server/sender.c: out-of-bounds read when PAD_LENGTH > 0

[pesco]

senderSendPkt mishandles the PAD_LENGTH define if it is not 0. it will malloc a buffer of size (len + 2 * PAD_LENGTH) and memcpy (len + PAD_LENGTH) bytes from the packet, i.e. PAD_LENGTH bytes from behind the buffer. it will then send (len + 2 * PAD_LENGTH) bytes to the network, i.e. the extra data from behind the packet and PAD_LENGTH uninitialized bytes from the malloced ppacket.