vcard: Fix whitespace handling in line cont's (#9637)

* vcard: Fix whitespace handling in line cont's

Previously, multiple whitespace characters at the start of a
continuation line would all be dropped, instead of only the first one.

Also,
 - restrict line continuation characters to SPACE and TAB.

Note that, like before, this identifies the CR (`\r`) character with the
empty string, and thereby notably does not require a CRLF (`\r\n`)
sequence (which is mandated by RFCs 2426, 2425) for line termination
(i.e., `\n` suffices).

Fixes: Bug 1 of issue #9593.

* vcard: Add test for #9593/1

* Fix coding style

program/lib/Roundcube/rcube_vcard.php

@@ -699,8 +699,8 @@ public static function rfc2425_fold($val)
     private static function vcard_decode($vcard)
     {
         // Perform RFC2425 line unfolding and split lines
-        $vcard  = preg_replace(["/\r/", "/\n\s+/"], '', $vcard);
-        $lines  = explode("\n", $vcard);
+        $vcard = str_replace(["\r", "\n ", "\n\t"], '', $vcard);
+        $lines = explode("\n", $vcard);
         $result = [];
 
         for ($i=0; $i < count($lines); $i++) {
@@ -1013,8 +1013,8 @@ private static function detect_encoding($string)
         // This will for example exclude photos
 
         // Perform RFC2425 line unfolding and split lines
-        $string = preg_replace(["/\r/", "/\n\s+/"], '', $string);
-        $lines  = explode("\n", $string);
+        $string = str_replace(["\r", "\n ", "\n\t"], '', $string);
+        $lines = explode("\n", $string);
         $string = '';
 
         for ($i = 0, $len = count($lines); $i < $len; $i++) {

tests/Framework/VCard.php

@@ -98,6 +98,28 @@ function test_parse_six()
         $this->assertCount(1, $result['address:work'], "ITEM1.-prefixed entry");
     }
 
+    /**
+     * Extra whitespace at start of continuation line (#9593/1).
+     */
+    public function test_parse_continuation_line_with_initial_whitespace()
+    {
+        $vcard_string = <<<'EOF'
+            BEGIN:VCARD
+            VERSION:3.0
+            N:Doe;Jane;;;
+            FN:Jane Doe
+            NOTE:an
+              example
+            END:VCARD
+            EOF;
+
+        $vcard = new \rcube_vcard(str_replace("\n", "\r\n", $vcard_string) . "\r\n");
+
+        $result = $vcard->get_assoc();
+
+        $this->assertSame('an example', $result['notes'][0]);
+    }
+
     function test_import()
     {
         $input = file_get_contents($this->_srcpath('apple.vcf'));