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PDF4QT/Pdf4QtLib/sources/pdfsecurityhandler.cpp

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2021-09-27 11:14:20 +02:00
// Copyright (C) 2019-2021 Jakub Melka
//
// This file is part of PDF4QT.
//
// PDF4QT 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
// with the written consent of the copyright owner, any later version.
//
// PDF4QT 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 PDF4QT. If not, see <https://www.gnu.org/licenses/>.
#include "pdfsecurityhandler.h"
#include "pdfexception.h"
#include "pdfencoding.h"
#include "pdfvisitor.h"
#include "pdfutils.h"
#include "pdfdocumentbuilder.h"
#include <QRandomGenerator>
#include <openssl/rc4.h>
#include <openssl/md5.h>
#include <openssl/aes.h>
#include <openssl/sha.h>
#include <array>
namespace pdf
{
// Padding password
static constexpr std::array<uint8_t, 32> PDFPasswordPadding = {
0x28, 0xBF, 0x4E, 0x5E, 0x4E, 0x75, 0x8A, 0x41,
0x64, 0x00, 0x4E, 0x56, 0xFF, 0xFA, 0x01, 0x08,
0x2E, 0x2E, 0x00, 0xB6, 0xD0, 0x68, 0x3E, 0x80,
0x2F, 0x0C, 0xA9, 0xFE, 0x64, 0x53, 0x69, 0x7A
};
class PDFDecryptOrEncryptObjectVisitor : public PDFAbstractVisitor
{
public:
enum class Mode
{
Decrypt,
Encrypt
};
explicit PDFDecryptOrEncryptObjectVisitor(const PDFSecurityHandler* securityHandler, PDFObjectReference reference, Mode mode) :
m_securityHandler(securityHandler),
m_reference(reference),
m_mode(mode)
{
m_objectStack.reserve(32);
}
virtual void visitNull() override;
virtual void visitBool(bool value) override;
virtual void visitInt(PDFInteger value) override;
virtual void visitReal(PDFReal value) override;
virtual void visitString(PDFStringRef string) override;
virtual void visitName(PDFStringRef name) override;
virtual void visitArray(const PDFArray* array) override;
virtual void visitDictionary(const PDFDictionary* dictionary) override;
virtual void visitStream(const PDFStream* stream) override;
virtual void visitReference(const PDFObjectReference reference) override;
PDFObject getProcessedObject();
private:
const PDFSecurityHandler* m_securityHandler = nullptr;
std::vector<PDFObject> m_objectStack;
PDFObjectReference m_reference;
Mode m_mode = Mode::Decrypt;
};
void PDFDecryptOrEncryptObjectVisitor::visitNull()
{
m_objectStack.push_back(PDFObject::createNull());
}
void PDFDecryptOrEncryptObjectVisitor::visitBool(bool value)
{
m_objectStack.push_back(PDFObject::createBool(value));
}
void PDFDecryptOrEncryptObjectVisitor::visitInt(PDFInteger value)
{
m_objectStack.push_back(PDFObject::createInteger(value));
}
void PDFDecryptOrEncryptObjectVisitor::visitReal(PDFReal value)
{
m_objectStack.push_back(PDFObject::createReal(value));
}
void PDFDecryptOrEncryptObjectVisitor::visitString(PDFStringRef string)
{
switch (m_mode)
{
case pdf::PDFDecryptOrEncryptObjectVisitor::Mode::Decrypt:
m_objectStack.push_back(PDFObject::createString(m_securityHandler->decrypt(string.getString(), m_reference, PDFSecurityHandler::EncryptionScope::String)));
break;
case pdf::PDFDecryptOrEncryptObjectVisitor::Mode::Encrypt:
m_objectStack.push_back(PDFObject::createString(m_securityHandler->encrypt(string.getString(), m_reference, PDFSecurityHandler::EncryptionScope::String)));
break;
default:
Q_ASSERT(false);
break;
}
}
void PDFDecryptOrEncryptObjectVisitor::visitName(PDFStringRef name)
{
m_objectStack.push_back(PDFObject::createName(name));
}
void PDFDecryptOrEncryptObjectVisitor::visitArray(const PDFArray* array)
{
acceptArray(array);
// We have all objects on the stack
Q_ASSERT(array->getCount() <= m_objectStack.size());
auto it = std::next(m_objectStack.cbegin(), m_objectStack.size() - array->getCount());
std::vector<PDFObject> objects(it, m_objectStack.cend());
PDFObject object = PDFObject::createArray(std::make_shared<PDFArray>(qMove(objects)));
m_objectStack.erase(it, m_objectStack.cend());
m_objectStack.push_back(object);
}
void PDFDecryptOrEncryptObjectVisitor::visitDictionary(const PDFDictionary* dictionary)
{
Q_ASSERT(dictionary);
// We must check, if it is or isn't a signature dictionary. If it is,
// then don't decrypt/encrypt the Content value. We also don't check, if signature
// isn't indirectly referenced by reference. Hope it isn't...
const PDFObject& typeObject = dictionary->get("Type");
bool isSignatureObject = (typeObject.isName() && typeObject.getString() == "Sig");
std::vector<PDFDictionary::DictionaryEntry> entries;
entries.reserve(dictionary->getCount());
for (size_t i = 0, count = dictionary->getCount(); i < count; ++i)
{
if (isSignatureObject && dictionary->getKey(i) == "Contents")
{
entries.emplace_back(dictionary->getKey(i), dictionary->getValue(i));
}
else
{
dictionary->getValue(i).accept(this);
entries.emplace_back(dictionary->getKey(i), m_objectStack.back());
m_objectStack.pop_back();
}
}
m_objectStack.push_back(PDFObject::createDictionary(std::make_shared<PDFDictionary>(qMove(entries))));
}
void PDFDecryptOrEncryptObjectVisitor::visitStream(const PDFStream* stream)
{
// Don't decrypt/encrypt, if it is a Metadata stream and Metadata encryption is turned off
const PDFDictionary* dictionary = stream->getDictionary();
const PDFObject& typeObject = dictionary->get("Type");
bool isMetadata = (typeObject.isName() && typeObject.getString() == "Metadata");
if (isMetadata && !m_securityHandler->isMetadataEncrypted())
{
m_objectStack.push_back(PDFObject::createStream(std::make_shared<PDFStream>(PDFDictionary(*dictionary), QByteArray(*stream->getContent()))));
return;
}
// Decrypt/encrypt the dictionary
visitDictionary(dictionary);
PDFObject dictionaryObject = m_objectStack.back();
m_objectStack.pop_back();
// We must also handle situation, that stream has specified Crypt filter.
// In this case, we must delegate decryption/encryption to the stream filters.
PDFDictionary processedDictionary(*dictionaryObject.getDictionary());
QByteArray processedData;
if (!processedDictionary.hasKey("Crypt"))
{
// Is it an embedded file?
