mbedtls/include/mbedtls/md.h
Hanno Becker 4c6876b134 Provide standalone version of ssl_decrypt_buf
Analogous to the previous commit, but concerning the record decryption
routine `ssl_decrypt_buf`.

An important change regards the checking of CBC padding:
Prior to this commit, the CBC padding check always read 256 bytes at
the end of the internal record buffer, almost always going past the
boundaries of the record under consideration. In order to stay within
the bounds of the given record, this commit changes this behavior by
always reading the last min(256, plaintext_len) bytes of the record
plaintext buffer and taking into consideration the last `padlen` of
these for the padding check. With this change, the memory access
pattern and runtime of the padding check is entirely determined by
the size of the encrypted record, in particular not giving away
any information on the validity of the padding.

The following depicts the different behaviors:

1) Previous CBC padding check

1.a) Claimed padding length <= plaintext length

  +----------------------------------------+----+
  |   Record plaintext buffer   |          | PL |
  +----------------------------------------+----+
                                 \__ PL __/

                                +------------------------------------...
                                |  read for padding check            ...
                                +------------------------------------...
                                                |
                                                 contents discarded
                                                 from here

1.b) Claimed padding length > plaintext length

  +----------------------------------------+----+
  |   Record plaintext buffer              | PL |
  +----------------------------------------+----+
                                           +-------------------------...
                                           |  read for padding check ...
                                           +-------------------------...
                                                |
                                                 contents discarded
                                                 from here

2) New CBC padding check

  +----------------------------------------+----+
  |   Record plaintext buffer   |          | PL |
  +----------------------------------------+----+
                                 \__ PL __/

        +---------------------------------------+
        |        read for padding check         |
        +---------------------------------------+
                                |
                                 contents discarded
                                 until here
2019-04-29 12:13:25 +02:00

