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Network Security Hacks by Andrew Lockhart

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Share Files Securely in Unix

Use SFS to help secure your remote filesystems.

If you are using Unix systems and sharing files on your network, you are most likely using NFS. However, there are a lot of security problems, not only with individual implementations, but also with the design of the protocol itself. For instance, if a user can spoof an IP address and mount an NFS share that is only meant for a certain computer, she essentially has root access to all the files on that share. In addition, NFS employs secret file handles that are used with each file request. Since NFS does not encrypt its traffic, this makes it very easy for attackers to guess these file handles. If they guess correctly, they essentially get total root access to the remote filesystem.

SFS (http://www.fs.net), the Self-certifying File System, fixes all of these problems by employing a drastically different design philosophy. NFS was created with the notion that you can (and should) trust your network. SFS has been designed from the beginning with the idea that no network should ever be trusted until it can definitively prove its identity. To accomplish this, SFS makes use of public keys on both the client and server ends. It uses these keys to verify the identity of servers and clients, and also provides access control on the server side. One particularly nice side effect of such strong encryption is that SFS provides a much finer grained level of access control than NFS. With NFS, you are limited to specifying ...

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