Bugtraq: Re: Possible issue with Cisco on-line help?

[lnapier () CISCO COM (Lisa Napier)]

Hi Fernando,

I confirmed this behavior, and found some history on why we did things this way.

The original intent of showing a limited subset of commands at the "show ?" help command was to simplify the command 
line help subsystem.  When user typed the command "show ?", we intended to provide them a list of only the most used 
and useful commands at that level.

To allow customers to see all the commands available at that level, the command "terminal full-help" was implemented in 
October of 1993.

The intent was not security related at all, but simply an attempt to provide only the 'useful' commands to the users 
who were supposed to be at that prompt and at that level, rather than having them scroll through several screens of 
available but not very useful commands.

So, rather than being an inadvertent mistake in the parser, this is actually how the product was designed.

I will be updating our white papers on securing routers to include the recommendation of setting the default user 
privilege level to 0, and ensuring that only commands that are explicitly permitted to be run by un-enabled users are 
set to priv level 0.

Thanks much for your work on this Fernando,

Lisa Napier
Product Security Incident Response Team
Cisco Systems
http://www.cisco.com/warp/public/707/sec_incident_response.shtml

At 12:04 PM 05/04/2000 +0000, Fernando Montenegro wrote:
> Hi!
>
> I have received information from Matti Saarinen
> <mjs () cc tut fi> explaining how the on-line help can be
> configured to show all the commands available (see below).
>
> This explains the apparent lack of authorization control
> over the "show" options.
>
> It seems that the only issue left is that there is so much
> information available from the non-enabled account.I would
> think that, on account of that, the recommendation for
> "jailing" the user still applies, though.
>
> Cheers,
> Fernando
>
>
> Extracts from the message received from Matti Saarinen
> <mjs () cc tut fi>:
>
> >  Router2>show ?>    backup         Backup status
> >    cef            Cisco Express Forwarding
> >    clock          Display the system clock
> >    dialer         Dialer parameters and statistics
> >    flash:         display information about flash: file>
> system
> >    history        Display the session command history>
> ...>
> > Notice that we did not see an "access-lists" option, so
> the
> > help system thinks we should not be able to run it...
>         Yes, you cannot normally see access-lists option in
>         the output of the help system.
> router>sh ?
>   alps           Alps information
>   atm            ATM information
>   backup         Backup status[cut]
>
>         But when you enable full help the access-lists
> option is there
>         with many others:
> router>terminal full-help
> router>sh ?
>   access-expression  List access expression
>   access-lists       List access lists
>   adjacency          Adjacent nodes
>   aliases            Display alias commands
>   alps               Alps information
>   arp                ARP table
>   async              Information on terminal lines used as
> router interfaces
>   atm                ATM information
>   backup             Backup status
>         And the privilege level was 1 the whole time:
> router>sh priv
> Current privilege level is 1