static buffer and error checking for DNSSEC status

CID: 1094066

src/knot/ctl/remote.c

@@ -222,12 +222,18 @@ static int remote_c_status(server_t *s, remote_cmdargs_t* a)
 	return KNOT_EOK;
 }
 
-static char *dnssec_info(const zonedata_t *zd, char *buf)
+static char *dnssec_info(const zonedata_t *zd, char *buf, size_t buf_size)
 {
 	assert(zd && zd->dnssec_timer);
+	assert(buf);
+
 	time_t diff_time = zd->dnssec_timer->tv.tv_sec;
 	struct tm *t = localtime(&diff_time);
-	snprintf(buf, 128, "%s", asctime(t));
+
+	int written = snprintf(buf, buf_size, "%s", asctime(t));
+	UNUSED(written);
+	assert(written >= 0);
+
 	return buf;
 }
 
@@ -301,8 +307,8 @@ static int remote_c_zonestatus(server_t *s, remote_cmdargs_t* a)
 		}
 
 		/* Workaround, some platforms ignore 'size' with snprintf() */
-		char buf[512];
-		char *dnssec_buf = xmalloc(128);
+		char buf[512] = { '\0' };
+		char dnssec_buf[128] = { '\0' };
 		int n = snprintf(buf, sizeof(buf),
 		                 "%s\ttype=%s | serial=%u | %s %s | %s %s\n",
 		                 zd->conf->name,
@@ -311,9 +317,8 @@ static int remote_c_zonestatus(server_t *s, remote_cmdargs_t* a)
 		                 state ? state : "",
 		                 when ? when : "",
 		                 zd->conf->dnssec_enable ? "automatic DNSSEC, resigning at:" : "",
-		                 zd->conf->dnssec_enable ? dnssec_info(zd, dnssec_buf) : "");
+		                 zd->conf->dnssec_enable ? dnssec_info(zd, dnssec_buf, sizeof(dnssec_buf)) : "");
 		free(when);
-		free(dnssec_buf);
 		if (n < 0 || (size_t)n > rb) {
 			*dst = '\0';
 			ret = KNOT_ESPACE;