diff options
Diffstat (limited to 'library/mps_reader.c')
| -rw-r--r-- | library/mps_reader.c | 559 |
1 files changed, 559 insertions, 0 deletions
diff --git a/library/mps_reader.c b/library/mps_reader.c new file mode 100644 index 000000000..df97b6cd1 --- /dev/null +++ b/library/mps_reader.c @@ -0,0 +1,559 @@ +/* + * 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 "common.h" + +#if defined(MBEDTLS_SSL_PROTO_TLS1_3) + +#include "mps_reader.h" +#include "mps_common.h" +#include "mps_trace.h" + +#include <string.h> + +#if defined(MBEDTLS_MPS_ENABLE_TRACE) +static int mbedtls_mps_trace_id = MBEDTLS_MPS_TRACE_BIT_READER; +#endif /* MBEDTLS_MPS_ENABLE_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. + * + * The reason for this is twofold: + * (1) It will ease verification efforts using the VST + * (Verified Software Toolchain) + * 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 int mps_reader_is_accumulating( + mbedtls_mps_reader const *rd ) +{ + mbedtls_mps_size_t acc_remaining; + if( rd->acc == NULL ) + return( 0 ); + + acc_remaining = rd->acc_share.acc_remaining; + return( acc_remaining > 0 ); +} + +static inline int mps_reader_is_producing( + mbedtls_mps_reader const *rd ) +{ + unsigned char *frag = rd->frag; + return( frag == NULL ); +} + +static inline int mps_reader_is_consuming( + mbedtls_mps_reader const *rd ) +{ + return( !mps_reader_is_producing( rd ) ); +} + +static inline mbedtls_mps_size_t mps_reader_get_fragment_offset( + mbedtls_mps_reader const *rd ) +{ + unsigned char *acc = rd->acc; + mbedtls_mps_size_t frag_offset; + + if( acc == NULL ) + return( 0 ); + + frag_offset = rd->acc_share.frag_offset; + return( frag_offset ); +} + +static inline mbedtls_mps_size_t mps_reader_serving_from_accumulator( + mbedtls_mps_reader const *rd ) +{ + mbedtls_mps_size_t frag_offset, end; + + frag_offset = mps_reader_get_fragment_offset( rd ); + end = rd->end; + + return( end < frag_offset ); +} + +static inline void mps_reader_zero( mbedtls_mps_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 FV efforts since it + * doesn't require reasoning about structs being + * interpreted as unstructured binary blobs. */ + static mbedtls_mps_reader const zero = + { .frag = NULL, + .frag_len = 0, + .commit = 0, + .end = 0, + .pending = 0, + .acc = NULL, + .acc_len = 0, + .acc_available = 0, + .acc_share = { .acc_remaining = 0 } + }; + *rd = zero; +} + +int mbedtls_mps_reader_init( mbedtls_mps_reader *rd, + unsigned char *acc, + mbedtls_mps_size_t acc_len ) +{ + MBEDTLS_MPS_TRACE_INIT( "mbedtls_mps_reader_init" ); + MBEDTLS_MPS_TRACE( MBEDTLS_MPS_TRACE_TYPE_COMMENT, + "* Accumulator size: %u bytes", (unsigned) acc_len ); + mps_reader_zero( rd ); + rd->acc = acc; + rd->acc_len = acc_len; + MBEDTLS_MPS_TRACE_RETURN( 0 ); +} + +int mbedtls_mps_reader_free( mbedtls_mps_reader *rd ) +{ + MBEDTLS_MPS_TRACE_INIT( "mbedtls_mps_reader_free" ); + mps_reader_zero( rd ); + MBEDTLS_MPS_TRACE_RETURN( 0 ); +} + +int mbedtls_mps_reader_feed( mbedtls_mps_reader *rd, + unsigned char *new_frag, + mbedtls_mps_size_t new_frag_len ) +{ + mbedtls_mps_size_t copy_to_acc; + MBEDTLS_MPS_TRACE_INIT( "mbedtls_mps_reader_feed" ); + MBEDTLS_MPS_TRACE( MBEDTLS_MPS_TRACE_TYPE_COMMENT, + "* Fragment length: %u bytes", (unsigned) new_frag_len ); + + if( new_frag == NULL ) + MBEDTLS_MPS_TRACE_RETURN( MBEDTLS_ERR_MPS_READER_INVALID_ARG ); + + MBEDTLS_MPS_STATE_VALIDATE_RAW( mps_reader_is_producing( rd ), + "mbedtls_mps_reader_feed() requires reader to be in producing mode" ); + + if( mps_reader_is_accumulating( rd ) ) + { + unsigned char *acc = rd->acc; + mbedtls_mps_size_t acc_remaining = rd->acc_share.acc_remaining; + mbedtls_mps_size_t acc_available = rd->acc_available; + + /* Skip over parts of the accumulator that have already been filled. */ + acc += acc_available; + + copy_to_acc = acc_remaining; + if( copy_to_acc > new_frag_len ) + copy_to_acc = new_frag_len; + + /* Copy new contents to accumulator. */ + memcpy( acc, new_frag, copy_to_acc ); + + MBEDTLS_MPS_TRACE( MBEDTLS_MPS_TRACE_TYPE_COMMENT, + "Copy new data of size %u of %u into accumulator at offset %u", + (unsigned) copy_to_acc, (unsigned) new_frag_len, (unsigned) acc_available ); + + /* Check if, with the new fragment, we have enough data. */ + acc_remaining -= copy_to_acc; + if( acc_remaining > 0 ) + { + /* We need to accumulate more data. Stay in producing mode. */ + acc_available += copy_to_acc; + rd->acc_share.acc_remaining = acc_remaining; + rd->acc_available = acc_available; + MBEDTLS_MPS_TRACE_RETURN( MBEDTLS_ERR_MPS_READER_NEED_MORE ); + } + + /* We have filled the accumulator: Move to consuming mode. */ + + MBEDTLS_MPS_TRACE( MBEDTLS_MPS_TRACE_TYPE_COMMENT, + "Enough data available to serve user request" ); + + /* Remember overlap of accumulator and fragment. */ + rd->acc_share.frag_offset = acc_available; + acc_available += copy_to_acc; + rd->acc_available = acc_available; + } + else /* Not accumulating */ + { + rd->acc_share.frag_offset = 0; + } + + rd->frag = new_frag; + rd->frag_len = new_frag_len; + rd->commit = 0; + rd->end = 0; + MBEDTLS_MPS_TRACE_RETURN( 0 ); +} + + +int mbedtls_mps_reader_get( mbedtls_mps_reader *rd, + mbedtls_mps_size_t desired, + unsigned char **buffer, + mbedtls_mps_size_t *buflen ) +{ + unsigned char *frag; + mbedtls_mps_size_t frag_len, frag_offset, end, frag_fetched, frag_remaining; + MBEDTLS_MPS_TRACE_INIT( "mbedtls_mps_reader_get" ); + MBEDTLS_MPS_TRACE( MBEDTLS_MPS_TRACE_TYPE_COMMENT, + "* Bytes requested: %u", (unsigned) desired ); + + MBEDTLS_MPS_STATE_VALIDATE_RAW( mps_reader_is_consuming( rd ), + "mbedtls_mps_reader_get() requires reader to be in consuming mode" ); + + end = rd->end; + frag_offset = mps_reader_get_fragment_offset( rd ); + + /* Check if we're still serving from the accumulator. */ + if( mps_reader_serving_from_accumulator( rd ) ) + { + /* Illustration of supported and unsupported cases: + * + * - Allowed #1 + * + * +-----------------------------------+ + * | frag | + * +-----------------------------------+ + * + * end end+desired + * | | + * +-----v-------v-------------+ + * | acc | + * +---------------------------+ + * | | + * frag_offset acc_available + * + * - Allowed #2 + * + * +-----------------------------------+ + * | frag | + * +-----------------------------------+ + * + * end end+desired + * | | + * +----------v----------------v + * | acc | + * +---------------------------+ + * | | + * frag_offset acc_available + * + * - Not allowed #1 (could