366 lines
17 KiB
C++
366 lines
17 KiB
C++
/*
|
|
* Copyright The Mbed TLS Contributors
|
|
* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
|
|
*/
|
|
|
|
/**
|
|
* \file mps_reader.h
|
|
*
|
|
* \brief This file defines reader objects, which together with their
|
|
* sibling writer objects form the basis for the communication
|
|
* between the various layers of the Mbed TLS messaging stack,
|
|
* as well as the communication between the messaging stack and
|
|
* the (D)TLS handshake protocol implementation.
|
|
*
|
|
* Readers provide a means of transferring incoming data from
|
|
* a 'producer' providing it in chunks of arbitrary size, to
|
|
* a 'consumer' which fetches and processes it in chunks of
|
|
* again arbitrary, and potentially different, size.
|
|
*
|
|
* Readers can thus be seen as datagram-to-stream converters,
|
|
* and they abstract away the following two tasks from the user:
|
|
* 1. The pointer arithmetic of stepping through a producer-
|
|
* provided chunk in smaller chunks.
|
|
* 2. The merging of incoming data chunks in case the
|
|
* consumer requests data in larger chunks than what the
|
|
* producer provides.
|
|
*
|
|
* The basic abstract flow of operation is the following:
|
|
* - Initially, the reader is in 'producing mode'.
|
|
* - The producer hands an incoming data buffer to the reader,
|
|
* moving it from 'producing' to 'consuming' mode.
|
|
* - The consumer subsequently fetches and processes the buffer
|
|
* content. Once that's done -- or partially done and a consumer's
|
|
* request can't be fulfilled -- the producer revokes the reader's
|
|
* access to the incoming data buffer, putting the reader back to
|
|
* producing mode.
|
|
* - The producer subsequently gathers more incoming data and hands
|
|
* it to the reader until it switches back to consuming mode
|
|
* if enough data is available for the last consumer request to
|
|
* be satisfiable.
|
|
* - Repeat the above.
|
|
*
|
|
* The abstract states of the reader from the producer's and
|
|
* consumer's perspective are as follows:
|
|
*
|
|
* - From the perspective of the consumer, the state of the
|
|
* reader consists of the following:
|
|
* - A byte stream representing (concatenation of) the data
|
|
* received through calls to mbedtls_mps_reader_get(),
|
|
* - A marker within that byte stream indicating which data
|
|
* can be considered processed, and hence need not be retained,
|
|
* when the reader is passed back to the producer via
|
|
* mbedtls_mps_reader_reclaim().
|
|
* The marker is set via mbedtls_mps_reader_commit()
|
|
* which places it at the end of the current byte stream.
|
|
* The consumer need not be aware of the distinction between consumer
|
|
* and producer mode, because it only interfaces with the reader
|
|
* when the latter is in consuming mode.
|
|
*
|
|
* - From the perspective of the producer, the reader's state is one of:
|
|
* - Attached: The reader is in consuming mode.
|
|
* - Unset: No incoming data buffer is currently managed by the reader,
|
|
* and all previously handed incoming data buffers have been
|
|
* fully processed. More data needs to be fed into the reader
|
|
* via mbedtls_mps_reader_feed().
|
|
*
|
|
* - Accumulating: No incoming data buffer is currently managed by the
|
|
* reader, but some data from the previous incoming data
|
|
* buffer hasn't been processed yet and is internally
|
|
* held back.
|
|
* The Attached state belongs to consuming mode, while the Unset and
|
|
* Accumulating states belong to producing mode.
|
|
*
|
|
* Transitioning from the Unset or Accumulating state to Attached is
|
|
* done via successful calls to mbedtls_mps_reader_feed(), while
|
|
* transitioning from Attached to either Unset or Accumulating (depending
|
|
* on what has been processed) is done via mbedtls_mps_reader_reclaim().
