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

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Date:	Mon, 09 Jun 2014 10:56:38 +0300
From:	Dmitry Kasatkin <d.kasatkin@...sung.com>
To:	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	Dmitry Kasatkin <dmitry.kasatkin@...il.com>
Cc:	linux-security-module <linux-security-module@...r.kernel.org>,
	David Howells <dhowells@...hat.com>,
	Josh Boyer <jwboyer@...hat.com>,
	keyrings <keyrings@...ux-nfs.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v5 1/4] KEYS: special dot prefixed keyring name bug fix

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@...ux.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@...sung.com>
>>> Cc: David Howells <dhowells@...hat.com>
>>> Signed-off-by: Mimi Zohar <zohar@...ux.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
>
>
>

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