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Hi. I'm a college student and my school has a packeteer which really slows down the bandwidth. I was wondering about ways to get around such a device if its even possible. (tried googling, but not much) I was wondering if it would be possible to exploit ipv4 fragmenting. By that I mean a way around simple state-less firewalls is to send a small small IP packet with a simple TCP header (which has an allowed pori like 80 or something) that has the more fragments flag set. Then send another IP packet with the real TCP port you want to go to, and under the fragmentation offset have it so it will rewrite the TCP header. This way the firewall has no idea what its going to do and passes the packet. Then at the reassembly buffer the computer will reassamble the packet and pass it up its stack and it will go to the banned port. Or course you have to have the same IP ID number and so on. My idea is that something along this line could be used against a packeteer.
Lets say you send out a very small packet to the server you want to connect to that the packeteer allows, such as as HTTP get request with the more fragments flag set. Then send out a packet to overwrite the dest port and have the more fragments flag set. Then send out another packet with the data you want to send to the server and have the fragmentation offset set to overwrite the data in the tcp part. This way when they get to the server they are reassambled and passed up the stack. Now this way can fail if the packeteer dosent allow fragmentation. It can also fail if the packeteer has a special way it handles fragments such as a little bandwidth. Or it can fail if it is such a smart device that it reassembles packets and really sees whats going on. Now, what I described above will only get data out at a fast rate (this would be usefull for a server type thing). Now if you wanted to get data in well you would have to make sure the server sending you stuff did some sort of fragmentation inorder to get by the packeteer. So by telling the server to send lots of fragments you could get arousd such a device. Does this seem practical, should I spend more time trying this out or drop the idea?
Lets say you send out a very small packet to the server you want to connect to that the packeteer allows, such as as HTTP get request with the more fragments flag set. Then send out a packet to overwrite the dest port and have the more fragments flag set. Then send out another packet with the data you want to send to the server and have the fragmentation offset set to overwrite the data in the tcp part. This way when they get to the server they are reassambled and passed up the stack. Now this way can fail if the packeteer dosent allow fragmentation. It can also fail if the packeteer has a special way it handles fragments such as a little bandwidth. Or it can fail if it is such a smart device that it reassembles packets and really sees whats going on. Now, what I described above will only get data out at a fast rate (this would be usefull for a server type thing). Now if you wanted to get data in well you would have to make sure the server sending you stuff did some sort of fragmentation inorder to get by the packeteer. So by telling the server to send lots of fragments you could get arousd such a device. Does this seem practical, should I spend more time trying this out or drop the idea?
