encfs/encfs/Cipher.cpp

/*****************************************************************************
 * Author:   Valient Gough <vgough@pobox.com>
 *
 *****************************************************************************
 * Copyright (c) 2002-2004, Valient Gough
 *
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or (at your
 * option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <cstddef>
#include <iostream>
#include <list>
#include <map>
#include <string>
#include <utility>

#include "Cipher.h"
#include "CipherKey.h"
#include "Interface.h"
// for static build.  Need to reference the modules which are registered at
// run-time, to ensure that the linker doesn't optimize them away.
#include "NullCipher.h"
#include "Range.h"
#include "SSL_Cipher.h"
#include "base64.h"

using namespace std;

namespace encfs {

#define REF_MODULE(TYPE) \
  if (!TYPE::Enabled()) cerr << "referenceModule: should never happen\n";

static void AddSymbolReferences() {
  REF_MODULE(SSL_Cipher)
  REF_MODULE(NullCipher)
}

struct CipherAlg {
  bool hidden;
  Cipher::CipherConstructor constructor;
  string description;
  Interface iface;
  Range keyLength;
  Range blockSize;
};

using CipherMap_t = multimap<string, CipherAlg>;
static CipherMap_t *gCipherMap = nullptr;

std::list<Cipher::CipherAlgorithm> Cipher::GetAlgorithmList(
    bool includeHidden) {
  AddSymbolReferences();

  list<CipherAlgorithm> result;

  if (gCipherMap == nullptr) {
    return result;
  }

  CipherMap_t::const_iterator it;
  CipherMap_t::const_iterator mapEnd = gCipherMap->end();
  for (it = gCipherMap->begin(); it != mapEnd; ++it) {
    if (includeHidden || !it->second.hidden) {
      CipherAlgorithm tmp;
      tmp.name = it->first;
      tmp.description = it->second.description;
      tmp.iface = it->second.iface;
      tmp.keyLength = it->second.keyLength;
      tmp.blockSize = it->second.blockSize;

      result.push_back(tmp);
    }
  }

  return result;
}

bool Cipher::Register(const char *name, const char *description,
                      const Interface &iface, CipherConstructor fn,
                      bool hidden) {
  Range keyLength(-1, -1, 1);
  Range blockSize(-1, -1, 1);
  return Cipher::Register(name, description, iface, keyLength, blockSize, fn,
                          hidden);
}

bool Cipher::Register(const char *name, const char *description,
                      const Interface &iface, const Range &keyLength,
                      const Range &blockSize, CipherConstructor fn,
                      bool hidden) {
  if (gCipherMap == nullptr) {
    gCipherMap = new CipherMap_t;
  }

  CipherAlg ca;
  ca.hidden = hidden;
  ca.constructor = fn;
  ca.description = description;
  ca.iface = iface;
  ca.keyLength = keyLength;
  ca.blockSize = blockSize;

  gCipherMap->insert(make_pair(string(name), ca));
  return true;
}
std::shared_ptr<Cipher> Cipher::New(const string &name, int keyLen) {
  std::shared_ptr<Cipher> result;

  if (gCipherMap != nullptr) {
    CipherMap_t::const_iterator it = gCipherMap->find(name);
    if (it != gCipherMap->end()) {
      CipherConstructor fn = it->second.constructor;
      // use current interface..
      result = (*fn)(it->second.iface, keyLen);
    }
  }

  return result;
}
std::shared_ptr<Cipher> Cipher::New(const Interface &iface, int keyLen) {
  std::shared_ptr<Cipher> result;
  if (gCipherMap != nullptr) {
    CipherMap_t::const_iterator it;
    CipherMap_t::const_iterator mapEnd = gCipherMap->end();

    for (it = gCipherMap->begin(); it != mapEnd; ++it) {
      // TODO: we should look for the newest implementation..
      if (it->second.iface.implements(iface)) {
        CipherConstructor fn = it->second.constructor;
        // pass in requested interface..
        result = (*fn)(iface, keyLen);

        // if we're not going to compare the options, then just stop
        // now..
        break;
      }
    }
  }

  return result;
}

Cipher::Cipher() = default;

Cipher::~Cipher() = default;

unsigned int Cipher::MAC_32(const unsigned char *src, int len,
                            const CipherKey &key, uint64_t *chainedIV) const {
  uint64_t mac64 = MAC_64(src, len, key, chainedIV);

  unsigned int mac32 = ((mac64 >> 32) & 0xffffffff) ^ (mac64 & 0xffffffff);

  return mac32;
}

unsigned int Cipher::MAC_16(const unsigned char *src, int len,
                            const CipherKey &key, uint64_t *chainedIV) const {
  uint64_t mac64 = MAC_64(src, len, key, chainedIV);

  unsigned int mac32 = ((mac64 >> 32) & 0xffffffff) ^ (mac64 & 0xffffffff);
  unsigned int mac16 = ((mac32 >> 16) & 0xffff) ^ (mac32 & 0xffff);

  return mac16;
}

bool Cipher::nameEncode(unsigned char *data, int len, uint64_t iv64,
                        const CipherKey &key) const {
  return streamEncode(data, len, iv64, key);
}

bool Cipher::nameDecode(unsigned char *data, int len, uint64_t iv64,
                        const CipherKey &key) const {
  return streamDecode(data, len, iv64, key);
}

string Cipher::encodeAsString(const CipherKey &key,
                              const CipherKey &encodingKey) {
  int encodedKeySize = this->encodedKeySize();
  auto *keyBuf = new unsigned char[encodedKeySize];

  // write the key, encoding it with itself.
  this->writeKey(key, keyBuf, encodingKey);

  int b64Len = B256ToB64Bytes(encodedKeySize);
  auto *b64Key = new unsigned char[b64Len + 1];

  changeBase2(keyBuf, encodedKeySize, 8, b64Key, b64Len, 6);
  B64ToAscii(b64Key, b64Len);
  b64Key[b64Len - 1] = '\0';

  string str((const char *)b64Key);
  delete[] b64Key;
  delete[] keyBuf;

  return str;
}

}  // namespace encfs