summaryrefslogtreecommitdiffstats
path: root/security/nss/lib/ssl/dtlscon.c
blob: 09ceeac23cdce7b14893b38dc4329ca86e076bbf (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/*
 * DTLS Protocol
 */

#include "ssl.h"
#include "sslimpl.h"
#include "sslproto.h"

#ifndef PR_ARRAY_SIZE
#define PR_ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
#endif

static SECStatus dtls_TransmitMessageFlight(sslSocket *ss);
static SECStatus dtls_StartRetransmitTimer(sslSocket *ss);
static void dtls_RetransmitTimerExpiredCb(sslSocket *ss);
static SECStatus dtls_SendSavedWriteData(sslSocket *ss);
static void dtls_FinishedTimerCb(sslSocket *ss);

/* -28 adjusts for the IP/UDP header */
static const PRUint16 COMMON_MTU_VALUES[] = {
    1500 - 28, /* Ethernet MTU */
    1280 - 28, /* IPv6 minimum MTU */
    576 - 28,  /* Common assumption */
    256 - 28   /* We're in serious trouble now */
};

#define DTLS_COOKIE_BYTES 32

/* List copied from ssl3con.c:cipherSuites */
static const ssl3CipherSuite nonDTLSSuites[] = {
    TLS_ECDHE_ECDSA_WITH_RC4_128_SHA,
    TLS_ECDHE_RSA_WITH_RC4_128_SHA,
    TLS_DHE_DSS_WITH_RC4_128_SHA,
    TLS_ECDH_RSA_WITH_RC4_128_SHA,
    TLS_ECDH_ECDSA_WITH_RC4_128_SHA,
    TLS_RSA_WITH_RC4_128_MD5,
    TLS_RSA_WITH_RC4_128_SHA,
    0 /* End of list marker */
};

/* Map back and forth between TLS and DTLS versions in wire format.
 * Mapping table is:
 *
 * TLS             DTLS
 * 1.1 (0302)      1.0 (feff)
 * 1.2 (0303)      1.2 (fefd)
 * 1.3 (0304)      1.3 (fefc)
 */
SSL3ProtocolVersion
dtls_TLSVersionToDTLSVersion(SSL3ProtocolVersion tlsv)
{
    if (tlsv == SSL_LIBRARY_VERSION_TLS_1_1) {
        return SSL_LIBRARY_VERSION_DTLS_1_0_WIRE;
    }
    if (tlsv == SSL_LIBRARY_VERSION_TLS_1_2) {
        return SSL_LIBRARY_VERSION_DTLS_1_2_WIRE;
    }
    if (tlsv == SSL_LIBRARY_VERSION_TLS_1_3) {
        return SSL_LIBRARY_VERSION_DTLS_1_3_WIRE;
    }

    /* Anything other than TLS 1.1 or 1.2 is an error, so return
     * the invalid version 0xffff. */
    return 0xffff;
}

/* Map known DTLS versions to known TLS versions.
 * - Invalid versions (< 1.0) return a version of 0
 * - Versions > known return a version one higher than we know of
 * to accomodate a theoretically newer version */
SSL3ProtocolVersion
dtls_DTLSVersionToTLSVersion(SSL3ProtocolVersion dtlsv)
{
    if (MSB(dtlsv) == 0xff) {
        return 0;
    }

    if (dtlsv == SSL_LIBRARY_VERSION_DTLS_1_0_WIRE) {
        return SSL_LIBRARY_VERSION_TLS_1_1;
    }
    /* Handle the skipped version of DTLS 1.1 by returning
     * an error. */
    if (dtlsv == ((~0x0101) & 0xffff)) {
        return 0;
    }
    if (dtlsv == SSL_LIBRARY_VERSION_DTLS_1_2_WIRE) {
        return SSL_LIBRARY_VERSION_TLS_1_2;
    }
    if (dtlsv == SSL_LIBRARY_VERSION_DTLS_1_3_WIRE) {
        return SSL_LIBRARY_VERSION_TLS_1_3;
    }

    /* Return a fictional higher version than we know of */
    return SSL_LIBRARY_VERSION_MAX_SUPPORTED + 1;
}

/* On this socket, Disable non-DTLS cipher suites in the argument's list */
SECStatus
ssl3_DisableNonDTLSSuites(sslSocket *ss)
{
    const ssl3CipherSuite *suite;

    for (suite = nonDTLSSuites; *suite; ++suite) {
        PORT_CheckSuccess(ssl3_CipherPrefSet(ss, *suite, PR_FALSE));
    }
    return SECSuccess;
}

/* Allocate a DTLSQueuedMessage.
 *
 * Called from dtls_QueueMessage()
 */
static DTLSQueuedMessage *
dtls_AllocQueuedMessage(ssl3CipherSpec *cwSpec, SSL3ContentType type,
                        const unsigned char *data, PRUint32 len)
{
    DTLSQueuedMessage *msg = NULL;

    msg = PORT_ZAlloc(sizeof(DTLSQueuedMessage));
    if (!msg)
        return NULL;

    msg->data = PORT_Alloc(len);
    if (!msg->data) {
        PORT_Free(msg);
        return NULL;
    }
    PORT_Memcpy(msg->data, data, len);

    msg->len = len;
    msg->cwSpec = cwSpec;
    msg->type = type;
    /* Safe if we are < 1.3, since the refct is
     * already very high. */
    tls13_CipherSpecAddRef(cwSpec);

    return msg;
}

/*
 * Free a handshake message
 *
 * Called from dtls_FreeHandshakeMessages()
 */
void
dtls_FreeHandshakeMessage(DTLSQueuedMessage *msg)
{
    if (!msg)
        return;

