// default.cpp - written and placed in the public domain by Wei Dai
#include "pch.h"
#include "default.h"
#include "queue.h"
#include <time.h>
#include <memory>
NAMESPACE_BEGIN(CryptoPP)
static const unsigned int MASH_ITERATIONS = 200;
static const unsigned int SALTLENGTH = 8;
static const unsigned int BLOCKSIZE = Default_BlockCipher::Encryption::BLOCKSIZE;
static const unsigned int KEYLENGTH = Default_BlockCipher::Encryption::DEFAULT_KEYLENGTH;
// The purpose of this function Mash() is to take an arbitrary length input
// string and *deterministicly* produce an arbitrary length output string such
// that (1) it looks random, (2) no information about the input is
// deducible from it, and (3) it contains as much entropy as it can hold, or
// the amount of entropy in the input string, whichever is smaller.
static void Mash(const byte *in, size_t inLen, byte *out, size_t outLen, int iterations)
{
if (BytePrecision(outLen) > 2)
throw InvalidArgument("Mash: output legnth too large");
size_t bufSize = RoundUpToMultipleOf(outLen, (size_t)DefaultHashModule::DIGESTSIZE);
byte b[2];
SecByteBlock buf(bufSize);
SecByteBlock outBuf(bufSize);
DefaultHashModule hash;
unsigned int i;
for(i=0; i<outLen; i+=DefaultHashModule::DIGESTSIZE)
{
b[0] = (byte) (i >> 8);
b[1] = (byte) i;
hash.Update(b, 2);
hash.Update(in, inLen);
hash.Final(outBuf+i);
}
while (iterations-- > 1)
{
memcpy(buf, outBuf, bufSize);
for (i=0; i<bufSize; i+=DefaultHashModule::DIGESTSIZE)
{
b[0] = (byte) (i >> 8);
b[1] = (byte) i;
hash.Update(b, 2);
hash.Update(buf, bufSize);
hash.Final(outBuf+i);
}
}
memcpy(out, outBuf, outLen);
}
static void GenerateKeyIV(const byte *passphrase, size_t passphraseLength, const byte *salt, size_t saltLength, byte *key, byte *IV)
{
SecByteBlock temp(passphraseLength+saltLength);
memcpy(temp, passphrase, passphraseLength);
memcpy(temp+passphraseLength, salt, saltLength);
SecByteBlock keyIV(KEYLENGTH+BLOCKSIZE);
Mash(temp, passphraseLength + saltLength, keyIV, KEYLENGTH+BLOCKSIZE, MASH_ITERATIONS);
memcpy(key, keyIV, KEYLENGTH);
memcpy(IV, keyIV+KEYLENGTH, BLOCKSIZE);
}
// ********************************************************
DefaultEncryptor::DefaultEncryptor(const char *passphrase, BufferedTransformation *attachment)
: ProxyFilter(NULL, 0, 0, attachment), m_passphrase((const byte *)passphrase, strlen(passphrase))
{
}
DefaultEncryptor::DefaultEncryptor(const byte *passphrase, size_t passphraseLength, BufferedTransformation *attachment)
: ProxyFilter(NULL, 0, 0, attachment), m_passphrase(passphrase, passphraseLength)
{
}
void DefaultEncryptor::FirstPut(const byte *)
{
// VC60 workaround: __LINE__ expansion bug
CRYPTOPP_COMPILE_ASSERT_INSTANCE(SALTLENGTH <= DefaultHashModule::DIGESTSIZE, 1);
CRYPTOPP_COMPILE_ASSERT_INSTANCE(BLOCKSIZE <= DefaultHashModule::DIGESTSIZE, 2);
SecByteBlock salt(DefaultHashModule::DIGESTSIZE), keyCheck(DefaultHashModule::DIGESTSIZE);
DefaultHashModule hash;
// use hash(passphrase | time | clock) as salt
hash.Update(m_passphrase, m_passphrase.size());
time_t t=time(0);
hash.Update((byte *)&t, sizeof(t));
clock_t c=clock();
hash.Update((byte *)&c, sizeof(c));
hash.Final(salt);
// use hash(passphrase | salt) as key check
hash.Update(m_passphrase, m_passphrase.size());
hash.Update(salt, SALTLENGTH);
hash.Final(keyCheck);
AttachedTransformation()->Put(salt, SALTLENGTH);
// mash passphrase and salt together into key and IV
SecByteBlock key(KEYLENGTH);
SecByteBlock IV(BLOCKSIZE);
GenerateKeyIV(m_passphrase, m_passphrase.size(), salt, SALTLENGTH, key, IV);
m_cipher.SetKeyWithIV(key, key.size(), IV);
SetFilter(new StreamTransformationFilter(m_cipher));
m_filter->Put(keyCheck, BLOCKSIZE);
}
void DefaultEncryptor::LastPut(const byte *inString, size_t length)
{
m_filter->MessageEnd();
}
// ********************************************************
DefaultDecryptor::DefaultDecryptor(const char *p, BufferedTransformation *attachment, bool throwException)
: ProxyFilter(NULL, SALTLENGTH+BLOCKSIZE, 0, attachment)
, m_state(WAITING_FOR_KEYCHECK)
, m_passphrase((const byte *)p, strlen(p))
, m_throwException(throwException)
