kwz_between: fix a bug when one key is a prefix of another

diff --git a/lib/cache.c b/lib/cache.c
index 965c26854fb9691471ce94572516cda5b09f79b3..d4b68353be697c0b335cdcbc4c1fe5ed07ec9195 100644 (file)
--- a/lib/cache.c
+++ b/lib/cache.c
@@ -622,11 +622,18 @@ static knot_db_val_t key_NSEC1(struct key *k, const knot_dname_t *name,
 static bool kwz_between(knot_db_val_t k1, knot_db_val_t k2, knot_db_val_t k3)
 {
        assert(k2.data && k3.data);
-       /* CACHE_KEY_DEF */
-       return (!k1.data || memcmp(k1.data, k2.data, MIN(k1.len, k2.len)) < 0)
-               && (k3.len == 0 /* wrap-around */
-                       || memcmp(k2.data, k3.data, MIN(k2.len, k3.len)) < 0
-                  );
+       /* CACHE_KEY_DEF; we need to beware of one key being a prefix of another */
+       if (k1.data) {
+               int cmp12 = memcmp(k1.data, k2.data, MIN(k1.len, k2.len));
+               bool ok = cmp12 < 0 || (cmp12 == 0 && k1.len < k2.len);
+               if (!ok) return false;
+       }
+       if (k3.len == 0) { /* wrap-around */
+               return k2.len > 0;
+       } else {
+               int cmp23 = memcmp(k2.data, k3.data, MIN(k2.len, k3.len));
+               return cmp23 < 0 || (cmp23 == 0 && k2.len < k3.len);
+       }
 }
 
 /** NSEC1 range search.