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mbedtls/library/mps/reader.c
Hanno Becker b910016049 Add MPS trace module implementation 
This commit adds an implementation of the MPS trace module
based on `printf()`.

The enabling macro MBEDTLS_MPS_TRACE remains unset by default
because MPS tracing is very verbose and consumes unnecessary
space in the CI.

Signed-off-by: Hanno Becker <hanno.becker@arm.com>
2021-03-29 14:19:32 +01:00

513 lines
17 KiB
C
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/*
* Message Processing Stack, Reader implementation
*
* Copyright The Mbed TLS Contributors
* 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)
*/
#include "reader.h"
#include "common.h"
#include "trace.h"
#include <string.h>
#if ( defined(__ARMCC_VERSION) || defined(_MSC_VER) ) && \
!defined(inline) && !defined(__cplusplus)
#define inline __inline
#endif
#if defined(MBEDTLS_MPS_TRACE)
static int trace_id = TRACE_BIT_READER;
#endif /* MBEDTLS_MPS_TRACE */
/*
* GENERAL NOTE ON CODING STYLE
*
* The following code intentionally separates memory loads
* and stores from other operations (arithmetic or branches).
* This leads to the introduction of many local variables
* and significantly increases the C-code line count, but
* should not increase the size of generated assembly.
*
* This reason for this is twofold:
* (1) It will ease verification efforts using the VST
* whose program logic cannot directly reason
* about instructions containing a load or store in
* addition to other operations (e.g. *p = *q or
* tmp = *p + 42).
* (2) Operating on local variables and writing the results
* back to the target contexts on success only
* allows to maintain structure invariants even
* on failure - this in turn has two benefits:
* (2.a) If for some reason an error code is not caught
* and operation continues, functions are nonetheless
* called with sane contexts, reducing the risk
* of dangerous behavior.
* (2.b) Randomized testing is easier if structures
* remain intact even in the face of failing
* and/or non-sensical calls.
* Moreover, it might even reduce code-size because
* the compiler need not write back temporary results
* to memory in case of failure.
*
*/
static inline void mps_reader_zero( mbedtls_reader *rd )
{
/* A plain memset() would likely be more efficient,
* but the current way of zeroing makes it harder
* to overlook fields which should not be zero-initialized.
* It's also more suitable for VF efforts since it
* doesn't require reasoning about structs being
* interpreted as unstructured binary blobs. */
static mbedtls_reader const zero =
{ .frag = NULL,
.frag_len = 0,
.commit = 0,
.end = 0,
.pending = 0,
.acc = NULL,
.acc_len = 0,
.acc_avail = 0,
.acc_share = { .acc_remaining = 0 }
};
*rd = zero;
}
int mbedtls_reader_init( mbedtls_reader *rd,
unsigned char *acc,
mbedtls_mps_size_t acc_len )
{
TRACE_INIT( "reader_init, acc len %u", (unsigned) acc_len );
mps_reader_zero( rd );
rd->acc = acc;
rd->acc_len = acc_len;
RETURN( 0 );
}
int mbedtls_reader_free( mbedtls_reader *rd )
{
TRACE_INIT( "reader_free" );
mps_reader_zero( rd );
RETURN( 0 );
}
int mbedtls_reader_feed( mbedtls_reader *rd,
unsigned char *new_frag,
mbedtls_mps_size_t new_frag_len )
{
unsigned char *acc;
mbedtls_mps_size_t copy_to_acc;
TRACE_INIT( "reader_feed, frag %p, len %u",
(void*) new_frag, (unsigned) new_frag_len );
if( new_frag == NULL )
RETURN( MBEDTLS_ERR_MPS_READER_INVALID_ARG );
MBEDTLS_MPS_STATE_VALIDATE_RAW( rd->frag == NULL,
"mbedtls_reader_feed() requires reader to be in producing mode" );
acc = rd->acc;
if( acc != NULL )
{
mbedtls_mps_size_t aa, ar;
ar = rd->acc_share.acc_remaining;
aa = rd->acc_avail;
copy_to_acc = ar;
if( copy_to_acc > new_frag_len )
copy_to_acc = new_frag_len;
acc += aa;
if( copy_to_acc > 0 )
memcpy( acc, new_frag, copy_to_acc );
TRACE( trace_comment, "Copy new data of size %u of %u into accumulator at offset %u",
(unsigned) copy_to_acc, (unsigned) new_frag_len, (unsigned) aa );
/* Check if, with the new fragment, we have enough data. */
ar -= copy_to_acc;
if( ar > 0 )
{
/* Need more data */
aa += copy_to_acc;
rd->acc_share.acc_remaining = ar;
rd->acc_avail = aa;
RETURN( MBEDTLS_ERR_MPS_READER_NEED_MORE );
}
TRACE( trace_comment, "Enough data available to serve user request" );
rd->acc_share.frag_offset = aa;
