From 0626af3139572610b56376580d11eb65d45d9dd7 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 4 Sep 2012 07:49:03 +0000 Subject: netfilter: take care of timewait sockets Sami Farin reported crashes in xt_LOG because it assumes skb->sk is a full blown socket. Since (41063e9 ipv4: Early TCP socket demux), we can have skb->sk pointing to a timewait socket. Same fix is needed in nfnetlink_log. Diagnosed-by: Florian Westphal Reported-by: Sami Farin Signed-off-by: Eric Dumazet Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nfnetlink_log.c | 14 ++++++++------ net/netfilter/xt_LOG.c | 33 +++++++++++++++++---------------- 2 files changed, 25 insertions(+), 22 deletions(-) (limited to 'net') diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c index 14e2f39..5cfb5be 100644 --- a/net/netfilter/nfnetlink_log.c +++ b/net/netfilter/nfnetlink_log.c @@ -381,6 +381,7 @@ __build_packet_message(struct nfulnl_instance *inst, struct nlmsghdr *nlh; struct nfgenmsg *nfmsg; sk_buff_data_t old_tail = inst->skb->tail; + struct sock *sk; nlh = nlmsg_put(inst->skb, 0, 0, NFNL_SUBSYS_ULOG << 8 | NFULNL_MSG_PACKET, @@ -499,18 +500,19 @@ __build_packet_message(struct nfulnl_instance *inst, } /* UID */ - if (skb->sk) { - read_lock_bh(&skb->sk->sk_callback_lock); - if (skb->sk->sk_socket && skb->sk->sk_socket->file) { - struct file *file = skb->sk->sk_socket->file; + sk = skb->sk; + if (sk && sk->sk_state != TCP_TIME_WAIT) { + read_lock_bh(&sk->sk_callback_lock); + if (sk->sk_socket && sk->sk_socket->file) { + struct file *file = sk->sk_socket->file; __be32 uid = htonl(file->f_cred->fsuid); __be32 gid = htonl(file->f_cred->fsgid); - read_unlock_bh(&skb->sk->sk_callback_lock); + read_unlock_bh(&sk->sk_callback_lock); if (nla_put_be32(inst->skb, NFULA_UID, uid) || nla_put_be32(inst->skb, NFULA_GID, gid)) goto nla_put_failure; } else - read_unlock_bh(&skb->sk->sk_callback_lock); + read_unlock_bh(&sk->sk_callback_lock); } /* local sequence number */ diff --git a/net/netfilter/xt_LOG.c b/net/netfilter/xt_LOG.c index ff5f75f..2a4f969 100644 --- a/net/netfilter/xt_LOG.c +++ b/net/netfilter/xt_LOG.c @@ -145,6 +145,19 @@ static int dump_tcp_header(struct sbuff *m, const struct sk_buff *skb, return 0; } +static void dump_sk_uid_gid(struct sbuff *m, struct sock *sk) +{ + if (!sk || sk->sk_state == TCP_TIME_WAIT) + return; + + read_lock_bh(&sk->sk_callback_lock); + if (sk->sk_socket && sk->sk_socket->file) + sb_add(m, "UID=%u GID=%u ", + sk->sk_socket->file->f_cred->fsuid, + sk->sk_socket->file->f_cred->fsgid); + read_unlock_bh(&sk->sk_callback_lock); +} + /* One level of recursion won't kill us */ static void dump_ipv4_packet(struct sbuff *m, const struct nf_loginfo *info, @@ -361,14 +374,8 @@ static void dump_ipv4_packet(struct sbuff *m, } /* Max length: 15 "UID=4294967295 " */ - if ((logflags & XT_LOG_UID) && !iphoff && skb->sk) { - read_lock_bh(&skb->sk->sk_callback_lock); - if (skb->sk->sk_socket && skb->sk->sk_socket->file) - sb_add(m, "UID=%u GID=%u ", - skb->sk->sk_socket->file->f_cred->fsuid, - skb->sk->sk_socket->file->f_cred->fsgid); - read_unlock_bh(&skb->sk->sk_callback_lock); - } + if ((logflags & XT_LOG_UID) && !iphoff) + dump_sk_uid_gid(m, skb->sk); /* Max length: 16 "MARK=0xFFFFFFFF " */ if (!iphoff && skb->mark) @@ -717,14 +724,8 @@ static void dump_ipv6_packet(struct sbuff *m, } /* Max length: 15 "UID=4294967295 " */ - if ((logflags & XT_LOG_UID) && recurse && skb->sk) { - read_lock_bh(&skb->sk->sk_callback_lock); - if (skb->sk->sk_socket && skb->sk->sk_socket->file) - sb_add(m, "UID=%u GID=%u ", - skb->sk->sk_socket->file->f_cred->fsuid, - skb->sk->sk_socket->file->f_cred->fsgid); - read_unlock_bh(&skb->sk->sk_callback_lock); - } + if ((logflags & XT_LOG_UID) && recurse) + dump_sk_uid_gid(m, skb->sk); /* Max length: 16 "MARK=0xFFFFFFFF " */ if (!recurse && skb->mark) -- cgit v1.1 From 64f509ce71b08d037998e93dd51180c19b2f464c Mon Sep 17 00:00:00 2001 From: Jozsef Kadlecsik Date: Fri, 31 Aug 2012 09:55:53 +0000 Subject: netfilter: Mark SYN/ACK packets as invalid from original direction Clients should not send such packets. By accepting them, we open up a hole by wich ephemeral ports can be discovered in an off-path attack. See: "Reflection scan: an Off-Path Attack on TCP" by Jan Wrobel, http://arxiv.org/abs/1201.2074 Signed-off-by: Jozsef Kadlecsik Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nf_conntrack_proto_tcp.c | 19 ++++++++----------- 1 file changed, 8 insertions(+), 11 deletions(-) (limited to 'net') diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c index a5ac11e..aba98f9 100644 --- a/net/netfilter/nf_conntrack_proto_tcp.c +++ b/net/netfilter/nf_conntrack_proto_tcp.c @@ -158,21 +158,18 @@ static const u8 tcp_conntracks[2][6][TCP_CONNTRACK_MAX] = { * sCL -> sSS */ /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ -/*synack*/ { sIV, sIV, sIG, sIG, sIG, sIG, sIG, sIG, sIG, sSR }, +/*synack*/ { sIV, sIV, sSR, sIV, sIV, sIV, sIV, sIV, sIV, sSR }, /* * sNO -> sIV Too late and no reason to do anything * sSS -> sIV Client can't send SYN and then SYN/ACK * sS2 -> sSR SYN/ACK sent to SYN2 in simultaneous open - * sSR -> sIG - * sES -> sIG Error: SYNs in window outside the SYN_SENT state - * are errors. Receiver will reply with RST - * and close the connection. - * Or we are not in sync and hold a dead connection. - * sFW -> sIG - * sCW -> sIG - * sLA -> sIG - * sTW -> sIG - * sCL -> sIG + * sSR -> sSR Late retransmitted SYN/ACK in simultaneous open + * sES -> sIV Invalid SYN/ACK packets sent by the client + * sFW -> sIV + * sCW -> sIV + * sLA -> sIV + * sTW -> sIV + * sCL -> sIV */ /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ /*fin*/ { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV }, -- cgit v1.1 From 4a70bbfaef0361d27272629d1a250a937edcafe4 Mon Sep 17 00:00:00 2001 From: Jozsef Kadlecsik Date: Fri, 31 Aug 2012 09:55:54 +0000 Subject: netfilter: Validate the sequence number of dataless ACK packets as well We spare nothing by not validating the sequence number of dataless ACK packets and enabling it makes harder off-path attacks. See: "Reflection scan: an Off-Path Attack on