1//
2// Copyright (C) 2012 The Android Open Source Project
3//
4// Licensed under the Apache License, Version 2.0 (the "License");
5// you may not use this file except in compliance with the License.
6// You may obtain a copy of the License at
7//
8//      http://www.apache.org/licenses/LICENSE-2.0
9//
10// Unless required by applicable law or agreed to in writing, software
11// distributed under the License is distributed on an "AS IS" BASIS,
12// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13// See the License for the specific language governing permissions and
14// limitations under the License.
15//
16
17#include "shill/crypto_des_cbc.h"
18
19#include <rpc/des_crypt.h>
20
21#include <base/files/file_util.h>
22#include <base/strings/string_util.h>
23#include <brillo/data_encoding.h>
24
25using base::FilePath;
26using std::string;
27using std::vector;
28
29namespace shill {
30
31const unsigned int CryptoDESCBC::kBlockSize = 8;
32const char CryptoDESCBC::kID[] = "des-cbc";
33const char CryptoDESCBC::kSentinel[] = "[ok]";
34const char CryptoDESCBC::kVersion2Prefix[] = "02:";
35
36CryptoDESCBC::CryptoDESCBC() {}
37
38string CryptoDESCBC::GetID() {
39  return kID;
40}
41
42bool CryptoDESCBC::Encrypt(const string& plaintext, string* ciphertext) {
43  // Never encrypt. We'll fall back to rot47 which doesn't depend on
44  // the owner key which may change due to rotation.
45  return false;
46}
47
48bool CryptoDESCBC::Decrypt(const string& ciphertext, string* plaintext) {
49  CHECK_EQ(kBlockSize, key_.size());
50  CHECK_EQ(kBlockSize, iv_.size());
51  int version = 1;
52  string b64_ciphertext = ciphertext;
53  if (base::StartsWith(ciphertext, kVersion2Prefix,
54                       base::CompareCase::SENSITIVE)) {
55    version = 2;
56    b64_ciphertext.erase(0, strlen(kVersion2Prefix));
57  }
58
59  string decoded_data;
60  if (!brillo::data_encoding::Base64Decode(b64_ciphertext, &decoded_data)) {
61    LOG(ERROR) << "Unable to base64-decode DEC-CBC ciphertext.";
62    return false;
63  }
64
65  vector<char> data(decoded_data.c_str(),
66                    decoded_data.c_str() + decoded_data.length());
67  if (data.empty() || (data.size() % kBlockSize != 0)) {
68    LOG(ERROR) << "Invalid DES-CBC ciphertext size: " << data.size();
69    return false;
70  }
71
72  // The IV is modified in place.
73  vector<char> iv = iv_;
74  int rv =
75      cbc_crypt(key_.data(), data.data(), data.size(), DES_DECRYPT, iv.data());
76  if (DES_FAILED(rv)) {
77    LOG(ERROR) << "DES-CBC decryption failed.";
78    return false;
79  }
80  if (data.back() != '\0') {
81    LOG(ERROR) << "DEC-CBC decryption resulted in invalid plain text.";
82    return false;
83  }
84  string text = data.data();
85  if (version == 2) {
86    if (!base::EndsWith(text, kSentinel, base::CompareCase::SENSITIVE)) {
87      LOG(ERROR) << "DES-CBC decrypted text missing sentinel -- bad key?";
88      return false;
89    }
90    text.erase(text.size() - strlen(kSentinel), strlen(kSentinel));
91  }
92  *plaintext = text;
93  return true;
94}
95
96bool CryptoDESCBC::LoadKeyMatter(const FilePath& path) {
97  key_.clear();
98  iv_.clear();
99  string matter;
100  // TODO(petkov): This mimics current flimflam behavior. Fix it so that it
101  // doesn't read the whole file.
102  if (!base::ReadFileToString(path, &matter)) {
103    LOG(ERROR) << "Unable to load key matter from " << path.value();
104    return false;
105  }
106  if (matter.size() < 2 * kBlockSize) {
107    LOG(ERROR) << "Key matter data not enough " << matter.size() << " < "
108               << 2 * kBlockSize;
109    return false;
110  }
111  string::const_iterator matter_start =
112      matter.begin() + (matter.size() - 2 * kBlockSize);
113  key_.assign(matter_start + kBlockSize, matter_start + 2 * kBlockSize);
114  iv_.assign(matter_start, matter_start + kBlockSize);
115  return true;
116}
117
118}  // namespace shill
119