Impact
If a Content-Length header is present in the original HTTP/2 request, the field is not validated by Http2MultiplexHandler as it is propagated up. This is fine as long as the request is not proxied through as HTTP/1.1.
If the request comes in as an HTTP/2 stream, gets converted into the HTTP/1.1 domain objects (HttpRequest, HttpContent, etc.) via Http2StreamFrameToHttpObjectCodec and then sent up to the child channel's pipeline and proxied through a remote peer as HTTP/1.1 this may result in request smuggling.
In a proxy case, users may assume the content-length is validated somehow, which is not the case. If the request is forwarded to a backend channel that is a HTTP/1.1 connection, the Content-Length now has meaning and needs to be checked.
An attacker can smuggle requests inside the body as it gets downgraded from HTTP/2 to HTTP/1.1. A sample attack request looks like:
POST / HTTP/2
:authority:: externaldomain.com
Content-Length: 4
asdfGET /evilRedirect HTTP/1.1
Host: internaldomain.com
Users are only affected if all of this is true:
HTTP2MultiplexCodec or Http2FrameCodec is usedHttp2StreamFrameToHttpObjectCodec is used to convert to HTTP/1.1 objects- These HTTP/1.1 objects are forwarded to another remote peer.
Patches
This has been patched in 4.1.60.Final
Workarounds
The user can do the validation by themselves by implementing a custom ChannelInboundHandler that is put in the ChannelPipeline behind Http2StreamFrameToHttpObjectCodec.
References
Related change to workaround the problem: Netflix/zuul#980
artgon Analyst
carl-mastrangelo Analyst
Impact
If a Content-Length header is present in the original HTTP/2 request, the field is not validated by
Http2MultiplexHandleras it is propagated up. This is fine as long as the request is not proxied through as HTTP/1.1.If the request comes in as an HTTP/2 stream, gets converted into the HTTP/1.1 domain objects (
HttpRequest,HttpContent, etc.) viaHttp2StreamFrameToHttpObjectCodecand then sent up to the child channel's pipeline and proxied through a remote peer as HTTP/1.1 this may result in request smuggling.In a proxy case, users may assume the content-length is validated somehow, which is not the case. If the request is forwarded to a backend channel that is a HTTP/1.1 connection, the Content-Length now has meaning and needs to be checked.
An attacker can smuggle requests inside the body as it gets downgraded from HTTP/2 to HTTP/1.1. A sample attack request looks like:
Users are only affected if all of this is
true:HTTP2MultiplexCodecorHttp2FrameCodecis usedHttp2StreamFrameToHttpObjectCodecis used to convert to HTTP/1.1 objectsPatches
This has been patched in 4.1.60.Final
Workarounds
The user can do the validation by themselves by implementing a custom
ChannelInboundHandlerthat is put in theChannelPipelinebehindHttp2StreamFrameToHttpObjectCodec.References
Related change to workaround the problem: Netflix/zuul#980