Re: [RFC PATCH v4 1/4] KEYS: special dot prefixed keyring name bug fix

[Mimi Zohar]

On Fri, 2014-05-30 at 21:24 +0300, Dmitry Kasatkin wrote: 
> On 30 May 2014 20:58, "Mimi Zohar" <zohar@xxxxxxxxxxxxxxxxxx> wrote:
> >
> > On Fri, 2014-05-30 at 18:58 +0300, Dmitry Kasatkin wrote:
> > > On 28 May 2014 18:09, Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx> wrote:
> > > > Dot prefixed keyring names are supposed to be reserved for the
> > > > kernel, but add_key() calls key_get_type_from_user(), which
> > > > incorrectly verifies the 'type' field, not the 'description' field.
> > > > This patch verifies the 'description' field isn't dot prefixed,
> > > > when creating a new keyring, and removes the dot prefix test in
> > > > key_get_type_from_user().
> > > >
> > > > Reported-by: Dmitry Kasatkin <d.kasatkin@xxxxxxxxxxx>
> > > > Cc: David Howells <dhowells@xxxxxxxxxx>
> > > > Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx>
> > > > ---
> > > >  security/keys/keyctl.c | 6 ++++--
> > > >  1 file changed, 4 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
> > > > index cd5bd0c..9e9a762 100644
> > > > --- a/security/keys/keyctl.c
> > > > +++ b/security/keys/keyctl.c
> > > > @@ -37,8 +37,6 @@ static int key_get_type_from_user(char *type,
> > > >                 return ret;
> > > >         if (ret == 0 || ret >= len)
> > > >                 return -EINVAL;
> > > > -       if (type[0] == '.')
> > > > -               return -EPERM;
> > > >         type[len - 1] = '\0';
> > > >         return 0;
> > > >  }
> > > > @@ -87,6 +85,10 @@ SYSCALL_DEFINE5(add_key, const char __user *,
> _type,
> > > >                         kfree(description);
> > > >                         description = NULL;
> > > >                 }
> > > > +               if (description[0] == '.') {
> > > > +                       ret = -EPERM;
> > > > +                       goto error2;
> > > > +               }
> > >
> > > 1. 3 lines above "discription = NULL" will cause kernel oops...
> > > It happens when using empty description... like:
> > >
> > > cat x509_ima.der | keyctl padd asymmetric "" keyid
> >
> > Right, that should be 'else if'.
> >
> > > 2. It prevents adding trusted keys to ".ima" from user space...
> > > This is NOT what we want... right?
> >
> > It prevents creating a dot prefixed keyring.
> >
> 
> May be. But it prevents also adding the key....
> It needs to distinguish key adding and keyring adding then...

Perhaps, but assuming you created a keyring on @u, you would still need
to look up the keyid and use it.  The same is true here.  Instead of
using "keyctl search @u keyring _ima", you would use "keyctl describe %
keyring:.ima".  The first field is the keyring id.

Mimi

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