acme-client calloc fix

[Ted Unangst]

should not size the size until the allocation succeeds, or the free path will
try to deref the null array.


Index: json.c
===================================================================
RCS file: /home/cvs/src/usr.sbin/acme-client/json.c,v
retrieving revision 1.14
diff -u -p -r1.14 json.c
--- json.c      18 Jun 2019 18:50:07 -0000      1.14
+++ json.c      22 Jan 2020 05:37:59 -0000
@@ -459,12 +459,13 @@ json_parse_order(struct jsmnn *n, struct
        if ((array = json_getarray(n, "authorizations")) == NULL)
                goto err;
 
-       if ((order->authsz = array->fields) > 0) {
+       if (array->fields > 0) {
                order->auths = calloc(sizeof(*order->auths), order->authsz);
                if (order->auths == NULL) {
                        warn("malloc");
                        goto err;
                }
+               order->authsz = array->fields;
        }
 
        for (i = 0; i < array->fields; i++) {