Method decrypt_key

libcppcryptfs/config/cryptconfig.cpp:622–717

}

bool CryptConfig::decrypt_key(LPCTSTR password)
{

	bool bret = true;

	shared_ptr<EVP_CIPHER_CTX> context = nullptr;

	try {
		if (m_encrypted_key.size() == 0 || m_encrypted_key_salt.size() == 0 || GetMasterKeyLength() == 0)
			return false;

		LockZeroBuffer<char> pass_buf(4*MAX_PASSWORD_LEN+1, false);

		if (!pass_buf.IsLocked())
			throw (-1);

		const char *pass = unicode_to_utf8(password, pass_buf.m_buf, pass_buf.m_len-1);

		if (!pass) {
			throw (-1);
		}

		LockZeroBuffer<unsigned char> pwkey(GetMasterKeyLength(), false);

		LockZeroBuffer<unsigned char> pwkeyHKDF(GetMasterKeyLength(), false);

		if (!pwkey.IsLocked())
			throw(-1);

		if (m_HKDF && !pwkeyHKDF.IsLocked())
			throw(-1);
	
		int result = EVP_PBE_scrypt(pass, strlen(pass), &m_encrypted_key_salt[0], 
			m_encrypted_key_salt.size(), m_N, m_R, m_P, scrypt_mem(), pwkey.m_buf,
			GetMasterKeyLength());

		if (result != 1)
			throw (-1);

		unsigned char adata[8];

		const int adata_len = sizeof(adata);

		memset(adata, 0, adata_len);

		int ivlen = m_HKDF ? HKDF_MASTER_IV_LEN : ORIG_MASTER_IV_LEN;

		const int taglen = BLOCK_TAG_LEN;

		unsigned char *ciphertext = &(m_encrypted_key)[0] + ivlen;
		int ciphertext_len = (int)m_encrypted_key.size() - ivlen - taglen;
		unsigned char *tag = &(m_encrypted_key)[0] + m_encrypted_key.size() - taglen;

		unsigned char *iv = &(m_encrypted_key)[0];

		if (ciphertext_len != MASTER_KEY_LEN)
			throw (-1);