1 // Copyright (c) 2013 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #include "net/quic/crypto/curve25519_key_exchange.h" 6 7 #include "base/logging.h" 8 #include "crypto/curve25519.h" 9 #include "net/quic/crypto/quic_random.h" 10 11 using base::StringPiece; 12 using std::string; 13 14 namespace net { 15 16 Curve25519KeyExchange::Curve25519KeyExchange() {} 17 18 Curve25519KeyExchange::~Curve25519KeyExchange() {} 19 20 // static 21 Curve25519KeyExchange* Curve25519KeyExchange::New( 22 const StringPiece& private_key) { 23 Curve25519KeyExchange* ka; 24 // We don't want to #include the NaCl headers in the public header file, so 25 // we use literals for the sizes of private_key_ and public_key_. Here we 26 // assert that those values are equal to the values from the NaCl header. 27 COMPILE_ASSERT( 28 sizeof(ka->private_key_) == crypto::curve25519::kScalarBytes, 29 header_out_of_sync); 30 COMPILE_ASSERT(sizeof(ka->public_key_) == crypto::curve25519::kBytes, 31 header_out_of_sync); 32 33 if (private_key.size() != crypto::curve25519::kScalarBytes) { 34 return NULL; 35 } 36 37 ka = new Curve25519KeyExchange(); 38 memcpy(ka->private_key_, private_key.data(), 39 crypto::curve25519::kScalarBytes); 40 crypto::curve25519::ScalarBaseMult(ka->private_key_, ka->public_key_); 41 return ka; 42 } 43 44 // static 45 string Curve25519KeyExchange::NewPrivateKey(QuicRandom* rand) { 46 uint8 private_key[crypto::curve25519::kScalarBytes]; 47 rand->RandBytes(private_key, sizeof(private_key)); 48 49 // This makes |private_key| a valid scalar, as specified on 50 // http://cr.yp.to/ecdh.html 51 private_key[0] &= 248; 52 private_key[31] &= 127; 53 private_key[31] |= 64; 54 return string(reinterpret_cast<char*>(private_key), sizeof(private_key)); 55 } 56 57 KeyExchange* Curve25519KeyExchange::NewKeyPair(QuicRandom* rand) const { 58 const string private_value = NewPrivateKey(rand); 59 return Curve25519KeyExchange::New(private_value); 60 } 61 62 bool Curve25519KeyExchange::CalculateSharedKey( 63 const StringPiece& peer_public_value, 64 string* out_result) const { 65 if (peer_public_value.size() != crypto::curve25519::kBytes) { 66 return false; 67 } 68 69 uint8 result[crypto::curve25519::kBytes]; 70 crypto::curve25519::ScalarMult( 71 private_key_, 72 reinterpret_cast<const uint8*>(peer_public_value.data()), 73 result); 74 out_result->assign(reinterpret_cast<char*>(result), sizeof(result)); 75 76 return true; 77 } 78 79 StringPiece Curve25519KeyExchange::public_value() const { 80 return StringPiece(reinterpret_cast<const char*>(public_key_), 81 sizeof(public_key_)); 82 } 83 84 QuicTag Curve25519KeyExchange::tag() const { return kC255; } 85 86 } // namespace net 87
