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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
* This file is part of the LibreOffice project.
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/
#include <pdf/PDFEncryptorR6.hxx>
#include <pdf/EncryptionHashTransporter.hxx>
#include <pdf/pdfwriter_impl.hxx>
#include <comphelper/crypto/Crypto.hxx>
#include <comphelper/hash.hxx>
#include <comphelper/random.hxx>
namespace vcl::pdf
{
namespace
{
constexpr size_t IV_SIZE = 16;
constexpr size_t KEY_SIZE = 32;
constexpr size_t SALT_SIZE = 8;
/** Calculates modulo 3 of the 128-bit integer, using the first 16 bytes of the vector */
sal_Int32 calculateModulo3(std::vector<sal_uInt8> const& rInput)
{
sal_Int32 nSum = 0;
for (size_t i = 0; i < 16; ++i)
nSum += rInput[i];
return nSum % 3;
}
void generateBytes(std::vector<sal_uInt8>& rBytes, size_t nSize)
{
rBytes.resize(nSize);
for (size_t i = 0; i < rBytes.size(); ++i)
rBytes[i] = sal_uInt8(comphelper::rng::uniform_uint_distribution(0, 0xFF));
}
} // end anonymous
std::vector<sal_uInt8> generateKey()
{
std::vector<sal_uInt8> aKey;
generateBytes(aKey, KEY_SIZE);
return aKey;
}
bool validateUserPassword(const sal_uInt8* pPass, size_t nLength, std::vector<sal_uInt8>& U)
{
std::vector<sal_uInt8> aHash(U.begin(), U.begin() + KEY_SIZE);
std::vector<sal_uInt8> aValidationSalt(U.begin() + KEY_SIZE, U.begin() + KEY_SIZE + SALT_SIZE);
std::vector<sal_uInt8> aCalculatedHash
= vcl::pdf::computeHashR6(pPass, nLength, aValidationSalt);
return aHash == aCalculatedHash;
}
bool validateOwnerPassword(const sal_uInt8* pPass, size_t nLength, std::vector<sal_uInt8>& U,
std::vector<sal_uInt8>& O)
{
std::vector<sal_uInt8> aHash(O.begin(), O.begin() + KEY_SIZE);
std::vector<sal_uInt8> aValidationSalt(O.begin() + KEY_SIZE, O.begin() + KEY_SIZE + SALT_SIZE);
std::vector<sal_uInt8> aCalculatedHash
= vcl::pdf::computeHashR6(pPass, nLength, aValidationSalt, U);
return aHash == aCalculatedHash;
}
/** Algorithm 8 */
void generateUandUE(const sal_uInt8* pPass, size_t nLength,
std::vector<sal_uInt8>& rFileEncryptionKey, std::vector<sal_uInt8>& U,
std::vector<sal_uInt8>& UE)
{
std::vector<sal_uInt8> aValidationSalt;
generateBytes(aValidationSalt, SALT_SIZE);
std::vector<sal_uInt8> aKeySalt;
generateBytes(aKeySalt, SALT_SIZE);
U = vcl::pdf::computeHashR6(pPass, nLength, aValidationSalt);
U.insert(U.end(), aValidationSalt.begin(), aValidationSalt.end());
U.insert(U.end(), aKeySalt.begin(), aKeySalt.end());
std::vector<sal_uInt8> aKeyHash = vcl::pdf::computeHashR6(pPass, nLength, aKeySalt);
std::vector<sal_uInt8> iv(IV_SIZE, 0); // zero IV
UE = std::vector<sal_uInt8>(rFileEncryptionKey.size(), 0);
comphelper::Encrypt aEncrypt(aKeyHash, iv, comphelper::CryptoType::AES_256_CBC);
aEncrypt.update(UE, rFileEncryptionKey);
}
/** Algorithm 9 */
void generateOandOE(const sal_uInt8* pPass, size_t nLength,
std::vector<sal_uInt8>& rFileEncryptionKey, std::vector<sal_uInt8>& U,
std::vector<sal_uInt8>& O, std::vector<sal_uInt8>& OE)
{
std::vector<sal_uInt8> aValidationSalt;
generateBytes(aValidationSalt, SALT_SIZE);
std::vector<sal_uInt8> aKeySalt;
generateBytes(aKeySalt, SALT_SIZE);
O = vcl::pdf::computeHashR6(pPass, nLength, aValidationSalt, U);
O.insert(O.end(), aValidationSalt.begin(), aValidationSalt.end());
O.insert(O.end(), aKeySalt.begin(), aKeySalt.end());
std::vector<sal_uInt8> aKeyHash = vcl::pdf::computeHashR6(pPass, nLength, aKeySalt, U);
std::vector<sal_uInt8> iv(IV_SIZE, 0); // zero IV
OE = std::vector<sal_uInt8>(rFileEncryptionKey.size(), 0);
comphelper::Encrypt aEncrypt(aKeyHash, iv, comphelper::CryptoType::AES_256_CBC);
aEncrypt.update(OE, rFileEncryptionKey);
}
/** Algorithm 8 step b) */
std::vector<sal_uInt8> decryptKey(const sal_uInt8* pPass, size_t nLength, std::vector<sal_uInt8>& U,
std::vector<sal_uInt8>& UE)
{
std::vector<sal_uInt8> aKeySalt(U.begin() + KEY_SIZE + SALT_SIZE,
U.begin() + KEY_SIZE + SALT_SIZE + SALT_SIZE);
auto aKeyHash = vcl::pdf::computeHashR6(pPass, nLength, aKeySalt);
std::vector<sal_uInt8> aEncryptedKey(UE.begin(), UE.begin() + KEY_SIZE);
std::vector<sal_uInt8> iv(IV_SIZE, 0);
