initial add of chromeos shell and cros-term

initial add of chromeos shell and cros-term

BUG=chromium-os:3884
TEST=None yet.

cros-term takes care of launching the appropriate xterm stand-in, with a suitable environment.

crosh is a read-eval-print loop with a whitelisted set of commands.  It is intended to be started by our xterm, instead of bash, so that we don't have to give a full bash prompt.

I don't believe platform/window-manager is really the correct place to stash these scripts in the long term.  Short term, we'd like to land this in time to cherry-pick into R7, and window-manager seems like the best of the wrong places.

If this ends up being something we keep around, it probably deserves its own repo.

[rginda, 2010-06-07 23:21:52]

I'll be fixing the aterm sizing issues in another CL.

[Daniel Erat, 2010-06-07 23:41:16]

This looks okay to me, but you should probably find someone who knows more about
writing secure scripts to also take a look.  Python seems like it might be a
better choice for this (except maybe we don't want to add another dependency on
it).  And, did you consider rbash and reject it?

http://codereview.chromium.org/2733001/diff/1/3
File bin/crosh (right):

http://codereview.chromium.org/2733001/diff/1/3#newcode86
bin/crosh:86: expr "$1" : '^[[:alnum:].]*$' > /dev/null
Shouldn't you permit '-' as well?

[Daniel Erat, 2010-06-07 23:42:15]

http://codereview.chromium.org/2733001/diff/1/3
File bin/crosh (right):

http://codereview.chromium.org/2733001/diff/1/3#newcode86
bin/crosh:86: expr "$1" : '^[[:alnum:].]*$' > /dev/null
On 2010/06/07 23:41:16, Daniel Erat wrote:
> Shouldn't you permit '-' as well?

(While not letting users sneak in flags, of course.)

[rginda, 2010-06-08 00:02:02]

http://codereview.chromium.org/2733001/diff/1/3
File bin/crosh (right):

http://codereview.chromium.org/2733001/diff/1/3#newcode86
bin/crosh:86: expr "$1" : '^[[:alnum:].]*$' > /dev/null
On 2010/06/07 23:42:15, Daniel Erat wrote:
> On 2010/06/07 23:41:16, Daniel Erat wrote:
> > Shouldn't you permit '-' as well?
> 
> (While not letting users sneak in flags, of course.)

Yeah, good point.  I've split the checking into two functions.  Hostnames allow
only alphanumeric and [.-].  Usernames allow a few more characters that might
show up in a username.  Both MUST start with an alphanumeric.

[Will Drewry, 2010-06-08 15:11:15]

A few nits, but seems fine for now.  We should really just rewrite the wrapper
with a small bit of C, but this seems like it'll work for now -- and it's not
like it _actually_ acts as a security barrier -- more as gentle discouragement.

thanks for pulling it together quickly.

http://codereview.chromium.org/2733001/diff/11001/12001
File bin/cros-term (right):

http://codereview.chromium.org/2733001/diff/11001/12001#newcode1
bin/cros-term:1: #!/bin/bash
Why not just use /bin/sh?

http://codereview.chromium.org/2733001/diff/11001/12002
File bin/crosh (right):

http://codereview.chromium.org/2733001/diff/11001/12002#newcode1
bin/crosh:1: #!/bin/bash
Make sure that you add bash to a dependency somewhere in the ebuild since I
think the only package holding it in the image now is the memento_updater.sh

http://codereview.chromium.org/2733001/diff/11001/12002#newcode18
bin/crosh:18: if [ "$1" == "--dev" -o -f "/root/.dev_mode" ]; then
can we _not_ encode /root/.dev_mode here too or do you really need it here? 
/root/.dev_mode is/was? a temporary hack until we expose dev_mode via /sys/.... 
On real hardware, we won't change the read-only partition to have this file. 
(At best, we can mount --bind over /root/ but that seems like a hack to fix a
hack.)

If you need it, at least add a TODO :/

http://codereview.chromium.org/2733001/diff/11001/12002#newcode92
bin/crosh:92: function check_hostname() {
two check_hostnames? :)

http://codereview.chromium.org/2733001/diff/11001/12002#newcode99
bin/crosh:99: expr "$1" : '^[[:alnum:]][[:alnum:].~%$^\-]*$' > /dev/null
Are these characters just to cover the weird overloaded cases you see with
things like hydras?  (You may want to include a colon too fwiw)

Otherwise, most usernames don't have tilde, etc...

http://codereview.chromium.org/2733001/diff/11001/12002#newcode103
bin/crosh:103: expr "$1" : '^[[:digit:].]*$' > /dev/null
Why is the dot in there?