File md.h

This file contains the generic functions for message-digest (hashing) and HMAC.

Author: Adriaan de Jong dejong@fox-it.com

Defines

MBEDTLS_ERR_MD_FEATURE_UNAVAILABLE: The selected feature is not available.

MBEDTLS_ERR_MD_BAD_INPUT_DATA: Bad input parameters to function.

MBEDTLS_ERR_MD_ALLOC_FAILED: Failed to allocate memory.

MBEDTLS_ERR_MD_FILE_IO_ERROR: Opening or reading of file failed.

MBEDTLS_MD_MAX_SIZE

MBEDTLS_MD_MAX_BLOCK_SIZE

Typedefs

typedef struct mbedtls_md_info_t mbedtls_md_info_t

Opaque struct.

Constructed using either mbedtls_md_info_from_string or mbedtls_md_info_from_type.

Fields can be accessed with mbedtls_md_get_size, mbedtls_md_get_type and mbedtls_md_get_name.

typedef struct mbedtls_md_context_t mbedtls_md_context_t: The generic message-digest context.

Enums

enum mbedtls_md_type_t

Supported message digests.

Warning

MD5 and SHA-1 are considered weak message digests and their use constitutes a security risk. We recommend considering stronger message digests instead.

Values:

enumerator MBEDTLS_MD_NONE: None.

enumerator MBEDTLS_MD_MD5: The MD5 message digest.

enumerator MBEDTLS_MD_RIPEMD160: The RIPEMD-160 message digest.

enumerator MBEDTLS_MD_SHA1: The SHA-1 message digest.

enumerator MBEDTLS_MD_SHA224: The SHA-224 message digest.

enumerator MBEDTLS_MD_SHA256: The SHA-256 message digest.

enumerator MBEDTLS_MD_SHA384: The SHA-384 message digest.

enumerator MBEDTLS_MD_SHA512: The SHA-512 message digest.

enumerator MBEDTLS_MD_SHA3_224: The SHA3-224 message digest.

enumerator MBEDTLS_MD_SHA3_256: The SHA3-256 message digest.

enumerator MBEDTLS_MD_SHA3_384: The SHA3-384 message digest.

enumerator MBEDTLS_MD_SHA3_512: The SHA3-512 message digest.

enum mbedtls_md_engine_t

Used internally to indicate whether a context uses legacy or PSA.

Internal use only.

Values:

enumerator MBEDTLS_MD_ENGINE_LEGACY

enumerator MBEDTLS_MD_ENGINE_PSA

Functions

const mbedtls_md_info_t *mbedtls_md_info_from_type(mbedtls_md_type_t md_type)

This function returns the message-digest information associated with the given digest type.

Parameters: md_type – The type of digest to search for.
Returns: The message-digest information associated with md_type.
Returns: NULL if the associated message-digest information is not found.

void mbedtls_md_init(mbedtls_md_context_t *ctx)

This function initializes a message-digest context without binding it to a particular message-digest algorithm.

This function should always be called first. It prepares the context for mbedtls_md_setup() for binding it to a message-digest algorithm.

void mbedtls_md_free(mbedtls_md_context_t *ctx)

This function clears the internal structure of ctx and frees any embedded internal structure, but does not free ctx itself.

If you have called mbedtls_md_setup() on ctx, you must call mbedtls_md_free() when you are no longer using the context. Calling this function if you have previously called mbedtls_md_init() and nothing else is optional. You must not call this function if you have not called mbedtls_md_init().

int mbedtls_md_setup(mbedtls_md_context_t *ctx, const mbedtls_md_info_t *md_info, int hmac)

This function selects the message digest algorithm to use, and allocates internal structures.

It should be called after mbedtls_md_init() or mbedtls_md_free(). Makes it necessary to call mbedtls_md_free() later.

Parameters

ctx – The context to set up.
md_info – The information structure of the message-digest algorithm to use.
hmac – Defines if HMAC is used. 0: HMAC is not used (saves some memory), or non-zero: HMAC is used with this context.

Returns

0 on success.

Returns

MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification failure.

