page.title=Network Security Configuration
page.keywords=security,network,config
page.metaDescription=Feature that allows app developers to customize network security settings in a safe configuration file.
page.image=images/cards/card-nyc_2x.jpg
@jd:body
<div id="tb-wrapper">
<div id="tb">
<h2>In this document</h2>
<ol>
<li><a href="#manifest">Adding a Security Configuration File</a></li>
<li><a href="#CustomTrust">Customizing Trusted CAs</a>
<ol>
<li><a href="#ConfigCustom">Configuring a Trusted Custom CA</a></li>
<li><a href="#LimitingCas">Limiting the Set of Trusted CAs</a></li>
<li><a href="#TrustingAdditionalCas">Trusting Additional CAs</a></li>
</ol>
</li>
<li><a href="#TrustingDebugCa">Debugging-only CAs</a></li>
<li><a href="#CleartextTrafficPermitted">Opting Out of Cleartext Traffic</a></li>
<li><a href="#CertificatePinning">Pinning Certificates</a></li>
<li><a href="#ConfigInheritance">Configuration Inheritance Behavior</a></li>
<li><a href="#FileFormat">Configuration File Format</a></li>
</ol>
</div>
</div>
<p>
The Network Security Configuration feature lets apps customize their network
security settings in a safe, declarative configuration file without modifying
app code. These settings can be configured for specific domains and for a
specific app. The key capabilities of this feature are as follows:
</p>
<ul>
<li>
<b>Custom trust anchors:</b> Customize which Certificate Authorities (CA)
are trusted for an app's secure connections. For
example, trusting particular self-signed certificates or restricting the
set of public CAs that the app trusts.
</li>
<li>
<b>Debug-only overrides:</b> Safely debug secure connections in an app
without added risk to the installed base.
</li>
<li>
<b>Cleartext traffic opt-out:</b> Protect apps from
accidental usage of cleartext traffic.
</li>
<li>
<b>Certificate pinning:</b> Restrict an app's secure connection to
particular certificates.
</li>
</ul>
<h2 id="manifest">Adding a Security Configuration File</h2>
<p>
The Network Security Configuration feature uses an XML file where you specify
the settings for your app. You must include an entry in the manifest of your
app to point to this file. The following code excerpt from a manifest
demonstrates how to create this entry:
</p>
<pre>
<?xml version="1.0" encoding="utf-8"?>
<manifest ... >
<application android:networkSecurityConfig="@xml/network_security_config"
... >
...
</application>
</manifest>
</pre>
<h2 id="CustomTrust">Customizing Trusted CAs</h2>
<p>
An app may want to trust a custom set of CAs instead of the platform
default. The most common reasons of this are:
</p>
<ul>
<li>Connecting to a host with a custom certificate authority, such as a
CA that is self-signed or is issued internally within a company.
</li>
<li>Limiting the set of CAs to only the CAs you trust instead of every
pre-installed CA.
</li>
<li>Trusting additional CAs not included in the system.
</li>
</ul>
<p>
By default, secure connections (using protocols like TLS and HTTPS) from all
apps trust the pre-installed system CAs, and apps targeting Android 6.0 (API
level 23) and lower also trust the user-added CA store by default. An app can
customize its own connections using {@code base-config} (for app-wide
customization) or {@code domain-config} (for per-domain customization).
</p>
<h3 id="ConfigCustom">Configuring a Custom CA</h3>
<p>
Assume you want to connect to your host which uses a self-signed SSL
certificate or to a host whose SSL certificate is issued by a non-public CA
which you trust, such as your company's internal CA.
</p>
<p>
<code>res/xml/network_security_config.xml</code>:
<pre>
<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
<domain-config>
<domain includeSubdomains="true">example.com</domain>
<trust-anchors>
<certificates src="@raw/my_ca"/>
</trust-anchors>
</domain-config>
</network-security-config>
</pre>
</p>
<p>
Add the self-signed or non-public CA certificate, in PEM or DER format, to
{@code res/raw/my_ca}.
</p>
<h3 id="LimitingCas">Limiting the Set of Trusted CAs</h3>
<p>
An app that does not want to trust all CAs trusted by system can
instead specify its own reduced set of CAs to trust. This protects the
app from fradulent certificates issued by any of the other CAs.
</p>
<p>
The configuration to limit the set of trusted CAs is similar to <a href=
"#ConfigCustom">trusting a custom CA</a> for a specific domain except
that multiple CAs are provided in the resource.
</p>
<p>
<code>res/xml/network_security_config.xml</code>:
<pre>
<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
<domain-config>
<domain includeSubdomains="true">secure.example.com</domain>
<domain includeSubdomains="true">cdn.example.com</domain>
<trust-anchors>
<certificates src="@raw/trusted_roots"/>
</trust-anchors>
</domain-config>
</network-security-config>
</pre>
</p>
<p>
Add the trusted CAs, in PEM or DER format, to {@code res/raw/trusted_roots}.
