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Improve CTR-DRBG documentation

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- Rephrase file/function/parameter/enum/define/error descriptions into full
  and clear sentences.
- Make sure to adhere to the Arm writing guidelines.
- Fix missing/incorrect Doxygen tags.
- Standardize terminology used within the file.
- Add full standard name in file description.

GitHub PR: #1316
This commit is contained in:
Rose Zadik 2018-01-25 21:55:14 +00:00 committed by Jaeden Amero
parent 44833d9597
commit 2f8163d3cd
2 changed files with 143 additions and 112 deletions
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249
include/mbedtls/ctr_drbg.h
View file

@ -1,10 +1,13 @@
/**
* \file ctr_drbg.h
*
* \brief CTR_DRBG based on AES-256 (NIST SP 800-90)
* \brief CTR_DRBG is based on AES-256, as defined in <em>NIST SP 800-90A:
* Recommendation for Random Number Generation Using Deterministic
* Random Bit Generators</em>.
*
*/
/*
* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
* Copyright (C) 2006-2018, Arm Limited (or its affiliates), All Rights Reserved
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may
@ -19,8 +22,9 @@
* See the License for the specific language governing permissions and
* limitations under the License.
*
* This file is part of mbed TLS (https://tls.mbed.org)
* This file is part of Mbed TLS (https://tls.mbed.org)
*/
#ifndef MBEDTLS_CTR_DRBG_H
#define MBEDTLS_CTR_DRBG_H
@ -31,78 +35,95 @@
#endif
#define MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED -0x0034 /**< The entropy source failed. */
#define MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG -0x0036 /**< Too many random requested in single call. */
#define MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG -0x0038 /**< Input too large (Entropy + additional). */
#define MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR -0x003A /**< Read/write error in file. */
#define MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG -0x0036 /**< The requested random buffer length is too big. */
#define MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG -0x0038 /**< The input (entropy + additional data) is too large. */
#define MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR -0x003A /**< Read or write error in file. */
#define MBEDTLS_CTR_DRBG_BLOCKSIZE 16 /**< Block size used by the cipher */
#define MBEDTLS_CTR_DRBG_KEYSIZE 32 /**< Key size used by the cipher */
#define MBEDTLS_CTR_DRBG_KEYBITS ( MBEDTLS_CTR_DRBG_KEYSIZE * 8 )
#define MBEDTLS_CTR_DRBG_SEEDLEN ( MBEDTLS_CTR_DRBG_KEYSIZE + MBEDTLS_CTR_DRBG_BLOCKSIZE )
/**< The seed length (counter + AES key) */
#define MBEDTLS_CTR_DRBG_BLOCKSIZE 16 /**< The block size used by the cipher. */
#define MBEDTLS_CTR_DRBG_KEYSIZE 32 /**< The key size used by the cipher. */
#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 config.h or define them on the compiler command line.
* Either change them in config.h or define them using the compiler command
* line.
* \{
*/
#if !defined(MBEDTLS_CTR_DRBG_ENTROPY_LEN)
#if defined(MBEDTLS_SHA512_C) && !defined(MBEDTLS_ENTROPY_FORCE_SHA256)
#define MBEDTLS_CTR_DRBG_ENTROPY_LEN 48 /**< Amount of entropy used per seed by default (48 with SHA-512, 32 with SHA-256) */
#define MBEDTLS_CTR_DRBG_ENTROPY_LEN 48
/**< The amount of entropy used per seed by default:
* <ul><li>48 with SHA-512.</li>
* <li>32 with SHA-256.</li></ul>
*/
#else
#define MBEDTLS_CTR_DRBG_ENTROPY_LEN 32 /**< Amount of entropy used per seed by default (48 with SHA-512, 32 with SHA-256) */
#define MBEDTLS_CTR_DRBG_ENTROPY_LEN 32
/**< Amount of entropy used per seed by default:
* <ul><li>48 with SHA-512.</li>
* <li>32 with SHA-256.</li></ul>
*/
#endif
#endif
#if !defined(MBEDTLS_CTR_DRBG_RESEED_INTERVAL)
#define MBEDTLS_CTR_DRBG_RESEED_INTERVAL 10000 /**< Interval before reseed is performed by default */
#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 /**< Maximum number of additional input bytes */
#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 /**< Maximum number of requested bytes per call */
#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 /**< Maximum size of (re)seed buffer */
#define MBEDTLS_CTR_DRBG_MAX_SEED_INPUT 384
/**< The maximum size of seed or reseed buffer. */
#endif
/* \} name SECTION: Module settings */
#define MBEDTLS_CTR_DRBG_PR_OFF 0 /**< No prediction resistance */
#define MBEDTLS_CTR_DRBG_PR_ON 1 /**< Prediction resistance enabled */
#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
/**
* \brief CTR_DRBG context structure
* \brief The CTR_DRBG context structure.
*/
typedef struct
{
unsigned char counter[16]; /*!< counter (V) */
int reseed_counter; /*!< reseed counter */
int prediction_resistance; /*!< enable prediction resistance (Automatic
reseed before every random generation) */
size_t entropy_len; /*!< amount of entropy grabbed on each
(re)seed */
int reseed_interval; /*!< reseed interval */
unsigned char counter[16]; /*!< The counter (V). */
int reseed_counter; /*!< The reseed counter. */
