--- filter_nnrpd.pl.orig	2021-02-09 07:47:09.000000000 +0100
+++ filter_nnrpd.pl	2021-02-09 07:59:46.000000000 +0100
@@ -1,10 +1,7 @@
 #
 # Do any initialization steps.
 #
-use Digest::MD5  qw(md5_base64);
-use Digest::SHA1();
-use Digest::HMAC_SHA1();
-use MIME::Base64();
+use Digest::SHA qw( sha256_base64 hmac_sha256_base64 );
 
 $CANCEL_LOCK = 'secretword';
 
@@ -36,18 +33,26 @@
 sub add_cancel_item($$$) {
    my ( $r_hdr, $name, $value ) = @_;
    my $prefix = $r_hdr->{$name};
-   $prefix = defined($prefix) ? $prefix . ' sha1:' : 'sha1:';
+   $prefix = defined($prefix) ? $prefix . ' sha256:' : 'sha256:';
    $r_hdr->{$name} = $prefix . $value;
 }
 
 sub calc_cancel_key($$) {
    my ( $user, $message_id ) = @_;
-   return MIME::Base64::encode(Digest::HMAC_SHA1::hmac_sha1($message_id, $user . $CANCEL_LOCK), '');
+   return pad_b64digest(hmac_sha256_base64($message_id, $user . $CANCEL_LOCK));
 }
 
 sub add_cancel_lock($$) {
    my ( $r_hdr, $user ) = @_;
    my $key = calc_cancel_key($user, $r_hdr->{'Message-ID'});
-   my $lock = MIME::Base64::encode(Digest::SHA1::sha1($key), '');
+   my $lock = pad_b64digest(sha256_base64($key));
    add_cancel_item($r_hdr, 'Cancel-Lock', $lock);
 }
+
+sub pad_b64digest($) {
+    my ($b64_digest) = @_;
+    while (length($b64_digest) % 4) {
+        $b64_digest .= '=';
+    }
+    return $b64_digest;
+}