Implement object deep inspector (#8456)

internal/ingress/inspector/rules.go

@@ -0,0 +1,53 @@
+/*
+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 inspector
+
+import (
+	"fmt"
+	"regexp"
+)
+
+var (
+	invalidAliasDirective = regexp.MustCompile(`\s*alias\s*.*;`)
+	invalidRootDirective  = regexp.MustCompile(`\s*root\s*.*;`)
+	invalidEtcDir         = regexp.MustCompile(`/etc/(passwd|shadow|group|nginx|ingress-controller)`)
+	invalidSecretsDir     = regexp.MustCompile(`/var/run/secrets`)
+	invalidByLuaDirective = regexp.MustCompile(`.*_by_lua.*`)
+
+	invalidRegex = []regexp.Regexp{}
+)
+
+func init() {
+	invalidRegex = []regexp.Regexp{
+		*invalidAliasDirective,
+		*invalidRootDirective,
+		*invalidEtcDir,
+		*invalidSecretsDir,
+		*invalidByLuaDirective,
+	}
+}
+
+// CheckRegex receives a value/configuration and validates if it matches with one of the
+// forbidden regexes.
+func CheckRegex(value string) error {
+	for _, regex := range invalidRegex {
+		if regex.MatchString(value) {
+			return fmt.Errorf("invalid value found: %s", value)
+		}
+	}
+	return nil
+}