pwdbased.h

// pwdbased.h - written and placed in the public domain by Wei Dai

#ifndef CRYPTOPP_PWDBASED_H
#define CRYPTOPP_PWDBASED_H

#include "cryptlib.h"
#include "hmac.h"
#include "hrtimer.h"

NAMESPACE_BEGIN(CryptoPP)

//! abstract base class for password based key derivation function
class PasswordBasedKeyDerivationFunction
{
public:
        virtual size_t MaxDerivedKeyLength() const =0;
        virtual bool UsesPurposeByte() const =0;
        //! derive key from password
        /*! If timeInSeconds != 0, will iterate until time elapsed, as measured by ThreadUserTimer
                Returns actual iteration count, which is equal to iterations if timeInSeconds == 0, and not less than iterations otherwise. */
        virtual unsigned int DeriveKey(byte *derived, size_t derivedLen, byte purpose, const byte *password, size_t passwordLen, const byte *salt, size_t saltLen, unsigned int iterations, double timeInSeconds=0) const =0;
};

//! PBKDF1 from PKCS #5, T should be a HashTransformation class
template <class T>
class PKCS5_PBKDF1 : public PasswordBasedKeyDerivationFunction
{
public:
        size_t MaxDerivedKeyLength() const {return T::DIGESTSIZE;}
        bool UsesPurposeByte() const {return false;}
        // PKCS #5 says PBKDF1 should only take 8-byte salts. This implementation allows salts of any length.
        unsigned int DeriveKey(byte *derived, size_t derivedLen, byte purpose, const byte *password, size_t passwordLen, const byte *salt, size_t saltLen, unsigned int iterations, double timeInSeconds=0) const;
};

//! PBKDF2 from PKCS #5, T should be a HashTransformation class
template <class T>
class PKCS5_PBKDF2_HMAC : public PasswordBasedKeyDerivationFunction
{
public:
        size_t MaxDerivedKeyLength() const {return 0xffffffffU;}        // should multiply by T::DIGESTSIZE, but gets overflow that way
        bool UsesPurposeByte() const {return false;}
        unsigned int DeriveKey(byte *derived, size_t derivedLen, byte purpose, const byte *password, size_t passwordLen, const byte *salt, size_t saltLen, unsigned int iterations, double timeInSeconds=0) const;
};

/*
class PBKDF2Params
{
public:
        SecByteBlock m_salt;
        unsigned int m_interationCount;
        ASNOptional<ASNUnsignedWrapper<word32> > m_keyLength;
};
*/

template <class T>
unsigned int PKCS5_PBKDF1<T>::DeriveKey(byte *derived, size_t derivedLen, byte purpose, const byte *password, size_t passwordLen, const byte *salt, size_t saltLen, unsigned int iterations, double timeInSeconds) const
{
        assert(derivedLen <= MaxDerivedKeyLength());
        assert(iterations > 0 || timeInSeconds > 0);

        if (!iterations)
                iterations = 1;

        T hash;
        hash.Update(password, passwordLen);
        hash.Update(salt, saltLen);

        SecByteBlock buffer(hash.DigestSize());
        hash.Final(buffer);

        unsigned int i;
        ThreadUserTimer timer;

        if (timeInSeconds)
                timer.StartTimer();

        for (i=1; i<iterations || (timeInSeconds && (i%128!=0 || timer.ElapsedTimeAsDouble() < timeInSeconds)); i++)
                hash.CalculateDigest(buffer, buffer, buffer.size());

        memcpy(derived, buffer, derivedLen);
        return i;
}

template <class T>
unsigned int PKCS5_PBKDF2_HMAC<T>::DeriveKey(byte *derived, size_t derivedLen, byte purpose, const byte *password, size_t passwordLen, const byte *salt, size_t saltLen, unsigned int iterations, double timeInSeconds) const
{
        assert(derivedLen <= MaxDerivedKeyLength());
        assert(iterations > 0 || timeInSeconds > 0);

        if (!iterations)
                iterations = 1;