    /* Safe if we are < 1.3, since the refct is
     * already very high. */
    tls13_CipherSpecRelease(msg->cwSpec);
    PORT_ZFree(msg->data, msg->len);
    PORT_Free(msg);
}

/*
 * Free a list of handshake messages
 *
 * Called from:
 *              dtls_HandleHandshake()
 *              ssl3_DestroySSL3Info()
 */
void
dtls_FreeHandshakeMessages(PRCList *list)
{
    PRCList *cur_p;

    while (!PR_CLIST_IS_EMPTY(list)) {
        cur_p = PR_LIST_TAIL(list);
        PR_REMOVE_LINK(cur_p);
        dtls_FreeHandshakeMessage((DTLSQueuedMessage *)cur_p);
    }
}

/* Called by dtls_HandleHandshake() and dtls_MaybeRetransmitHandshake() if a
 * handshake message retransmission is detected. */
static SECStatus
dtls_RetransmitDetected(sslSocket *ss)
{
    SECStatus rv = SECSuccess;

    PORT_Assert(ss->opt.noLocks || ssl_HaveRecvBufLock(ss));
    PORT_Assert(ss->opt.noLocks || ssl_HaveSSL3HandshakeLock(ss));

    if (ss->ssl3.hs.rtTimerCb == dtls_RetransmitTimerExpiredCb) {
        /* Check to see if we retransmitted recently. If so,
         * suppress the triggered retransmit. This avoids
         * retransmit wars after packet loss.
         * This is not in RFC 5346 but it should be.
         */
        if ((PR_IntervalNow() - ss->ssl3.hs.rtTimerStarted) >
            (ss->ssl3.hs.rtTimeoutMs / 4)) {
            SSL_TRC(30,
                    ("%d: SSL3[%d]: Shortcutting retransmit timer",
                     SSL_GETPID(), ss->fd));

            /* Cancel the timer and call the CB,
             * which re-arms the timer */
            dtls_CancelTimer(ss);
            dtls_RetransmitTimerExpiredCb(ss);
        } else {
            SSL_TRC(30,
                    ("%d: SSL3[%d]: Ignoring retransmission: "
                     "last retransmission %dms ago, suppressed for %dms",
                     SSL_GETPID(), ss->fd,
                     PR_IntervalNow() - ss->ssl3.hs.rtTimerStarted,
                     ss->ssl3.hs.rtTimeoutMs / 4));
        }

    } else if (ss->ssl3.hs.rtTimerCb == dtls_FinishedTimerCb) {
        SSL_TRC(30, ("%d: SSL3[%d]: Retransmit detected in holddown",
                     SSL_GETPID(), ss->fd));
        /* Retransmit the messages and re-arm the timer
         * Note that we are not backing off the timer here.
         * The spec isn't clear and my reasoning is that this
         * may be a re-ordered packet rather than slowness,
         * so let's be aggressive. */
        dtls_CancelTimer(ss);
        rv = dtls_TransmitMessageFlight(ss);
        if (rv == SECSuccess) {
            rv = dtls_StartHolddownTimer(ss);
        }

    } else {
        PORT_Assert(ss->ssl3.hs.rtTimerCb == NULL);
        /* ... and ignore it. */
    }
    return rv;
}

/* Called only from ssl3_HandleRecord, for each (deciphered) DTLS record.
 * origBuf is the decrypted ssl record content and is expected to contain
 * complete handshake records
 * Caller must hold the handshake and RecvBuf locks.
 *
 * Note that this code uses msg_len for two purposes:
 *
 * (1) To pass the length to ssl3_HandleHandshakeMessage()
 * (2) To carry the length of a message currently being reassembled
 *
 * However, unlike ssl3_HandleHandshake(), it is not used to carry
 * the state of reassembly (i.e., whether one is in progress). That
 * is carried in recvdHighWater and recvdFragments.
 */
#define OFFSET_BYTE(o) (o / 8)
#define OFFSET_MASK(o) (1 << (o % 8))

SECStatus
dtls_HandleHandshake(sslSocket *ss, sslBuffer *origBuf)
{
    /* XXX OK for now.
     * This doesn't work properly with asynchronous certificate validation.
     * because that returns a WOULDBLOCK error. The current DTLS
     * applications do not need asynchronous validation, but in the
     * future we will need to add this.
     */
    sslBuffer buf = *origBuf;
    SECStatus rv = SECSuccess;

    PORT_Assert(ss->opt.noLocks || ssl_HaveRecvBufLock(ss));
    PORT_Assert(ss->opt.noLocks || ssl_HaveSSL3HandshakeLock(ss));

    while (buf.len > 0) {
        PRUint8 type;
        PRUint32 message_length;
        PRUint16 message_seq;
        PRUint32 fragment_offset;
        PRUint32 fragment_length;
        PRUint32 offset;

        if (buf.len < 12) {
            PORT_SetError(SSL_ERROR_RX_MALFORMED_HANDSHAKE);
            rv = SECFailure;
            break;
        }

        /* Parse the header */
        type = buf.buf[0];
        message_length = (buf.buf[1] << 16) | (buf.buf[2] << 8) | buf.buf[3];
        message_seq = (buf.buf[4] << 8) | buf.buf[5];
        fragment_offset = (buf.buf[6] << 16) | (buf.buf[7] << 8) | buf.buf[8];
        fragment_length = (buf.buf[9] << 16) | (buf.buf[10] << 8) | buf.buf[11];

