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 *cpoint, size_t cpoint_len, uint32_t ctl)
90 unsigned char rpms[80];
94 * The point length is supposed to be 1+2*Xlen, where Xlen is
95 * the length (in bytes) of the X coordinate, i.e. the pre-master
96 * secret. If the provided point is too large, then it is
97 * obviously incorrect (i.e. everybody can see that it is
98 * incorrect), so leaking that fact is not a problem.
100 pms_len = cpoint_len >> 1;
101 if (pms_len > sizeof rpms) {
102 pms_len = sizeof rpms;
107 * Make a random PMS and copy it above the decrypted value if the
108 * decryption failed. Note that we use a constant-time conditional
111 br_hmac_drbg_generate(&ctx->eng.rng, rpms, pms_len);
112 br_ccopy(ctl ^ 1, cpoint + 1, rpms, pms_len);
115 * Compute master secret.
117 br_ssl_engine_compute_master(&ctx->eng, prf_id, cpoint + 1, pms_len);
120 * Clear the pre-master secret from RAM: it is normally a buffer
121 * in the context, hence potentially long-lived.
123 memset(cpoint, 0, cpoint_len);
127 * Do the ECDH key exchange (not ECDHE).
130 do_ecdh(br_ssl_server_context *ctx, int prf_id,
131 unsigned char *cpoint, size_t cpoint_len)
136 * Finalise the key exchange.
138 x = (*ctx->policy_vtable)->do_keyx(ctx->policy_vtable,
140 ecdh_common(ctx, prf_id, cpoint, cpoint_len, x);
144 * Do the full static ECDH key exchange. When this function is called,
145 * it has already been verified that the cipher suite uses ECDH (not ECDHE),
146 * and the client's public key (from its certificate) has type EC and is
147 * apt for key exchange.
150 do_static_ecdh(br_ssl_server_context *ctx, int prf_id)
152 unsigned char cpoint[133];
154 const br_x509_class **xc;
155 const br_x509_pkey *pk;
157 xc = ctx->eng.x509ctx;
158 pk = (*xc)->get_pkey(xc, NULL);
159 cpoint_len = pk->key.ec.qlen;
160 if (cpoint_len > sizeof cpoint) {
162 * If the point is larger than our buffer then we need to
163 * restrict it. Length 2 is not a valid point length, so
164 * the ECDH will fail.
168 memcpy(cpoint, pk->key.ec.q, cpoint_len);
169 do_ecdh(ctx, prf_id, cpoint, cpoint_len);
173 * Do the ECDHE key exchange (part 1: generation of transient key, and
174 * computing of the point to send to the client). Returned value is the
175 * signature length (in bytes), or -x on error (with x being an error
176 * code). The encoded point is written in the ecdhe_point[] context buffer
177 * (length in ecdhe_point_len).
180 do_ecdhe_part1(br_ssl_server_context *ctx, int curve)
184 const unsigned char *order;
186 br_multihash_context mhc;
187 unsigned char head[4];
188 size_t hv_len, sig_len;
190 if (!((ctx->eng.iec->supported_curves >> curve) & 1)) {
191 return -BR_ERR_INVALID_ALGORITHM;
193 ctx->eng.ecdhe_curve = curve;
196 * Generate our private key. We need a non-zero random value
197 * which is lower than the curve order, in a "large enough"
198 * range. We force the top bit to 0 and bottom bit to 1, which
199 * does the trick. Note that contrary to what happens in ECDSA,
200 * this is not a problem if we do not cover the full range of
203 order = ctx->eng.iec->order(curve, &olen);
205 while (mask >= order[0]) {
208 br_hmac_drbg_generate(&ctx->eng.rng, ctx->ecdhe_key, olen);
209 ctx->ecdhe_key[0] &= mask;
210 ctx->ecdhe_key[olen - 1] |= 0x01;
211 ctx->ecdhe_key_len = olen;
214 * Compute our ECDH point.
218 generator = ctx->eng.iec->generator(curve, &glen);
219 memcpy(ctx->eng.ecdhe_point, generator, glen);
220 ctx->eng.ecdhe_point_len = glen;
221 if (!ctx->eng.iec->mul(ctx->eng.ecdhe_point, glen,
222 ctx->ecdhe_key, olen, curve))
224 return -BR_ERR_INVALID_ALGORITHM;
227 glen = ctx->eng.iec->mulgen(ctx->eng.ecdhe_point,
228 ctx->ecdhe_key, olen, curve);
229 ctx->eng.ecdhe_point_len = glen;
232 * Compute the signature.