aa += copy_to_acc;
rd->acc_avail = aa;
}
else
{
rd->acc_share.frag_offset = 0;
}
rd->frag = new_frag;
rd->frag_len = new_frag_len;
rd->commit = 0;
rd->end = 0;
RETURN( 0 );
}
int mbedtls_reader_get( mbedtls_reader *rd,
mbedtls_mps_size_t desired,
unsigned char **buffer,
mbedtls_mps_size_t *buflen )
{
unsigned char *frag, *acc;
mbedtls_mps_size_t end, fo, fl, frag_fetched, frag_remaining;
TRACE_INIT( "reader_get %p, desired %u", (void*) rd, (unsigned) desired );
frag = rd->frag;
MBEDTLS_MPS_STATE_VALIDATE_RAW( frag != NULL,
"mbedtls_reader_get() requires reader to be in consuming mode" );
/* The fragment offset indicates the offset of the fragment
* from the accmulator, if the latter is present. Use a offset
* of \c 0 if no accumulator is used. */
acc = rd->acc;
if( acc == NULL )
fo = 0;
else
fo = rd->acc_share.frag_offset;
TRACE( trace_comment, "frag_off %u, end %u, acc_avail %d",
(unsigned) fo, (unsigned) rd->end,
acc == NULL ? -1 : (int) rd->acc_avail );
/* Check if we're still serving from the accumulator. */
end = rd->end;
if( end < fo )
{
TRACE( trace_comment, "Serve the request from the accumulator" );
if( fo - end < desired )
{
/* Illustration of supported and unsupported cases:
*
* - Allowed #1
*
* +-----------------------------------+
* | frag |
* +-----------------------------------+
*
* end end+desired
* | |
* +-----v-------v-------------+
* | acc |
* +---------------------------+
* | |
* fo/frag_offset aa/acc_avail
*
* - Allowed #2
*
* +-----------------------------------+
* | frag |
* +-----------------------------------+
*
* end end+desired
* | |
* +----------v----------------v
* | acc |
* +---------------------------+
* | |
* fo/frag_offset aa/acc_avail
*
* - Not allowed #1 (could be served, but we don't actually use it):
*
* +-----------------------------------+
* | frag |
* +-----------------------------------+
*
* end end+desired
* | |
* +------v-------------v------+
* | acc |
* +---------------------------+
* | |
* fo/frag_offset aa/acc_avail
*
*
* - Not allowed #2 (can't be served with a contiguous buffer):
*
* +-----------------------------------+
* | frag |
* +-----------------------------------+
*
* end end + desired
* | |
* +------v--------------------+ v
* | acc |
* +---------------------------+
* | |
* fo/frag_offset aa/acc_avail
*
* In case of Allowed #1 and #2 we're switching to serve from
* `frag` starting from the next call to mbedtls_reader_get().
*/
mbedtls_mps_size_t aa;
aa = rd->acc_avail;
if( aa - end != desired )
{
/* It might be possible to serve some of these situations by
* making additional space in the accumulator, removing those
* parts that have already been committed.
* On the other hand, this brings additional complexity and
* enlarges the code size, while there doesn't seem to be a use
* case where we don't attempt exactly the same `get` calls when
* resuming on a reader than what we tried before pausing it.
* If we believe we adhere to this restricted usage throughout
* the library, this check is a good opportunity to
* validate this. */
RETURN( MBEDTLS_ERR_MPS_READER_INCONSISTENT_REQUESTS );
}
}
acc += end;
*buffer = acc;
if( buflen != NULL )
*buflen = desired;
end += desired;
rd->end = end;
rd->pending = 0;
RETURN( 0 );
}
/* Attempt to serve the request from the current fragment */
TRACE( trace_comment, "Serve the request from the current fragment." );
fl = rd->frag_len;
frag_fetched = end - fo; /* The amount of data from the current fragment
* that has already been passed to the user. */
frag += frag_fetched;
frag_remaining = fl - frag_fetched; /* Remaining data in fragment */
/* Check if we can serve the read request from the fragment. */
if( frag_remaining < desired )
{
TRACE( trace_comment, "There's not enough data in the current fragment to serve the request." );
/* There's not enough data in the current fragment,
* so either just RETURN what we have or fail. */
if( buflen == NULL )
{
if( frag_remaining > 0 )
{
rd->pending = desired - frag_remaining;
TRACE( trace_comment, "Remember to collect %u bytes before re-opening",
(unsigned) rd->pending );
}
RETURN( MBEDTLS_ERR_MPS_READER_OUT_OF_DATA );
}
desired = frag_remaining;
}
/* There's enough data in the current fragment to serve the
* (potentially modified) read request. */
*buffer = frag;
if( buflen != NULL )
*buflen = desired;
