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      1      1.1  christos # -*- mode: perl; -*-
      2  1.1.1.4  christos # Copyright 2016-2021 The OpenSSL Project Authors. All Rights Reserved.
      3      1.1  christos #
      4  1.1.1.4  christos # Licensed under the Apache License 2.0 (the "License").  You may not use
      5      1.1  christos # this file except in compliance with the License.  You can obtain a copy
      6      1.1  christos # in the file LICENSE in the source distribution or at
      7      1.1  christos # https://www.openssl.org/source/license.html
      8      1.1  christos 
      9      1.1  christos 
     10      1.1  christos ## Test version negotiation
     11      1.1  christos 
     12      1.1  christos package ssltests;
     13      1.1  christos 
     14      1.1  christos use strict;
     15      1.1  christos use warnings;
     16      1.1  christos 
     17      1.1  christos use List::Util qw/max min/;
     18      1.1  christos 
     19      1.1  christos use OpenSSL::Test;
     20  1.1.1.2  christos use OpenSSL::Test::Utils qw/anydisabled alldisabled disabled/;
     21      1.1  christos setup("no_test_here");
     22      1.1  christos 
     23  1.1.1.2  christos my @tls_protocols = ("SSLv3", "TLSv1", "TLSv1.1", "TLSv1.2", "TLSv1.3");
     24  1.1.1.4  christos my @tls_protocols_fips = ("TLSv1.2", "TLSv1.3");
     25      1.1  christos # undef stands for "no limit".
     26  1.1.1.2  christos my @min_tls_protocols = (undef, "SSLv3", "TLSv1", "TLSv1.1", "TLSv1.2", "TLSv1.3");
     27  1.1.1.4  christos my @min_tls_protocols_fips = (undef, "TLSv1.2", "TLSv1.3");
     28  1.1.1.2  christos my @max_tls_protocols = ("SSLv3", "TLSv1", "TLSv1.1", "TLSv1.2", "TLSv1.3", undef);
     29  1.1.1.4  christos my @max_tls_protocols_fips = ("TLSv1.2", "TLSv1.3", undef);
     30      1.1  christos 
     31  1.1.1.2  christos my @is_tls_disabled = anydisabled("ssl3", "tls1", "tls1_1", "tls1_2", "tls1_3");
     32  1.1.1.4  christos my @is_tls_disabled_fips = anydisabled("tls1_2", "tls1_3");
     33      1.1  christos 
     34      1.1  christos my $min_tls_enabled; my $max_tls_enabled;
     35  1.1.1.4  christos my $min_tls_enabled_fips; my $max_tls_enabled_fips;
     36      1.1  christos 
     37      1.1  christos # Protocol configuration works in cascades, i.e.,
     38      1.1  christos # $no_tls1_1 disables TLSv1.1 and below.
     39      1.1  christos #
     40      1.1  christos # $min_enabled and $max_enabled will be correct if there is at least one
     41      1.1  christos # protocol enabled.
     42  1.1.1.4  christos 
     43  1.1.1.4  christos sub min_prot_enabled {
     44  1.1.1.4  christos     my $protref = shift;
     45  1.1.1.4  christos     my $disabledref = shift;
     46  1.1.1.4  christos     my @protocols = @{$protref};
     47  1.1.1.4  christos     my @is_disabled = @{$disabledref};
     48  1.1.1.4  christos     my $min_enabled;
     49  1.1.1.4  christos 
     50  1.1.1.4  christos     foreach my $i (0..$#protocols) {
     51  1.1.1.4  christos         if (!$is_disabled[$i]) {
     52  1.1.1.4  christos             $min_enabled = $i;
     53  1.1.1.4  christos             last;
     54  1.1.1.4  christos         }
     55      1.1  christos     }
     56  1.1.1.4  christos     return $min_enabled;
     57      1.1  christos }
     58      1.1  christos 
     59  1.1.1.4  christos sub max_prot_enabled {
     60  1.1.1.4  christos     my $protref = shift;
     61  1.1.1.4  christos     my $disabledref = shift;
     62  1.1.1.4  christos     my @protocols = @{$protref};
     63  1.1.1.4  christos     my @is_disabled = @{$disabledref};
     64  1.1.1.4  christos     my $max_enabled;
     65  1.1.1.4  christos 
     66  1.1.1.4  christos     foreach my $i (0..$#protocols) {
     67  1.1.1.4  christos         if (!$is_disabled[$i]
     68  1.1.1.4  christos                 && ($protocols[$i] ne "TLSv1.3"
     69  1.1.1.4  christos                     || !disabled("ec")
     70  1.1.1.4  christos                     || !disabled("dh"))) {
     71  1.1.1.4  christos             $max_enabled = $i;
     72  1.1.1.4  christos         }
     73      1.1  christos     }
     74  1.1.1.4  christos     return $max_enabled;
     75      1.1  christos }
     76      1.1  christos 
     77  1.1.1.4  christos $min_tls_enabled = min_prot_enabled(\@tls_protocols, \@is_tls_disabled);
     78  1.1.1.4  christos $max_tls_enabled = max_prot_enabled(\@tls_protocols, \@is_tls_disabled);
     79  1.1.1.4  christos $min_tls_enabled_fips = min_prot_enabled(\@tls_protocols_fips, \@is_tls_disabled_fips);
     80  1.1.1.4  christos $max_tls_enabled_fips = max_prot_enabled(\@tls_protocols_fips, \@is_tls_disabled_fips);
     81  1.1.1.4  christos 
     82  1.1.1.4  christos 
     83      1.1  christos my @dtls_protocols = ("DTLSv1", "DTLSv1.2");
     84  1.1.1.4  christos my @dtls_protocols_fips = ("DTLSv1.2");
     85      1.1  christos # undef stands for "no limit".
