osrng.cpp

// osrng.cpp - originally written and placed in the public domain by Wei Dai

// Thanks to Leonard Janke for the suggestion for AutoSeededRandomPool.

#include "pch.h"
#include "config.h"

#ifndef CRYPTOPP_IMPORTS

// Win32 has CryptoAPI and <wincrypt.h>. Windows 10 and Windows Store 10 have CNG and <bcrypt.h>.
//  There's a hole for Windows Phone 8 and Windows Store 8. There is no userland RNG available.
//  Also see http://www.drdobbs.com/windows/using-c-and-com-with-winrt/240168150 and
//  http://stackoverflow.com/questions/36974545/random-numbers-for-windows-phone-8-and-windows-store-8 and
//  https://social.msdn.microsoft.com/Forums/vstudio/en-US/25b83e13-c85f-4aa1-a057-88a279ea3fd6/what-crypto-random-generator-c-code-could-use-on-wp81
#if defined(CRYPTOPP_WIN32_AVAILABLE) && !defined(OS_RNG_AVAILABLE)
# pragma message("WARNING: Compiling for Windows but an OS RNG is not available. This is likely a Windows Phone 8 or Windows Store 8 app.")
#endif

#if !defined(NO_OS_DEPENDENCE) && defined(OS_RNG_AVAILABLE)

#include "osrng.h"
#include "rng.h"

// FreeBSD links /dev/urandom -> /dev/random. It showed up when we added
// O_NOFOLLOW to harden the non-blocking generator. Use Arc4Random instead
// for a non-blocking generator. Arc4Random is cryptograhic quality prng
// based on ChaCha20. The ChaCha20 generator is seeded from /dev/random,
// so we can't completely avoid the blocking.
// https://www.freebsd.org/cgi/man.cgi?query=arc4random_buf.
#ifdef __FreeBSD__
# define DONT_USE_O_NOFOLLOW 1
# define USE_FREEBSD_ARC4RANDOM 1
# include <stdlib.h>
#endif

// Solaris links /dev/urandom -> ../devices/pseudo/random@0:urandom
// We can't access the device. Avoid O_NOFOLLOW for the platform.
#ifdef __sun
# define DONT_USE_O_NOFOLLOW 1
#endif

// And other OSes that don't define it
#ifndef O_NOFOLLOW
# define DONT_USE_O_NOFOLLOW 1
#endif

#ifdef CRYPTOPP_WIN32_AVAILABLE
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#ifndef ERROR_INCORRECT_SIZE
# define ERROR_INCORRECT_SIZE 0x000005B6
#endif
#if defined(USE_MS_CRYPTOAPI)
#include <wincrypt.h>
#ifndef CRYPT_NEWKEYSET
# define CRYPT_NEWKEYSET 0x00000008
#endif
#ifndef CRYPT_MACHINE_KEYSET
# define CRYPT_MACHINE_KEYSET 0x00000020
#endif
#elif defined(USE_MS_CNGAPI)
#include <bcrypt.h>
#ifndef BCRYPT_SUCCESS
# define BCRYPT_SUCCESS(Status) (((NTSTATUS)(Status)) >= 0)
#endif
#ifndef STATUS_INVALID_PARAMETER
# define STATUS_INVALID_PARAMETER 0xC000000D
#endif
#ifndef STATUS_INVALID_HANDLE
# define STATUS_INVALID_HANDLE 0xC0000008
#endif
#endif
#endif  // Win32

#ifdef CRYPTOPP_UNIX_AVAILABLE
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#endif

NAMESPACE_BEGIN(CryptoPP)

#if defined(NONBLOCKING_RNG_AVAILABLE) || defined(BLOCKING_RNG_AVAILABLE)
OS_RNG_Err::OS_RNG_Err(const std::string &operation)
    : Exception(OTHER_ERROR, "OS_Rng: " + operation + " operation failed with error " +
#ifdef CRYPTOPP_WIN32_AVAILABLE
        "0x" + IntToString(GetLastError(), 16)
#else
        IntToString(errno)
#endif
        )
{
}
#endif