234 br_multihash_zero(&mhc);
235 br_multihash_copyimpl(&mhc, &ctx->eng.mhash);
236 br_multihash_init(&mhc);
237 br_multihash_update(&mhc,
238 ctx->eng.client_random, sizeof ctx->eng.client_random);
239 br_multihash_update(&mhc,
240 ctx->eng.server_random, sizeof ctx->eng.server_random);
244 head[3] = ctx->eng.ecdhe_point_len;
245 br_multihash_update(&mhc, head, sizeof head);
246 br_multihash_update(&mhc,
247 ctx->eng.ecdhe_point, ctx->eng.ecdhe_point_len);
248 hash = ctx->sign_hash_id;
250 hv_len = br_multihash_out(&mhc, hash, ctx->eng.pad);
252 return -BR_ERR_INVALID_ALGORITHM;
255 if (!br_multihash_out(&mhc, br_md5_ID, ctx->eng.pad)
256 || !br_multihash_out(&mhc,
257 br_sha1_ID, ctx->eng.pad + 16))
259 return -BR_ERR_INVALID_ALGORITHM;
263 sig_len = (*ctx->policy_vtable)->do_sign(ctx->policy_vtable,
264 hash, hv_len, ctx->eng.pad, sizeof ctx->eng.pad);
265 return sig_len ? (int)sig_len : -BR_ERR_INVALID_ALGORITHM;
269 * Do the ECDHE key exchange (part 2: computation of the shared secret
270 * from the point sent by the client).
273 do_ecdhe_part2(br_ssl_server_context *ctx, int prf_id,
274 unsigned char *cpoint, size_t cpoint_len)
279 curve = ctx->eng.ecdhe_curve;
282 * Finalise the key exchange.
284 x = ctx->eng.iec->mul(cpoint, cpoint_len,
285 ctx->ecdhe_key, ctx->ecdhe_key_len, curve);
286 ecdh_common(ctx, prf_id, cpoint, cpoint_len, x);
289 * Clear the ECDHE private key. Forward Secrecy is achieved insofar
290 * as that key does not get stolen, so we'd better destroy it
291 * as soon as it ceases to be useful.
293 memset(ctx->ecdhe_key, 0, ctx->ecdhe_key_len);
297 * Offset for hash value within the pad (when obtaining all hash values,
298 * in preparation for verification of the CertificateVerify message).
299 * Order is MD5, SHA-1, SHA-224, SHA-256, SHA-384, SHA-512; last value
300 * is used to get the total length.
302 static const unsigned char HASH_PAD_OFF[] = { 0, 16, 36, 64, 96, 144, 208 };
305 * OID for hash functions in RSA signatures.
307 static const unsigned char HASH_OID_SHA1[] = {
308 0x05, 0x2B, 0x0E, 0x03, 0x02, 0x1A
311 static const unsigned char HASH_OID_SHA224[] = {
312 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x04
315 static const unsigned char HASH_OID_SHA256[] = {
316 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01
319 static const unsigned char HASH_OID_SHA384[] = {
320 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x02
323 static const unsigned char HASH_OID_SHA512[] = {
324 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03
327 static const unsigned char *HASH_OID[] = {
336 * Verify the signature in CertificateVerify. Returned value is 0 on
337 * success, or a non-zero error code. Lack of implementation of the
338 * designated signature algorithm is reported as a "bad signature"
339 * error (because it means that the peer did not honour our advertised
340 * set of supported signature algorithms).
343 verify_CV_sig(br_ssl_server_context *ctx, size_t sig_len)
345 const br_x509_class **xc;
346 const br_x509_pkey *pk;
349 id = ctx->hash_CV_id;
350 xc = ctx->eng.x509ctx;
351 pk = (*xc)->get_pkey(xc, NULL);
352 if (pk->key_type == BR_KEYTYPE_RSA) {
353 unsigned char tmp[64];
354 const unsigned char *hash_oid;
359 hash_oid = HASH_OID[id - 2];
361 if (ctx->eng.irsavrfy == 0) {
362 return BR_ERR_BAD_SIGNATURE;
364 if (!ctx->eng.irsavrfy(ctx->eng.pad, sig_len,
365 hash_oid, ctx->hash_CV_len, &pk->key.rsa, tmp)
366 || memcmp(tmp, ctx->hash_CV, ctx->hash_CV_len) != 0)
368 return BR_ERR_BAD_SIGNATURE;
371 if (ctx->eng.iecdsa == 0) {
372 return BR_ERR_BAD_SIGNATURE;
374 if (!ctx->eng.iecdsa(ctx->eng.iec,
375 ctx->hash_CV, ctx->hash_CV_len,
376 &pk->key.ec, ctx->eng.pad, sig_len))
378 return BR_ERR_BAD_SIGNATURE;
386 \ =======================================================================
390 "addr-" field + 0 1 define-word
391 0 8191 "offsetof(br_ssl_server_context, " field + ")" + make-CX
392 postpone literal postpone ; ;
394 addr-ctx: client_max_version
395 addr-ctx: client_suites
396 addr-ctx: client_suites_num
399 addr-ctx: sign_hash_id
401 \ Get address and length of the client_suites[] buffer. Length is expressed
403 : addr-len-client_suites ( -- addr len )
405 CX 0 1023 { BR_MAX_CIPHER_SUITES * sizeof(br_suite_translated) } ;
407 \ Read the client SNI extension.