     86      1.1  christos my @min_dtls_protocols = (undef, "DTLSv1", "DTLSv1.2");
     87  1.1.1.4  christos my @min_dtls_protocols_fips = (undef, "DTLSv1.2");
     88      1.1  christos my @max_dtls_protocols = ("DTLSv1", "DTLSv1.2", undef);
     89  1.1.1.4  christos my @max_dtls_protocols_fips = ("DTLSv1.2", undef);
     90      1.1  christos 
     91      1.1  christos my @is_dtls_disabled = anydisabled("dtls1", "dtls1_2");
     92  1.1.1.4  christos my @is_dtls_disabled_fips = anydisabled("dtls1_2");
     93      1.1  christos 
     94      1.1  christos my $min_dtls_enabled; my $max_dtls_enabled;
     95  1.1.1.4  christos my $min_dtls_enabled_fips; my $max_dtls_enabled_fips;
     96      1.1  christos 
     97      1.1  christos # $min_enabled and $max_enabled will be correct if there is at least one
     98      1.1  christos # protocol enabled.
     99  1.1.1.4  christos $min_dtls_enabled = min_prot_enabled(\@dtls_protocols, \@is_dtls_disabled);
    100  1.1.1.4  christos $max_dtls_enabled = max_prot_enabled(\@dtls_protocols, \@is_dtls_disabled);
    101  1.1.1.4  christos $min_dtls_enabled_fips = min_prot_enabled(\@dtls_protocols_fips, \@is_dtls_disabled_fips);
    102  1.1.1.4  christos $max_dtls_enabled_fips = max_prot_enabled(\@dtls_protocols_fips, \@is_dtls_disabled_fips);
    103      1.1  christos 
    104      1.1  christos sub no_tests {
    105  1.1.1.4  christos     my ($dtls, $fips) = @_;
    106  1.1.1.4  christos     if ($dtls && $fips) {
    107  1.1.1.4  christos         return disabled("dtls1_2");
    108  1.1.1.4  christos     }
    109      1.1  christos     return $dtls ? alldisabled("dtls1", "dtls1_2") :
    110  1.1.1.2  christos       alldisabled("ssl3", "tls1", "tls1_1", "tls1_2", "tls1_3");
    111      1.1  christos }
    112      1.1  christos 
    113      1.1  christos sub generate_version_tests {
    114  1.1.1.4  christos     my $method = shift;
    115  1.1.1.4  christos     my $fips = shift;
    116      1.1  christos 
    117      1.1  christos     my $dtls = $method eq "DTLS";
    118      1.1  christos     # Don't write the redundant "Method = TLS" into the configuration.
