Tag Archives: Android-Security

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.

Android Security 2017 Year in Review

Originally posted by Dave Kleidermacher, Vice President of Security for Android, Play, ChromeOS, on the Google Security Blog

Our team's goal is simple: secure more than two billion Android devices. It's our entire focus, and we're constantly working to improve our protections to keep users safe.

Today, we're releasing our fourth annual Android security year in review. We compile these reports to help educate the public about the many different layers of Android security, and also to hold ourselves accountable so that anyone can track our security work over time.

We saw some really positive momentum last year and this post includes some, but not nearly all, of the major moments from 2017. To dive into all the details, you can read the full report at: g.co/AndroidSecurityReport2017

Google Play Protect

In May, we announced Google Play Protect, a new home for the suite of Android security services on nearly two billion devices. While many of Play Protect's features had been securing Android devices for years, we wanted to make these more visible to help assure people that our security protections are constantly working to keep them safe.

Play Protect's core objective is to shield users from Potentially Harmful Apps, or PHAs. Every day, it automatically reviews more than 50 billion apps, other potential sources of PHAs, and devices themselves and takes action when it finds any.

Play Protect uses a variety of different tactics to keep users and their data safe, but the impact of machine learning is already quite significant: 60.3% of all Potentially Harmful Apps were detected via machine learning, and we expect this to increase in the future.

Protecting users' devices

Play Protect automatically checks Android devices for PHAs at least once every day, and users can conduct an additional review at any time for some extra peace of mind. These automatic reviews enabled us to remove nearly 39 million PHAs last year.

We also update Play Protect to respond to trends that we detect across the ecosystem. For instance, we recognized that nearly 35% of new PHA installations were occurring when a device was offline or had lost network connectivity. As a result, in October 2017, we enabled offline scanning in Play Protect, and have since prevented 10 million more PHA installs.

Preventing PHA downloads

Devices that downloaded apps exclusively from Google Play were nine times less likely to get a PHA than devices that downloaded apps from other sources. And these security protections continue to improve, partially because of Play Protect's increased visibility into newly submitted apps to Play. It reviewed 65% more Play apps compared to 2016.

Play Protect also doesn't just secure Google Play—it helps protect the broader Android ecosystem as well. Thanks in large part to Play Protect, the installation rates of PHAs from outside of Google Play dropped by more than 60%.

Security updates

While Google Play Protect is a great shield against harmful PHAs, we also partner with device manufacturers to make sure that the version of Android running on user devices is up-to-date and secure.

Throughout the year, we worked to improve the process for releasing security updates, and 30% more devices received security patches than in 2016. Furthermore, no critical security vulnerabilities affecting the Android platform were publicly disclosed without an update or mitigation available for Android devices. This was possible due to the Android Security Rewards Program, enhanced collaboration with the security researcher community, coordination with industry partners, and built-in security features of the Android platform.

New security features in Android Oreo

We introduced a slew of new security features in Android Oreo: making it safer to get apps, dropping insecure network protocols, providing more user control over identifiers, hardening the kernel, and more.

We highlighted many of these over the course of the year, but some may have flown under the radar. For example, we updated the overlay API so that apps can no longer block the entire screen and prevent you from dismissing them, a common tactic employed by ransomware.

Openness makes Android security stronger

We've long said it, but it remains truer than ever: Android's openness helps strengthen our security protections. For years, the Android ecosystem has benefitted from researchers' findings, and 2017 was no different.

Security reward programs

We continued to see great momentum with our Android Security Rewards program: we paid researchers $1.28 million, totalling more than two million dollars since the start of the program. We also increased our top-line payouts for exploits that compromise TrustZone or Verified Boot from $50,000 to $200,000, and remote kernel exploits from $30,000 to $150,000.

In parallel, we also introduced Google Play Security Rewards program and offered a bonus bounty to developers that discover and disclose select critical vulnerabilities in apps hosted on Play to their developers.