408 : read-client-sni ( lim -- lim )
409 \ Open extension value.
412 \ Open ServerNameList.
415 \ Find if there is a name of type 0 (host_name) with a length
416 \ that fits in our dedicated buffer.
423 dup addr-server_name + 0 swap set8
424 addr-server_name swap read-blob
431 \ Close ServerNameList.
434 \ Close extension value.
437 \ Set the new maximum fragment length. BEWARE: this shall be called only
438 \ after reading the ClientHello and before writing the ServerHello.
439 cc: set-max-frag-len ( len -- ) {
440 size_t max_frag_len = T0_POP();
442 br_ssl_engine_new_max_frag_len(ENG, max_frag_len);
445 * We must adjust our own output limit. Since we call this only
446 * after receiving a ClientHello and before beginning to send
447 * the ServerHello, the next output record should be empty at
448 * that point, so we can use max_frag_len as a limit.
450 if (ENG->hlen_out > max_frag_len) {
451 ENG->hlen_out = max_frag_len;
455 \ Read the client Max Frag Length extension.
456 : read-client-frag ( lim -- lim )
457 \ Extension value must have length exactly 1 byte.
458 read16 1 <> if ERR_BAD_FRAGLEN fail then
461 \ The byte value must be 1, 2, 3 or 4.
462 dup dup 0= swap 5 >= or if ERR_BAD_FRAGLEN fail then
464 \ If our own maximum fragment length is greater, then we reduce
466 8 + dup addr-log_max_frag_len get8 < if
467 dup 1 swap << set-max-frag-len
468 dup addr-log_max_frag_len set8
469 addr-peer_log_max_frag_len set8
474 \ Read the Secure Renegotiation extension from the client.
475 : read-client-reneg ( lim -- lim )
479 \ The "reneg" value is one of:
480 \ 0 on first handshake, client support is unknown
481 \ 1 client does not support secure renegotiation
482 \ 2 client supports secure renegotiation
485 \ First handshake, value length shall be 1.
486 1 = ifnot ERR_BAD_SECRENEG fail then
487 read8 if ERR_BAD_SECRENEG fail then
491 \ Renegotiation, value shall consist of 13 bytes
492 \ (header + copy of the saved client "Finished").
493 13 = ifnot ERR_BAD_SECRENEG fail then
494 read8 12 = ifnot ERR_BAD_SECRENEG fail then
495 addr-pad 12 read-blob
496 addr-saved_finished addr-pad 12 memcmp ifnot
497 ERR_BAD_SECRENEG fail
501 \ If "reneg" is 1 then the client is not supposed to support
502 \ the extension, and it sends it nonetheless, which means
504 ERR_BAD_SECRENEG fail
507 \ Read the Signature Algorithms extension.
508 : read-signatures ( lim -- lim )
509 \ Open extension value.
512 read-list-sign-algos addr-hashes set16
514 \ Close extension value.
517 \ Read the Supported Curves extension.
518 : read-supported-curves ( lim -- lim )
519 \ Open extension value.
522 \ Open list of curve identifiers.
525 \ Get all supported curves.
529 1 swap << addr-curves get32 or addr-curves set32
537 \ Read the ALPN extension from client.
538 : read-ALPN-from-client ( lim -- lim )
539 \ If we do not have configured names, then we just ignore the
541 addr-protocol_names_num get16 ifnot read-ignore-16 ret then
543 \ Open extension value.
546 \ Open list of protocol names.
549 \ Get all names and test for their support. We keep the one with
550 \ the lowest index (because we apply server's preferences, as
551 \ recommended by RFC 7301, section 3.2. We set the 'found' variable
552 \ to -2 and use an unsigned comparison, making -2 a huge value.
555 read8 dup { len } addr-pad swap read-blob
556 len test-protocol-name dup found u< if
567 \ Write back found name index (or not). If no match was found,
568 \ then we write -1 (0xFFFF) in the index value, not 0, so that
569 \ the caller knows that we tried to match, and failed.
570 found 1+ addr-selected_protocol set16 ;
572 \ Call policy handler to get cipher suite, hash function identifier and
573 \ certificate chain. Returned value is 0 (false) on failure.
574 cc: call-policy-handler ( -- bool ) {
576 br_ssl_server_choices choices;
578 x = (*CTX->policy_vtable)->choose(
579 CTX->policy_vtable, CTX, &choices);
580 ENG->session.cipher_suite = choices.cipher_suite;
581 CTX->sign_hash_id = choices.hash_id;
582 ENG->chain = choices.chain;
583 ENG->chain_len = choices.chain_len;
587 \ Check for a remembered session.
588 cc: check-resume ( -- bool ) {
589 if (ENG->session.session_id_len == 32
590 && CTX->cache_vtable != NULL && (*CTX->cache_vtable)->load(
591 CTX->cache_vtable, CTX, &ENG->session))
599 \ Save the current session.
600 cc: save-session ( -- ) {
601 if (CTX->cache_vtable != NULL) {
602 (*CTX->cache_vtable)->save(
603 CTX->cache_vtable, CTX, &ENG->session);
607 \ Read ClientHello. If the session is resumed, then -1 is returned.
