Encrypt certificate logger requests for extended reporting

chrome/browser/net/cert_logger.proto

 // Copyright (c) 2011 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.
 //
 // This protobuffer is intended to store reports from Chrome users of
 // certificate pinning errors. A report will be sent from Chrome when it gets
 // e.g. a certificate for google.com that chains up to a root CA not expected by
 // Chrome for that origin, such as DigiNotar (compromised in July 2011), or
 // other pinning errors such as a blacklisted cert in the chain. The
 // report from the user will include the hostname being accessed, 
@@ skipping 35 matching lines @@
     OK = 1;
     MALFORMED_CERT_DATA = 2;
     HOST_CERT_DONT_MATCH = 3;
     ROOT_NOT_RECOGNIZED = 4;
     ROOT_NOT_UNEXPECTED = 5;
     OTHER_ERROR = 6;
   };
   required ResponseCode response = 1;
 };
 
+// A wrapper proto containing an encrypted CertLoggerRequest
+message EncryptedCertLoggerRequest {
+  // An encrypted, serialized CertLoggerRequest
+  required bytes encrypted_report = 1;
+  // An identifier for the server public key that was used to encrypt
+  // this report.
+  required uint32 server_public_key = 2;
+  // The ephemeral client public key used to encrypt the report.
+  required bytes client_public_key = 3;
+
+  required bytes nonce = 4;

[agl, 2015/03/05 19:22:25]

Since the key is random per-message, the nonce can be fixed and thus omitted
from the protobuf if you like.

+  required bytes mac = 5;

[agl, 2015/03/05 19:22:25]

this shouldn't be split out, it should be appended to the ciphertext. AEADs work
on opaque ciphertext blocks and don't generally expose their internals like
this.

+
+  enum Algorithm {
+    UNKNOWN_ALGORITHM = 0;
+    ECDH_AES_CTR_128_HMAC_SHA256 = 1;

[agl, 2015/03/05 19:22:25]

the server side that I reviewed was using AES_256.

+  }
+
+  optional Algorithm algorithm = 6 [default = UNKNOWN_ALGORITHM];

[agl, 2015/03/05 19:22:25]

the default is UNKNOWN_ALGORITHM? Don't you want the default to be
ECDH_AES_CTR_128_HMAC_SHA256?

+}