Note that if using PEM format the file must contain <em>only</em> PEM data
and no extra text. You can also provide multiple
<a href="#certificates"><code><certificates></code></a>
elements instead of one.
</p>
<h3 id="TrustingAdditionalCas">
Trusting Additional CAs
</h3>
<p>
An app may want to trust additional CAs not trusted by the system,
this could be due to the system not yet including the CA or a CA that does
not meet the requirements for inclusion into the Android system. An
app can do this by specifying multiple certificate sources for a
configuration.
</p>
<p>
<code>res/xml/network_security_config.xml</code>:
<pre>
<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
<base-config>
<trust-anchors>
<certificates src="@raw/extracas"/>
<certificates src="system"/>
</trust-anchors>
</base-config>
</network-security-config>
</pre>
</p>
<h2 id="TrustingDebugCa">Configuring CAs for Debugging</h2>
<p>
When debugging an app that connects over HTTPS, you may want to
connect to a local development server, which does not have the SSL
certificate for your production server. In order to support this without any
modification to your app's code, you can specify debug-only CAs, which
are trusted <i>only</i> when <a href=
"{@docRoot}guide/topics/manifest/application-element.html#debug">
android:debuggable</a>
is {@code true}, by using {@code debug-overrides}. Normally, IDEs and build
tools set this flag automatically for non-release builds.
</p>
<p>
This is safer than the usual conditional code because, as a security
precaution, app stores do not accept apps which are marked
debuggable.
</p>
<p>
<code>res/xml/network_security_config.xml</code>:
<pre>
<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
<debug-overrides>
<trust-anchors>
<certificates src="@raw/debug_cas"/>
</trust-anchors>
</debug-overrides>
</network-security-config>
</pre>
</p>
<h2 id="CleartextTrafficPermitted">Opting Out of Cleartext Traffic</h2>
<p>
Applications intending to connect to destinations using only secure
connections can opt-out of supporting cleartext (using the unencrypted HTTP
protocol instead of HTTPS) to those destinations. This option helps prevent
accidental regressions in apps due to changes in URLs provided by external
sources such as backend servers.
See {@link android.security.NetworkSecurityPolicy#isCleartextTrafficPermitted
NetworkSecurityPolicy.isCleartextTrafficPermitted()} for more details.
</p>
<p>
For example, an app may want to ensure that all connections to {@code
secure.example.com} are always done over HTTPS to protect sensitive traffic
from hostile networks.
</p>
<p>
<code>res/xml/network_security_config.xml</code>:
<pre>
<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
<domain-config cleartextTrafficPermitted="false">
<domain includeSubdomains="true">secure.example.com</domain>
</domain-config>
</network-security-config>
</pre>
</p>
<h2 id="CertificatePinning">Pinning Certificates</h2>
<p>
Normally, an app trusts all pre-installed CAs. If any of these CAs were to
issue a fradulent certificate, the app would be at risk from a
man-in-the-middle attack. Some apps choose to limit the set of certificates
they accept by either limiting the set of CAs they trust or by certificate
pinning.
</p>
<p>
Certificate pinning is done by providing a set of certificates by hash of the
public key (<code>SubjectPublicKeyInfo</code> of the X.509 certificate). A
certificate chain is then valid only if the certificate chain contains at
least one of the pinned public keys.
</p>
<p>
Note that, when using certificate pinning, you should always include a backup
key so that if you are forced to switch to new keys or change CAs (when
pinning to a CA certificate or an intermediate of that CA), your
app's connectivity is unaffected. Otherwise, you must push out
an update to the app to restore connectivity.
</p>
<p>
Additionally, it is possible to set an expiration time for pins after which
pinning is not performed. This helps prevent connectivity issues in
apps which have not been updated. However, setting an expiration time
on pins may enable pinning bypass.
</p>
<p>
<code>res/xml/network_security_config.xml</code>:
<pre>
<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
<domain-config>
<domain includeSubdomains="true">example.com</domain>
<pin-set expiration="2018-01-01">
<pin digest="SHA-256">7HIpactkIAq2Y49orFOOQKurWxmmSFZhBCoQYcRhJ3Y=</pin>
<!-- backup pin -->
<pin digest="SHA-256">fwza0LRMXouZHRC8Ei+4PyuldPDcf3UKgO/04cDM1oE=</pin>
</pin-set>
</domain-config>
</network-security-config>
</pre>
</p>
<h2 id="ConfigInheritance">Configuration Inheritance Behavior</h2>
<p>
Values not set in a specific configuration are inherited. This behavior allows
more complex configurations while keeping the configuration file readable.
