Net::IMAP::InterIMAP: add support for TLSv1.3 (on recent enough Net::SSLeay).

Also, change "SSL_protocols" default value from "!SSLv2 !SSLv3" to
"!SSLv2 !SSLv3 !TLSv1 !TLSv1.1".  I.e., only enable TLSv1.2 and later,
which is the default in Debian's OpenSSL as of 1.1.1-2, cf.
https://tracker.debian.org/news/998835/accepted-openssl-111-2-source-into-unstable/ .

4 files changed, 28 insertions, 16 deletions

diff --git a/Changelog b/Changelog
index b4fb931..9fa46dd 100644
--- a/Changelog
+++ b/Changelog
@@ -7,6 +7,9 @@ interimap (0.4) UNRELEASED
     relative to $XDG_CONFIG_HOME/$NAME (or ~/.config/$NAME), to comply
     with the XDG specification.  Thus the previous default config file
     $XDG_CONFIG_HOME/$NAME should become $XDG_CONFIG_HOME/$NAME/config.
+  * Library: add support for TLSv1.3 (on recent enough Net::SSLeay), and
+    change "SSL_protocols" default value from "!SSLv2 !SSLv3" to "!SSLv2
+    !SSLv3 !TLSv1 !TLSv1.1".
   + Library: new API idle_start() and idle_stop().
   + Add support for untagged ESEARCH responses from RFC 4731.
   + pullimap: Use extended SEARCH commands (RFC 4731) if supported by
diff --git a/interimap.md b/interimap.md
index 1831d39..4d85eaf 100644
--- a/interimap.md
+++ b/interimap.md
@@ -332,9 +332,10 @@ Valid options are:
 
 :   A space-separated list of SSL protocols to enable or disable (if
     prefixed with an exclamation mark `!`.  Known protocols are `SSLv2`,
-    `SSLv3`, `TLSv1`, `TLSv1.1`, and `TLSv1.2`.  Enabling a protocol is
-    a short-hand for disabling all other protocols.
-    (Default: `!SSLv2 !SSLv3`, i.e., only enable TLSv1 and above.)
+    `SSLv3`, `TLSv1`, `TLSv1.1`, `TLSv1.2`, and `TLSv1.3`.  Enabling a
+    protocol is a short-hand for disabling all other protocols.
+    (Default: `!SSLv2 !SSLv3 !TLSv1 !TLSv1.1`, i.e., only enable TLSv1.2
+    and above.)
 
 *SSL_cipher_list*
 
diff --git a/lib/Net/IMAP/InterIMAP.pm b/lib/Net/IMAP/InterIMAP.pm
index f783ea7..3d8bd97 100644
--- a/lib/Net/IMAP/InterIMAP.pm
+++ b/lib/Net/IMAP/InterIMAP.pm
@@ -45,7 +45,7 @@ my $RE_ATOM_CHAR    = qr/[\x21\x23\x24\x26\x27\x2B-\x5B\x5E-\x7A\x7C-\x7E]/;
 my $RE_ASTRING_CHAR = qr/[\x21\x23\x24\x26\x27\x2B-\x5B\x5D-\x7A\x7C-\x7E]/;
 my $RE_TEXT_CHAR    = qr/[\x01-\x09\x0B\x0C\x0E-\x7F]/;
 
-my $RE_SSL_PROTO = qr/(?:SSLv[23]|TLSv1|TLSv1\.[0-2])/;
+my $RE_SSL_PROTO = qr/(?:SSLv[23]|TLSv1|TLSv1\.[0-3])/;
 
 # Map each option to a regexp validating its values.
 my %OPTIONS = (
@@ -1599,13 +1599,19 @@ sub _ssl_verify($$$) {
     return $ok; # 1=accept cert, 0=reject
 }
 
