fix: harden small core containers

hash.c

@@ -25,7 +25,7 @@ hmapalloc(int nbuckets)
 	int nsz;
 
 	if(nbuckets < 1)
-		die("hmapalloc: no buckets");
+		return nil;
 	nsz = Tagsize;
 	store = emalloc(sizeof(*h) + nbuckets * nsz);
 	h = store;
@@ -54,6 +54,8 @@ hmapget(Hmap *h, Str *key)
 	Hnode *n;
 	uchar *v;
 
+	if(h == nil || key == nil || key->n < 0 || key->n > Maxrunes)
+		return nil;
 	v = h->nodes + (hash(key) % h->nbs) * h->nsz;
 	for(;;){
 		n = (Hnode*)v;
@@ -67,7 +69,7 @@ hmapget(Hmap *h, Str *key)
 }
 
 static char*
-sdup(Str *s)
+sdup(Str *s, int *len)
 {
 	char buf[Maxutf];
 	char *p;
@@ -77,6 +79,7 @@ sdup(Str *s)
 	p = emalloc(n + 1);
 	memmove(p, buf, n);
 	p[n] = '\0';
+	*len = n;
 	return p;
 }
 
@@ -121,6 +124,10 @@ hmapset(Hmap **store, Str *key, const char *val, int vlen)
 	int next;
 	vlong diff;
 
+	if(store == nil || *store == nil || key == nil ||
+	   key->n < 0 || key->n > Maxrunes || vlen < 0 ||
+	   (vlen > 0 && val == nil))
+		return;
 	newval = memdup(val, vlen);
 	h = *store;
 	v = h->nodes + (hash(key) % h->nbs) * h->nsz;
@@ -151,8 +158,7 @@ hmapset(Hmap **store, Str *key, const char *val, int vlen)
 	n = (Hnode*)v;
 replace:
 	if(n->filled == 0){
-		n->key = sdup(key);
-		n->klen = strlen(n->key);
+		n->key = sdup(key, &n->klen);
 		n->filled = 1;
 	}
 	n->next = next;