#define MAX_HANDSHAKE_MSG_LEN 0x1ffff /* 128k - 1 */
        if (message_length > MAX_HANDSHAKE_MSG_LEN) {
            (void)ssl3_DecodeError(ss);
            PORT_SetError(SSL_ERROR_RX_MALFORMED_HANDSHAKE);
            return SECFailure;
        }
#undef MAX_HANDSHAKE_MSG_LEN

        buf.buf += 12;
        buf.len -= 12;

        /* This fragment must be complete */
        if (buf.len < fragment_length) {
            PORT_SetError(SSL_ERROR_RX_MALFORMED_HANDSHAKE);
            rv = SECFailure;
            break;
        }

        /* Sanity check the packet contents */
        if ((fragment_length + fragment_offset) > message_length) {
            PORT_SetError(SSL_ERROR_RX_MALFORMED_HANDSHAKE);
            rv = SECFailure;
            break;
        }

        /* There are three ways we could not be ready for this packet.
         *
         * 1. It's a partial next message.
         * 2. It's a partial or complete message beyond the next
         * 3. It's a message we've already seen
         *
         * If it's the complete next message we accept it right away.
         * This is the common case for short messages
         */
        if ((message_seq == ss->ssl3.hs.recvMessageSeq) &&
            (fragment_offset == 0) &&
            (fragment_length == message_length)) {
            /* Complete next message. Process immediately */
            ss->ssl3.hs.msg_type = (SSL3HandshakeType)type;
            ss->ssl3.hs.msg_len = message_length;

            /* At this point we are advancing our state machine, so
             * we can free our last flight of messages */
            dtls_FreeHandshakeMessages(&ss->ssl3.hs.lastMessageFlight);
            ss->ssl3.hs.recvdHighWater = -1;
            dtls_CancelTimer(ss);

            /* Reset the timer to the initial value if the retry counter
             * is 0, per Sec. 4.2.4.1 */
            if (ss->ssl3.hs.rtRetries == 0) {
                ss->ssl3.hs.rtTimeoutMs = DTLS_RETRANSMIT_INITIAL_MS;
            }

            rv = ssl3_HandleHandshakeMessage(ss, buf.buf, ss->ssl3.hs.msg_len,
                                             buf.len == fragment_length);
            if (rv == SECFailure) {
                /* Do not attempt to process rest of messages in this record */
                break;
            }
        } else {
            if (message_seq < ss->ssl3.hs.recvMessageSeq) {
                /* Case 3: we do an immediate retransmit if we're
                 * in a waiting state. */
                rv = dtls_RetransmitDetected(ss);
                break;
            } else if (message_seq > ss->ssl3.hs.recvMessageSeq) {
                /* Case 2
                 *
                 * Ignore this message. This means we don't handle out of
                 * order complete messages that well, but we're still
                 * compliant and this probably does not happen often
                 *
                 * XXX OK for now. Maybe do something smarter at some point?
                 */
            } else {
                /* Case 1
                 *
                 * Buffer the fragment for reassembly
                 */
                /* Make room for the message */
                if (ss->ssl3.hs.recvdHighWater == -1) {
                    PRUint32 map_length = OFFSET_BYTE(message_length) + 1;

                    rv = sslBuffer_Grow(&ss->ssl3.hs.msg_body, message_length);
                    if (rv != SECSuccess)
                        break;
                    /* Make room for the fragment map */
                    rv = sslBuffer_Grow(&ss->ssl3.hs.recvdFragments,
                                        map_length);
                    if (rv != SECSuccess)
                        break;

                    /* Reset the reassembly map */
                    ss->ssl3.hs.recvdHighWater = 0;
                    PORT_Memset(ss->ssl3.hs.recvdFragments.buf, 0,
                                ss->ssl3.hs.recvdFragments.space);
                    ss->ssl3.hs.msg_type = (SSL3HandshakeType)type;
                    ss->ssl3.hs.msg_len = message_length;
                }

                /* If we have a message length mismatch, abandon the reassembly
                 * in progress and hope that the next retransmit will give us
                 * something sane
                 */
                if (message_length != ss->ssl3.hs.msg_len) {
                    ss->ssl3.hs.recvdHighWater = -1;
                    PORT_SetError(SSL_ERROR_RX_MALFORMED_HANDSHAKE);
                    rv = SECFailure;
                    break;
                }

                /* Now copy this fragment into the buffer */
                PORT_Assert((fragment_offset + fragment_length) <=
                            ss->ssl3.hs.msg_body.space);
                PORT_Memcpy(ss->ssl3.hs.msg_body.buf + fragment_offset,
                            buf.buf, fragment_length);

                /* This logic is a bit tricky. We have two values for
                 * reassembly state:
                 *
                 * - recvdHighWater contains the highest contiguous number of
                 *   bytes received
                 * - recvdFragments contains a bitmask of packets received
                 *   above recvdHighWater
                 *
                 * This avoids having to fill in the bitmask in the common
                 * case of adjacent fragments received in sequence
                 */
                if (fragment_offset <= (unsigned int)ss->ssl3.hs.recvdHighWater) {
                    /* Either this is the adjacent fragment or an overlapping
                     * fragment */
                    ss->ssl3.hs.recvdHighWater = fragment_offset +
                                                 fragment_length;
                } else {
                    for (offset = fragment_offset;
                         offset < fragment_offset + fragment_length;
                         offset++) {
                        ss->ssl3.hs.recvdFragments.buf[OFFSET_BYTE(offset)] |=
                            OFFSET_MASK(offset);
                    }
                }

