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net/http/httputil: ReverseProxy should copy *req.URL #20068

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aronatkins opened this issue Apr 21, 2017 · 4 comments
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net/http/httputil: ReverseProxy should copy *req.URL #20068

aronatkins opened this issue Apr 21, 2017 · 4 comments
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@aronatkins
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The ReverseProxy.ServeHTTP performs a shallow copy of the incoming request. This includes just copying the pointer of req.URL to outreq.URL. The director is likely to mutate that request URL, which can lead to mismatched pre/post logging.

Workaround: Copy the url.URL within a custom director.

What version of Go are you using (go version)?

go version go1.8.1 darwin/amd64

What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/aron/go"
GORACE=""
GOROOT="/usr/local/go"
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/ts/s940qvdj5vj1czr9qh07fvtw0000gn/T/go-build348823784=/tmp/go-build -gno-record-gcc-switches -fno-common"
CXX="clang++"
CGO_ENABLED="1"
PKG_CONFIG="pkg-config"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"

What did you do?

package main

import (
	"log"
	"net/http"
	"net/http/httputil"
	"net/url"
)

func main() {
	target, err := url.Parse("http://google.com/")
	if err != nil {
		log.Fatalf("could not parse URL: %s", err)
	}
	pxy := httputil.NewSingleHostReverseProxy(target)
	server := http.Server{
		Addr: ":9999",
		Handler: http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			log.Printf("proxy starting: %s", r.URL)
			pxy.ServeHTTP(w, r)
			log.Printf("proxy complete: %s", r.URL)
		}),
	}
	err = server.ListenAndServe()
	if err != nil {
		log.Fatalf("could not serve: %s", err)
	}
}
$ curl http://localhost:9999/ > /dev/null

What did you expect to see?

2017/04/21 11:14:54 proxy starting: /
2017/04/21 11:14:54 proxy complete: /

What did you see instead?

2017/04/21 11:14:54 proxy starting: /
2017/04/21 11:14:54 proxy complete: http://google.com/
@odeke-em
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/cc @bradfitz, I think the day of reckoning has arrived, for us to modify Request.WithContext https://golang.org/pkg/net/http/#Request.WithContext to perform some deep copies e.g for URL as requested by the issue. What do you think?

@gopherbot
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CL https://golang.org/cl/41308 mentions this issue.

@aronatkins
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This issue is also similar to #18327, which is trying to establish what is possible/recommended in the director.

@CSEMike
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CSEMike commented May 19, 2017

Also related: #19706

@bradfitz bradfitz mentioned this issue Jun 7, 2017
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@paranoiacblack paranoiacblack mentioned this issue Jan 24, 2018
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@golang golang locked and limited conversation to collaborators May 24, 2018
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@CSEMike @aronatkins @odeke-em @gopherbot