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gbe_fork/mbedtls/mps_reader.c
otavepto 92c77cee31 added a new cryptography library Mbed TLS
2023-12-24 14:33:40 +02:00

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/*
* 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 */
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