|
|
*
|
|
* The following diagram depicts the producer-state progression:
|
|
*
|
|
* +------------------+ reclaim
|
|
* | Unset +<-------------------------------------+ get
|
|
* +--------|---------+ | +------+
|
|
* | | | |
|
|
* | | | |
|
|
* | feed +---------+---+--+ |
|
|
* +--------------------------------------> <---+
|
|
* | Attached |
|
|
* +--------------------------------------> <---+
|
|
* | feed, enough data available +---------+---+--+ |
|
|
* | to serve previous consumer request | | |
|
|
* | | | |
|
|
* +--------+---------+ | +------+
|
|
* +----> Accumulating |<-------------------------------------+ commit
|
|
* | +---+--------------+ reclaim, previous read request
|
|
* | | couldn't be fulfilled
|
|
* | |
|
|
* +--------+
|
|
* feed, need more data to serve
|
|
* previous consumer request
|
|
* |
|
|
* |
|
|
* producing mode | consuming mode
|
|
* |
|
|
*
|
|
*/
|
|
|
|
#ifndef MBEDTLS_READER_H
|
|
#define MBEDTLS_READER_H
|
|
|
|
#include <stdio.h>
|
|
|
|
#include "mps_common.h"
|
|
#include "mps_error.h"
|
|
|
|
struct mbedtls_mps_reader;
|
|
typedef struct mbedtls_mps_reader mbedtls_mps_reader;
|
|
|
|
/*
|
|
* Structure definitions
|
|
*/
|
|
|
|
struct mbedtls_mps_reader {
|
|
unsigned char *frag; /*!< The fragment of incoming data managed by
|
|
* the reader; it is provided to the reader
|
|
* through mbedtls_mps_reader_feed(). The reader
|
|
* does not own the fragment and does not
|
|
* perform any allocation operations on it,
|
|
* but does have read and write access to it.
|
|
*
|
|
* The reader is in consuming mode if
|
|
* and only if \c frag is not \c NULL. */
|
|
mbedtls_mps_stored_size_t frag_len;
|
|
/*!< The length of the current fragment.
|
|
* Must be 0 if \c frag == \c NULL. */
|
|
mbedtls_mps_stored_size_t commit;
|
|
/*!< The offset of the last commit, relative
|
|
* to the first byte in the fragment, if
|
|
* no accumulator is present. If an accumulator
|
|
* is present, it is viewed as a prefix to the
|
|
* current fragment, and this variable contains
|
|
* an offset from the beginning of the accumulator.
|
|
*
|
|
* This is only used when the reader is in
|
|
* consuming mode, i.e. \c frag != \c NULL;
|
|
* otherwise, its value is \c 0. */
|
|
mbedtls_mps_stored_size_t end;
|
|
/*!< The offset of the end of the last chunk
|
|
* passed to the user through a call to
|
|
* mbedtls_mps_reader_get(), relative to the first
|
|
* byte in the fragment, if no accumulator is
|
|
* present. If an accumulator is present, it is
|
|
* viewed as a prefix to the current fragment, and
|
|
* this variable contains an offset from the
|
|
* beginning of the accumulator.
|
|
*
|
|
* This is only used when the reader is in
|
|
* consuming mode, i.e. \c frag != \c NULL;
|
|
* otherwise, its value is \c 0. */
|
|
mbedtls_mps_stored_size_t pending;
|
|
/*!< The amount of incoming data missing on the
|
|
* last call to mbedtls_mps_reader_get().
|
|
* In particular, it is \c 0 if the last call
|
|
* was successful.
|
|
* If a reader is reclaimed after an
|
|
* unsuccessful call to mbedtls_mps_reader_get(),
|
|
* this variable is used to have the reader
|
|
* remember how much data should be accumulated
|
|
* so that the call to mbedtls_mps_reader_get()
|
|
* succeeds next time.
|
|
* This is only used when the reader is in
|
|
* consuming mode, i.e. \c frag != \c NULL;
|
|
* otherwise, its value is \c 0. */
|
|
|
|
/* The accumulator is only needed if we need to be able to pause
|
|
* the reader. A few bytes could be saved by moving this to a
|
|
* separate struct and using a pointer here. */
|
|
|
|
unsigned char *acc; /*!< The accumulator is used to gather incoming
|
|
* data if a read-request via mbedtls_mps_reader_get()
|
|
* cannot be served from the current fragment. */
|
|
mbedtls_mps_stored_size_t acc_len;
|
|
/*!< The total size of the accumulator. */
|
|
mbedtls_mps_stored_size_t acc_available;
|
|
/*!< The number of bytes currently gathered in
|
|
* the accumulator. This is both used in
|
|
* producing and in consuming mode:
|
|
* While producing, it is increased until
|
|
* it reaches the value of \c acc_remaining below.
