Prevent infinite loop in CronAdjuster with invalid date combinations (#4548)

Signed-off-by: Jimmy Tanagra <jcode@tanagra.id.au>

bundles/org.openhab.core/src/main/java/org/openhab/core/scheduler/CronAdjuster.java

@@ -71,6 +71,7 @@ public class CronAdjuster implements SchedulerTemporalAdjuster {
             .collect(Collectors.toMap(Entry::getKey, Entry::getValue));
 
     private final List<Field> fields = new ArrayList<>(7);
+    private String cronExpression;
     private final Map<String, String> environmentMap;
     private final boolean reboot;
 
@@ -82,6 +83,7 @@ public class CronAdjuster implements SchedulerTemporalAdjuster {
         environmentMap = parseEnvironment(entries);
 
         String cronExpression = entries[entries.length - 1].trim();
+        this.cronExpression = cronExpression;
 
         reboot = "@reboot".equals(cronExpression);
 
@@ -515,6 +517,7 @@ public class CronAdjuster implements SchedulerTemporalAdjuster {
         // we start over with this new time.
 
         int index = 0;
+        int restarts = 0;
         final int length = fields.size();
 
         while (index < length) {
@@ -525,6 +528,10 @@ public class CronAdjuster implements SchedulerTemporalAdjuster {
             if (out == null) {
                 index++;
             } else {
+                if (restarts++ > 1000) {
+                    throw new IllegalArgumentException(
+                            String.format("Cron expression '%s' is not valid, too many restarts", cronExpression));
+                }
                 ret = out;
                 index = 0;
             }

bundles/org.openhab.core/src/test/java/org/openhab/core/internal/scheduler/CronAdjusterTest.java

@@ -14,6 +14,7 @@ package org.openhab.core.internal.scheduler;
 
 import static org.hamcrest.CoreMatchers.equalTo;
 import static org.hamcrest.MatcherAssert.assertThat;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import java.time.LocalDateTime;
 import java.time.temporal.Temporal;
@@ -25,6 +26,7 @@ import org.eclipse.jdt.annotation.NonNullByDefault;
 import org.junit.jupiter.api.Timeout;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.MethodSource;
+import org.junit.jupiter.params.provider.ValueSource;
 import org.openhab.core.scheduler.CronAdjuster;
 
 /**
@@ -197,4 +199,13 @@ public class CronAdjusterTest {
                     equalTo(out));
         }
     }
+
+    @ParameterizedTest
+    @ValueSource(strings = { "0 0 0 31 2 *", "* * *", "80 * * * * *" })
+    public void testInvalidCronExpression(String cron) {
+        assertThrows(IllegalArgumentException.class, () -> {
+            final CronAdjuster cronAdjuster = new CronAdjuster(cron);
+            cronAdjuster.adjustInto(java.time.ZonedDateTime.now());
+        });
+    }
 }