Apply Jackson stream read constraints defaults at runtime (#16832) (#16845)

When Logstash 8.12.0 added increased Jackson stream read constraints to
jvm.options, assumptions about the existence of that file's contents
were invalidated. This led to issues like #16683.

This change ensures Logstash applies defaults from config at runtime:
- MAX_STRING_LENGTH: 200_000_000
- MAX_NUMBER_LENGTH: 10_000
- MAX_NESTING_DEPTH: 1_000

These match the jvm.options defaults and are applied even when config
is missing. Config values still override these defaults when present.

(cherry picked from commit cc608eb)

Co-authored-by: Cas Donoghue <[email protected]>

Author: github-actions[bot]

logstash-core/src/main/java/org/logstash/jackson/StreamReadConstraintsUtil.java

@@ -18,6 +18,14 @@ public class StreamReadConstraintsUtil {
 
     private StreamReadConstraints configuredStreamReadConstraints;
 
+    // Provide default values for Jackson constraints in the case they are
+    // not specified in configuration file.
+    private static final Map<Override, Integer> JACKSON_DEFAULTS = Map.of(
+        Override.MAX_STRING_LENGTH, 200_000_000,
+        Override.MAX_NUMBER_LENGTH, 10_000,
+        Override.MAX_NESTING_DEPTH, 1_000
+    );
+
     enum Override {
         MAX_STRING_LENGTH(StreamReadConstraints.Builder::maxStringLength, StreamReadConstraints::getMaxStringLength),
         MAX_NUMBER_LENGTH(StreamReadConstraints.Builder::maxNumberLength, StreamReadConstraints::getMaxNumberLength),
@@ -78,6 +86,8 @@ StreamReadConstraints get() {
         if (configuredStreamReadConstraints == null) {
             final StreamReadConstraints.Builder builder = StreamReadConstraints.defaults().rebuild();
 
+            // Apply the Jackson defaults first, then the overrides from config
+            JACKSON_DEFAULTS.forEach((override, value) -> override.applicator.apply(builder, value));
             eachOverride((override, value) -> override.applicator.apply(builder, value));
 
             this.configuredStreamReadConstraints = builder.build();

logstash-core/src/test/java/org/logstash/jackson/StreamReadConstraintsUtilTest.java

@@ -26,6 +26,10 @@ public class StreamReadConstraintsUtilTest {
     private ListAppender listAppender;
     private Logger observedLogger;
 
+    private static final int DEFAULT_MAX_STRING_LENGTH = 200_000_000;
+    private static final int DEFAULT_MAX_NUMBER_LENGTH = 10_000;
+    private static final int DEFAULT_MAX_NESTING_DEPTH = 1_000;
+
     @Before
     public void setUpLoggingListAppender() {
         int i = 1+16;
@@ -51,8 +55,8 @@ public void configuresMaxStringLength() {
             assertThat(configuredConstraints).as("inherited defaults")
                     .returns(defaults.getMaxDocumentLength(), from(StreamReadConstraints::getMaxDocumentLength))
                     .returns(defaults.getMaxNameLength(), from(StreamReadConstraints::getMaxNameLength))
-                    .returns(defaults.getMaxNestingDepth(), from(StreamReadConstraints::getMaxNestingDepth))
-                    .returns(defaults.getMaxNumberLength(), from(StreamReadConstraints::getMaxNumberLength));
+                    .returns(DEFAULT_MAX_NESTING_DEPTH, from(StreamReadConstraints::getMaxNestingDepth))
+                    .returns(DEFAULT_MAX_NUMBER_LENGTH, from(StreamReadConstraints::getMaxNumberLength));
 
             assertThatThrownBy(configuredUtil::validateIsGlobalDefault).isInstanceOf(IllegalStateException.class).hasMessageContaining(MAX_STRING_LENGTH.propertyName);
 
@@ -94,8 +98,8 @@ public void configuresMaxNumberLength() {
             assertThat(configuredConstraints).as("inherited defaults")
                     .returns(defaults.getMaxDocumentLength(), from(StreamReadConstraints::getMaxDocumentLength))
                     .returns(defaults.getMaxNameLength(), from(StreamReadConstraints::getMaxNameLength))
-                    .returns(defaults.getMaxNestingDepth(), from(StreamReadConstraints::getMaxNestingDepth))
-                    .returns(defaults.getMaxStringLength(), from(StreamReadConstraints::getMaxStringLength));
+                    .returns(DEFAULT_MAX_NESTING_DEPTH, from(StreamReadConstraints::getMaxNestingDepth))
+                    .returns(DEFAULT_MAX_STRING_LENGTH, from(StreamReadConstraints::getMaxStringLength));
 
             assertThatThrownBy(configuredUtil::validateIsGlobalDefault).isInstanceOf(IllegalStateException.class).hasMessageContaining(MAX_NUMBER_LENGTH.propertyName);
 
@@ -137,8 +141,8 @@ public void configuresMaxNestingDepth() {
             assertThat(configuredConstraints).as("inherited defaults")
                     .returns(defaults.getMaxDocumentLength(), from(StreamReadConstraints::getMaxDocumentLength))
                     .returns(defaults.getMaxNameLength(), from(StreamReadConstraints::getMaxNameLength))
-                    .returns(defaults.getMaxStringLength(), from(StreamReadConstraints::getMaxStringLength))
-                    .returns(defaults.getMaxNumberLength(), from(StreamReadConstraints::getMaxNumberLength));
+                    .returns(DEFAULT_MAX_STRING_LENGTH, from(StreamReadConstraints::getMaxStringLength))
+                    .returns(DEFAULT_MAX_NUMBER_LENGTH, from(StreamReadConstraints::getMaxNumberLength));
 
             assertThatThrownBy(configuredUtil::validateIsGlobalDefault).isInstanceOf(IllegalStateException.class).hasMessageContaining(MAX_NESTING_DEPTH.propertyName);
 
@@ -193,6 +197,31 @@ public void validatesApplication() {
         assertLogObserved(Level.WARN, "override `" + PROP_PREFIX + "unsupported-option1` is unknown and has been ignored");
     }
 
+    @Test
+    public void usesJacksonDefaultsWhenNoConfig() {
+        StreamReadConstraintsUtil util = new StreamReadConstraintsUtil(new Properties(), this.observedLogger);
+        StreamReadConstraints constraints = util.get();
+
+        assertThat(constraints)
+            .returns(DEFAULT_MAX_STRING_LENGTH, from(StreamReadConstraints::getMaxStringLength))
+            .returns(DEFAULT_MAX_NUMBER_LENGTH, from(StreamReadConstraints::getMaxNumberLength))
+            .returns(DEFAULT_MAX_NESTING_DEPTH, from(StreamReadConstraints::getMaxNestingDepth));
+    }
+
+    @Test
+    public void configOverridesDefault() {
+        Properties props = new Properties();
+        props.setProperty("logstash.jackson.stream-read-constraints.max-string-length", "100");
+
+        StreamReadConstraintsUtil util = new StreamReadConstraintsUtil(props, this.observedLogger);
+        StreamReadConstraints constraints = util.get();
+
+        assertThat(constraints)
+            .returns(100, from(StreamReadConstraints::getMaxStringLength))
+            .returns(DEFAULT_MAX_NUMBER_LENGTH, from(StreamReadConstraints::getMaxNumberLength))
+            .returns(DEFAULT_MAX_NESTING_DEPTH, from(StreamReadConstraints::getMaxNestingDepth));
+    }
+
     private void assertLogObserved(final Level level, final String... messageFragments) {
         List<LogEvent> logEvents = listAppender.getEvents();
         assertThat(logEvents)