557 lines
19 KiB
C
557 lines
19 KiB
C
/*
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* Message Processing Stack, Reader implementation
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*
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* Copyright The Mbed TLS Contributors
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* This file is part of Mbed TLS (https://tls.mbed.org)
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*/
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#include "mps_reader.h"
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#include "mps_common.h"
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#include "mps_trace.h"
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#include <string.h>
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#if ( defined(__ARMCC_VERSION) || defined(_MSC_VER) ) && \
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!defined(inline) && !defined(__cplusplus)
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#define inline __inline
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#endif
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#if defined(MBEDTLS_MPS_ENABLE_TRACE)
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static int mbedtls_mps_trace_id = MBEDTLS_MPS_TRACE_BIT_READER;
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#endif /* MBEDTLS_MPS_ENABLE_TRACE */
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/*
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* GENERAL NOTE ON CODING STYLE
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*
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* The following code intentionally separates memory loads
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* and stores from other operations (arithmetic or branches).
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* This leads to the introduction of many local variables
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* and significantly increases the C-code line count, but
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* should not increase the size of generated assembly.
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*
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* This reason for this is twofold:
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* (1) It will ease verification efforts using the VST
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* whose program logic cannot directly reason
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* about instructions containing a load or store in
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* addition to other operations (e.g. *p = *q or
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* tmp = *p + 42).
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* (2) Operating on local variables and writing the results
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* back to the target contexts on success only
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* allows to maintain structure invariants even
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* on failure - this in turn has two benefits:
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* (2.a) If for some reason an error code is not caught
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* and operation continues, functions are nonetheless
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* called with sane contexts, reducing the risk
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* of dangerous behavior.
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* (2.b) Randomized testing is easier if structures
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* remain intact even in the face of failing
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* and/or non-sensical calls.
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* Moreover, it might even reduce code-size because
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* the compiler need not write back temporary results
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* to memory in case of failure.
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*
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*/
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static inline int mps_reader_is_accumulating(
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mbedtls_mps_reader const *rd )
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{
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mbedtls_mps_size_t ar;
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if( rd->acc == NULL )
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return( 0 );
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ar = rd->acc_share.acc_remaining;
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return( ar > 0 );
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}
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static inline int mps_reader_is_producing(
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mbedtls_mps_reader const *rd )
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{
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unsigned char *frag = rd->frag;
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return( frag == NULL );
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}
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static inline int mps_reader_is_consuming(
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mbedtls_mps_reader const *rd )
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{
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return( !mps_reader_is_producing( rd ) );
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}
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static inline mbedtls_mps_size_t mps_reader_get_fragment_offset(
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mbedtls_mps_reader const *rd )
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{
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unsigned char *acc = rd->acc;
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mbedtls_mps_size_t fo;
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if( acc == NULL )
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return( 0 );
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fo = rd->acc_share.frag_offset;
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return( fo );
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}
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static inline mbedtls_mps_size_t mps_reader_serving_from_accumulator(
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mbedtls_mps_reader const *rd )
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{
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mbedtls_mps_size_t fo, end;
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fo = mps_reader_get_fragment_offset( rd );
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end = rd->end;
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return( end < fo );
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}
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static inline void mps_reader_zero( mbedtls_mps_reader *rd )
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{
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/* A plain memset() would likely be more efficient,
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* but the current way of zeroing makes it harder
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* to overlook fields which should not be zero-initialized.