-my %SSL_proto = (
-    'SSLv2' => Net::SSLeay::OP_NO_SSLv2(),
-    'SSLv3' => Net::SSLeay::OP_NO_SSLv3(),
-    'TLSv1' => Net::SSLeay::OP_NO_TLSv1(),
-    'TLSv1.1' => Net::SSLeay::OP_NO_TLSv1_1(),
-    'TLSv1.2' => Net::SSLeay::OP_NO_TLSv1_2()
-);
+my %SSL_proto;
+BEGIN {
+    sub _append_ssl_proto($$) {
+        my ($k, $v) = @_;
+        $SSL_proto{$k} = $v if defined $v;
+    }
+    _append_ssl_proto( "SSLv2",   eval { Net::SSLeay::OP_NO_SSLv2()   } );
+    _append_ssl_proto( "SSLv3",   eval { Net::SSLeay::OP_NO_SSLv3()   } );
+    _append_ssl_proto( "TLSv1",   eval { Net::SSLeay::OP_NO_TLSv1()   } );
+    _append_ssl_proto( "TLSv1.1", eval { Net::SSLeay::OP_NO_TLSv1_1() } );
+    _append_ssl_proto( "TLSv1.2", eval { Net::SSLeay::OP_NO_TLSv1_2() } );
+    _append_ssl_proto( "TLSv1.3", eval { Net::SSLeay::OP_NO_TLSv1_3() } );
+}
 
 # $self->_start_ssl($socket)
 #   Upgrade the $socket to SSL/TLS.
@@ -1614,7 +1620,7 @@ sub _start_ssl($$) {
     my $ctx = Net::SSLeay::CTX_new() or $self->panic("Failed to create SSL_CTX $!");
     my $ssl_options = Net::SSLeay::OP_SINGLE_DH_USE() | Net::SSLeay::OP_SINGLE_ECDH_USE();
 
-    $self->{SSL_protocols} //= q{!SSLv2 !SSLv3};
+    $self->{SSL_protocols} //= q{!SSLv2 !SSLv3 !TLSv1 !TLSv1.1};
     my ($proto_include, $proto_exclude) = (0, 0);
     foreach (split /\s+/, $self->{SSL_protocols}) {
         my $neg = s/^!// ? 1 : 0;
@@ -1629,7 +1635,7 @@ sub _start_ssl($$) {
         $proto_exclude |= $x;
     }
     my @proto_exclude = grep { ($proto_exclude & $SSL_proto{$_}) != 0 } keys %SSL_proto;
-    $self->log("Disabling SSL protocol: ".join(', ', sort @proto_exclude)) if $self->{debug};
+    $self->log("Disabling SSL protocols: ".join(', ', sort @proto_exclude)) if $self->{debug};
     $ssl_options |= $SSL_proto{$_} foreach @proto_exclude;
     $ssl_options |= Net::SSLeay::OP_NO_COMPRESSION();
 
@@ -1675,6 +1681,7 @@ sub _start_ssl($$) {
                                                        $v == 0x0301 ? 'TLSv1' :
                                                        $v == 0x0302 ? 'TLSv1.1' :
                                                        $v == 0x0303 ? 'TLSv1.2' :
+                                                       $v == 0x0304 ? 'TLSv1.3' :
                                                                       '??'),
                                                       $v));
         $self->log(sprintf('SSL cipher: %s (%d bits)'
diff --git a/pullimap.md b/pullimap.md
index eac8efa..a367dd1 100644
--- a/pullimap.md
+++ b/pullimap.md
@@ -198,9 +198,10 @@ Valid options are:
 
 :   A space-separated list of SSL protocols to enable or disable (if
     prefixed with an exclamation mark `!`.  Known protocols are `SSLv2`,
-    `SSLv3`, `TLSv1`, `TLSv1.1`, and `TLSv1.2`.  Enabling a protocol is
-    a short-hand for disabling all other protocols.
-    (Default: `!SSLv2 !SSLv3`, i.e., only enable TLSv1 and above.)
+    `SSLv3`, `TLSv1`, `TLSv1.1`, `TLSv1.2`, and `TLSv1.3`.  Enabling a
+    protocol is a short-hand for disabling all other protocols.
+    (Default: `!SSLv2 !SSLv3 !TLSv1 !TLSv1.1`, i.e., only enable TLSv1.2
+    and above.)
 
 *SSL_cipher_list*