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 /**
  * \file ctr_drbg.h
  *
  * \brief    This file contains definitions and functions for the
  *           CTR_DRBG pseudorandom generator.
  *
  * CTR_DRBG is a standardized way of building a PRNG from a block-cipher
  * in counter mode operation, as defined in <em>NIST SP 800-90A:
  * Recommendation for Random Number Generation Using Deterministic Random
  * Bit Generators</em>.
  *
  * The Mbed TLS implementation of CTR_DRBG uses AES-256 (default) or AES-128
  * (if \c MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is enabled at compile time)
  * as the underlying block cipher, with a derivation function.
  *
  * The security strength as defined in NIST SP 800-90A is
  * 128 bits when AES-128 is used (\c MBEDTLS_CTR_DRBG_USE_128_BIT_KEY enabled)
  * and 256 bits otherwise, provided that #MBEDTLS_CTR_DRBG_ENTROPY_LEN is
  * kept at its default value (and not overridden in mbedtls_config.h) and that the
  * DRBG instance is set up with default parameters.
  * See the documentation of mbedtls_ctr_drbg_seed() for more
  * information.
  */
 /*
  *  Copyright The Mbed TLS Contributors
  *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
  */
 
 #ifndef MBEDTLS_CTR_DRBG_H
 #define MBEDTLS_CTR_DRBG_H
 #include "mbedtls/private_access.h"
 
 #include "mbedtls/build_info.h"
 
 /* The CTR_DRBG implementation can either directly call the low-level AES
  * module (gated by MBEDTLS_AES_C) or call the PSA API to perform AES
  * operations. Calling the AES module directly is the default, both for
  * maximum backward compatibility and because it's a bit more efficient
  * (less glue code).
  *
  * When MBEDTLS_AES_C is disabled, the CTR_DRBG module calls PSA crypto and
  * thus benefits from the PSA AES accelerator driver.
  * It is technically possible to enable MBEDTLS_CTR_DRBG_USE_PSA_CRYPTO
  * to use PSA even when MBEDTLS_AES_C is enabled, but there is very little
  * reason to do so other than testing purposes and this is not officially
  * supported.
  */
 #if !defined(MBEDTLS_AES_C)
 #define MBEDTLS_CTR_DRBG_USE_PSA_CRYPTO
 #endif
 
 #if defined(MBEDTLS_CTR_DRBG_USE_PSA_CRYPTO)
 #include "psa/crypto.h"
 #else
 #include "mbedtls/aes.h"
 #endif
 
 #include "entropy.h"
 
 #if defined(MBEDTLS_THREADING_C)
 #include "mbedtls/threading.h"
 #endif
 
 /** The entropy source failed. */
 #define MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED        -0x0034
 /** The requested random buffer length is too big. */
 #define MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG              -0x0036
 /** The input (entropy + additional data) is too large. */
 #define MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG                -0x0038
 /** Read or write error in file. */
 #define MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR                -0x003A
 
 #define MBEDTLS_CTR_DRBG_BLOCKSIZE          16 /**< The block size used by the cipher. */
 
 #if defined(MBEDTLS_CTR_DRBG_USE_128_BIT_KEY)
 #define MBEDTLS_CTR_DRBG_KEYSIZE            16
 /**< The key size in bytes used by the cipher.
  *
  * Compile-time choice: 16 bytes (128 bits)
  * because #MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is enabled.
  */
 #else
 #define MBEDTLS_CTR_DRBG_KEYSIZE            32
 /**< The key size in bytes used by the cipher.
  *
  * Compile-time choice: 32 bytes (256 bits)
  * because \c MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is disabled.
  */
 #endif
 
 #define MBEDTLS_CTR_DRBG_KEYBITS            (MBEDTLS_CTR_DRBG_KEYSIZE * 8)   /**< The key size for the DRBG operation, in bits. */
 #define MBEDTLS_CTR_DRBG_SEEDLEN            (MBEDTLS_CTR_DRBG_KEYSIZE + MBEDTLS_CTR_DRBG_BLOCKSIZE)   /**< The seed length, calculated as (counter + AES key). */
 