475 lines
18 KiB
C

/**
* \file md.h
*
* \brief This file contains the generic message-digest wrapper.
*
* \author Adriaan de Jong <dejong@fox-it.com>
*/
/*
* 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
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* 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)
*/
#ifndef MBEDTLS_MD_H
#define MBEDTLS_MD_H
#include <stddef.h>
#if !defined(MBEDTLS_CONFIG_FILE)
#include "config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
#define MBEDTLS_ERR_MD_FEATURE_UNAVAILABLE -0x5080 /**< The selected feature is not available. */
#define MBEDTLS_ERR_MD_BAD_INPUT_DATA -0x5100 /**< Bad input parameters to function. */
#define MBEDTLS_ERR_MD_ALLOC_FAILED -0x5180 /**< Failed to allocate memory. */
#define MBEDTLS_ERR_MD_FILE_IO_ERROR -0x5200 /**< Opening or reading of file failed. */
/* MBEDTLS_ERR_MD_HW_ACCEL_FAILED is deprecated and should not be used. */
#define MBEDTLS_ERR_MD_HW_ACCEL_FAILED -0x5280 /**< MD hardware accelerator failed. */
#ifdef __cplusplus
extern "C" {
#endif
/**
* \brief Supported message digests.
*
* \warning MD2, MD4, MD5 and SHA-1 are considered weak message digests and
* their use constitutes a security risk. We recommend considering
* stronger message digests instead.
*
*/
typedef enum {
MBEDTLS_MD_NONE=0, /**< None. */
MBEDTLS_MD_MD2, /**< The MD2 message digest. */
MBEDTLS_MD_MD4, /**< The MD4 message digest. */
MBEDTLS_MD_MD5, /**< The MD5 message digest. */
MBEDTLS_MD_SHA1, /**< The SHA-1 message digest. */
MBEDTLS_MD_SHA224, /**< The SHA-224 message digest. */
MBEDTLS_MD_SHA256, /**< The SHA-256 message digest. */
MBEDTLS_MD_SHA384, /**< The SHA-384 message digest. */
MBEDTLS_MD_SHA512, /**< The SHA-512 message digest. */
MBEDTLS_MD_RIPEMD160, /**< The RIPEMD-160 message digest. */
} mbedtls_md_type_t;
#if defined(MBEDTLS_SHA512_C)
#define MBEDTLS_MD_MAX_SIZE 64 /* longest known is SHA512 */
#else
#define MBEDTLS_MD_MAX_SIZE 32 /* longest known is SHA256 or less */
#endif
#if defined(MBEDTLS_SHA512_C)
#define MBEDTLS_MD_MAX_BLOCK_SIZE 128
#else
#define MBEDTLS_MD_MAX_BLOCK_SIZE 64
#endif
/**
* Opaque struct defined in md_internal.h.
*/
typedef struct mbedtls_md_info_t mbedtls_md_info_t;
/**
* The generic message-digest context.
*/
typedef struct mbedtls_md_context_t
{
/** Information about the associated message digest. */
const mbedtls_md_info_t *md_info;
/** The digest-specific context. */
void *md_ctx;
/** The HMAC part of the context. */
void *hmac_ctx;
} mbedtls_md_context_t;
/**
* \brief This function returns the list of digests supported by the
* generic digest module.
*
* \return 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 int *mbedtls_md_list( void );
/**
* \brief This function returns the message-digest information
* associated with the given digest name.
*
* \param md_name The name of the digest to search for.
*
* \return The message-digest information associated with \p md_name.
* \return NULL if the associated message-digest information is not found.
*/
const mbedtls_md_info_t *mbedtls_md_info_from_string( const char *md_name );
/**
* \brief This function returns the message-digest information
* associated with the given digest type.
*
* \param md_type The type of digest to search for.
*
* \return The message-digest information associated with \p md_type.
* \return NULL if the associated message-digest information is not found.
*/
const mbedtls_md_info_t *mbedtls_md_info_from_type( mbedtls_md_type_t md_type );
/**
* \brief 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_init( mbedtls_md_context_t *ctx );
/**
* \brief This function clears the internal structure of \p ctx and
* frees any embedded internal structure, but does not free
* \p ctx itself.
*
* If you have called mbedtls_md_setup() on \p 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().
*/
void mbedtls_md_free( mbedtls_md_context_t *ctx );
#if ! defined(MBEDTLS_DEPRECATED_REMOVED)
#if defined(MBEDTLS_DEPRECATED_WARNING)
#define MBEDTLS_DEPRECATED __attribute__((deprecated))
#else
#define MBEDTLS_DEPRECATED
#endif
/**
* \brief 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.
*
* \deprecated Superseded by mbedtls_md_setup() in 2.0.0
*
* \param ctx The context to set up.
* \param md_info The information structure of the message-digest algorithm
* to use.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification
* failure.
* \return #MBEDTLS_ERR_MD_ALLOC_FAILED on memory-allocation failure.
*/
int mbedtls_md_init_ctx( mbedtls_md_context_t *ctx, const mbedtls_md_info_t *md_info ) MBEDTLS_DEPRECATED;
#undef MBEDTLS_DEPRECATED
#endif /* MBEDTLS_DEPRECATED_REMOVED */
/**
* \brief 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.
*
* \param ctx The context to set up.
* \param md_info The information structure of the message-digest algorithm
* to use.
* \param hmac Defines if HMAC is used. 0: HMAC is not used (saves some memory),
* or non-zero: HMAC is used with this context.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification
* failure.
* \return #MBEDTLS_ERR_MD_ALLOC_FAILED on memory-allocation failure.
*/
int mbedtls_md_setup( mbedtls_md_context_t *ctx, const mbedtls_md_info_t *md_info, int hmac );
/**
* \brief This function clones the state of an message-digest