const PDFObject& object = processedDictionary.get("Type");
const bool isEmbeddedFile = object.isName() && object.getString() == "EmbeddedFile";
const PDFSecurityHandler::EncryptionScope scope = !isEmbeddedFile ? PDFSecurityHandler::EncryptionScope::Stream : PDFSecurityHandler::EncryptionScope::EmbeddedFile;
switch (m_mode)
{
case pdf::PDFDecryptOrEncryptObjectVisitor::Mode::Decrypt:
processedData = m_securityHandler->decrypt(*stream->getContent(), m_reference, scope);
break;
case pdf::PDFDecryptOrEncryptObjectVisitor::Mode::Encrypt:
processedData = m_securityHandler->encrypt(*stream->getContent(), m_reference, scope);
break;
default:
Q_ASSERT(false);
break;
}
processedDictionary.setEntry(PDFInplaceOrMemoryString("Length"), PDFObject::createInteger(processedData.size()));
}
else
{
switch (m_mode)
{
case pdf::PDFDecryptOrEncryptObjectVisitor::Mode::Decrypt:
{
processedData = *stream->getContent();
processedDictionary.setEntry(PDFInplaceOrMemoryString(PDFSecurityHandler::OBJECT_REFERENCE_DICTIONARY_NAME), PDFObject::createReference(m_reference));
break;
}
case pdf::PDFDecryptOrEncryptObjectVisitor::Mode::Encrypt:
{
processedData = *stream->getContent();
processedDictionary.removeEntry(PDFSecurityHandler::OBJECT_REFERENCE_DICTIONARY_NAME);
break;
}
default:
Q_ASSERT(false);
break;
}
}
m_objectStack.push_back(PDFObject::createStream(std::make_shared<PDFStream>(qMove(processedDictionary), qMove(processedData))));
}
void PDFDecryptOrEncryptObjectVisitor::visitReference(const PDFObjectReference reference)
{
m_objectStack.push_back(PDFObject::createReference(reference));
}
PDFObject PDFDecryptOrEncryptObjectVisitor::getProcessedObject()
{
Q_ASSERT(m_objectStack.size() == 1);
return qMove(m_objectStack.back());
}
PDFObject PDFSecurityHandler::decryptObject(const PDFObject& object, PDFObjectReference reference) const
{
PDFDecryptOrEncryptObjectVisitor visitor(this, reference, PDFDecryptOrEncryptObjectVisitor::Mode::Decrypt);
object.accept(&visitor);
return visitor.getProcessedObject();
}
PDFObject PDFSecurityHandler::encryptObject(const PDFObject& object, PDFObjectReference reference) const
{
PDFDecryptOrEncryptObjectVisitor visitor(this, reference, PDFDecryptOrEncryptObjectVisitor::Mode::Encrypt);
object.accept(&visitor);
return visitor.getProcessedObject();
}
PDFSecurityHandlerPointer PDFSecurityHandler::createSecurityHandler(const PDFObject& encryptionDictionaryObject, const QByteArray& id)
{
if (encryptionDictionaryObject.isNull())
{
return PDFSecurityHandlerPointer(new PDFNoneSecurityHandler());
}
if (!encryptionDictionaryObject.isDictionary())
{
throw PDFException(PDFTranslationContext::tr("Invalid encryption dictionary."));
}
const PDFDictionary* dictionary = encryptionDictionaryObject.getDictionary();
auto getName = [](const PDFDictionary* dictionary, const char* key, bool required, const char* defaultValue = nullptr) -> QByteArray
{
const PDFObject& nameObject = dictionary->get(key);
if (nameObject.isNull())
{
return defaultValue ? QByteArray(defaultValue) : QByteArray();
}
if (!nameObject.isName())
{
if (required)
{
throw PDFException(PDFTranslationContext::tr("Invalid value for entry '%1' in encryption dictionary. Name expected.").arg(QString::fromLatin1(key)));
}
return defaultValue ? QByteArray(defaultValue) : QByteArray();
}
return nameObject.getString();
};
auto getInt = [](const PDFDictionary* dictionary, const char* key, bool required, PDFInteger defaultValue = -1) -> PDFInteger
{
const PDFObject& intObject = dictionary->get(key);
if (!intObject.isInt())
{
if (required)
{
throw PDFException(PDFTranslationContext::tr("Invalid value for entry '%1' in encryption dictionary. Integer expected.").arg(QString::fromLatin1(key)));
}
return defaultValue;
}
return intObject.getInteger();
};
QByteArray filterName = getName(dictionary, "Filter", true);
if (filterName != "Standard")
{
throw PDFException(PDFTranslationContext::tr("Unknown security handler."));
}
const int V = getInt(dictionary, "V", true);
// Check V
if (V < 1 || V > 5)
{
throw PDFException(PDFTranslationContext::tr("Unsupported version of document encryption (V = %1).").arg(V));
}
// Only valid for V == 2 or V == 3, otherwise we set file encryption key length manually
int Length = 40;
switch (V)
{
case 1:
Length = 40;
break;
case 2:
case 3:
Length = getInt(dictionary, "Length", false, 40);
break;
case 4:
Length = 128;
break;
case 5:
Length = 256;
break;
default:
Q_ASSERT(false);
break;
}
// Create standard security handler
PDFStandardSecurityHandler handler;
handler.m_V = V;
handler.m_keyLength = Length;
// Add "Identity" filter to the filters
CryptFilter identityFilter;
identityFilter.type = CryptFilterType::Identity;
handler.m_cryptFilters[IDENTITY_FILTER_NAME] = identityFilter;
if (V == 4 || V == 5)
{
const PDFObject& cryptFilterObjects = dictionary->get("CF");
if (cryptFilterObjects.isDictionary())
{
auto parseCryptFilter = [Length, &getName, &getInt](const PDFObject& object) -> CryptFilter
{
if (!object.isDictionary())
{
throw PDFException(PDFTranslationContext::tr("Crypt filter is not a dictionary!"));
}
const PDFDictionary* cryptFilterDictionary = object.getDictionary();
CryptFilter filter;
QByteArray CFMName = getName(cryptFilterDictionary, "CFM", false, "None");
if (CFMName == "None")
{
filter.type = CryptFilterType::None;
}
else if (CFMName == "V2")
{
filter.type = CryptFilterType::V2;
}
else if (CFMName == "AESV2")
{
filter.type = CryptFilterType::AESV2;
}
else if (CFMName == "AESV3")
{
filter.type = CryptFilterType::AESV3;
}
else
{
throw PDFException(PDFTranslationContext::tr("Unsupported encryption algorithm '%1'.").arg(QString::fromLatin1(CFMName)));
}
QByteArray authEventName = getName(cryptFilterDictionary, "AuthEvent", false, "DocOpen");
if (authEventName == "DocOpen")
{
filter.authEvent = AuthEvent::DocOpen;
}
else if (authEventName == "EFOpen")
{
filter.authEvent = AuthEvent::EFOpen;
}
else
{
throw PDFException(PDFTranslationContext::tr("Unsupported authorization event '%1'.").arg(QString::fromLatin1(authEventName)));
}
filter.keyLength = getInt(cryptFilterDictionary, "Length", false, Length / 8);
return filter;
};
const PDFDictionary* cryptFilters = cryptFilterObjects.getDictionary();
for (size_t i = 0, cryptFilterCount = cryptFilters->getCount(); i < cryptFilterCount; ++i)
{
handler.m_cryptFilters[cryptFilters->getKey(i).getString()] = parseCryptFilter(cryptFilters->getValue(i));
}
}
// Now, add standard filters
auto resolveFilter = [&handler](const QByteArray& name)
{
auto it = handler.m_cryptFilters.find(name);
if (it == handler.m_cryptFilters.cend())
{
throw PDFException(PDFTranslationContext::tr("Unknown crypt filter '%1'.").arg(QString::fromLatin1(name)));
}
return it->second;
};
handler.m_filterStreams = resolveFilter(getName(dictionary, "StmF", false, IDENTITY_FILTER_NAME));
handler.m_filterStrings = resolveFilter(getName(dictionary, "StrF", false, IDENTITY_FILTER_NAME));
if (dictionary->hasKey("EFF"))
{
handler.m_filterEmbeddedFiles = resolveFilter(getName(dictionary, "EFF", true));
}
else
{
// According to the PDF specification, if 'EFF' entry is omitted, then filter
// for streams is used.
