Allow command-line arguments to override EF public key

chrome/common/origin_trials/origin_trial_key_manager.cc

 // Copyright (c) 2016 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.
 
 #include "chrome/common/origin_trials/origin_trial_key_manager.h"
 
 #include <stdint.h>
 
+#include "base/base64.h"
+
 // This is the default public key used for validating signatures.
 // TODO(iclelland): Provide a mechanism to allow for multiple signing keys.
 // https://crbug.com/584737
-// TODO(iclelland): Provide a mechanism to override, replace or disable this key
-// with field trials.
-static const uint8_t kPublicKey[] = {
+static const uint8_t kDefaultPublicKey[] = {
     0x7c, 0xc4, 0xb8, 0x9a, 0x93, 0xba, 0x6e, 0xe2, 0xd0, 0xfd, 0x03,
     0x1d, 0xfb, 0x32, 0x66, 0xc7, 0x3b, 0x72, 0xfd, 0x54, 0x3a, 0x07,
     0x51, 0x14, 0x66, 0xaa, 0x02, 0x53, 0x4e, 0x33, 0xa1, 0x15,
 };
 
-base::StringPiece OriginTrialKeyManager::GetPublicKey() {
-  return base::StringPiece(reinterpret_cast<const char*>(kPublicKey),
-                           arraysize(kPublicKey));
+OriginTrialKeyManager::OriginTrialKeyManager()
+    : public_key_(std::string(reinterpret_cast<const char*>(kDefaultPublicKey),

[sky, 2016/04/14 16:19:51]

Rather than the cast why not declare kDefaultPublicKey as a const char[] ?

[iclelland, 2016/04/14 19:29:07]

The signedness of plain char isn't defined, and so I wasn't certain whether or
not it is technically valid to assign character literals outside of the [0,0x7f]
range to them.

(Also see the previous comment about std::string -- is it better to make these
char's, and build a std::string out of them, or leave them as uint8_t, and
return a std::vector?)

+                              arraysize(kDefaultPublicKey))) {}
+
+OriginTrialKeyManager::~OriginTrialKeyManager() {}
+
+bool OriginTrialKeyManager::SetPublicKeyFromASCIIString(
+    const std::string& ascii_public_key) {
+  // Base64-decode the incoming string. Set the key if it is correctly formatted
+  std::string new_public_key;
+  if (!base::Base64Decode(ascii_public_key, &new_public_key))
+    return false;
+  if (new_public_key.size() != 32)
+    return false;
+  public_key_.swap(new_public_key);
+  return true;
 }
+
+base::StringPiece OriginTrialKeyManager::GetPublicKey() const {
+  return base::StringPiece(public_key_);
+}