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* It's also more suitable for FV efforts since it
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* doesn't require reasoning about structs being
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* interpreted as unstructured binary blobs. */
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static mbedtls_mps_reader const zero =
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{ .frag = NULL,
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.frag_len = 0,
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.commit = 0,
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.end = 0,
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.pending = 0,
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.acc = NULL,
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.acc_len = 0,
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.acc_avail = 0,
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.acc_share = { .acc_remaining = 0 }
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};
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*rd = zero;
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}
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int mbedtls_mps_reader_init( mbedtls_mps_reader *rd,
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unsigned char *acc,
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mbedtls_mps_size_t acc_len )
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{
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MBEDTLS_MPS_TRACE_INIT( "mbedtls_mps_reader_init" );
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MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
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"* Accumulator size: %u bytes", (unsigned) acc_len );
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mps_reader_zero( rd );
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rd->acc = acc;
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rd->acc_len = acc_len;
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MBEDTLS_MPS_TRACE_RETURN( 0 );
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}
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int mbedtls_mps_reader_free( mbedtls_mps_reader *rd )
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{
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MBEDTLS_MPS_TRACE_INIT( "mbedtls_mps_reader_free" );
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mps_reader_zero( rd );
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MBEDTLS_MPS_TRACE_RETURN( 0 );
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}
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int mbedtls_mps_reader_feed( mbedtls_mps_reader *rd,
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unsigned char *new_frag,
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mbedtls_mps_size_t new_frag_len )
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{
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mbedtls_mps_size_t copy_to_acc;
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MBEDTLS_MPS_TRACE_INIT( "mbedtls_mps_reader_feed" );
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MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
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"* Fragment length: %u bytes", (unsigned) new_frag_len );
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if( new_frag == NULL )
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MBEDTLS_MPS_TRACE_RETURN( MBEDTLS_ERR_MPS_READER_INVALID_ARG );
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MBEDTLS_MPS_STATE_VALIDATE_RAW( mps_reader_is_producing( rd ),
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"mbedtls_mps_reader_feed() requires reader to be in producing mode" );
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if( mps_reader_is_accumulating( rd ) )
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{
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unsigned char *acc = rd->acc;
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mbedtls_mps_size_t ar = rd->acc_share.acc_remaining;
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mbedtls_mps_size_t aa = rd->acc_avail;
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/* Skip over parts of the accumulator that have already been filled. */
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acc += aa;
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copy_to_acc = ar;
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if( copy_to_acc > new_frag_len )
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copy_to_acc = new_frag_len;
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/* Copy new contents to accumulator. */
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if( copy_to_acc > 0 )
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memcpy( acc, new_frag, copy_to_acc );
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MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
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"Copy new data of size %u of %u into accumulator at offset %u",
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(unsigned) copy_to_acc, (unsigned) new_frag_len, (unsigned) aa );
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/* Check if, with the new fragment, we have enough data. */
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ar -= copy_to_acc;
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if( ar > 0 )
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{
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/* We need to accumulate more data. Stay in producing mode. */
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aa += copy_to_acc;
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rd->acc_share.acc_remaining = ar;
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rd->acc_avail = aa;
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MBEDTLS_MPS_TRACE_RETURN( MBEDTLS_ERR_MPS_READER_NEED_MORE );
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}
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/* We have filled the accumulator: Move to consuming mode. */
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MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
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"Enough data available to serve user request" );
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/* Remember overlap of accumulator and fragment. */
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rd->acc_share.frag_offset = aa;
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aa += copy_to_acc;
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rd->acc_avail = aa;
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}
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else /* Not accumulating */
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{
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rd->acc_share.frag_offset = 0;
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}
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rd->frag = new_frag;
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rd->frag_len = new_frag_len;
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rd->commit = 0;
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rd->end = 0;
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MBEDTLS_MPS_TRACE_RETURN( 0 );
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}
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int mbedtls_mps_reader_get( mbedtls_mps_reader *rd,
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mbedtls_mps_size_t desired,
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unsigned char **buffer,
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mbedtls_mps_size_t *buflen )
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{
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unsigned char *frag;
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mbedtls_mps_size_t fl, fo, end, frag_fetched, frag_remaining;
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MBEDTLS_MPS_TRACE_INIT( "mbedtls_mps_reader_get" );
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MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
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"* Bytes requested: %u", (unsigned) desired );
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MBEDTLS_MPS_STATE_VALIDATE_RAW( mps_reader_is_consuming( rd ),
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"mbedtls_mps_reader_get() requires reader to be in consuming mode" );
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end = rd->end;
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fo = mps_reader_get_fragment_offset( rd );
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/* Check if we're still serving from the accumulator. */
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if( mps_reader_serving_from_accumulator( rd ) )
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{
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unsigned char *acc;
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MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
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"Serve the request from the accumulator" );
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if( fo - end < desired )
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{
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/* Illustration of supported and unsupported cases:
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*
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* - Allowed #1
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*
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* +-----------------------------------+
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* | frag |
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* +-----------------------------------+
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*
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* end end+desired
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* | |
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* +-----v-------v-------------+
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* | acc |
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* +---------------------------+
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* | |
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* fo/frag_offset aa/acc_avail
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*
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* - Allowed #2
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*
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* +-----------------------------------+
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* | frag |
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* +-----------------------------------+
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*
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* end end+desired
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* | |
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* +----------v----------------v
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* | acc |
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* +---------------------------+
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* | |
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* fo/frag_offset aa/acc_avail
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*
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* - Not allowed #1 (could be served, but we don't actually use it):
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*
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* +-----------------------------------+
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* | frag |
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* +-----------------------------------+
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*
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* end end+desired
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* | |
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* +------v-------------v------+
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* | acc |
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* +---------------------------+
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* | |
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* fo/frag_offset aa/acc_avail
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*
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*
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* - Not allowed #2 (can't be served with a contiguous buffer):
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*
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* +-----------------------------------+
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* | frag |
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* +-----------------------------------+
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*
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* end end + desired
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* | |
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* +------v--------------------+ v
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* | acc |
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* +---------------------------+
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* | |
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* fo/frag_offset aa/acc_avail
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*
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* In case of Allowed #1 and #2 we're switching to serve from
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* `frag` starting from the next call to mbedtls_mps_reader_get().
