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/basictypes.h"
8 #include "base/logging.h"
9 #include "crypto/curve25519.h"
10 #include "net/quic/crypto/quic_random.h"
11
12 using base::StringPiece;
13 using std::string;
14
15 namespace net {
16
Curve25519KeyExchange()17 Curve25519KeyExchange::Curve25519KeyExchange() {}
18
~Curve25519KeyExchange()19 Curve25519KeyExchange::~Curve25519KeyExchange() {}
20
21 // static
New(const StringPiece & private_key)22 Curve25519KeyExchange* Curve25519KeyExchange::New(
23 const StringPiece& private_key) {
24 Curve25519KeyExchange* ka;
25 // We don't want to #include the NaCl headers in the public header file, so
26 // we use literals for the sizes of private_key_ and public_key_. Here we
27 // assert that those values are equal to the values from the NaCl header.
28 COMPILE_ASSERT(
29 sizeof(ka->private_key_) == crypto::curve25519::kScalarBytes,
30 header_out_of_sync);
31 COMPILE_ASSERT(sizeof(ka->public_key_) == crypto::curve25519::kBytes,
32 header_out_of_sync);
33
34 if (private_key.size() != crypto::curve25519::kScalarBytes) {
35 return NULL;
36 }
37
38 ka = new Curve25519KeyExchange();
39 memcpy(ka->private_key_, private_key.data(),
40 crypto::curve25519::kScalarBytes);
41 crypto::curve25519::ScalarBaseMult(ka->private_key_, ka->public_key_);
42 return ka;
43 }
44
45 // static
NewPrivateKey(QuicRandom * rand)46 string Curve25519KeyExchange::NewPrivateKey(QuicRandom* rand) {
47 uint8 private_key[crypto::curve25519::kScalarBytes];
48 rand->RandBytes(private_key, sizeof(private_key));
49
50 // This makes |private_key| a valid scalar, as specified on
51 // http://cr.yp.to/ecdh.html
52 private_key[0] &= 248;
53 private_key[31] &= 127;
54 private_key[31] |= 64;
55 return string(reinterpret_cast<char*>(private_key), sizeof(private_key));
56 }
57
NewKeyPair(QuicRandom * rand) const58 KeyExchange* Curve25519KeyExchange::NewKeyPair(QuicRandom* rand) const {
59 const string private_value = NewPrivateKey(rand);
60 return Curve25519KeyExchange::New(private_value);
61 }
62
CalculateSharedKey(const StringPiece & peer_public_value,string * out_result) const63 bool Curve25519KeyExchange::CalculateSharedKey(
64 const StringPiece& peer_public_value,
65 string* out_result) const {
66 if (peer_public_value.size() != crypto::curve25519::kBytes) {
67 return false;
68 }
69
70 uint8 result[crypto::curve25519::kBytes];
71 crypto::curve25519::ScalarMult(
72 private_key_,
73 reinterpret_cast<const uint8*>(peer_public_value.data()),
74 result);
75 out_result->assign(reinterpret_cast<char*>(result), sizeof(result));
76
77 return true;
78 }
79
public_value() const80 StringPiece Curve25519KeyExchange::public_value() const {
81 return StringPiece(reinterpret_cast<const char*>(public_key_),
82 sizeof(public_key_));
83 }
84
tag() const85 QuicTag Curve25519KeyExchange::tag() const { return kC255; }
86
87 } // namespace net
88