|
|
* While consuming, it is used to judge if a
|
|
* get request can be served from the
|
|
* accumulator or not.
|
|
* Must not be larger than \c acc_len. */
|
|
union {
|
|
mbedtls_mps_stored_size_t acc_remaining;
|
|
/*!< This indicates the amount of data still
|
|
* to be gathered in the accumulator. It is
|
|
* only used in producing mode.
|
|
* Must be at most acc_len - acc_available. */
|
|
mbedtls_mps_stored_size_t frag_offset;
|
|
/*!< If an accumulator is present and in use, this
|
|
* field indicates the offset of the current
|
|
* fragment from the beginning of the
|
|
* accumulator. If no accumulator is present
|
|
* or the accumulator is not in use, this is \c 0.
|
|
* It is only used in consuming mode.
|
|
* Must not be larger than \c acc_available. */
|
|
} acc_share;
|
|
};
|
|
|
|
/*
|
|
* API organization:
|
|
* A reader object is usually prepared and maintained
|
|
* by some lower layer and passed for usage to an upper
|
|
* layer, and the API naturally splits according to which
|
|
* layer is supposed to use the respective functions.
|
|
*/
|
|
|
|
/*
|
|
* Maintenance API (Lower layer)
|
|
*/
|
|
|
|
/**
|
|
* \brief Initialize a reader object
|
|
*
|
|
* \param reader The reader to be initialized.
|
|
* \param acc The buffer to be used as a temporary accumulator
|
|
* in case get requests through mbedtls_mps_reader_get()
|
|
* exceed the buffer provided by mbedtls_mps_reader_feed().
|
|
* This buffer is owned by the caller and exclusive use
|
|
* for reading and writing is given to the reader for the
|
|
* duration of the reader's lifetime. It is thus the caller's
|
|
* responsibility to maintain (and not touch) the buffer for
|
|
* the lifetime of the reader, and to properly zeroize and
|
|
* free the memory after the reader has been destroyed.
|
|
* \param acc_len The size in Bytes of \p acc.
|
|
*
|
|
* \return \c 0 on success.
|
|
* \return A negative \c MBEDTLS_ERR_READER_XXX error code on failure.
|
|
*/
|
|
int mbedtls_mps_reader_init(mbedtls_mps_reader *reader,
|
|
unsigned char *acc,
|
|
mbedtls_mps_size_t acc_len);
|
|
|
|
/**
|
|
* \brief Free a reader object
|
|
*
|
|
* \param reader The reader to be freed.
|
|
*
|
|
* \return \c 0 on success.
|
|
* \return A negative \c MBEDTLS_ERR_READER_XXX error code on failure.
|
|
*/
|
|
int mbedtls_mps_reader_free(mbedtls_mps_reader *reader);
|
|
|
|
/**
|
|
* \brief Pass chunk of data for the reader to manage.
|
|
*
|
|
* \param reader The reader context to use. The reader must be
|
|
* in producing mode.
|
|
* \param buf The buffer to be managed by the reader.
|
|
* \param buflen The size in Bytes of \p buffer.
|
|
*
|
|
* \return \c 0 on success. In this case, the reader will be
|
|
* moved to consuming mode and obtains read access
|
|
* of \p buf until mbedtls_mps_reader_reclaim()
|
|
* is called. It is the responsibility of the caller
|
|
* to ensure that the \p buf persists and is not changed
|
|
* between successful calls to mbedtls_mps_reader_feed()
|
|
* and mbedtls_mps_reader_reclaim().
|
|
* \return \c MBEDTLS_ERR_MPS_READER_NEED_MORE if more input data is
|
|
* required to fulfill a previous request to mbedtls_mps_reader_get().
|
|
* In this case, the reader remains in producing mode and
|
|
* takes no ownership of the provided buffer (an internal copy
|
|
* is made instead).
|
|
* \return Another negative \c MBEDTLS_ERR_READER_XXX error code on
|
|
* different kinds of failures.
