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<div class="PlainText">A proper list would be net-dev at openjdk.java.net.<br>
<br>
> On 24 Jul 2024, at 21:13, Andy Boothe <andy.boothe@gmail.com> wrote:<br>
> <br>
> Hello,<br>
> <br>
> I'm documenting some guidelines for using java.net.http.HttpClient defensively for my team. For example: "Always set a request timeout", "Don't assume HTTP response entities are small and/or will fit in memory", etc.<br>
> <br>
> One guideline I'd like to document is "Set a maximum for HTTP response header size." However, I can't seem to find a way to set that limit, either in documentation or in OpenJDK code.<br>
> <br>
> I tried my best to search the archives for this mailing list for any mentions, but came up empty.<br>
> <br>
> To make sure my head is on straight and there isn't an undocumented limit set by default, I wrote the attached (very quick and dirty) client and server programs. LongResponseHeaderDemoServer opens a raw server socket and reads (what it assumes is) a well-formed
HTTP request, and then prints an HTTP response which includes a response header of infinite length. LongResponseHeaderDemoHttpClient uses java.net.http.HttpClient to make a request and print the response body.<br>
> <br>
> When I run LongResponseHeaderDemoServer in one terminal and make a curl request to the server in another terminal, this is what curl spits out:<br>
> <br>
> $ curl -vvv -D - <a href="http://localhost:3000">http://localhost:3000</a><br>
> * Host localhost:3000 was resolved.<br>
> * IPv6: ::1<br>
> * IPv4: 127.0.0.1<br>
> * Trying [::1]:3000...<br>
> * Connected to localhost (::1) port 3000<br>
> > GET / HTTP/1.1<br>
> > Host: localhost:3000<br>
> > User-Agent: curl/8.6.0<br>
> > Accept: */*<br>
> > <br>
> < HTTP/1.1 200 OK<br>
> HTTP/1.1 200 OK<br>
> < Content-Type: text/plain<br>
> Content-Type: text/plain<br>
> < Connection: close<br>
> Connection: close<br>
> < Content-Length: 3<br>
> Content-Length: 3<br>
> * Closing connection<br>
> curl: (100) A value or data field grew larger than allowed<br>
> <br>
> So curl detects the long response header and bails out. Safe and sane.<br>
> <br>
> However, when I run LongResponseHeaderDemoServer in one terminal and run LongResponseHeaderDemoHttpClient in another terminal, this is what happens:<br>
> <br>
> $ java LongResponseHeaderDemoHttpClient <br>
> Exception in thread "main" java.io.IOException: Requested array size exceeds VM limit<br>
> at java.net.http/jdk.internal.net.http.HttpClientImpl.send(HttpClientImpl.java:966)<br>
> at java.net.http/jdk.internal.net.http.HttpClientFacade.send(HttpClientFacade.java:133)<br>
> at LongResponseHeaderDemoHttpClient.main(LongResponseHeaderDemoHttpClient.java:13)<br>
> Caused by: java.lang.OutOfMemoryError: Requested array size exceeds VM limit<br>
> at java.base/java.util.Arrays.copyOf(Arrays.java:3541)<br>
> at java.base/java.lang.AbstractStringBuilder.ensureCapacityInternal(AbstractStringBuilder.java:242)<br>
> at java.base/java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:806)<br>
> at java.base/java.lang.StringBuilder.append(StringBuilder.java:246)<br>
> at java.net.http/jdk.internal.net.http.Http1HeaderParser.readResumeHeader(Http1HeaderParser.java:250)<br>
> at java.net.http/jdk.internal.net.http.Http1HeaderParser.parse(Http1HeaderParser.java:124)<br>
> at java.net.http/jdk.internal.net.http.Http1Response$HeadersReader.handle(Http1Response.java:605)<br>
> at java.net.http/jdk.internal.net.http.Http1Response$HeadersReader.handle(Http1Response.java:536)<br>
> at java.net.http/jdk.internal.net.http.Http1Response$Receiver.accept(Http1Response.java:527)<br>
> at java.net.http/jdk.internal.net.http.Http1Response$HeadersReader.tryAsyncReceive(Http1Response.java:583)<br>
> at java.net.http/jdk.internal.net.http.Http1AsyncReceiver.flush(Http1AsyncReceiver.java:233)<br>
> at java.net.http/jdk.internal.net.http.Http1AsyncReceiver$$Lambda/0x00000008010dbd50.run(Unknown Source)<br>
> at java.net.http/jdk.internal.net.http.common.SequentialScheduler$LockingRestartableTask.run(SequentialScheduler.java:182)<br>
> at java.net.http/jdk.internal.net.http.common.SequentialScheduler$CompleteRestartableTask.run(SequentialScheduler.java:149)<br>
> at java.net.http/jdk.internal.net.http.common.SequentialScheduler$SchedulableTask.run(SequentialScheduler.java:207)<br>
> at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)<br>
> at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)<br>
> at java.base/java.lang.Thread.runWith(Thread.java:1596)<br>
> at java.base/java.lang.Thread.run(Thread.java:1583)<br>
> <br>
> Ostensibly, HttpClient just keeps on reading the never-ending header until it OOMs. This seems to confirm that there is no default limit to header size. It also seems like A Very Bad Thing to me. This suggests that any time a program makes an HTTP request
to an untrusted source using HttpClient, for example when crawling the web, they are at risk of an OOM.<br>
> <br>
> For grins, I also wrote an application LongResponseHeaderDemoHttpURLConnection that does the same thing as LongResponseHeaderDemoHttpClient, just using HttpURLConnection instead of HttpClient. When I run LongResponseHeaderDemoServer in one terminal and LongResponseHeaderDemoHttpURLConnection
in another terminal, this is what happens:<br>
> <br>
> $ java LongResponseHeaderDemoHttpURLConnection<br>
> Exception in thread "main" java.lang.NegativeArraySizeException: -1610612736<br>
> at java.base/sun.net.www.MessageHeader.mergeHeader(MessageHeader.java:526)<br>
> at java.base/sun.net.www.MessageHeader.parseHeader(MessageHeader.java:481)<br>
> at java.base/sun.net.www.http.HttpClient.parseHTTPHeader(HttpClient.java:804)<br>
> at java.base/sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:726)<br>
> at java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1688)<br>
> at java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1589)<br>
> at java.base/java.net.URL.openStream(URL.java:1161)<br>
> at LongResponseHeaderDemoHttpURLConnection.main(LongResponseHeaderDemoHttpURLConnection.java:12)<br>
> <br>
> So HttpURLConnection doesn't handle things gracefully either, but at least it doesn't OOM. That seems like a bug, too, but perhaps less severe.<br>
> <br>
> For reference, here's my java version:<br>
> <br>
> $ java -version<br>
> openjdk version "21.0.2" 2024-01-16 LTS<br>
> OpenJDK Runtime Environment Corretto-21.0.2.13.1 (build 21.0.2+13-LTS)<br>
> OpenJDK 64-Bit Server VM Corretto-21.0.2.13.1 (build 21.0.2+13-LTS, mixed mode, sharing)<br>
> <br>
> Can anyone check my work, and maybe reproduce? And ideally, can someone with more knowledge than me about java.net.http.HttpClient and/or java.net.HttpURLConnection please comment? Is this real, or have I made a mistake somewhere along the way? If it's real,
what's next? A bug report?<br>
> <br>
> Andy Boothe<br>
> Email: andy.boothe@gmail.com<br>
> Mobile: (979) 574-1089<br>
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