From 6ee584be3ee30f72dec8a8ca87bc10824e27a631 Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Mon, 24 Sep 2012 14:52:12 +0200 Subject: [PATCH] netfilter: nfnetlink_queue: add NFQA_CAP_LEN attribute This patch adds the NFQA_CAP_LEN attribute that allows us to know what is the real packet size from user-space (even if we decided to retrieve just a few bytes from the packet instead of all of it). Security software that inspects packets should always check for this new attribute to make sure that it is inspecting the entire packet. This also helps to provide a workaround for the problem described in: http://marc.info/?l=netfilter-devel&m=134519473212536&w=2 Original idea from Florian Westphal. Signed-off-by: Pablo Neira Ayuso --- include/linux/netfilter/nfnetlink_queue.h | 1 + net/netfilter/nfnetlink_queue_core.c | 9 +++++++-- 2 files changed, 8 insertions(+), 2 deletions(-) diff --git a/include/linux/netfilter/nfnetlink_queue.h b/include/linux/netfilter/nfnetlink_queue.h index 3b1c1360aedf..70ec8c2bc11a 100644 --- a/include/linux/netfilter/nfnetlink_queue.h +++ b/include/linux/netfilter/nfnetlink_queue.h @@ -44,6 +44,7 @@ enum nfqnl_attr_type { NFQA_PAYLOAD, /* opaque data payload */ NFQA_CT, /* nf_conntrack_netlink.h */ NFQA_CT_INFO, /* enum ip_conntrack_info */ + NFQA_CAP_LEN, /* __u32 length of captured packet */ __NFQA_MAX }; diff --git a/net/netfilter/nfnetlink_queue_core.c b/net/netfilter/nfnetlink_queue_core.c index 3e4ddcb7e781..e12d44e75b21 100644 --- a/net/netfilter/nfnetlink_queue_core.c +++ b/net/netfilter/nfnetlink_queue_core.c @@ -225,7 +225,7 @@ nfqnl_build_packet_message(struct nfqnl_instance *queue, { sk_buff_data_t old_tail; size_t size; - size_t data_len = 0; + size_t data_len = 0, cap_len = 0; struct sk_buff *skb; struct nlattr *nla; struct nfqnl_msg_packet_hdr *pmsg; @@ -247,7 +247,8 @@ nfqnl_build_packet_message(struct nfqnl_instance *queue, #endif + nla_total_size(sizeof(u_int32_t)) /* mark */ + nla_total_size(sizeof(struct nfqnl_msg_packet_hw)) - + nla_total_size(sizeof(struct nfqnl_msg_packet_timestamp)); + + nla_total_size(sizeof(struct nfqnl_msg_packet_timestamp) + + nla_total_size(sizeof(u_int32_t))); /* cap_len */ outdev = entry->outdev; @@ -266,6 +267,7 @@ nfqnl_build_packet_message(struct nfqnl_instance *queue, data_len = entskb->len; size += nla_total_size(data_len); + cap_len = entskb->len; break; } @@ -402,6 +404,9 @@ nfqnl_build_packet_message(struct nfqnl_instance *queue, if (ct && nfqnl_ct_put(skb, ct, ctinfo) < 0) goto nla_put_failure; + if (cap_len > 0 && nla_put_be32(skb, NFQA_CAP_LEN, htonl(cap_len))) + goto nla_put_failure; + nlh->nlmsg_len = skb->tail - old_tail; return skb; -- 2.20.1