608 : read-ClientHello ( -- resume )
609 \ Get header, and check message type.
610 read-handshake-header 1 = ifnot ERR_UNEXPECTED fail then
612 \ Get maximum protocol version from client.
613 read16 dup { client-version-max } addr-client_max_version set16
616 addr-client_random 32 read-blob
619 read8 dup 32 > if ERR_OVERSIZED_ID fail then
620 dup addr-session_id_len set8
621 addr-session_id swap read-blob
623 \ Lookup session for resumption. We should do that here because
624 \ we need to verify that the remembered cipher suite is still
625 \ matched by this ClientHello.
626 check-resume { resume }
628 \ Cipher suites. We read all cipher suites from client, each time
629 \ matching against our own list. We accumulate suites in the
630 \ client_suites[] context buffer: we keep suites that are
631 \ supported by both the client and the server (so the list size
632 \ cannot exceed that of the server list), and we keep them in
633 \ either client or server preference order (depending on the
636 \ We also need to identify the pseudo cipher suite for secure
637 \ renegotiation here.
641 addr-len-client_suites dup2 bzero
642 over + { css-off css-max }
647 \ Check that when resuming a session, the requested
648 \ suite is still valid.
650 dup addr-cipher_suite get16 = if
655 \ Special handling for TLS_EMPTY_RENEGOTIATION_INFO_SCSV.
656 \ This fake cipher suite may occur only in the first
659 addr-reneg get8 if ERR_BAD_SECRENEG fail then
663 \ Special handling for TLS_FALLBACK_SCSV. If the client
664 \ maximum version is less than our own maximum version,
665 \ then this is an undue downgrade. We mark it by setting
666 \ the client max version to 0x10000.
668 client-version-max addr-version_min get16 >=
669 client-version-max addr-version_max get16 < and if
670 -1 >client-version-max
674 \ Test whether the suite is supported by the server.
676 \ We do not support this cipher suite. Note
677 \ that this also covers the case of pseudo
681 \ If we use server order, then we place the
682 \ suite at the computed offset; otherwise, we
683 \ append it to the list at the current place.
685 2 << addr-client_suites + suite swap set16
688 \ We need to test for list length because
689 \ the client list may have duplicates,
690 \ that we do not filter. Duplicates are
691 \ invalid so this is not a problem if we
692 \ reject such clients.
693 css-off css-max >= if
694 ERR_BAD_HANDSHAKE fail
703 \ Compression methods. We need method 0 (no compression).
707 read8 ifnot -1 >ok-compression then
711 \ Set default values for parameters that may be affected by
713 \ -- server name is empty
714 \ -- client is reputed to know RSA and ECDSA, both with SHA-1
715 \ -- the default elliptic curve is P-256 (secp256r1, id = 23)
716 0 addr-server_name set8
717 0x404 addr-hashes set16
718 0x800000 addr-curves set32
720 \ Process extensions, if any.
725 \ Server Name Indication.
733 \ Secure Renegotiation.
737 \ Signature Algorithms.
743 read-supported-curves
745 \ Supported Point Formats.
746 \ We only support "uncompressed", that all
747 \ implementations are supposed to support,
748 \ so we can simply ignore that extension.
755 read-ALPN-from-client
758 \ Other extensions are ignored.
759 drop read-ignore-16 0
768 \ Cancel session resumption if the cipher suite was not found.
769 resume resume-suite and >resume
771 \ Now check the received data. Since the client is expecting an
772 \ answer, we can send an appropriate fatal alert on any error.
774 \ Compute protocol version as the minimum of our maximum version,
775 \ and the maximum version sent by the client. If that is less than
776 \ 0x0300 (SSL-3.0), then fail. Otherwise, we may at least send an
777 \ alert with that version. We still reject versions lower than our
778 \ configured minimum.
779 \ As a special case, in case of undue downgrade, we send a specific
780 \ alert (see RFC 7507). Note that this case may happen only if
781 \ we would otherwise accept the client's version.
782 client-version-max 0< if
783 addr-client_max_version get16 addr-version_out set16
786 addr-version_max get16
787 dup client-version-max > if drop client-version-max then
788 dup 0x0300 < if ERR_BAD_VERSION fail then
789 client-version-max addr-version_min get16 < if
792 \ If resuming the session, then enforce the previously negotiated
793 \ version (if still possible).
795 addr-version get16 client-version-max <= if
796 drop addr-version get16
801 dup addr-version set16
802 dup addr-version_in set16
803 dup addr-version_out set16
804 0x0303 >= { can-tls12 }
806 \ If the client sent TLS_EMPTY_RENEGOTIATION_INFO_SCSV, then
807 \ we should mark the client as "supporting secure renegotiation".
808 reneg-scsv if 2 addr-reneg set8 then
811 ok-compression ifnot 40 fail-alert then
813 \ Filter hash function support by what the server also supports.