</p>
<p>
If a value is not set in a specific entry, then the value from the more
general entry is used. For example, values not set in a {@code domain-config}
are taken from the parent {@code domain-config}, if nested, or from the {@code
base-config} if not. Values not set in the {@code base-config} use the
platform default values.
</p>
<p>
For example, consider where all connections to subdomains of {@code
example.com} must use a custom set of CAs. Additonally, cleartext traffic to
these domains is permitted <em>except</em> when connecting to {@code
secure.example.com}. By nesting the configuration for {@code
secure.example.com} inside the configuration for {@code example.com}, the
{@code trust-anchors} does not need to be duplicated.
</p>
<p>
<code>res/xml/network_security_config.xml</code>:
<pre>
<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
<domain-config>
<domain includeSubdomains="true">example.com</domain>
<trust-anchors>
<certificates src="@raw/my_ca"/>
</trust-anchors>
<domain-config cleartextTrafficPermitted="false">
<domain includeSubdomains="true">secure.example.com</domain>
</domain-config>
</domain-config>
</network-security-config>
</pre>
</p>
<h2 id="FileFormat">Configuration File Format</h2>
<p>
The Network Security Configuration feature uses an XML file format.
The overall structure of the file is shown in the following code sample:
</p>
<pre>
<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
<base-config>
<trust-anchors>
<certificates src="..."/>
...
</trust-anchors>
</base-config>
<domain-config>
<domain>android.com</domain>
...
<trust-anchors>
<certificates src="..."/>
...
</trust-anchors>
<pin-set>
<pin digest="...">...</pin>
...
</pin-set>
</domain-config>
...
<debug-overrides>
<trust-anchors>
<certificates src="..."/>
...
</trust-anchors>
</debug-overrides>
</network-security-config>
</pre>
<p>
The following sections describe the syntax and other details of the file
format.
</p>
<h3 id="network-security-config">
<network-security-config>
</h3>
<dl class="xml">
<dt>
can contain:
</dt>
<dd>
0 or 1 of <code><a href="#base-config"><base-config></a></code><br>
Any number of <code><a href=
"#domain-config"><domain-config></a></code><br>
0 or 1 of <code><a href="#debug-overrides"><debug-overrides></a></code>
</dd>
</dl>
<h3 id="base-config">
<base-config>
</h3>
<dl class="xml">
<dt>
syntax:
</dt>
</dl>
<pre class="stx">
<base-config <a href=
"#CleartextTrafficPermitted">cleartextTrafficPermitted</a>=["true" | "false"]>
...
</base-config>
</pre>
<dl class="xml">
<dt>
can contain:
</dt>
<dd>
<code><a href="#trust-anchors"><trust-anchors></a></code>
</dd>
<dt>
description:
</dt>
<dd>
The default configuration used by all connections whose destination is not
covered by a <a href="#domain-config"><code>domain-config</code></a>.
<p>
Any values that are not set use the platform default values. The default
configuration for apps targeting Android 7.0 (API level 24) and higher is as
follows:
</p>
<pre>
<base-config cleartextTrafficPermitted="true">
<trust-anchors>
<certificates src="system" />
</trust-anchors>
</base-config>
</pre>
The default configuration for apps targeting Android 6.0 (API level 23) and
lower is as follows:
<pre>
<base-config cleartextTrafficPermitted="true">
<trust-anchors>
<certificates src="system" />
<certificates src="user" />
</trust-anchors>
</base-config>
</pre>
</dd>
</dl>
<h3 id="domain-config"><domain-config></h3>
<dl class="xml">
<dt>syntax:</dt>
<dd>
<pre class="stx"><domain-config <a href="#CleartextTrafficPermitted">cleartextTrafficPermitted</a>=["true" | "false"]>
...
</domain-config></pre>
</dd>
<dt>Can Contain:</dt>
<dd>
1 or more <code><a href="#domain"><domain></a></code>
<br/>0 or 1 <code><a href="#trust-anchors"><trust-anchors></a></code>
<br/>0 or 1 <code><a href="#pin-set"><pin-set></code></a>
<br/>Any number of nested <code><domain-config></code></dd>
<dt>Description</dt>
<dd>Configuration used for connections to specific destinations, as defined by
the {@code domain} elements.
<p>Note that if multiple {@code domain-config} elements cover a destination, the
configuration with the most specific (longest) matching domain rule is
used.</p></dd>
</dl>
<h3 id="domain"><domain></h3>
<dl class="xml">
<dt>
syntax:
</dt>
<dd>
<pre class="stx">
<domain includeSubdomains=["true" | "false"]>example.com</domain>
</pre>
</dd>
<dt>
Attributes:
</dt>
<dd>
<dl class="attr">
<dt>
{@code includeSubdomains}
</dt>
<dd>
If {@code "true"}, then this domain rule matches the domain and all
subdomains, including subdomains of subdomains. Otherwise, the rule only
applies to exact matches.
