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Bugtraq archives for 4th quarter (Oct-Dec) 1994: Re: /dev/tcp, and a LD_LIBRARY_PATH question.

Re: /dev/tcp, and a LD_LIBRARY_PATH question.

hoodrhoodr.slip.netcom.com
Fri, 2 Dec 1994 19:28:20 +0000 

>Second question: How can I write a program that keeps the LD_LIBRARY_PATH
>variable from being exploited? i.e. the SUN 'login' bug where LD_LIBRARY_PATH
>got exploited. I would ASSUME I could prevent this by doing something like:
>putenv("LD_LIBRARY_PATH"), but that just seems too simple to be a true fix. 
>(If it's not complex, it's not right? :)

Don't assume that LD_LIBRAY_PATH is the only variable you have to
worry about.  I was able to easily break "sudo" with the LD_PRELOAD
variable (we've since fixed it by supplying a brand new environment,
instead of re-using the old one).

A strings on /usr/lib/ld.so, show the following items which are most
likley environment variables:
    LD_LIBRARY_PATH
    LD_TRACE_LOADED_OBJECTS
    LD_PROFILE
    LD_PRELOAD
    LD_SYMBOLS_PUBLIC

Of course only LD_LIBRARY_PATH seems to be documented in the man pages.
Maybe someone from Sun can comment on what the rest of these do (please?)

>From experimentation, the LD_PRELOAD variable should point to a
library (not a directory of libraries).  That library will be loaded
before the standard library path (or LD_LIBRARY_PATH) is searched.