                /* Now figure out the new high water mark if appropriate */
                for (offset = ss->ssl3.hs.recvdHighWater;
                     offset < ss->ssl3.hs.msg_len; offset++) {
                    /* Note that this loop is not efficient, since it counts
                     * bit by bit. If we have a lot of out-of-order packets,
                     * we should optimize this */
                    if (ss->ssl3.hs.recvdFragments.buf[OFFSET_BYTE(offset)] &
                        OFFSET_MASK(offset)) {
                        ss->ssl3.hs.recvdHighWater++;
                    } else {
                        break;
                    }
                }

                /* If we have all the bytes, then we are good to go */
                if (ss->ssl3.hs.recvdHighWater == ss->ssl3.hs.msg_len) {
                    ss->ssl3.hs.recvdHighWater = -1;

                    rv = ssl3_HandleHandshakeMessage(
                        ss,
                        ss->ssl3.hs.msg_body.buf, ss->ssl3.hs.msg_len,
                        buf.len == fragment_length);
                    if (rv == SECFailure)
                        break; /* Skip rest of record */

                    /* At this point we are advancing our state machine, so
                     * we can free our last flight of messages */
                    dtls_FreeHandshakeMessages(&ss->ssl3.hs.lastMessageFlight);
                    dtls_CancelTimer(ss);

                    /* If there have been no retries this time, reset the
                     * timer value to the default per Section 4.2.4.1 */
                    if (ss->ssl3.hs.rtRetries == 0) {
                        ss->ssl3.hs.rtTimeoutMs = DTLS_RETRANSMIT_INITIAL_MS;
                    }
                }
            }
        }

        buf.buf += fragment_length;
        buf.len -= fragment_length;
    }

    origBuf->len = 0; /* So ssl3_GatherAppDataRecord will keep looping. */

    /* XXX OK for now. In future handle rv == SECWouldBlock safely in order
     * to deal with asynchronous certificate verification */
    return rv;
}

/* Enqueue a message (either handshake or CCS)
 *
 * Called from:
 *              dtls_StageHandshakeMessage()
 *              ssl3_SendChangeCipherSpecs()
 */
SECStatus
dtls_QueueMessage(sslSocket *ss, SSL3ContentType type,
                  const SSL3Opaque *pIn, PRInt32 nIn)
{
    SECStatus rv = SECSuccess;
    DTLSQueuedMessage *msg = NULL;
    ssl3CipherSpec *spec;

    PORT_Assert(ss->opt.noLocks || ssl_HaveSSL3HandshakeLock(ss));
    PORT_Assert(ss->opt.noLocks || ssl_HaveXmitBufLock(ss));

    spec = ss->ssl3.cwSpec;
    msg = dtls_AllocQueuedMessage(spec, type, pIn, nIn);

    if (!msg) {
        PORT_SetError(SEC_ERROR_NO_MEMORY);
        rv = SECFailure;
    } else {
        PR_APPEND_LINK(&msg->link, &ss->ssl3.hs.lastMessageFlight);
    }

    return rv;
}

/* Add DTLS handshake message to the pending queue
 * Empty the sendBuf buffer.
 * This function returns SECSuccess or SECFailure, never SECWouldBlock.
 * Always set sendBuf.len to 0, even when returning SECFailure.
 *
 * Called from:
 *              ssl3_AppendHandshakeHeader()
 *              dtls_FlushHandshake()
 */
SECStatus
dtls_StageHandshakeMessage(sslSocket *ss)
{
    SECStatus rv = SECSuccess;

    PORT_Assert(ss->opt.noLocks || ssl_HaveSSL3HandshakeLock(ss));
    PORT_Assert(ss->opt.noLocks || ssl_HaveXmitBufLock(ss));

    /* This function is sometimes called when no data is actually to
     * be staged, so just return SECSuccess. */
    if (!ss->sec.ci.sendBuf.buf || !ss->sec.ci.sendBuf.len)
        return rv;

    rv = dtls_QueueMessage(ss, content_handshake,
                           ss->sec.ci.sendBuf.buf, ss->sec.ci.sendBuf.len);

    /* Whether we succeeded or failed, toss the old handshake data. */
    ss->sec.ci.sendBuf.len = 0;
    return rv;
}

/* Enqueue the handshake message in sendBuf (if any) and then
 * transmit the resulting flight of handshake messages.
 *
 * Called from:
 *              ssl3_FlushHandshake()
 */
SECStatus
dtls_FlushHandshakeMessages(sslSocket *ss, PRInt32 flags)
{
    SECStatus rv = SECSuccess;

    PORT_Assert(ss->opt.noLocks || ssl_HaveSSL3HandshakeLock(ss));
    PORT_Assert(ss->opt.noLocks || ssl_HaveXmitBufLock(ss));

    rv = dtls_StageHandshakeMessage(ss);
    if (rv != SECSuccess)
        return rv;

    if (!(flags & ssl_SEND_FLAG_FORCE_INTO_BUFFER)) {
        rv = dtls_TransmitMessageFlight(ss);
        if (rv != SECSuccess) {
            return rv;
        }

        if (!(flags & ssl_SEND_FLAG_NO_RETRANSMIT)) {
            rv = dtls_StartRetransmitTimer(ss);
        }
    }

    return rv;
}

/* The callback for when the retransmit timer expires
 *
 * Called from:
 *              dtls_CheckTimer()
 *              dtls_HandleHandshake()
 */
static void
dtls_RetransmitTimerExpiredCb(sslSocket *ss)
{
    SECStatus rv;

    ss->ssl3.hs.rtRetries++;

    if (!(ss->ssl3.hs.rtRetries % 3)) {
        /* If one of the messages was potentially greater than > MTU,
         * then downgrade. Do this every time we have retransmitted a
         * message twice, per RFC 6347 Sec. 4.1.1 */
        dtls_SetMTU(ss, ss->ssl3.hs.maxMessageSent - 1);
    }

    rv = dtls_TransmitMessageFlight(ss);
    if (rv == SECSuccess) {
        /* Re-arm the timer */
        ss->ssl3.hs.rtTimeoutMs *= 2;
        if (ss->ssl3.hs.rtTimeoutMs > DTLS_RETRANSMIT_MAX_MS) {
            ss->ssl3.hs.rtTimeoutMs = DTLS_RETRANSMIT_MAX_MS;
        }

        ss->ssl3.hs.rtTimerStarted = PR_IntervalNow();
        ss->ssl3.hs.rtTimerCb = dtls_RetransmitTimerExpiredCb;

