Deflate decompression doesn't fail for truncated input

[vojtarylko]

I tried to extend HTTPRequestDecompressorTest with this test case:

    func testDecompressionTruncatedInput() throws {
        // Truncated compressed data
        let compressed = ByteBuffer(bytes: [120, 156, 99, 0])

        let channel = EmbeddedChannel()
        try channel.pipeline.addHandler(NIOHTTPRequestDecompressor(limit: .none)).wait()
        let headers = HTTPHeaders([("Content-Encoding", "deflate"), ("Content-Length", "\(compressed.readableBytes)")])
        try channel.writeInbound(HTTPServerRequestPart.head(.init(version: .init(major: 1, minor: 1), method: .POST, uri: "https://nio.swift.org/test", headers: headers)))

        do {
            try channel.writeInbound(HTTPServerRequestPart.body(compressed))
            XCTFail("writeInbound should fail")
        } catch let error as NIOHTTPDecompression.DecompressionError {
            switch error {
            case .inflationError(Int(Z_BUF_ERROR)):
                // ok
                break
            default:
                XCTFail("Unexptected error: \(error)")
            }
        }
    }

As you can see I'm sending truncated invalid compressed data. I'd expect to get DecompressionError.inflationError(-5). Instead decompression succeeds.

(I guess root cause is in z_stream_s.inflatePart(to:minimumCapacity:) which always calls inflate with Z_NO_FLUSH parameter.)

Is the problem in my test case, or in the NIO code?

[Lukasa]

NIOHTTPRequestDecompressor does not assume the message is finished until it receives a HTTPServerRequestPart.end. In this instance I suspect we should see an error if we also send .end, but looking at the code I wonder if we're discarding the error result from dropping the decoder. It may be worth adding a send of .end after the send of .body, and then checking to see if there's an error reported here that we're losing:

swift-nio-extras/Sources/NIOHTTPCompression/HTTPDecompression.swift

Line 114 in 5334d94

inflateEnd(&self.stream)

[vojtarylko]

The inflateEnd(&self.stream) returns just Z_OK when I add try channel.writeInbound(HTTPServerRequestPart.end(nil)) into test.

[Lukasa]

Good catch, resolved by #177.