{
}
DefaultDecryptor::DefaultDecryptor(const byte *passphrase, size_t passphraseLength, BufferedTransformation *attachment, bool throwException)
: ProxyFilter(NULL, SALTLENGTH+BLOCKSIZE, 0, attachment)
, m_state(WAITING_FOR_KEYCHECK)
, m_passphrase(passphrase, passphraseLength)
, m_throwException(throwException)
{
}
void DefaultDecryptor::FirstPut(const byte *inString)
{
CheckKey(inString, inString+SALTLENGTH);
}
void DefaultDecryptor::LastPut(const byte *inString, size_t length)
{
if (m_filter.get() == NULL)
{
m_state = KEY_BAD;
if (m_throwException)
throw KeyBadErr();
}
else
{
m_filter->MessageEnd();
m_state = WAITING_FOR_KEYCHECK;
}
}
void DefaultDecryptor::CheckKey(const byte *salt, const byte *keyCheck)
{
SecByteBlock check(STDMAX((unsigned int)2*BLOCKSIZE, (unsigned int)DefaultHashModule::DIGESTSIZE));
DefaultHashModule hash;
hash.Update(m_passphrase, m_passphrase.size());
hash.Update(salt, SALTLENGTH);
hash.Final(check);
SecByteBlock key(KEYLENGTH);
SecByteBlock IV(BLOCKSIZE);
GenerateKeyIV(m_passphrase, m_passphrase.size(), salt, SALTLENGTH, key, IV);
m_cipher.SetKeyWithIV(key, key.size(), IV);
std::auto_ptr<StreamTransformationFilter> decryptor(new StreamTransformationFilter(m_cipher));
decryptor->Put(keyCheck, BLOCKSIZE);
decryptor->ForceNextPut();
decryptor->Get(check+BLOCKSIZE, BLOCKSIZE);
SetFilter(decryptor.release());
if (!VerifyBufsEqual(check, check+BLOCKSIZE, BLOCKSIZE))
{
m_state = KEY_BAD;
if (m_throwException)
throw KeyBadErr();
}
else
m_state = KEY_GOOD;
}
// ********************************************************
static DefaultMAC * NewDefaultEncryptorMAC(const byte *passphrase, size_t passphraseLength)
{
size_t macKeyLength = DefaultMAC::StaticGetValidKeyLength(16);
SecByteBlock macKey(macKeyLength);
// since the MAC is encrypted there is no reason to mash the passphrase for many iterations
Mash(passphrase, passphraseLength, macKey, macKeyLength, 1);
return new DefaultMAC(macKey, macKeyLength);
}
DefaultEncryptorWithMAC::DefaultEncryptorWithMAC(const char *passphrase, BufferedTransformation *attachment)
: ProxyFilter(NULL, 0, 0, attachment)
, m_mac(NewDefaultEncryptorMAC((const byte *)passphrase, strlen(passphrase)))
{
SetFilter(new HashFilter(*m_mac, new DefaultEncryptor(passphrase), true));
}
DefaultEncryptorWithMAC::DefaultEncryptorWithMAC(const byte *passphrase, size_t passphraseLength, BufferedTransformation *attachment)
: ProxyFilter(NULL, 0, 0, attachment)
, m_mac(NewDefaultEncryptorMAC(passphrase, passphraseLength))
{
SetFilter(new HashFilter(*m_mac, new DefaultEncryptor(passphrase, passphraseLength), true));
}
void DefaultEncryptorWithMAC::LastPut(const byte *inString, size_t length)
{
m_filter->MessageEnd();
}
// ********************************************************
DefaultDecryptorWithMAC::DefaultDecryptorWithMAC(const char *passphrase, BufferedTransformation *attachment, bool throwException)
: ProxyFilter(NULL, 0, 0, attachment)
, m_mac(NewDefaultEncryptorMAC((const byte *)passphrase, strlen(passphrase)))
, m_throwException(throwException)
{
SetFilter(new DefaultDecryptor(passphrase, m_hashVerifier=new HashVerifier(*m_mac, NULL, HashVerifier::PUT_MESSAGE), throwException));
}
DefaultDecryptorWithMAC::DefaultDecryptorWithMAC(const byte *passphrase, size_t passphraseLength, BufferedTransformation *attachment, bool throwException)
: ProxyFilter(NULL, 0, 0, attachment)
, m_mac(NewDefaultEncryptorMAC(passphrase, passphraseLength))
, m_throwException(throwException)
{
SetFilter(new DefaultDecryptor(passphrase, passphraseLength, m_hashVerifier=new HashVerifier(*m_mac, NULL, HashVerifier::PUT_MESSAGE), throwException));
}
DefaultDecryptor::State DefaultDecryptorWithMAC::CurrentState() const
{
return static_cast<const DefaultDecryptor *>(m_filter.get())->CurrentState();
}
bool DefaultDecryptorWithMAC::CheckLastMAC() const
{
return m_hashVerifier->GetLastResult();
}
void DefaultDecryptorWithMAC::LastPut(const byte *inString, size_t length)
{
m_filter->MessageEnd();
if (m_throwException && !CheckLastMAC())
throw MACBadErr();
}
NAMESPACE_END
Submit an article or tip