        SSL_TRC(30,
                ("%d: SSL3[%d]: Retransmit #%d, next in %d",
                 SSL_GETPID(), ss->fd,
                 ss->ssl3.hs.rtRetries, ss->ssl3.hs.rtTimeoutMs));
    }
    /* else: OK for now. In future maybe signal the stack that we couldn't
     * transmit. For now, let the read handle any real network errors */
}

/* Transmit a flight of handshake messages, stuffing them
 * into as few records as seems reasonable
 *
 * Called from:
 *             dtls_FlushHandshake()
 *             dtls_RetransmitTimerExpiredCb()
 */
static SECStatus
dtls_TransmitMessageFlight(sslSocket *ss)
{
    SECStatus rv = SECSuccess;
    PRCList *msg_p;
    PRUint16 room_left = ss->ssl3.mtu;
    PRInt32 sent;

    ssl_GetXmitBufLock(ss);
    ssl_GetSpecReadLock(ss);

    /* DTLS does not buffer its handshake messages in
     * ss->pendingBuf, but rather in the lastMessageFlight
     * structure. This is just a sanity check that
     * some programming error hasn't inadvertantly
     * stuffed something in ss->pendingBuf
     */
    PORT_Assert(!ss->pendingBuf.len);
    for (msg_p = PR_LIST_HEAD(&ss->ssl3.hs.lastMessageFlight);
         msg_p != &ss->ssl3.hs.lastMessageFlight;
         msg_p = PR_NEXT_LINK(msg_p)) {
        DTLSQueuedMessage *msg = (DTLSQueuedMessage *)msg_p;

        /* The logic here is:
         *
         * 1. If this is a message that will not fit into the remaining
         *    space, then flush.
         * 2. If the message will now fit into the remaining space,
         *    encrypt, buffer, and loop.
         * 3. If the message will not fit, then fragment.
         *
         * At the end of the function, flush.
         */
        if ((msg->len + SSL3_BUFFER_FUDGE) > room_left) {
            /* The message will not fit into the remaining space, so flush */
            rv = dtls_SendSavedWriteData(ss);
            if (rv != SECSuccess)
                break;

            room_left = ss->ssl3.mtu;
        }

        if ((msg->len + SSL3_BUFFER_FUDGE) <= room_left) {
            /* The message will fit, so encrypt and then continue with the
             * next packet */
            sent = ssl3_SendRecord(ss, msg->cwSpec, msg->type,
                                   msg->data, msg->len,
                                   ssl_SEND_FLAG_FORCE_INTO_BUFFER);
            if (sent != msg->len) {
                rv = SECFailure;
                if (sent != -1) {
                    PORT_SetError(SEC_ERROR_LIBRARY_FAILURE);
                }
                break;
            }

            room_left = ss->ssl3.mtu - ss->pendingBuf.len;
        } else {
            /* The message will not fit, so fragment.
             *
             * XXX OK for now. Arrange to coalesce the last fragment
             * of this message with the next message if possible.
             * That would be more efficient.
             */
            PRUint32 fragment_offset = 0;
            unsigned char fragment[DTLS_MAX_MTU]; /* >= than largest
                                                   * plausible MTU */

            /* Assert that we have already flushed */
            PORT_Assert(room_left == ss->ssl3.mtu);

            /* Case 3: We now need to fragment this message
             * DTLS only supports fragmenting handshaking messages */
            PORT_Assert(msg->type == content_handshake);

            /* The headers consume 12 bytes so the smalles possible
             *  message (i.e., an empty one) is 12 bytes
             */
            PORT_Assert(msg->len >= 12);

            while ((fragment_offset + 12) < msg->len) {
                PRUint32 fragment_len;
                const unsigned char *content = msg->data + 12;
                PRUint32 content_len = msg->len - 12;

                /* The reason we use 8 here is that that's the length of
                 * the new DTLS data that we add to the header */
                fragment_len = PR_MIN((PRUint32)room_left - (SSL3_BUFFER_FUDGE + 8),
                                      content_len - fragment_offset);
                PORT_Assert(fragment_len < DTLS_MAX_MTU - 12);
                /* Make totally sure that we are within the buffer.
                 * Note that the only way that fragment len could get
                 * adjusted here is if
                 *
                 * (a) we are in release mode so the PORT_Assert is compiled out
                 * (b) either the MTU table is inconsistent with DTLS_MAX_MTU
                 * or ss->ssl3.mtu has become corrupt.
                 */
                fragment_len = PR_MIN(fragment_len, DTLS_MAX_MTU - 12);

                /* Construct an appropriate-sized fragment */
                /* Type, length, sequence */
                PORT_Memcpy(fragment, msg->data, 6);

                /* Offset */
                fragment[6] = (fragment_offset >> 16) & 0xff;
                fragment[7] = (fragment_offset >> 8) & 0xff;
                fragment[8] = (fragment_offset)&0xff;

