Re: [leafnode-list] Question regarding authentification

["David Given" <dg@xxxxxxxxxxxxx>]

[...]
>I had a look. The problem (for me :-) is that checkpassword insists on
>reading the username and password from fd3, and I have (due to a lack
>of Unix programming knowledge) no idea how to send data from a parent
>process to fd3 of a child process. I assume that it has to do something
>with pipes, but sifting through Stevens so far was not very helpful.
>
>I assume that it must go somewhat like this (this is pseudo code):

Hey! Something I know!

The call you want is dup2(from, to). This duplicates the `from' fd into the 
`to' fd.

It's usually used like this:

{
	int pipefd[2];
	
	// Create a pipe

	pipe(pipefd);

	if (fork() == 0)
	{
		// Inside child. We want to connect one end of the pipe to
		// the child's stdout.

		close(1);		// Don't want old stdout
		dup(pipefd[1], 1);

		// Call remote process

		execlp(...);

		// Paranoia rules

		exit(42);
	}

	// Now we can read from pipefd[0], and we'll get the child's stdout.
}

Connecting a pipe to fd 3 is identical (just change the close() and dup() 
lines). And, of course, you can use multiple pipes.

>I assume that it wouldn't be a major fuss to include checkpassword into
>the leafnode distribution because it is free. I could still check with
>Dan Bernstein first, just to be sure. Of course configure.in would have
>to be tweaked so that an already existing checkpassword would not be
>overwritten.

Aren't there already yp services for doing this?


-- 
+- David Given ---------------McQ-+ 
|  Work: dg@xxxxxxxxxxxxx         | Resist the resistance!                    
|  Play: dgiven@xxxxxxxxx         | 
+- http://wired.st-and.ac.uk/~dg -+ 


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