    119      1.1  christos     undef $method if !$dtls;
    120      1.1  christos 
    121  1.1.1.4  christos     my @protocols;
    122  1.1.1.4  christos     my @min_protocols;
    123  1.1.1.4  christos     my @max_protocols;
    124  1.1.1.4  christos     my $min_enabled;
    125  1.1.1.4  christos     my $max_enabled;
    126  1.1.1.4  christos     if ($fips) {
    127  1.1.1.4  christos         @protocols = $dtls ? @dtls_protocols_fips : @tls_protocols_fips;
    128  1.1.1.4  christos         @min_protocols = $dtls ? @min_dtls_protocols_fips : @min_tls_protocols_fips;
    129  1.1.1.4  christos         @max_protocols = $dtls ? @max_dtls_protocols_fips : @max_tls_protocols_fips;
    130  1.1.1.4  christos         $min_enabled  = $dtls ? $min_dtls_enabled_fips : $min_tls_enabled_fips;
    131  1.1.1.4  christos         $max_enabled  = $dtls ? $max_dtls_enabled_fips : $max_tls_enabled_fips;
    132  1.1.1.4  christos     } else {
    133  1.1.1.4  christos         @protocols = $dtls ? @dtls_protocols : @tls_protocols;
    134  1.1.1.4  christos         @min_protocols = $dtls ? @min_dtls_protocols : @min_tls_protocols;
    135  1.1.1.4  christos         @max_protocols = $dtls ? @max_dtls_protocols : @max_tls_protocols;
    136  1.1.1.4  christos         $min_enabled  = $dtls ? $min_dtls_enabled : $min_tls_enabled;
    137  1.1.1.4  christos         $max_enabled  = $dtls ? $max_dtls_enabled : $max_tls_enabled;
    138  1.1.1.4  christos     }
    139      1.1  christos 
    140  1.1.1.4  christos     if (no_tests($dtls, $fips)) {
    141      1.1  christos         return;
    142      1.1  christos     }
    143      1.1  christos 
    144      1.1  christos     my @tests = ();
    145      1.1  christos 
    146  1.1.1.2  christos     for (my $sctp = 0; $sctp < ($dtls && !disabled("sctp") ? 2 : 1); $sctp++) {
    147  1.1.1.2  christos         foreach my $c_min (0..$#min_protocols) {
    148  1.1.1.2  christos             my $c_max_min = $c_min == 0 ? 0 : $c_min - 1;
    149  1.1.1.2  christos             foreach my $c_max ($c_max_min..$#max_protocols) {
    150  1.1.1.2  christos                 foreach my $s_min (0..$#min_protocols) {
    151  1.1.1.2  christos                     my $s_max_min = $s_min == 0 ? 0 : $s_min - 1;
    152  1.1.1.2  christos                     foreach my $s_max ($s_max_min..$#max_protocols) {
    153  1.1.1.2  christos                         my ($result, $protocol) =
    154  1.1.1.2  christos                             expected_result($c_min, $c_max, $s_min, $s_max,
    155  1.1.1.2  christos                                             $min_enabled, $max_enabled,
    156  1.1.1.2  christos                                             \@protocols);
    157  1.1.1.2  christos                         push @tests, {
    158  1.1.1.2  christos                             "name" => "version-negotiation",
    159  1.1.1.2  christos                             "client" => {
    160  1.1.1.4  christos                                 "CipherString" => "DEFAULT:\@SECLEVEL=0",
    161  1.1.1.2  christos                                 "MinProtocol" => $min_protocols[$c_min],
    162  1.1.1.2  christos                                 "MaxProtocol" => $max_protocols[$c_max],
    163  1.1.1.2  christos                             },
    164  1.1.1.2  christos                             "server" => {
    165  1.1.1.4  christos                                 "CipherString" => "DEFAULT:\@SECLEVEL=0",
    166  1.1.1.2  christos                                 "MinProtocol" => $min_protocols[$s_min],
    167  1.1.1.2  christos                                 "MaxProtocol" => $max_protocols[$s_max],
    168  1.1.1.2  christos                             },
    169  1.1.1.2  christos                             "test" => {
    170  1.1.1.2  christos                                 "ExpectedResult" => $result,
    171  1.1.1.2  christos                                 "ExpectedProtocol" => $protocol,
    172  1.1.1.2  christos                                 "Method" => $method,
    173  1.1.1.2  christos                             }
    174  1.1.1.2  christos                         };
    175  1.1.1.2  christos                         $tests[-1]{"test"}{"UseSCTP"} = "Yes" if $sctp;
    176  1.1.1.2  christos                     }
    177      1.1  christos                 }
    178      1.1  christos             }
    179      1.1  christos         }
