Validate ingress path fields (#9309)

* Validate characters in path fields

* Add e2e tests for path validation

* Fix review comments

internal/ingress/controller/store/store.go

@@ -59,6 +59,7 @@ import (
 	"k8s.io/ingress-nginx/internal/ingress/resolver"
 	"k8s.io/ingress-nginx/internal/k8s"
 	"k8s.io/ingress-nginx/pkg/apis/ingress"
+	ingressutils "k8s.io/ingress-nginx/pkg/util/ingress"
 )
 
 // IngressFilterFunc decides if an Ingress should be omitted or not
@@ -861,6 +862,10 @@ func (s *k8sStore) syncIngress(ing *networkingv1.Ingress) {
 			if path.Path == "" {
 				copyIng.Spec.Rules[ri].HTTP.Paths[pi].Path = "/"
 			}
+			if !ingressutils.IsSafePath(copyIng, path.Path) {
+				klog.Warningf("ingress %s contains invalid path %s", key, path.Path)
+				return
+			}
 		}
 	}
 

pkg/util/ingress/ingress.go

@@ -18,15 +18,30 @@ package ingress
 
 import (
 	"fmt"
+	"regexp"
 	"strings"
 
+	networkingv1 "k8s.io/api/networking/v1"
 	"k8s.io/apimachinery/pkg/util/sets"
+	"k8s.io/ingress-nginx/internal/ingress/annotations/parser"
 	"k8s.io/ingress-nginx/internal/k8s"
 	"k8s.io/ingress-nginx/internal/net/ssl"
 	"k8s.io/ingress-nginx/pkg/apis/ingress"
 	"k8s.io/klog/v2"
 )
 
+const (
+	alphaNumericChars = `\-\.\_\~a-zA-Z0-9/`
+	regexEnabledChars = `\^\$\[\]\(\)\{\}\*\+`
+)
+
+var (
+	// pathAlphaNumeric is a regex validation of something like "^/[a-zA-Z]+$" on path
+	pathAlphaNumeric = regexp.MustCompile("^/[" + alphaNumericChars + "]*$").MatchString
+	// pathRegexEnabled is a regex validation of paths that may contain regex.
+	pathRegexEnabled = regexp.MustCompile("^/[" + alphaNumericChars + regexEnabledChars + "]*$").MatchString
+)
+
 func GetRemovedHosts(rucfg, newcfg *ingress.Configuration) []string {
 	oldSet := sets.NewString()
 	newSet := sets.NewString()
@@ -231,3 +246,13 @@ func BuildRedirects(servers []*ingress.Server) []*redirect {
 
 	return redirectServers
 }
+
+// IsSafePath verifies if the path used in ingress object contains only valid characters.
+// It will behave differently if regex is enabled or not
+func IsSafePath(copyIng *networkingv1.Ingress, path string) bool {
+	isRegex, _ := parser.GetBoolAnnotation("use-regex", copyIng)
+	if isRegex {
+		return pathRegexEnabled(path)
+	}
+	return pathAlphaNumeric(path)
+}

pkg/util/ingress/ingress_test.go

@@ -17,8 +17,13 @@ limitations under the License.
 package ingress
 
 import (
+	"fmt"
 	"testing"
 
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+
+	networkingv1 "k8s.io/api/networking/v1"
+	"k8s.io/ingress-nginx/internal/ingress/annotations/parser"
 	"k8s.io/ingress-nginx/pkg/apis/ingress"
 )
 
@@ -130,3 +135,83 @@ func TestIsDynamicConfigurationEnough(t *testing.T) {
 		t.Errorf("Expected new config to not change")
 	}
 }
+
+func generateDumbIngressforPathTest(regexEnabled bool) *networkingv1.Ingress {
+	var annotations = make(map[string]string)
+	regexAnnotation := fmt.Sprintf("%s/use-regex", parser.AnnotationsPrefix)
+	if regexEnabled {
+		annotations[regexAnnotation] = "true"
+	}
+	return &networkingv1.Ingress{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:        "dumb",
+			Namespace:   "default",
+			Annotations: annotations,
+		},
+	}
+}
+
+func TestIsSafePath(t *testing.T) {
+	tests := []struct {
+		name    string
+		copyIng *networkingv1.Ingress
+		path    string
+		want    bool
+	}{
+		{
+			name:    "should accept valid path with regex disabled",
+			want:    true,
+			copyIng: generateDumbIngressforPathTest(false),
+			path:    "/xpto/~user/t-e_st.exe",
+		},
+		{
+			name:    "should accept valid path / with regex disabled",
+			want:    true,
+			copyIng: generateDumbIngressforPathTest(false),
+			path:    "/",
+		},
+		{
+			name:    "should reject invalid path with invalid chars",
+			want:    false,
+			copyIng: generateDumbIngressforPathTest(false),
+			path:    "/foo/bar/;xpto",
+		},
+		{
+			name:    "should reject regex path when regex is disabled",
+			want:    false,
+			copyIng: generateDumbIngressforPathTest(false),
+			path:    "/foo/bar/(.+)",
+		},
+		{
+			name:    "should accept valid path / with regex enabled",
+			want:    true,
+			copyIng: generateDumbIngressforPathTest(true),
+			path:    "/",
+		},
+		{
+			name:    "should accept regex path when regex is enabled",
+			want:    true,
+			copyIng: generateDumbIngressforPathTest(true),
+			path:    "/foo/bar/(.+)",
+		},
+		{
+			name:    "should reject regex path when regex is enabled but the path is invalid",
+			want:    false,
+			copyIng: generateDumbIngressforPathTest(true),
+			path:    "/foo/bar/;xpto",
+		},
+		{
+			name:    "should reject regex path when regex is enabled but the path is invalid",
+			want:    false,
+			copyIng: generateDumbIngressforPathTest(true),
+			path:    ";xpto",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := IsSafePath(tt.copyIng, tt.path); got != tt.want {
+				t.Errorf("IsSafePath() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

