally write the contents of the list of
1069 \ supported client authentication methods.
1070 : write-list-auth ( do_write -- len )
1072 addr-cipher_suite get16 use-ecdh? if
1073 2+ over if 65 write8 66 write8 then
1075 supports-rsa-sign? if 1+ over if 1 write8 then then
1076 supports-ecdsa? if 1+ over if 64 write8 then then
1079 : write-signhash-inner2 ( dow algo hashes len id -- dow algo hashes len )
1081 over 1 id << and ifnot ret then
1083 3 pick if id write8 2 pick write8 then ;
1085 : write-signhash-inner1 ( dow algo hashes -- dow len )
1087 4 write-signhash-inner2
1088 5 write-signhash-inner2
1089 6 write-signhash-inner2
1090 3 write-signhash-inner2
1091 2 write-signhash-inner2
1094 \ Compute length and optionally write the contents of the list of
1095 \ supported sign+hash algorithms.
1096 : write-list-signhash ( do_write -- len )
1098 \ If supporting neither RSA nor ECDSA in the engine, then we
1099 \ will do only static ECDH, and thus we claim support for
1100 \ everything (for the X.509 validator).
1101 supports-rsa-sign? supports-ecdsa? or ifnot
1102 1 0x7C write-signhash-inner1 >len
1103 3 0x7C write-signhash-inner1 len +
1106 supports-rsa-sign? if
1107 1 supported-hash-functions drop
1108 write-signhash-inner1 >len
1111 3 supported-hash-functions drop
1112 write-signhash-inner1 len + >len
1116 \ Initialise index for sending the list of anchor DN.
1117 cc: begin-ta-name-list ( -- ) {
1118 CTX->cur_dn_index = 0;
1121 \ Switch to next DN in the list. Returned value is the DN length, or -1
1122 \ if the end of the list was reached.
1123 cc: begin-ta-name ( -- len ) {
1124 const br_x500_name *dn;
1125 if (CTX->cur_dn_index >= CTX->num_tas) {
1128 if (CTX->ta_names == NULL) {
1129 dn = &CTX->tas[CTX->cur_dn_index].dn;
1131 dn = &CTX->ta_names[CTX->cur_dn_index];
1133 CTX->cur_dn_index ++;
1134 CTX->cur_dn = dn->data;
1135 CTX->cur_dn_len = dn->len;
1136 T0_PUSH(CTX->cur_dn_len);
1140 \ Copy a chunk of the current DN into the pad. Returned value is the
1141 \ chunk length; this is 0 when the end of the current DN is reached.
1142 cc: copy-dn-chunk ( -- len ) {
1145 clen = CTX->cur_dn_len;
1146 if (clen > sizeof ENG->pad) {
1147 clen = sizeof ENG->pad;
1149 memcpy(ENG->pad, CTX->cur_dn, clen);
1150 CTX->cur_dn += clen;
1151 CTX->cur_dn_len -= clen;
1155 \ Write a CertificateRequest message.
1156 : write-CertificateRequest ( -- )
1157 \ The list of client authentication types includes:
1160 \ rsa_fixed_ecdh (65)
1161 \ ecdsa_fixed_ecdh (66)
1162 \ rsa_sign and ecdsa_sign require, respectively, RSA and ECDSA
1163 \ support. Static ECDH requires that the cipher suite is ECDH.
1164 \ When we ask for static ECDH, we always send both rsa_fixed_ecdh
1165 \ and ecdsa_fixed_ecdh because what matters there is what the
1166 \ X.509 engine may support, and we do not control that.
1168 \ With TLS 1.2, we must also send a list of supported signature
1169 \ and hash algorithms. That list is supposed to qualify both
1170 \ the engine itself, and the X.509 validator, which are separate
1171 \ in BearSSL. There again, we use the engine capabilities in that
1172 \ list, and resort to a generic all-support list if only
1173 \ static ECDH is accepted.
1175 \ (In practice, client implementations tend to have at most one
1176 \ or two certificates, and send the chain regardless of what
1177 \ algorithms are used in it.)
1180 addr-version get16 0x0303 >= if
1181 2+ 0 write-list-signhash +
1183 ta-names-total-length + 3 +
1188 \ List of authentication methods
1189 0 write-list-auth write8 1 write-list-auth drop
1191 \ For TLS 1.2+, list of sign+hash
1192 addr-version get16 0x0303 >= if
1193 0 write-list-signhash write16 1 write-list-signhash drop
1196 \ Trust anchor names
1197 ta-names-total-length write16
1201 dup 0< if drop ret then write16
1202 begin copy-dn-chunk dup while
1203 addr-pad swap write-blob
1208 \ Write the Server Hello Done message.