 /**
  * \name SECTION: Module settings
  *
  * The configuration options you can set for this module are in this section.
  * Either change them in mbedtls_config.h or define them using the compiler command
  * line.
  * \{
  */
 
 /** \def MBEDTLS_CTR_DRBG_ENTROPY_LEN
  *
  * \brief The amount of entropy used per seed by default, in bytes.
  */
 #if !defined(MBEDTLS_CTR_DRBG_ENTROPY_LEN)
 #if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
 /** This is 48 bytes because the entropy module uses SHA-512.
  */
 #define MBEDTLS_CTR_DRBG_ENTROPY_LEN        48
 
 #else /* MBEDTLS_ENTROPY_SHA512_ACCUMULATOR */
 
 /** This is 32 bytes because the entropy module uses SHA-256.
  */
 #if !defined(MBEDTLS_CTR_DRBG_USE_128_BIT_KEY)
 /** \warning To achieve a 256-bit security strength, you must pass a nonce
  *           to mbedtls_ctr_drbg_seed().
  */
 #endif /* !defined(MBEDTLS_CTR_DRBG_USE_128_BIT_KEY) */
 #define MBEDTLS_CTR_DRBG_ENTROPY_LEN        32
 #endif /* MBEDTLS_ENTROPY_SHA512_ACCUMULATOR */
 #endif /* !defined(MBEDTLS_CTR_DRBG_ENTROPY_LEN) */
 
 #if !defined(MBEDTLS_CTR_DRBG_RESEED_INTERVAL)
 #define MBEDTLS_CTR_DRBG_RESEED_INTERVAL    10000
 /**< The interval before reseed is performed by default. */
 #endif
 
 #if !defined(MBEDTLS_CTR_DRBG_MAX_INPUT)
 #define MBEDTLS_CTR_DRBG_MAX_INPUT          256
 /**< The maximum number of additional input Bytes. */
 #endif
 
 #if !defined(MBEDTLS_CTR_DRBG_MAX_REQUEST)
 #define MBEDTLS_CTR_DRBG_MAX_REQUEST        1024
 /**< The maximum number of requested Bytes per call. */
 #endif
 
 #if !defined(MBEDTLS_CTR_DRBG_MAX_SEED_INPUT)
 #define MBEDTLS_CTR_DRBG_MAX_SEED_INPUT     384
 /**< The maximum size of seed or reseed buffer in bytes. */
 #endif
 
 /** \} name SECTION: Module settings */
 
 #define MBEDTLS_CTR_DRBG_PR_OFF             0
 /**< Prediction resistance is disabled. */
 #define MBEDTLS_CTR_DRBG_PR_ON              1
 /**< Prediction resistance is enabled. */
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 #if MBEDTLS_CTR_DRBG_ENTROPY_LEN >= MBEDTLS_CTR_DRBG_KEYSIZE * 3 / 2
 /** The default length of the nonce read from the entropy source.
  *
  * This is \c 0 because a single read from the entropy source is sufficient
  * to include a nonce.
  * See the documentation of mbedtls_ctr_drbg_seed() for more information.
  */
 #define MBEDTLS_CTR_DRBG_ENTROPY_NONCE_LEN 0
 #else
 /** The default length of the nonce read from the entropy source.
  *
  * This is half of the default entropy length because a single read from
  * the entropy source does not provide enough material to form a nonce.
  * See the documentation of mbedtls_ctr_drbg_seed() for more information.
  */
 #define MBEDTLS_CTR_DRBG_ENTROPY_NONCE_LEN (MBEDTLS_CTR_DRBG_ENTROPY_LEN + 1) / 2
 #endif
 
 #if defined(MBEDTLS_CTR_DRBG_USE_PSA_CRYPTO)
 typedef struct mbedtls_ctr_drbg_psa_context {
     mbedtls_svc_key_id_t key_id;
     psa_cipher_operation_t operation;
 } mbedtls_ctr_drbg_psa_context;
 #endif
 