end += desired;
rd->end = end;
rd->pending = 0;
RETURN( 0 );
}
int mbedtls_reader_commit( mbedtls_reader *rd )
{
unsigned char *acc;
mbedtls_mps_size_t aa, end, fo, shift;
TRACE_INIT( "reader_commit" );
MBEDTLS_MPS_STATE_VALIDATE_RAW( rd->frag != NULL,
"mbedtls_reader_commit() requires reader to be in consuming mode" );
acc = rd->acc;
end = rd->end;
if( acc == NULL )
{
TRACE( trace_comment, "No accumulator, just shift end" );
rd->commit = end;
RETURN( 0 );
}
fo = rd->acc_share.frag_offset;
if( end >= fo )
{
TRACE( trace_comment, "Started to serve fragment, get rid of accumulator" );
shift = fo;
aa = 0;
}
else
{
TRACE( trace_comment, "Still serving from accumulator" );
aa = rd->acc_avail;
shift = end;
memmove( acc, acc + shift, aa - shift );
aa -= shift;
}
end -= shift;
fo -= shift;
rd->acc_share.frag_offset = fo;
rd->acc_avail = aa;
rd->commit = end;
rd->end = end;
TRACE( trace_comment, "Final state: (end=commit,fo,avail) = (%u,%u,%u)",
(unsigned) end, (unsigned) fo, (unsigned) aa );
RETURN( 0 );
}
int mbedtls_reader_reclaim( mbedtls_reader *rd,
mbedtls_mps_size_t *paused )
{
unsigned char *frag, *acc;
mbedtls_mps_size_t pending, commit;
mbedtls_mps_size_t al, fo, fl;
TRACE_INIT( "reader_reclaim" );
if( paused != NULL )
*paused = 0;
frag = rd->frag;
MBEDTLS_MPS_STATE_VALIDATE_RAW( frag != NULL,
"mbedtls_reader_reclaim() requires reader to be in consuming mode" );
acc = rd->acc;
pending = rd->pending;
commit = rd->commit;
fl = rd->frag_len;
if( acc == NULL )
fo = 0;
else
fo = rd->acc_share.frag_offset;
if( pending == 0 )
{
TRACE( trace_comment, "No unsatisfied read-request has been logged." );
/* Check if there's data left to be consumed. */
if( commit < fo || commit - fo < fl )
{
TRACE( trace_comment, "There is data left to be consumed." );
rd->end = commit;
RETURN( MBEDTLS_ERR_MPS_READER_DATA_LEFT );
}
TRACE( trace_comment, "The fragment has been completely processed and committed." );
}
else
{
mbedtls_mps_size_t frag_backup_offset;
mbedtls_mps_size_t frag_backup_len;
TRACE( trace_comment, "There has been an unsatisfied read-request with %u bytes overhead.",
(unsigned) pending );
if( acc == NULL )
{
TRACE( trace_comment, "No accumulator present" );
RETURN( MBEDTLS_ERR_MPS_READER_NEED_ACCUMULATOR );
}
al = rd->acc_len;
/* Check if the upper layer has already fetched
* and committed the contents of the accumulator. */
if( commit < fo )
{
/* No, accumulator is still being processed. */
int overflow;
TRACE( trace_comment, "Still processing data from the accumulator" );
overflow =
( fo + fl < fo ) || ( fo + fl + pending < fo + fl );
if( overflow || al < fo + fl + pending )
{
rd->end = commit;
rd->pending = 0;
TRACE( trace_error, "The accumulator is too small to handle the backup." );
TRACE( trace_error, "* Remaining size: %u", (unsigned) al );
TRACE( trace_error, "* Needed: %u (%u + %u + %u)",
(unsigned) ( fo + fl + pending ),
(unsigned) fo, (unsigned) fl, (unsigned) pending );
RETURN( MBEDTLS_ERR_MPS_READER_ACCUMULATOR_TOO_SMALL );
}
frag_backup_offset = 0;
frag_backup_len = fl;
}
else
{
/* Yes, the accumulator is already processed. */
int overflow;
TRACE( trace_comment, "The accumulator has already been processed" );
frag_backup_offset = commit;
frag_backup_len = fl - commit;
overflow = ( frag_backup_len + pending < pending );
if( overflow ||
al - fo < frag_backup_len + pending )
{
rd->end = commit;
rd->pending = 0;
TRACE( trace_error, "The accumulator is too small to handle the backup." );
TRACE( trace_error, "* Remaining size: %u", (unsigned) ( al - fo ) );
TRACE( trace_error, "* Needed: %u (%u + %u)",
(unsigned) ( frag_backup_len + pending ),
(unsigned) frag_backup_len, (unsigned) pending );
RETURN( MBEDTLS_ERR_MPS_READER_ACCUMULATOR_TOO_SMALL );
}
}
frag += frag_backup_offset;
acc += fo;
memcpy( acc, frag, frag_backup_len );
TRACE( trace_comment, "Backup %u bytes into accumulator",
(unsigned) frag_backup_len );
rd->acc_avail = fo + frag_backup_len;
rd->acc_share.acc_remaining = pending;
if( paused != NULL )
*paused = 1;
}
rd->frag = NULL;
rd->frag_len = 0;
rd->commit = 0;
rd->end = 0;
rd->pending = 0;
TRACE( trace_comment, "Final state: aa %u, al %u, ar %u",
(unsigned) rd->acc_avail, (unsigned) rd->acc_len,
(unsigned) rd->acc_share.acc_remaining );
RETURN( 0 );
}
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