🚀 go-pugleaf

In article <3536@zorba.Tynan.COM> kingman@tci.bell-atl.com (Matt Kingman) writes:
>Hi.  I have an application that requires the user to enter a password
>on the command line.  In the good old days, I could modify argv in place
>to block out the password, so that when other users did a 'ps' they can't
>see the password.  On System V 3.X, the command line arguments get copied
>to the user struct so that modifying argv doesn't do the trick anymore.
>'ps' looks at the user struct for it's information.  My question is:
>Is there any way to access the user struct from within my program so that
>I can block out the password?  How do I find it?  (Having the program prompt
>the user for the password is an obvious workaround but there must be some
>way to access the user struct).  Thanks for any help/information.

Well, I won't comment on what you're trying to do, although I think you're
approaching the problem the wrong way. However, you could try this if you
insist:
Open /dev/kmem. Seek to UAREA_SYSVMADDR, or whatever it is, which should
be in <sys/user.h>. Read the u area. Fix it and write it.

This has its problems in that it probably won't work. I'm not sure what
will happen on write - all I've ever done is read it. It's also revoltingly
non-portable (try it on VMS :-)

/dev/kmem needs to be 0666, or your code setuid, as well, which have their
own sets of associated problems. 0666 for /dev/kmem is rather dangerous...

As I say, don't do it. Passwords on command lines is horrible.

	Tim.
-- 
Tim Oldham, BT Applied Systems. tjo@its.bt.co.uk or ...!ukc!axion!its!tjo
Less is more, but not as much as more.