8255405: sun/net/ftp/imp/FtpClient uses SimpleDateFormat in not thread-safe manner

Reviewed-by: chegar, ryadav, dfuchs

Author: iignatev

src/java.base/share/classes/sun/net/ftp/impl/FtpClient.java

@@ -29,15 +29,16 @@
 import java.security.AccessController;
 import java.security.PrivilegedAction;
 import java.text.DateFormat;
-import java.text.ParseException;
-import java.text.SimpleDateFormat;
+import java.time.ZoneOffset;
+import java.time.ZonedDateTime;
+import java.time.format.DateTimeFormatter;
+import java.time.format.DateTimeParseException;
 import java.util.ArrayList;
 import java.util.Base64;
 import java.util.Calendar;
 import java.util.Date;
 import java.util.Iterator;
 import java.util.List;
-import java.util.TimeZone;
 import java.util.Vector;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -1739,19 +1740,8 @@ public long getSize(String path) throws sun.net.ftp.FtpProtocolException, IOExce
         return -1;
     }
 
-    private static final SimpleDateFormat[] dateFormats;
-
-    static {
-        String[] formats = {
-            "yyyyMMddHHmmss.SSS",
-            "yyyyMMddHHmmss"
-        };
-        dateFormats = new SimpleDateFormat[formats.length];
-        for (int i = 0; i < formats.length; ++i) {
-            dateFormats[i] = new SimpleDateFormat(formats[i]);
-            dateFormats[i].setTimeZone(TimeZone.getTimeZone("GMT"));
-        }
-    }
+    private static final DateTimeFormatter RFC3659_DATETIME_FORMAT = DateTimeFormatter.ofPattern("yyyyMMddHHmmss[.SSS]")
+                                                                                      .withZone(ZoneOffset.UTC);
 
     /**
      * Issues the MDTM [path] command to the server to get the modification
@@ -1768,24 +1758,20 @@ public long getSize(String path) throws sun.net.ftp.FtpProtocolException, IOExce
     public Date getLastModified(String path) throws sun.net.ftp.FtpProtocolException, IOException {
         issueCommandCheck("MDTM " + path);
         if (lastReplyCode == FtpReplyCode.FILE_STATUS) {
-            String s = getResponseString().substring(4);
-            return parseRfc3659TimeValue(s);
+            String s = getResponseString();
+            return parseRfc3659TimeValue(s.substring(4, s.length() - 1));
         }
         return null;
     }
 
     private static Date parseRfc3659TimeValue(String s) {
-        Date d = null;
-        for (SimpleDateFormat dateFormat : dateFormats) {
-            try {
-                d = dateFormat.parse(s);
-            } catch (ParseException ex) {
-            }
-            if (d != null) {
-                return d;
-            }
+        Date result = null;
+        try {
+            var d = ZonedDateTime.parse(s, RFC3659_DATETIME_FORMAT);
+            result = Date.from(d.toInstant());
+        } catch (DateTimeParseException ex) {
         }
-        return d;
+        return result;
     }
 
     /**

test/jdk/sun/net/ftp/TestFtpTimeValue.java

@@ -28,7 +28,8 @@
  * @library /test/lib
  * @modules java.base/sun.net.ftp
  * @build jdk.test.lib.Asserts
- * @run main TestFtpTimeValue
+ * @run main/othervm -Duser.timezone=UTC TestFtpTimeValue
+ * @run main/othervm -Duser.timezone=America/Los_Angeles TestFtpTimeValue
  */
 
 import jdk.test.lib.Asserts;
@@ -61,23 +62,24 @@ private enum TestCase {
             calendar.set(year, month - 1, day, hrs, min, sec);
             calendar.set(Calendar.MILLISECOND, milliseconds);
             expectedCreated = calendar.getTime();
-            var s = String.format("%4d%2d%2d%2d%2d%2d", year, month, day, hrs, min, sec);
+            var s = String.format("%4d%02d%02d%02d%02d%02d", year, month, day, hrs, min, sec);
             if (milliseconds != 0) {
-                s += "." + String.format("%3d", milliseconds);
+                s += "." + String.format("%03d", milliseconds);
             }
             create = s;
 
             calendar.add(GregorianCalendar.SECOND, 1);
             expectedModified = calendar.getTime();
-            s = String.format("%4d%2d%2d%2d%2d%2d", year, month, day, hrs, min, sec + 1);
+            s = String.format("%4d%02d%02d%02d%02d%02d", year, month, day, hrs, min, sec + 1);
             if (milliseconds != 0) {
-                s += "." + String.format("%3d", milliseconds);
+                s += "." + String.format("%03d", milliseconds);
             }
             modify = s;
         }
     }
 
     public static void main(String[] args) throws Exception {
+        System.out.println("user.timezone: " + System.getProperty("user.timezone"));
         try (FtpServer server = new FtpServer();
              FtpClient client = FtpClient.create()) {
             (new Thread(server)).start();