                /* Fragment length */
                fragment[9] = (fragment_len >> 16) & 0xff;
                fragment[10] = (fragment_len >> 8) & 0xff;
                fragment[11] = (fragment_len)&0xff;

                PORT_Memcpy(fragment + 12, content + fragment_offset,
                            fragment_len);

                /*
                 *  Send the record. We do this in two stages
                 * 1. Encrypt
                 */
                sent = ssl3_SendRecord(ss, msg->cwSpec, msg->type,
                                       fragment, fragment_len + 12,
                                       ssl_SEND_FLAG_FORCE_INTO_BUFFER);
                if (sent != (fragment_len + 12)) {
                    rv = SECFailure;
                    if (sent != -1) {
                        PORT_SetError(SEC_ERROR_LIBRARY_FAILURE);
                    }
                    break;
                }

                /* 2. Flush */
                rv = dtls_SendSavedWriteData(ss);
                if (rv != SECSuccess)
                    break;

                fragment_offset += fragment_len;
            }
        }
    }

    /* Finally, we need to flush */
    if (rv == SECSuccess)
        rv = dtls_SendSavedWriteData(ss);

    /* Give up the locks */
    ssl_ReleaseSpecReadLock(ss);
    ssl_ReleaseXmitBufLock(ss);

    return rv;
}

/* Flush the data in the pendingBuf and update the max message sent
 * so we can adjust the MTU estimate if we need to.
 * Wrapper for ssl_SendSavedWriteData.
 *
 * Called from dtls_TransmitMessageFlight()
 */
static SECStatus
dtls_SendSavedWriteData(sslSocket *ss)
{
    PRInt32 sent;

    sent = ssl_SendSavedWriteData(ss);
    if (sent < 0)
        return SECFailure;

    /* We should always have complete writes b/c datagram sockets
     * don't really block */
    if (ss->pendingBuf.len > 0) {
        ssl_MapLowLevelError(SSL_ERROR_SOCKET_WRITE_FAILURE);
        return SECFailure;
    }

    /* Update the largest message sent so we can adjust the MTU
     * estimate if necessary */
    if (sent > ss->ssl3.hs.maxMessageSent)
        ss->ssl3.hs.maxMessageSent = sent;

    return SECSuccess;
}

static SECStatus
dtls_StartTimer(sslSocket *ss, PRUint32 time, DTLSTimerCb cb)
{
    PORT_Assert(ss->ssl3.hs.rtTimerCb == NULL);

    ss->ssl3.hs.rtRetries = 0;
    ss->ssl3.hs.rtTimerStarted = PR_IntervalNow();
    ss->ssl3.hs.rtTimeoutMs = time;
    ss->ssl3.hs.rtTimerCb = cb;
    return SECSuccess;
}

/* Start a timer for retransmission. */
static SECStatus
dtls_StartRetransmitTimer(sslSocket *ss)
{
    return dtls_StartTimer(ss, DTLS_RETRANSMIT_INITIAL_MS,
                           dtls_RetransmitTimerExpiredCb);
}

/* Start a timer for holding an old cipher spec. */
SECStatus
dtls_StartHolddownTimer(sslSocket *ss)
{
    return dtls_StartTimer(ss, DTLS_RETRANSMIT_FINISHED_MS,
                           dtls_FinishedTimerCb);
}

/* Cancel a pending timer
 *
 * Called from:
 *              dtls_HandleHandshake()
 *              dtls_CheckTimer()
 */
void
dtls_CancelTimer(sslSocket *ss)
{
    PORT_Assert(ss->opt.noLocks || ssl_HaveRecvBufLock(ss));

    ss->ssl3.hs.rtTimerCb = NULL;
}

/* Check the pending timer and fire the callback if it expired
 *
 * Called from ssl3_GatherCompleteHandshake()
 */
void
dtls_CheckTimer(sslSocket *ss)
{
    ssl_GetSSL3HandshakeLock(ss);
    if (!ss->ssl3.hs.rtTimerCb) {
        ssl_ReleaseSSL3HandshakeLock(ss);
        return;
    }

    if ((PR_IntervalNow() - ss->ssl3.hs.rtTimerStarted) >
        PR_MillisecondsToInterval(ss->ssl3.hs.rtTimeoutMs)) {
        /* Timer has expired */
        DTLSTimerCb cb = ss->ssl3.hs.rtTimerCb;

        /* Cancel the timer so that we can call the CB safely */
        dtls_CancelTimer(ss);

        /* Now call the CB */
        cb(ss);
    }
    ssl_ReleaseSSL3HandshakeLock(ss);
}

/* The callback to fire when the holddown timer for the Finished
 * message expires and we can delete it
 *
 * Called from dtls_CheckTimer()
 */
static void
dtls_FinishedTimerCb(sslSocket *ss)
{
    dtls_FreeHandshakeMessages(&ss->ssl3.hs.lastMessageFlight);
    if (ss->version < SSL_LIBRARY_VERSION_TLS_1_3) {
        ssl3_DestroyCipherSpec(ss->ssl3.pwSpec, PR_FALSE);
    }
}

/* Cancel the Finished hold-down timer and destroy the
 * pending cipher spec. Note that this means that
 * successive rehandshakes will fail if the Finished is
 * lost.
 *
 * XXX OK for now. Figure out how to handle the combination
 * of Finished lost and rehandshake
 */
void
dtls_RehandshakeCleanup(sslSocket *ss)
{
    /* Skip this if we are handling a second ClientHello. */
    if (ss->ssl3.hs.helloRetry) {
        return;
    }
    PORT_Assert((ss->version < SSL_LIBRARY_VERSION_TLS_1_3));
    dtls_CancelTimer(ss);
    ssl3_DestroyCipherSpec(ss->ssl3.pwSpec, PR_FALSE);
    ss->ssl3.hs.sendMessageSeq = 0;
    ss->ssl3.hs.recvMessageSeq = 0;
}

