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

Dmitry Kasatkin
2014-06-09T07:57:06Z

On 07/06/14 01:00, Mimi Zohar wrote:
> 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?

I think by mistake I was checking old patch in the thread because I have
not noticed strncmp(type, "keyring", 7).
This patch definitely should do the job.

- Dmitry

> thanks,
>
> Mimi
>
> Mimi
>
>
>