libinterimap: remove default SSL_protocols value.

Namely, use the system default instead of "!SSLv2 !SSLv3 !TLSv1 !TLSv1.1".

As of Debian Buster (OpenSSL 1.1.1) this does not make a difference,
however using the system default provides better compatibility with
future libssl versions.

1 files changed, 20 insertions, 18 deletions

diff --git a/lib/Net/IMAP/InterIMAP.pm b/lib/Net/IMAP/InterIMAP.pm
index 8b59ed2..221b016 100644
--- a/lib/Net/IMAP/InterIMAP.pm
+++ b/lib/Net/IMAP/InterIMAP.pm
@@ -1694,32 +1694,34 @@ sub _start_ssl($$) {
     my ($self, $socket) = @_;
     my $openssl_version = Net::SSLeay::OPENSSL_VERSION_NUMBER();
     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();
 
     if (defined $self->{_OUTBUF} and $self->{_OUTBUF} ne '') {
         $self->warn("Truncating non-empty output buffer (unauthenticated response injection?)");
         undef $self->{_OUTBUF};
     }
 
-    $self->{SSL_protocols} //= q{!SSLv2 !SSLv3 !TLSv1 !TLSv1.1};
-    my ($proto_include, $proto_exclude) = (0, 0);
-    foreach (split /\s+/, $self->{SSL_protocols}) {
-        my $neg = s/^!// ? 1 : 0;
-        s/\.0$//;
-        ($neg ? $proto_exclude : $proto_include) |= $SSL_proto{$_} // $self->panic("Unknown SSL protocol: $_");
-    }
-    if ($proto_include != 0) {
-        # exclude all protocols except those explictly included
-        my $x = 0;
-        $x |= $_ foreach values %SSL_proto;
-        $x &= ~ $proto_include;
-        $proto_exclude |= $x;
-    }
-    my @proto_exclude = grep { ($proto_exclude & $SSL_proto{$_}) != 0 } keys %SSL_proto;
-    $self->log("Disabling SSL protocols: ".join(', ', sort @proto_exclude)) if $self->{debug};
-    $ssl_options |= $SSL_proto{$_} foreach @proto_exclude;
+    my $ssl_options = Net::SSLeay::OP_SINGLE_DH_USE() | Net::SSLeay::OP_SINGLE_ECDH_USE();
     $ssl_options |= Net::SSLeay::OP_NO_COMPRESSION();
 
+    if (defined (my $protos = $self->{SSL_protocols})) {
+        my ($proto_include, $proto_exclude) = (0, 0);
+        foreach (split /\s+/, $protos) {
+            my $neg = s/^!// ? 1 : 0;
+            s/\.0$//;
+            ($neg ? $proto_exclude : $proto_include) |= $SSL_proto{$_} // $self->panic("Unknown SSL protocol: $_");
+        }
+        if ($proto_include != 0) {
+            # exclude all protocols except those explictly included
+            my $x = 0;
+            $x |= $_ foreach values %SSL_proto;
+            $x &= ~ $proto_include;
+            $proto_exclude |= $x;
+        }
+        my @proto_exclude = grep { ($proto_exclude & $SSL_proto{$_}) != 0 } keys %SSL_proto;
+        $self->log("Disabling SSL protocols: ".join(', ', sort @proto_exclude)) if $self->{debug};
+        $ssl_options |= $SSL_proto{$_} foreach @proto_exclude;
+    }
+
     # https://www.openssl.org/docs/manmaster/ssl/SSL_CTX_set_options.html
     Net::SSLeay::CTX_set_options($ctx, $ssl_options);