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*/
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mbedtls_mps_size_t aa;
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aa = rd->acc_avail;
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if( aa - end != desired )
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{
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/* It might be possible to serve some of these situations by
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* making additional space in the accumulator, removing those
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* parts that have already been committed.
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* On the other hand, this brings additional complexity and
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* enlarges the code size, while there doesn't seem to be a use
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* case where we don't attempt exactly the same `get` calls when
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* resuming on a reader than what we tried before pausing it.
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* If we believe we adhere to this restricted usage throughout
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* the library, this check is a good opportunity to
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* validate this. */
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MBEDTLS_MPS_TRACE_RETURN(
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MBEDTLS_ERR_MPS_READER_INCONSISTENT_REQUESTS );
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}
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}
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acc = rd->acc;
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acc += end;
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*buffer = acc;
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if( buflen != NULL )
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*buflen = desired;
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end += desired;
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rd->end = end;
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rd->pending = 0;
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MBEDTLS_MPS_TRACE_RETURN( 0 );
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}
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/* Attempt to serve the request from the current fragment */
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MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
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"Serve the request from the current fragment." );
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fl = rd->frag_len;
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frag_fetched = end - fo; /* The amount of data from the current fragment
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* that has already been passed to the user. */
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frag_remaining = fl - frag_fetched; /* Remaining data in fragment */
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/* Check if we can serve the read request from the fragment. */
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if( frag_remaining < desired )
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{
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MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
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"There's not enough data in the current fragment "
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"to serve the request." );
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/* There's not enough data in the current fragment,
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* so either just RETURN what we have or fail. */
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if( buflen == NULL )
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{
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if( frag_remaining > 0 )
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{
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rd->pending = desired - frag_remaining;
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MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
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"Remember to collect %u bytes before re-opening",
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(unsigned) rd->pending );
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}
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MBEDTLS_MPS_TRACE_RETURN( MBEDTLS_ERR_MPS_READER_OUT_OF_DATA );
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}
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desired = frag_remaining;
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}
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/* There's enough data in the current fragment to serve the
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* (potentially modified) read request. */
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frag = rd->frag;
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frag += frag_fetched;
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*buffer = frag;
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if( buflen != NULL )
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*buflen = desired;
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end += desired;
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rd->end = end;
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rd->pending = 0;
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MBEDTLS_MPS_TRACE_RETURN( 0 );
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}
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int mbedtls_mps_reader_commit( mbedtls_mps_reader *rd )
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{
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mbedtls_mps_size_t end;
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MBEDTLS_MPS_TRACE_INIT( "mbedtls_mps_reader_commit" );
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MBEDTLS_MPS_STATE_VALIDATE_RAW( mps_reader_is_consuming( rd ),
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"mbedtls_mps_reader_commit() requires reader to be in consuming mode" );
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end = rd->end;
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rd->commit = end;
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MBEDTLS_MPS_TRACE_RETURN( 0 );
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}
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int mbedtls_mps_reader_reclaim( mbedtls_mps_reader *rd,
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mbedtls_mps_size_t *paused )
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{
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unsigned char *frag, *acc;
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mbedtls_mps_size_t pending, commit;
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mbedtls_mps_size_t al, fo, fl;
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MBEDTLS_MPS_TRACE_INIT( "mbedtls_mps_reader_reclaim" );
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if( paused != NULL )
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*paused = 0;
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MBEDTLS_MPS_STATE_VALIDATE_RAW( mps_reader_is_consuming( rd ),