814 \ If no common hash function remains with RSA and/or ECDSA, then
815 \ the corresponding ECDHE suites are not possible.
816 supported-hash-functions drop 257 *
817 addr-hashes get16 and dup addr-hashes set16
818 \ In 'can-ecdhe', bit 12 is set if ECDHE_RSA is possible, bit 13 is
819 \ set if ECDHE_ECDSA is possible.
821 swap 8 >> 0<> 2 and or 12 << { can-ecdhe }
823 \ Filter supported curves. If there is no common curve between
824 \ client and us, then ECDHE suites cannot be used. Note that we
825 \ may still allow ECDH, depending on the EC key handler.
826 addr-curves get32 supported-curves and dup addr-curves set32
827 ifnot 0 >can-ecdhe then
829 \ If resuming a session, then the next steps are not necessary;
830 \ we won't invoke the policy handler.
831 resume if -1 ret then
833 \ We are not resuming, so a new session ID should be generated.
834 \ We don't check that the new ID is distinct from the one sent
835 \ by the client because probability of such an event is 2^(-256),
836 \ i.e. much (much) lower than that of an undetected transmission
837 \ error or hardware miscomputation, and with similar consequences
838 \ (handshake simply fails).
839 addr-session_id 32 mkrand
840 32 addr-session_id_len set8
842 \ Translate common cipher suites, then squeeze out holes: there
843 \ may be holes because of the way we fill the list when the
844 \ server preference order is enforced, and also in case some
845 \ suites are filtered out. In particular:
846 \ -- ECDHE suites are removed if there is no common hash function
847 \ (for the relevant signature algorithm) or no common curve.
848 \ -- TLS-1.2-only suites are removed if the negociated version is
850 addr-client_suites dup >css-off
851 begin dup css-max < while
852 dup get16 dup cipher-suite-to-elements
853 dup 12 >> dup 1 = swap 2 = or if
854 dup can-ecdhe and ifnot
859 \ Suites compatible with TLS-1.0 and TLS-1.1 are
860 \ exactly the ones that use HMAC/SHA-1.
861 dup 0xF0 and 0x20 <> if
866 css-off 2+ set16 css-off set16
874 css-off addr-client_suites - 2 >>
876 \ No common cipher suite: handshake failure.
879 addr-client_suites_num set8
882 addr-selected_protocol get16 0xFFFF = if
883 3 flag? if 120 fail-alert then
884 0 addr-selected_protocol set16
887 \ Call policy handler to obtain the cipher suite and other
889 call-policy-handler ifnot 40 fail-alert then
891 \ We are not resuming a session.
895 : write-ServerHello ( initial -- )
897 \ Compute ServerHello length.
900 \ Compute length of Secure Renegotiation extension.
901 addr-reneg get8 2 = if
902 initial if 5 else 29 then
908 \ Compute length of Max Fragment Length extension.
909 addr-peer_log_max_frag_len get8 if 5 else 0 then
912 \ Compute length of ALPN extension. This also copy the
913 \ selected protocol name into the pad.
914 addr-selected_protocol get16 dup if 1- copy-protocol-name 7 + then
917 \ Adjust ServerHello length to account for the extensions.
918 ext-reneg-len ext-max-frag-len + ext-ALPN-len + dup if 2 + then +
922 addr-version get16 write16
925 addr-server_random 4 bzero
926 addr-server_random 4 + 28 mkrand
927 addr-server_random 32 write-blob
930 \ TODO: if we have no session cache at all, we might send here
931 \ an empty session ID. This would save a bit of network
934 addr-session_id 32 write-blob
937 addr-cipher_suite get16 write16
943 ext-reneg-len ext-max-frag-len + ext-ALPN-len + dup if
948 1- addr-saved_finished swap write-blob-head8
954 1 write16 addr-peer_log_max_frag_len get8 8 - write8
957 \ Note: the selected protocol name was previously
958 \ copied into the pad.
962 1- addr-pad swap write-blob-head8
970 \ Do the first part of ECDHE. Returned value is the computed signature
971 \ length, or a negative error code on error.
972 cc: do-ecdhe-part1 ( curve -- len ) {
973 int curve = T0_POPi();
974 T0_PUSHi(do_ecdhe_part1(CTX, curve));
977 \ Write the Server Key Exchange message (if applicable).
978 : write-ServerKeyExchange ( -- )
979 addr-cipher_suite get16 use-ecdhe? ifnot ret then
981 \ We must select an appropriate curve among the curves that
982 \ are supported both by us and the peer. Right now we use
983 \ the one with the smallest ID, which in practice means P-256.
984 \ (TODO: add some option to make that behaviour configurable.)
986 \ This loop always terminates because previous processing made
987 \ sure that ECDHE suites are not selectable if there is no common
990 begin dup2 >> 1 and 0= while 1+ repeat
993 \ Compute the signed curve point to send.
994 curve-id do-ecdhe-part1 dup 0< if neg fail then { sig-len }
996 \ If using TLS-1.2+, then the hash function and signature
997 \ algorithm are explicitly encoded in the message.
