Is it possible to abuse icmp?

I wonder what's going to happen when malicious user will inject crafted icmp packet with some error information (like Port Unreachable) to tcp connection. Will the connection be closed? You may think that to inject something like this it's needed to guess sequential numbers. That's not exactly correct. Icmp payload can be relatively small, specification says it has to carry at least 8 bytes from OSI 3th layer, so only tcp source and destination port must be included.

I can assume that you're going to use google. To block your connection I have to only send 65K packets with payload: from google, to you, from 80port to, and sequentially select your local port. I should guess after while. That's even less than 65K possibilities, on standard linux there are less than 32K possible local ports (see proc parameter ip_local_port_range).

The question is how common tcp stacks are interpreting such crafted Icmp message.

There are also other possibly vulnerable applications. For example most dns servers, to make recursive queries use source port 53 (see bind 'query-source address' option). How dns servers react for icmp errors with relatively small payload? Is it possible to perform Dos attack using this method?

Well, of course port number in tcp header uses only 16 bits. So to 8 bytes in icmp payload should fit: source, destination port, seq number.

I change my question. How common tcp stacks interpret icmp packets with too short payload?

Linux seems to be immune for this kind of attack. The function that parses icmp errors for tcp transmission is in linux/net/tcp_ipv4.c:tcp_v4_err(). The code says, that payload must be at least 8 bytes long. Source and destination port in the payload must be correct and sequence number must be in correct range. In other case icmp packet is simply dropped.

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