        HMAC<T> hmac(password, passwordLen);
        SecByteBlock buffer(hmac.DigestSize());
        ThreadUserTimer timer;

        unsigned int i=1;
        while (derivedLen > 0)
        {
                hmac.Update(salt, saltLen);
                unsigned int j;
                for (j=0; j<4; j++)
                {
                        byte b = byte(i >> ((3-j)*8));
                        hmac.Update(&b, 1);
                }
                hmac.Final(buffer);

                size_t segmentLen = STDMIN(derivedLen, buffer.size());
                memcpy(derived, buffer, segmentLen);

                if (timeInSeconds)
                {
                        timeInSeconds = timeInSeconds / ((derivedLen + buffer.size() - 1) / buffer.size());
                        timer.StartTimer();
                }

                for (j=1; j<iterations || (timeInSeconds && (j%128!=0 || timer.ElapsedTimeAsDouble() < timeInSeconds)); j++)
                {
                        hmac.CalculateDigest(buffer, buffer, buffer.size());
                        xorbuf(derived, buffer, segmentLen);
                }

                if (timeInSeconds)
                {
                        iterations = j;
                        timeInSeconds = 0;
                }

                derived += segmentLen;
                derivedLen -= segmentLen;
                i++;
        }

        return iterations;
}

//! PBKDF from PKCS #12, appendix B, T should be a HashTransformation class
template <class T>
class PKCS12_PBKDF : public PasswordBasedKeyDerivationFunction
{
public:
        size_t MaxDerivedKeyLength() const {return size_t(0)-1;}
        bool UsesPurposeByte() const {return true;}
        unsigned int DeriveKey(byte *derived, size_t derivedLen, byte purpose, const byte *password, size_t passwordLen, const byte *salt, size_t saltLen, unsigned int iterations, double timeInSeconds) const;
};

template <class T>
unsigned int PKCS12_PBKDF<T>::DeriveKey(byte *derived, size_t derivedLen, byte purpose, const byte *password, size_t passwordLen, const byte *salt, size_t saltLen, unsigned int iterations, double timeInSeconds) const
{
        assert(derivedLen <= MaxDerivedKeyLength());
        assert(iterations > 0 || timeInSeconds > 0);

        if (!iterations)
                iterations = 1;

        const size_t v = T::BLOCKSIZE;  // v is in bytes rather than bits as in PKCS #12
        const size_t DLen = v, SLen = RoundUpToMultipleOf(saltLen, v);
        const size_t PLen = RoundUpToMultipleOf(passwordLen, v), ILen = SLen + PLen;
        SecByteBlock buffer(DLen + SLen + PLen);
        byte *D = buffer, *S = buffer+DLen, *P = buffer+DLen+SLen, *I = S;

        memset(D, purpose, DLen);
        size_t i;
        for (i=0; i<SLen; i++)
                S[i] = salt[i % saltLen];
        for (i=0; i<PLen; i++)
                P[i] = password[i % passwordLen];


        T hash;
        SecByteBlock Ai(T::DIGESTSIZE), B(v);
        ThreadUserTimer timer;

        while (derivedLen > 0)
        {
                hash.CalculateDigest(Ai, buffer, buffer.size());

                if (timeInSeconds)
                {
                        timeInSeconds = timeInSeconds / ((derivedLen + Ai.size() - 1) / Ai.size());
                        timer.StartTimer();
                }

                for (i=1; i<iterations || (timeInSeconds && (i%128!=0 || timer.ElapsedTimeAsDouble() < timeInSeconds)); i++)
                        hash.CalculateDigest(Ai, Ai, Ai.size());

                if (timeInSeconds)
                {
                        iterations = (unsigned int)i;
                        timeInSeconds = 0;
                }

                for (i=0; i<B.size(); i++)
                        B[i] = Ai[i % Ai.size()];

                Integer B1(B, B.size());
                ++B1;
                for (i=0; i<ILen; i+=v)
                        (Integer(I+i, v) + B1).Encode(I+i, v);

                size_t segmentLen = STDMIN(derivedLen, Ai.size());
                memcpy(derived, Ai, segmentLen);
                derived += segmentLen;
                derivedLen -= segmentLen;
        }

        return iterations;
}

NAMESPACE_END

#endif

---