    180      1.1  christos     }
    181  1.1.1.4  christos     return @tests
    182  1.1.1.4  christos         if disabled("tls1_3")
    183  1.1.1.4  christos            || disabled("tls1_2")
    184  1.1.1.4  christos            || (disabled("ec") && disabled("dh"))
    185  1.1.1.4  christos            || $dtls;
    186  1.1.1.2  christos 
    187  1.1.1.2  christos     #Add some version/ciphersuite sanity check tests
    188  1.1.1.2  christos     push @tests, {
    189  1.1.1.2  christos         "name" => "ciphersuite-sanity-check-client",
    190  1.1.1.2  christos         "client" => {
    191  1.1.1.2  christos             #Offering only <=TLSv1.2 ciphersuites with TLSv1.3 should fail
    192  1.1.1.2  christos             "CipherString" => "AES128-SHA",
    193  1.1.1.2  christos             "Ciphersuites" => "",
    194  1.1.1.2  christos         },
    195  1.1.1.2  christos         "server" => {
    196  1.1.1.2  christos             "MaxProtocol" => "TLSv1.2"
    197  1.1.1.2  christos         },
    198  1.1.1.2  christos         "test" => {
    199  1.1.1.2  christos             "ExpectedResult" => "ClientFail",
    200  1.1.1.2  christos         }
    201  1.1.1.2  christos     };
    202  1.1.1.2  christos     push @tests, {
    203  1.1.1.2  christos         "name" => "ciphersuite-sanity-check-server",
    204  1.1.1.2  christos         "client" => {
    205  1.1.1.2  christos             "CipherString" => "AES128-SHA",
    206  1.1.1.2  christos             "MaxProtocol" => "TLSv1.2"
    207  1.1.1.2  christos         },
    208  1.1.1.2  christos         "server" => {
    209  1.1.1.2  christos             #Allowing only <=TLSv1.2 ciphersuites with TLSv1.3 should fail
    210  1.1.1.2  christos             "CipherString" => "AES128-SHA",
    211  1.1.1.2  christos             "Ciphersuites" => "",
    212  1.1.1.2  christos         },
    213  1.1.1.2  christos         "test" => {
    214  1.1.1.2  christos             "ExpectedResult" => "ServerFail",
    215  1.1.1.2  christos         }
    216  1.1.1.2  christos     };
    217  1.1.1.2  christos 
    218      1.1  christos     return @tests;
    219      1.1  christos }
    220      1.1  christos 
    221      1.1  christos sub generate_resumption_tests {
    222  1.1.1.4  christos     my $method = shift;
    223  1.1.1.4  christos     my $fips = shift;
    224      1.1  christos 
    225      1.1  christos     my $dtls = $method eq "DTLS";
    226      1.1  christos     # Don't write the redundant "Method = TLS" into the configuration.
    227      1.1  christos     undef $method if !$dtls;
    228      1.1  christos 
    229  1.1.1.4  christos     my @protocols;
    230  1.1.1.4  christos     my $min_enabled;
    231  1.1.1.4  christos     my $max_enabled;
    232  1.1.1.4  christos 
    233  1.1.1.4  christos     if ($fips) {
    234  1.1.1.4  christos         @protocols = $dtls ? @dtls_protocols_fips : @tls_protocols_fips;
    235  1.1.1.4  christos         $min_enabled  = $dtls ? $min_dtls_enabled_fips : $min_tls_enabled_fips;
    236  1.1.1.4  christos         $max_enabled = $dtls ? $max_dtls_enabled_fips : $max_tls_enabled_fips;
    237  1.1.1.4  christos     } else {
    238  1.1.1.4  christos         @protocols = $dtls ? @dtls_protocols : @tls_protocols;
    239  1.1.1.4  christos         $min_enabled  = $dtls ? $min_dtls_enabled : $min_tls_enabled;
    240  1.1.1.4  christos         $max_enabled = $dtls ? $max_dtls_enabled : $max_tls_enabled;
    241  1.1.1.4  christos     }
    242      1.1  christos 
    243      1.1  christos     if (no_tests($dtls)) {
    244      1.1  christos         return;
    245      1.1  christos     }
    246      1.1  christos 
    247      1.1  christos     my @server_tests = ();
    248      1.1  christos     my @client_tests = ();
    249      1.1  christos 
    250      1.1  christos     # Obtain the first session against a fixed-version server/client.
    251  1.1.1.2  christos     foreach my $original_protocol($min_enabled..$max_enabled) {
    252      1.1  christos         # Upgrade or downgrade the server/client max version support and test
    253      1.1  christos         # that it upgrades, downgrades or resumes the session as well.
    254  1.1.1.2  christos         foreach my $resume_protocol($min_enabled..$max_enabled) {
    255      1.1  christos             my $resumption_expected;
    256      1.1  christos             # We should only resume on exact version match.
