From be65bc3f8643ea7a61ec223776141fc8d9e9b39f Mon Sep 17 00:00:00 2001
From: Stephen Heywood <stephen@ii.coop>
Date: Mon, 4 Oct 2021 16:36:36 +1300
Subject: [PATCH] Redirect proxy requests for only GET & HEAD methods

- Extract the current redirect code into a function
  (proxyRedirectsforRootPath) and redirect for only
  http.MethodGet or http.MethodHead
- Create a unit test that confirms that only GET &
  HEAD methods are redirected
---
 .../pkg/util/proxy/upgradeaware.go            | 33 ++++++---
 .../pkg/util/proxy/upgradeaware_test.go       | 71 +++++++++++++++++++
 2 files changed, 93 insertions(+), 11 deletions(-)

diff --git a/staging/src/k8s.io/apimachinery/pkg/util/proxy/upgradeaware.go b/staging/src/k8s.io/apimachinery/pkg/util/proxy/upgradeaware.go
index cda35380459..e84548017f5 100644
--- a/staging/src/k8s.io/apimachinery/pkg/util/proxy/upgradeaware.go
+++ b/staging/src/k8s.io/apimachinery/pkg/util/proxy/upgradeaware.go
@@ -192,6 +192,26 @@ func NewUpgradeAwareHandler(location *url.URL, transport http.RoundTripper, wrap
 	}
 }
 
+func proxyRedirectsforRootPath(path string, w http.ResponseWriter, req *http.Request) bool {
+	redirect := false
+	method := req.Method
+
+	// From pkg/genericapiserver/endpoints/handlers/proxy.go#ServeHTTP:
+	// Redirect requests with an empty path to a location that ends with a '/'
+	// This is essentially a hack for http://issue.k8s.io/4958.
+	// Note: Keep this code after tryUpgrade to not break that flow.
+	if len(path) == 0 && (method == http.MethodGet || method == http.MethodHead) {
+		var queryPart string
+		if len(req.URL.RawQuery) > 0 {
+			queryPart = "?" + req.URL.RawQuery
+		}
+		w.Header().Set("Location", req.URL.Path+"/"+queryPart)
+		w.WriteHeader(http.StatusMovedPermanently)
+		redirect = true
+	}
+	return redirect
+}
+
 // ServeHTTP handles the proxy request
 func (h *UpgradeAwareHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	if h.tryUpgrade(w, req) {
@@ -211,17 +231,8 @@ func (h *UpgradeAwareHandler) ServeHTTP(w http.ResponseWriter, req *http.Request
 		loc.Path += "/"
 	}
 
-	// From pkg/genericapiserver/endpoints/handlers/proxy.go#ServeHTTP:
-	// Redirect requests with an empty path to a location that ends with a '/'
-	// This is essentially a hack for http://issue.k8s.io/4958.
-	// Note: Keep this code after tryUpgrade to not break that flow.
-	if len(loc.Path) == 0 {
-		var queryPart string
-		if len(req.URL.RawQuery) > 0 {
-			queryPart = "?" + req.URL.RawQuery
-		}
-		w.Header().Set("Location", req.URL.Path+"/"+queryPart)
-		w.WriteHeader(http.StatusMovedPermanently)
+	proxyRedirect := proxyRedirectsforRootPath(loc.Path, w, req)
+	if proxyRedirect {
 		return
 	}
 
diff --git a/staging/src/k8s.io/apimachinery/pkg/util/proxy/upgradeaware_test.go b/staging/src/k8s.io/apimachinery/pkg/util/proxy/upgradeaware_test.go
index f7f34be5d53..cb71b7e2702 100644
--- a/staging/src/k8s.io/apimachinery/pkg/util/proxy/upgradeaware_test.go
+++ b/staging/src/k8s.io/apimachinery/pkg/util/proxy/upgradeaware_test.go
@@ -1055,6 +1055,77 @@ func TestErrorPropagation(t *testing.T) {
 	}
 }
 
+func TestProxyRedirectsforRootPath(t *testing.T) {
+
+	tests := []struct {
+		name               string
+		method             string
+		requestPath        string
+		expectedHeader     http.Header
+		expectedStatusCode int
+		redirect           bool
+	}{
+		{
+			name:               "root path, simple get",
+			method:             "GET",
+			requestPath:        "",
+			redirect:           true,
+			expectedStatusCode: 301,
+			expectedHeader: http.Header{
+				"Location": []string{"/"},
+			},
+		},
+		{
+			name:               "root path, simple put",
+			method:             "PUT",
+			requestPath:        "",
+			redirect:           false,
+			expectedStatusCode: 200,
+		},
+		{
+			name:               "root path, simple head",
+			method:             "HEAD",
+			requestPath:        "",
+			redirect:           true,
+			expectedStatusCode: 301,
+			expectedHeader: http.Header{
+				"Location": []string{"/"},
+			},
+		},
+		{
+			name:               "root path, simple delete with params",
+			method:             "DELETE",
+			requestPath:        "",
+			redirect:           false,
+			expectedStatusCode: 200,
+		},
+	}
+
+	for _, test := range tests {
+		func() {
+			w := httptest.NewRecorder()
+			req, err := http.NewRequest(test.method, test.requestPath, nil)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			redirect := proxyRedirectsforRootPath(test.requestPath, w, req)
+			if got, want := redirect, test.redirect; got != want {
+				t.Errorf("Expected redirect state %v; got %v", want, got)
+			}
+
+			res := w.Result()
+			if got, want := res.StatusCode, test.expectedStatusCode; got != want {
+				t.Errorf("Expected status code %d; got %d", want, got)
+			}
+
+			if res.StatusCode == 301 && !reflect.DeepEqual(res.Header, test.expectedHeader) {
+				t.Errorf("Expected location header to be %v, got %v", test.expectedHeader, res.Header)
+			}
+		}()
+	}
+}
+
 // exampleCert was generated from crypto/tls/generate_cert.go with the following command:
 //    go run generate_cert.go  --rsa-bits 1024 --host example.com --ca --start-date "Jan 1 00:00:00 1970" --duration=1000000h
 var exampleCert = []byte(`-----BEGIN CERTIFICATE-----