998 addr-version get16 0x0303 >= { tls1.2+ }
1001 sig-len addr-ecdhe_point_len get8 + tls1.2+ 2 and + 6 + write24
1003 \ Curve parameters: named curve with 16-bit ID.
1004 3 write8 curve-id write16
1007 addr-ecdhe_point addr-ecdhe_point_len get8 write-blob-head8
1009 \ If TLS-1.2+, write hash and signature identifiers.
1011 \ Hash identifier is in the sign_hash_id field.
1012 addr-sign_hash_id get8 write8
1013 \ 'use-rsa-ecdhe?' returns -1 for RSA, 0 for ECDSA.
1014 \ The byte on the wire shall be 1 for RSA, 3 for ECDSA.
1015 addr-cipher_suite get16 use-rsa-ecdhe? 1 << 3 + write8
1020 addr-pad sig-len write-blob ;
1022 \ Get length of the list of anchor names to send to the client. The length
1023 \ includes the per-name 2-byte header, but _not_ the 2-byte header for
1024 \ the list itself. If no client certificate is requested, then this
1026 cc: ta-names-total-length ( -- len ) {
1030 if (CTX->ta_names != NULL) {
1031 for (u = 0; u < CTX->num_tas; u ++) {
1032 len += CTX->ta_names[u].len + 2;
1034 } else if (CTX->tas != NULL) {
1035 for (u = 0; u < CTX->num_tas; u ++) {
1036 len += CTX->tas[u].dn.len + 2;
1042 \ Compute length and optionally write the contents of the list of
1043 \ supported client authentication methods.
1044 : write-list-auth ( do_write -- len )
1046 addr-cipher_suite get16 use-ecdh? if
1047 2+ over if 65 write8 66 write8 then
1049 supports-rsa-sign? if 1+ over if 1 write8 then then
1050 supports-ecdsa? if 1+ over if 64 write8 then then
1053 : write-signhash-inner2 ( dow algo hashes len id -- dow algo hashes len )
1055 over 1 id << and ifnot ret then
1057 3 pick if id write8 2 pick write8 then ;
1059 : write-signhash-inner1 ( dow algo hashes -- dow len )
1061 4 write-signhash-inner2
1062 5 write-signhash-inner2
1063 6 write-signhash-inner2
1064 3 write-signhash-inner2
1065 2 write-signhash-inner2
1068 \ Compute length and optionally write the contents of the list of
1069 \ supported sign+hash algorithms.
1070 : write-list-signhash ( do_write -- len )
1072 \ If supporting neither RSA nor ECDSA in the engine, then we
1073 \ will do only static ECDH, and thus we claim support for
1074 \ everything (for the X.509 validator).
1075 supports-rsa-sign? supports-ecdsa? or ifnot
1076 1 0x7C write-signhash-inner1 >len
1077 3 0x7C write-signhash-inner1 len +
1080 supports-rsa-sign? if
1081 1 supported-hash-functions drop
1082 write-signhash-inner1 >len
1085 3 supported-hash-functions drop
1086 write-signhash-inner1 len + >len
1090 \ Initialise index for sending the list of anchor DN.
1091 cc: begin-ta-name-list ( -- ) {
1092 CTX->cur_dn_index = 0;
1095 \ Switch to next DN in the list. Returned value is the DN length, or -1
1096 \ if the end of the list was reached.
1097 cc: begin-ta-name ( -- len ) {
1098 const br_x500_name *dn;
1099 if (CTX->cur_dn_index >= CTX->num_tas) {
1102 if (CTX->ta_names == NULL) {
1103 dn = &CTX->tas[CTX->cur_dn_index].dn;
1105 dn = &CTX->ta_names[CTX->cur_dn_index];
1107 CTX->cur_dn_index ++;
1108 CTX->cur_dn = dn->data;
1109 CTX->cur_dn_len = dn->len;
1110 T0_PUSH(CTX->cur_dn_len);
1114 \ Copy a chunk of the current DN into the pad. Returned value is the
1115 \ chunk length; this is 0 when the end of the current DN is reached.
1116 cc: copy-dn-chunk ( -- len ) {
1119 clen = CTX->cur_dn_len;
1120 if (clen > sizeof ENG->pad) {
1121 clen = sizeof ENG->pad;
1123 memcpy(ENG->pad, CTX->cur_dn, clen);
1124 CTX->cur_dn += clen;
1125 CTX->cur_dn_len -= clen;
1129 \ Write a CertificateRequest message.
1130 : write-CertificateRequest ( -- )
1131 \ The list of client authentication types includes:
1134 \ rsa_fixed_ecdh (65)
1135 \ ecdsa_fixed_ecdh (66)
1136 \ rsa_sign and ecdsa_sign require, respectively, RSA and ECDSA
1137 \ support. Static ECDH requires that the cipher suite is ECDH.
