Tag Archives: android p

DNS over TLS support in Android P Developer Preview

Posted by Erik Kline, Android software engineer, and Ben Schwartz, Jigsaw software engineer

The first step of almost every connection on the internet is a DNS query. A client, such as a smartphone, typically uses a DNS server provided by the Wi-Fi or cellular network. The client asks this DNS server to convert a domain name, like www.google.com, into an IP address, like 2607:f8b0:4006:80e::2004. Once the client has the IP address, it can connect to its intended destination.

When the DNS protocol was designed in the 1980s, the internet was a much smaller, simpler place. For the past few years, the Internet Engineering Task Force (IETF) has worked to define a new DNS protocol that provides users with the latest protections for security and privacy. The protocol is called "DNS over TLS" (standardized as RFC 7858).

Like HTTPS, DNS over TLS uses the TLS protocol to establish a secure channel to the server. Once the secure channel is established, DNS queries and responses can't be read or modified by anyone else who might be monitoring the connection. (The secure channel only applies to DNS, so it can't protect users from other kinds of security and privacy violations.)

DNS over TLS in P

The Android P Developer Preview includes built-in support for DNS over TLS. We added a Private DNS mode to the Network & internet settings.

By default, devices automatically upgrade to DNS over TLS if a network's DNS server supports it. But users who don't want to use DNS over TLS can turn it off.

Users can enter a hostname if they want to use a private DNS provider. Android then sends all DNS queries over a secure channel to this server or marks the network as "No internet access" if it can't reach the server. (For testing purposes, see this community-maintained list of compatible servers.)

DNS over TLS mode automatically secures the DNS queries from all apps on the system. However, apps that perform their own DNS queries, instead of using the system's APIs, must ensure that they do not send insecure DNS queries when the system has a secure connection. Apps can get this information using a new API: LinkProperties.isPrivateDnsActive().

With the Android P Developer Preview, we're proud to present built-in support for DNS over TLS. In the future, we hope that all operating systems will include secure transports for DNS, to provide better protection and privacy for all users on every new connection.

Protecting users with TLS by default in Android P

Posted by Chad Brubaker, Senior Software Engineer Android Security

Android is committed to keeping users, their devices, and their data safe. One of the ways that we keep data safe is by protecting all data that enters or leaves an Android device with Transport Layer Security (TLS) in transit. As we announced in our Android P developer preview, we're further improving these protections by preventing apps that target Android P from allowing unencrypted connections by default.

This follows a variety of changes we've made over the years to better protect Android users.To prevent accidental unencrypted connections, we introduced the android:usesCleartextTraffic manifest attribute in Android Marshmallow. In Android Nougat, we extended that attribute by creating the Network Security Config feature, which allows apps to indicate that they do not intend to send network traffic without encryption. In Android Nougat and Oreo, we still allowed cleartext connections.

How do I update my app?

If your app uses TLS for all connections then you have nothing to do. If not, update your app to use TLS to encrypt all connections. If you still need to make cleartext connections, keep reading for some best practices.

Why should I use TLS?

Android considers all networks potentially hostile and so encrypting traffic should be used at all times, for all connections. Mobile devices are especially at risk because they regularly connect to many different networks, such as the Wi-Fi at a coffee shop.

All traffic should be encrypted, regardless of content, as any unencrypted connections can be used to inject content, increase attack surface for potentially vulnerable client code, or track the user. For more information, see our past blog post and Developer Summit talk.

Isn't TLS slow?

No, it's not.

How do I use TLS in my app?

Once your server supports TLS, simply change the URLs in your app and server responses from http:// to https://. Your HTTP stack handles the TLS handshake without any more work.

If you are making sockets yourself, use an SSLSocketFactory instead of a SocketFactory. Take extra care to use the socket correctly as SSLSocket doesn't perform hostname verification. Your app needs to do its own hostname verification, preferably by calling getDefaultHostnameVerifier() with the expected hostname. Further, beware that HostnameVerifier.verify() doesn't throw an exception on error but instead returns a boolean result that you must explicitly check.

I need to use cleartext traffic to...

While you should use TLS for all connections, it's possibly that you need to use cleartext traffic for legacy reasons, such as connecting to some servers. To do this, change your app's network security config to allow those connections.

We've included a couple example configurations. See the network security config documentation for a bit more help.

Allow cleartext connections to a specific domain

If you need to allow connections to a specific domain or set of domains, you can use the following config as a guide:

<network-security-config>
    <domain-config cleartextTrafficPermitted="true">
        <domain includeSubdomains="true">insecure.example.com</domain>
        <domain includeSubdomains="true">insecure.cdn.example.com</domain>
    </domain-config>
</network-security-config>

Allow connections to arbitrary insecure domains

If your app supports opening arbitrary content from URLs over insecure connections, you should disable cleartext connections to your own services while supporting cleartext connections to arbitrary hosts. Keep in mind that you should be cautious about the data received over insecure connections as it could have been tampered with in transit.

<network-security-config>
    <domain-config cleartextTrafficPermitted="false">
        <domain includeSubdomains="true">example.com</domain>
        <domain includeSubdomains="true">cdn.example2.com</domain>
    </domain-config>
    <base-config cleartextTrafficPermitted="true" />
</network-security-config>

How do I update my library?

If your library directly creates secure/insecure connections, make sure that it honors the app's cleartext settings by checking isCleartextTrafficPermitted before opening any cleartext connection.

Cryptography Changes in Android P

Posted by Adam Vartanian, Software Engineer

We hope you're enjoying the first developer preview of Android P. We wanted to specifically call out some backward-incompatible changes we plan to make to the cryptographic capabilities in Android P, which you can see in the developer preview.

Changes to providers

Starting in Android P, we plan to deprecate some functionality from the BC provider that's duplicated by the AndroidOpenSSL (also known as Conscrypt) provider. This will only affect applications that specify the BC provider explicitly when calling getInstance() methods. To be clear, we aren't doing this because we are concerned about the security of the implementations from the BC provider, rather because having duplicated functionality imposes additional costs and risks while not providing much benefit.

If you don't specify a provider in your getInstance() calls, no changes are required.

If you specify the provider by name or by instance—for example, Cipher.getInstance("AES/CBC/PKCS7PADDING", "BC") or Cipher.getInstance("AES/CBC/PKCS7PADDING", Security.getProvider("BC"))—the behavior you get in Android P will depend on what API level your application targets. For apps targeting an API level before P, the call will return the BC implementation and log a warning in the application log. For apps targeting Android P or later, the call will throw NoSuchAlgorithmException.

To resolve this, you should stop specifying a provider and use the default implementation.

In a later Android release, we plan to remove the deprecated functionality from the BC provider entirely. Once removed, any call that requests that functionality from the BC provider (whether by name or instance) will throw NoSuchAlgorithmException.

Removal of the Crypto provider

In a previous post, we announced that the Crypto provider was deprecated beginning in Android Nougat. Since then, any request for the Crypto provider by an application targeting API 23 (Marshmallow) or before would succeed, but requests by applications targeting API 24 (Nougat) or later would fail. In Android P, we plan to remove the Crypto provider entirely. Once removed, any call to SecureRandom.getInstance("SHA1PRNG", "Crypto") will throw NoSuchProviderException. Please ensure your apps have been updated.