Function pbkdf2

Libraries/unrar/crypt5.cpp:85–128

PBKDF2 for 32 byte key length. We generate the key for specified number of iteration count also as two supplementary values (key for checksums and password verification) for iterations+16 and iterations+32.

// of iteration count also as two supplementary values (key for checksums
// and password verification) for iterations+16 and iterations+32.
void pbkdf2(const byte *Pwd, size_t PwdLength, 
            const byte *Salt, size_t SaltLength,
            byte *Key, byte *V1, byte *V2, uint Count)
{
  const size_t MaxSalt=64;
  byte SaltData[MaxSalt+4];
  memcpy(SaltData, Salt, Min(SaltLength,MaxSalt));

  SaltData[SaltLength + 0] = 0; // Salt concatenated to 1.
  SaltData[SaltLength + 1] = 0;
  SaltData[SaltLength + 2] = 0;
  SaltData[SaltLength + 3] = 1;

  // First iteration: HMAC of password, salt and block index (1).
  byte U1[SHA256_DIGEST_SIZE];
  hmac_sha256(Pwd, PwdLength, SaltData, SaltLength + 4, U1, NULL, NULL, NULL, NULL);
  byte Fn[SHA256_DIGEST_SIZE]; // Current function value.
  memcpy(Fn, U1, sizeof(Fn)); // Function at first iteration.

  uint  CurCount[] = { Count-1, 16, 16 };
  byte *CurValue[] = { Key    , V1, V2 };
  
  sha256_context ICtxOpt,RCtxOpt;
  bool SetIOpt=false,SetROpt=false;
  
  byte U2[SHA256_DIGEST_SIZE];
  for (uint I = 0; I < 3; I++) // For output key and 2 supplementary values.
  {
    for (uint J = 0; J < CurCount[I]; J++) 
    {
      // U2 = PRF (P, U1).
      hmac_sha256(Pwd, PwdLength, U1, sizeof(U1), U2, &ICtxOpt, &SetIOpt, &RCtxOpt, &SetROpt);
      memcpy(U1, U2, sizeof(U1));
      for (uint K = 0; K < sizeof(Fn); K++) // Function ^= U.
        Fn[K] ^= U1[K];
    }
    memcpy(CurValue[I], Fn, SHA256_DIGEST_SIZE);
  }

  cleandata(SaltData, sizeof(SaltData));
  cleandata(Fn, sizeof(Fn));
  cleandata(U1, sizeof(U1));
  cleandata(U2, sizeof(U2));
}


void CryptData::SetKey50(bool Encrypt,SecPassword *Password,const wchar *PwdW,