From 5802408ab53a524f40f9a83a104f1d5f19ce5db0 Mon Sep 17 00:00:00 2001
From: Greg Hudson <ghudson@mit.edu>
Date: Thu, 24 Aug 2017 16:00:33 -0400
Subject: [PATCH] Limit ticket lifetime to 2^31-1 seconds
Although timestamps above 2^31-1 are now valid, intervals exceeding
2^31-1 seconds may be treated incorrectly by comparison operations.
The initially computed interval in kdc_get_ticket_endtime() could be
negative if the requested end time is far in the future, causing the
function to yield an incorrect result. (With the new larger value of
kdc_infinity, this could specifically happen if a KDC-REQ contains a
zero till field.) Cap the interval at the maximum valid value.
Reported by Weijun Wang.
Avoid delta comparisons in favor of timestamp comparions in
krb5int_validate_times(), ksu's krb5_check_exp(), and clockskew
checks.
Also use a y2038-safe timestamp comparison in set_request_times() when
comparing the requested renewable end time to the requested ticket end
time.
ticket: 8352
(cherry picked from commit 54e58755368b58ba5894a14c1d02626da42d8003)
---
src/clients/ksu/ccache.c | 2 +-
src/include/k5-int.h | 7 +++++++
src/kdc/kdc_util.c | 7 ++++++-
src/kdc/replay.c | 2 +-
src/kdc/t_replay.c | 2 +-
src/lib/krb5/krb/gc_via_tkt.c | 4 ++--
src/lib/krb5/krb/get_in_tkt.c | 6 +++---
src/lib/krb5/krb/int-proto.h | 3 ---
src/lib/krb5/krb/valid_times.c | 4 ++--
src/lib/krb5/os/timeofday.c | 2 +-
10 files changed, 24 insertions(+), 15 deletions(-)
diff --git a/src/clients/ksu/ccache.c b/src/clients/ksu/ccache.c
index 236313b7b..2a99521d4 100644
--- a/src/clients/ksu/ccache.c
+++ b/src/clients/ksu/ccache.c
@@ -282,7 +282,7 @@ krb5_error_code krb5_check_exp(context, tkt_time)
}
- if (ts_delta(currenttime, tkt_time.endtime) > context->clockskew) {
+ if (ts_after(currenttime, ts_incr(tkt_time.endtime, context->clockskew))) {
retval = KRB5KRB_AP_ERR_TKT_EXPIRED ;
return retval;
}
diff --git a/src/include/k5-int.h b/src/include/k5-int.h
index 39ffb9568..e31004a7c 100644
--- a/src/include/k5-int.h
+++ b/src/include/k5-int.h
@@ -2386,6 +2386,13 @@ ts_after(krb5_timestamp a, krb5_timestamp b)
return (uint32_t)a > (uint32_t)b;
}
+/* Return true if a and b are within d seconds. */
+static inline krb5_boolean
+ts_within(krb5_timestamp a, krb5_timestamp b, krb5_deltat d)
+{
+ return !ts_after(a, ts_incr(b, d)) && !ts_after(b, ts_incr(a, d));
+}
+
krb5_error_code KRB5_CALLCONV
krb5_get_credentials_for_user(krb5_context context, krb5_flags options,
krb5_ccache ccache,
diff --git a/src/kdc/kdc_util.c b/src/kdc/kdc_util.c
index 5455e2a67..770163b94 100644
--- a/src/kdc/kdc_util.c
+++ b/src/kdc/kdc_util.c
@@ -1759,14 +1759,19 @@ kdc_get_ticket_endtime(kdc_realm_t *kdc_active_realm,
krb5_db_entry *server,
krb5_timestamp *out_endtime)
{
- krb5_timestamp until, life;
+ krb5_timestamp until;
+ krb5_deltat life;
if (till == 0)
till = kdc_infinity;
until = ts_min(till, endtime);
+ /* Determine the requested lifetime, capped at the maximum valid time
+ * interval. */
life = ts_delta(until, starttime);
+ if (ts_after(until, starttime) && life < 0)
+ life = INT32_MAX;
if (client != NULL && client->max_life != 0)
life = min(life, client->max_life);
diff --git a/src/kdc/replay.c b/src/kdc/replay.c
index fab39cf88..caca783bf 100644
--- a/src/kdc/replay.c
+++ b/src/kdc/replay.c
@@ -61,7 +61,7 @@ static size_t total_size = 0;
static krb5_ui_4 seed;
#define STALE_TIME (2*60) /* two minutes */
-#define STALE(ptr, now) (labs(ts_delta((ptr)->timein, now)) >= STALE_TIME)
+#define STALE(ptr, now) (ts_after(now, ts_incr((ptr)->timein, STALE_TIME)))
/* Return x rotated to the left by r bits. */
