[linux-security] Re: /bin/login problem

[R E Wolff BitWizard nl (Rogier Wolff)]

Wietse Venema wrote:
> Rogier Wolff:
> > Passing the string through a pipe works (I didn't find that "obvious":
> > The sending end of the pipe was written to by the same process, which
> > just exec-ed the reading program, and the writing end of the pipe is
> > closed by the time the read is performed)
> 
> It seems much simpler to me to select the terminal for readability
> (i.e. until someone hits the ENTER key) and to notify the login
> program that it can find the name on STDIN instead of finding it
> on the command line.
> 
> The TTYPROMPT environment variable used by SYSV4 does not pass
> sensitive info via the environment; it is just a flag to notify
> the login program that the login name is available on STDIN. All
> this requires minimal change to the login progam: a getenv() call
> and setting a flag to force reading STDIN upon program startup.
> 
> Yes, this means that you lose all those cutesy features of my agetty
> program. But login/getty code runs as root and is extremely security
> sensitive. Keep it simple, I'd say.
> 
> 	Wietse
> 

One of the classical "getty" features that you loose this way is 
the autobauding that classical getty's perform. (i.e. read a
character, and change the baudrate whenever it's "bad")

				Roger. 

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