Subject: Re: [PATCH v2 1/2] netfilter_queue: enable UID/GID socket info retrieval

From: Pablo Neira Ayuso <[email-masked]>
Date: Fri, 20 Dec 2013 10:26:38 +0100

Hi,

On Thu, Dec 19, 2013 at 12:03:26PM +0100, [email-masked] wrote:
> From: Valentina Giusti <[email-masked]>
> 
> Thanks to commits 41063e9 (ipv4: Early TCP socket demux) and 421b388 (udp: ipv4:
> Add udp early demux) it is now possible to parse UID and GID socket info
> also for incoming TCP and UDP connections. Having this info available, it
> is convenient to let NFQUEUE parse it in order to improve and refine the
> traffic analysis in userspace.
> 
> Signed-off-by: Valentina Giusti <[email-masked]>
> ---
>  include/uapi/linux/netfilter/nfnetlink_queue.h |  5 ++++-
>  net/netfilter/nfnetlink_queue_core.c           | 31 ++++++++++++++++++++++++++
>  2 files changed, 35 insertions(+), 1 deletion(-)
> 
> diff --git a/include/uapi/linux/netfilter/nfnetlink_queue.h b/include/uapi/linux/netfilter/nfnetlink_queue.h
> index 0132bad..8dd819e 100644
> --- a/include/uapi/linux/netfilter/nfnetlink_queue.h
> +++ b/include/uapi/linux/netfilter/nfnetlink_queue.h
> @@ -47,6 +47,8 @@ enum nfqnl_attr_type {
>  	NFQA_CAP_LEN,			/* __u32 length of captured packet */
>  	NFQA_SKB_INFO,			/* __u32 skb meta information */
>  	NFQA_EXP,			/* nf_conntrack_netlink.h */
> +	NFQA_UID,			/* __u32 sk uid */
> +	NFQA_GID,			/* __u32 sk gid */
>  
>  	__NFQA_MAX
>  };
> @@ -99,7 +101,8 @@ enum nfqnl_attr_config {
>  #define NFQA_CFG_F_FAIL_OPEN			(1 << 0)
>  #define NFQA_CFG_F_CONNTRACK			(1 << 1)
>  #define NFQA_CFG_F_GSO				(1 << 2)
> -#define NFQA_CFG_F_MAX				(1 << 3)
> +#define NFQA_CFG_F_UID_GID			(1 << 3)
> +#define NFQA_CFG_F_MAX				(1 << 4)
>  
>  /* 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 21258cf..2cdef07 100644
> --- a/net/netfilter/nfnetlink_queue_core.c
> +++ b/net/netfilter/nfnetlink_queue_core.c
> @@ -297,6 +297,29 @@ nfqnl_put_packet_info(struct sk_buff *nlskb, struct sk_buff *packet,
>  	return flags ? nla_put_be32(nlskb, NFQA_SKB_INFO, htonl(flags)) : 0;
>  }
>  
> +static int nfqnl_put_sk_uidgid(struct sk_buff *skb, struct sock *sk)
> +{
> +	const struct cred *cred;
> +
> +	if (sk && sk->sk_state != TCP_TIME_WAIT) {
> +		read_lock_bh(&sk->sk_callback_lock);
> +		if (sk->sk_socket && sk->sk_socket->file) {
> +			cred = sk->sk_socket->file->f_cred;
> +			if (nla_put_u32(skb, NFQA_UID, htonl(cred->fsuid)))

I'm hitting this compilation error here:

net/netfilter/nfnetlink_queue_core.c: In function ‘nfqnl_put_sk_uidgid’:
net/netfilter/nfnetlink_queue_core.c:308:4: error: aggregate value used where an integer was expected

It seems that in recent kernels you have to use:

        from_kuid_munged(&init_user_ns, cred->fsuid);

to retrieve the integer that represents the uid.

Please, 

> +				goto nla_put_failure;
> +			if (nla_put_u32(skb, NFQA_GID, htonl(cred->fsgid)))
                                    ^^^

Minor nitpick: This has to be _be32 otherwise sparse will complain
(spotted by Florian Westphal).

Make sure you patch is also clean when running make C=2.

Also remove the extra checking for socket that Florian mentioned and
resubmit. Thanks.