 /**
  * \brief          The CTR_DRBG context structure.
  */
 typedef struct mbedtls_ctr_drbg_context {
     unsigned char MBEDTLS_PRIVATE(counter)[16];  /*!< The counter (V). */
     int MBEDTLS_PRIVATE(reseed_counter);         /*!< The reseed counter.
                                                   * This is the number of requests that have
                                                   * been made since the last (re)seeding,
                                                   * minus one.
                                                   * Before the initial seeding, this field
                                                   * contains the amount of entropy in bytes
                                                   * to use as a nonce for the initial seeding,
                                                   * or -1 if no nonce length has been explicitly
                                                   * set (see mbedtls_ctr_drbg_set_nonce_len()).
                                                   */
     int MBEDTLS_PRIVATE(prediction_resistance);  /*!< This determines whether prediction
                                                     resistance is enabled, that is
                                                     whether to systematically reseed before
                                                     each random generation. */
     size_t MBEDTLS_PRIVATE(entropy_len);         /*!< The amount of entropy grabbed on each
                                                     seed or reseed operation, in bytes. */
     int MBEDTLS_PRIVATE(reseed_interval);        /*!< The reseed interval.
                                                   * This is the maximum number of requests
                                                   * that can be made between reseedings. */
 
 #if defined(MBEDTLS_CTR_DRBG_USE_PSA_CRYPTO)
     mbedtls_ctr_drbg_psa_context MBEDTLS_PRIVATE(psa_ctx); /*!< The PSA context. */
 #else
     mbedtls_aes_context MBEDTLS_PRIVATE(aes_ctx);        /*!< The AES context. */
 #endif
 
     /*
      * Callbacks (Entropy)
      */
     int(*MBEDTLS_PRIVATE(f_entropy))(void *, unsigned char *, size_t);
     /*!< The entropy callback function. */
 
     void *MBEDTLS_PRIVATE(p_entropy);            /*!< The context for the entropy function. */
 
 #if defined(MBEDTLS_THREADING_C)
     /* Invariant: the mutex is initialized if and only if f_entropy != NULL.
      * This means that the mutex is initialized during the initial seeding
      * in mbedtls_ctr_drbg_seed() and freed in mbedtls_ctr_drbg_free().
      *
      * Note that this invariant may change without notice. Do not rely on it
      * and do not access the mutex directly in application code.
      */
     mbedtls_threading_mutex_t MBEDTLS_PRIVATE(mutex);
 #endif
 }
 mbedtls_ctr_drbg_context;
 
 /**
  * \brief               This function initializes the CTR_DRBG context,
  *                      and prepares it for mbedtls_ctr_drbg_seed()
  *                      or mbedtls_ctr_drbg_free().
  *
  * \note                The reseed interval is
  *                      #MBEDTLS_CTR_DRBG_RESEED_INTERVAL by default.
  *                      You can override it by calling
  *                      mbedtls_ctr_drbg_set_reseed_interval().
  *
  * \param ctx           The CTR_DRBG context to initialize.
  */
 void mbedtls_ctr_drbg_init(mbedtls_ctr_drbg_context *ctx);
 