TCP" by Jan Wrobel, http://arxiv.org/abs/1201.2074 Signed-off-by: Jozsef Kadlecsik Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nf_conntrack_proto_tcp.c | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-) (limited to 'net') diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c index aba98f9..e046b37 100644 --- a/net/netfilter/nf_conntrack_proto_tcp.c +++ b/net/netfilter/nf_conntrack_proto_tcp.c @@ -630,15 +630,9 @@ static bool tcp_in_window(const struct nf_conn *ct, ack = sack = receiver->td_end; } - if (seq == end - && (!tcph->rst - || (seq == 0 && state->state == TCP_CONNTRACK_SYN_SENT))) + if (tcph->rst && seq == 0 && state->state == TCP_CONNTRACK_SYN_SENT) /* - * Packets contains no data: we assume it is valid - * and check the ack value only. - * However RST segments are always validated by their - * SEQ number, except when seq == 0 (reset sent answering - * SYN. + * RST sent answering SYN. */ seq = end = sender->td_end; -- cgit v1.1 From 16af511a666827eaf5802144f09e2fb7b0942c99 Mon Sep 17 00:00:00 2001 From: Joe Perches Date: Wed, 12 Sep 2012 02:04:53 +0000 Subject: netfilter: log: Fix log-level processing auto75914331@hushmail.com reports that iptables does not correctly output the KERN_. $IPTABLES -A RULE_0_in -j LOG --log-level notice --log-prefix "DENY in: " result with linux 3.6-rc5 Sep 12 06:37:29 xxxxx kernel: <5>DENY in: IN=eth0 OUT= MAC=....... result with linux 3.5.3 and older: Sep 9 10:43:01 xxxxx kernel: DENY in: IN=eth0 OUT= MAC...... commit 04d2c8c83d0 ("printk: convert the format for KERN_ to a 2 byte pattern") updated the syslog header style but did not update netfilter uses. Do so. Use KERN_SOH and string concatenation instead of "%c" KERN_SOH_ASCII as suggested by Eric Dumazet. Signed-off-by: Joe Perches cc: auto75914331@hushmail.com Signed-off-by: Pablo Neira Ayuso --- net/bridge/netfilter/ebt_log.c | 2 +- net/netfilter/xt_LOG.c | 4 ++-- 2 files changed, 3 insertions(+), 3 deletions(-) (limited to 'net') diff --git a/net/bridge/netfilter/ebt_log.c b/net/bridge/netfilter/ebt_log.c index f88ee53..92de5e5 100644 --- a/net/bridge/netfilter/ebt_log.c +++ b/net/bridge/netfilter/ebt_log.c @@ -80,7 +80,7 @@ ebt_log_packet(u_int8_t pf, unsigned int hooknum, unsigned int bitmask; spin_lock_bh(&ebt_log_lock); - printk("<%c>%s IN=%s OUT=%s MAC source = %pM MAC dest = %pM proto = 0x%04x", + printk(KERN_SOH "%c%s IN=%s OUT=%s MAC source = %pM MAC dest = %pM proto = 0x%04x", '0' + loginfo->u.log.level, prefix, in ? in->name : "", out ? out->name : "", eth_hdr(skb)->h_source, eth_hdr(skb)->h_dest, diff --git a/net/netfilter/xt_LOG.c b/net/netfilter/xt_LOG.c index 2a4f969..91e9af4 100644 --- a/net/netfilter/xt_LOG.c +++ b/net/netfilter/xt_LOG.c @@ -443,8 +443,8 @@ log_packet_common(struct sbuff *m, const struct nf_loginfo *loginfo, const char *prefix) { - sb_add(m, "<%d>%sIN=%s OUT=%s ", loginfo->u.log.level, - prefix, + sb_add(m, KERN_SOH "%c%sIN=%s OUT=%s ", + '0' + loginfo->u.log.level, prefix, in ? in->name : "", out ? out->name : ""); #ifdef CONFIG_BRIDGE_NETFILTER -- cgit v1.1