KTFTP: a secure file transfer utility

What KTFTP is

KTFTP is a CMU-grown simple file transfer utility for transferring secure data between server machines. It is based on the 4.3 BSD tftp, and inherits all of its functionality. This document will only detail differences between ktftp and regular tftp.

Summary of Differences

KTFTP does not work on a file basis; rather, operations are done on tags, which are mapped by the KTFTP server to a file on the remote machine. This is done for data abstraction purposes, and so that knowledge of the motion of log files and related types of data on the remote machine does not have to be propagated excessively throughout other system components. Each tag has associated with it a '~' holder which is referenced as tagname~ (for instance, the tag "foo" would have ~ holder "foo~"). See the push and delete commands below for the use of this. The mental picture is that of a backup file.
Additionally, all tags have access control lists associated with them. The Kerberos identity of the user running ktftp is used for these. Unlike normal tftp, if a user is on an ACL for a tag, the only time an operation will be denied is if root on the server machine cannot reasonably perform the operation. In particular, read/write bits on the file are irrelavent and file existance is not neccesary for the put operation. The ~ holder has exactly the same rights as the normal tag.
Two new commands are avaliable in KTFTP, and are in place explicitly to support moving log files and similar types of data off of server machines. These are:

push: moves the files in the named tags to their ~ holder. This is done atomically through a rename(2) on the remote server
delete: deletes the file associated with the named tags

These commands can be put together as follows for reliable transfer of data:

ktftp push machine:tag

      ktftp get machine:tag~

      ktftp delete machine:tag~

As this implies, a single command can be placed on the command line for non-interactive operation. Exit codes can be used to detect errors:

-1: a local error, error message printed
0: successful operation
1: EUNDEF, associated with a UNIX error on the remote machine, error message printed.
2: ENOTFOUND, file associated with tag not found
3: EACCESS, access violation
4: ENOSPACE, disk full or allocation exceeded
5: EBADOP, illegal KTFTP operation
6: EBADID, unknown transfer ID
7: EEXISTS, file already exists
8: ENOUSER, no such user
9: ETIMEOUT, transfer timed out

EBADID, EEXISTS and ENOUSER are not currently used in KTFTP. EBADOP is indicative of packet corruption or catastrophic program error.
So that ktftp may be used as a pipe, the local filename "-" may be used to stand for standard input / standard output.
Lastly, so KTFTP can be used for security purposes, all data being transferred is encrypted.
Program Author
Dan Lovinger, CMU Computing Services
Support Contact
Derrick Brashear (shadow+@andrew.cmu.edu), CMU Computing Services

Obtaining KTFTP

Export of this software from the United States of America may require a specific license from the United States Government.

The KTFTP distribution