1138 \ When we ask for static ECDH, we always send both rsa_fixed_ecdh
1139 \ and ecdsa_fixed_ecdh because what matters there is what the
1140 \ X.509 engine may support, and we do not control that.
1142 \ With TLS 1.2, we must also send a list of supported signature
1143 \ and hash algorithms. That list is supposed to qualify both
1144 \ the engine itself, and the X.509 validator, which are separate
1145 \ in BearSSL. There again, we use the engine capabilities in that
1146 \ list, and resort to a generic all-support list if only
1147 \ static ECDH is accepted.
1149 \ (In practice, client implementations tend to have at most one
1150 \ or two certificates, and send the chain regardless of what
1151 \ algorithms are used in it.)
1154 addr-version get16 0x0303 >= if
1155 2+ 0 write-list-signhash +
1157 ta-names-total-length + 3 +
1162 \ List of authentication methods
1163 0 write-list-auth write8 1 write-list-auth drop
1165 \ For TLS 1.2+, list of sign+hash
1166 addr-version get16 0x0303 >= if
1167 0 write-list-signhash write16 1 write-list-signhash drop
1170 \ Trust anchor names
1171 ta-names-total-length write16
1175 dup 0< if drop ret then write16
1176 begin copy-dn-chunk dup while
1177 addr-pad swap write-blob
1182 \ Write the Server Hello Done message.
1183 : write-ServerHelloDone ( -- )
1184 14 write8 0 write24 ;
1186 \ Perform RSA decryption of the client-sent pre-master secret. The value
1187 \ is in the pad, and its length is provided as parameter.
1188 cc: do-rsa-decrypt ( len prf_id -- ) {
1189 int prf_id = T0_POPi();
1190 size_t len = T0_POP();
1191 do_rsa_decrypt(CTX, prf_id, ENG->pad, len);
1194 \ Perform ECDH (not ECDHE). The point from the client is in the pad, and
1195 \ its length is provided as parameter.
1196 cc: do-ecdh ( len prf_id -- ) {
1197 int prf_id = T0_POPi();
1198 size_t len = T0_POP();
1199 do_ecdh(CTX, prf_id, ENG->pad, len);
1202 \ Do the second part of ECDHE.
1203 cc: do-ecdhe-part2 ( len prf_id -- ) {
1204 int prf_id = T0_POPi();
1205 size_t len = T0_POP();
1206 do_ecdhe_part2(CTX, prf_id, ENG->pad, len);
1209 \ Perform static ECDH. The point from the client is the public key
1210 \ extracted from its certificate.
1211 cc: do-static-ecdh ( prf_id -- ) {
1212 do_static_ecdh(CTX, T0_POP());
1215 \ Read a ClientKeyExchange header.
1216 : read-ClientKeyExchange-header ( -- len )
1217 read-handshake-header 16 = ifnot ERR_UNEXPECTED fail then ;
1219 \ Read the Client Key Exchange contents (non-empty case).
1220 : read-ClientKeyExchange-contents ( lim -- )
1221 \ What we should get depends on the cipher suite.
1222 addr-cipher_suite get16 use-rsa-keyx? if
1223 \ RSA key exchange: we expect a RSA-encrypted value.
1225 dup 512 > if ERR_LIMIT_EXCEEDED fail then
1227 addr-pad swap read-blob
1228 enc-rsa-len addr-cipher_suite get16 prf-id do-rsa-decrypt
1230 addr-cipher_suite get16 dup use-ecdhe? swap use-ecdh? { ecdhe ecdh }
1232 \ ECDH or ECDHE key exchange: we expect an EC point.
1233 read8 dup { ec-point-len }
1234 addr-pad swap read-blob
1235 ec-point-len addr-cipher_suite get16 prf-id
1236 ecdhe if do-ecdhe-part2 else do-ecdh then
1240 \ Read the Client Key Exchange (normal case).
1241 : read-ClientKeyExchange ( -- )
1242 read-ClientKeyExchange-header
1243 read-ClientKeyExchange-contents ;
1245 \ Obtain all possible hash values for handshake messages so far. This
1246 \ is done because we need the hash value for the CertificateVerify
1247 \ _before_ knowing which hash function will actually be used, as this
1248 \ information is obtained from decoding the message header itself.
1249 \ All hash values are stored in the pad (208 bytes in total).
1250 cc: compute-hash-CV ( -- ) {
1253 for (i = 1; i <= 6; i ++) {
1254 br_multihash_out(&ENG->mhash, i,
1255 ENG->pad + HASH_PAD_OFF[i - 1]);
1259 \ Copy the proper hash value from the pad into the dedicated buffer.
1260 \ Returned value is true (-1) on success, false (0) on error (error
1261 \ being an unimplemented hash function). The id has already been verified
1262 \ to be either 0 (for MD5+SHA-1) or one of the SHA-* functions.
