Harden packet, retry, and alert handling

src/Packet.cpp

@@ -64,22 +64,29 @@ uint8_t Packet::writeTo(uint8_t dest[]) const {
 }
 
 bool Packet::readFrom(const uint8_t src[], uint8_t len) {
+  if (src == NULL || len < 2) return false;   // header + path_len
+
   uint8_t i = 0;
   tx_cr = 0;
   header = src[i++];
+  if (getPayloadVer() > PAYLOAD_VER_1) return false;
+
   if (hasTransportCodes()) {
+    if ((uint16_t)i + sizeof(transport_codes) + 1 > len) return false;
     memcpy(&transport_codes[0], &src[i], 2); i += 2;
     memcpy(&transport_codes[1], &src[i], 2); i += 2;
   } else {
     transport_codes[0] = transport_codes[1] = 0;
   }
+
+  if (i >= len) return false;
   path_len = src[i++];
   if (!isValidPathLen(path_len)) return false;   // bad encoding
 
   uint8_t bl = getPathByteLen();
+  if ((uint16_t)i + bl > len) return false;
   memcpy(path, &src[i], bl); i += bl;
 
-  if (i >= len) return false;   // bad encoding
   payload_len = len - i;
   if (payload_len > sizeof(payload)) return false;  // bad encoding
   memcpy(payload, &src[i], payload_len); //i += payload_len;