</dd>
</dl>
</dd>
<dt>
Description:
</dt>
</dl>
<h3 id="debug-overrides"><debug-overrides></h3>
<dl class="xml">
<dt>
syntax:
</dt>
<dd>
<pre class="stx">
<debug-overrides>
...
</debug-overrides>
</pre>
</dd>
<dt>
Can Contain:
</dt>
<dd>
0 or 1 <code><a href="#trust-anchors"><trust-anchors></a></code>
</dd>
<dt>
Description:
</dt>
<dd>
Overrides to be applied when <a href=
"{@docRoot}guide/topics/manifest/application-element.html#debug">android:debuggable</a>
is {@code "true"}, which is normally the case for non-release builds
generated by IDEs and build tools. Trust anchors specified in {@code
debug-overrides} are added to all other configurations, and certificate
pinning is not performed when the server's certificate chain uses one of
these debug-only trust anchors. If <a href=
"{@docRoot}guide/topics/manifest/application-element.html#debug">android:debuggable</a>
is {@code "false"}, then this section is completely ignored.
</dd>
</dl>
<h3 id="trust-anchors"><trust-anchors></h3>
<dl class="xml">
<dt>
syntax:
</dt>
<dd>
<pre class="stx">
<trust-anchors>
...
</trust-anchors>
</pre>
</dd>
<dt>
Can Contain:
</dt>
<dd>
Any number of <code><a href="#certificates"><certificates></a></code>
</dd>
<dt>
Description:
</dt>
<dd>
Set of trust anchors for secure connections.
</dd>
</dl>
<h3 id="certificates"><certificates></h3>
<dl class="xml">
<dt>syntax:</dt>
<dd><pre class="stx"><certificates src=["system" | "user" | "<i>raw resource</i>"]
overridePins=["true" | "false"] />
</pre></dd>
<dt>description:</dt>
<dd>Set of X.509 certificates for {@code trust-anchors} elements.</dd>
<dt>attributes:</dt>
<dd><dl class="attr">
<dt>{@code src}</dt>
<dd>
The source of CA certificates. Each certificate can be one of the following:
<ul>
<li>a raw resource ID pointing to a file containing X.509 certificates.
Certificates must be encoded in DER or PEM format. In the case of PEM
certificates, the file <em>must not</em> contain extra non-PEM data such as
comments.
</li>
<li>{@code "system"} for the pre-installed system CA certificates
</li>
<li>{@code "user"} for user-added CA certificates
</li>
</ul>
</dd>
<dt>{@code overridePins}</dt>
<dd>
<p>
Specifies if the CAs from this source bypass certificate pinning. If {@code
"true"}, then pinning is not performed on certificate chains which are
signed by one of the CAs from this source. This can be useful for debugging
CAs or for testing man-in-the-middle attacks on your app's secure traffic.
</p>
<p>
Default is {@code "false"} unless specified in a {@code debug-overrides}
element, in which case the default is {@code "true"}.
</p>
</dd>
</dl>
</dd>
<h3 id="pin-set"><pin-set></h3>
<dl class="xml">
<dt>
syntax:
</dt>
<dd>
<pre class="stx">
<pin-set expiration="date">
...
</pin-set>
</pre>
</dd>
<dt>
Can Contain:
</dt>
<dd>
Any number of <code><a href="#pin"><pin></a></code>
</dd>
<dt>
Description:
</dt>
<dd>
A set of public key pins. For a secure connection to be trusted, one of the
public keys in the chain of trust must be in the set of pins. See
<code><a href="#pin"><pin></a></code> for the format of pins.
</dd>
<dt>
Attributes:
</dt>
<dd>
<dl class="attr">
<dt>
{@code expiration}
</dt>
<dd>
The date, in {@code yyyy-MM-dd} format, on which the pins expire, thus
disabling pinning. If the attribute is not set, then the pins do not
expire.
<p>
Expiration helps prevent connectivity issues in apps which do not get
updates to their pin set, such as when the user disables app updates.
</p>
</dd>
</dl>
</dd>
</dl>
<h3 id="pin"><pin></h3>
<dl class="xml">
<dt>
syntax:
</dt>
<dd>
<pre class="stx">
<pin digest=["SHA-256"]>base64 encoded digest of X.509
SubjectPublicKeyInfo (SPKI)</pin>
</pre>
</dd>
<dt>
Attributes:
</dt>
<dd>
<dl class="attr">
<dt>
{@code digest}
</dt>
<dd>
The digest algorithm used to generate the pin. Currently, only
{@code "SHA-256"} is supported.
</dd>
</dl>
</dd>
</dl>