Update normalise and example for clearsigning

Trailing whitespace must be removed when generating the signature and
must not be included in output.

examples/clearsign.php

@@ -7,8 +7,11 @@ require_once dirname(__FILE__).'/../lib/openpgp_crypt_rsa.php';
 $wkey = OpenPGP_Message::parse(file_get_contents('php://stdin'));
 $wkey = $wkey[0];
 
+$string = "This\nis\na\ntest.";
+
 /* Create a new literal data packet */
-$data = new OpenPGP_LiteralDataPacket('This is text.', array('format' => 'u', 'filename' => 'stuff.txt'));
+$data = new OpenPGP_LiteralDataPacket($string, array('format' => 'u', 'filename' => 'stuff.txt'));
+$data->normalize(true); // Clearsign-style normalization of the LiteralDataPacket
 
 /* Create a signer from the key */
 $sign = new OpenPGP_Crypt_RSA($wkey);
@@ -19,6 +22,9 @@ $m = $sign->sign($data);
 /* Generate clearsigned data */
 $packets = $m->signatures()[0];
 echo "-----BEGIN PGP SIGNED MESSAGE-----\nHash: SHA256\n\n";
+// Output normalised data.  You could convert line endings here
+// without breaking the signature, but do not add any
+// trailing whitespace to lines.
 echo preg_replace("/^-/", "- -",  $packets[0]->data)."\n";
 echo OpenPGP::enarmor($packets[1][0]->to_bytes(), "PGP SIGNATURE");
 

lib/openpgp.php

@@ -1702,10 +1702,19 @@ class OpenPGP_LiteralDataPacket extends OpenPGP_Packet {
     $this->timestamp = isset($opt['timestamp']) ? $opt['timestamp'] : time();
   }
 
-  function normalize() {
+  function normalize($clearsign=false) {
+    if($clearsign && ($this->format != 'u' && $this->format != 't')) {
+      $this->format = 'u'; // Clearsign must be text
+    }
+
     if($this->format == 'u' || $this->format == 't') { // Normalize line endings
       $this->data = str_replace("\n", "\r\n", str_replace("\r", "\n", str_replace("\r\n", "\n", $this->data)));
     }
+
+    if($clearsign) {
+      // When clearsigning, do not sign over trailing whitespace
+      $this->data = preg_replace('/\s+\r/', "\r", $this->data);
+    }
   }
 
   function read() {