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340 lines
13 KiB
C
340 lines
13 KiB
C
/**
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* \file ctr_drbg.h
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*
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* \brief This file contains CTR_DRBG definitions and functions.
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*
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* CTR_DRBG is a standardized way of building a PRNG from a block-cipher
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* in counter mode operation, as defined in <em>NIST SP 800-90A:
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* Recommendation for Random Number Generation Using Deterministic Random
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* Bit Generators</em>.
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*
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* The Mbed TLS implementation of CTR_DRBG uses AES-256 (default) or AES-128
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* as the underlying block cipher.
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*
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* \warning Using 128-bit keys for CTR_DRBG limits the security of generated
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* keys and operations that use random values generated to 128-bit security.
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*/
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/*
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* Copyright (C) 2006-2018, Arm Limited (or its affiliates), All Rights Reserved
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* This file is part of Mbed TLS (https://tls.mbed.org)
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*/
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#ifndef MBEDTLS_CTR_DRBG_H
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#define MBEDTLS_CTR_DRBG_H
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#include "aes.h"
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#if defined(MBEDTLS_THREADING_C)
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#include "threading.h"
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#endif
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#define MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED -0x0034 /**< The entropy source failed. */
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#define MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG -0x0036 /**< The requested random buffer length is too big. */
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#define MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG -0x0038 /**< The input (entropy + additional data) is too large. */
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#define MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR -0x003A /**< Read or write error in file. */
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#define MBEDTLS_CTR_DRBG_BLOCKSIZE 16 /**< The block size used by the cipher. */
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#if defined(MBEDTLS_CTR_DRBG_USE_128_BIT_KEY)
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#define MBEDTLS_CTR_DRBG_KEYSIZE 16 /**< The key size used by the cipher (compile-time choice: 128 bits). */
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#else
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#define MBEDTLS_CTR_DRBG_KEYSIZE 32 /**< The key size used by the cipher (compile-time choice: 256 bits). */
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#endif
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#define MBEDTLS_CTR_DRBG_KEYBITS ( MBEDTLS_CTR_DRBG_KEYSIZE * 8 ) /**< The key size for the DRBG operation, in bits. */
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#define MBEDTLS_CTR_DRBG_SEEDLEN ( MBEDTLS_CTR_DRBG_KEYSIZE + MBEDTLS_CTR_DRBG_BLOCKSIZE ) /**< The seed length, calculated as (counter + AES key). */
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/**
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* \name SECTION: Module settings
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*
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* The configuration options you can set for this module are in this section.
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* Either change them in config.h or define them using the compiler command
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* line.
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* \{
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*/
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#if !defined(MBEDTLS_CTR_DRBG_ENTROPY_LEN)
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#if defined(MBEDTLS_SHA512_C) && !defined(MBEDTLS_ENTROPY_FORCE_SHA256)
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#define MBEDTLS_CTR_DRBG_ENTROPY_LEN 48
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/**< The amount of entropy used per seed by default:
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* <ul><li>48 with SHA-512.</li>
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* <li>32 with SHA-256.</li></ul>
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*/
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#else
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#define MBEDTLS_CTR_DRBG_ENTROPY_LEN 32
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/**< Amount of entropy used per seed by default:
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* <ul><li>48 with SHA-512.</li>
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* <li>32 with SHA-256.</li></ul>
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*/
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#endif
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#endif
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#if !defined(MBEDTLS_CTR_DRBG_RESEED_INTERVAL)
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#define MBEDTLS_CTR_DRBG_RESEED_INTERVAL 10000
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/**< The interval before reseed is performed by default. */
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#endif
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#if !defined(MBEDTLS_CTR_DRBG_MAX_INPUT)
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#define MBEDTLS_CTR_DRBG_MAX_INPUT 256
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/**< The maximum number of additional input Bytes. */
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#endif
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#if !defined(MBEDTLS_CTR_DRBG_MAX_REQUEST)
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#define MBEDTLS_CTR_DRBG_MAX_REQUEST 1024
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/**< The maximum number of requested Bytes per call. */
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#endif
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#if !defined(MBEDTLS_CTR_DRBG_MAX_SEED_INPUT)
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#define MBEDTLS_CTR_DRBG_MAX_SEED_INPUT 384
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/**< The maximum size of seed or reseed buffer. */
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#endif
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/* \} name SECTION: Module settings */
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#define MBEDTLS_CTR_DRBG_PR_OFF 0
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/**< Prediction resistance is disabled. */
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#define MBEDTLS_CTR_DRBG_PR_ON 1
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/**< Prediction resistance is enabled. */
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* \brief The CTR_DRBG context structure.
