Re: [ptxdist] [PATCH v2 5/8] dropbear: Refactor rc-once and init to use KEYTYPES

[Michael Olbrich <m.olbrich@pengutronix.de>]

On Fri, Oct 22, 2021 at 11:05:37AM +0200, Alexander Dahl wrote:
> Hello Michael,
> 
> Am Freitag, 22. Oktober 2021, 10:44:05 CEST schrieb Michael Olbrich:
> > On Mon, Oct 18, 2021 at 04:35:51PM +0200, Alexander Dahl wrote:
> > > Previously DSS and RSA keys were always generated, regardless if
> > > dropbear was built with support for that host key or not, which somehow
> > > contradicts what commit message of 01ac7cc409b5 ("dropbear: Remove
> > > deprecated options") promised.
> > > 
> > > No other things changed here, just considering that KEYTYPES list for
> > > 'rsa' and 'dss' for now.
> > > 
> > > Signed-off-by: Alexander Dahl <ada@thorsis.com>
> > > ---
> > > 
> > >  projectroot/etc/init.d/dropbear    | 17 ++++++++++++++---
> > >  projectroot/etc/rc.once.d/dropbear | 26 +++++++++++++++++++++++---
> > >  2 files changed, 37 insertions(+), 6 deletions(-)
> > > 
> > > diff --git a/projectroot/etc/init.d/dropbear
> > > b/projectroot/etc/init.d/dropbear index 342565f93..88ef5aa71 100644
> > > --- a/projectroot/etc/init.d/dropbear
> > > +++ b/projectroot/etc/init.d/dropbear
> > > @@ -15,10 +15,21 @@ test -z "$DROPBEAR_BANNER" || \
> > > 
> > >    DROPBEAR_EXTRA_ARGS="$DROPBEAR_EXTRA_ARGS -b $DROPBEAR_BANNER"
> > >  
> > >  dropbear_start() {
> > > 
> > > -
> > > 
> > >      KEY_ARGS=""
> > > 
> > > -    test -f $DROPBEAR_DSSKEY && KEY_ARGS="$KEY_ARGS -d $DROPBEAR_DSSKEY"
> > > -    test -f $DROPBEAR_RSAKEY && KEY_ARGS="$KEY_ARGS -r $DROPBEAR_RSAKEY"
> > > +    for keytype in $DROPBEAR_KEYTYPES
> > > +    do
> > > +        case "$keytype" in
> > > +            dss)
> > > +                test -f $DROPBEAR_DSSKEY && KEY_ARGS="$KEY_ARGS -d
> > > $DROPBEAR_DSSKEY" +                ;;
> > 
> > Isn't dss disabled completely? So do we actually need this?
> 
> Depends where you look. :-/
> 
> The option was removed from ptxdist menu, yes. It is discouraged to use, yes.
> 
> For the patch I did not want to refactor and change behaviour at the same 
> time, so I would propose another patch for removing dss key support from the 
> init and rc-once scripts. Should that come before or after the other changes?

Before please.

> >From dropbear point of view I'm not 100% sure, but I think it's still possible 
> to built with dss support. ptxdist does not make an explicit decision on that 
> and relies on dropbear internal defaults. Maybe we should disable that 
> explicitly? dropbear build is different from standard ways, so it's a little 
> harder to pin down all the options.

I looked at the code. It's build by default. So please disable it
explicitly.

And i noticed, that we still have an option for 3DES. Can you remove that
one as well. It's actually disabled by default.

Regards,
Michael

> Greets
> Alex
> 
> > 
> > Michael
> > 
> > > +            rsa)
> > > +                test -f $DROPBEAR_RSAKEY && KEY_ARGS="$KEY_ARGS -r
> > > $DROPBEAR_RSAKEY" +                ;;
> > > +            *)
> > > +                echo "Key type '$keytype' not supported"
> > > +                ;;
> > > +        esac
> > > +    done
> > > 
> > >      echo -n "starting dropbear..."
> > > 
> > > diff --git a/projectroot/etc/rc.once.d/dropbear
> > > b/projectroot/etc/rc.once.d/dropbear index dd922d727..a9a1d475c 100644
> > > --- a/projectroot/etc/rc.once.d/dropbear
> > > +++ b/projectroot/etc/rc.once.d/dropbear
> > > @@ -5,10 +5,11 @@
> > > PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin> 
> > >  . /usr/lib/init/dropbear.sh
> > >  
> > >  gen_key() {
> > > 
> > > -
> > > 
> > >  	key_type=$1
> > >  	key_file=$2
> > > 
> > > +	[ -e "$key_file" ] && return
> > > +
> > > 
> > >  	rm -f $key_file > /dev/null 2>&1
> > >  	
> > >  	echo -n "generating $key_type key..."
> > > 
> > > @@ -22,6 +23,25 @@ gen_key() {
> > > 
> > >  	fi
> > >  
> > >  }
> > > 
> > > -[ -e "$DROPBEAR_RSAKEY" ] || gen_key rsa "$DROPBEAR_RSAKEY"
> > > -[ -e "$DROPBEAR_DSSKEY" ] || gen_key dss "$DROPBEAR_DSSKEY"
> > > +gen_keys() {
> > > +	for keytype in $DROPBEAR_KEYTYPES
> > > +	do
> > > +		case "$keytype" in
> > > +			dss)
> > > +				gen_key dss "$DROPBEAR_DSSKEY"
> > > +				;;
> > > +			rsa)
> > > +				gen_key rsa "$DROPBEAR_RSAKEY"
> > > +				;;
> > > +			*)
> > > +				echo "Key type '$keytype' not supported"
> > > +				;;
> > > +		esac
> > > +	done
> > > +}
> > > 
> > > +if ! gen_keys
> > > +then
> > > +	echo "Generating SSH keys failed!"
> > > +	exit 1
> > > +fi
> 
> 
> -- 
> Alexander Dahl           Thorsis Technologies GmbH   T +49 391 544 563 1000
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