1209 : write-ServerHelloDone ( -- )
1210 14 write8 0 write24 ;
1212 \ Perform RSA decryption of the client-sent pre-master secret. The value
1213 \ is in the pad, and its length is provided as parameter.
1214 cc: do-rsa-decrypt ( len prf_id -- ) {
1215 int prf_id = T0_POPi();
1216 size_t len = T0_POP();
1217 do_rsa_decrypt(CTX, prf_id, ENG->pad, len);
1220 \ Perform ECDH (not ECDHE). The point from the client is in the pad, and
1221 \ its length is provided as parameter.
1222 cc: do-ecdh ( len prf_id -- ) {
1223 int prf_id = T0_POPi();
1224 size_t len = T0_POP();
1225 do_ecdh(CTX, prf_id, ENG->pad, len);
1228 \ Do the second part of ECDHE.
1229 cc: do-ecdhe-part2 ( len prf_id -- ) {
1230 int prf_id = T0_POPi();
1231 size_t len = T0_POP();
1232 do_ecdhe_part2(CTX, prf_id, ENG->pad, len);
1235 \ Perform static ECDH. The point from the client is the public key
1236 \ extracted from its certificate.
1237 cc: do-static-ecdh ( prf_id -- ) {
1238 do_static_ecdh(CTX, T0_POP());
1241 \ Read a ClientKeyExchange header.
1242 : read-ClientKeyExchange-header ( -- len )
1243 read-handshake-header 16 = ifnot ERR_UNEXPECTED fail then ;
1245 \ Read the Client Key Exchange contents (non-empty case).
1246 : read-ClientKeyExchange-contents ( lim -- )
1247 \ What we should get depends on the cipher suite.
1248 addr-cipher_suite get16 use-rsa-keyx? if
1249 \ RSA key exchange: we expect a RSA-encrypted value.
1251 dup 512 > if ERR_LIMIT_EXCEEDED fail then
1253 addr-pad swap read-blob
1254 enc-rsa-len addr-cipher_suite get16 prf-id do-rsa-decrypt
1256 addr-cipher_suite get16 dup use-ecdhe? swap use-ecdh? { ecdhe ecdh }
1258 \ ECDH or ECDHE key exchange: we expect an EC point.
1259 read8 dup { ec-point-len }
1260 addr-pad swap read-blob
1261 ec-point-len addr-cipher_suite get16 prf-id
1262 ecdhe if do-ecdhe-part2 else do-ecdh then
1266 \ Read the Client Key Exchange (normal case).
1267 : read-ClientKeyExchange ( -- )
1268 read-ClientKeyExchange-header
1269 read-ClientKeyExchange-contents ;
1271 \ Obtain all possible hash values for handshake messages so far. This
1272 \ is done because we need the hash value for the CertificateVerify
1273 \ _before_ knowing which hash function will actually be used, as this
1274 \ information is obtained from decoding the message header itself.
1275 \ All hash values are stored in the pad (208 bytes in total).
1276 cc: compute-hash-CV ( -- ) {
1279 for (i = 1; i <= 6; i ++) {
1280 br_multihash_out(&ENG->mhash, i,
1281 ENG->pad + HASH_PAD_OFF[i - 1]);
1285 \ Copy the proper hash value from the pad into the dedicated buffer.
1286 \ Returned value is true (-1) on success, false (0) on error (error
1287 \ being an unimplemented hash function). The id has already been verified
1288 \ to be either 0 (for MD5+SHA-1) or one of the SHA-* functions.
1289 cc: copy-hash-CV ( hash_id -- bool ) {
1297 if (br_multihash_getimpl(&ENG->mhash, id) == 0) {
1301 off = HASH_PAD_OFF[id - 1];
1302 len = HASH_PAD_OFF[id] - off;
1304 memcpy(CTX->hash_CV, ENG->pad + off, len);
1305 CTX->hash_CV_len = len;
1306 CTX->hash_CV_id = id;
1310 \ Verify signature in CertificateVerify. Output is 0 on success, or a
1311 \ non-zero error code.
1312 cc: verify-CV-sig ( sig-len -- err ) {
1315 err = verify_CV_sig(CTX, T0_POP());
1319 \ Process static ECDH.
