So after some discussion on the security mailing list i had to figure out a way to implement what i wanted
without added security functions and ops.
So the below v4 patch version does that, is uses the secmark field of the sk_buff structure to get the
secid and map that to the security context. I tested it and it works with SMACK and the option:
CONFIG_SECURITY_SMACK_NETFILTER
i don't know about SELinux but it should work assuming that they map secid to secctx.
-- cut here
This patch adds an additional attribute when sending
packet information via netlink in netfilter_queue module.
It will send additional security context data, so that
userspace applications can verify this context against
their own security databases.
Signed-off-by: Roman Kubiak <r.kubiak@xxxxxxxxxxx>
---
v2:
- nfqnl_get_sk_secctx returns seclen now, this changes
- updated size calculation
- changed NFQA_SECCTX comment
- removed duplicate testing of NFQA_CFG_F flags
v3:
- NULL is not added to the security context anymore
- return 0 when socket is invalid in nfqnl_get_sk_secctx
- small intent change
- removed ret variable in nfqnl_get_sk_secctx
v4:
- removed security dependency, this patch does not
require any changes in other subsystems
- nfqnl_get_sk_secctx returns seclen
- added IFDEF when using secmark from the sk_buff
structure
---
---
include/uapi/linux/netfilter/nfnetlink_queue.h | 4 +++-
net/netfilter/nfnetlink_queue_core.c | 29 ++++++++++++++++++++++++++
2 files changed, 32 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/netfilter/nfnetlink_queue.h b/include/uapi/linux/netfilter/nfnetlink_queue.h
index 8dd819e..b67a853 100644
--- a/include/uapi/linux/netfilter/nfnetlink_queue.h
+++ b/include/uapi/linux/netfilter/nfnetlink_queue.h
@@ -49,6 +49,7 @@ enum nfqnl_attr_type {
NFQA_EXP, /* nf_conntrack_netlink.h */
NFQA_UID, /* __u32 sk uid */
NFQA_GID, /* __u32 sk gid */
+ NFQA_SECCTX, /* security context string */
__NFQA_MAX
};
@@ -102,7 +103,8 @@ enum nfqnl_attr_config {
#define NFQA_CFG_F_CONNTRACK (1 << 1)
#define NFQA_CFG_F_GSO (1 << 2)
#define NFQA_CFG_F_UID_GID (1 << 3)
-#define NFQA_CFG_F_MAX (1 << 4)
+#define NFQA_CFG_F_SECCTX (1 << 4)
+#define NFQA_CFG_F_MAX (1 << 5)
/* flags for NFQA_SKB_INFO */
/* packet appears to have wrong checksums, but they are ok */
diff --git a/net/netfilter/nfnetlink_queue_core.c b/net/netfilter/nfnetlink_queue_core.c
index 0b98c74..2c35112 100644
--- a/net/netfilter/nfnetlink_queue_core.c
+++ b/net/netfilter/nfnetlink_queue_core.c
@@ -278,6 +278,24 @@ nla_put_failure:
return -1;
}
+static u32 nfqnl_get_sk_secctx(struct sk_buff *skb, char **secdata)
+{
+ u32 seclen = 0;
+
+ if (!skb || !sk_fullsock(skb->sk))
+ return 0;
+
+#if IS_ENABLED(CONFIG_NETWORK_SECMARK)
+ read_lock_bh(&skb->sk->sk_callback_lock);
+
+ if (skb->secmark)
+ security_secid_to_secctx(skb->secmark, secdata, &seclen);
+
+ read_unlock_bh(&skb->sk->sk_callback_lock);
+#endif
+ return seclen;
+}
+
static struct sk_buff *
nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
struct nf_queue_entry *entry,
@@ -297,6 +315,8 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
struct nf_conn *ct = NULL;
enum ip_conntrack_info uninitialized_var(ctinfo);
bool csum_verify;
+ char *secdata = NULL;
+ u32 seclen = 0;
size = nlmsg_total_size(sizeof(struct nfgenmsg))
+ nla_total_size(sizeof(struct nfqnl_msg_packet_hdr))
@@ -352,6 +372,12 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
+ nla_total_size(sizeof(u_int32_t))); /* gid */
}
+ if ((queue->flags & NFQA_CFG_F_SECCTX) && entskb->sk) {
+ seclen = nfqnl_get_sk_secctx(entskb, &secdata);
+ if (seclen)
+ size += nla_total_size(seclen);
+ }
+
skb = nfnetlink_alloc_skb(net, size, queue->peer_portid,
GFP_ATOMIC);
if (!skb) {
@@ -479,6 +505,9 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
nfqnl_put_sk_uidgid(skb, entskb->sk) < 0)
goto nla_put_failure;
+ if (seclen && nla_put(skb, NFQA_SECCTX, seclen, secdata))
+ goto nla_put_failure;
+
if (ct && nfqnl_ct_put(skb, ct, ctinfo) < 0)
goto nla_put_failure;
--
1.9.1
On 05/27/2015 02:49 PM, Pablo Neira Ayuso wrote:
> On Wed, May 27, 2015 at 01:12:42PM +0200, Roman Kubiak wrote:
>> I think i forgot to mention one important thing the function:
>> security_sk_getsecid is not in the kernel yet, i posted a patch to
>> add it on the linux-security-module mailing list:
>> http://marc.info/?t=143254934900006&r=1&w=2
>
> You shouldn't split the patches between several lists, they are
> interdependent and without that context it is normal that people don't
> understand your intentions.
>
> So please send the full patchset, Cc'ing the relevant lists so we can
> get feedback from both the netfilter and the linux-security
> communities.
>
> BTW, another minor nitpick below:
>
>>> diff --git a/net/netfilter/nfnetlink_queue_core.c b/net/netfilter/nfnetlink_queue_core.c
>>> index 0b98c74..ae4f520 100644
>>> --- a/net/netfilter/nfnetlink_queue_core.c
>>> +++ b/net/netfilter/nfnetlink_queue_core.c
>>> @@ -278,6 +278,24 @@ nla_put_failure:
>>> return -1;
>>> }
>>>
>>> +static u32 nfqnl_get_sk_secctx(struct sock *sk, char **secdata)
>>> +{
>>> + u32 secid = 0;
>>> + u32 seclen = 0;
>
> Merge these two variable declarations in one line.
>
> Thanks.
> --
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>
--
--------------
Roman Kubiak
--------------
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