1 // Copyright (c) 2011 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.
5 #include "crypto/encryptor.h"
7 #include <openssl/aes.h>
8 #include <openssl/evp.h>
10 #include "base/logging.h"
11 #include "base/strings/string_util.h"
12 #include "crypto/openssl_util.h"
13 #include "crypto/symmetric_key.h"
19 const EVP_CIPHER* GetCipherForKey(SymmetricKey* key) {
20 switch (key->key().length()) {
21 case 16: return EVP_aes_128_cbc();
22 case 24: return EVP_aes_192_cbc();
23 case 32: return EVP_aes_256_cbc();
28 // On destruction this class will cleanup the ctx, and also clear the OpenSSL
29 // ERR stack as a convenience.
30 class ScopedCipherCTX {
32 explicit ScopedCipherCTX() {
33 EVP_CIPHER_CTX_init(&ctx_);
36 EVP_CIPHER_CTX_cleanup(&ctx_);
37 ClearOpenSSLERRStack(FROM_HERE);
39 EVP_CIPHER_CTX* get() { return &ctx_; }
47 Encryptor::Encryptor()
52 Encryptor::~Encryptor() {
55 bool Encryptor::Init(SymmetricKey* key,
57 const base::StringPiece& iv) {
59 DCHECK(mode == CBC || mode == CTR);
62 if (mode == CBC && iv.size() != AES_BLOCK_SIZE)
65 if (GetCipherForKey(key) == NULL)
70 iv.CopyToString(&iv_);
74 bool Encryptor::Encrypt(const base::StringPiece& plaintext,
75 std::string* ciphertext) {
76 CHECK(!plaintext.empty() || (mode_ == CBC));
77 return (mode_ == CTR) ?
78 CryptCTR(true, plaintext, ciphertext) :
79 Crypt(true, plaintext, ciphertext);
82 bool Encryptor::Decrypt(const base::StringPiece& ciphertext,
83 std::string* plaintext) {
84 CHECK(!ciphertext.empty());
85 return (mode_ == CTR) ?
86 CryptCTR(false, ciphertext, plaintext) :
87 Crypt(false, ciphertext, plaintext);
90 bool Encryptor::Crypt(bool do_encrypt,
91 const base::StringPiece& input,
92 std::string* output) {
93 DCHECK(key_); // Must call Init() before En/De-crypt.
94 // Work on the result in a local variable, and then only transfer it to
95 // |output| on success to ensure no partial data is returned.
99 const EVP_CIPHER* cipher = GetCipherForKey(key_);
100 DCHECK(cipher); // Already handled in Init();
102 const std::string& key = key_->key();
103 DCHECK_EQ(EVP_CIPHER_iv_length(cipher), static_cast<int>(iv_.length()));
104 DCHECK_EQ(EVP_CIPHER_key_length(cipher), static_cast<int>(key.length()));
107 if (!EVP_CipherInit_ex(ctx.get(), cipher, NULL,
108 reinterpret_cast<const uint8*>(key.data()),
109 reinterpret_cast<const uint8*>(iv_.data()),
113 // When encrypting, add another block size of space to allow for any padding.
114 const size_t output_size = input.size() + (do_encrypt ? iv_.size() : 0);
115 CHECK_GT(output_size, 0u);
116 CHECK_GT(output_size + 1, input.size());
117 uint8* out_ptr = reinterpret_cast<uint8*>(WriteInto(&result,
120 if (!EVP_CipherUpdate(ctx.get(), out_ptr, &out_len,
121 reinterpret_cast<const uint8*>(input.data()),
125 // Write out the final block plus padding (if any) to the end of the data
128 if (!EVP_CipherFinal_ex(ctx.get(), out_ptr + out_len, &tail_len))
132 DCHECK_LE(out_len, static_cast<int>(output_size));
133 result.resize(out_len);
135 output->swap(result);
139 bool Encryptor::CryptCTR(bool do_encrypt,
140 const base::StringPiece& input,
141 std::string* output) {
142 if (!counter_.get()) {
143 LOG(ERROR) << "Counter value not set in CTR mode.";
148 if (AES_set_encrypt_key(reinterpret_cast<const uint8*>(key_->key().data()),
149 key_->key().size() * 8, &aes_key) != 0) {
153 const size_t out_size = input.size();
154 CHECK_GT(out_size, 0u);
155 CHECK_GT(out_size + 1, input.size());
158 uint8* out_ptr = reinterpret_cast<uint8*>(WriteInto(&result, out_size + 1));
160 uint8_t ivec[AES_BLOCK_SIZE] = { 0 };
161 uint8_t ecount_buf[AES_BLOCK_SIZE] = { 0 };
162 unsigned int block_offset = 0;
164 counter_->Write(ivec);
166 AES_ctr128_encrypt(reinterpret_cast<const uint8*>(input.data()), out_ptr,
167 input.size(), &aes_key, ivec, ecount_buf, &block_offset);
169 // AES_ctr128_encrypt() updates |ivec|. Update the |counter_| here.
170 SetCounter(base::StringPiece(reinterpret_cast<const char*>(ivec),
173 output->swap(result);
177 } // namespace crypto