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*/
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typedef struct mbedtls_ctr_drbg_context
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{
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unsigned char counter[16]; /*!< The counter (V). */
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int reseed_counter; /*!< The reseed counter. */
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int prediction_resistance; /*!< This determines whether prediction
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resistance is enabled, that is
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whether to systematically reseed before
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each random generation. */
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size_t entropy_len; /*!< The amount of entropy grabbed on each
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seed or reseed operation. */
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int reseed_interval; /*!< The reseed interval. */
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mbedtls_aes_context aes_ctx; /*!< The AES context. */
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/*
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* Callbacks (Entropy)
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*/
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int (*f_entropy)(void *, unsigned char *, size_t);
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/*!< The entropy callback function. */
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void *p_entropy; /*!< The context for the entropy function. */
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#if defined(MBEDTLS_THREADING_C)
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mbedtls_threading_mutex_t mutex;
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#endif
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}
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mbedtls_ctr_drbg_context;
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/**
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* \brief This function initializes the CTR_DRBG context,
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* and prepares it for mbedtls_ctr_drbg_seed()
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* or mbedtls_ctr_drbg_free().
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*
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* \param ctx The CTR_DRBG context to initialize.
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*/
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void mbedtls_ctr_drbg_init( mbedtls_ctr_drbg_context *ctx );
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/**
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* \brief This function seeds and sets up the CTR_DRBG
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* entropy source for future reseeds.
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*
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* \note Personalization data can be provided in addition to the more generic
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* entropy source, to make this instantiation as unique as possible.
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*
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* \param ctx The CTR_DRBG context to seed.
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* \param f_entropy The entropy callback, taking as arguments the
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* \p p_entropy context, the buffer to fill, and the
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length of the buffer.
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* \param p_entropy The entropy context.
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* \param custom Personalization data, that is device-specific
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identifiers. Can be NULL.
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* \param len The length of the personalization data.
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*
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* \return \c 0 on success.
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* \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on failure.
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*/
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int mbedtls_ctr_drbg_seed( mbedtls_ctr_drbg_context *ctx,
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int (*f_entropy)(void *, unsigned char *, size_t),
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void *p_entropy,
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const unsigned char *custom,
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size_t len );
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/**
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* \brief This function clears CTR_CRBG context data.
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*
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* \param ctx The CTR_DRBG context to clear.
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*/
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void mbedtls_ctr_drbg_free( mbedtls_ctr_drbg_context *ctx );
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/**
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* \brief This function turns prediction resistance on or off.
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* The default value is off.
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*
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* \note If enabled, entropy is gathered at the beginning of
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* every call to mbedtls_ctr_drbg_random_with_add().
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* Only use this if your entropy source has sufficient
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* throughput.
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*
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* \param ctx The CTR_DRBG context.
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* \param resistance #MBEDTLS_CTR_DRBG_PR_ON or #MBEDTLS_CTR_DRBG_PR_OFF.
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*/
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void mbedtls_ctr_drbg_set_prediction_resistance( mbedtls_ctr_drbg_context *ctx,
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int resistance );
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/**
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* \brief This function sets the amount of entropy grabbed on each
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* seed or reseed. The default value is
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* #MBEDTLS_CTR_DRBG_ENTROPY_LEN.
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*
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* \param ctx The CTR_DRBG context.
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* \param len The amount of entropy to grab.
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*/
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void mbedtls_ctr_drbg_set_entropy_len( mbedtls_ctr_drbg_context *ctx,
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size_t len );
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/**
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* \brief This function sets the reseed interval.
