# Exercise #8a.

Your exercise if you choose this option is to construct ssh like client/server
programs.

The client:
- Should accept a host and optionally a port # from the command line.
  i.e.: Usage: `sclient <host> [<port#>]`

- Should connect to the server using a streaming internet socket.  All
  communication with the server should be "encrypted" using a simple stream
  cipher using the `rand_r()` or better the `lrand48_r()` PRNG's.  The port
  number may be used as the secret key to the PRNG.

- Your client should set the local terminal settings as per the `pty.c` example
  done in class.

- Your client may handle the login/authorization phase and send the username and
  password to the server on connecting.  Note however that typed passwords
  should not be visible.

The server:
- Should start a "shell" (this should probably be a fake shell) via a pseudo
  terminal (the shell may or may not be started automatically on server startup
  -- it will award one bonus point if the shell is not started until someone has
  successfully connected and authenticated and the user is prompted to press
  enter to start the shell.)

- However once launched the shell should remain running even if the client
  closes the connection.  If the shell exits, then the client(s) may be prompted
  to press enter to launch a new shell.

- Optionally should allow multiple incoming streaming internet client
  connections that are individually encrypted using the secret key via a PRNG.
  It may however be designed to fork off a process to handle a single connection
  if you so desire.

- When a initial connection is made the server should enter into an
  authorization phase with the new client, first prompting for a user-name, then
  password and check the credentials against a user-name/password database file
  "`./auth.db`" (that is located in the current working directory of the server.)

- The `auth.db` file should in the following format:
  >
```
user-name1:hashed-password1
user-name2:hashed-password2
...
```

  The server should allow for more than one user-name and password. Note that
  the client will not echo keys typed, so for the user-name entry you must echo
  back the keys typed and not echo back keys typed for the password entry phase.