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Ignore timestamps of INTRODUCE2 cells

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This commit is contained in:
Robert Ransom 2011-10-30 02:13:46 -07:00
parent 1a52a947c5
commit 272dd90b5c
3 changed files with 15 additions and 14 deletions
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11
changes/bug3460 Normal file
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@ -0,0 +1,11 @@
o Major bugfixes:
- Ignore the timestamps of INTRODUCE2 cells received by a hidden
service. Previously, hidden services would check that the
timestamp was within 30 minutes of their system clock, so that
services could keep only INTRODUCE2 cells they had received in
the last hour in their replay-detection cache. Bugfix on
0.2.1.6-alpha, when the v3 intro-point protocol (the first one
which sent a timestamp field in the INTRODUCE2 cell) was
introduced; fixes bug 3460.

6
src/or/or.h
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@ -756,9 +756,9 @@ typedef struct rend_data_t {
char rend_cookie[REND_COOKIE_LEN];
} rend_data_t;
/** Time interval for tracking possible replays of INTRODUCE2 cells.
* Incoming cells with timestamps half of this interval in the past or
* future are dropped immediately. */
/** Time interval for tracking replays of DH public keys received in
* INTRODUCE2 cells. Used only to avoid launching multiple
* simultaneous attempts to connect to the same rendezvous point. */
#define REND_REPLAY_TIME_INTERVAL (60 * 60)
/** Used to indicate which way a cell is going on a circuit. */

12
src/or/rendservice.c
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@ -1037,7 +1037,6 @@ rend_service_introduce(origin_circuit_t *circuit, const uint8_t *request,
len = r;
if (*buf == 3) {
/* Version 3 INTRODUCE2 cell. */
time_t ts = 0;
v3_shift = 1;
auth_type = buf[1];
switch (auth_type) {
@ -1059,17 +1058,8 @@ rend_service_introduce(origin_circuit_t *circuit, const uint8_t *request,
log_info(LD_REND, "Unknown authorization type '%d'", auth_type);
}
/* Check timestamp. */
ts = ntohl(get_uint32(buf+1+v3_shift));
/* Skip the timestamp field. We no longer use it. */
v3_shift += 4;
if ((now - ts) < -1 * REND_REPLAY_TIME_INTERVAL / 2 ||
(now - ts) > REND_REPLAY_TIME_INTERVAL / 2) {
/* This is far more likely to mean that a client's clock is
* skewed than that a replay attack is in progress. */
log_info(LD_REND, "INTRODUCE2 cell is too %s. Discarding.",
(now - ts) < 0 ? "old" : "new");
return -1;
}
}
if (*buf == 2 || *buf == 3) {
/* Version 2 INTRODUCE2 cell. */