handler.m_filterEmbeddedFiles = handler.m_filterStreams;
}
}
int R = getInt(dictionary, "R", true);
if (R < 2 || R > 6)
{
throw PDFException(PDFTranslationContext::tr("Revision %1 of standard security handler is not supported.").arg(R));
}
handler.m_R = R;
handler.m_filterDefault.authEvent = AuthEvent::DocOpen;
handler.m_filterDefault.keyLength = Length / 8;
handler.m_filterDefault.type = (R > 4) ? CryptFilterType::AESV3 : CryptFilterType::V2;
auto readByteArray = [dictionary](const char* key, int size)
{
QByteArray result;
const PDFObject& object = dictionary->get(key);
if (object.isString())
{
result = object.getString();
if (result.size() != size)
{
throw PDFException(PDFTranslationContext::tr("Expected %1 characters long string in entry '%2'. Provided length is %3.").arg(size).arg(QString::fromLatin1(key)).arg(result.size()));
}
}
else
{
throw PDFException(PDFTranslationContext::tr("Expected %1 characters long string in entry '%2'.").arg(size).arg(QString::fromLatin1(key)));
}
return result;
};
handler.m_O = readByteArray("O", (R != 6 && R != 5) ? 32 : 48);
handler.m_U = readByteArray("U", (R != 6 && R != 5) ? 32 : 48);
handler.m_permissions = static_cast<uint32_t>(static_cast<int>(getInt(dictionary, "P", true)));
if (R == 6 || R == 5)
{
handler.m_OE = readByteArray("OE", 32);
handler.m_UE = readByteArray("UE", 32);
handler.m_Perms = readByteArray("Perms", 16);
}
const PDFObject& encryptMetadataObject = dictionary->get("EncryptMetadata");
if (encryptMetadataObject.isBool())
{
handler.m_encryptMetadata = encryptMetadataObject.getBool();
}
handler.m_ID = id;
return PDFSecurityHandlerPointer(new PDFStandardSecurityHandler(qMove(handler)));
}
void PDFSecurityHandler::fillEncryptionDictionary(PDFObjectFactory& factory) const
{
factory.beginDictionaryItem("V");
factory << PDFInteger(m_V);
factory.endDictionaryItem();
factory.beginDictionaryItem("Length");
factory << PDFInteger(m_keyLength);
factory.endDictionaryItem();
if (m_V == 4 || m_V == 5)
{
factory.beginDictionaryItem("CF");
factory.beginDictionary();
QByteArray stmfName = "Identity";
QByteArray strfName = stmfName;
QByteArray effName = stmfName;
for (const auto& cryptFilter : m_cryptFilters)
{
factory.beginDictionaryItem(cryptFilter.first);
factory.beginDictionary();
factory.beginDictionaryItem("CFM");
if (cryptFilter.second == m_filterStrings)
{
strfName = cryptFilter.first;
}
if (cryptFilter.second == m_filterStreams)
{
stmfName = cryptFilter.first;
}
if (cryptFilter.second == m_filterEmbeddedFiles)
{
effName = cryptFilter.first;
}
switch (cryptFilter.second.type)
{
case CryptFilterType::None:
// The application shall decrypt the data using the security handler
factory << WrapName("None");
break;
case CryptFilterType::V2:
// Use file encryption key for RC4 algorithm
factory << WrapName("V2");
break;
case CryptFilterType::AESV2:
// Use file encryption key for AES algorithm
factory << WrapName("AESV2");
break;
case CryptFilterType::AESV3:
// Use file encryption key for AES 256 bit algorithm
factory << WrapName("AESV3");
break;
case CryptFilterType::Identity:
// Don't decrypt anything, use identity function
factory << WrapName("Identity");
break;
default:
Q_ASSERT(false);
factory << WrapName("None");
break;
}
factory.endDictionaryItem();
factory.beginDictionaryItem("AuthEvent");
switch (cryptFilter.second.authEvent)
{
case AuthEvent::DocOpen:
factory << WrapName("DocOpen");
break;
case AuthEvent::EFOpen:
factory << WrapName("EFOpen");
break;
default:
Q_ASSERT(false);
break;
}
factory.endDictionaryItem();
factory.beginDictionaryItem("Length");
factory << cryptFilter.second.keyLength;
factory.endDictionaryItem();
factory.endDictionary();
factory.endDictionaryItem();
}
factory.endDictionary();
factory.endDictionaryItem();
// Store StmF, StrF, EFF
factory.beginDictionaryItem("StmF");
factory << WrapName(stmfName);
factory.endDictionaryItem();
factory.beginDictionaryItem("StrF");
factory << WrapName(strfName);
factory.endDictionaryItem();
factory.beginDictionaryItem("EFF");
factory << WrapName(effName);
factory.endDictionaryItem();
}
}
PDFSecurityHandler* PDFStandardSecurityHandler::clone() const
{
return new PDFStandardSecurityHandler(*this);
}
PDFSecurityHandler::AuthorizationResult PDFStandardSecurityHandler::authenticate(const std::function<QString(bool*)>& getPasswordCallback, bool authorizeOwnerOnly)
{
QByteArray password;
bool passwordObtained = true;
// Clear the authorization data
m_authorizationData = AuthorizationData();
while (passwordObtained)
{
switch (m_R)
{
case 2:
case 3:
case 4:
{
// Try to authorize by owner password
{
QByteArray userPassword = createUserPasswordFromOwnerPassword(password);
QByteArray fileEncryptionKey = createFileEncryptionKey(userPassword);
QByteArray U = createEntryValueU_r234(fileEncryptionKey);
if (U == m_U)
{
// We have authorized owner access
m_authorizationData.authorizationResult = AuthorizationResult::OwnerAuthorized;
m_authorizationData.fileEncryptionKey = fileEncryptionKey;
return AuthorizationResult::OwnerAuthorized;
}
}
// Try to authorize user password
if (!authorizeOwnerOnly)
{
QByteArray fileEncryptionKey = createFileEncryptionKey(password);
QByteArray U = createEntryValueU_r234(fileEncryptionKey);
if (U == m_U)
{
// We have authorized user access
m_authorizationData.authorizationResult = AuthorizationResult::UserAuthorized;
m_authorizationData.fileEncryptionKey = fileEncryptionKey;
return AuthorizationResult::UserAuthorized;
}
}
break;
}
case 5:
case 6:
{
UserOwnerData_r6 userData = parseParts(m_U);
UserOwnerData_r6 ownerData = parseParts(m_O);
auto createHash_r5 = [](const QByteArray& inputData)
{
QByteArray result(SHA256_DIGEST_LENGTH, char(0));
SHA256(convertByteArrayToUcharPtr(inputData), inputData.size(), convertByteArrayToUcharPtr(result));
return result;
};
auto createHash_r56 = [this, &createHash_r5](const QByteArray& input, const QByteArray& inputPassword, bool useUserKey)
{
return (m_R == 5) ? createHash_r5(input) : createHash_r6(input, inputPassword, useUserKey);
};
// Try to authorize owner password
{
QByteArray inputData = password + ownerData.validationSalt + m_U;
QByteArray hash = createHash_r56(inputData, password, true);
if (hash == ownerData.hash)
{
// We have authorized owner access. Now we must calculate the owner encryption key
QByteArray fileEncryptionKeyInputData = password + ownerData.keySalt + m_U;
QByteArray fileEncryptionDecryptionKey = createHash_r56(fileEncryptionKeyInputData, password, true);
Q_ASSERT(fileEncryptionDecryptionKey.size() == 32);
AES_KEY key = { };
AES_set_decrypt_key(convertByteArrayToUcharPtr(fileEncryptionDecryptionKey), fileEncryptionDecryptionKey.size() * 8, &key);
unsigned char aesInitializationVector[AES_BLOCK_SIZE] = { };
m_authorizationData.fileEncryptionKey.resize(m_OE.size());
AES_cbc_encrypt(convertByteArrayToUcharPtr(m_OE), convertByteArrayToUcharPtr(m_authorizationData.fileEncryptionKey), m_OE.size(), &key, aesInitializationVector, AES_DECRYPT);
m_authorizationData.authorizationResult = AuthorizationResult::OwnerAuthorized;
}
}
// Try to authorize user password
if (!m_authorizationData.isAuthorized() && !authorizeOwnerOnly)
{
QByteArray inputData = password + userData.validationSalt;
QByteArray hash = createHash_r56(inputData, password, false);
if (hash == userData.hash)
{
QByteArray fileEncryptionKeyInputData = password + userData.keySalt;
QByteArray fileEncryptionDecryptionKey = createHash_r56(fileEncryptionKeyInputData, password, false);
Q_ASSERT(fileEncryptionDecryptionKey.size() == 32);
AES_KEY key = { };
AES_set_decrypt_key(convertByteArrayToUcharPtr(fileEncryptionDecryptionKey), fileEncryptionDecryptionKey.size() * 8, &key);
unsigned char aesInitializationVector[AES_BLOCK_SIZE] = { };
m_authorizationData.fileEncryptionKey.resize(m_UE.size());
AES_cbc_encrypt(convertByteArrayToUcharPtr(m_UE), convertByteArrayToUcharPtr(m_authorizationData.fileEncryptionKey), m_UE.size(), &key, aesInitializationVector, AES_DECRYPT);
// We have authorized user access
m_authorizationData.authorizationResult = AuthorizationResult::UserAuthorized;
}
}
// Stop, if we authorized the document usage
if (m_authorizationData.isAuthorized())
{
// According the PDF specification, we must also check, if flags are not manipulated.