comphelper::Decrypt aDecryptCBC(aKeyHash, iv, comphelper::CryptoType::AES_256_CBC);
std::vector<sal_uInt8> aFileEncryptionKey(aEncryptedKey.size());
sal_uInt32 nDecrypted = aDecryptCBC.update(aFileEncryptionKey, aEncryptedKey);
if (nDecrypted == 0)
return std::vector<sal_uInt8>();
return aFileEncryptionKey;
}
/** Algorithm 13: Validating the permissions */
std::vector<sal_uInt8> decryptPerms(std::vector<sal_uInt8>& rPermsEncrypted,
std::vector<sal_uInt8>& rFileEncryptionKey)
{
std::vector<sal_uInt8> aPermsDecrpyted(rPermsEncrypted.size());
std::vector<sal_uInt8> iv(IV_SIZE, 0);
comphelper::Decrypt aDecryptor(rFileEncryptionKey, iv, comphelper::CryptoType::AES_256_ECB);
aDecryptor.update(aPermsDecrpyted, rPermsEncrypted);
return aPermsDecrpyted;
}
/** Algorithm 10 step f) */
std::vector<sal_uInt8> encryptPerms(std::vector<sal_uInt8>& rPerms,
std::vector<sal_uInt8>& rFileEncryptionKey)
{
std::vector<sal_uInt8> aPermsEncrypted(rPerms.size());
std::vector<sal_uInt8> iv(IV_SIZE, 0);
comphelper::Encrypt aEncryptor(rFileEncryptionKey, iv, comphelper::CryptoType::AES_256_ECB);
aEncryptor.update(aPermsEncrypted, rPerms);
return aPermsEncrypted;
}
/** Algorithm 10 steps a) - e) */
std::vector<sal_uInt8> createPerms(sal_Int32 nAccessPermissions, bool bEncryptMetadata)
{
std::vector<sal_uInt8> aPermsCreated;
generateBytes(aPermsCreated, 16);
aPermsCreated[0] = sal_uInt8(nAccessPermissions);
aPermsCreated[1] = sal_uInt8(nAccessPermissions >> 8);
aPermsCreated[2] = sal_uInt8(nAccessPermissions >> 16);
aPermsCreated[3] = sal_uInt8(nAccessPermissions >> 24);
aPermsCreated[4] = sal_uInt8(0xff);
aPermsCreated[5] = sal_uInt8(0xff);
aPermsCreated[6] = sal_uInt8(0xff);
aPermsCreated[7] = sal_uInt8(0xff);
aPermsCreated[8] = bEncryptMetadata ? 'T' : 'F'; // Encrypt metadata
aPermsCreated[9] = 'a';
aPermsCreated[10] = 'd';
aPermsCreated[11] = 'b';
return aPermsCreated;
}
/** Algorithm 2.B: Computing a hash (revision 6 and later) */
std::vector<sal_uInt8> computeHashR6(const sal_uInt8* pPassword, size_t nPasswordLength,
std::vector<sal_uInt8> const& rValidationSalt,
std::vector<sal_uInt8> const& rUserKey)
{
// Round 0
comphelper::Hash aHash(comphelper::HashType::SHA256);
aHash.update(pPassword, nPasswordLength);
aHash.update(rValidationSalt);
if (!rUserKey.empty()) // if calculating owner key
aHash.update(rUserKey);
std::vector<sal_uInt8> K = aHash.finalize();
std::vector<sal_uInt8> E;
sal_Int32 nRound = 1; // round 0 is done already
do
{
// Step a)
std::vector<sal_uInt8> K1;
for (sal_Int32 nRepetition = 0; nRepetition < 64; ++nRepetition)
{
K1.insert(K1.end(), pPassword, pPassword + nPasswordLength);
K1.insert(K1.end(), K.begin(), K.end());
if (!rUserKey.empty()) // if calculating owner key
K1.insert(K1.end(), rUserKey.begin(), rUserKey.end());
}
// Step b)
std::vector<sal_uInt8> aKey(K.begin(), K.begin() + 16);
std::vector<sal_uInt8> aInitVector(K.begin() + 16, K.end());
E = std::vector<sal_uInt8>(K1.size(), 0);
comphelper::Encrypt aEncrypt(aKey, aInitVector, comphelper::CryptoType::AES_128_CBC);
aEncrypt.update(E, K1);
// Step c)
sal_Int32 nModulo3Result = calculateModulo3(E);
// Step d)
comphelper::HashType eType;
switch (nModulo3Result)
{
case 0:
eType = comphelper::HashType::SHA256;
break;
case 1:
eType = comphelper::HashType::SHA384;
break;
default:
eType = comphelper::HashType::SHA512;
break;
}
K = comphelper::Hash::calculateHash(E.data(), E.size(), eType);
nRound++;
}
// Step e) and f)
// We stop iteration if we do at least 64 rounds and (the last element of E <= round number - 32)
while (nRound < 64 || E.back() > (nRound - 32));
// Output - first 32 bytes
return std::vector<sal_uInt8>(K.begin(), K.begin() + 32);
}
size_t addPaddingToVector(std::vector<sal_uInt8>& rVector, size_t nBlockSize)
{
size_t nPaddedSize = comphelper::roundUp(rVector.size(), size_t(nBlockSize));
if (nPaddedSize > rVector.size())
{
sal_uInt8 nPaddedValue = sal_uInt8(nPaddedSize - rVector.size());
rVector.resize(nPaddedSize, nPaddedValue);
}
return nPaddedSize;
}
} // end vcl::pdf
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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