net/quic/crypto/p256_key_exchange_openssl.cc

   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/p256_key_exchange.h"
   6
   7 #include <openssl/ec.h>
   8 #include <openssl/ecdh.h>
   9 #include <openssl/evp.h>
  10
  11 #include "base/logging.h"
  12
  13 using base::StringPiece;
  14 using std::string;
  15
  16 namespace net {
  17
  18 P256KeyExchange::P256KeyExchange(EC_KEY* private_key, const uint8* public_key)
  19     : private_key_(private_key) {
  20   memcpy(public_key_, public_key, sizeof(public_key_));
  21 }
  22
  23 P256KeyExchange::~P256KeyExchange() {}
  24
  25 // static
  26 P256KeyExchange* P256KeyExchange::New(StringPiece key) {
  27   if (key.empty()) {
  28     DVLOG(1) << "Private key is empty";
  29     return NULL;
  30   }
  31
  32   const uint8* keyp = reinterpret_cast<const uint8*>(key.data());
  33   crypto::ScopedEC_KEY private_key(d2i_ECPrivateKey(NULL, &keyp, key.size()));
  34   if (!private_key.get() || !EC_KEY_check_key(private_key.get())) {
  35     DVLOG(1) << "Private key is invalid.";
  36     return NULL;
  37   }
  38
  39   uint8 public_key[kUncompressedP256PointBytes];
  40   if (EC_POINT_point2oct(EC_KEY_get0_group(private_key.get()),
  41                          EC_KEY_get0_public_key(private_key.get()),
  42                          POINT_CONVERSION_UNCOMPRESSED, public_key,
  43                          sizeof(public_key), NULL) != sizeof(public_key)) {
  44     DVLOG(1) << "Can't get public key.";
  45     return NULL;
  46   }
  47
  48   return new P256KeyExchange(private_key.release(), public_key);
  49 }
  50
  51 // static
  52 string P256KeyExchange::NewPrivateKey() {
  53   crypto::ScopedEC_KEY key(EC_KEY_new_by_curve_name(NID_X9_62_prime256v1));
  54   if (!key.get() || !EC_KEY_generate_key(key.get())) {
  55     DVLOG(1) << "Can't generate a new private key.";
  56     return string();
  57   }
  58
  59   int key_len = i2d_ECPrivateKey(key.get(), NULL);
  60   if (key_len <= 0) {
  61     DVLOG(1) << "Can't convert private key to string";
  62     return string();
  63   }
  64   scoped_ptr<uint8[]> private_key(new uint8[key_len]);
  65   uint8* keyp = private_key.get();
  66   if (!i2d_ECPrivateKey(key.get(), &keyp)) {
  67     DVLOG(1) << "Can't convert private key to string.";
  68     return string();
  69   }
  70   return string(reinterpret_cast<char*>(private_key.get()), key_len);
  71 }
  72
  73 KeyExchange* P256KeyExchange::NewKeyPair(QuicRandom* /*rand*/) const {
  74   // TODO(agl): avoid the serialisation/deserialisation in this function.
  75   const string private_value = NewPrivateKey();
  76   return P256KeyExchange::New(private_value);
  77 }
  78
  79 bool P256KeyExchange::CalculateSharedKey(const StringPiece& peer_public_value,
  80                                          string* out_result) const {
  81   if (peer_public_value.size() != kUncompressedP256PointBytes) {
  82     DVLOG(1) << "Peer public value is invalid";
  83     return false;
  84   }
  85
  86   crypto::ScopedOpenSSL<EC_POINT, EC_POINT_free>::Type point(
  87       EC_POINT_new(EC_KEY_get0_group(private_key_.get())));
  88   if (!point.get() ||
  89       !EC_POINT_oct2point( /* also test if point is on curve */
  90           EC_KEY_get0_group(private_key_.get()),
  91           point.get(),
  92           reinterpret_cast<const uint8*>(peer_public_value.data()),
  93           peer_public_value.size(), NULL)) {
  94     DVLOG(1) << "Can't convert peer public value to curve point.";
  95     return false;
  96   }
  97
  98   uint8 result[kP256FieldBytes];
  99   if (ECDH_compute_key(result, sizeof(result), point.get(), private_key_.get(),
 100                        NULL) != sizeof(result)) {
 101     DVLOG(1) << "Can't compute ECDH shared key.";
 102     return false;
 103   }
 104
 105   out_result->assign(reinterpret_cast<char*>(result), sizeof(result));
 106   return true;
 107 }
 108
 109 StringPiece P256KeyExchange::public_value() const {
 110   return StringPiece(reinterpret_cast<const char*>(public_key_),
 111                      sizeof(public_key_));
 112 }
 113
 114 QuicTag P256KeyExchange::tag() const { return kP256; }
 115
 116 }  // namespace net
 117