#ifdef NONBLOCKING_RNG_AVAILABLE

#ifdef CRYPTOPP_WIN32_AVAILABLE

#if defined(USE_MS_CNGAPI)
inline DWORD NtStatusToErrorCode(NTSTATUS status)
{
    if (status == static_cast<NTSTATUS>(STATUS_INVALID_PARAMETER))
        return ERROR_INVALID_PARAMETER;
    else if (status == static_cast<NTSTATUS>(STATUS_INVALID_HANDLE))
        return ERROR_INVALID_HANDLE;
    else
        return static_cast<DWORD>(status);
}
#endif

#if defined(UNICODE) || defined(_UNICODE)
# define CRYPTOPP_CONTAINER L"Crypto++ RNG"
#else
# define CRYPTOPP_CONTAINER "Crypto++ RNG"
#endif

MicrosoftCryptoProvider::MicrosoftCryptoProvider() : m_hProvider(0)
{
#if defined(USE_MS_CRYPTOAPI)
    // See http://support.microsoft.com/en-us/kb/238187 for CRYPT_NEWKEYSET fallback strategy
    if (!CryptAcquireContext(&m_hProvider, 0, 0, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT))
    {
        const DWORD firstErr = GetLastError();
        if (!CryptAcquireContext(&m_hProvider, CRYPTOPP_CONTAINER, 0, PROV_RSA_FULL, CRYPT_NEWKEYSET /*user*/) &&
            !CryptAcquireContext(&m_hProvider, CRYPTOPP_CONTAINER, 0, PROV_RSA_FULL, CRYPT_MACHINE_KEYSET|CRYPT_NEWKEYSET))
        {
            // Set original error with original code
            SetLastError(firstErr);
            throw OS_RNG_Err("CryptAcquireContext");
        }
    }
#elif defined(USE_MS_CNGAPI)
    NTSTATUS ret = BCryptOpenAlgorithmProvider(&m_hProvider, BCRYPT_RNG_ALGORITHM, MS_PRIMITIVE_PROVIDER, 0);
    if (!(BCRYPT_SUCCESS(ret)))
    {
        // Hack... OS_RNG_Err calls GetLastError()
        SetLastError(NtStatusToErrorCode(ret));
        throw OS_RNG_Err("BCryptOpenAlgorithmProvider");
    }
#endif
}

MicrosoftCryptoProvider::~MicrosoftCryptoProvider()
{
#if defined(USE_MS_CRYPTOAPI)
    if (m_hProvider)
        CryptReleaseContext(m_hProvider, 0);
#elif defined(USE_MS_CNGAPI)
    if (m_hProvider)
        BCryptCloseAlgorithmProvider(m_hProvider, 0);
#endif
}

#endif  // CRYPTOPP_WIN32_AVAILABLE

NonblockingRng::NonblockingRng()
{
#if !defined(CRYPTOPP_WIN32_AVAILABLE) && !defined(USE_FREEBSD_ARC4RANDOM)
# ifndef DONT_USE_O_NOFOLLOW
    const int flags = O_RDONLY|O_NOFOLLOW;
# else
    const int flags = O_RDONLY;
# endif

    m_fd = open("/dev/urandom", flags);
    if (m_fd == -1)
        throw OS_RNG_Err("open /dev/urandom");

#endif
}

NonblockingRng::~NonblockingRng()
{
#if !defined(CRYPTOPP_WIN32_AVAILABLE) && !defined(USE_FREEBSD_ARC4RANDOM)
    close(m_fd);
#endif
}

void NonblockingRng::GenerateBlock(byte *output, size_t size)
{
#ifdef CRYPTOPP_WIN32_AVAILABLE
    // Acquiring a provider is expensive. Do it once and retain the reference.
# if defined(CRYPTOPP_CXX11_STATIC_INIT)
    static const MicrosoftCryptoProvider hProvider = MicrosoftCryptoProvider();
# else
    const MicrosoftCryptoProvider &hProvider = Singleton<MicrosoftCryptoProvider>().Ref();
# endif
# if defined(USE_MS_CRYPTOAPI)
    DWORD dwSize;
    CRYPTOPP_ASSERT(SafeConvert(size, dwSize));
    if (!SafeConvert(size, dwSize))
    {
        SetLastError(ERROR_INCORRECT_SIZE);
        throw OS_RNG_Err("GenerateBlock size");
    }
    BOOL ret = CryptGenRandom(hProvider.GetProviderHandle(), dwSize, output);
    CRYPTOPP_ASSERT(ret != FALSE);
    if (ret == FALSE)
        throw OS_RNG_Err("CryptGenRandom");
# elif defined(USE_MS_CNGAPI)
    ULONG ulSize;
    CRYPTOPP_ASSERT(SafeConvert(size, ulSize));
    if (!SafeConvert(size, ulSize))
    {
        SetLastError(ERROR_INCORRECT_SIZE);
        throw OS_RNG_Err("GenerateBlock size");
    }
    NTSTATUS ret = BCryptGenRandom(hProvider.GetProviderHandle(), output, ulSize, 0);
    CRYPTOPP_ASSERT(BCRYPT_SUCCESS(ret));
    if (!(BCRYPT_SUCCESS(ret)))
    {
        // Hack... OS_RNG_Err calls GetLastError()
        SetLastError(NtStatusToErrorCode(ret));
        throw OS_RNG_Err("BCryptGenRandom");
    }
# endif
#else

