lib:crypto: Add error checking to GKDI key start time calculation

[gd/samba-autobuild/.git] / lib / crypto / gkdi.c

diff --git a/lib/crypto/gkdi.c b/lib/crypto/gkdi.c
index 92348f286ac303cdd9f5e095734cb9d1507d4f4c..dcecf1206b99c4c55350d7867b57cbb621b45d2b 100644 (file)
--- a/lib/crypto/gkdi.c
+++ b/lib/crypto/gkdi.c
@@ -175,11 +175,45 @@ struct Gkid gkdi_get_interval_id(const NTTIME time)
                    time / gkdi_key_cycle_duration % gkdi_l2_key_iteration);
 }
 
-NTTIME gkdi_get_key_start_time(const struct Gkid gkid)
+bool gkdi_get_key_start_time(const struct Gkid gkid, NTTIME *start_time_out)
 {
-       return (gkid.l0_idx * gkdi_l1_key_iteration * gkdi_l2_key_iteration +
-               gkid.l1_idx * gkdi_l2_key_iteration + gkid.l2_idx) *
-              gkdi_key_cycle_duration;
+       if (!gkid_is_valid(gkid)) {
+               return false;
+       }
+
+       {
+               enum GkidType key_type = gkid_key_type(gkid);
+               if (key_type != GKID_L2_SEED_KEY) {
+                       return false;
+               }
+       }
+
+       {
+               /*
+                * Make sure that the GKID is not so large its start time can’t
+                * be represented in NTTIME.
+                */
+               static const struct Gkid max_gkid = {
+                       UINT64_MAX /
+                               (gkdi_l1_key_iteration * gkdi_l2_key_iteration *
+                                gkdi_key_cycle_duration),
+                       UINT64_MAX /
+                               (gkdi_l2_key_iteration *
+                                gkdi_key_cycle_duration) %
+                               gkdi_l1_key_iteration,
+                       UINT64_MAX / gkdi_key_cycle_duration %
+                               gkdi_l2_key_iteration};
+               if (!gkid_less_than_or_equal_to(gkid, max_gkid)) {
+                       return false;
+               }
+       }
+
+       *start_time_out = ((uint64_t)gkid.l0_idx * gkdi_l1_key_iteration *
+                                  gkdi_l2_key_iteration +
+                          (uint64_t)gkid.l1_idx * gkdi_l2_key_iteration +
+                          (uint64_t)gkid.l2_idx) *
+                         gkdi_key_cycle_duration;
+       return true;
 }
 
 /*