1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * xfrm4_input.c
4 *
5 * Changes:
6 * YOSHIFUJI Hideaki @USAGI
7 * Split up af-specific portion
8 * Derek Atkins <derek@ihtfp.com>
9 * Add Encapsulation support
10 *
11 */
12
13 #include <linux/slab.h>
14 #include <linux/module.h>
15 #include <linux/string.h>
16 #include <linux/netfilter.h>
17 #include <linux/netfilter_ipv4.h>
18 #include <net/ip.h>
19 #include <net/xfrm.h>
20
xfrm4_rcv_encap_finish2(struct net * net,struct sock * sk,struct sk_buff * skb)21 static int xfrm4_rcv_encap_finish2(struct net *net, struct sock *sk,
22 struct sk_buff *skb)
23 {
24 return dst_input(skb);
25 }
26
xfrm4_rcv_encap_finish(struct net * net,struct sock * sk,struct sk_buff * skb)27 static inline int xfrm4_rcv_encap_finish(struct net *net, struct sock *sk,
28 struct sk_buff *skb)
29 {
30 if (!skb_dst(skb)) {
31 const struct iphdr *iph = ip_hdr(skb);
32
33 if (ip_route_input_noref(skb, iph->daddr, iph->saddr,
34 iph->tos, skb->dev))
35 goto drop;
36 }
37
38 if (xfrm_trans_queue(skb, xfrm4_rcv_encap_finish2))
39 goto drop;
40
41 return 0;
42 drop:
43 kfree_skb(skb);
44 return NET_RX_DROP;
45 }
46
xfrm4_transport_finish(struct sk_buff * skb,int async)47 int xfrm4_transport_finish(struct sk_buff *skb, int async)
48 {
49 struct xfrm_offload *xo = xfrm_offload(skb);
50 struct iphdr *iph = ip_hdr(skb);
51
52 iph->protocol = XFRM_MODE_SKB_CB(skb)->protocol;
53
54 #ifndef CONFIG_NETFILTER
55 if (!async)
56 return -iph->protocol;
57 #endif
58
59 __skb_push(skb, skb->data - skb_network_header(skb));
60 iph->tot_len = htons(skb->len);
61 ip_send_check(iph);
62
63 if (xo && (xo->flags & XFRM_GRO)) {
64 /* The full l2 header needs to be preserved so that re-injecting the packet at l2
65 * works correctly in the presence of vlan tags.
66 */
67 skb_mac_header_rebuild_full(skb, xo->orig_mac_len);
68 skb_reset_network_header(skb);
69 skb_reset_transport_header(skb);
70 return 0;
71 }
72
73 NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING,
74 dev_net(skb->dev), NULL, skb, skb->dev, NULL,
75 xfrm4_rcv_encap_finish);
76 return 0;
77 }
78
79 /* If it's a keepalive packet, then just eat it.
80 * If it's an encapsulated packet, then pass it to the
81 * IPsec xfrm input.
82 * Returns 0 if skb passed to xfrm or was dropped.
83 * Returns >0 if skb should be passed to UDP.
84 * Returns <0 if skb should be resubmitted (-ret is protocol)
85 */
xfrm4_udp_encap_rcv(struct sock * sk,struct sk_buff * skb)86 int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb)
87 {
88 struct udp_sock *up = udp_sk(sk);
89 struct udphdr *uh;
90 struct iphdr *iph;
91 int iphlen, len;
92 __u8 *udpdata;
93 __be32 *udpdata32;
94 u16 encap_type;
95
96 encap_type = READ_ONCE(up->encap_type);
97 /* if this is not encapsulated socket, then just return now */
98 if (!encap_type)
99 return 1;
100
101 /* If this is a paged skb, make sure we pull up
102 * whatever data we need to look at. */
103 len = skb->len - sizeof(struct udphdr);
104 if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8)))
105 return 1;
106
107 /* Now we can get the pointers */
108 uh = udp_hdr(skb);
109 udpdata = (__u8 *)uh + sizeof(struct udphdr);
110 udpdata32 = (__be32 *)udpdata;
111
112 switch (encap_type) {
113 default:
114 case UDP_ENCAP_ESPINUDP:
115 /* Check if this is a keepalive packet. If so, eat it. */
116 if (len == 1 && udpdata[0] == 0xff) {
117 goto drop;
118 } else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) {
119 /* ESP Packet without Non-ESP header */
120 len = sizeof(struct udphdr);
121 } else
122 /* Must be an IKE packet.. pass it through */
123 return 1;
124 break;
125 case UDP_ENCAP_ESPINUDP_NON_IKE:
126 /* Check if this is a keepalive packet. If so, eat it. */
127 if (len == 1 && udpdata[0] == 0xff) {
128 goto drop;
129 } else if (len > 2 * sizeof(u32) + sizeof(struct ip_esp_hdr) &&
130 udpdata32[0] == 0 && udpdata32[1] == 0) {
131
132 /* ESP Packet with Non-IKE marker */
133 len = sizeof(struct udphdr) + 2 * sizeof(u32);
134 } else
135 /* Must be an IKE packet.. pass it through */
136 return 1;
137 break;
138 }
139
140 /* At this point we are sure that this is an ESPinUDP packet,
141 * so we need to remove 'len' bytes from the packet (the UDP
142 * header and optional ESP marker bytes) and then modify the
143 * protocol to ESP, and then call into the transform receiver.
144 */
145 if (skb_unclone(skb, GFP_ATOMIC))
146 goto drop;
147
148 /* Now we can update and verify the packet length... */
149 iph = ip_hdr(skb);
150 iphlen = iph->ihl << 2;
151 iph->tot_len = htons(ntohs(iph->tot_len) - len);
152 if (skb->len < iphlen + len) {
153 /* packet is too small!?! */
154 goto drop;
155 }
156
157 /* pull the data buffer up to the ESP header and set the
158 * transport header to point to ESP. Keep UDP on the stack
159 * for later.
160 */
161 __skb_pull(skb, len);
162 skb_reset_transport_header(skb);
163
164 /* process ESP */
165 return xfrm4_rcv_encap(skb, IPPROTO_ESP, 0, encap_type);
166
167 drop:
168 kfree_skb(skb);
169 return 0;
170 }
171 EXPORT_SYMBOL(xfrm4_udp_encap_rcv);
172
xfrm4_rcv(struct sk_buff * skb)173 int xfrm4_rcv(struct sk_buff *skb)
174 {
175 return xfrm4_rcv_spi(skb, ip_hdr(skb)->protocol, 0);
176 }
177 EXPORT_SYMBOL(xfrm4_rcv);
178