Hello, I'm moving this thread from jdk-dev to this list on the sage advice of Pavel Rappo.
As a brief recap, it looks like HttpClient and HttpURLConnection do not currently support a way to set the maximum acceptable response header length. As a result, sending HTTP requests with these classes that result in a response with very long headers causes an OutOfMemoryError and a NegativeArraySizeException, respectively. (Simple programs for reproducing the issue are attached.) This seems like A Bad Thing. There is a (very brief) discussion in the thread about how to handle, but of course you guys are the experts. If my head is on straight and this turns out to be a real issue as opposed to a mistake on my part, I'm keen to help however I can. Andy Boothe *Email*: andy.boo...@gmail.com *Mobile*: (979) 574-1089 ---------- Forwarded message --------- From: Pavel Rappo <pavel.ra...@oracle.com> Date: Wed, Jul 24, 2024 at 4:30 PM Subject: Re: Very long response headers and java.net.http.HttpClient? To: Andy Boothe <andy.boo...@gmail.com> Cc: jdk-...@openjdk.org <jdk-...@openjdk.org> A proper list would be net-dev at openjdk.java.net. > On 24 Jul 2024, at 21:13, Andy Boothe <andy.boo...@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.boo...@gmail.com > Mobile: (979) 574-1089
LongResponseHeaderDemoHttpClient.java
Description: application/ms-java
LongResponseHeaderDemoHttpURLConnection.java
Description: application/ms-java
LongResponseHeaderDemoServer.java
Description: application/ms-java
