[Cronet] Public key pinning for Java API

components/cronet/android/api/src/org/chromium/net/CronetUtil.java

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+package org.chromium.net;
+
+import java.util.regex.Pattern;
+
+/**
+ * A set of generic utility methods.
+ */
+class CronetUtil {
+    private static final String VALID_IP_EXPR = "^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])"

[mef, 2015/11/09 16:59:28]

I'm very skeptical about this.

[kapishnikov, 2015/11/09 19:14:20]

I can add more tests to
https://codereview.chromium.org/1407263010/patch/160001/170005
The problem is that if we don't validate the host name properly, the C++ side
will silently fail adding the pins without notifying the client. Also, according
to the HPKP spec, the IPv4 addresses should not be pinned which is not obvious.
Should I implement the validation without using the regular expression?

+            + "\\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])$";
+    private static final String VALID_HOST_EXPR = "^(([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\\-]*"
+            + "[a-zA-Z0-9])\\.)*([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\\-]*[a-zA-Z0-9])$";
+    private static final Pattern VALID_IP_PATTERN = Pattern.compile(VALID_IP_EXPR);
+    private static final Pattern VALID_HOST_PATTERN = Pattern.compile(VALID_HOST_EXPR);
+
+    private CronetUtil() {}
+
+    /**
+     * Checks whether a given string that represents a host name is valid.
+     *
+     * @param hostName host name to check.
+     * @return true if the string is a valid host name.
+     */
+    static boolean isValidHostName(String hostName) {
+        return VALID_HOST_PATTERN.matcher(hostName).matches();
+    }
+
+    /**
+     * Checks whether a given string that represents an IPv4 address is valid.
+     *
+     * @param addr IPv4 address to check.
+     * @return true if the string is a valid IPv4 address.
+     */
+    static boolean isValidIPv4(String addr) {
+        return VALID_IP_PATTERN.matcher(addr).matches();
+    }
+}