xref: /openbmc/linux/net/ipv4/xfrm4_input.c (revision 4a9771c0)
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