static inline krb5_ui_4
diff --git a/src/kdc/t_replay.c b/src/kdc/t_replay.c
index 1442e0e8c..bb7e2faff 100644
--- a/src/kdc/t_replay.c
+++ b/src/kdc/t_replay.c
@@ -903,7 +903,7 @@ test_kdc_insert_lookaside_cache_expire(void **state)
assert_non_null(e);
e->num_hits = 5;
- time_return(STALE_TIME, 0);
+ time_return(STALE_TIME + 1, 0);
kdc_insert_lookaside(context, &req2, NULL);
assert_null(K5_LIST_FIRST(&hash_table[req_hash1]));
diff --git a/src/lib/krb5/krb/gc_via_tkt.c b/src/lib/krb5/krb/gc_via_tkt.c
index cf1ea361f..5b9bb9573 100644
--- a/src/lib/krb5/krb/gc_via_tkt.c
+++ b/src/lib/krb5/krb/gc_via_tkt.c
@@ -306,8 +306,8 @@ krb5int_process_tgs_reply(krb5_context context,
goto cleanup;
if (!in_cred->times.starttime &&
- !in_clock_skew(context, dec_rep->enc_part2->times.starttime,
- timestamp)) {
+ !ts_within(dec_rep->enc_part2->times.starttime, timestamp,
+ context->clockskew)) {
retval = KRB5_KDCREP_SKEW;
goto cleanup;
}
diff --git a/src/lib/krb5/krb/get_in_tkt.c b/src/lib/krb5/krb/get_in_tkt.c
index 7178bd87b..ed15550f0 100644
--- a/src/lib/krb5/krb/get_in_tkt.c
+++ b/src/lib/krb5/krb/get_in_tkt.c
@@ -269,8 +269,8 @@ verify_as_reply(krb5_context context,
return retval;
} else {
if ((request->from == 0) &&
- !in_clock_skew(context, as_reply->enc_part2->times.starttime,
- time_now))
+ !ts_within(as_reply->enc_part2->times.starttime, time_now,
+ context->clockskew))
return (KRB5_KDCREP_SKEW);
}
return 0;
@@ -781,7 +781,7 @@ set_request_times(krb5_context context, krb5_init_creds_context ctx)
if (ctx->renew_life > 0) {
/* Don't ask for a smaller renewable time than the lifetime. */
ctx->request->rtime = ts_incr(from, ctx->renew_life);
- if (ctx->request->rtime < ctx->request->till)
+ if (ts_after(ctx->request->till, ctx->request->rtime))
ctx->request->rtime = ctx->request->till;
ctx->request->kdc_options &= ~KDC_OPT_RENEWABLE_OK;
} else {
diff --git a/src/lib/krb5/krb/int-proto.h b/src/lib/krb5/krb/int-proto.h
index 48bd9f8f7..9c746d05b 100644
--- a/src/lib/krb5/krb/int-proto.h
+++ b/src/lib/krb5/krb/int-proto.h
@@ -83,9 +83,6 @@ krb5int_construct_matching_creds(krb5_context context, krb5_flags options,
krb5_creds *in_creds, krb5_creds *mcreds,
krb5_flags *fields);
-#define in_clock_skew(context, date, now) \
- (labs(ts_delta(date, now)) < (context)->clockskew)
-
#define IS_TGS_PRINC(p) ((p)->length == 2 && \
data_eq_string((p)->data[0], KRB5_TGS_NAME))
diff --git a/src/lib/krb5/krb/valid_times.c b/src/lib/krb5/krb/valid_times.c
index 9e509b2dd..294761a88 100644
--- a/src/lib/krb5/krb/valid_times.c
+++ b/src/lib/krb5/krb/valid_times.c
@@ -47,10 +47,10 @@ krb5int_validate_times(krb5_context context, krb5_ticket_times *times)
else
starttime = times->authtime;
- if (ts_delta(starttime, currenttime) > context->clockskew)
+ if (ts_after(starttime, ts_incr(currenttime, context->clockskew)))
return KRB5KRB_AP_ERR_TKT_NYV; /* ticket not yet valid */
- if (ts_delta(currenttime, times->endtime) > context->clockskew)
+ if (ts_after(currenttime, ts_incr(times->endtime, context->clockskew)))
return KRB5KRB_AP_ERR_TKT_EXPIRED; /* ticket expired */
return 0;
diff --git a/src/lib/krb5/os/timeofday.c b/src/lib/krb5/os/timeofday.c
index 887f24c22..d4e36b1c7 100644
--- a/src/lib/krb5/os/timeofday.c
+++ b/src/lib/krb5/os/timeofday.c
@@ -60,7 +60,7 @@ krb5_check_clockskew(krb5_context context, krb5_timestamp date)
retval = krb5_timeofday(context, ¤ttime);
if (retval)
return retval;
- if (labs(ts_delta(date, currenttime)) >= context->clockskew)
+ if (!ts_within(date, currenttime, context->clockskew))
return KRB5KRB_AP_ERR_SKEW;
return 0;