1320 : process-static-ECDH ( ktu -- )
1321 \ Static ECDH is allowed only if the cipher suite uses ECDH, and
1322 \ the client's public key has type EC and allows key exchange.
1323 \ BR_KEYTYPE_KEYX is 0x10, and BR_KEYTYPE_EC is 2.
1324 0x1F and 0x12 = ifnot ERR_WRONG_KEY_USAGE fail then
1325 addr-cipher_suite get16
1326 dup use-ecdh? ifnot ERR_UNEXPECTED fail then
1330 \ Read CertificateVerify header.
1331 : read-CertificateVerify-header ( -- lim )
1333 read-handshake-header 15 = ifnot ERR_UNEXPECTED fail then ;
1335 \ Read CertificateVerify. The client key type + usage is expected on the
1337 : read-CertificateVerify ( ktu -- )
1338 \ Check that the key allows for signatures.
1339 dup 0x20 and ifnot ERR_WRONG_KEY_USAGE fail then
1340 0x0F and { key-type }
1343 read-CertificateVerify-header
1345 \ With TLS 1.2+, there is an explicit hash + signature indication,
1346 \ which must be compatible with the key type.
1347 addr-version get16 0x0303 >= if
1348 \ Get hash function, then signature algorithm. The
1349 \ signature algorithm is 1 (RSA) or 3 (ECDSA) while our
1350 \ symbolic constants for key types are 1 (RSA) or 2 (EC).
1352 dup 0xFF and 1+ 1 >> key-type = ifnot
1353 ERR_BAD_SIGNATURE fail
1357 \ We support only SHA-1, SHA-224, SHA-256, SHA-384
1358 \ and SHA-512. We explicitly reject MD5.
1359 dup 2 < over 6 > or if ERR_INVALID_ALGORITHM fail then
1361 \ With TLS 1.0 and 1.1, hash is MD5+SHA-1 (0) for RSA,
1362 \ SHA-1 (2) for ECDSA.
1363 key-type 0x01 = if 0 else 2 then
1365 copy-hash-CV ifnot ERR_INVALID_ALGORITHM fail then
1368 read16 dup { sig-len }
1369 dup 512 > if ERR_LIMIT_EXCEEDED fail then
1370 addr-pad swap read-blob
1371 sig-len verify-CV-sig
1372 dup if fail then drop
1376 \ Send a HelloRequest.
1377 : send-HelloRequest ( -- )
1379 begin can-output? not while wait-co drop repeat
1380 22 addr-record_type_out set8
1381 0 write8 0 write24 flush-record
1382 23 addr-record_type_out set8 ;
1385 : do-handshake ( initial -- )
1386 0 addr-application_data set8
1387 22 addr-record_type_out set8
1388 0 addr-selected_protocol set16
1391 more-incoming-bytes? if ERR_UNEXPECTED fail then
1393 \ Session resumption
1395 0 write-CCS-Finished
1398 \ Not a session resumption
1400 write-Certificate drop
1401 write-ServerKeyExchange
1402 ta-names-total-length if
1403 write-CertificateRequest
1405 write-ServerHelloDone
1408 \ If we sent a CertificateRequest then we expect a
1409 \ Certificate message.
1410 ta-names-total-length if
1411 \ Read client certificate.
1416 \ Client certificate validation failed.
1417 2 flag? ifnot neg fail then
1419 read-ClientKeyExchange
1420 read-CertificateVerify-header
1424 \ Client sent no certificate at all.
1427 ERR_NO_CLIENT_AUTH fail
1429 read-ClientKeyExchange
1432 \ Client certificate was validated.
1433 read-ClientKeyExchange-header
1435 \ Empty ClientKeyExchange.
1439 read-ClientKeyExchange-contents
1440 read-CertificateVerify
1444 \ No client certificate request, we just expect
1445 \ a non-empty ClientKeyExchange.
1446 read-ClientKeyExchange
1449 0 write-CCS-Finished
1452 1 addr-application_data set8
1453 23 addr-record_type_out set8 ;
1457 \ Perform initial handshake.
1461 \ Wait for further invocation. At that point, we should
1462 \ get either an explicit call for renegotiation, or
1463 \ an incoming ClientHello handshake message.
1468 \ The best we can do is ask for a
1469 \ renegotiation, then wait for it
1475 \ Reject renegotiations if the peer does not
1476 \ support secure renegotiation, or if the
1477 \ "no renegotiation" flag is set.
1479 addr-reneg get8 1 = 1 flag? or if
1481 begin can-output? not while