1263 cc: copy-hash-CV ( hash_id -- bool ) {
1271 if (br_multihash_getimpl(&ENG->mhash, id) == 0) {
1275 off = HASH_PAD_OFF[id - 1];
1276 len = HASH_PAD_OFF[id] - off;
1278 memcpy(CTX->hash_CV, ENG->pad + off, len);
1279 CTX->hash_CV_len = len;
1280 CTX->hash_CV_id = id;
1284 \ Verify signature in CertificateVerify. Output is 0 on success, or a
1285 \ non-zero error code.
1286 cc: verify-CV-sig ( sig-len -- err ) {
1289 err = verify_CV_sig(CTX, T0_POP());
1293 \ Process static ECDH.
1294 : process-static-ECDH ( ktu -- )
1295 \ Static ECDH is allowed only if the cipher suite uses ECDH, and
1296 \ the client's public key has type EC and allows key exchange.
1297 \ BR_KEYTYPE_KEYX is 0x10, and BR_KEYTYPE_EC is 2.
1298 0x1F and 0x12 = ifnot ERR_WRONG_KEY_USAGE fail then
1299 addr-cipher_suite get16
1300 dup use-ecdh? ifnot ERR_UNEXPECTED fail then
1304 \ Read CertificateVerify header.
1305 : read-CertificateVerify-header ( -- lim )
1307 read-handshake-header 15 = ifnot ERR_UNEXPECTED fail then ;
1309 \ Read CertificateVerify. The client key type + usage is expected on the
1311 : read-CertificateVerify ( ktu -- )
1312 \ Check that the key allows for signatures.
1313 dup 0x20 and ifnot ERR_WRONG_KEY_USAGE fail then
1314 0x0F and { key-type }
1317 read-CertificateVerify-header
1319 \ With TLS 1.2+, there is an explicit hash + signature indication,
1320 \ which must be compatible with the key type.
1321 addr-version get16 0x0303 >= if
1322 \ Get hash function, then signature algorithm. The
1323 \ signature algorithm is 1 (RSA) or 3 (ECDSA) while our
1324 \ symbolic constants for key types are 1 (RSA) or 2 (EC).
1326 dup 0xFF and 1+ 1 >> key-type = ifnot
1327 ERR_BAD_SIGNATURE fail
1331 \ We support only SHA-1, SHA-224, SHA-256, SHA-384
1332 \ and SHA-512. We explicitly reject MD5.
1333 dup 2 < over 6 > or if ERR_INVALID_ALGORITHM fail then
1335 \ With TLS 1.0 and 1.1, hash is MD5+SHA-1 (0) for RSA,
1336 \ SHA-1 (2) for ECDSA.
1337 key-type 0x01 = if 0 else 2 then
1339 copy-hash-CV ifnot ERR_INVALID_ALGORITHM fail then
1342 read16 dup { sig-len }
1343 dup 512 > if ERR_LIMIT_EXCEEDED fail then
1344 addr-pad swap read-blob
1345 sig-len verify-CV-sig
1346 dup if fail then drop
1350 \ Send a HelloRequest.
1351 : send-HelloRequest ( -- )
1353 begin can-output? not while wait-co drop repeat
1354 22 addr-record_type_out set8
1355 0 write8 0 write24 flush-record
1356 23 addr-record_type_out set8 ;
1359 : do-handshake ( initial -- )
1360 0 addr-application_data set8
1361 22 addr-record_type_out set8
1362 0 addr-selected_protocol set16
1365 more-incoming-bytes? if ERR_UNEXPECTED fail then
1367 \ Session resumption
1369 0 write-CCS-Finished
1372 \ Not a session resumption
1374 write-Certificate drop
1375 write-ServerKeyExchange
1376 ta-names-total-length if
1377 write-CertificateRequest
1379 write-ServerHelloDone
1382 \ If we sent a CertificateRequest then we expect a
1383 \ Certificate message.
1384 ta-names-total-length if
1385 \ Read client certificate.
1390 \ Client certificate validation failed.
1391 2 flag? ifnot neg fail then
1393 read-ClientKeyExchange
1394 read-CertificateVerify-header
1398 \ Client sent no certificate at all.
1401 ERR_NO_CLIENT_AUTH fail
1403 read-ClientKeyExchange
1406 \ Client certificate was validated.
1407 read-ClientKeyExchange-header
1409 \ Empty ClientKeyExchange.
1413 read-ClientKeyExchange-contents
1414 read-CertificateVerify
1418 \ No client certificate request, we just expect
1419 \ a non-empty ClientKeyExchange.
1420 read-ClientKeyExchange
1423 0 write-CCS-Finished
1426 1 addr-application_data set8
1427 23 addr-record_type_out set8 ;
1431 \ Perform initial handshake.
1435 \ Wait for further invocation. At that point, we should
1436 \ get either an explicit call for renegotiation, or
1437 \ an incoming ClientHello handshake message.
1442 \ The best we can do is ask for a
1443 \ renegotiation, then wait for it
1449 \ Reject renegotiations if the peer does not
1450 \ support secure renegotiation, or if the
1451 \ "no renegotiation" flag is set.
1453 addr-reneg get8 1 = 1 flag? or if
1455 begin can-output? not while