/* Set the MTU to the next step less than or equal to the
 * advertised value. Also used to downgrade the MTU by
 * doing dtls_SetMTU(ss, biggest packet set).
 *
 * Passing 0 means set this to the largest MTU known
 * (effectively resetting the PMTU backoff value).
 *
 * Called by:
 *            ssl3_InitState()
 *            dtls_RetransmitTimerExpiredCb()
 */
void
dtls_SetMTU(sslSocket *ss, PRUint16 advertised)
{
    int i;

    if (advertised == 0) {
        ss->ssl3.mtu = COMMON_MTU_VALUES[0];
        SSL_TRC(30, ("Resetting MTU to %d", ss->ssl3.mtu));
        return;
    }

    for (i = 0; i < PR_ARRAY_SIZE(COMMON_MTU_VALUES); i++) {
        if (COMMON_MTU_VALUES[i] <= advertised) {
            ss->ssl3.mtu = COMMON_MTU_VALUES[i];
            SSL_TRC(30, ("Resetting MTU to %d", ss->ssl3.mtu));
            return;
        }
    }

    /* Fallback */
    ss->ssl3.mtu = COMMON_MTU_VALUES[PR_ARRAY_SIZE(COMMON_MTU_VALUES) - 1];
    SSL_TRC(30, ("Resetting MTU to %d", ss->ssl3.mtu));
}

/* Called from ssl3_HandleHandshakeMessage() when it has deciphered a
 * DTLS hello_verify_request
 * Caller must hold Handshake and RecvBuf locks.
 */
SECStatus
dtls_HandleHelloVerifyRequest(sslSocket *ss, SSL3Opaque *b, PRUint32 length)
{
    int errCode = SSL_ERROR_RX_MALFORMED_HELLO_VERIFY_REQUEST;
    SECStatus rv;
    SSL3ProtocolVersion temp;
    SSL3AlertDescription desc = illegal_parameter;

    SSL_TRC(3, ("%d: SSL3[%d]: handle hello_verify_request handshake",
                SSL_GETPID(), ss->fd));
    PORT_Assert(ss->opt.noLocks || ssl_HaveRecvBufLock(ss));
    PORT_Assert(ss->opt.noLocks || ssl_HaveSSL3HandshakeLock(ss));

    if (ss->ssl3.hs.ws != wait_server_hello) {
        errCode = SSL_ERROR_RX_UNEXPECTED_HELLO_VERIFY_REQUEST;
        desc = unexpected_message;
        goto alert_loser;
    }

    /* The version.
     *
     * RFC 4347 required that you verify that the server versions
     * match (Section 4.2.1) in the HelloVerifyRequest and the
     * ServerHello.
     *
     * RFC 6347 suggests (SHOULD) that servers always use 1.0 in
     * HelloVerifyRequest and allows the versions not to match,
     * especially when 1.2 is being negotiated.
     *
     * Therefore we do not do anything to enforce a match, just
     * read and check that this value is sane.
     */
    rv = ssl_ClientReadVersion(ss, &b, &length, &temp);
    if (rv != SECSuccess) {
        goto loser; /* alert has been sent */
    }

    /* Read the cookie.
     * IMPORTANT: The value of ss->ssl3.hs.cookie is only valid while the
     * HelloVerifyRequest message remains valid. */
    rv = ssl3_ConsumeHandshakeVariable(ss, &ss->ssl3.hs.cookie, 1, &b, &length);
    if (rv != SECSuccess) {
        goto loser; /* alert has been sent */
    }
    if (ss->ssl3.hs.cookie.len > DTLS_COOKIE_BYTES) {
        desc = decode_error;
        goto alert_loser; /* malformed. */
    }

    ssl_GetXmitBufLock(ss); /*******************************/

    /* Now re-send the client hello */
    rv = ssl3_SendClientHello(ss, client_hello_retransmit);

    ssl_ReleaseXmitBufLock(ss); /*******************************/

    if (rv == SECSuccess)
        return rv;

alert_loser:
    (void)SSL3_SendAlert(ss, alert_fatal, desc);

loser:
    ssl_MapLowLevelError(errCode);
    return SECFailure;
}

/* Initialize the DTLS anti-replay window
 *
 * Called from:
 *              ssl3_SetupPendingCipherSpec()
 *              ssl3_InitCipherSpec()
 */
void
dtls_InitRecvdRecords(DTLSRecvdRecords *records)
{
    PORT_Memset(records->data, 0, sizeof(records->data));
    records->left = 0;
    records->right = DTLS_RECVD_RECORDS_WINDOW - 1;
}

/*
 * Has this DTLS record been received? Return values are:
 * -1 -- out of range to the left
 *  0 -- not received yet
 *  1 -- replay
 *
 *  Called from: ssl3_HandleRecord()
 */
int
dtls_RecordGetRecvd(const DTLSRecvdRecords *records, sslSequenceNumber seq)
{
    PRUint64 offset;

    /* Out of range to the left */
    if (seq < records->left) {
        return -1;
    }

    /* Out of range to the right; since we advance the window on
     * receipt, that means that this packet has not been received
     * yet */
    if (seq > records->right)
        return 0;

    offset = seq % DTLS_RECVD_RECORDS_WINDOW;

    return !!(records->data[offset / 8] & (1 << (offset % 8)));
}

/* Update the DTLS anti-replay window
 *
 * Called from ssl3_HandleRecord()
 */
void
dtls_RecordSetRecvd(DTLSRecvdRecords *records, sslSequenceNumber seq)
{
    PRUint64 offset;

    if (seq < records->left)
        return;

    if (seq > records->right) {
        sslSequenceNumber new_left;
        sslSequenceNumber new_right;
        sslSequenceNumber right;

