File platform.h

This file contains the definitions and functions of the Mbed TLS platform abstraction layer.

The platform abstraction layer removes the need for the library to directly link to standard C library functions or operating system services, making the library easier to port and embed. Application developers and users of the library can provide their own implementations of these functions, or implementations specific to their platform, which can be statically linked to the library or dynamically configured at runtime.

When all compilation options related to platform abstraction are disabled, this header just defines mbedtls_xxx function names as aliases to the standard xxx function.

Most modules in the library and example programs are expected to include this header.

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 on the compiler command line.

MBEDTLS_PLATFORM_STD_CALLOC: Default allocator to use, can be undefined. It must initialize the allocated buffer memory to zeroes. The size of the buffer is the product of the two parameters. The calloc function returns either a null pointer or a pointer to the allocated space. If the product is 0, the function may either return NULL or a valid pointer to an array of size 0 which is a valid input to the deallocation function. An uninitialized MBEDTLS_PLATFORM_STD_CALLOC always fails, returning a null pointer. See the description of MBEDTLS_PLATFORM_MEMORY for more details. The corresponding deallocation function is MBEDTLS_PLATFORM_STD_FREE.

MBEDTLS_PLATFORM_STD_FREE: Default free to use, can be undefined. NULL is a valid parameter, and the function must do nothing. A non-null parameter will always be a pointer previously returned by MBEDTLS_PLATFORM_STD_CALLOC and not yet freed. An uninitialized MBEDTLS_PLATFORM_STD_FREE does not do anything. See the description of MBEDTLS_PLATFORM_MEMORY for more details (same principles as for MBEDTLS_PLATFORM_STD_CALLOC apply).

Defines

MBEDTLS_EXIT_SUCCESS

MBEDTLS_EXIT_FAILURE

Functions

void *mbedtls_calloc(size_t n, size_t size)

void mbedtls_free(void *ptr)

int mbedtls_platform_set_calloc_free(void *(*calloc_func)(size_t, size_t), void (*free_func)(void*))

This function dynamically sets the memory-management functions used by the library, during runtime.

Parameters

calloc_func – The calloc function implementation.
free_func – The free function implementation.

Returns

0.

int mbedtls_platform_set_fprintf(int (*fprintf_func)(FILE *stream, const char*, ...))

This function dynamically configures the fprintf function that is called when the mbedtls_fprintf() function is invoked by the library.

Parameters: fprintf_func – The fprintf function implementation.
Returns: 0.

int mbedtls_platform_set_printf(int (*printf_func)(const char*, ...))

This function dynamically configures the snprintf function that is called when the mbedtls_snprintf() function is invoked by the library.

Parameters: printf_func – The printf function implementation.
Returns: 0 on success.

int mbedtls_platform_set_snprintf(int (*snprintf_func)(char *s, size_t n, const char *format, ...))

This function allows configuring a custom snprintf function pointer.

Parameters: snprintf_func – The snprintf function implementation.
Returns: 0 on success.

int mbedtls_platform_set_vsnprintf(int (*vsnprintf_func)(char *s, size_t n, const char *format, va_list arg))

Set your own snprintf function pointer.

Parameters: vsnprintf_func – The vsnprintf function implementation
Returns: 0

int mbedtls_platform_set_setbuf(void (*setbuf_func)(FILE *stream, char *buf))

Dynamically configure the function that is called when the mbedtls_setbuf() function is called by the library.

Parameters: setbuf_func – The setbuf function implementation
Returns: 0

int mbedtls_platform_set_exit(void (*exit_func)(int status))

This function dynamically configures the exit function that is called when the mbedtls_exit() function is invoked by the library.

Parameters: exit_func – The exit function implementation.
Returns: 0 on success.

int mbedtls_platform_set_nv_seed(int (*nv_seed_read_func)(unsigned char *buf, size_t buf_len), int (*nv_seed_write_func)(unsigned char *buf, size_t buf_len))

This function allows configuring custom seed file writing and reading functions.

Parameters

nv_seed_read_func – The seed reading function implementation.
nv_seed_write_func – The seed writing function implementation.

Returns

0 on success.

int mbedtls_platform_setup(mbedtls_platform_context *ctx)

This function performs any platform-specific initialization operations.

Note

This function should be called before any other library functions.

     Its implementation is platform-specific, and unless
     platform-specific code is provided, it does nothing.

Note

The usage and necessity of this function is dependent on the platform.

Parameters: ctx – The platform context.
Returns: 0 on success.

void mbedtls_platform_teardown(mbedtls_platform_context *ctx)

This function performs any platform teardown operations.

Its implementation is platform-specific, and unless platform-specific code is provided, it does nothing.

Note

This function should be called after every other Mbed TLS module has been correctly freed using the appropriate free function.

Note

The usage and necessity of this function is dependent on the platform.

Parameters: ctx – The platform context.

Variables

int (*mbedtls_fprintf)(FILE *stream, const char *format, ...)

int (*mbedtls_printf)(const char *format, ...)

int (*mbedtls_snprintf)(char *s, size_t n, const char *format, ...)

int (*mbedtls_vsnprintf)(char *s, size_t n, const char *format, va_list arg)

void (*mbedtls_setbuf)(FILE *stream, char *buf)

Function pointer to call for setbuf() functionality (changing the internal buffering on stdio calls).

The library always calls this function with buf equal to NULL.

Note

The library calls this function to disable buffering when reading or writing sensitive data, to avoid having extra copies of sensitive data remaining in stdio buffers after the file is closed. If this is not a concern, for example if your platform’s stdio doesn’t have any buffering, you can set mbedtls_setbuf to a function that does nothing.

void (*mbedtls_exit)(int status)

int (*mbedtls_nv_seed_read)(unsigned char *buf, size_t buf_len)

int (*mbedtls_nv_seed_write)(unsigned char *buf, size_t buf_len)