External security competitions

Our teams also participated in external vulnerability discovery and disclosure competitions, such as Mobile Pwn2Own. At the 2017 Mobile Pwn2Own competition, no exploits successfully compromised the Google Pixel. And of the exploits demonstrated against devices running Android, none could be reproduced on a device running unmodified Android source code from the Android Open Source Project (AOSP).

We're pleased to see the positive momentum behind Android security, and we'll continue our work to improve our protections this year, and beyond. We will never stop our work to ensure the security of Android users.

Android security to the N-th degree

Posted by Adrian Ludwig, Director, Android Security

Editor's note: Today we share highlights and a few remaining questions from our last security discussion as we ramp up for our next security talk focused on what’s new for work in Android N. Don’t miss that Hangout on Air on August 16 at 9:30am PT. To help guide that discussion, leave whatever questions you’ll have for us then in comments on this post or vote with a “+1” for questions from others you’d like answers to. Join that discussion by registering here.

In April we shared our Android Security 2015 Year in Review report and took a deeper dive into Android security with a live Hangout on Air to discuss the trends and hard data; you can still view the recorded session.

Some interesting highlights from the report include data showing that Android runs more than 400 million automatic security scans per day on devices and this helped limit the number of potentially harmful apps (PHAs) installed to less than 0.15% of devices that only get apps from Google Play. Note that devices that install apps from outside of Google Play are around 10 times more likely to have a PHA. As a follow up, we’re taking some time today to answer a few of the remaining questions from our live Hangout in April.

Will you have a plan to release a security patch via an app, such as WebView, in Play Store instead of a security patch by the manufacturer?

We do think it's possible for more of the framework to be updated by Google directly — there’s some architectural work that we're doing to make this possible in a future release.

Are all Android versions encrypted?

Android has provided full disk encryption since Android 3.0. Users can enable it by going into settings and turning it on. For newer devices, encryption may be turned on by default. And starting with Android M, all new devices that meet a performance requirement (being capable of encrypting over 50MB/S using AES, or the Advanced Encryption Standard) must be encrypted by default. These requirements are described in more detail in the Android Compatibility Definition Documentation (CDD).

Android N is introducing a new feature "Direct Boot" and a file based encryption mechanism that improves usability while maintaining encryption of user data.

Given that Android is making advancements towards the phones being used in enterprise [Android for Work], what are the security improvements that have been made specifically to make the phones more secure for enterprise? What are the security improvements that the team is working on that we will likely see in the near future?

Most of the security improvements that we make in Android have the dual purpose of protecting both enterprise and consumers, but there are some features that are more specific to enterprises. "Profiles," for example, were introduced to make it easy to separate work data from personal data. We've also added APIs so that application developers (including Mobile Device Management vendors or MDMs) can remotely query the state of the device — some more recent examples include the security patch level and adding an API in Google Play Services called SafetyNet.attest that allows an enterprise to confirm that a device is a compatible device.

Verify Apps. As far as I recall it was provided 4 years ago and improved in 2013 with background scanning. What's new now?

We're constantly making improvements to how we identify and protect users from potentially harmful apps. The 2015 year in review describes a number of changes, including the introduction of a technology we call the Anomaly Correlation Engine, advancements in Machine Learning, improvements to our System Integrity Checker, more effective user interface on security warnings and much more.

During next month’s Hangout on Air, we’ll answer your Android security questions and share information on what’s new for work in Android N.

To help kickstart some question ideas, here are just a few of the many new and improved work Android N security features that we’ll discuss:
  • Always on VPN for secure data transmission
  • Passcode enforcement options on individual work apps
  • More granular policies and app permission management
  • QR code provisioning to save time and money on device deployments

So, if like many, you’re wondering if Android could be the right mobile solution for your business, register for our Android N Hangout on Air taking place on August 16 at 9:30am PT.