test/e2e/security/invalid_paths.go

@@ -0,0 +1,134 @@
+/*
+Copyright 2022 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package security
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+
+	"github.com/onsi/ginkgo/v2"
+
+	"k8s.io/ingress-nginx/test/e2e/framework"
+)
+
+const (
+	validPath   = "/xpto/~user/t-e_st.exe"
+	invalidPath = "/foo/bar/;xpto"
+	regexPath   = "/foo/bar/(.+)"
+	host        = "securitytest.com"
+)
+
+var (
+	annotationRegex = map[string]string{
+		"nginx.ingress.kubernetes.io/use-regex": "true",
+	}
+)
+
+var _ = framework.IngressNginxDescribe("[Security] validate path fields", func() {
+	f := framework.NewDefaultFramework("validate-path")
+
+	ginkgo.BeforeEach(func() {
+		f.NewEchoDeployment()
+	})
+
+	ginkgo.It("should accept an ingress with valid path", func() {
+
+		ing := framework.NewSingleIngress(host, validPath, host, f.Namespace, framework.EchoService, 80, nil)
+
+		f.EnsureIngress(ing)
+
+		f.WaitForNginxServer(host,
+			func(server string) bool {
+				return strings.Contains(server, fmt.Sprintf("server_name %s ;", host))
+			})
+
+		f.HTTPTestClient().
+			GET(validPath).
+			WithHeader("Host", host).
+			Expect().
+			Status(http.StatusOK)
+	})
+
+	ginkgo.It("should drop an ingress with invalid path", func() {
+
+		ing := framework.NewSingleIngress(host, invalidPath, host, f.Namespace, framework.EchoService, 80, nil)
+		f.EnsureIngress(ing)
+
+		f.WaitForNginxServer(host,
+			func(server string) bool {
+				return !strings.Contains(server, fmt.Sprintf("server_name %s ;", host))
+			})
+
+		f.HTTPTestClient().
+			GET(invalidPath).
+			WithHeader("Host", host).
+			Expect().
+			Status(http.StatusNotFound)
+	})
+
+	ginkgo.It("should drop an ingress with regex path and regex disabled", func() {
+
+		ing := framework.NewSingleIngress(host, regexPath, host, f.Namespace, framework.EchoService, 80, nil)
+		f.EnsureIngress(ing)
+
+		f.WaitForNginxServer(host,
+			func(server string) bool {
+				return !strings.Contains(server, fmt.Sprintf("server_name %s ;", host))
+			})
+
+		f.HTTPTestClient().
+			GET("/foo/bar/lalala").
+			WithHeader("Host", host).
+			Expect().
+			Status(http.StatusNotFound)
+	})
+
+	ginkgo.It("should accept an ingress with regex path and regex enabled", func() {
+
+		ing := framework.NewSingleIngress(host, regexPath, host, f.Namespace, framework.EchoService, 80, annotationRegex)
+		f.EnsureIngress(ing)
+
+		f.WaitForNginxServer(host,
+			func(server string) bool {
+				return strings.Contains(server, fmt.Sprintf("server_name %s ;", host))
+			})
+
+		f.HTTPTestClient().
+			GET("/foo/bar/lalala").
+			WithHeader("Host", host).
+			Expect().
+			Status(http.StatusOK)
+	})
+
+	ginkgo.It("should reject an ingress with invalid path and regex enabled", func() {
+
+		ing := framework.NewSingleIngress(host, invalidPath, host, f.Namespace, framework.EchoService, 80, annotationRegex)
+		f.EnsureIngress(ing)
+
+		f.WaitForNginxServer(host,
+			func(server string) bool {
+				return !strings.Contains(server, fmt.Sprintf("server_name %s ;", host))
+			})
+
+		f.HTTPTestClient().
+			GET(invalidPath).
+			WithHeader("Host", host).
+			Expect().
+			Status(http.StatusNotFound)
+	})
+})