lib: resolves potential reads of uninitialized data

lib/util.c

@@ -274,8 +274,9 @@ ykpiv_rc ykpiv_util_list_keys(ykpiv_state *state, uint8_t *key_count, ykpiv_key
 
   for (i = 0; i < sizeof(SLOTS); i++) {
     cbBuf = sizeof(buf);
+    res = _read_certificate(state, SLOTS[i], buf, &cbBuf);
 
-    if (YKPIV_OK == (res = _read_certificate(state, SLOTS[i], buf, &cbBuf))) {
+    if ((res == YKPIV_OK) && (cbBuf > 0)) {
       // add current slot to result, grow result buffer if necessary
 
       cbRealloc = (sizeof(ykpiv_key) + cbBuf - 1) > (cbData - offset) ? MAX((sizeof(ykpiv_key) + cbBuf - 1) - (cbData - offset), CB_PAGE) : 0;

lib/ykpiv.c

@@ -1044,6 +1044,12 @@ static ykpiv_rc _ykpiv_get_version(ykpiv_state *state, ykpiv_version_t *p_versio
   if((res = _send_data(state, &apdu, data, &recv_len, &sw)) != YKPIV_OK) {
     return res;
   } else if(sw == SW_SUCCESS) {
+
+    /* check that we received enough data for the verson number */
+    if (recv_len < 3) {
+      return YKPIV_SIZE_ERROR;
+    }
+
     state->ver.major = data[0];
     state->ver.minor = data[1];
     state->ver.patch = data[2];
@@ -1182,6 +1188,11 @@ static ykpiv_rc _ykpiv_get_serial(ykpiv_state *state, uint32_t *p_serial, bool f
     }
   }
 
+  /* check that we received enough data for the serial number */
+  if (recv_len < 4) {
+    return YKPIV_SIZE_ERROR;
+  }
+
   p_temp = (uint8_t*)(&state->serial);
 
   *p_temp++ = data[3];