[NETFILTER]: ipt_REJECT: properly handle IP options
The current TCP RST construction reuses the old packet and can't deal with IP options as a consequence of that. Construct the RST from scratch instead. Signed-off-by: Patrick McHardy <kaber@trash.net> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Denys Vlasenko
David S. Miller
parent
022748a935
commit
9ba99b0d3f
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@ -35,11 +35,8 @@ MODULE_DESCRIPTION("Xtables: packet \"rejection\" target for IPv4");
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static void send_reset(struct sk_buff *oldskb, int hook)
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{
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struct sk_buff *nskb;
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struct iphdr *niph;
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struct iphdr *oiph, *niph;
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struct tcphdr _otcph, *oth, *tcph;
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__be16 tmp_port;
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__be32 tmp_addr;
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int needs_ack;
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unsigned int addr_type;
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/* IP header checks: fragment. */
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@ -58,69 +55,47 @@ static void send_reset(struct sk_buff *oldskb, int hook)
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/* Check checksum */
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if (nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), IPPROTO_TCP))
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return;
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oiph = ip_hdr(oldskb);
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/* We need a linear, writeable skb. We also need to expand
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headroom in case hh_len of incoming interface < hh_len of
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outgoing interface */
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nskb = skb_copy_expand(oldskb, LL_MAX_HEADER, skb_tailroom(oldskb),
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GFP_ATOMIC);
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nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) +
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LL_MAX_HEADER, GFP_ATOMIC);
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if (!nskb)
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return;
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/* This packet will not be the same as the other: clear nf fields */
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nf_reset(nskb);
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nskb->mark = 0;
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skb_init_secmark(nskb);
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skb_reserve(nskb, LL_MAX_HEADER);
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skb_shinfo(nskb)->gso_size = 0;
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skb_shinfo(nskb)->gso_segs = 0;
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skb_shinfo(nskb)->gso_type = 0;
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skb_reset_network_header(nskb);
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niph = (struct iphdr *)skb_put(nskb, sizeof(struct iphdr));
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niph->version = 4;
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niph->ihl = sizeof(struct iphdr) / 4;
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niph->tos = 0;
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niph->id = 0;
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niph->frag_off = htons(IP_DF);
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niph->protocol = IPPROTO_TCP;
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niph->check = 0;
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niph->saddr = oiph->daddr;
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niph->daddr = oiph->saddr;
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tcph = (struct tcphdr *)(skb_network_header(nskb) + ip_hdrlen(nskb));
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tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr));
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memset(tcph, 0, sizeof(*tcph));
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tcph->source = oth->dest;
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tcph->dest = oth->source;
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tcph->doff = sizeof(struct tcphdr) / 4;
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/* Swap source and dest */
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niph = ip_hdr(nskb);
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tmp_addr = niph->saddr;
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niph->saddr = niph->daddr;
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niph->daddr = tmp_addr;
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tmp_port = tcph->source;
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tcph->source = tcph->dest;
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tcph->dest = tmp_port;
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/* Truncate to length (no data) */
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tcph->doff = sizeof(struct tcphdr)/4;
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skb_trim(nskb, ip_hdrlen(nskb) + sizeof(struct tcphdr));
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if (tcph->ack) {
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needs_ack = 0;
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if (oth->ack)
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tcph->seq = oth->ack_seq;
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tcph->ack_seq = 0;
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} else {
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needs_ack = 1;
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else {
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tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin +
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oldskb->len - ip_hdrlen(oldskb) -
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(oth->doff << 2));
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tcph->seq = 0;
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tcph->ack = 1;
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}
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/* Reset flags */
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((u_int8_t *)tcph)[13] = 0;
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tcph->rst = 1;
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tcph->ack = needs_ack;
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tcph->window = 0;
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tcph->urg_ptr = 0;
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/* Adjust TCP checksum */
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tcph->check = 0;
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tcph->check = tcp_v4_check(sizeof(struct tcphdr),
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niph->saddr, niph->daddr,
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csum_partial(tcph,
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sizeof(struct tcphdr), 0));
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/* Set DF, id = 0 */
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niph->frag_off = htons(IP_DF);
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niph->id = 0;
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tcph->rst = 1;
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tcph->check = tcp_v4_check(sizeof(struct tcphdr),
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niph->saddr, niph->daddr,
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csum_partial(tcph,
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sizeof(struct tcphdr), 0));
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addr_type = RTN_UNSPEC;
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if (hook != NF_INET_FORWARD
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@ -130,14 +105,16 @@ static void send_reset(struct sk_buff *oldskb, int hook)
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)
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addr_type = RTN_LOCAL;
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/* ip_route_me_harder expects skb->dst to be set */
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dst_hold(oldskb->dst);
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nskb->dst = oldskb->dst;
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if (ip_route_me_harder(nskb, addr_type))
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goto free_nskb;
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niph->ttl = dst_metric(nskb->dst, RTAX_HOPLIMIT);
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nskb->ip_summed = CHECKSUM_NONE;
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/* Adjust IP TTL */
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niph->ttl = dst_metric(nskb->dst, RTAX_HOPLIMIT);
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/* "Never happens" */
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if (nskb->len > dst_mtu(nskb->dst))
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goto free_nskb;
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@ -163,11 +140,6 @@ reject_tg(struct sk_buff *skb, const struct net_device *in,
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{
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const struct ipt_reject_info *reject = targinfo;
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/* Our naive response construction doesn't deal with IP
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options, and probably shouldn't try. */
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if (ip_hdrlen(skb) != sizeof(struct iphdr))
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return NF_DROP;
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/* WARNING: This code causes reentry within iptables.
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This means that the iptables jump stack is now crap. We
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must return an absolute verdict. --RR */
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