Very long response headers and java.net.http.HttpClient?

[Andy Boothe]

Ah! Right! Thanks for that. Moving now…

Andy Boothe
*Email*: andy.boothe at gmail.com
*Mobile*: (979) 574-1089


On Wed, Jul 24, 2024 at 4:30 PM Pavel Rappo <pavel.rappo at oracle.com> wrote:

> A proper list would be net-dev at openjdk.java.net.
>
>
> > On 24 Jul 2024, at 21:13, Andy Boothe <andy.boothe at gmail.com> wrote:
> >
> > Hello,
> >
> > 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.
> >
> > 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.
> >
> > I tried my best to search the archives for this mailing list for any
> mentions, but came up empty.
> >
> > 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.
> >
> > When I run LongResponseHeaderDemoServer in one terminal and make a curl
> request to the server in another terminal, this is what curl spits out:
> >
> > $ curl -vvv -D - http://localhost:3000
> > * Host localhost:3000 was resolved.
> > * IPv6: ::1
> > * IPv4: 127.0.0.1
> > *   Trying [::1]:3000...
> > * Connected to localhost (::1) port 3000
> > > GET / HTTP/1.1
> > > Host: localhost:3000
> > > User-Agent: curl/8.6.0
> > > Accept: */*
> > >
> > < HTTP/1.1 200 OK
> > HTTP/1.1 200 OK
> > < Content-Type: text/plain
> > Content-Type: text/plain
> > < Connection: close
> > Connection: close
> > < Content-Length: 3
> > Content-Length: 3
> > * Closing connection
> > curl: (100) A value or data field grew larger than allowed
> >
> > So curl detects the long response header and bails out. Safe and sane.
> >
> > However, when I run LongResponseHeaderDemoServer in one terminal and run
> LongResponseHeaderDemoHttpClient in another terminal, this is what happens:
> >
> > $ java LongResponseHeaderDemoHttpClient
> > Exception in thread "main" java.io.IOException: Requested array size
> exceeds VM limit
> > at
> java.net.http/jdk.internal.net.http.HttpClientImpl.send(HttpClientImpl.java:966)
> > at
> java.net.http/jdk.internal.net.http.HttpClientFacade.send(HttpClientFacade.java:133)
> > at
> LongResponseHeaderDemoHttpClient.main(LongResponseHeaderDemoHttpClient.java:13)
> > Caused by: java.lang.OutOfMemoryError: Requested array size exceeds VM
> limit
> > at java.base/java.util.Arrays.copyOf(Arrays.java:3541)
> > at
> java.base/java.lang.AbstractStringBuilder.ensureCapacityInternal(AbstractStringBuilder.java:242)
> > at
> java.base/java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:806)
> > at java.base/java.lang.StringBuilder.append(StringBuilder.java:246)
> > at
> java.net.http/jdk.internal.net.http.Http1HeaderParser.readResumeHeader(Http1HeaderParser.java:250)
> > at
> java.net.http/jdk.internal.net.http.Http1HeaderParser.parse(Http1HeaderParser.java:124)
> > at
> java.net.http/jdk.internal.net.http.Http1Response$HeadersReader.handle(Http1Response.java:605)
> > at
> java.net.http/jdk.internal.net.http.Http1Response$HeadersReader.handle(Http1Response.java:536)
> > at
> java.net.http/jdk.internal.net.http.Http1Response$Receiver.accept(Http1Response.java:527)
> > at
> java.net.http/jdk.internal.net.http.Http1Response$HeadersReader.tryAsyncReceive(Http1Response.java:583)
> > at
> java.net.http/jdk.internal.net.http.Http1AsyncReceiver.flush(Http1AsyncReceiver.java:233)
> > at
> java.net.http/jdk.internal.net.http.Http1AsyncReceiver$$Lambda/0x00000008010dbd50.run(Unknown
> Source)
> > at
> java.net.http/jdk.internal.net.http.common.SequentialScheduler$LockingRestartableTask.run(SequentialScheduler.java:182)
> > at
> java.net.http/jdk.internal.net.http.common.SequentialScheduler$CompleteRestartableTask.run(SequentialScheduler.java:149)
> > at
> java.net.http/jdk.internal.net.http.common.SequentialScheduler$SchedulableTask.run(SequentialScheduler.java:207)
> > at
> java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
> > at
> java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
> > at java.base/java.lang.Thread.runWith(Thread.java:1596)
> > at java.base/java.lang.Thread.run(Thread.java:1583)
> >
> > 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.
> >
> > 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:
> >
> > $ java LongResponseHeaderDemoHttpURLConnection
> > Exception in thread "main" java.lang.NegativeArraySizeException:
> -1610612736
> > at
> java.base/sun.net.www.MessageHeader.mergeHeader(MessageHeader.java:526)
> > at
> java.base/sun.net.www.MessageHeader.parseHeader(MessageHeader.java:481)
> > at
> java.base/sun.net.www.http.HttpClient.parseHTTPHeader(HttpClient.java:804)
> > at java.base/sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:726)
> > at
> java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1688)
> > at
> java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1589)
> > at java.base/java.net.URL.openStream(URL.java:1161)
> > at
> LongResponseHeaderDemoHttpURLConnection.main(LongResponseHeaderDemoHttpURLConnection.java:12)
> >
> > 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.
> >
> > For reference, here's my java version:
> >
> > $ java -version
> > openjdk version "21.0.2" 2024-01-16 LTS
> > OpenJDK Runtime Environment Corretto-21.0.2.13.1 (build 21.0.2+13-LTS)
> > OpenJDK 64-Bit Server VM Corretto-21.0.2.13.1 (build 21.0.2+13-LTS,
> mixed mode, sharing)
> >
> > 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?
> >
> > Andy Boothe
> > Email: andy.boothe at gmail.com
> > Mobile: (979) 574-1089
>
>
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