Returns

MBEDTLS_ERR_MD_ALLOC_FAILED on memory-allocation failure.

int mbedtls_md_clone(mbedtls_md_context_t *dst, const mbedtls_md_context_t *src)

This function clones the state of a message-digest context.

Note

You must call mbedtls_md_setup() on dst before calling this function.

Note

The two contexts must have the same type, for example, both are SHA-256.

Warning

This function clones the message-digest state, not the HMAC state.

Parameters

dst – The destination context.
src – The context to be cloned.

Returns

0 on success.

Returns

MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification failure.

Returns

MBEDTLS_ERR_MD_FEATURE_UNAVAILABLE if both contexts are not using the same engine. This can be avoided by moving the call to psa_crypto_init() before the first call to mbedtls_md_setup().

unsigned char mbedtls_md_get_size(const mbedtls_md_info_t *md_info)

This function extracts the message-digest size from the message-digest information structure.

Parameters: md_info – The information structure of the message-digest algorithm to use.
Returns: The size of the message-digest output in Bytes.

static inline unsigned char mbedtls_md_get_size_from_type(mbedtls_md_type_t md_type)

This function gives the message-digest size associated to message-digest type.

Parameters: md_type – The message-digest type.
Returns: The size of the message-digest output in Bytes, or 0 if the message-digest type is not known.

mbedtls_md_type_t mbedtls_md_get_type(const mbedtls_md_info_t *md_info)

This function extracts the message-digest type from the message-digest information structure.

Parameters: md_info – The information structure of the message-digest algorithm to use.
Returns: The type of the message digest.

int mbedtls_md_starts(mbedtls_md_context_t *ctx)

This function starts a message-digest computation.

             You must call this function after setting up the context
             with mbedtls_md_setup(), and before passing data with
             mbedtls_md_update().

Parameters: ctx – The generic message-digest context.
Returns: 0 on success.
Returns: MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification failure.

int mbedtls_md_update(mbedtls_md_context_t *ctx, const unsigned char *input, size_t ilen)

This function feeds an input buffer into an ongoing message-digest computation.

You must call mbedtls_md_starts() before calling this function. You may call this function multiple times. Afterwards, call mbedtls_md_finish().

Parameters

ctx – The generic message-digest context.
input – The buffer holding the input data.
ilen – The length of the input data.

Returns

0 on success.

Returns

MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification failure.

int mbedtls_md_finish(mbedtls_md_context_t *ctx, unsigned char *output)

This function finishes the digest operation, and writes the result to the output buffer.

Call this function after a call to mbedtls_md_starts(), followed by any number of calls to mbedtls_md_update(). Afterwards, you may either clear the context with mbedtls_md_free(), or call mbedtls_md_starts() to reuse the context for another digest operation with the same algorithm.

Parameters

ctx – The generic message-digest context.
output – The buffer for the generic message-digest checksum result.

Returns

0 on success.

Returns

MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification failure.

int mbedtls_md(const mbedtls_md_info_t *md_info, const unsigned char *input, size_t ilen, unsigned char *output)

This function calculates the message-digest of a buffer, with respect to a configurable message-digest algorithm in a single call.

The result is calculated as Output = message_digest(input buffer).

Parameters

md_info – The information structure of the message-digest algorithm to use.
input – The buffer holding the data.
ilen – The length of the input data.
output – The generic message-digest checksum result.

Returns

0 on success.

Returns

MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification failure.

const int *mbedtls_md_list(void)

This function returns the list of digests supported by the generic digest module.

Note

The list starts with the strongest available hashes.

Returns: A statically allocated array of digests. Each element in the returned list is an integer belonging to the message-digest enumeration mbedtls_md_type_t. The last entry is 0.

const mbedtls_md_info_t *mbedtls_md_info_from_string(const char *md_name)

This function returns the message-digest information associated with the given digest name.

Parameters: md_name – The name of the digest to search for.
Returns: The message-digest information associated with md_name.
Returns: NULL if the associated message-digest information is not found.

const char *mbedtls_md_get_name(const mbedtls_md_info_t *md_info)

This function returns the name of the message digest for the message-digest information structure given.