Q_ASSERT(m_Perms.size() == AES_BLOCK_SIZE);
AES_KEY key = { };
AES_set_decrypt_key(convertByteArrayToUcharPtr(m_authorizationData.fileEncryptionKey), m_authorizationData.fileEncryptionKey.size() * 8, &key);
QByteArray decodedPerms(m_Perms.size(), char(0));
AES_ecb_encrypt(convertByteArrayToUcharPtr(m_Perms), convertByteArrayToUcharPtr(decodedPerms), &key, AES_DECRYPT);
// 1) Checks, if bytes 9, 10, 11 are 'a', 'd', 'b'
if (decodedPerms[9] != 'a' || decodedPerms[10] != 'd' || decodedPerms[11] != 'b')
{
throw PDFException(PDFTranslationContext::tr("Permissions entry in the Encryption dictionary is invalid."));
}
// 2) Verify, that bytes 0-3 are valid permissions entry
const uint32_t permissions = qFromLittleEndian(*reinterpret_cast<const uint32_t*>(decodedPerms.data()));
if (permissions != m_permissions)
{
throw PDFException(PDFTranslationContext::tr("Security permissions are manipulated. Can't open the document."));
}
// 3) Verify, that byte 8 is 'T' or 'F' and is equal to EncryptMetadata entry
if (decodedPerms[8] != 'T' && decodedPerms[8] != 'F')
{
throw PDFException(PDFTranslationContext::tr("Security permissions are manipulated. Can't open the document."));
}
if ((decodedPerms[8] == 'T') != m_encryptMetadata)
{
throw PDFException(PDFTranslationContext::tr("Security permissions are manipulated. Can't open the document."));
}
return m_authorizationData.authorizationResult;
}
break;
}
default:
return AuthorizationResult::Failed;
}
password = adjustPassword(getPasswordCallback(&passwordObtained), m_R);
}
return AuthorizationResult::Cancelled;
}
std::vector<uint8_t> PDFStandardSecurityHandler::createV2_ObjectEncryptionKey(PDFObjectReference reference, CryptFilter filter) const
{
std::vector<uint8_t> inputKeyData = convertByteArrayToVector(m_authorizationData.fileEncryptionKey);
uint32_t objectNumber = qToLittleEndian(static_cast<uint32_t>(reference.objectNumber));
uint32_t generation = qToLittleEndian(static_cast<uint32_t>(reference.generation));
inputKeyData.insert(inputKeyData.cend(), { uint8_t(objectNumber & 0xFF), uint8_t((objectNumber >> 8) & 0xFF), uint8_t((objectNumber >> 16) & 0xFF), uint8_t(generation & 0xFF), uint8_t((generation >> 8) & 0xFF) });
std::vector<uint8_t> objectEncryptionKey(MD5_DIGEST_LENGTH, uint8_t(0));
MD5(inputKeyData.data(), inputKeyData.size(), objectEncryptionKey.data());
// Use up to (n + 5) bytes, maximally 16, from the digest as object encryption key
size_t objectEncryptionKeySize = qMin(filter.keyLength + 5, MD5_DIGEST_LENGTH);
objectEncryptionKey.resize(objectEncryptionKeySize);
return objectEncryptionKey;
}
std::vector<uint8_t> PDFStandardSecurityHandler::createAESV2_ObjectEncryptionKey(PDFObjectReference reference) const
{
std::vector<uint8_t> inputKeyData = convertByteArrayToVector(m_authorizationData.fileEncryptionKey);
uint32_t objectNumber = qToLittleEndian(static_cast<uint32_t>(reference.objectNumber));
uint32_t generation = qToLittleEndian(static_cast<uint32_t>(reference.generation));
inputKeyData.insert(inputKeyData.cend(), { uint8_t(objectNumber & 0xFF), uint8_t((objectNumber >> 8) & 0xFF), uint8_t((objectNumber >> 16) & 0xFF), uint8_t(generation & 0xFF), uint8_t((generation >> 8) & 0xFF), 0x73, 0x41, 0x6C, 0x54 });
std::vector<uint8_t> objectEncryptionKey(MD5_DIGEST_LENGTH, uint8_t(0));
MD5(inputKeyData.data(), inputKeyData.size(), objectEncryptionKey.data());
return objectEncryptionKey;
}
QByteArray PDFStandardSecurityHandler::decryptUsingFilter(const QByteArray& data, CryptFilter filter, PDFObjectReference reference) const
{
QByteArray decryptedData;
Q_ASSERT(m_authorizationData.isAuthorized());
struct AES_data
{
QByteArray initializationVector;
QByteArray paddedData;
};
auto prepareAES_data = [](const QByteArray& data)
{
AES_data result;
result.initializationVector = data.left(AES_BLOCK_SIZE);
// This is an error. But to handle it, we resize the vector
// with arbitrary data.
if (result.initializationVector.size() < AES_BLOCK_SIZE)
{
result.initializationVector.resize(AES_BLOCK_SIZE);
}
result.paddedData = data.mid(AES_BLOCK_SIZE);
// Remove errorneous data - we must have a data of multiple of AES_BLOCK_SIZE
const int remainder = result.paddedData.size() % AES_BLOCK_SIZE;
if (remainder != 0)
{
result.paddedData = result.paddedData.left(result.paddedData.size() - remainder);
}
return result;
};
auto removeAES_padding = [](const QByteArray& data)
{
if (data.isEmpty())
{
return data;
}
// If padding doesnt fit from 1 to AES_BLOCK_SIZE, then it is
// an error, but just clamp the value.
const int padding = data.back();
const int clampedPadding = qBound(1, padding, AES_BLOCK_SIZE);
return data.left(data.size() - clampedPadding);
};
switch (filter.type)
{
case CryptFilterType::None: // The application shall decrypt the data using the security handler
{
// This shouldn't occur, because in case the used filter has None value, then default filter
// is used and default filter can't have this value.
Q_ASSERT(false);
break;
}
case CryptFilterType::V2: // Use file encryption key for RC4 algorithm
{
std::vector<uint8_t> objectEncryptionKey = createV2_ObjectEncryptionKey(reference, filter);
decryptedData.resize(data.size());
RC4_KEY key = { };
RC4_set_key(&key, static_cast<int>(objectEncryptionKey.size()), objectEncryptionKey.data());
RC4(&key, data.size(), convertByteArrayToUcharPtr(data), convertByteArrayToUcharPtr(decryptedData));
break;
}
case CryptFilterType::AESV2: // Use file encryption key for AES algorithm
{
std::vector<uint8_t> objectEncryptionKey = createAESV2_ObjectEncryptionKey(reference);
// For AES algorithm, always use 16 bytes key (128 bit encryption mode)
AES_KEY key = { };
AES_set_decrypt_key(objectEncryptionKey.data(), static_cast<int>(objectEncryptionKey.size()) * 8, &key);
AES_data aes_data = prepareAES_data(data);
if (!aes_data.paddedData.isEmpty())
{
decryptedData.resize(aes_data.paddedData.size());
AES_cbc_encrypt(convertByteArrayToUcharPtr(aes_data.paddedData), convertByteArrayToUcharPtr(decryptedData), aes_data.paddedData.length(), &key, convertByteArrayToUcharPtr(aes_data.initializationVector), AES_DECRYPT);
decryptedData = removeAES_padding(decryptedData);
}
break;
}
case CryptFilterType::AESV3: // Use file encryption key for AES 256 bit algorithm
{
Q_ASSERT(m_authorizationData.fileEncryptionKey.size() == 32);
AES_KEY key = { };
AES_set_decrypt_key(convertByteArrayToUcharPtr(m_authorizationData.fileEncryptionKey), static_cast<int>(m_authorizationData.fileEncryptionKey.size()) * 8, &key);
AES_data aes_data = prepareAES_data(data);
if (!aes_data.paddedData.isEmpty())
{
decryptedData.resize(aes_data.paddedData.size());
AES_cbc_encrypt(convertByteArrayToUcharPtr(aes_data.paddedData), convertByteArrayToUcharPtr(decryptedData), aes_data.paddedData.length(), &key, convertByteArrayToUcharPtr(aes_data.initializationVector), AES_DECRYPT);
decryptedData = removeAES_padding(decryptedData);
}
break;
}
case CryptFilterType::Identity: // Don't decrypt anything, use identity function
{
decryptedData = data;
break;
}
}
return decryptedData;
}
QByteArray PDFStandardSecurityHandler::encryptUsingFilter(const QByteArray& data, CryptFilter filter, PDFObjectReference reference) const
{
QByteArray encryptedData;
Q_ASSERT(m_authorizationData.isAuthorized());
struct AES_data
{
QByteArray initializationVector;
QByteArray paddedData;
};
auto prepareAES_data = [](const QByteArray& data)
{
AES_data result;
QRandomGenerator randomNumberGenerator = QRandomGenerator::securelySeeded();
result.initializationVector.resize(AES_BLOCK_SIZE);
for (int i = 0; i < AES_BLOCK_SIZE; ++i)
{
result.initializationVector[i] = uint8_t(randomNumberGenerator.generate());
}
result.paddedData = data;
// Add padding remainder according to the specification
int size = data.size();
const int paddingRemainder = AES_BLOCK_SIZE - (size % AES_BLOCK_SIZE);
result.initializationVector.reserve(result.initializationVector.size() + paddingRemainder);
for (int i = 0; i < paddingRemainder; ++i)
{
result.paddedData.push_back(paddingRemainder);
}
return result;
};
switch (filter.type)
{
case CryptFilterType::None: // The application shall encrypt the data using the security handler
{
// This shouldn't occur, because in case the used filter has None value, then default filter
// is used and default filter can't have this value.
