Re: [RFC PATCH v5 1/4] KEYS: special dot prefixed keyring name bug fix

Mimi Zohar
2014-06-06T22:00:39Z

On Sat, 2014-06-07 at 00:48 +0300, Dmitry Kasatkin wrote:
> On 3 June 2014 20:58, Mimi Zohar <zohar@linux.vnet.ibm.com> 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().
> >
> > Changelog v5:
> > - Only prevent userspace from creating a dot prefixed keyring, not
> > regular keys - Dmitry
> >
> > Reported-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
> > Cc: David Howells <dhowells@redhat.com>
> > Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
> > ---
> > 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..62a9952 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;
> > }
> > @@ -86,6 +84,10 @@ SYSCALL_DEFINE5(add_key, const char __user *, _type,
> > if (!*description) {
> > kfree(description);
> > description = NULL;
> > + } else if ((description[0] == '.') &&
> > + (strncmp(type, "keyring", 7) == 0)) {
> > + ret = -EPERM;
> > + goto error2;
> > }
> > }

> I think it does not another problem...
> It is not only prevent creating new keyring with ".abc" name but also
> prevent adding new key...
>
> this is wrong...

Seems to prevent creating a dot prefixed keyring, but permits creating a
dot prefixed key. Do you have an example?

thanks,

Mimi

Mimi