On 3/6/2020 4:58 PM, Paul Moore wrote:
> On Fri, Feb 14, 2020 at 6:43 PM Casey Schaufler <casey@xxxxxxxxxxxxxxxx> wrote:
>> Change security_secctx_to_secid() to fill in a lsmblob instead
>> of a u32 secid. Multiple LSMs may be able to interpret the
>> string, and this allows for setting whichever secid is
>> appropriate. In some cases there is scaffolding where other
>> interfaces have yet to be converted.
>>
>> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
>> Reviewed-by: John Johansen <john.johansen@xxxxxxxxxxxxx>
>> Acked-by: Stephen Smalley <sds@xxxxxxxxxxxxx>
>> Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
>> ---
>> include/linux/security.h | 5 +++--
>> kernel/cred.c | 4 +---
>> net/netfilter/nft_meta.c | 12 +++++++-----
>> net/netfilter/xt_SECMARK.c | 5 ++++-
>> net/netlabel/netlabel_unlabeled.c | 14 ++++++++------
>> security/security.c | 18 +++++++++++++++---
>> 6 files changed, 38 insertions(+), 20 deletions(-)
> ...
>
>> diff --git a/net/netfilter/nft_meta.c b/net/netfilter/nft_meta.c
>> index 951b6e87ed5d..e12125b85035 100644
>> --- a/net/netfilter/nft_meta.c
>> +++ b/net/netfilter/nft_meta.c
>> @@ -811,21 +811,23 @@ static const struct nla_policy nft_secmark_policy[NFTA_SECMARK_MAX + 1] = {
>>
>> static int nft_secmark_compute_secid(struct nft_secmark *priv)
>> {
>> - u32 tmp_secid = 0;
>> + struct lsmblob blob;
>> int err;
>>
>> - err = security_secctx_to_secid(priv->ctx, strlen(priv->ctx), &tmp_secid);
>> + err = security_secctx_to_secid(priv->ctx, strlen(priv->ctx), &blob);
>> if (err)
>> return err;
>>
>> - if (!tmp_secid)
>> + if (!lsmblob_is_set(&blob))
>> return -ENOENT;
>>
>> - err = security_secmark_relabel_packet(tmp_secid);
>> + /* Using le[0] is scaffolding */
>> + err = security_secmark_relabel_packet(blob.secid[0]);
>> if (err)
>> return err;
> At the very least it looks like the comment above needs an update.
I can see that.
> However, I would really like to see an explanation in this patch,
> either in the comments or in the commit description, about how you
> plan to handle secmarks.
Yes. It should probably be spread between here, 0017 and the introduction.
> If your plan is to always have it be the
> first LSM, let's admit that and document it appropriately. If there
> is something much grander coming later in the patchset I guess
> "scaffolding" is an okay term, but it would be good to mention in the
> commit description that this will be replaced with something better
> later in the patchset.
You are correct.
> I'm worried about the case five years from know when we are changing
> this code, either due to bugs or new features, and we stumble across
> this commit. Was it always intended to be this way? Or was this
> temporary? Right now I don't know.
>
>> - priv->secid = tmp_secid;
>> + /* Using le[0] is scaffolding */
>> + priv->secid = blob.secid[0];
>> return 0;
>> }
> ...
>
>> diff --git a/net/netlabel/netlabel_unlabeled.c b/net/netlabel/netlabel_unlabeled.c
>> index d2e4ab8d1cb1..7a5a87f15736 100644
>> --- a/net/netlabel/netlabel_unlabeled.c
>> +++ b/net/netlabel/netlabel_unlabeled.c
>> @@ -881,7 +881,7 @@ static int netlbl_unlabel_staticadd(struct sk_buff *skb,
>> void *addr;
>> void *mask;
>> u32 addr_len;
>> - u32 secid;
>> + struct lsmblob blob;
>> struct netlbl_audit audit_info;
>>
>> /* Don't allow users to add both IPv4 and IPv6 addresses for a
>> @@ -905,12 +905,13 @@ static int netlbl_unlabel_staticadd(struct sk_buff *skb,
>> ret_val = security_secctx_to_secid(
>> nla_data(info->attrs[NLBL_UNLABEL_A_SECCTX]),
>> nla_len(info->attrs[NLBL_UNLABEL_A_SECCTX]),
>> - &secid);
>> + &blob);
>> if (ret_val != 0)
>> return ret_val;
>>
>> + /* scaffolding with the [0] */
>> return netlbl_unlhsh_add(&init_net,
>> - dev_name, addr, mask, addr_len, secid,
>> + dev_name, addr, mask, addr_len, blob.secid[0],
>> &audit_info);
>> }
> Same as above, although this time with the peer label.
>
