As requested, the skinny on my tip-without-ops approach.

doc/tipwithoutops.txt

+; crb, june 5 2002
+
+Tip-without-ops:
+
+Joe User has downloaded and installed "tiptunnel," telling it his favorite telnet client
+and associating it with files of type "text/testbed-acl" in his web browser.
+There is a Windows binary (and a FreeBSD binary?), as well as unix/windows source,
+available for download, with adequate disclaimers all over it.
+
+Joe User logs into his experiment, and opens up a "detail view" on a node
+assigned to his experiment. A link on the page offers "Connect to serial line."
+When he clicks on the link, the server sends a file of MIME type "text/testbed-acl".
+This launches tiptunnel on his machine. The file contains a server name, a port number,
+a key, and a certificate's SHA-hash.
+
+Tiptunnel connects, via TCP/IP, to the server/port specified in the ACL file.
+It is now talking to Capture. Capture, upon accepting a TCP/IP connection, 
+wants a secret key before it allows a client access to the serial line. 
+Tiptunnel sends "WANTSSL" as the secret key, and both initialize an OpenSSL
+connection. Capture uses $TB/etc/capture.pem as its certificate, unless a different
+certificate was specified on its command line.
+
+Tiptunnel looks at the certificate given by Capture, and SHA-hashes it, verifying that
+it matches the hash in the ACL file. If it does not, the user is warned of a possible
+man-in-the-middle attack, and tiptunnel closes. If the hash does indeed match,
+the key is sent over SSL. If the key is accepted by Capture, the connection begins.
+
+Tiptunnel then forks.
+
+The parent starts listening on a local port for a TCP/IP connection. A single 
+connection (from localhost only) will be accepted, and traffic to/from that port
+will be tunnelled through the SSL connection. Upon accepting a connection,
+special telnet commands will be sent to the client, turning off line-at-a-time and
+local echo.
+When the connection closes, this process will exit.
+
+The child execs the telnet program chosen by the user,
+telling it to connect to localhost:<someport> (the tiptunnel).
+Joe User is now able to talk to his node's serial line.
+When Joe User exits, the connection is dropped, and all processes exit.
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