Q_ASSERT(false);
break;
}
case CryptFilterType::V2: // Use file encryption key for RC4 algorithm
{
// This algorithm is same as the encrypt algorithm, because RC4 cipher is symmetrical
std::vector<uint8_t> objectEncryptionKey = createV2_ObjectEncryptionKey(reference, filter);
encryptedData.resize(data.size());
RC4_KEY key = { };
RC4_set_key(&key, static_cast<int>(objectEncryptionKey.size()), objectEncryptionKey.data());
RC4(&key, data.size(), convertByteArrayToUcharPtr(data), convertByteArrayToUcharPtr(encryptedData));
break;
}
case CryptFilterType::AESV2: // Use file encryption key for AES algorithm
{
std::vector<uint8_t> objectEncryptionKey = createAESV2_ObjectEncryptionKey(reference);
// For AES algorithm, always use 16 bytes key (128 bit encryption mode)
AES_KEY key = { };
AES_set_encrypt_key(objectEncryptionKey.data(), static_cast<int>(objectEncryptionKey.size()) * 8, &key);
AES_data aes_data = prepareAES_data(data);
if (!aes_data.paddedData.isEmpty())
{
QByteArray initializationVectorCopy = aes_data.initializationVector;
encryptedData.resize(aes_data.paddedData.size());
AES_cbc_encrypt(convertByteArrayToUcharPtr(aes_data.paddedData), convertByteArrayToUcharPtr(encryptedData), aes_data.paddedData.length(), &key, convertByteArrayToUcharPtr(aes_data.initializationVector), AES_ENCRYPT);
encryptedData.prepend(initializationVectorCopy);
}
break;
}
case CryptFilterType::AESV3: // Use file encryption key for AES 256 bit algorithm
{
Q_ASSERT(m_authorizationData.fileEncryptionKey.size() == 32);
AES_KEY key = { };
AES_set_encrypt_key(convertByteArrayToUcharPtr(m_authorizationData.fileEncryptionKey), static_cast<int>(m_authorizationData.fileEncryptionKey.size()) * 8, &key);
AES_data aes_data = prepareAES_data(data);
if (!aes_data.paddedData.isEmpty())
{
QByteArray initializationVectorCopy = aes_data.initializationVector;
encryptedData.resize(aes_data.paddedData.size());
AES_cbc_encrypt(convertByteArrayToUcharPtr(aes_data.paddedData), convertByteArrayToUcharPtr(encryptedData), aes_data.paddedData.length(), &key, convertByteArrayToUcharPtr(aes_data.initializationVector), AES_ENCRYPT);
encryptedData.prepend(initializationVectorCopy);
}
break;
}
case CryptFilterType::Identity: // Don't decrypt anything, use identity function
{
encryptedData = data;
break;
}
}
return encryptedData;
}
QByteArray PDFStandardSecurityHandler::decrypt(const QByteArray& data, PDFObjectReference reference, EncryptionScope encryptionScope) const
{
CryptFilter filter = getCryptFilter(encryptionScope);
return decryptUsingFilter(data, filter, reference);
}
QByteArray PDFStandardSecurityHandler::decryptByFilter(const QByteArray& data, const QByteArray& filterName, PDFObjectReference reference) const
{
auto it = m_cryptFilters.find(filterName);
if (it == m_cryptFilters.cend())
{
throw PDFException(PDFTranslationContext::tr("Crypt filter '%1' not found.").arg(QString::fromLatin1(filterName)));
}
return decryptUsingFilter(data, it->second, reference);
}
CryptFilter PDFStandardSecurityHandler::getCryptFilter(EncryptionScope encryptionScope) const
{
CryptFilter filter = m_filterDefault;
switch (encryptionScope)
{
case EncryptionScope::String:
{
if (m_filterStrings.type != CryptFilterType::None)
{
filter = m_filterStrings;
}
break;
}
case EncryptionScope::Stream:
{
if (m_filterStreams.type != CryptFilterType::None)
{
filter = m_filterStreams;
}
break;
}
case EncryptionScope::EmbeddedFile:
{
if (m_filterEmbeddedFiles.type != CryptFilterType::None)
{
filter = m_filterEmbeddedFiles;
}
break;
}
}
return filter;
}
QByteArray PDFStandardSecurityHandler::encrypt(const QByteArray& data, PDFObjectReference reference, EncryptionScope encryptionScope) const
{
CryptFilter filter = getCryptFilter(encryptionScope);
return encryptUsingFilter(data, filter, reference);
}
QByteArray PDFStandardSecurityHandler::encryptByFilter(const QByteArray& data, const QByteArray& filterName, PDFObjectReference reference) const
{
auto it = m_cryptFilters.find(filterName);
if (it == m_cryptFilters.cend())
{
throw PDFException(PDFTranslationContext::tr("Crypt filter '%1' not found.").arg(QString::fromLatin1(filterName)));
}
return encryptUsingFilter(data, it->second, reference);
}
PDFObject PDFStandardSecurityHandler::createEncryptionDictionaryObject() const
{
PDFObjectFactory factory;
factory.beginDictionary();
fillEncryptionDictionary(factory);
factory.beginDictionaryItem("Filter");
factory << WrapName("Standard");
factory.endDictionaryItem();
factory.beginDictionaryItem("R");
factory << PDFInteger(m_R);
factory.endDictionaryItem();
factory.beginDictionaryItem("O");
factory << WrapString(m_O);
factory.endDictionaryItem();
factory.beginDictionaryItem("U");
factory << WrapString(m_U);
factory.endDictionaryItem();
if (m_R == 6)
{
factory.beginDictionaryItem("OE");
factory << WrapString(m_OE);
factory.endDictionaryItem();
factory.beginDictionaryItem("UE");
factory << WrapString(m_UE);
factory.endDictionaryItem();
}
factory.beginDictionaryItem("P");
factory << PDFInteger(int32_t(m_permissions));
factory.endDictionaryItem();
if (m_R == 6)
{
factory.beginDictionaryItem("Perms");
factory << WrapString(m_Perms);
factory.endDictionaryItem();
}
if (m_V == 4 || m_V == 5)
{
factory.beginDictionaryItem("EncryptMetadata");
factory << m_encryptMetadata;
factory.endDictionaryItem();
}
factory.endDictionary();
return factory.takeObject();
}
QByteArray PDFStandardSecurityHandler::createFileEncryptionKey(const QByteArray& password) const
{
QByteArray result;
switch (m_R)
{
case 2:
case 3:
case 4:
{
std::array<uint8_t, 32> paddedPassword = createPaddedPassword32(password);
uint32_t transformedPermissions = qToLittleEndian(m_permissions);
MD5_CTX context = { };
MD5_Init(&context);
MD5_Update(&context, paddedPassword.data(), paddedPassword.size());
MD5_Update(&context, m_O.constData(), m_O.size());
MD5_Update(&context, &transformedPermissions, sizeof(transformedPermissions));
MD5_Update(&context, m_ID.constData(), m_ID.size());
if (!m_encryptMetadata)
{
constexpr uint32_t value = 0xFFFFFFFF;
MD5_Update(&context, &value, sizeof(value));
}
std::array<uint8_t, MD5_DIGEST_LENGTH> fileEncryptionKey = { };
MD5_Final(fileEncryptionKey.data(), &context);
const int keyByteLength = m_keyLength / 8;
if (keyByteLength > MD5_DIGEST_LENGTH)
{
throw PDFException(PDFTranslationContext::tr("Encryption key length (%1) exceeded maximal value of %2.").arg(keyByteLength).arg(MD5_DIGEST_LENGTH));
}
if (m_R >= 3)
{
for (int i = 0; i < 50; ++i)
{
MD5_Init(&context);
MD5_Update(&context, fileEncryptionKey.data(), keyByteLength);
MD5_Final(fileEncryptionKey.data(), &context);
}
}
result.resize(keyByteLength);
std::copy_n(fileEncryptionKey.cbegin(), keyByteLength, result.begin());
break;
}
case 5:
case 6:
{
// This function must not be called with revision 5/6
Q_ASSERT(false);
break;
}
default:
{
throw PDFException(PDFTranslationContext::tr("Revision %1 of standard security handler is not supported.").arg(m_R));
}
}
return result;
}
QByteArray PDFStandardSecurityHandler::createEntryValueU_r234(const QByteArray& fileEncryptionKey) const
{
QByteArray result;
switch (m_R)
{
case 2:
{
RC4_KEY key = { };
RC4_set_key(&key, fileEncryptionKey.size(), convertByteArrayToUcharPtr(fileEncryptionKey));
result.resize(static_cast<int>(PDFPasswordPadding.size()));
RC4(&key, PDFPasswordPadding.size(), PDFPasswordPadding.data(), convertByteArrayToUcharPtr(result));
break;
}
case 3:
case 4:
{
std::array<uint8_t, MD5_DIGEST_LENGTH> hash = { };
MD5_CTX context = { };
MD5_Init(&context);
MD5_Update(&context, PDFPasswordPadding.data(), PDFPasswordPadding.size());
MD5_Update(&context, m_ID.data(), m_ID.size());
MD5_Final(hash.data(), &context);
RC4_KEY key = { };
RC4_set_key(&key, fileEncryptionKey.size(), convertByteArrayToUcharPtr(fileEncryptionKey));
std::array<uint8_t, MD5_DIGEST_LENGTH> encryptedHash = { };
std::array<uint8_t, MD5_DIGEST_LENGTH> targetBuffer = { };
RC4(&key, hash.size(), hash.data(), encryptedHash.data());
QByteArray transformedKey = fileEncryptionKey;
for (int i = 1; i <= 19; ++i)
{
for (int j = 0, keySize = fileEncryptionKey.size(); j < keySize; ++j)
{
transformedKey[j] = static_cast<uint8_t>(fileEncryptionKey[j]) ^ static_cast<uint8_t>(i);
}
RC4_set_key(&key, transformedKey.size(), convertByteArrayToUcharPtr(transformedKey));
RC4(&key, encryptedHash.size(), encryptedHash.data(), targetBuffer.data());
encryptedHash = targetBuffer;
}
// We do a hack here. In the PDF's specification, it is written, that arbitrary 16 bytes
// are appended to the 16 bytes result. We use the last 16 bytes of the U entry, because we
// want to compare byte arrays entirely (otherwise we must compare only 16 bytes to authenticate
// user password).
