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prop289: Move digest matching in its own function

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No behavior change but code had to be refactored a bit. Also, the tor_memcmp()
was changed to tor_memneq().

Part of #26288

Signed-off-by: David Goulet <dgoulet@torproject.org>
This commit is contained in:
David Goulet 2019-03-07 12:01:58 -05:00
parent 217b553193
commit 4efe9d653a
1 changed files with 45 additions and 35 deletions
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80
src/core/or/sendme.c
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@ -59,6 +59,49 @@ get_accept_min_version(void)
SENDME_ACCEPT_MIN_VERSION_MAX); SENDME_ACCEPT_MIN_VERSION_MAX);
} }
/* Return true iff the given cell digest matches the first digest in the
* circuit sendme list. */
static bool
v1_digest_matches(const circuit_t *circ, const uint8_t *cell_digest)
{
bool ret = false;
uint8_t *circ_digest = NULL;
tor_assert(circ);
tor_assert(cell_digest);
/* We shouldn't have received a SENDME if we have no digests. Log at
* protocol warning because it can be tricked by sending many SENDMEs
* without prior data cell. */
if (circ->sendme_last_digests == NULL ||
smartlist_len(circ->sendme_last_digests) == 0) {
log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
"We received a SENDME but we have no cell digests to match. "
"Closing circuit.");
goto no_match;
}
/* Pop the first element that was added (FIFO) and compare it. */
circ_digest = smartlist_get(circ->sendme_last_digests, 0);
smartlist_del_keeporder(circ->sendme_last_digests, 0);
/* Compare the digest with the one in the SENDME. This cell is invalid
* without a perfect match. */
if (tor_memneq(circ_digest, cell_digest, TRUNNEL_SENDME_V1_DIGEST_LEN)) {
log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
"SENDME v1 cell digest do not match.");
goto no_match;
}
/* Digests matches! */
ret = true;
no_match:
/* This digest was popped from the circuit list. Regardless of what happens,
* we have no more use for it. */
tor_free(circ_digest);
return ret;
}
/* Return true iff the given decoded SENDME version 1 cell is valid and /* Return true iff the given decoded SENDME version 1 cell is valid and
* matches the expected digest on the circuit. * matches the expected digest on the circuit.
* *
@ -68,44 +111,11 @@ get_accept_min_version(void)
static bool static bool
cell_v1_is_valid(const sendme_cell_t *cell, const circuit_t *circ) cell_v1_is_valid(const sendme_cell_t *cell, const circuit_t *circ)
{ {
const uint8_t *cell_digest = NULL;
tor_assert(cell); tor_assert(cell);
tor_assert(circ); tor_assert(circ);
cell_digest = sendme_cell_getconstarray_data_v1_digest(cell); const uint8_t *cell_digest = sendme_cell_getconstarray_data_v1_digest(cell);
return v1_digest_matches(circ, cell_digest);
/* We shouldn't have received this SENDME if we have no digests. Log at
* protocol warning because it can be tricked by sending many SENDMEs
* without prior data cell. */
if (circ->sendme_last_digests == NULL ||
smartlist_len(circ->sendme_last_digests) == 0) {
log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
"We received a SENDME but we have no cell digests to match. "
"Closing circuit.");
goto invalid;
}
/* Pop the first element that was added (FIFO) and compare it. */
{
uint8_t *digest = smartlist_get(circ->sendme_last_digests, 0);
smartlist_del_keeporder(circ->sendme_last_digests, 0);
/* Compare the digest with the one in the SENDME. This cell is invalid
* without a perfect match. */
if (tor_memcmp(digest, cell_digest, TRUNNEL_SENDME_V1_DIGEST_LEN)) {
tor_free(digest);
log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
"SENDME v1 cell digest do not match.");
goto invalid;
}
tor_free(digest);
}
/* Validated SENDME v1 cell. */
return 1;
invalid:
return 0;
} }
/* Return true iff the given cell version can be handled or if the minimum /* Return true iff the given cell version can be handled or if the minimum