diff options
| -rw-r--r-- | changes/ticket8240 | 4 | ||||
| -rw-r--r-- | doc/tor.1.txt | 6 | ||||
| -rw-r--r-- | src/common/util.h | 11 | ||||
| -rw-r--r-- | src/or/circuitbuild.c | 36 | ||||
| -rw-r--r-- | src/or/config.c | 1 | ||||
| -rw-r--r-- | src/or/or.h | 3 |
6 files changed, 57 insertions, 4 deletions
diff --git a/changes/ticket8240 b/changes/ticket8240 new file mode 100644 index 0000000000..91e6f8c14a --- /dev/null +++ b/changes/ticket8240 @@ -0,0 +1,4 @@ + o Major security fixes: + - Make the default guard lifetime controllable via a new + GuardLifetime torrc option and a GuardLifetime consensus + parameter. Start of a fix for bug 8240; bugfix on 0.1.1.11-alpha. diff --git a/doc/tor.1.txt b/doc/tor.1.txt index 773fccf536..5cf5a718c0 100644 --- a/doc/tor.1.txt +++ b/doc/tor.1.txt @@ -959,6 +959,12 @@ The following options are useful only for clients (that is, if If UseEntryGuards is set to 1, we will try to pick a total of NUM routers as long-term entries for our circuits. (Default: 3) +**HeartbeatPeriod** __N__ **days**|**weeks**|**months**:: + If nonzero, and UseEntryGuards is set, minimum time to keep a guard before + picking a new one. If zero, we use the GuardLifetime parameter from the + consensus directory. No value here may be less than 2 months or greater + than 5 years; out-of-range values are clamped. (Default: 0) + **SafeSocks** **0**|**1**:: When this option is enabled, Tor will reject application connections that use unsafe variants of the socks protocol -- ones that only provide an IP diff --git a/src/common/util.h b/src/common/util.h index 8977d273c5..4642e40584 100644 --- a/src/common/util.h +++ b/src/common/util.h @@ -173,6 +173,17 @@ int n_bits_set_u8(uint8_t v); * overflow. */ #define CEIL_DIV(a,b) (((a)+(b)-1)/(b)) +/* Return <b>v</b> if it's between <b>min</b> and <b>max</b>. Otherwise + * return <b>min</b> if <b>v</b> is smaller than <b>min</b>, or <b>max</b> if + * <b>b</b> is larger than <b>max</b>. + * + * Requires that <b>min</b> is no more than <b>max</b>. May evaluate any of + * its arguments more than once! */ +#define CLAMP(min,v,max) \ + ( ((v) < (min)) ? (min) : \ + ((v) > (max)) ? (max) : \ + (v) ) + /* String manipulation */ /** Allowable characters in a hexadecimal string. */ diff --git a/src/or/circuitbuild.c b/src/or/circuitbuild.c index f8521c5cff..f07d428829 100644 --- a/src/or/circuitbuild.c +++ b/src/or/circuitbuild.c @@ -4203,6 +4203,9 @@ control_event_guard_deferred(void) #endif } +/** Largest amount that we'll backdate chosen_on_date */ +#define CHOSEN_ON_DATE_SLOP (30*86400) + /** Add a new (preferably stable and fast) router to our * entry_guards list. Return a pointer to the router if we succeed, * or NULL if we can't find any more suitable entries. @@ -4241,7 +4244,7 @@ add_an_entry_guard(const node_t *chosen, int reset_status, int prepend) * don't all select them on the same day, and b) avoid leaving a * precise timestamp in the state file about when we first picked * this guard. For details, see the Jan 2010 or-dev thread. */ - entry->chosen_on_date = time(NULL) - crypto_rand_int(3600*24*30); + entry->chosen_on_date = time(NULL) - crypto_rand_int(CHOSEN_ON_DATE_SLOP); entry->chosen_by_version = tor_strdup(VERSION); if (prepend) smartlist_insert(entry_guards, 0, entry); @@ -4285,15 +4288,40 @@ entry_guard_free(entry_guard_t *e) tor_free(e); } +/** + * Return the minimum lifetime of working entry guard, in seconds, + * as given in the consensus networkstatus. + */ +static int32_t +guards_get_lifetime(void) +{ + const or_options_t *options = get_options(); +#define DFLT_GUARD_LIFETIME (86400 * 60) /* Two months. */ +#define MIN_GUARD_LIFETIME (86400 * 60) /* Two months. */ +#define MAX_GUARD_LIFETIME (86400 * 1826) /* Five years. */ + + if (options->GuardLifetime >= 1) { + return CLAMP(MIN_GUARD_LIFETIME, + options->GuardLifetime, + MAX_GUARD_LIFETIME) + CHOSEN_ON_DATE_SLOP; + } + + return networkstatus_get_param(NULL, "GuardLifetime", + DFLT_GUARD_LIFETIME, + MIN_GUARD_LIFETIME, + MAX_GUARD_LIFETIME) + CHOSEN_ON_DATE_SLOP; +} + /** Remove any entry guard which was selected by an unknown version of Tor, * or which was selected by a version of Tor that's known to select - * entry guards badly, or which was selected more 2 months ago. */ + * entry guards badly, or which was selected a long time ago */ /* XXXX The "obsolete guards" and "chosen long ago guards" things should * probably be different functions. */ static int remove_obsolete_entry_guards(time_t now) { int changed = 0, i; + int32_t guard_lifetime = guards_get_lifetime(); for (i = 0; i < smartlist_len(entry_guards); ++i) { entry_guard_t *entry = smartlist_get(entry_guards, i); @@ -4324,8 +4352,8 @@ remove_obsolete_entry_guards(time_t now) } tor_free(tor_ver); } - if (!version_is_bad && entry->chosen_on_date + 3600*24*60 < now) { - /* It's been 2 months since the date listed in our state file. */ + if (!version_is_bad && entry->chosen_on_date + guard_lifetime < now) { + /* It's been too long since the date listed in our state file. */ msg = "was selected several months ago"; date_is_bad = 1; } diff --git a/src/or/config.c b/src/or/config.c index 90a5dfbda1..6ccd65a57a 100644 --- a/src/or/config.c +++ b/src/or/config.c @@ -302,6 +302,7 @@ static config_var_t _option_vars[] = { #endif OBSOLETE("GiveGuardFlagTo_CVE_2011_2768_VulnerableRelays"), OBSOLETE("Group"), + V(GuardLifetime, INTERVAL, "0 minutes"), V(HardwareAccel, BOOL, "0"), V(HeartbeatPeriod, INTERVAL, "6 hours"), V(AccelName, STRING, NULL), diff --git a/src/or/or.h b/src/or/or.h index 51c23d305d..b54834de32 100644 --- a/src/or/or.h +++ b/src/or/or.h @@ -3605,6 +3605,9 @@ typedef struct { int PathBiasScaleFactor; /** @} */ + /** How long (seconds) do we keep a guard before picking a new one? */ + int GuardLifetime; + } or_options_t; /** Persistent state for an onion router, as saved to disk. */ |