Update from https://crrev.com/307664

crypto/p224_spake.cc

 // Copyright (c) 2012 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 code implements SPAKE2, a variant of EKE:
 //  http://www.di.ens.fr/~pointche/pub.php?reference=AbPo04
 
 #include <crypto/p224_spake.h>
 
+#include <algorithm>
+
 #include <base/logging.h>
 #include <crypto/p224.h>
 #include <crypto/random.h>
 #include <crypto/secure_util.h>
 
 namespace {
 
 // The following two points (M and N in the protocol) are verifiable random
 // points on the curve and can be generated with the following code:
 
@@ skipping 78 matching lines @@
 P224EncryptedKeyExchange::P224EncryptedKeyExchange(
     PeerType peer_type, const base::StringPiece& password)
     : state_(kStateInitial),
       is_server_(peer_type == kPeerTypeServer) {
   memset(&x_, 0, sizeof(x_));
   memset(&expected_authenticator_, 0, sizeof(expected_authenticator_));
 
   // x_ is a random scalar.
   RandBytes(x_, sizeof(x_));
 
-  // X = g**x_
-  p224::Point X;
-  p224::ScalarBaseMult(x_, &X);
-
   // Calculate |password| hash to get SPAKE password value.
   SHA256HashString(std::string(password.data(), password.length()),
                    pw_, sizeof(pw_));
 
+  Init();
+}
+
+void P224EncryptedKeyExchange::Init() {
+  // X = g**x_
+  p224::Point X;
+  p224::ScalarBaseMult(x_, &X);
+
   // The client masks the Diffie-Hellman value, X, by adding M**pw and the
   // server uses N**pw.
   p224::Point MNpw;
   p224::ScalarMult(is_server_ ? kN : kM, pw_, &MNpw);
 
   // X* = X + (N|M)**pw
   p224::Point Xstar;
   p224::Add(X, MNpw, &Xstar);
 
   next_message_ = Xstar.ToString();
@@ skipping 120 matching lines @@
 }
 
 const std::string& P224EncryptedKeyExchange::GetUnverifiedKey() const {
   // Key is already final when state is kStateSendHash. Subsequent states are
   // used only for verification of the key. Some users may combine verification
   // with sending verifiable data instead of |expected_authenticator_|.
   DCHECK_GE(state_, kStateSendHash);
   return key_;
 }
 
+void P224EncryptedKeyExchange::SetXForTesting(const std::string& x) {
+  memset(&x_, 0, sizeof(x_));
+  memcpy(&x_, x.data(), std::min(x.size(), sizeof(x_)));
+  Init();
+}
+
 }  // namespace crypto