|
|
*/
|
|
int mbedtls_mps_reader_feed(mbedtls_mps_reader *reader,
|
|
unsigned char *buf,
|
|
mbedtls_mps_size_t buflen);
|
|
|
|
/**
|
|
* \brief Reclaim reader's access to the current input buffer.
|
|
*
|
|
* \param reader The reader context to use. The reader must be
|
|
* in consuming mode.
|
|
* \param paused If not \c NULL, the integer at address \p paused will be
|
|
* modified to indicate whether the reader has been paused
|
|
* (value \c 1) or not (value \c 0). Pausing happens if there
|
|
* is uncommitted data and a previous request to
|
|
* mbedtls_mps_reader_get() has exceeded the bounds of the
|
|
* input buffer.
|
|
*
|
|
* \return \c 0 on success.
|
|
* \return A negative \c MBEDTLS_ERR_READER_XXX error code on failure.
|
|
*/
|
|
int mbedtls_mps_reader_reclaim(mbedtls_mps_reader *reader,
|
|
int *paused);
|
|
|
|
/*
|
|
* Usage API (Upper layer)
|
|
*/
|
|
|
|
/**
|
|
* \brief Request data from the reader.
|
|
*
|
|
* \param reader The reader context to use. The reader must
|
|
* be in consuming mode.
|
|
* \param desired The desired amount of data to be read, in Bytes.
|
|
* \param buffer The address to store the buffer pointer in.
|
|
* This must not be \c NULL.
|
|
* \param buflen The address to store the actual buffer
|
|
* length in, or \c NULL.
|
|
*
|
|
* \return \c 0 on success. In this case, \c *buf holds the
|
|
* address of a buffer of size \c *buflen
|
|
* (if \c buflen != \c NULL) or \c desired
|
|
* (if \c buflen == \c NULL). The user has read access
|
|
* to the buffer and guarantee of stability of the data
|
|
* until the next call to mbedtls_mps_reader_reclaim().
|
|
* \return #MBEDTLS_ERR_MPS_READER_OUT_OF_DATA if there is not enough
|
|
* data available to serve the get request. In this case, the
|
|
* reader remains intact and in consuming mode, and the consumer
|
|
* should retry the call after a successful cycle of
|
|
* mbedtls_mps_reader_reclaim() and mbedtls_mps_reader_feed().
|
|
* If, after such a cycle, the consumer requests a different
|
|
* amount of data, the result is implementation-defined;
|
|
* progress is guaranteed only if the same amount of data
|
|
* is requested after a mbedtls_mps_reader_reclaim() and
|
|
* mbedtls_mps_reader_feed() cycle.
|
|
* \return Another negative \c MBEDTLS_ERR_READER_XXX error
|
|
* code for different kinds of failure.
|
|
*
|
|
* \note Passing \c NULL as \p buflen is a convenient way to
|
|
* indicate that fragmentation is not tolerated.
|
|
* It's functionally equivalent to passing a valid
|
|
* address as buflen and checking \c *buflen == \c desired
|
|
* afterwards.
|
|
*/
|
|
int mbedtls_mps_reader_get(mbedtls_mps_reader *reader,
|
|
mbedtls_mps_size_t desired,
|
|
unsigned char **buffer,
|
|
mbedtls_mps_size_t *buflen);
|
|
|
|
/**
|
|
* \brief Mark data obtained from mbedtls_mps_reader_get() as processed.
|
|
*
|
|
* This call indicates that all data received from prior calls to
|
|
* mbedtls_mps_reader_get() has been or will have been
|
|
* processed when mbedtls_mps_reader_reclaim() is called,
|
|
* and thus need not be backed up.
|
|
*
|
|
* This function has no user observable effect until
|
|
* mbedtls_mps_reader_reclaim() is called. In particular,
|
|
* buffers received from mbedtls_mps_reader_get() remain
|
|
* valid until mbedtls_mps_reader_reclaim() is called.
|
|
*
|
|
* \param reader The reader context to use.
|
|
*
|
|
* \return \c 0 on success.
|
|
* \return A negative \c MBEDTLS_ERR_READER_XXX error code on failure.
|
|
*
|
|
*/
|
|
int mbedtls_mps_reader_commit(mbedtls_mps_reader *reader);
|
|
|
|
#endif /* MBEDTLS_READER_H */
|