Adding a minimal shell to default rootfs

[mcastelino]

@jcvenegas can we add a shell to the rootfs. That will allow us to provide a debug console.
The current minimal set of tools does not have a shell pre-installed.

See clearcontainers/agent#122

[jodh-intel]

bash is probably too big for a basic shell. I don't think CLR currently has busybox (GPL-licensed) or toybox (BSD-licensed), but they are both autospec-able (I've got examples somewhere if needed).

[jcvenegas]

@jodh-intel, I will add bash by now after, I will work with CL team to add probably busybox.

[devimc]

I prefer to do not include bash or any other utility that will not be used by the agent,
less components -> less CVEs -> less vulnerabilities

[jcvenegas]

@devimc @mcastelino in case dont want to add it, it could be documented in clearcontainers/agent#122 to use EXTRA_PKGS="bash-bin" just for debugging

[devimc]

we can create a debugeable image running next command:

make clean
$ EXTRA_PKGS="dbus-bin dbus-autostart util-linux-bin p11-kit-bin bash shadow ca-certs dist-pam-configs xz-bin tar-bin grep-bin sed-bin pigz-bin iproute2-bin procps-ng-bin psstop-bin htop-bin curl nano pciutils usbutils-bin" make rootfs
$ IMG_SIZE="450MB" make image

also we can include any other package needed

[mcastelino]

@devimc @jodh-intel I would rather have some minimal shell, vs asking the user to rebuild the image. If it come to that, we should provide a debug image as part of our default package, so that we provide debuggability by default.

Also I do not buy that having bash will make our solution any worse from a security point of view. Our going in assumption for clear containers is that obtaining root in the VM is a given. We prevent further compromise.

[devimc]

@jcvenegas how many MB increase the image size?

[gorozco1]

my vote for toybox @jodh-intel

[devimc]

I wouldn't like to include bash in the "production" version of the CC image because I want to avoid any possible container escape (i.e chroot /proc/1/cwd)