Re: [PATCH v2] nfnetlink_queue: add security context information

[Florian Westphal <fw@strlen.de>]

Roman Kubiak <r.kubiak@samsung.com> wrote:
> I was wondering, assuming i remove the NULL termination and SMACK sends a piece of data that's not null terminated,
> how, on the userland side, can i find out about that size ?

The size of netlink attribute is stored in netlink header.
For old libnfnetlink based api, see nfq_get_payload() in
libnetfilter_queue.

> Please notice that i send a libnetfilter_queue patch:
> [PATCH] libnetfitler_queue: receive security context info
> 
> it uses
> *secdata = (unsigned char *)nfnl_get_pointer_to_data(nfad->data, NFQA_SECCTX, char);
> to get the security context data, but there is no info about the size, where can i find that not to go over bounds and read beyond what i should ?

NFQ_PAYLOAD(nfad->data[NFQA_SECCTX - 1])

For libmnl based api (preferred), you'd use

mnl_nlmsg_get_payload_len(attr[NFQA_SECCTX])