src/utils/csprng.hpp

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/**
 * @file
 * This file includes definition for cryptographically secure pseudorandom number generator utilities.
 */

#ifndef OTBR_UTILS_CSPRNG_HPP_
#define OTBR_UTILS_CSPRNG_HPP_

#include <common/types.hpp>

#include <mbedtls/ctr_drbg.h>
#include <mbedtls/entropy.h>

namespace otbr {

class Csprng
{
public:
    /**
     * Gets the singleton instance of the generator.
     */
    static Csprng &GetInstance(void);

    /**
     * Fills a given buffer with cryptographically secure random bytes.
     *
     * @param[out] aBuffer  A pointer to a buffer to fill with the random bytes. Must not be NULL.
     * @param[in]  aSize    Size of buffer (number of bytes to fill).
     *
     * @retval OTBR_ERROR_NONE           The bytes are successfully generated.
     * @retval OTBR_ERROR_INVALID_STATE  The generation failed because of some internal state.
     * @retval OTBR_ERROR_INVALID_ARGS   @p aBuffer is NULL and @p aSize is not 0.
     */
    otbrError RandomGet(uint8_t *aBuffer, uint16_t aSize);

private:
    Csprng(void);
    ~Csprng(void);

    mbedtls_entropy_context  mEntropyContext;
    mbedtls_ctr_drbg_context mCtrDrbgContext;

    bool mInitialized;
};

} // namespace otbr

#endif // OTBR_UTILS_CSPRNG_HPP_