    257      1.1  christos             if ($original_protocol eq $resume_protocol) {
    258      1.1  christos                 $resumption_expected = "Yes";
    259      1.1  christos             } else {
    260      1.1  christos                 $resumption_expected = "No";
    261      1.1  christos             }
    262      1.1  christos 
    263  1.1.1.2  christos             for (my $sctp = 0; $sctp < ($dtls && !disabled("sctp") ? 2 : 1);
    264  1.1.1.2  christos                  $sctp++) {
    265  1.1.1.2  christos                 foreach my $ticket ("SessionTicket", "-SessionTicket") {
    266  1.1.1.2  christos                     # Client is flexible, server upgrades/downgrades.
    267  1.1.1.2  christos                     push @server_tests, {
    268  1.1.1.2  christos                         "name" => "resumption",
    269  1.1.1.4  christos                         "client" => {
    270  1.1.1.4  christos                             "CipherString" => "DEFAULT:\@SECLEVEL=0",
    271  1.1.1.4  christos                         },
    272  1.1.1.2  christos                         "server" => {
    273  1.1.1.4  christos                             "CipherString" => "DEFAULT:\@SECLEVEL=0",
    274  1.1.1.2  christos                             "MinProtocol" => $protocols[$original_protocol],
    275  1.1.1.2  christos                             "MaxProtocol" => $protocols[$original_protocol],
    276  1.1.1.2  christos                             "Options" => $ticket,
    277  1.1.1.2  christos                         },
    278  1.1.1.2  christos                         "resume_server" => {
    279  1.1.1.4  christos                             "CipherString" => "DEFAULT:\@SECLEVEL=0",
    280  1.1.1.2  christos                             "MaxProtocol" => $protocols[$resume_protocol],
    281  1.1.1.2  christos                             "Options" => $ticket,
    282  1.1.1.2  christos                         },
    283  1.1.1.2  christos                         "test" => {
    284  1.1.1.2  christos                             "ExpectedProtocol" => $protocols[$resume_protocol],
    285  1.1.1.2  christos                             "Method" => $method,
    286  1.1.1.2  christos                             "HandshakeMode" => "Resume",
    287  1.1.1.2  christos                             "ResumptionExpected" => $resumption_expected,
    288  1.1.1.2  christos                         }
    289  1.1.1.2  christos                     };
    290  1.1.1.2  christos                     $server_tests[-1]{"test"}{"UseSCTP"} = "Yes" if $sctp;
    291  1.1.1.2  christos                     # Server is flexible, client upgrades/downgrades.
    292  1.1.1.2  christos                     push @client_tests, {
    293  1.1.1.2  christos                         "name" => "resumption",
    294  1.1.1.2  christos                         "client" => {
    295  1.1.1.4  christos                             "CipherString" => "DEFAULT:\@SECLEVEL=0",
    296  1.1.1.2  christos                             "MinProtocol" => $protocols[$original_protocol],
    297  1.1.1.2  christos                             "MaxProtocol" => $protocols[$original_protocol],
    298  1.1.1.2  christos                         },
    299  1.1.1.2  christos                         "server" => {
    300  1.1.1.4  christos                             "CipherString" => "DEFAULT:\@SECLEVEL=0",
    301  1.1.1.2  christos                             "Options" => $ticket,
    302  1.1.1.2  christos                         },
    303  1.1.1.2  christos                         "resume_client" => {
    304  1.1.1.4  christos                             "CipherString" => "DEFAULT:\@SECLEVEL=0",
    305  1.1.1.2  christos                             "MaxProtocol" => $protocols[$resume_protocol],
    306  1.1.1.2  christos                         },
    307  1.1.1.2  christos                         "test" => {
    308  1.1.1.2  christos                             "ExpectedProtocol" => $protocols[$resume_protocol],
    309  1.1.1.2  christos                             "Method" => $method,
    310  1.1.1.2  christos                             "HandshakeMode" => "Resume",
    311  1.1.1.2  christos                             "ResumptionExpected" => $resumption_expected,
    312  1.1.1.2  christos                         }
    313  1.1.1.2  christos                     };
    314  1.1.1.2  christos                     $client_tests[-1]{"test"}{"UseSCTP"} = "Yes" if $sctp;
    315  1.1.1.2  christos                 }
