[Cronet] Public key pinning for Java API

components/cronet/android/api/src/org/chromium/net/CronetEngine.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 android.content.Context;
 import android.support.annotation.IntDef;
+import android.util.Base64;
 import android.util.Log;
 
 import org.json.JSONArray;
 import org.json.JSONException;
 import org.json.JSONObject;
 
 import java.io.File;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.reflect.Constructor;
 import java.net.Proxy;
 import java.net.URL;
 import java.net.URLConnection;
 import java.net.URLStreamHandlerFactory;
+import java.util.Collection;
+import java.util.Date;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 import java.util.concurrent.Executor;
 
 /**
  * An engine to process {@link UrlRequest}s, which uses the best HTTP stack
  * available on the current platform.
  */
 public abstract class CronetEngine {
     /**
      * A builder for {@link CronetEngine}s, which allows runtime configuration of
      * {@code CronetEngine}. Configuration options are set on the builder and
@@ skipping 261 matching lines @@
                 hint.put(CronetEngineBuilderList.QUIC_HINT_PORT, port);
                 hint.put(CronetEngineBuilderList.QUIC_HINT_ALT_PORT, alternatePort);
                 quicHints.put(hint);
             } catch (JSONException e) {
                 // Intentionally do nothing.
             }
             return this;
         }
 
         /**
+         * Adds public key pins for a given host.
+         *
+         * @param hostName name of the host to which public keys should be pinned.
+         * @param pinsSha256 a collection of pins. Each pin is the SHA-256 cryptographic
+         *                   hash of DER-encoded ASN.1 representation of Subject Public
+         *                   Key Info (SPKI) of the host X.509 certificate. Use
+         *                   {@link java.security.cert.Certificate#getPublicKey()
+         *                   Certificate.getPublicKey} and
+         *                   {@link java.security.Key#getEncoded() Key.getEncoded}
+         *                   to obtain DER-encoded ASN.1 representation of SPKI.
+         * @param includeSubdomains indicates whether the pinning policy should be applied to
+         *                          subdomains of {@code hostName}.
+         * @param expirationDate specifies the expiration date for the pins.
+         * @return the builder to facilitate chaining.
+         * @throws NullPointerException if one of the input parameters is null.
+         * @throws IllegalArgumentException if the given host name is invalid or the
+         *                                  {@code pinsSha256} collection contains a byte array
+         *                                  that does not represent a valid SHA-256 hash.
+         */
+        public Builder addPublicKeyPins(String hostName, Collection<byte[]> pinsSha256,
+                boolean includeSubdomains, Date expirationDate) {
+            if (hostName == null) {
+                throw new NullPointerException("The hostname cannot be null");
+            }
+            if (!isValidHostNameForPinning(hostName)) {
+                throw new IllegalArgumentException("Invalid host name: " + hostName);
+            }
+            if (pinsSha256 == null) {
+                throw new NullPointerException("The collection of SHA256 pins cannot be null");
+            }
+            try {
+                // Add PKP_LIST JSON array element if it is not present.
+                JSONArray pkpList = mConfig.optJSONArray(CronetEngineBuilderList.PKP_LIST);
+                if (pkpList == null) {
+                    pkpList = new JSONArray();
+                    mConfig.put(CronetEngineBuilderList.PKP_LIST, pkpList);
+                }
+
+                // 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 PKP_LIST JSON array.
+                JSONObject pkp = new JSONObject();
+                pkp.put(CronetEngineBuilderList.PKP_HOST, hostName);
+                pkp.put(CronetEngineBuilderList.PKP_PIN_HASHES, new JSONArray(hashes));
+                pkp.put(CronetEngineBuilderList.PKP_INCLUDE_SUBDOMAINS, includeSubdomains);
+                // The expiration time is passed as a double, in seconds since January 1, 1970.
+                pkp.put(CronetEngineBuilderList.PKP_EXPIRATION_DATE,
+                        (double) expirationDate.getTime() / 1000);
+                pkpList.put(pkp);
+            } catch (JSONException e) {
+                // This exception should never happen.
+                throw new RuntimeException(
+                        "Failed to add pubic key pins with the given arguments", e);
+            }
+            return this;
+        }
+
+        /**
+         * Converts a given SHA256 array of bytes to BASE64 encoded string and prepends
+         * {@code sha256/} prefix to it. The format corresponds to the format that is expected by
+         * {@code net::HashValue} class.
+         *
+         * @param sha256 SHA256 bytes to convert to BASE64.
+         * @return the BASE64 encoded SHA256 with the prefix.
+         * @throws IllegalArgumentException if the provided pin is invalid.
+         */
+        private static String convertSha256ToBase64WithPrefix(byte[] sha256) {
+            if (sha256 == null || sha256.length != 32) {
+                throw new IllegalArgumentException("Public key pin is invalid");
+            }
+            return "sha256/" + Base64.encodeToString(sha256, Base64.NO_WRAP);
+        }
+
+        /**
+         * Checks whether the given string that represents a host name is valid for PKP.
+         * A valid host name should not match IPv4 address.
+         *
+         * @see <a href="https://tools.ietf.org/html/rfc7469#section-2.3.3>RFC 7469</a>
+         * @param hostName host name to check.
+         * @return true if the string is a valid host name.
+         */
+        private static boolean isValidHostNameForPinning(String hostName) {
+            return CronetUtil.isValidHostName(hostName) && !CronetUtil.isValidIPv4(hostName);

[nharper, 2015/11/19 23:47:54]

This doesn't explicitly check that hostName isn't an IPv6 address (although I
imagine isValidHostName would fail when given an IPv6 address, I can't be sure).

RFC 7469 section 2.3.3 states "Known Pinned Hosts are identified only by domain
names, and never IP addresses."

[kapishnikov, 2015/11/20 16:38:03]

Yes, any IPv6 is not a valid host name and will be rejected. I added IPv6 to the
method description.

+        }
+
+        /**
          * Sets experimental options to be used in Cronet.
          *
          * @param options JSON formatted experimental options.
          * @return the builder to facilitate chaining.
          */
         public Builder setExperimentalOptions(String options) {
             return putString(CronetEngineBuilderList.EXPERIMENTAL_OPTIONS, options);
         }
 
         /**
@@ skipping 370 matching lines @@
                 cronetEngine = possibleEngine;
             }
         } catch (ClassNotFoundException e) {
             // Leave as null.
         } catch (Exception e) {
             throw new IllegalStateException("Cannot instantiate: " + CRONET_URL_REQUEST_CONTEXT, e);
         }
         return cronetEngine;
     }
 }