Protecting against unintentional regressions to cleartext traffic in your Android apps

Posted by Alex Klyubin, Android Security team

When your app communicates with servers using cleartext network traffic, such as HTTP, the traffic risks being eavesdropped upon and tampered with by third parties. This may leak information about your users and open your app up to injection of unauthorized content or exploits. Ideally, your app should use secure traffic only, such as by using HTTPS instead of HTTP. Such traffic is protected against eavesdropping and tampering.

Many Android apps already use secure traffic only. However, some of them occasionally regress to cleartext traffic by accident. For example, an inadvertent change in one of the server components could make the server provide the app with HTTP URLs instead of HTTPS URLs. The app would then proceed to communicate in cleartext, without any user-visible symptoms. This situation may go unnoticed by the app’s developer and users.

Even if you believe your app is only using secure traffic, make sure to use the new mechanisms provided by Android Marshmallow (Android 6.0) to catch and prevent accidental regressions.

New protection mechanisms

For apps which only use secure traffic, Android 6.0 Marshmallow (API Level 23) introduced two mechanisms to address regressions to cleartext traffic: (1) in production / installed base, block cleartext traffic, and (2) during development / QA, log or crash whenever non-TLS/SSL traffic is encountered. The following sections provide more information about these mechanisms.

Block cleartext traffic in production

To protect the installed base of your app against regressions to cleartext traffic, declare android:usesCleartextTraffic=”false” attribute on the application element in your app’s AndroidManifest.xml. This declares that the app is not supposed to use cleartext network traffic and makes the platform network stacks of Android Marshmallow block cleartext traffic in the app. For example, if your app accidentally attempts to sign in the user via a cleartext HTTP request, the request will be blocked and the user’s identity and password will not leak to the network.

You don’t have to set minSdkVersion or targetSdkVersion of your app to 23 (Android Marshmallow) to use android:usesCleartextTraffic. On older platforms, this attribute is simply ignored and thus has no effect.

Please note that WebView does not yet honor this feature.

And under certain circumstances cleartext traffic may still leave or enter the app. For example, Socket API ignores the cleartext policy because it does not know whether the data it transmits or receives can be classified as cleartext. Android platform HTTP stacks, on the other hand, honor the policy because they know whether traffic is cleartext.

Google AdMob is also built to honor this policy. When your app declares that it does not use cleartext traffic, only HTTPS-only ads should be served to the app.

Third-party network, ad, and analytics libraries are encouraged to add support for this policy. They can query the cleartext traffic policy via the NetworkSecurityPolicy class.

Detect cleartext traffic during development

To spot cleartext traffic during development or QA, StrictMode API lets you modify your app to detect non-TLS/SSL traffic and then either log violations to system log or crash the app (see StrictMode.VmPolicy.Builder.detectCleartextNetwork()). This is a useful tool for identifying which bits of the app are using non-TLS/SSL (and DLTS) traffic. Unlike the android:usesCleartextTraffic attribute, this feature is not meant to be enabled in app builds distributed to users.

Firstly, this feature is supposed to flag secure traffic that is not TLS/SSL. More importantly, TLS/SSL traffic via HTTP proxy also may be flagged. This is an issue because as a developer, you have no control over whether a particular user of your app may have configured their Android device to use an HTTP proxy. Finally, the implementation of the feature is not future-proof and thus may reject future TLS/SSL protocol versions. Thus, this feature is intended to be used only during the development and QA phase.

Declare finer-grained cleartext policy in Network Security Config

Android N offers finer-grained control over cleartext traffic policy. As opposed to android:usesCleartextTraffic attribute, which applies to all destinations with which an app communicates, Android N’s Network Security Config lets an app specify cleartext policy for specific destinations. For example, to facilitate a more gradual transition towards a policy that does not allow cleartext traffic, an app can at first block accidental cleartext only for communication with its most important backends and permit cleartext to be used for other destinations.

Next steps

It is a security best practice to only use secure network traffic for communication between your app and its servers. Android Marshmallow enables you to enforce this practice, so give it a try!

As always, we appreciate feedback and welcome suggestions for improving Android. Contact us at [email protected]. HTTPS, Android-Security