Stop parsing chunks once the chunk count limit is reached

[pjfanning]

Motivation

The max-chunk-count check in HttpMessageParser.parseChunkBody is missing its else:

if (chunkSize > 0) {
  if (chunkCount >= settings.maxChunkCount)
    failEntityStream(s"HTTP chunk count exceeds the configured limit of ${settings.maxChunkCount} chunks")
  val chunkBodyEnd = cursor + chunkSize
  ...  // emits the chunk and trampolines into the next one regardless

failEntityStream does not throw — it emits an EntityStreamError, sets terminated = true and returns a StateResult (done() is null). Its result is dropped here, so after the error the parser emits the current chunk, continues with the next one, and emits a further error for every remaining chunk in the buffer, i.e. it keeps producing output after it has terminated itself. Every other limit in this parser is written as if (cond) failEntityStream(...) else <continue>.

This is not a bypass: the error is emitted before the chunk, so a consumer that stops at the first error still fails the entity stream, which is presumably why it went unnoticed — there is no test for max-chunk-count in the repo. But the parser does work it should not, and it emits the whole rest of the body behind the error.

Modification

Move the rest of parseChunkBody into the else branch of the check.

Result

Nothing is emitted after the chunk count error and the parser stops parsing the remainder of the body.

Tests

• sbt "http-core/testOnly org.apache.pekko.http.impl.engine.parsing.RequestParserCRLFSpec org.apache.pekko.http.impl.engine.parsing.RequestParserLFSpec" - pass, with a new test that collects the raw parser output for a body of three chunks with max-chunk-count = 2. It asserts that only the chunks "a" and "b" are emitted and that the error is the last output. Without the change the parser emits "a", "b", "c", "", so the test fails. It deliberately reads the parser output directly, because the existing harness cancels the rest of the stream at the first error and therefore cannot see the difference.
• sbt http-core/test - pass (1216 tests)
• sbt http-core/mimaReportBinaryIssues - pass
• sbt http-core/scalafmt http-core/Test/scalafmt - clean

References

None - makes the max-chunk-count limit stop parsing