result = m_U;
result.detach();
if (result.size() != 32)
{
// In case of error, we resize it to correct size. We can't assume, that m_U has correct length.
result.resize(32);
}
std::copy_n(encryptedHash.begin(), encryptedHash.size(), result.begin());
break;
}
default:
{
throw PDFException(PDFTranslationContext::tr("Revision %1 of standard security handler is not supported.").arg(m_R));
}
}
return result;
}
QByteArray PDFStandardSecurityHandler::createUserPasswordFromOwnerPassword(const QByteArray& password) const
{
QByteArray result;
std::array<uint8_t, 32> paddedPassword = createPaddedPassword32(password);
std::array<uint8_t, MD5_DIGEST_LENGTH> hash;
MD5_CTX context = { };
MD5_Init(&context);
MD5_Update(&context, paddedPassword.data(), paddedPassword.size());
MD5_Final(hash.data(), &context);
const int keyByteLength = m_keyLength / 8;
if (keyByteLength > MD5_DIGEST_LENGTH)
{
throw PDFException(PDFTranslationContext::tr("Encryption key length (%1) exceeded maximal value of %2.").arg(keyByteLength).arg(MD5_DIGEST_LENGTH));
}
if (m_R >= 3)
{
for (int i = 0; i < 50; ++i)
{
MD5_Init(&context);
MD5_Update(&context, hash.data(), keyByteLength);
MD5_Final(hash.data(), &context);
}
}
switch (m_R)
{
case 2:
{
RC4_KEY key = { };
RC4_set_key(&key, keyByteLength, hash.data());
result.resize(m_O.size());
RC4(&key, m_O.size(), convertByteArrayToUcharPtr(m_O), convertByteArrayToUcharPtr(result));
break;
}
case 3:
case 4:
{
QByteArray buffer = m_O;
QByteArray transformedKey;
transformedKey.resize(keyByteLength);
std::copy_n(hash.data(), keyByteLength, transformedKey.data());
for (int i = 19; i >= 0; --i)
{
for (int j = 0, keySize = transformedKey.size(); j < keySize; ++j)
{
transformedKey[j] = static_cast<uint8_t>(hash[j]) ^ static_cast<uint8_t>(i);
}
RC4_KEY key = { };
RC4_set_key(&key, transformedKey.size(), convertByteArrayToUcharPtr(transformedKey));
RC4(&key, buffer.size(), convertByteArrayToUcharPtr(buffer), convertByteArrayToUcharPtr(buffer));
}
result = buffer;
break;
}
default:
{
throw PDFException(PDFTranslationContext::tr("Revision %1 of standard security handler is not supported.").arg(m_R));
}
}
return result;
}
std::array<uint8_t, 32> PDFStandardSecurityHandler::createPaddedPassword32(const QByteArray& password) const
{
std::array<uint8_t, 32> result = { };
int copiedBytes = qMin<int>(static_cast<int>(result.size()), password.size());
auto it = result.begin();
for (int i = 0; i < copiedBytes; ++i)
{
*it++ = static_cast<uint8_t>(password[i]);
}
auto itPadding = PDFPasswordPadding.cbegin();
for (; it != result.cend();)
{
Q_ASSERT(itPadding != PDFPasswordPadding.cend());
*it++ = *itPadding++;
}
return result;
}
QByteArray PDFStandardSecurityHandler::createHash_r6(const QByteArray& input, const QByteArray& inputPassword, bool useUserKey) const
{
QByteArray result;
// First compute sha-256 digest of the input
std::array<uint8_t, SHA256_DIGEST_LENGTH> inputDigest = { };
SHA256(convertByteArrayToUcharPtr(input), input.size(), inputDigest.data());
std::vector<uint8_t> K(inputDigest.cbegin(), inputDigest.cend());
// Fill the user key, if we use it
std::vector<uint8_t> userKey;
if (useUserKey)
{
userKey.resize(m_U.size());
std::copy_n(m_U.constData(), m_U.size(), userKey.begin());
}
const size_t userKeySize = userKey.size();
// Fill the input password
std::vector<uint8_t> password(inputPassword.constData(), inputPassword.constData() + inputPassword.size());
const size_t passwordSize = password.size();
std::vector<uint8_t> K1;
std::vector<uint8_t> E;
int round = 0;
while (round < 64 || round < E.back() + 32)
{
const size_t blockCount = 64;
const size_t KSize = K.size();
const size_t sequenceSize = passwordSize + KSize + userKeySize;
const size_t totalSize = blockCount * sequenceSize;
// Resize the arrays
K1.resize(totalSize);
E.resize(totalSize);
// a) fill the input array K1 with data
auto it = K1.begin();
for (size_t i = 0; i < blockCount; ++i)
{
std::copy_n(password.cbegin(), passwordSize, it);
std::advance(it, passwordSize);
std::copy_n(K.cbegin(), KSize, it);
std::advance(it, KSize);
std::copy_n(userKey.cbegin(), userKeySize, it);
std::advance(it, userKeySize);
}
Q_ASSERT(it == K1.cend());
Q_ASSERT(K.size() >= 32);
// b) encrypt K1 with AES-128 in CBC mode, first 16 bytes of K is key,
// second 16 bytes in K is initialization vector for AES algorithm.
AES_KEY key = { };
AES_set_encrypt_key(K.data(), 128, &key);
AES_cbc_encrypt(K1.data(), E.data(), K1.size(), &key, K.data() + 16, AES_ENCRYPT);
// c) we take first 16 bytes from E as unsigned 128 bit big-endian integer and compute
// remainder modulo 3. Then we decide which SHA function we will use.
// We can't directly modulo 128 bit unsigned number, because we do not have 128 bit arithmetic (yet).
// We will use following trick from https://math.stackexchange.com/questions/2727954/bit-representation-and-divisibility-by-3
//
// 2^n mod 3 = 2 for n = 1, 3, 5, 7, 9, ...
// 2^n mod 3 = 1 for n = 0, 2, 4, 6, 8, ...