    316      1.1  christos             }
    317      1.1  christos         }
    318      1.1  christos     }
    319      1.1  christos 
    320  1.1.1.4  christos     if (!disabled("tls1_3") && (!disabled("ec") || !disabled("dh")) && !$dtls) {
    321  1.1.1.2  christos         push @client_tests, {
    322  1.1.1.2  christos             "name" => "resumption-with-hrr",
    323  1.1.1.2  christos             "client" => {
    324  1.1.1.2  christos             },
    325  1.1.1.2  christos             "server" => {
    326  1.1.1.4  christos                 "Curves" => disabled("ec") ? "ffdhe3072" : "P-256"
    327  1.1.1.2  christos             },
    328  1.1.1.2  christos             "resume_client" => {
    329  1.1.1.2  christos             },
    330  1.1.1.2  christos             "test" => {
    331  1.1.1.2  christos                 "ExpectedProtocol" => "TLSv1.3",
    332  1.1.1.2  christos                 "Method" => "TLS",
    333  1.1.1.2  christos                 "HandshakeMode" => "Resume",
    334  1.1.1.2  christos                 "ResumptionExpected" => "Yes",
    335  1.1.1.2  christos             }
    336  1.1.1.2  christos         };
    337  1.1.1.2  christos     }
    338  1.1.1.2  christos 
    339      1.1  christos     return (@server_tests, @client_tests);
    340      1.1  christos }
    341      1.1  christos 
    342      1.1  christos sub expected_result {
    343      1.1  christos     my ($c_min, $c_max, $s_min, $s_max, $min_enabled, $max_enabled,
    344      1.1  christos         $protocols) = @_;
    345  1.1.1.4  christos     my @prots = @$protocols;
    346      1.1  christos 
    347  1.1.1.4  christos     my $orig_c_max = $c_max;
    348      1.1  christos     # Adjust for "undef" (no limit).
    349      1.1  christos     $c_min = $c_min == 0 ? 0 : $c_min - 1;
    350      1.1  christos     $c_max = $c_max == scalar @$protocols ? $c_max - 1 : $c_max;
    351      1.1  christos     $s_min = $s_min == 0 ? 0 : $s_min - 1;
    352      1.1  christos     $s_max = $s_max == scalar @$protocols ? $s_max - 1 : $s_max;
    353      1.1  christos 
    354      1.1  christos     # We now have at least one protocol enabled, so $min_enabled and
    355      1.1  christos     # $max_enabled are well-defined.
    356      1.1  christos     $c_min = max $c_min, $min_enabled;
    357      1.1  christos     $s_min = max $s_min, $min_enabled;
    358      1.1  christos     $c_max = min $c_max, $max_enabled;
    359      1.1  christos     $s_max = min $s_max, $max_enabled;
    360      1.1  christos 
    361  1.1.1.4  christos     if ($c_min > $c_max
    362  1.1.1.4  christos             || ($orig_c_max != scalar @$protocols
    363  1.1.1.4  christos                 && $prots[$orig_c_max] eq "TLSv1.3"
    364  1.1.1.4  christos                 && $c_max != $orig_c_max
    365  1.1.1.4  christos                 && !disabled("tls1_3"))) {
    366      1.1  christos         # Client should fail to even send a hello.
    367  1.1.1.2  christos         return ("ClientFail", undef);
    368      1.1  christos     } elsif ($s_min > $s_max) {
    369      1.1  christos         # Server has no protocols, should always fail.
    370      1.1  christos         return ("ServerFail", undef);
    371      1.1  christos     } elsif ($s_min > $c_max) {
    372      1.1  christos         # Server doesn't support the client range.
    373      1.1  christos         return ("ServerFail", undef);
    374      1.1  christos     } elsif ($c_min > $s_max) {
    375  1.1.1.2  christos         if ($prots[$c_max] eq "TLSv1.3") {
    376  1.1.1.2  christos             # Client will have sent supported_versions, so server will know
    377  1.1.1.2  christos             # that there are no overlapping versions.
    378  1.1.1.2  christos             return ("ServerFail", undef);
    379  1.1.1.2  christos         } else {
    380  1.1.1.2  christos             # Server will try with a version that is lower than the lowest
    381  1.1.1.2  christos             # supported client version.
    382  1.1.1.2  christos             return ("ClientFail", undef);
    383  1.1.1.2  christos         }
    384      1.1  christos     } else {
    385      1.1  christos         # Server and client ranges overlap.
    386      1.1  christos         my $max_common = $s_max < $c_max ? $s_max : $c_max;
    387      1.1  christos         return ("Success", $protocols->[$max_common]);
    388      1.1  christos     }
    389      1.1  christos }
    390      1.1  christos 
    391      1.1  christos 1;
    392