int prediction_resistance; /*!< This determines whether prediction
resistance is enabled, that is
whether to systematically reseed before
each random generation. */
size_t entropy_len; /*!< The amount of entropy grabbed on each
seed or reseed operation. */
int reseed_interval; /*!< The reseed interval. */
mbedtls_aes_context aes_ctx; /*!< AES context */
mbedtls_aes_context aes_ctx; /*!< The AES context. */
/*
* Callbacks (Entropy)
*/
int (*f_entropy)(void *, unsigned char *, size_t);
/*!< The entropy callback function. */
void *p_entropy; /*!< context for the entropy function */
void *p_entropy; /*!< The context for the entropy function. */
#if defined(MBEDTLS_THREADING_C)
mbedtls_threading_mutex_t mutex;
@ -111,31 +132,32 @@ typedef struct
mbedtls_ctr_drbg_context;
/**
* \brief CTR_DRBG context initialization
* Makes the context ready for mbedtls_ctr_drbg_seed() or
* mbedtls_ctr_drbg_free().
* \brief This function initializes the CTR_DRBG context,
* and prepares it for mbedtls_ctr_drbg_seed()
* or mbedtls_ctr_drbg_free().
*
* \param ctx CTR_DRBG context to be initialized
* \param ctx The CTR_DRBG context to initialize.
*/
void mbedtls_ctr_drbg_init( mbedtls_ctr_drbg_context *ctx );
/**
* \brief CTR_DRBG initial seeding
* Seed and setup entropy source for future reseeds.
* \brief This function seeds and sets up the CTR_DRBG
* entropy source for future reseeds.
*
* Note: Personalization data can be provided in addition to the more generic
* entropy source to make this instantiation as unique as possible.
* \note Personalization data can be provided in addition to the more generic
* entropy source, to make this instantiation as unique as possible.
*
* \param ctx CTR_DRBG context to be seeded
* \param f_entropy Entropy callback (p_entropy, buffer to fill, buffer
* length)
* \param p_entropy Entropy context
* \param custom Personalization data (Device specific identifiers)
* (Can be NULL)
* \param len Length of personalization data
* \param ctx The CTR_DRBG context to seed.
* \param f_entropy The entropy callback, taking as arguments the
* \p p_entropy context, the buffer to fill, and the
length of the buffer.
* \param p_entropy The entropy context.
* \param custom Personalization data, that is device-specific
identifiers. Can be NULL.
* \param len The length of the personalization data.
*
* \return 0 if successful, or
* MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED
* \return \c 0 on success, or
* #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),
@ -144,138 +166,147 @@ int mbedtls_ctr_drbg_seed( mbedtls_ctr_drbg_context *ctx,
size_t len );
/**
* \brief Clear CTR_CRBG context data
* \brief This function clears CTR_CRBG context data.
*
* \param ctx CTR_DRBG context to clear
* \param ctx The CTR_DRBG context to clear.
*/
void mbedtls_ctr_drbg_free( mbedtls_ctr_drbg_context *ctx );
/**
* \brief Enable / disable prediction resistance (Default: Off)
* \brief This function turns prediction resistance on or off.
* The default value is off.
*
* Note: If enabled, entropy is used for ctx->entropy_len before each call!
* Only use this if you have ample supply of good entropy!
* \note If enabled, entropy is gathered at the beginning of
* every call to mbedtls_ctr_drbg_random_with_add().
* Only use this if your entropy source has sufficient
* throughput.
*
* \param ctx CTR_DRBG context
* \param resistance MBEDTLS_CTR_DRBG_PR_ON or MBEDTLS_CTR_DRBG_PR_OFF
* \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 Set the amount of entropy grabbed on each (re)seed
* (Default: MBEDTLS_CTR_DRBG_ENTROPY_LEN)
* \brief This function sets the amount of entropy grabbed on each
* seed or reseed. The default value is
* #MBEDTLS_CTR_DRBG_ENTROPY_LEN.
*
* \param ctx CTR_DRBG context
* \param len Amount of entropy to grab
* \param ctx The CTR_DRBG context.
* \param len The amount of entropy to grab.
*/
void mbedtls_ctr_drbg_set_entropy_len( mbedtls_ctr_drbg_context *ctx,
size_t len );
/**
* \brief Set the reseed interval
* (Default: MBEDTLS_CTR_DRBG_RESEED_INTERVAL)
* \brief This function sets the reseed interval.
* The default value is #MBEDTLS_CTR_DRBG_RESEED_INTERVAL.
*
* \param ctx CTR_DRBG context
* \param interval 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 CTR_DRBG reseeding (extracts data from entropy source)
* \brief This function reseeds the CTR_DRBG context, that is
* extracts data from the entropy source.
*
* \param ctx CTR_DRBG context
* \param additional Additional data to add to state (Can be NULL)
* \param len Length of additional data
* \param ctx The CTR_DRBG context.
* \param additional Additional data to add to the state. Can be NULL.
* \param len The length of the additional data.
*
* \return 0 if successful, or
* MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED
* \return \c 0 on success, or
* #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 CTR_DRBG update state
* \brief This function updates the state of the CTR_DRBG context.
*
* \param ctx CTR_DRBG context
* \param additional Additional data to update state with