 /**
  * \brief               This function seeds and sets up the CTR_DRBG
  *                      entropy source for future reseeds.
  *
  * A typical choice for the \p f_entropy and \p p_entropy parameters is
  * to use the entropy module:
  * - \p f_entropy is mbedtls_entropy_func();
  * - \p p_entropy is an instance of ::mbedtls_entropy_context initialized
  *   with mbedtls_entropy_init() (which registers the platform's default
  *   entropy sources).
  *
  * The entropy length is #MBEDTLS_CTR_DRBG_ENTROPY_LEN by default.
  * You can override it by calling mbedtls_ctr_drbg_set_entropy_len().
  *
  * The entropy nonce length is:
  * - \c 0 if the entropy length is at least 3/2 times the entropy length,
  *   which guarantees that the security strength is the maximum permitted
  *   by the key size and entropy length according to NIST SP 800-90A §10.2.1;
  * - Half the entropy length otherwise.
  * You can override it by calling mbedtls_ctr_drbg_set_nonce_len().
  * With the default entropy length, the entropy nonce length is
  * #MBEDTLS_CTR_DRBG_ENTROPY_NONCE_LEN.
  *
  * You can provide a nonce and personalization string in addition to the
  * entropy source, to make this instantiation as unique as possible.
  * See SP 800-90A §8.6.7 for more details about nonces.
  *
  * The _seed_material_ value passed to the derivation function in
  * the CTR_DRBG Instantiate Process described in NIST SP 800-90A §10.2.1.3.2
  * is the concatenation of the following strings:
  * - A string obtained by calling \p f_entropy function for the entropy
  *   length.
  */
 #if MBEDTLS_CTR_DRBG_ENTROPY_NONCE_LEN == 0
 /**
  * - If mbedtls_ctr_drbg_set_nonce_len() has been called, a string
  *   obtained by calling \p f_entropy function for the specified length.
  */
 #else
 /**
  * - A string obtained by calling \p f_entropy function for the entropy nonce
  *   length. If the entropy nonce length is \c 0, this function does not
  *   make a second call to \p f_entropy.
  */
 #endif
 #if defined(MBEDTLS_THREADING_C)
 /**
  * \note                When Mbed TLS is built with threading support,
  *                      after this function returns successfully,
  *                      it is safe to call mbedtls_ctr_drbg_random()
  *                      from multiple threads. Other operations, including
  *                      reseeding, are not thread-safe.
  */
 #endif /* MBEDTLS_THREADING_C */
 /**
  * - The \p custom string.
  *
  * \note                To achieve the nominal security strength permitted
  *                      by CTR_DRBG, the entropy length must be:
  *                      - at least 16 bytes for a 128-bit strength
  *                      (maximum achievable strength when using AES-128);
  *                      - at least 32 bytes for a 256-bit strength
  *                      (maximum achievable strength when using AES-256).
  *
  *                      In addition, if you do not pass a nonce in \p custom,
  *                      the sum of the entropy length
  *                      and the entropy nonce length must be:
  *                      - at least 24 bytes for a 128-bit strength
  *                      (maximum achievable strength when using AES-128);
  *                      - at least 48 bytes for a 256-bit strength
  *                      (maximum achievable strength when using AES-256).
  *
  * \param ctx           The CTR_DRBG context to seed.
  *                      It must have been initialized with
  *                      mbedtls_ctr_drbg_init().
  *                      After a successful call to mbedtls_ctr_drbg_seed(),
  *                      you may not call mbedtls_ctr_drbg_seed() again on
  *                      the same context unless you call
  *                      mbedtls_ctr_drbg_free() and mbedtls_ctr_drbg_init()
  *                      again first.
  *                      After a failed call to mbedtls_ctr_drbg_seed(),
  *                      you must call mbedtls_ctr_drbg_free().
  * \param f_entropy     The entropy callback, taking as arguments the
  *                      \p p_entropy context, the buffer to fill, and the
  *                      length of the buffer.
  *                      \p f_entropy is always called with a buffer size
  *                      less than or equal to the entropy length.
  * \param p_entropy     The entropy context to pass to \p f_entropy.
  * \param custom        The personalization string.
  *                      This can be \c NULL, in which case the personalization
  *                      string is empty regardless of the value of \p len.
  * \param len           The length of the personalization string.
  *                      This must be at most
  *                      #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT
  *                      - #MBEDTLS_CTR_DRBG_ENTROPY_LEN.
  *
  * \return              \c 0 on success.
  * \return              #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on failure.
  */
 int mbedtls_ctr_drbg_seed(mbedtls_ctr_drbg_context *ctx,
                           int (*f_entropy)(void *, unsigned char *, size_t),
                           void *p_entropy,
                           const unsigned char *custom,
                           size_t len);
 
 /**
  * \brief               This function resets CTR_DRBG context to the state immediately
  *                      after initial call of mbedtls_ctr_drbg_init().
  *
  * \param ctx           The CTR_DRBG context to clear.
  */
 void mbedtls_ctr_drbg_free(mbedtls_ctr_drbg_context *ctx);
 
 /**
  * \brief               This function turns prediction resistance on or off.
  *                      The default value is off.
  *
  * \note                If enabled, entropy is gathered at the beginning of
  *                      every call to mbedtls_ctr_drbg_random_with_add()
  *                      or mbedtls_ctr_drbg_random().
  *                      Only use this if your entropy source has sufficient
  *                      throughput.
  *
  * \param ctx           The CTR_DRBG context.
  * \param resistance    #MBEDTLS_CTR_DRBG_PR_ON or #MBEDTLS_CTR_DRBG_PR_OFF.
  */
 void mbedtls_ctr_drbg_set_prediction_resistance(mbedtls_ctr_drbg_context *ctx,
                                                 int resistance);
 
