[tor-commits] [tor/master] Add crypto_rand_int_range() and use it
nickm at torproject.org
nickm at torproject.org
Thu Apr 23 13:21:49 UTC 2015
commit 3f413184728c1d7b441b8e54585c43220665218c
Author: David Goulet <dgoulet at ev0ke.net>
Date: Tue Apr 21 10:17:12 2015 -0400
Add crypto_rand_int_range() and use it
Incidently, this fixes a bug where the maximum value was never used when
only using crypto_rand_int(). For instance this example below in
rendservice.c never gets to INTRO_POINT_LIFETIME_MAX_SECONDS.
int intro_point_lifetime_seconds =
INTRO_POINT_LIFETIME_MIN_SECONDS +
crypto_rand_int(INTRO_POINT_LIFETIME_MAX_SECONDS -
INTRO_POINT_LIFETIME_MIN_SECONDS);
Signed-off-by: David Goulet <dgoulet at ev0ke.net>
---
src/common/crypto.c | 21 ++++++++++++++++++++-
src/common/crypto.h | 1 +
src/common/tortls.c | 3 ++-
src/or/entrynodes.c | 6 ++++--
src/or/main.c | 2 +-
src/or/rendservice.c | 10 ++++------
src/or/router.c | 4 +++-
7 files changed, 35 insertions(+), 12 deletions(-)
diff --git a/src/common/crypto.c b/src/common/crypto.c
index f05be2e..1c4eda9 100644
--- a/src/common/crypto.c
+++ b/src/common/crypto.c
@@ -2317,6 +2317,25 @@ crypto_rand_int(unsigned int max)
}
}
+/** Return a pseudorandom integer, chosen uniformly from the values between
+ * <b>min</b> and <b>max</b> inclusive.
+ *
+ * <b>min</b> MUST be between 0 and <b>max</b> - 1.
+ * <b>max</b> MUST be bigger than <b>min</b> and <= to INT_MAX.
+ */
+int
+crypto_rand_int_range(unsigned int min, unsigned int max)
+{
+ tor_assert(min <= max);
+ tor_assert(max <= INT_MAX);
+
+ /* The overflow is avoided here because crypto_rand_int() returns a value
+ * between 0 and (max - min - 1) with max being <= INT_MAX and min <= max.
+ * This is why we add 1 to the maximum value so we can actually get max as
+ * a return value. */
+ return min + crypto_rand_int(max - min + 1);
+}
+
/** Return a pseudorandom 64-bit integer, chosen uniformly from the values
* between 0 and <b>max</b>-1. */
uint64_t
@@ -2379,7 +2398,7 @@ crypto_random_hostname(int min_rand_len, int max_rand_len, const char *prefix,
if (min_rand_len > max_rand_len)
min_rand_len = max_rand_len;
- randlen = min_rand_len + crypto_rand_int(max_rand_len - min_rand_len + 1);
+ randlen = crypto_rand_int_range(min_rand_len, max_rand_len);
prefixlen = strlen(prefix);
resultlen = prefixlen + strlen(suffix) + randlen + 16;
diff --git a/src/common/crypto.h b/src/common/crypto.h
index b9c26a4..3de3c7e 100644
--- a/src/common/crypto.h
+++ b/src/common/crypto.h
@@ -254,6 +254,7 @@ int crypto_seed_rng(int startup);
MOCK_DECL(int,crypto_rand,(char *to, size_t n));
int crypto_strongest_rand(uint8_t *out, size_t out_len);
int crypto_rand_int(unsigned int max);
+int crypto_rand_int_range(unsigned int min, unsigned int max);
uint64_t crypto_rand_uint64(uint64_t max);
double crypto_rand_double(void);
struct tor_weak_rng_t;
diff --git a/src/common/tortls.c b/src/common/tortls.c
index 32106eb..7809c1a 100644
--- a/src/common/tortls.c
+++ b/src/common/tortls.c
@@ -659,7 +659,8 @@ tor_tls_create_certificate(crypto_pk_t *rsa,
* than having it start right now. Don't choose quite uniformly, since
* then we might pick a time where we're about to expire. Lastly, be
* sure to start on a day boundary. */
- start_time = time(NULL) - crypto_rand_int(cert_lifetime) + 2*24*3600;
