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Factor out warn_early_consensus()

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Factor out the early consensus warning code from
networkstatus_set_current_consensus() into a new function
warn_early_consensus().
This commit is contained in:
Taylor Yu 2018-05-01 18:13:37 -05:00
parent 4921670a8c
commit 0b80a0e500
2 changed files with 45 additions and 19 deletions
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62
src/or/networkstatus.c
View File

@ -1751,6 +1751,48 @@ handle_missing_protocol_warning(const networkstatus_t *c,
handle_missing_protocol_warning_impl(c, 1);
}
/**
* Check whether we received a consensus that appears to be coming
* from the future. Because we implicitly trust the directory
* authorities' idea of the current time, we produce a warning if we
* get an early consensus.
*
* If we got a consensus that is time stamped far in the past, that
* could simply have come from a stale cache. Possible ways to get a
* consensus from the future can include:
*
* - enough directory authorities have wrong clocks
* - directory authorities collude to produce misleading time stamps
* - our own clock is wrong (this is by far the most likely)
*
* We neglect highly improbable scenarios that involve actual time
* travel.
*/
STATIC void
warn_early_consensus(const networkstatus_t *c, const char *flavor,
time_t now)
{
/** If a consensus appears more than this many seconds before its declared
* valid-after time, declare that our clock is skewed. */
#define EARLY_CONSENSUS_NOTICE_SKEW 60
if (now < c->valid_after - EARLY_CONSENSUS_NOTICE_SKEW) {
char tbuf[ISO_TIME_LEN+1];
char dbuf[64];
long delta = now - c->valid_after;
char *flavormsg = NULL;
format_iso_time(tbuf, c->valid_after);
format_time_interval(dbuf, sizeof(dbuf), delta);
log_warn(LD_GENERAL, "Our clock is %s behind the time published in the "
"consensus network status document (%s UTC). Tor needs an "
"accurate clock to work correctly. Please check your time and "
"date settings!", dbuf, tbuf);
tor_asprintf(&flavormsg, "%s flavor consensus", flavor);
clock_skew_warning(NULL, delta, 1, LD_GENERAL, flavormsg, "CONSENSUS");
tor_free(flavormsg);
}
}
/** Try to replace the current cached v3 networkstatus with the one in
* <b>consensus</b>. If we don't have enough certificates to validate it,
* store it in consensus_waiting_for_certs and launch a certificate fetch.
@ -2053,25 +2095,7 @@ networkstatus_set_current_consensus(const char *consensus,
write_str_to_file(consensus_fname, consensus, 0);
}
/** If a consensus appears more than this many seconds before its declared
* valid-after time, declare that our clock is skewed. */
#define EARLY_CONSENSUS_NOTICE_SKEW 60
if (now < c->valid_after - EARLY_CONSENSUS_NOTICE_SKEW) {
char tbuf[ISO_TIME_LEN+1];
char dbuf[64];
long delta = now - c->valid_after;
char *flavormsg = NULL;
format_iso_time(tbuf, c->valid_after);
format_time_interval(dbuf, sizeof(dbuf), delta);
log_warn(LD_GENERAL, "Our clock is %s behind the time published in the "
"consensus network status document (%s UTC). Tor needs an "
"accurate clock to work correctly. Please check your time and "
"date settings!", dbuf, tbuf);
tor_asprintf(&flavormsg, "%s flavor consensus", flavor);
clock_skew_warning(NULL, delta, 1, LD_GENERAL, flavormsg, "CONSENSUS");
tor_free(flavormsg);
}
warn_early_consensus(c, flavor, now);
/* We got a new consesus. Reset our md fetch fail cache */
microdesc_reset_outdated_dirservers_list();

2
src/or/networkstatus.h
View File

@ -153,6 +153,8 @@ int any_client_port_set(const or_options_t *options);
#ifdef TOR_UNIT_TESTS
STATIC int networkstatus_set_current_consensus_from_ns(networkstatus_t *c,
const char *flavor);
STATIC void warn_early_consensus(const networkstatus_t *c, const char *flavor,
time_t now);
extern networkstatus_t *current_ns_consensus;
extern networkstatus_t *current_md_consensus;
#endif /* defined(TOR_UNIT_TESTS) */