//
// Also, it doesn't matter the endianity of the numbers, becase for example, when we change endianity of 16 bit
// numbers, then bits 0-7 became 8-15, so even/odd bits become also even/odd.
int remainderAccumulator = 0;
for (size_t i = 0; i < 16; ++i)
{
uint8_t byte = E[i];
int currentRemainder = 1;
for (uint8_t i = 0; i < 8; ++i)
{
if ((byte >> i) & 1)
{
remainderAccumulator += currentRemainder;
}
// We alternate the remainder 1, 2, 1, 2, 1, 2, ...
currentRemainder = 3 - currentRemainder;
}
}
remainderAccumulator = remainderAccumulator % 3;
// d) according to the remainder, decide, which function we will use
switch (remainderAccumulator)
{
case 0:
{
K.resize(SHA256_DIGEST_LENGTH);
SHA256(E.data(), E.size(), K.data());
break;
}
case 1:
{
K.resize(SHA384_DIGEST_LENGTH);
SHA384(E.data(), E.size(), K.data());
break;
}
case 2:
{
K.resize(SHA512_DIGEST_LENGTH);
SHA512(E.data(), E.size(), K.data());
break;
}
default:
{
// Invalid value, can't occur
Q_ASSERT(false);
break;
}
}
++round;
}
Q_ASSERT(K.size() >= 32);
// Clamp result to 32 bytes
result.resize(32);
std::copy_n(K.data(), 32, result.data());
return result;
}
PDFStandardSecurityHandler::UserOwnerData_r6 PDFStandardSecurityHandler::parseParts(const QByteArray& data) const
{
UserOwnerData_r6 result;
Q_ASSERT(data.size() == 48);
result.hash = data.left(32);
result.validationSalt = data.mid(32, 8);
result.keySalt = data.mid(40, 8);
return result;
}
QByteArray PDFStandardSecurityHandler::adjustPassword(const QString& password, int revision)
{
QByteArray result;
switch (revision)
{
case 2:
case 3:
case 4:
{
// According to the PDF specification, convert string to PDFDocEncoding encoding
result = PDFEncoding::convertToEncoding(password, PDFEncoding::Encoding::PDFDoc);
break;
}
case 5:
case 6:
{
// According to the PDF specification, use SASLprep profile for stringprep RFC 4013, please see these websites:
// - RFC 4013: https://tools.ietf.org/html/rfc4013 (SASLprep profile for stringprep algorithm)
// - RFC 3454: https://tools.ietf.org/html/rfc3454 (stringprep algorithm - preparation of internationalized strings)
//
// Note: we don't do checks according the RFC 4013, just use the mapping and normalize string in KC
QString preparedPassword;
preparedPassword.reserve(password.size());
// RFC 4013 Section 2.1, use mapping
for (const QChar character : password)
{
if (isUnicodeMappedToNothing(character.unicode()))
{
// Mapped to nothing
continue;
}
if (isUnicodeNonAsciiSpaceCharacter(character.unicode()))
{
// Map to space character
preparedPassword += QChar(QChar::Space);
}
else
{
preparedPassword += character;
}
}
// RFC 4013, Section 2.2, normalization to KC
preparedPassword = preparedPassword.normalized(QString::NormalizationForm_KC);
// We don't do other checks. We will transform password to the UTF-8 encoding
// and according the PDF specification, we take only first 127 characters.
result = preparedPassword.toUtf8().left(127);
}
default:
break;
}
return result;
}
bool PDFStandardSecurityHandler::isUnicodeNonAsciiSpaceCharacter(ushort unicode)
{
switch (unicode)
{
case 0x00A0:
case 0x1680:
case 0x2000:
case 0x2001:
case 0x2002:
case 0x2003:
case 0x2004:
case 0x2005:
case 0x2006:
case 0x2007:
case 0x2008:
case 0x2009:
case 0x200A:
case 0x200B:
case 0x202F:
case 0x205F:
case 0x3000:
return true;
default:
return false;
}
}
bool PDFStandardSecurityHandler::isUnicodeMappedToNothing(ushort unicode)
{
switch (unicode)
{
case 0x00AD:
case 0x034F:
case 0x1806:
case 0x180B:
case 0x180C:
case 0x180D:
case 0x200B:
case 0x200C:
case 0x200D:
return true;
default:
return false;
}
}
PDFSecurityHandlerPointer PDFSecurityHandlerFactory::createSecurityHandler(const SecuritySettings& settings)
{
if (settings.algorithm == Algorithm::None)
{
return PDFSecurityHandlerPointer(new PDFNoneSecurityHandler);
}
// Jakub Melka: create standard security handler, with given settings
PDFStandardSecurityHandler* handler = new PDFStandardSecurityHandler();
handler->m_ID = settings.id;
const bool isEncryptingEmbeddedFilesOnly = settings.encryptContents == EncryptContents::EmbeddedFiles;
switch (settings.algorithm)
{
case RC4:
{
handler->m_V = 4;
handler->m_keyLength = 128;
CryptFilter defaultFilter;
defaultFilter.type = CryptFilterType::V2;
defaultFilter.authEvent = !isEncryptingEmbeddedFilesOnly ? AuthEvent::DocOpen : AuthEvent::EFOpen;
defaultFilter.keyLength = handler->m_keyLength / 8;
handler->m_filterDefault = defaultFilter;
break;
}
case AES_128:
{
handler->m_V = 4;
handler->m_keyLength = 128;
CryptFilter defaultFilter;
defaultFilter.type = CryptFilterType::AESV2;
defaultFilter.authEvent = !isEncryptingEmbeddedFilesOnly ? AuthEvent::DocOpen : AuthEvent::EFOpen;
defaultFilter.keyLength = handler->m_keyLength / 8;
handler->m_filterDefault = defaultFilter;
break;
}
case AES_256:
{
handler->m_V = 5;
handler->m_keyLength = 256;
CryptFilter defaultFilter;
defaultFilter.type = CryptFilterType::AESV3;
defaultFilter.authEvent = !isEncryptingEmbeddedFilesOnly ? AuthEvent::DocOpen : AuthEvent::EFOpen;
defaultFilter.keyLength = handler->m_keyLength / 8;
handler->m_filterDefault = defaultFilter;
break;
}
default:
Q_ASSERT(false);
break;
}
CryptFilter identityFilter;
identityFilter.type = CryptFilterType::Identity;
switch (settings.encryptContents)
{
case All:
handler->m_filterStrings = handler->m_filterDefault;
handler->m_filterStreams = handler->m_filterDefault;
handler->m_filterEmbeddedFiles = handler->m_filterDefault;
handler->m_encryptMetadata = true;
break;
case AllExceptMetadata:
handler->m_filterStrings = handler->m_filterDefault;
handler->m_filterStreams = handler->m_filterDefault;
handler->m_filterEmbeddedFiles = handler->m_filterDefault;
handler->m_encryptMetadata = false;
break;
case EmbeddedFiles:
handler->m_filterStrings = identityFilter;
handler->m_filterStreams = identityFilter;
handler->m_filterEmbeddedFiles = handler->m_filterDefault;
handler->m_encryptMetadata = false;
break;
default:
Q_ASSERT(false);
break;
}
handler->m_cryptFilters["StdCF"] = handler->m_filterDefault;
handler->m_R = getRevisionFromAlgorithm(settings.algorithm);
handler->m_permissions = settings.permissions | 0xFFFFF000;
QByteArray adjustedOwnerPassword = handler->adjustPassword(settings.ownerPassword, handler->m_R);
QByteArray adjustedUserPassword = handler->adjustPassword(settings.userPassword, handler->m_R);
// Generate encryption entries
switch (handler->m_R)
{
case 2:
case 3:
case 4:
{
// Trick for computing "O" entry for revisions 2,3,4: in O entry, there is stored
// user password encrypted by owner password. Because RC4 cipher is symmetric, we
// can store user password in "O" entry and then use standard function to retrieve
// user password, which in fact will be encrypted user password.