        /* Slide to the right; this is the tricky part
         *
         * 1. new_top is set to have room for seq, on the
         *    next byte boundary by setting the right 8
         *    bits of seq
         * 2. new_left is set to compensate.
         * 3. Zero all bits between top and new_top. Since
         *    this is a ring, this zeroes everything as-yet
         *    unseen. Because we always operate on byte
         *    boundaries, we can zero one byte at a time
         */
        new_right = seq | 0x07;
        new_left = (new_right - DTLS_RECVD_RECORDS_WINDOW) + 1;

        if (new_right > records->right + DTLS_RECVD_RECORDS_WINDOW) {
            PORT_Memset(records->data, 0, sizeof(records->data));
        } else {
            for (right = records->right + 8; right <= new_right; right += 8) {
                offset = right % DTLS_RECVD_RECORDS_WINDOW;
                records->data[offset / 8] = 0;
            }
        }

        records->right = new_right;
        records->left = new_left;
    }

    offset = seq % DTLS_RECVD_RECORDS_WINDOW;

    records->data[offset / 8] |= (1 << (offset % 8));
}

SECStatus
DTLS_GetHandshakeTimeout(PRFileDesc *socket, PRIntervalTime *timeout)
{
    sslSocket *ss = NULL;
    PRIntervalTime elapsed;
    PRIntervalTime desired;

    ss = ssl_FindSocket(socket);

    if (!ss)
        return SECFailure;

    if (!IS_DTLS(ss))
        return SECFailure;

    if (!ss->ssl3.hs.rtTimerCb)
        return SECFailure;

    elapsed = PR_IntervalNow() - ss->ssl3.hs.rtTimerStarted;
    desired = PR_MillisecondsToInterval(ss->ssl3.hs.rtTimeoutMs);
    if (elapsed > desired) {
        /* Timer expired */
        *timeout = PR_INTERVAL_NO_WAIT;
    } else {
        *timeout = desired - elapsed;
    }

    return SECSuccess;
}

/*
 * DTLS relevance checks:
 * Note that this code currently ignores all out-of-epoch packets,
 * which means we lose some in the case of rehandshake +
 * loss/reordering. Since DTLS is explicitly unreliable, this
 * seems like a good tradeoff for implementation effort and is
 * consistent with the guidance of RFC 6347 Sections 4.1 and 4.2.4.1.
 *
 * If the packet is not relevant, this function returns PR_FALSE.
 * If the packet is relevant, this function returns PR_TRUE
 * and sets |*seqNum| to the packet sequence number.
 */
PRBool
dtls_IsRelevant(sslSocket *ss, const SSL3Ciphertext *cText,
                PRBool *sameEpoch, PRUint64 *seqNum)
{
    const ssl3CipherSpec *crSpec = ss->ssl3.crSpec;
    DTLSEpoch epoch;
    sslSequenceNumber dtls_seq_num;

    epoch = cText->seq_num >> 48;
    *sameEpoch = crSpec->epoch == epoch;
    if (!*sameEpoch) {
        SSL_DBG(("%d: SSL3[%d]: dtls_IsRelevant, received packet "
                 "from irrelevant epoch %d",
                 SSL_GETPID(), ss->fd, epoch));
        return PR_FALSE;
    }

    dtls_seq_num = cText->seq_num & RECORD_SEQ_MAX;
    if (dtls_RecordGetRecvd(&crSpec->recvdRecords, dtls_seq_num) != 0) {
        SSL_DBG(("%d: SSL3[%d]: dtls_IsRelevant, rejecting "
                 "potentially replayed packet",
                 SSL_GETPID(), ss->fd));
        return PR_FALSE;
    }

    *seqNum = dtls_seq_num;
    return PR_TRUE;
}

/* In TLS 1.3, a client that receives a retransmission of the server's first
 * flight will reject that message and discard it (see dtls_IsRelevant() above).
 * However, we need to trigger retransmission to prevent loss of the client's
 * last flight from causing the connection to fail.
 *
 * This only triggers for a retransmitted ServerHello.  Other (encrypted)
 * handshake messages do not trigger retransmission, so we are a little more
 * exposed to loss than is ideal.
 *
 * Note: This isn't an issue in earlier versions because the second-to-last
 * flight (sent by the server) includes the Finished message, which is not
 * dropped because it has the same epoch that the client currently expects.
 */
SECStatus
dtls_MaybeRetransmitHandshake(sslSocket *ss, const SSL3Ciphertext *cText,
                              PRBool sameEpoch)
{
    SECStatus rv = SECSuccess;
    DTLSEpoch messageEpoch = cText->seq_num >> 48;

    /* Drop messages from other epochs if we are ignoring things. */
    if (!sameEpoch && ss->ssl3.hs.zeroRttIgnore != ssl_0rtt_ignore_none) {
        return SECSuccess;
    }

    if (!ss->sec.isServer && ss->version >= SSL_LIBRARY_VERSION_TLS_1_3 &&
        messageEpoch == 0 && cText->type == content_handshake) {
        ssl_GetSSL3HandshakeLock(ss);
        if (ss->ssl3.hs.rtTimerCb == dtls_FinishedTimerCb &&
            ss->ssl3.hs.ws == idle_handshake) {
            rv = dtls_RetransmitDetected(ss);
        }
        ssl_ReleaseSSL3HandshakeLock(ss);
    }
    return rv;
}