1 // Copyright (c) 2012 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 "crypto/encryptor.h" 6 7 #include "base/logging.h" 8 #include "base/sys_byteorder.h" 9 10 namespace crypto { 11 12 ///////////////////////////////////////////////////////////////////////////// 13 // Encyptor::Counter Implementation. 14 Encryptor::Counter::Counter(const base::StringPiece& counter) { 15 CHECK(sizeof(counter_) == counter.length()); 16 17 memcpy(&counter_, counter.data(), sizeof(counter_)); 18 } 19 20 Encryptor::Counter::~Counter() { 21 } 22 23 bool Encryptor::Counter::Increment() { 24 uint64 low_num = base::NetToHost64(counter_.components64[1]); 25 uint64 new_low_num = low_num + 1; 26 counter_.components64[1] = base::HostToNet64(new_low_num); 27 28 // If overflow occured then increment the most significant component. 29 if (new_low_num < low_num) { 30 counter_.components64[0] = 31 base::HostToNet64(base::NetToHost64(counter_.components64[0]) + 1); 32 } 33 34 // TODO(hclam): Return false if counter value overflows. 35 return true; 36 } 37 38 void Encryptor::Counter::Write(void* buf) { 39 uint8* buf_ptr = reinterpret_cast<uint8*>(buf); 40 memcpy(buf_ptr, &counter_, sizeof(counter_)); 41 } 42 43 size_t Encryptor::Counter::GetLengthInBytes() const { 44 return sizeof(counter_); 45 } 46 47 ///////////////////////////////////////////////////////////////////////////// 48 // Partial Encryptor Implementation. 49 50 bool Encryptor::SetCounter(const base::StringPiece& counter) { 51 if (mode_ != CTR) 52 return false; 53 if (counter.length() != 16u) 54 return false; 55 56 counter_.reset(new Counter(counter)); 57 return true; 58 } 59 60 bool Encryptor::GenerateCounterMask(size_t plaintext_len, 61 uint8* mask, 62 size_t* mask_len) { 63 DCHECK_EQ(CTR, mode_); 64 CHECK(mask); 65 CHECK(mask_len); 66 67 const size_t kBlockLength = counter_->GetLengthInBytes(); 68 size_t blocks = (plaintext_len + kBlockLength - 1) / kBlockLength; 69 CHECK(blocks); 70 71 *mask_len = blocks * kBlockLength; 72 73 for (size_t i = 0; i < blocks; ++i) { 74 counter_->Write(mask); 75 mask += kBlockLength; 76 77 bool ret = counter_->Increment(); 78 if (!ret) 79 return false; 80 } 81 return true; 82 } 83 84 void Encryptor::MaskMessage(const void* plaintext, 85 size_t plaintext_len, 86 const void* mask, 87 void* ciphertext) const { 88 DCHECK_EQ(CTR, mode_); 89 const uint8* plaintext_ptr = reinterpret_cast<const uint8*>(plaintext); 90 const uint8* mask_ptr = reinterpret_cast<const uint8*>(mask); 91 uint8* ciphertext_ptr = reinterpret_cast<uint8*>(ciphertext); 92 93 for (size_t i = 0; i < plaintext_len; ++i) 94 ciphertext_ptr[i] = plaintext_ptr[i] ^ mask_ptr[i]; 95 } 96 97 } // namespace crypto 98
