net/quic/crypto/crypto_secret_boxer.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/crypto_secret_boxer.h"
   6
   7 #include "base/logging.h"
   8 #include "base/memory/scoped_ptr.h"
   9 #include "crypto/secure_hash.h"
  10 #include "crypto/sha2.h"
  11 #include "net/quic/crypto/quic_random.h"
  12
  13 using base::StringPiece;
  14 using std::string;
  15
  16 namespace net {
  17
  18 // Defined kKeySize for GetKeySize() and SetKey().
  19 static const size_t kKeySize = 16;
  20
  21 // kBoxNonceSize contains the number of bytes of nonce that we use in each box.
  22 static const size_t kBoxNonceSize = 16;
  23
  24 // static
  25 size_t CryptoSecretBoxer::GetKeySize() { return kKeySize; }
  26
  27 void CryptoSecretBoxer::SetKey(StringPiece key) {
  28   DCHECK_EQ(static_cast<size_t>(kKeySize), key.size());
  29   key_ = key.as_string();
  30 }
  31
  32 // TODO(rtenneti): Delete sha256 based code. Use Aes128Gcm12Encrypter to Box the
  33 // plaintext. This is temporary solution for tests to pass.
  34 string CryptoSecretBoxer::Box(QuicRandom* rand, StringPiece plaintext) const {
  35   string ret;
  36   const size_t len = kBoxNonceSize + plaintext.size() + crypto::kSHA256Length;
  37   ret.resize(len);
  38   char* data = &ret[0];
  39
  40   // Generate nonce.
  41   rand->RandBytes(data, kBoxNonceSize);
  42   memcpy(data + kBoxNonceSize, plaintext.data(), plaintext.size());
  43
  44   // Compute sha256 for nonce + plaintext.
  45   scoped_ptr<crypto::SecureHash> sha256(crypto::SecureHash::Create(
  46       crypto::SecureHash::SHA256));
  47   sha256->Update(data, kBoxNonceSize + plaintext.size());
  48   sha256->Finish(data + kBoxNonceSize + plaintext.size(),
  49                  crypto::kSHA256Length);
  50
  51   return ret;
  52 }
  53
  54 // TODO(rtenneti): Delete sha256 based code. Use Aes128Gcm12Decrypter to Unbox
  55 // the plaintext. This is temporary solution for tests to pass.
  56 bool CryptoSecretBoxer::Unbox(StringPiece ciphertext,
  57                               string* out_storage,
  58                               StringPiece* out) const {
  59   if (ciphertext.size() < kBoxNonceSize + crypto::kSHA256Length) {
  60     return false;
  61   }
  62
  63   const size_t plaintext_len =
  64       ciphertext.size() - kBoxNonceSize - crypto::kSHA256Length;
  65   out_storage->resize(plaintext_len);
  66   char* data = const_cast<char*>(out_storage->data());
  67
  68   // Copy plaintext from ciphertext.
  69   if (plaintext_len != 0) {
  70     memcpy(data, ciphertext.data() + kBoxNonceSize, plaintext_len);
  71   }
  72
  73   // Compute sha256 for nonce + plaintext.
  74   scoped_ptr<crypto::SecureHash> sha256(crypto::SecureHash::Create(
  75       crypto::SecureHash::SHA256));
  76   sha256->Update(ciphertext.data(), ciphertext.size() - crypto::kSHA256Length);
  77   char sha256_bytes[crypto::kSHA256Length];
  78   sha256->Finish(sha256_bytes, sizeof(sha256_bytes));
  79
  80   // Verify sha256.
  81   if (0 != memcmp(ciphertext.data() + ciphertext.size() - crypto::kSHA256Length,
  82                   sha256_bytes, crypto::kSHA256Length)) {
  83     return false;
  84   }
  85
  86   out->set(data, plaintext_len);
  87   return true;
  88 }
  89
  90 }  // namespace net