diff options
Diffstat (limited to 'library/mps_reader.c')
| -rw-r--r-- | library/mps_reader.c | 538 |
1 files changed, 538 insertions, 0 deletions
diff --git a/library/mps_reader.c b/library/mps_reader.c new file mode 100644 index 00000000000..27d0c04c108 --- /dev/null +++ b/library/mps_reader.c @@ -0,0 +1,538 @@ +/* + * Message Processing Stack, Reader implementation + * + * Copyright The Mbed TLS Contributors + * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later + */ + +#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 */ |