netdev - Re: [PATCH] crypto: user - make NETLINK

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Date:   Tue, 9 Jul 2019 17:28:35 +0200
From:   Ondrej Mosnacek <omosnace@...hat.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     linux-crypto@...r.kernel.org, netdev@...r.kernel.org,
        "David S . Miller" <davem@...emloft.net>,
        Stephan Mueller <smueller@...onox.de>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        Don Zickus <dzickus@...hat.com>
Subject: Re: [PATCH] crypto: user - make NETLINK_CRYPTO work inside netns

On Tue, Jul 9, 2019 at 4:38 PM Herbert Xu <herbert@...dor.apana.org.au> wrote:
> On Tue, Jul 09, 2019 at 01:11:24PM +0200, Ondrej Mosnacek wrote:
> > Currently, NETLINK_CRYPTO works only in the init network namespace. It
> > doesn't make much sense to cut it out of the other network namespaces,
> > so do the minor plumbing work necessary to make it work in any network
> > namespace. Code inspired by net/core/sock_diag.c.
> >
> > Tested using kcapi-dgst from libkcapi [1]:
> > Before:
> >     # unshare -n kcapi-dgst -c sha256 </dev/null | wc -c
> >     libkcapi - Error: Netlink error: sendmsg failed
> >     libkcapi - Error: Netlink error: sendmsg failed
> >     libkcapi - Error: NETLINK_CRYPTO: cannot obtain cipher information for hmac(sha512) (is required crypto_user.c patch missing? see documentation)
> >     0
> >
> > After:
> >     # unshare -n kcapi-dgst -c sha256 </dev/null | wc -c
> >     32
> >
> > [1] https://github.com/smuellerDD/libkcapi
> >
> > Signed-off-by: Ondrej Mosnacek <omosnace@...hat.com>
>
> Should we really let root inside a namespace manipulate crypto
> algorithms which are global?

I admit I'm not an expert on Linux namespaces, but aren't you
confusing network and user namespaces? Unless I'm mistaken, these
changes only affect _network_ namespaces (which only isolate the
network stuff itself) and the semantics of the netlink_capable(skb,
CAP_NET_ADMIN) calls remain unchanged - they check if the opener of
the socket has the CAP_NET_ADMIN capability within the global _user_
namespace.

>
> I think we should only allow the query operations without deeper
> surgery.
>
> Cheers,
> --
> Email: Herbert Xu <herbert@...dor.apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

-- 
Ondrej Mosnacek <omosnace at redhat dot com>
Software Engineer, Security Technologies
Red Hat, Inc.