# if defined(USE_FREEBSD_ARC4RANDOM)
    // Cryptographic quality prng based on ChaCha20,
    // https://www.freebsd.org/cgi/man.cgi?query=arc4random_buf
    arc4random_buf(output, size);
# else
    while (size)
    {
        ssize_t len = read(m_fd, output, size);
        if (len < 0)
        {
            // /dev/urandom reads CAN give EAGAIN errors! (maybe EINTR as well)
            if (errno != EINTR && errno != EAGAIN)
                throw OS_RNG_Err("read /dev/urandom");

            continue;
        }
        output += len;
        size -= len;
    }
# endif  // USE_FREEBSD_ARC4RANDOM

#endif  // CRYPTOPP_WIN32_AVAILABLE
}

#endif  // NONBLOCKING_RNG_AVAILABLE

// *************************************************************

#ifdef BLOCKING_RNG_AVAILABLE

#ifndef CRYPTOPP_BLOCKING_RNG_FILENAME
# ifdef __OpenBSD__
#  define CRYPTOPP_BLOCKING_RNG_FILENAME "/dev/srandom"
# else
#  define CRYPTOPP_BLOCKING_RNG_FILENAME "/dev/random"
# endif
#endif

BlockingRng::BlockingRng()
{
#ifndef DONT_USE_O_NOFOLLOW
    const int flags = O_RDONLY|O_NOFOLLOW;
#else
    const int flags = O_RDONLY;
#endif

    m_fd = open(CRYPTOPP_BLOCKING_RNG_FILENAME, flags);
    if (m_fd == -1)
        throw OS_RNG_Err("open " CRYPTOPP_BLOCKING_RNG_FILENAME);
}

BlockingRng::~BlockingRng()
{
    close(m_fd);
}

void BlockingRng::GenerateBlock(byte *output, size_t size)
{
    while (size)
    {
        // on some systems /dev/random will block until all bytes
        // are available, on others it returns immediately
        ssize_t len = read(m_fd, output, size);
        if (len < 0)
        {
            // /dev/random reads CAN give EAGAIN errors! (maybe EINTR as well)
            if (errno != EINTR && errno != EAGAIN)
                throw OS_RNG_Err("read " CRYPTOPP_BLOCKING_RNG_FILENAME);

            continue;
        }

        size -= len;
        output += len;
        if (size)
            sleep(1);
    }
}

#endif  // BLOCKING_RNG_AVAILABLE

// *************************************************************

void OS_GenerateRandomBlock(bool blocking, byte *output, size_t size)
{
#ifdef NONBLOCKING_RNG_AVAILABLE
    if (blocking)
#endif
    {
#ifdef BLOCKING_RNG_AVAILABLE
        BlockingRng rng;
        rng.GenerateBlock(output, size);
#endif
    }

#ifdef BLOCKING_RNG_AVAILABLE
    if (!blocking)
#endif
    {
#ifdef NONBLOCKING_RNG_AVAILABLE
        NonblockingRng rng;
        rng.GenerateBlock(output, size);
#endif
    }
}

void AutoSeededRandomPool::Reseed(bool blocking, unsigned int seedSize)
{
    SecByteBlock seed(seedSize);
    OS_GenerateRandomBlock(blocking, seed, seedSize);
    IncorporateEntropy(seed, seedSize);
}

NAMESPACE_END

#endif  // OS_RNG_AVAILABLE

#endif  // CRYPTOPP_IMPORTS