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"mbedtls_mps_reader_reclaim() requires reader to be in consuming mode" );
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frag = rd->frag;
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acc = rd->acc;
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pending = rd->pending;
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commit = rd->commit;
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fl = rd->frag_len;
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fo = mps_reader_get_fragment_offset( rd );
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if( pending == 0 )
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{
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MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
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"No unsatisfied read-request has been logged." );
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/* Check if there's data left to be consumed. */
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if( commit < fo || commit - fo < fl )
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{
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MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
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"There is data left to be consumed." );
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rd->end = commit;
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MBEDTLS_MPS_TRACE_RETURN( MBEDTLS_ERR_MPS_READER_DATA_LEFT );
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}
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rd->acc_avail = 0;
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rd->acc_share.acc_remaining = 0;
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MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
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"Fragment has been fully processed and committed." );
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}
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else
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{
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int overflow;
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mbedtls_mps_size_t acc_backup_offset;
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mbedtls_mps_size_t acc_backup_len;
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mbedtls_mps_size_t frag_backup_offset;
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mbedtls_mps_size_t frag_backup_len;
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mbedtls_mps_size_t backup_len;
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mbedtls_mps_size_t acc_len_needed;
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MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
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"There has been an unsatisfied read with %u bytes overhead.",
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(unsigned) pending );
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if( acc == NULL )
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{
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MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
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"No accumulator present" );
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MBEDTLS_MPS_TRACE_RETURN(
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MBEDTLS_ERR_MPS_READER_NEED_ACCUMULATOR );
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}
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al = rd->acc_len;
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/* Check if the upper layer has already fetched
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* and committed the contents of the accumulator. */
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if( commit < fo )
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{
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/* No, accumulator is still being processed. */
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frag_backup_offset = 0;
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frag_backup_len = fl;
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acc_backup_offset = commit;
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acc_backup_len = fo - commit;
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}
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else
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{
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/* Yes, the accumulator is already processed. */
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frag_backup_offset = commit - fo;
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frag_backup_len = fl - frag_backup_offset;
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acc_backup_offset = 0;
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acc_backup_len = 0;
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}
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backup_len = acc_backup_len + frag_backup_len;
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acc_len_needed = backup_len + pending;
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overflow = 0;
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overflow |= ( backup_len < acc_backup_len );
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overflow |= ( acc_len_needed < backup_len );
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if( overflow || al < acc_len_needed )
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{
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/* Except for the different return code, we behave as if
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* there hadn't been a call to mbedtls_mps_reader_get()
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* since the last commit. */
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rd->end = commit;
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rd->pending = 0;
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MBEDTLS_MPS_TRACE( mbedtls_mps_trace_error,
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"The accumulator is too small to handle the backup." );
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MBEDTLS_MPS_TRACE( mbedtls_mps_trace_error,
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"* Size: %u", (unsigned) al );
|
|
MBEDTLS_MPS_TRACE( mbedtls_mps_trace_error,
|
|
"* Needed: %u (%u + %u)",
|
|
(unsigned) acc_len_needed,
|
|
(unsigned) backup_len, (unsigned) pending );
|
|
MBEDTLS_MPS_TRACE_RETURN(
|
|
MBEDTLS_ERR_MPS_READER_ACCUMULATOR_TOO_SMALL );
|
|
}
|
|
|
|
MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
|
|
"Fragment backup: %u", (unsigned) frag_backup_len );
|
|
MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
|
|
"Accumulator backup: %u", (unsigned) acc_backup_len );
|
|
|
|
/* Move uncommitted parts from the accumulator to the front
|
|
* of the accumulator. */
|
|
memmove( acc, acc + acc_backup_offset, acc_backup_len );
|
|
|
|
/* Copy uncmmitted parts of the current fragment to the
|
|
* accumulator. */
|
|
memcpy( acc + acc_backup_len,
|
|
frag + frag_backup_offset, frag_backup_len );
|
|
|
|
rd->acc_avail = 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;
|
|
|
|
MBEDTLS_MPS_TRACE( mbedtls_mps_trace_comment,
|
|
"Final state: aa %u, al %u, ar %u",
|
|
(unsigned) rd->acc_avail, (unsigned) rd->acc_len,
|
|
(unsigned) rd->acc_share.acc_remaining );
|
|
MBEDTLS_MPS_TRACE_RETURN( 0 );
|
|
}
|