Function fill_random_dev_random

src/unique_path.cpp:115–164

Fills buffer with cryptographically random data obtained from /dev/(u)random

//! Fills buffer with cryptographically random data obtained from /dev/(u)random
int fill_random_dev_random(void* buf, std::size_t len)
{
    boost::scope::unique_fd file;
    while (true)
    {
        file.reset(::open("/dev/urandom", O_RDONLY | O_CLOEXEC));
        if (!file)
        {
            if (errno == EINTR)
                continue;
        }

        break;
    }

    if (!file)
    {
        while (true)
        {
            file.reset(::open("/dev/random", O_RDONLY | O_CLOEXEC));
            if (!file)
            {
                const int err = errno;
                if (err == EINTR)
                    continue;
                return err;
            }

            break;
        }
    }

    std::size_t bytes_read = 0u;
    while (bytes_read < len)
    {
        ssize_t n = ::read(file.get(), buf, len - bytes_read);
        if (BOOST_UNLIKELY(n < 0))
        {
            const int err = errno;
            if (err == EINTR)
                continue;
            return err;
        }

        bytes_read += n;
        buf = static_cast< char* >(buf) + n;
    }

    return 0;
}

#if defined(BOOST_FILESYSTEM_HAS_GETRANDOM) || defined(BOOST_FILESYSTEM_HAS_GETRANDOM_SYSCALL)