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chroot_before_main 1.0.0 - A method of executing dynamically linked executables
                           inside a change root without copying the dynamic
                           libraries into change root.
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chroot_before_main is a combination of a shared library and accompanying binary
which provides a method for executing a program inside a change root directory
without having to copy in all libraries that the program depends on.  This is
accomplished by placing a hook into the program just before main() is called.
This hook performs the chroot() call.

The dynamic library loader (ld.so) provides a mechanism called LD_AUDIT which
allows for a function callback after all dynamic libraries have been loaded,
but before the main() function is called.  In the case of chroot_before_main,
the library chroot_before_main.so contains a function called la_preinit().
la_preinit is where a chroot() is called to place the program in a chroot
jail. The program can be further locked down by disallowing the chrooted
program to call chroot() itself, which is a known exploit for breaking
out of a jail.

Ryan Chapman, [email protected]
Sun Jun  3 15:24:09 MDT 2012