[Cronet] Public key pinning for Java API

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

Index: components/cronet/android/api/src/org/chromium/net/CronetEngine.java
diff --git a/components/cronet/android/api/src/org/chromium/net/CronetEngine.java b/components/cronet/android/api/src/org/chromium/net/CronetEngine.java
index 4dc237107f3c10e06d670922715f67cdcbb5c3fd..ff6b7404e713d668cfc64cb9b9e6888676358844 100644
--- a/components/cronet/android/api/src/org/chromium/net/CronetEngine.java
+++ b/components/cronet/android/api/src/org/chromium/net/CronetEngine.java
@@ -6,6 +6,7 @@ package org.chromium.net;
 
 import android.content.Context;
 import android.support.annotation.IntDef;
+import android.util.Base64;
 import android.util.Log;
 
 import org.json.JSONArray;
@@ -20,8 +21,11 @@ import java.net.Proxy;
 import java.net.URL;
 import java.net.URLConnection;
 import java.net.URLStreamHandlerFactory;
+import java.util.Collection;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 import java.util.concurrent.Executor;
 
 /**
@@ -301,6 +305,67 @@ public abstract class CronetEngine {
         }
 
         /**
+         * Adds public key pinning for a given host.
+         *
+         * @param hostName name of the host, which public keys should be pinned.

[pauljensen, 2015/11/03 19:59:30]

either change "which" to "to which" or change "pinned" to "pinned to"

[kapishnikov, 2015/11/03 23:58:16]

Done.

+         * @param pinsSha256 a collection of SHA-256 pins.

[pauljensen, 2015/11/03 19:59:30]

I'm not well versed in key pinning, but can we elaborate on what the hash is of?
 is it a hash of the whole certificate? or is it the hash code from inside the
certificate?

[kapishnikov, 2015/11/03 23:58:16]

Done.

[kapishnikov, 2015/11/03 23:58:16]

Done.

+         * @param includeSubdomains indicates whether the pinning policy should be applied to
+         *                          subdomains of the host's domain name.

[pauljensen, 2015/11/03 19:59:30]

"the host's domain name"->"{@code hostName}"

[kapishnikov, 2015/11/03 23:58:16]

Done.

+         * @return the builder to facilitate chaining.
+         * @throws NullPointerException if one of the input parameters is null.
+         * @throws IllegalArgumentException if the provided collection of pins is invalid.

[pauljensen, 2015/11/03 19:59:30]

can you elaborate on what "invalid" means.  You mean if they do not represent a
valid SHA-256 hash code?

[kapishnikov, 2015/11/03 23:58:16]

Done.

+         */
+        public Builder addPublicKeyPins(
+                String hostName, Collection<byte[]> pinsSha256, boolean includeSubdomains) {
+            // Validate the input
+            if (hostName == null) {
+                throw new NullPointerException("The hostname cannot be null");
+            }
+            if (pinsSha256 == null) {
+                throw new NullPointerException("The collection of SHA256 pins cannot be null");
+            }
+            try {
+                // Add HPKP_LIST json array element if it is not present
+                JSONArray hpkpList = mConfig.optJSONArray(CronetEngineBuilderList.HPKP_LIST);
+                if (hpkpList == null) {
+                    hpkpList = new JSONArray();
+                    mConfig.put(CronetEngineBuilderList.HPKP_LIST, hpkpList);
+                }
+
+                // Convert the pin to BASE64 encoding.
+                Set<String> hashes = new HashSet<>(pinsSha256.size());
+                for (byte[] pinSha256 : pinsSha256) {
+                    hashes.add(convertSha256ToBase64WithPrefix(pinSha256));
+                }
+
+                // Add new element to HPKP_LIST json array
+                JSONObject hpkp = new JSONObject();
+                hpkp.put(CronetEngineBuilderList.HPKP_HOST, hostName);
+                hpkp.put(CronetEngineBuilderList.HPKP_PIN_HASHES, new JSONArray(hashes));
+                hpkp.put(CronetEngineBuilderList.HPKP_INCLUDE_SUBDOMAINS, includeSubdomains);
+                hpkpList.put(hpkp);
+            } catch (JSONException e) {
+                Log.e(TAG, "Unable to add public key pins", e);
+            }
+            return this;
+        }
+
+        /**
+         * Converts a given SHA256 array of bytes to BASE64 encoding with the prefix. The format
+         * corresponds to the format that is expected by net::HashValue class.
+         *
+         * @param sha256 SHA256 bytes to convert to BASE64.
+         * @return the BASE64 conversion.
+         * @throws IllegalArgumentException if the provided pin is invalid.
+         */
+        private String convertSha256ToBase64WithPrefix(byte[] sha256) {
+            if (sha256 == null || sha256.length != 32) {
+                throw new IllegalArgumentException("The provided pin is invalid");
+            }
+            return "sha256/" + Base64.encodeToString(sha256, Base64.NO_WRAP);
+        }
+
+        /**
          * Sets experimental QUIC connection options, overwriting any pre-existing
          * options. List of options is subject to change.
          *