Fix java/tainted-arithmetic CodeQL alerts

opendj-core/src/main/java/org/forgerock/opendj/ldap/ByteSequenceReader.java

@@ -499,7 +499,11 @@ public byte peek(int offset) {
      *             of the underlying byte sequence.
      */
     public void skip(final int length) {
-        position(pos + length);
+        final long newPos = (long) pos + length;
+        if (newPos < 0 || newPos > sequence.length()) {
+            throw new IndexOutOfBoundsException();
+        }
+        position((int) newPos);
     }
 
     @Override

opendj-core/src/main/java/org/forgerock/opendj/ldap/GeneralizedTime.java

@@ -12,6 +12,7 @@
  * information: "Portions Copyright [year] [name of copyright owner]".
  *
  * Copyright 2012-2016 ForgeRock AS.
+ * Portions Copyrighted 2026 3A Systems, LLC.
  */
 package org.forgerock.opendj.ldap;
 
@@ -653,7 +654,13 @@
             throw new LocalizedIllegalArgumentException(message);
         }
 
-        final Double fractionValue = Double.parseDouble(fractionBuffer.toString());
+        final double fractionValue = Double.parseDouble(fractionBuffer.toString());
+        if (!(fractionValue >= 0.0d && fractionValue < 1.0d)) {
+            // Cannot happen: the buffer contains "0." followed by decimal digits.
+            final LocalizableMessage message =
+                    WARN_ATTR_SYNTAX_GENERALIZED_TIME_ILLEGAL_TIME.get(value, fractionBuffer);
+            throw new LocalizedIllegalArgumentException(message);
+        }
         final int additionalMilliseconds = (int) Math.round(fractionValue * multiplier);
 
         try {

opendj-server-legacy/src/main/java/org/opends/server/replication/common/CSN.java

@@ -13,6 +13,7 @@
  *
  * Copyright 2006-2009 Sun Microsystems, Inc.
  * Portions Copyright 2013-2015 ForgeRock AS.
+ * Portions Copyrighted 2026 3A Systems, LLC.
  */
 package org.opends.server.replication.common;
 
@@ -319,11 +320,11 @@ else if (csn1.timeStamp != csn2.timeStamp)
     }
     else if (csn1.seqnum != csn2.seqnum)
     {
-      return csn1.seqnum - csn2.seqnum;
+      return Integer.compare(csn1.seqnum, csn2.seqnum);
     }
     else
     {
-      return csn1.serverId - csn2.serverId;
+      return Integer.compare(csn1.serverId, csn2.serverId);
     }
   }