std::array<uint8_t, 32> paddedUserPasswordArray = handler->createPaddedPassword32(adjustedUserPassword);
QByteArray paddedUserPassword;
paddedUserPassword.resize(int(paddedUserPasswordArray.size()));
std::copy(paddedUserPasswordArray.cbegin(), paddedUserPasswordArray.cend(), paddedUserPassword.data());
handler->m_O = paddedUserPassword;
QByteArray entryO = handler->createUserPasswordFromOwnerPassword(adjustedOwnerPassword);
handler->m_O = entryO;
Q_ASSERT(handler->createUserPasswordFromOwnerPassword(adjustedOwnerPassword) == paddedUserPassword);
handler->m_U.resize(32);
QRandomGenerator randomNumberGenerator = QRandomGenerator::securelySeeded();
for (int i = 0; i < handler->m_U.size(); ++i)
{
handler->m_U[i] = char(randomNumberGenerator.generate());
}
QByteArray fileEncryptionKey = handler->createFileEncryptionKey(paddedUserPassword);
QByteArray U = handler->createEntryValueU_r234(fileEncryptionKey);
handler->m_U = U;
break;
}
case 6:
{
PDFStandardSecurityHandler::UserOwnerData_r6 userData;
PDFStandardSecurityHandler::UserOwnerData_r6 ownerData;
QRandomGenerator randomNumberGenerator = QRandomGenerator::securelySeeded();
// Generate file encryption key
handler->m_authorizationData.fileEncryptionKey = generateRandomByteArray(randomNumberGenerator, 32);
handler->m_authorizationData.authorizationResult = PDFSecurityHandler::AuthorizationResult::OwnerAuthorized;
// Compute m_U entry
userData.keySalt = generateRandomByteArray(randomNumberGenerator, 8);
userData.validationSalt = generateRandomByteArray(randomNumberGenerator, 8);
userData.hash = handler->createHash_r6(adjustedUserPassword + userData.validationSalt, adjustedUserPassword, false);
handler->m_U = userData.hash + userData.validationSalt + userData.keySalt;
// Compute m_UE entry
QByteArray userFileEncryptionKeyInputData = adjustedUserPassword + userData.keySalt;
QByteArray userFileEncryptionKey = handler->createHash_r6(userFileEncryptionKeyInputData, adjustedUserPassword, false);
Q_ASSERT(userFileEncryptionKey.size() == 32);
AES_KEY userKey = { };
AES_set_encrypt_key(convertByteArrayToUcharPtr(userFileEncryptionKey), userFileEncryptionKey.size() * 8, &userKey);
unsigned char aesUserInitializationVector[AES_BLOCK_SIZE] = { };
handler->m_UE.resize(handler->m_authorizationData.fileEncryptionKey.size());
unsigned char* userInputBuffer = convertByteArrayToUcharPtr(handler->m_authorizationData.fileEncryptionKey);
unsigned char* userTargetBuffer = convertByteArrayToUcharPtr(handler->m_UE);
AES_cbc_encrypt(userInputBuffer, userTargetBuffer, handler->m_UE.size(), &userKey, aesUserInitializationVector, AES_ENCRYPT);
// Compute m_O entry
ownerData.keySalt = generateRandomByteArray(randomNumberGenerator, 8);
ownerData.validationSalt = generateRandomByteArray(randomNumberGenerator, 8);
ownerData.hash = handler->createHash_r6(adjustedOwnerPassword + ownerData.validationSalt + handler->m_U, adjustedOwnerPassword, true);
handler->m_O = ownerData.hash + ownerData.validationSalt + ownerData.keySalt;
// Compute m_OE entry
QByteArray ownerFileEncryptionKeyInputData = adjustedOwnerPassword + ownerData.keySalt + handler->m_U;
QByteArray ownerFileEncryptionKey = handler->createHash_r6(ownerFileEncryptionKeyInputData, adjustedOwnerPassword, true);
AES_KEY ownerKey = { };
AES_set_encrypt_key(convertByteArrayToUcharPtr(ownerFileEncryptionKey), ownerFileEncryptionKey.size() * 8, &ownerKey);
unsigned char aesOwnerInitializationVector[AES_BLOCK_SIZE] = { };
handler->m_OE.resize(handler->m_authorizationData.fileEncryptionKey.size());
unsigned char* ownerInputBuffer = convertByteArrayToUcharPtr(handler->m_authorizationData.fileEncryptionKey);
unsigned char* ownerTargetBuffer = convertByteArrayToUcharPtr(handler->m_OE);
AES_cbc_encrypt(ownerInputBuffer, ownerTargetBuffer, handler->m_OE.size(), &ownerKey, aesOwnerInitializationVector, AES_ENCRYPT);
// Perms entry
handler->m_Perms = QByteArray(AES_BLOCK_SIZE, char(0));
unsigned char* permsData = convertByteArrayToUcharPtr(handler->m_Perms);
permsData[0] = handler->m_permissions & 0xFF;
permsData[1] = (handler->m_permissions >> 8) & 0xFF;
permsData[2] = (handler->m_permissions >> 16) & 0xFF;
permsData[3] = (handler->m_permissions >> 24) & 0xFF;
permsData[4] = 0xFF;
permsData[5] = 0xFF;
permsData[6] = 0xFF;
permsData[7] = 0xFF;
permsData[8] = handler->m_encryptMetadata ? 'T' : 'F';
permsData[9] = 'a';
permsData[10] = 'd';
permsData[11] = 'b';
permsData[12] = randomNumberGenerator.generate() & 0xFF;
permsData[13] = randomNumberGenerator.generate() & 0xFF;
permsData[14] = randomNumberGenerator.generate() & 0xFF;
permsData[15] = randomNumberGenerator.generate() & 0xFF;
Q_ASSERT(handler->m_Perms.size() == AES_BLOCK_SIZE);
AES_KEY key = { };
AES_set_encrypt_key(convertByteArrayToUcharPtr(handler->m_authorizationData.fileEncryptionKey), handler->m_authorizationData.fileEncryptionKey.size() * 8, &key);
AES_ecb_encrypt(convertByteArrayToUcharPtr(handler->m_Perms), convertByteArrayToUcharPtr(handler->m_Perms), &key, AES_ENCRYPT);
break;
}
default:
{
Q_ASSERT(false);
break;
}
}
bool firstTry = true;
handler->authenticate([&settings, &firstTry](bool* b) { *b = firstTry; firstTry = false; return settings.ownerPassword; }, true);
Q_ASSERT(handler->getAuthorizationResult() == PDFSecurityHandler::AuthorizationResult::OwnerAuthorized);
return PDFSecurityHandlerPointer(handler);
}
int PDFSecurityHandlerFactory::getPasswordOptimalEntropy()
{
return 128;
}
int PDFSecurityHandlerFactory::getPasswordEntropy(const QString& password, Algorithm algorithm)
{
if (algorithm == None)
{
return 0;
}
QByteArray adjustedPassword = PDFStandardSecurityHandler::adjustPassword(password, getRevisionFromAlgorithm(algorithm));
if (adjustedPassword.isEmpty())
{
return 0;
}
const int length = adjustedPassword.length();
std::sort(adjustedPassword.begin(), adjustedPassword.end());
int charCount = 0;
char lastChar = adjustedPassword.front();
PDFReal entropy = 0.0;
for (int i = 0; i < length; ++i)
{
const char currentChar = adjustedPassword[i];
if (currentChar == lastChar)
{
++charCount;
}
else
{
const PDFReal probability = PDFReal(charCount) / PDFReal(length);
entropy += -probability * std::log2(probability);
charCount = 1;
lastChar = currentChar;
}
}
// Jakub Melka: last character
const PDFReal probability = PDFReal(charCount) / PDFReal(length);
entropy += -probability * std::log2(probability);
return entropy * length;
}
int PDFSecurityHandlerFactory::getRevisionFromAlgorithm(Algorithm algorithm)
{
switch (algorithm)
{
case None:
return 0;
case RC4:
return 4;
case AES_128:
return 4;
case AES_256:
return 6;
default:
Q_ASSERT(false);
break;
}
return 0;
}
QByteArray PDFSecurityHandlerFactory::generateRandomByteArray(QRandomGenerator& generator, int size)
{
QByteArray ba;
ba.reserve(size);
for (int i = 0; i < size; ++i)
{
ba.push_back(static_cast<char>(generator.generate()));
}
return ba;
}
bool PDFSecurityHandlerFactory::validate(const SecuritySettings& settings, QString* errorMessage)
{
switch (settings.algorithm)
{
case pdf::PDFSecurityHandlerFactory::RC4:
case pdf::PDFSecurityHandlerFactory::AES_128:
{
QString invalidCharacters;
if (!PDFEncoding::canConvertToEncoding(settings.userPassword, PDFEncoding::Encoding::PDFDoc, &invalidCharacters))
{
if (errorMessage)
{
Q_ASSERT(!invalidCharacters.isEmpty());
*errorMessage = tr("User password contains invalid characters: %1.").arg(invalidCharacters);
}
return false;
}
if (!PDFEncoding::canConvertToEncoding(settings.ownerPassword, PDFEncoding::Encoding::PDFDoc, &invalidCharacters))
{
if (errorMessage)
{
Q_ASSERT(!invalidCharacters.isEmpty());
*errorMessage = tr("Owner password contains invalid characters: %1.").arg(invalidCharacters);
}
return false;
}
break;
}
case pdf::PDFSecurityHandlerFactory::None:
case pdf::PDFSecurityHandlerFactory::AES_256:
break;
default:
Q_ASSERT(false);
break;
}
return true;
}
} // namespace pdf