 /**
  * \brief               This function sets the amount of entropy grabbed on each
  *                      seed or reseed.
  *
  * The default value is #MBEDTLS_CTR_DRBG_ENTROPY_LEN.
  *
  * \note                The security strength of CTR_DRBG is bounded by the
  *                      entropy length. Thus:
  *                      - When using AES-256
  *                        (\c MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is disabled,
  *                        which is the default),
  *                        \p len must be at least 32 (in bytes)
  *                        to achieve a 256-bit strength.
  *                      - When using AES-128
  *                        (\c MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is enabled)
  *                        \p len must be at least 16 (in bytes)
  *                        to achieve a 128-bit strength.
  *
  * \param ctx           The CTR_DRBG context.
  * \param len           The amount of entropy to grab, in bytes.
  *                      This must be at most #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT
  *                      and at most the maximum length accepted by the
  *                      entropy function that is set in the context.
  */
 void mbedtls_ctr_drbg_set_entropy_len(mbedtls_ctr_drbg_context *ctx,
                                       size_t len);
 
 /**
  * \brief               This function sets the amount of entropy grabbed
  *                      as a nonce for the initial seeding.
  *
  * Call this function before calling mbedtls_ctr_drbg_seed() to read
  * a nonce from the entropy source during the initial seeding.
  *
  * \param ctx           The CTR_DRBG context.
  * \param len           The amount of entropy to grab for the nonce, in bytes.
  *                      This must be at most #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT
  *                      and at most the maximum length accepted by the
  *                      entropy function that is set in the context.
  *
  * \return              \c 0 on success.
  * \return              #MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG if \p len is
  *                      more than #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT.
  * \return              #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED
  *                      if the initial seeding has already taken place.
  */
 int mbedtls_ctr_drbg_set_nonce_len(mbedtls_ctr_drbg_context *ctx,
                                    size_t len);
 
 /**
  * \brief               This function sets the reseed interval.
  *
  * The reseed interval is the number of calls to mbedtls_ctr_drbg_random()
  * or mbedtls_ctr_drbg_random_with_add() after which the entropy function
  * is called again.
  *
  * The default value is #MBEDTLS_CTR_DRBG_RESEED_INTERVAL.
  *
  * \param ctx           The CTR_DRBG context.
  * \param interval      The reseed interval.
  */
 void mbedtls_ctr_drbg_set_reseed_interval(mbedtls_ctr_drbg_context *ctx,
                                           int interval);
 
 /**
  * \brief               This function reseeds the CTR_DRBG context, that is
  *                      extracts data from the entropy source.
  *
  * \note                This function is not thread-safe. It is not safe
  *                      to call this function if another thread might be
  *                      concurrently obtaining random numbers from the same
  *                      context or updating or reseeding the same context.
  *
  * \param ctx           The CTR_DRBG context.
  * \param additional    Additional data to add to the state. Can be \c NULL.
  * \param len           The length of the additional data.
  *                      This must be less than
  *                      #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT - \c entropy_len
  *                      where \c entropy_len is the entropy length
  *                      configured for the context.
  *
  * \return              \c 0 on success.
  * \return              #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on failure.
  */
 int mbedtls_ctr_drbg_reseed(mbedtls_ctr_drbg_context *ctx,
                             const unsigned char *additional, size_t len);
 
 /**
  * \brief              This function updates the state of the CTR_DRBG context.
  *
  * \note                This function is not thread-safe. It is not safe
  *                      to call this function if another thread might be
  *                      concurrently obtaining random numbers from the same
  *                      context or updating or reseeding the same context.
  *
  * \param ctx          The CTR_DRBG context.
  * \param additional   The data to update the state with. This must not be
  *                     \c NULL unless \p add_len is \c 0.
  * \param add_len      Length of \p additional in bytes. This must be at
  *                     most #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT.
  *
  * \return             \c 0 on success.
  * \return             #MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG if
  *                     \p add_len is more than
  *                     #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT.
  * \return             An error from the underlying AES cipher on failure.
  */
 int mbedtls_ctr_drbg_update(mbedtls_ctr_drbg_context *ctx,
                             const unsigned char *additional,
                             size_t add_len);
 