Parameters: md_info – The information structure of the message-digest algorithm to use.
Returns: The name of the message digest.

const mbedtls_md_info_t *mbedtls_md_info_from_ctx(const mbedtls_md_context_t *ctx)

This function returns the message-digest information from the given context.

Parameters: ctx – The context from which to extract the information. This must be initialized (or NULL).
Returns: The message-digest information associated with ctx.
Returns: NULL if ctx is NULL.

int mbedtls_md_file(const mbedtls_md_info_t *md_info, const char *path, unsigned char *output)

This function calculates the message-digest checksum result of the contents of the provided file.

The result is calculated as Output = message_digest(file contents).

Parameters

md_info – The information structure of the message-digest algorithm to use.
path – The input file name.
output – The generic message-digest checksum result.

Returns

0 on success.

Returns

MBEDTLS_ERR_MD_FILE_IO_ERROR on an I/O error accessing the file pointed by path.

Returns

MBEDTLS_ERR_MD_BAD_INPUT_DATA if md_info was NULL.

int mbedtls_md_hmac_starts(mbedtls_md_context_t *ctx, const unsigned char *key, size_t keylen)

This function sets the HMAC key and prepares to authenticate a new message.

Call this function after mbedtls_md_setup(), to use the MD context for an HMAC calculation, then call mbedtls_md_hmac_update() to provide the input data, and mbedtls_md_hmac_finish() to get the HMAC value.

Parameters

ctx – The message digest context containing an embedded HMAC context.
key – The HMAC secret key.
keylen – The length of the HMAC key in Bytes.

Returns

0 on success.

Returns

MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification failure.

int mbedtls_md_hmac_update(mbedtls_md_context_t *ctx, const unsigned char *input, size_t ilen)

This function feeds an input buffer into an ongoing HMAC computation.

Call mbedtls_md_hmac_starts() or mbedtls_md_hmac_reset() before calling this function. You may call this function multiple times to pass the input piecewise. Afterwards, call mbedtls_md_hmac_finish().

Parameters

ctx – The message digest context containing an embedded HMAC context.
input – The buffer holding the input data.
ilen – The length of the input data.

Returns

0 on success.

Returns

MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification failure.

int mbedtls_md_hmac_finish(mbedtls_md_context_t *ctx, unsigned char *output)

This function finishes the HMAC operation, and writes the result to the output buffer.

Call this function after mbedtls_md_hmac_starts() and mbedtls_md_hmac_update() to get the HMAC value. Afterwards you may either call mbedtls_md_free() to clear the context, or call mbedtls_md_hmac_reset() to reuse the context with the same HMAC key.

Parameters

ctx – The message digest context containing an embedded HMAC context.
output – The generic HMAC checksum result.

Returns

0 on success.

Returns

MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification failure.

int mbedtls_md_hmac_reset(mbedtls_md_context_t *ctx)

This function prepares to authenticate a new message with the same key as the previous HMAC operation.

You may call this function after mbedtls_md_hmac_finish(). Afterwards call mbedtls_md_hmac_update() to pass the new input.

Parameters: ctx – The message digest context containing an embedded HMAC context.
Returns: 0 on success.
Returns: MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification failure.

int mbedtls_md_hmac(const mbedtls_md_info_t *md_info, const unsigned char *key, size_t keylen, const unsigned char *input, size_t ilen, unsigned char *output)

This function calculates the full generic HMAC on the input buffer with the provided key.

The function allocates the context, performs the calculation, and frees the context.

The HMAC result is calculated as output = generic HMAC(hmac key, input buffer).

Parameters

md_info – The information structure of the message-digest algorithm to use.
key – The HMAC secret key.
keylen – The length of the HMAC secret key in Bytes.
input – The buffer holding the input data.
ilen – The length of the input data.
output – The generic HMAC result.

Returns

0 on success.

Returns

MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification failure.

struct mbedtls_md_context_t

#include <md.h>

The generic message-digest context.

Public Members

const mbedtls_md_info_t *private_md_info: Information about the associated message digest.

void *private_md_ctx: The digest-specific context (legacy) or the PSA operation.

void *private_hmac_ctx: The HMAC part of the context.