On 09/21/2018 04:57 PM, David Howells wrote:
> Dave Jiang <[email protected]> wrote:
>
>> + new_key = key_alloc(&key_type_logon, key->description,
>> + GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, &init_cred, 0,
>
> KEY_POS_SEARCH? KEY_USR_VIEW?
>
>> + KEY_ALLOC_NOT_IN_QUOTA, NULL);
>> + ...
>> + down_read(&key->sem);
>> + payload = key->payload.data[0];
>> + rc = key_instantiate_and_link(new_key, payload->data, key->datalen,
>
> payload->datalen, not key->datalen.
>
>> + nvdimm_keyring, NULL);
>
> Okay, that's a weird way of going about things. I presume you don't want to
> add key to nvdimm_keyring - maybe in case it gets updated whilst you're using
> it and your private key isn't in quota?
>
>> + up_read(&key->sem);
>> + if (rc < 0) {
>> + key_revoke(new_key);
>> + key_put(new_key);
>> + return NULL;
>> + }
>
> Just putting it here should work since it didn't get linked to the keyring if
> any errors occurred. Revoking it too shouldn't be necessary.
>
>> + key_invalidate(key);
>> + key_put(key);
>
> Why are you invalidating the user's key?
>
>> + keyref = lookup_user_key(id, 0, 0);
>
> KEY_NEED_SEARCH? Though I suppose it's not strictly necessary as it's a key
> that's private to the kernel.
>
>> + if (old_keyid != 0) {
>> + old_key = nvdimm_get_key(dev);
>> + if (old_key) {
>> + if (key_serial(old_key) != old_keyid) {
>
> Ummm... That's not what I meant. Given the permissions you've set on your
> private key, userspace shouldn't be able to find it, let alone give you the
> key ID.
>
> What I meant here was to use, say, nvdimm_lookup_user_key() to get a key from
> userspace that contains the old password. You can use the description of the
> key to search nvdimm_keyring for the private key and then compare the
> passwords.
Ok I have a bit of confusion here. When the user injects a new key with
the same description and new passphrase, would that not replace the
existing user key with the old passphrase? Also, if I'm calling
lookup_user_key, where would the key_id come from for the old user key?
I suppose I can cache it.... Maybe I'm not quite understanding the exact
flow of how things you are suggesting.
>
> Then you don't need to passphrases in the new key.
>
>> + rc = nvdimm_check_key_len(key->datalen, update);
>
> payload->datalen.
>
>> + down_read(&key->sem);
>
> This needs to be earlier. The payload attached to the new key can be replaced
> by keyctl_update() at any time whilst you're not holding the lock, so you
> cannot use key->payload[*] without holding the lock or the RCU read lock.
>
>> + if (update)
>> + key_invalidate(key);
>
> The key doesn't belong to you - should you really be invalidating it?
>
>> + else {
>> + key_link(nvdimm_keyring, key);
>> + nvdimm->key = key;
>> + key->perm |= KEY_USR_SEARCH;
>> + }
>
> Um - do you really want to be taking the key into your internal keyring? Why
> aren't you calling nvdimm_replace_key()? Also, you shouldn't alter the
> permission - it's not your key.
>
>> +static int __parse_update(const char *buf, size_t len, unsigned int *old_id,
>> + unsigned int *new_id)
>> +{
>
> Try using sscanf()?
>
> David
>
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