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* The default value is #MBEDTLS_CTR_DRBG_RESEED_INTERVAL.
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*
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* \param ctx The CTR_DRBG context.
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* \param interval The reseed interval.
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*/
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void mbedtls_ctr_drbg_set_reseed_interval( mbedtls_ctr_drbg_context *ctx,
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int interval );
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/**
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* \brief This function reseeds the CTR_DRBG context, that is
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* extracts data from the entropy source.
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*
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* \param ctx The CTR_DRBG context.
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* \param additional Additional data to add to the state. Can be NULL.
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* \param len The length of the additional data.
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*
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* \return \c 0 on success.
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* \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on failure.
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*/
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int mbedtls_ctr_drbg_reseed( mbedtls_ctr_drbg_context *ctx,
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const unsigned char *additional, size_t len );
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/**
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* \brief This function updates the state of the CTR_DRBG context.
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*
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* \note If \p add_len is greater than
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* #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT, only the first
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* #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT Bytes are used.
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* The remaining Bytes are silently discarded.
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*
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* \param ctx The CTR_DRBG context.
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* \param additional The data to update the state with.
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* \param add_len Length of \p additional data.
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*
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*/
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void mbedtls_ctr_drbg_update( mbedtls_ctr_drbg_context *ctx,
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const unsigned char *additional, size_t add_len );
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/**
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* \brief This function updates a CTR_DRBG instance with additional
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* data and uses it to generate random data.
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*
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* \note The function automatically reseeds if the reseed counter is exceeded.
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*
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* \param p_rng The CTR_DRBG context. This must be a pointer to a
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* #mbedtls_ctr_drbg_context structure.
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* \param output The buffer to fill.
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* \param output_len The length of the buffer.
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* \param additional Additional data to update. Can be NULL.
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* \param add_len The length of the additional data.
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*
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* \return \c 0 on success.
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* \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or
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* #MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG on failure.
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*/
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int mbedtls_ctr_drbg_random_with_add( void *p_rng,
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unsigned char *output, size_t output_len,
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const unsigned char *additional, size_t add_len );
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/**
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* \brief This function uses CTR_DRBG to generate random data.
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*
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* \note The function automatically reseeds if the reseed counter is exceeded.
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*
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* \param p_rng The CTR_DRBG context. This must be a pointer to a
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* #mbedtls_ctr_drbg_context structure.
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* \param output The buffer to fill.
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* \param output_len The length of the buffer.
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*
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* \return \c 0 on success.
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* \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or
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* #MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG on failure.
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*/
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int mbedtls_ctr_drbg_random( void *p_rng,
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unsigned char *output, size_t output_len );
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#if defined(MBEDTLS_FS_IO)
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/**
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* \brief This function writes a seed file.
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*
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* \param ctx The CTR_DRBG context.
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* \param path The name of the file.
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*
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* \return \c 0 on success.
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* \return #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error.
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* \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on
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* failure.
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*/
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int mbedtls_ctr_drbg_write_seed_file( mbedtls_ctr_drbg_context *ctx, const char *path );
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/**
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* \brief This function reads and updates a seed file. The seed
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* is added to this instance.
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*
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* \param ctx The CTR_DRBG context.
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* \param path The name of the file.
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*
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* \return \c 0 on success.
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* \return #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error.
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* \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or
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* #MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG on failure.
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*/
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int mbedtls_ctr_drbg_update_seed_file( mbedtls_ctr_drbg_context *ctx, const char *path );
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#endif /* MBEDTLS_FS_IO */
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/**
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* \brief The CTR_DRBG checkup routine.
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*
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* \return \c 0 on success.
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* \return \c 1 on failure.
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*/
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int mbedtls_ctr_drbg_self_test( int verbose );
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/* Internal functions (do not call directly) */
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int mbedtls_ctr_drbg_seed_entropy_len( mbedtls_ctr_drbg_context *,
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int (*)(void *, unsigned char *, size_t), void *,
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const unsigned char *, size_t, size_t );
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#ifdef __cplusplus
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}
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#endif
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#endif /* ctr_drbg.h */
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