* context.
*
* \note You must call mbedtls_md_setup() on \c 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.
*
* \param dst The destination context.
* \param src The context to be cloned.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification failure.
*/
int mbedtls_md_clone( mbedtls_md_context_t *dst,
const mbedtls_md_context_t *src );
/**
* \brief This function extracts the message-digest size from the
* message-digest information structure.
*
* \param md_info The information structure of the message-digest algorithm
* to use.
*
* \return The size of the message-digest output in Bytes.
*/
unsigned char mbedtls_md_get_size( const mbedtls_md_info_t *md_info );
/**
* \brief This function extracts the message-digest type from the
* message-digest information structure.
*
* \param md_info The information structure of the message-digest algorithm
* to use.
*
* \return The type of the message digest.
*/
mbedtls_md_type_t mbedtls_md_get_type( const mbedtls_md_info_t *md_info );
/**
* \brief This function extracts the message-digest name from the
* message-digest information structure.
*
* \param md_info The information structure of the message-digest algorithm
* to use.
*
* \return The name of the message digest.
*/
const char *mbedtls_md_get_name( const mbedtls_md_info_t *md_info );
/**
* \brief 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().
*
* \param ctx The generic message-digest context.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification
* failure.
*/
int mbedtls_md_starts( mbedtls_md_context_t *ctx );
/**
* \brief 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().
*
* \param ctx The generic message-digest context.
* \param input The buffer holding the input data.
* \param ilen The length of the input data.
*
* \return \c 0 on success.
* \return #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 );
/**
* \brief 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.
*
* \param ctx The generic message-digest context.
* \param output The buffer for the generic message-digest checksum result.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification
* failure.
*/
int mbedtls_md_finish( mbedtls_md_context_t *ctx, unsigned char *output );
/**
* \brief 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).
*
* \param md_info The information structure of the message-digest algorithm
* to use.
* \param input The buffer holding the data.
* \param ilen The length of the input data.
* \param output The generic message-digest checksum result.
*
* \return \c 0 on success.
* \return #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 );
#if defined(MBEDTLS_FS_IO)
/**
* \brief 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).
*
* \param md_info The information structure of the message-digest algorithm
* to use.
* \param path The input file name.
* \param output The generic message-digest checksum result.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_MD_FILE_IO_ERROR on an I/O error accessing
* the file pointed by \p path.
* \return #MBEDTLS_ERR_MD_BAD_INPUT_DATA if \p md_info was NULL.
*/
int mbedtls_md_file( const mbedtls_md_info_t *md_info, const char *path,
unsigned char *output );
#endif /* MBEDTLS_FS_IO */
/**
* \brief 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.
*
* \param ctx The message digest context containing an embedded HMAC
* context.
* \param key The HMAC secret key.
* \param keylen The length of the HMAC key in Bytes.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification
* failure.
*/
int mbedtls_md_hmac_starts( mbedtls_md_context_t *ctx, const unsigned char *key,
size_t keylen );
/**
* \brief 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().
*
* \param ctx The message digest context containing an embedded HMAC
* context.
* \param input The buffer holding the input data.
* \param ilen The length of the input data.
*
* \return \c 0 on success.
* \return #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 );
/**
* \brief 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.
*
* \param ctx The message digest context containing an embedded HMAC
* context.
* \param output The generic HMAC checksum result.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification
* failure.
*/
int mbedtls_md_hmac_finish( mbedtls_md_context_t *ctx, unsigned char *output);
/**
* \brief 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.
*
* \param ctx The message digest context containing an embedded HMAC
* context.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification
* failure.
*/
int mbedtls_md_hmac_reset( mbedtls_md_context_t *ctx );
/**
* \brief 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).
*
* \param md_info The information structure of the message-digest algorithm
* to use.
* \param key The HMAC secret key.
* \param keylen The length of the HMAC secret key in Bytes.
* \param input The buffer holding the input data.
* \param ilen The length of the input data.
* \param output The generic HMAC result.
*
* \return \c 0 on success.
* \return #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 );
/* Internal use */
int mbedtls_md_process( mbedtls_md_context_t *ctx, const unsigned char *data );
#ifdef __cplusplus
}
#endif
#endif /* MBEDTLS_MD_H */