From 1aeca5f89e768df83d3f6f86e0d782e5a20fc1f6 Mon Sep 17 00:00:00 2001
From: Guilhem Moulin <guilhem@fripost.org>
Date: Mon, 19 Oct 2015 17:14:43 +0200
Subject: Add an option 'SSL_protocols'.

---
 lib/Net/IMAP/InterIMAP.pm | 37 +++++++++++++++++++++++++++++++------
 1 file changed, 31 insertions(+), 6 deletions(-)

(limited to 'lib')

diff --git a/lib/Net/IMAP/InterIMAP.pm b/lib/Net/IMAP/InterIMAP.pm
index 8b1f451..95bdfa8 100644
--- a/lib/Net/IMAP/InterIMAP.pm
+++ b/lib/Net/IMAP/InterIMAP.pm
@@ -43,6 +43,8 @@ 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 $RE_SSL_PROTO = qr/(?:SSLv[23]|TLSv1|TLSv1\.[0-2])/;
+
 # Map each option to a regexp validating its values.
 my %OPTIONS = (
     host => qr/\A(\P{Control}+)\z/,
@@ -56,6 +58,7 @@ my %OPTIONS = (
     command => qr/\A(\P{Control}+)\z/,
     'null-stderr' => qr/\A(YES|NO)\z/i,
     compress => qr/\A($RE_ATOM_CHAR+(?: $RE_ATOM_CHAR+)*)\z/,
+    SSL_protocols => qr/\A(!?$RE_SSL_PROTO(?: !?$RE_SSL_PROTO)*)\z/,
     SSL_fingerprint => qr/\A((?:[A-Za-z0-9]+\$)?\p{AHex}+)\z/,
     SSL_cipherlist => qr/\A(\P{Control}+)\z/,
     SSL_verify => qr/\A(YES|NO)\z/i,
@@ -1460,20 +1463,42 @@ 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()
+);
 
 # $self->_start_ssl($socket)
 #   Upgrade the $socket to SSL/TLS.
 sub _start_ssl($$) {
     my ($self, $socket) = @_;
     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();
+
+    $self->{SSL_protocols} //= q{!SSLv2 !SSLv3};
+    my ($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 protocol: ".join(', ', sort @proto_exclude)) if $self->{debug};
+    $ssl_options |= $SSL_proto{$_} foreach @proto_exclude;
+    $ssl_options |= Net::SSLeay::OP_NO_COMPRESSION();
 
     # https://www.openssl.org/docs/manmaster/ssl/SSL_CTX_set_options.html
-    Net::SSLeay::CTX_set_options($ctx,
-        Net::SSLeay::OP_SINGLE_ECDH_USE() |
-        Net::SSLeay::OP_SINGLE_DH_USE() |
-        Net::SSLeay::OP_NO_SSLv2() |
-        Net::SSLeay::OP_NO_SSLv3() |
-        Net::SSLeay::OP_NO_COMPRESSION() );
+    Net::SSLeay::CTX_set_options($ctx, $ssl_options);
 
     # https://www.openssl.org/docs/manmaster/ssl/SSL_CTX_set_mode.html
     Net::SSLeay::CTX_set_mode($ctx,
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