rand.hpp

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//    OpenVPN -- An application to securely tunnel IP networks
//               over a single port, with support for SSL/TLS-based
//               session authentication and key exchange,
//               packet encryption, packet authentication, and
//               packet compression.
//
//    Copyright (C) 2012- OpenVPN Inc.
//
//    SPDX-License-Identifier: MPL-2.0 OR AGPL-3.0-only WITH openvpn3-openssl-exception
//
 
// Wrap the OpenSSL Cryptographic Random API defined in <openssl/rand.h>
// so that it can be used as the primary source of cryptographic entropy by
// the OpenVPN core.
 
#ifndef OPENVPN_OPENSSL_UTIL_RAND_H
#define OPENVPN_OPENSSL_UTIL_RAND_H
 
#include <openssl/rand.h>
 
#include <openvpn/random/randapi.hpp>
#include <openvpn/common/numeric_util.hpp>
 
namespace openvpn {
class OpenSSLRandom : public StrongRandomAPI
{
  public:
    OPENVPN_EXCEPTION(rand_error_openssl);
 
    typedef RCPtr<OpenSSLRandom> Ptr;
 
    OpenSSLRandom() = default;
 
    std::string name() const override
    {
        return "OpenSSLRandom";
    }
 
    // Fill buffer with random bytes
    void rand_bytes(unsigned char *buf, size_t size) override
    {
        if (!rndbytes(buf, size))
            throw rand_error_openssl("rand_bytes");
    }
 
    // Like rand_bytes, but don't throw exception.
    // Return true on successs, false on fail.
    bool rand_bytes_noexcept(unsigned char *buf, size_t size) override
    {
        return rndbytes(buf, size);
    }
 
  private:
    bool rndbytes(unsigned char *buf, size_t size)
    {
        return is_safe_conversion<int>(size) ? RAND_bytes(buf, static_cast<int>(size)) == 1 : false;
    }
};
} // namespace openvpn
 
#endif