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
21int xfrm4_extract_input(struct xfrm_state *x, struct sk_buff *skb)
22{
23 return xfrm4_extract_header(skb);
24}
25
26static int xfrm4_rcv_encap_finish2(struct net *net, struct sock *sk,
27 struct sk_buff *skb)
28{
29 return dst_input(skb);
30}
31
32static inline int xfrm4_rcv_encap_finish(struct net *net, struct sock *sk,
33 struct sk_buff *skb)
34{
35 if (!skb_dst(skb)) {
36 const struct iphdr *iph = ip_hdr(skb);
37
38 if (ip_route_input_noref(skb, iph->daddr, iph->saddr,
39 iph->tos, skb->dev))
40 goto drop;
41 }
42
43 if (xfrm_trans_queue(skb, xfrm4_rcv_encap_finish2))
44 goto drop;
45
46 return 0;
47drop:
48 kfree_skb(skb);
49 return NET_RX_DROP;
50}
51
52int xfrm4_transport_finish(struct sk_buff *skb, int async)
53{
54 struct xfrm_offload *xo = xfrm_offload(skb);
55 struct iphdr *iph = ip_hdr(skb);
56
57 iph->protocol = XFRM_MODE_SKB_CB(skb)->protocol;
58
59#ifndef CONFIG_NETFILTER
60 if (!async)
61 return -iph->protocol;
62#endif
63
64 __skb_push(skb, skb->data - skb_network_header(skb));
65 iph->tot_len = htons(skb->len);
66 ip_send_check(iph);
67
68 if (xo && (xo->flags & XFRM_GRO)) {
69 skb_mac_header_rebuild(skb);
70 skb_reset_transport_header(skb);
71 return 0;
72 }
73
74 NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING,
75 dev_net(skb->dev), NULL, skb, skb->dev, NULL,
76 xfrm4_rcv_encap_finish);
77 return 0;
78}
79
80/* If it's a keepalive packet, then just eat it.
81 * If it's an encapsulated packet, then pass it to the
82 * IPsec xfrm input.
83 * Returns 0 if skb passed to xfrm or was dropped.
84 * Returns >0 if skb should be passed to UDP.
85 * Returns <0 if skb should be resubmitted (-ret is protocol)
86 */
87int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb)
88{
89 struct udp_sock *up = udp_sk(sk);
90 struct udphdr *uh;
91 struct iphdr *iph;
92 int iphlen, len;
93
94 __u8 *udpdata;
95 __be32 *udpdata32;
96 __u16 encap_type = up->encap_type;
97
98 /* if this is not encapsulated socket, then just return now */
99 if (!encap_type)
100 return 1;
101
102 /* If this is a paged skb, make sure we pull up
103 * whatever data we need to look at. */
104 len = skb->len - sizeof(struct udphdr);
105 if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8)))
106 return 1;
107
108 /* Now we can get the pointers */
109 uh = udp_hdr(skb);
110 udpdata = (__u8 *)uh + sizeof(struct udphdr);
111 udpdata32 = (__be32 *)udpdata;
112
113 switch (encap_type) {
114 default:
115 case UDP_ENCAP_ESPINUDP:
116 /* Check if this is a keepalive packet. If so, eat it. */
117 if (len == 1 && udpdata[0] == 0xff) {
118 goto drop;
119 } else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) {
120 /* ESP Packet without Non-ESP header */
121 len = sizeof(struct udphdr);
122 } else
123 /* Must be an IKE packet.. pass it through */
124 return 1;
125 break;
126 case UDP_ENCAP_ESPINUDP_NON_IKE:
127 /* Check if this is a keepalive packet. If so, eat it. */
128 if (len == 1 && udpdata[0] == 0xff) {
129 goto drop;
130 } else if (len > 2 * sizeof(u32) + sizeof(struct ip_esp_hdr) &&
131 udpdata32[0] == 0 && udpdata32[1] == 0) {
132
133 /* ESP Packet with Non-IKE marker */
134 len = sizeof(struct udphdr) + 2 * sizeof(u32);
135 } else
136 /* Must be an IKE packet.. pass it through */
137 return 1;
138 break;
139 }
140
141 /* At this point we are sure that this is an ESPinUDP packet,
142 * so we need to remove 'len' bytes from the packet (the UDP
143 * header and optional ESP marker bytes) and then modify the
144 * protocol to ESP, and then call into the transform receiver.
145 */
146 if (skb_unclone(skb, GFP_ATOMIC))
147 goto drop;
148
149 /* Now we can update and verify the packet length... */
150 iph = ip_hdr(skb);
151 iphlen = iph->ihl << 2;
152 iph->tot_len = htons(ntohs(iph->tot_len) - len);
153 if (skb->len < iphlen + len) {
154 /* packet is too small!?! */
155 goto drop;
156 }
157
158 /* pull the data buffer up to the ESP header and set the
159 * transport header to point to ESP. Keep UDP on the stack
160 * for later.
161 */
162 __skb_pull(skb, len);
163 skb_reset_transport_header(skb);
164
165 /* process ESP */
166 return xfrm4_rcv_encap(skb, IPPROTO_ESP, 0, encap_type);
167
168drop:
169 kfree_skb(skb);
170 return 0;
171}
172
173int xfrm4_rcv(struct sk_buff *skb)
174{
175 return xfrm4_rcv_spi(skb, ip_hdr(skb)->protocol, 0);
176}
177EXPORT_SYMBOL(xfrm4_rcv);
178