* \param add_len Length of additional data
* \param ctx The CTR_DRBG context.
* \param additional The data to update the state with.
* \param add_len Length of \p additional data.
*
* \note If add_len is greater than MBEDTLS_CTR_DRBG_MAX_SEED_INPUT,
* only the first MBEDTLS_CTR_DRBG_MAX_SEED_INPUT bytes are used,
* the remaining ones are silently discarded.
* \note If \p add_len is greater than #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT,
* only the first #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT Bytes are used.
* The remaining Bytes are silently discarded.
*/
void mbedtls_ctr_drbg_update( mbedtls_ctr_drbg_context *ctx,
const unsigned char *additional, size_t add_len );
/**
* \brief CTR_DRBG generate random with additional update input
* \brief This function updates a CTR_DRBG instance with additional
* data and uses it to generate random data.
*
* Note: Automatically reseeds if reseed_counter is reached.
* \note The function automatically reseeds if the reseed counter is exceeded.
*
* \param p_rng CTR_DRBG context
* \param output Buffer to fill
* \param output_len Length of the buffer
* \param additional Additional data to update with (Can be NULL)
* \param add_len Length of additional data
* \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.
* \param additional Additional data to update. Can be NULL.
* \param add_len The length of the additional data.
*
* \return 0 if successful, or
* MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED, or
* MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG
* \return \c 0 on success, or
* #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 CTR_DRBG generate random
* \brief This function uses CTR_DRBG to generate random data.
*
* Note: Automatically reseeds if reseed_counter is reached.
* \note The function automatically reseeds if the reseed counter is exceeded.
*
* \param p_rng CTR_DRBG context
* \param output Buffer to fill
* \param output_len Length of the buffer
* \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.
*
* \return 0 if successful, or
* MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED, or
* MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG
* \return \c 0 on success, or
* #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 Write a seed file
* \brief This function writes a seed file.
*
* \param ctx CTR_DRBG context
* \param path Name of the file
* \param ctx The CTR_DRBG context.
* \param path The name of the file.
*
* \return 0 if successful,
* MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error, or
* MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED
* \return \c 0 on success,
* #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error, or
* #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on
* failure.
*/
int mbedtls_ctr_drbg_write_seed_file( mbedtls_ctr_drbg_context *ctx, const char *path );
/**
* \brief Read and update a seed file. Seed is added to this
* instance
* \brief This function reads and updates a seed file. The seed
* is added to this instance.
*
* \param ctx CTR_DRBG context
* \param path Name of the file
* \param ctx The CTR_DRBG context.
* \param path The name of the file.
*
* \return 0 if successful,
* MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error,
* MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or
* MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG
* \return \c 0 on success,
* #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error,
* #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or
* #MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG on failure.
*/
int mbedtls_ctr_drbg_update_seed_file( mbedtls_ctr_drbg_context *ctx, const char *path );
#endif /* MBEDTLS_FS_IO */
/**
* \brief Checkup routine
* \brief The CTR_DRBG checkup routine.
*
* \return 0 if successful, or 1 if the test failed
* \return \c 0 on success, or \c 1 on failure.
*/
int mbedtls_ctr_drbg_self_test( int verbose );

6
library/error.c
View file

@ -658,11 +658,11 @@ void mbedtls_strerror( int ret, char *buf, size_t buflen )
if( use_ret == -(MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED) )
mbedtls_snprintf( buf, buflen, "CTR_DRBG - The entropy source failed" );
if( use_ret == -(MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG) )
mbedtls_snprintf( buf, buflen, "CTR_DRBG - Too many random requested in single call" );
mbedtls_snprintf( buf, buflen, "CTR_DRBG - The requested random buffer length is too big" );
if( use_ret == -(MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG) )
mbedtls_snprintf( buf, buflen, "CTR_DRBG - Input too large (Entropy + additional)" );
mbedtls_snprintf( buf, buflen, "CTR_DRBG - The input (entropy + additional data) is too large" );
if( use_ret == -(MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR) )
mbedtls_snprintf( buf, buflen, "CTR_DRBG - Read/write error in file" );
mbedtls_snprintf( buf, buflen, "CTR_DRBG - Read or write error in file" );
#endif /* MBEDTLS_CTR_DRBG_C */
#if defined(MBEDTLS_DES_C)