+ time_t now = time(NULL);
+ start_time = crypto_rand_int_range(now - cert_lifetime, now) + 2*24*3600;
start_time -= start_time % (24*3600);
tor_assert(rsa);
diff --git a/src/or/entrynodes.c b/src/or/entrynodes.c
index 9663f34..9f07d5a 100644
--- a/src/or/entrynodes.c
+++ b/src/or/entrynodes.c
@@ -440,7 +440,8 @@ 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);
+ time_t now = time(NULL);
+ entry->chosen_on_date = crypto_rand_int_range(now - 3600*24*30, now);
entry->chosen_by_version = tor_strdup(VERSION);
/* Are we picking this guard because all of our current guards are
@@ -1439,8 +1440,9 @@ entry_guards_parse_state(or_state_t *state, int set, char **msg)
}
} else {
if (state_version) {
+ time_t now = time(NULL);
+ e->chosen_on_date = crypto_rand_int_range(now - 3600*24*30, now);
e->chosen_by_version = tor_strdup(state_version);
- e->chosen_on_date = time(NULL) - crypto_rand_int(3600*24*30);
}
}
if (e->path_bias_disabled && !e->bad_since)
diff --git a/src/or/main.c b/src/or/main.c
index 39c0f5c..b9009db 100644
--- a/src/or/main.c
+++ b/src/or/main.c
@@ -1623,7 +1623,7 @@ run_scheduled_events(time_t now)
time_to.check_for_correct_dns < now &&
! router_my_exit_policy_is_reject_star()) {
if (!time_to.check_for_correct_dns) {
- time_to.check_for_correct_dns = now + 60 + crypto_rand_int(120);
+ time_to.check_for_correct_dns = crypto_rand_int_range(now, now + 120) + 60;
} else {
dns_launch_correctness_checks();
time_to.check_for_correct_dns = now + 12*3600 +
diff --git a/src/or/rendservice.c b/src/or/rendservice.c
index cf0352c..4b2331f 100644
--- a/src/or/rendservice.c
+++ b/src/or/rendservice.c
@@ -3133,9 +3133,8 @@ intro_point_should_expire_now(rend_intro_point_t *intro,
/* This intro point has been published, but we haven't picked an
* expiration time for it. Pick one now. */
int intro_point_lifetime_seconds =
- INTRO_POINT_LIFETIME_MIN_SECONDS +
- crypto_rand_int(INTRO_POINT_LIFETIME_MAX_SECONDS -
- INTRO_POINT_LIFETIME_MIN_SECONDS);
+ crypto_rand_int_range(INTRO_POINT_LIFETIME_MIN_SECONDS,
+ INTRO_POINT_LIFETIME_MAX_SECONDS);
/* Start the expiration timer now, rather than when the intro
* point was first published. There shouldn't be much of a time
@@ -3337,9 +3336,8 @@ rend_services_introduce(void)
intro->time_to_expire = -1;
intro->time_expiring = -1;
intro->max_introductions =
- INTRO_POINT_MIN_LIFETIME_INTRODUCTIONS +
- crypto_rand_int(INTRO_POINT_MAX_LIFETIME_INTRODUCTIONS -
- INTRO_POINT_MIN_LIFETIME_INTRODUCTIONS);
+ crypto_rand_int_range(INTRO_POINT_MIN_LIFETIME_INTRODUCTIONS,
+ INTRO_POINT_MAX_LIFETIME_INTRODUCTIONS);
smartlist_add(service->intro_nodes, intro);
log_info(LD_REND, "Picked router %s as an intro point for %s.",
safe_str_client(node_describe(node)),
diff --git a/src/or/router.c b/src/or/router.c
index b8bfd3c..afe533f 100644
--- a/src/or/router.c
+++ b/src/or/router.c
@@ -683,7 +683,9 @@ router_initialize_tls_context(void)
if (!lifetime) { /* we should guess a good ssl cert lifetime */
/* choose between 5 and 365 days, and round to the day */
- lifetime = 5*24*3600 + crypto_rand_int(361*24*3600);
+ unsigned int five_days = 5*24*3600;
+ unsigned int one_year = 365*24*3600;
+ lifetime = crypto_rand_int_range(five_days, one_year);
lifetime -= lifetime % (24*3600);
if (crypto_rand_int(2)) {
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