 /**
  * \brief   This function updates a CTR_DRBG instance with additional
  *          data and uses it to generate random data.
  *
  * This function automatically reseeds if the reseed counter is exceeded
  * or prediction resistance is enabled.
  *
  * \note                This function is not thread-safe. It is not safe
  *                      to call this function if another thread might be
  *                      concurrently obtaining random numbers from the same
  *                      context or updating or reseeding the same context.
  *
  * \param p_rng         The CTR_DRBG context. This must be a pointer to a
  *                      #mbedtls_ctr_drbg_context structure.
  * \param output        The buffer to fill.
  * \param output_len    The length of the buffer in bytes.
  * \param additional    Additional data to update. Can be \c NULL, in which
  *                      case the additional data is empty regardless of
  *                      the value of \p add_len.
  * \param add_len       The length of the additional data
  *                      if \p additional is not \c NULL.
  *                      This must be less than #MBEDTLS_CTR_DRBG_MAX_INPUT
  *                      and less than
  *                      #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT - \c entropy_len
  *                      where \c entropy_len is the entropy length
  *                      configured for the context.
  *
  * \return    \c 0 on success.
  * \return    #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or
  *            #MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG on failure.
  */
 int mbedtls_ctr_drbg_random_with_add(void *p_rng,
                                      unsigned char *output, size_t output_len,
                                      const unsigned char *additional, size_t add_len);
 
 /**
  * \brief   This function uses CTR_DRBG to generate random data.
  *
  * This function automatically reseeds if the reseed counter is exceeded
  * or prediction resistance is enabled.
  */
 #if defined(MBEDTLS_THREADING_C)
 /**
  * \note                When Mbed TLS is built with threading support,
  *                      it is safe to call mbedtls_ctr_drbg_random()
  *                      from multiple threads. Other operations, including
  *                      reseeding, are not thread-safe.
  */
 #endif /* MBEDTLS_THREADING_C */
 /**
  * \param p_rng         The CTR_DRBG context. This must be a pointer to a
  *                      #mbedtls_ctr_drbg_context structure.
  * \param output        The buffer to fill.
  * \param output_len    The length of the buffer in bytes.
  *
  * \return              \c 0 on success.
  * \return              #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or
  *                      #MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG on failure.
  */
 int mbedtls_ctr_drbg_random(void *p_rng,
                             unsigned char *output, size_t output_len);
 
 #if defined(MBEDTLS_FS_IO)
 /**
  * \brief               This function writes a seed file.
  *
  * \param ctx           The CTR_DRBG context.
  * \param path          The name of the file.
  *
  * \return              \c 0 on success.
  * \return              #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error.
  * \return              #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on reseed
  *                      failure.
  */
 int mbedtls_ctr_drbg_write_seed_file(mbedtls_ctr_drbg_context *ctx, const char *path);
 
 /**
  * \brief               This function reads and updates a seed file. The seed
  *                      is added to this instance.
  *
  * \param ctx           The CTR_DRBG context.
  * \param path          The name of the file.
  *
  * \return              \c 0 on success.
  * \return              #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error.
  * \return              #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on
  *                      reseed failure.
  * \return              #MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG if the existing
  *                      seed file is too large.
  */
 int mbedtls_ctr_drbg_update_seed_file(mbedtls_ctr_drbg_context *ctx, const char *path);
 #endif /* MBEDTLS_FS_IO */
 
 #if defined(MBEDTLS_SELF_TEST)
 
 /**
  * \brief               The CTR_DRBG checkup routine.
  *
  * \return              \c 0 on success.
  * \return              \c 1 on failure.
  */
 int mbedtls_ctr_drbg_self_test(int verbose);
 
 #endif /* MBEDTLS_SELF_TEST */
 
 #ifdef __cplusplus
 }
 #endif
 
 #endif /* ctr_drbg.h */

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