be served, but we don't actually use it): + * + * +-----------------------------------+ + * | frag | + * +-----------------------------------+ + * + * end end+desired + * | | + * +------v-------------v------+ + * | acc | + * +---------------------------+ + * | | + * frag_offset acc_available + * + * + * - Not allowed #2 (can't be served with a contiguous buffer): + * + * +-----------------------------------+ + * | frag | + * +-----------------------------------+ + * + * end end + desired + * | | + * +------v--------------------+ v + * | acc | + * +---------------------------+ + * | | + * frag_offset acc_available + * + * In case of Allowed #2 we're switching to serve from + * `frag` starting from the next call to mbedtls_mps_reader_get(). + */ + + unsigned char *acc; + + MBEDTLS_MPS_TRACE( MBEDTLS_MPS_TRACE_TYPE_COMMENT, + "Serve the request from the accumulator" ); + if( frag_offset - end < desired ) + { + mbedtls_mps_size_t acc_available; + acc_available = rd->acc_available; + if( acc_available - 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. */ + MBEDTLS_MPS_TRACE_RETURN( + MBEDTLS_ERR_MPS_READER_INCONSISTENT_REQUESTS ); + } + } + + acc = rd->acc; + acc += end; + + *buffer = acc; + if( buflen != NULL ) + *buflen = desired; + + end += desired; + rd->end = end; + rd->pending = 0; + + MBEDTLS_MPS_TRACE_RETURN( 0 ); + } + + /* Attempt to serve the request from the current fragment */ + MBEDTLS_MPS_TRACE( MBEDTLS_MPS_TRACE_TYPE_COMMENT, + "Serve the request from the current fragment." ); + + frag_len = rd->frag_len; + frag_fetched = end - frag_offset; /* The amount of data from the current + * fragment that has already been passed + * to the user. */ + frag_remaining = frag_len - frag_fetched; /* Remaining data in fragment */ + + /* Check if we can serve the read request from the fragment. */ + if( frag_remaining < desired ) + { + MBEDTLS_MPS_TRACE( MBEDTLS_MPS_TRACE_TYPE_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; + MBEDTLS_MPS_TRACE( MBEDTLS_MPS_TRACE_TYPE_COMMENT, + "Remember to collect %u bytes before re-opening", + (unsigned) rd->pending ); + } + MBEDTLS_MPS_TRACE_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. */ + + frag = rd->frag; + frag += frag_fetched; + + *buffer = frag; + if( buflen != NULL ) + *buflen = desired; + + end += desired; + rd->end = end; + rd->pending = 0; + MBEDTLS_MPS_TRACE_RETURN( 0 ); +} + +int mbedtls_mps_reader_commit( mbedtls_mps_reader *rd ) +{ + mbedtls_mps_size_t end; + MBEDTLS_MPS_TRACE_INIT( "mbedtls_mps_reader_commit" ); + MBEDTLS_MPS_STATE_VALIDATE_RAW( mps_reader_is_consuming( rd ), + "mbedtls_mps_reader_commit() requires reader to be in consuming mode" ); + + end = rd->end; + rd->commit = end; + + MBEDTLS_MPS_TRACE_RETURN( 0 ); +} + +int mbedtls_mps_reader_reclaim( mbedtls_mps_reader *rd, + int *paused ) +{ + unsigned char *frag, *acc; + mbedtls_mps_size_t pending, commit; + mbedtls_mps_size_t acc_len, frag_offset, frag_len; + MBEDTLS_MPS_TRACE_INIT( "mbedtls_mps_reader_reclaim" ); + + if( paused != NULL ) + *paused = 0; + + MBEDTLS_MPS_STATE_VALIDATE_RAW( mps_reader_is_consuming( rd ), + "mbedtls_mps_reader_reclaim() requires reader to be in consuming mode" ); + + frag = rd->frag; + acc = rd->acc; + pending = rd->pending; + commit = rd->commit; + frag_len = rd->frag_len; + + frag_offset = mps_reader_get_fragment_offset( rd ); + + if( pending == 0 ) + { + MBEDTLS_MPS_TRACE( MBEDTLS_MPS_TRACE_TYPE_COMMENT, + "No unsatisfied read-request has been logged." ); + + /* Check if there's data left to be consumed. */ + if( commit < frag_offset || commit - frag_offset < frag_len ) + { + MBEDTLS_MPS_TRACE( MBEDTLS_MPS_TRACE_TYPE_COMMENT, + "There is data left to be consumed." ); + rd->end = commit; + MBEDTLS_MPS_TRACE_RETURN( MBEDTLS_ERR_MPS_READER_DATA_LEFT ); + } + + rd->acc_available = 0; + rd->acc_share.acc_remaining = 0; + + MBEDTLS_MPS_TRACE( MBEDTLS_MPS_TRACE_TYPE_COMMENT, + "Fragment has been fully processed and committed." ); + } + else + { + int overflow; + + mbedtls_mps_size_t acc_backup_offset; + mbedtls_mps_size_t acc_backup_len; + mbedtls_mps_size_t frag_backup_offset; + mbedtls_mps_size_t frag_backup_len; + + mbedtls_mps_size_t backup_len; + mbedtls_mps_size_t acc_len_needed; + + MBEDTLS_MPS_TRACE( MBEDTLS_MPS_TRACE_TYPE_COMMENT, + "There has been an unsatisfied read with %u bytes overhead.", + (unsigned) pending ); + + if( acc == NULL ) + { + MBEDTLS_MPS_TRACE( MBEDTLS_MPS_TRACE_TYPE_COMMENT, + "No accumulator present" ); + MBEDTLS_MPS_TRACE_RETURN( + MBEDTLS_ERR_MPS_READER_NEED_ACCUMULATOR ); + } + acc_len = rd->acc_len; + + /* Check if the upper layer has already fetched + * and committed the contents of the accumulator. */ + if( commit < frag_offset ) + { + /* No, accumulator is still being processed. */ + frag_backup_offset = 0; + frag_backup_len = frag_len; + acc_backup_offset = commit; + acc_backup_len = frag_offset - commit; + } + else + { + /* Yes, the accumulator is already processed. */ + frag_backup_offset = commit - frag_offset; + frag_backup_len = frag_len - frag_backup_offset; + acc_backup_offset = 0; + acc_backup_len = 0; + } + + backup_len = acc_backup_len + frag_backup_len; + acc_len_needed = backup_len + pending; + + overflow = 0; + overflow |= ( backup_len < acc_backup_len ); + overflow |= ( acc_len_needed < backup_len ); + + if( overflow || acc_len < acc_len_needed ) + { + /* Except for the different return code, we behave as if + * there hadn't been a call to mbedtls_mps_reader_get() + * since the last commit. */ + rd->end = commit; + rd->pending = 0; + MBEDTLS_MPS_TRACE( MBEDTLS_MPS_TRACE_TYPE_ERROR, + "The accumulator is too small to handle the backup." ); + MBEDTLS_MPS_TRACE( MBEDTLS_MPS_TRACE_TYPE_ERROR, + "* Size: %u", (unsigned) acc_len ); + MBEDTLS_MPS_TRACE( MBEDTLS_MPS_TRACE_TYPE_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_TYPE_COMMENT, + "Fragment backup: %u", (unsigned) frag_backup_len ); + MBEDTLS_MPS_TRACE( MBEDTLS_MPS_TRACE_TYPE_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 uncommitted parts of the current fragment to the + * accumulator. */ + memcpy( acc + acc_backup_len, + frag + frag_backup_offset, frag_backup_len ); + + rd->acc_available = 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_TYPE_COMMENT, + "Final state: aa %u, al %u, ar %u", + (unsigned) rd->acc_available, (unsigned) rd->acc_len, + (unsigned) rd->acc_share.acc_remaining ); + MBEDTLS_MPS_TRACE_RETURN( 0 ); +} + +#endif /* MBEDTLS_SSL_PROTO_TLS1_3 */ |