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 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 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 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 skb_mac_header_rebuild(skb); 65 skb_reset_transport_header(skb); 66 return 0; 67 } 68 69 NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, 70 dev_net(skb->dev), NULL, skb, skb->dev, NULL, 71 xfrm4_rcv_encap_finish); 72 return 0; 73 } 74 75 /* If it's a keepalive packet, then just eat it. 76 * If it's an encapsulated packet, then pass it to the 77 * IPsec xfrm input. 78 * Returns 0 if skb passed to xfrm or was dropped. 79 * Returns >0 if skb should be passed to UDP. 80 * Returns <0 if skb should be resubmitted (-ret is protocol) 81 */ 82 int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb) 83 { 84 struct udp_sock *up = udp_sk(sk); 85 struct udphdr *uh; 86 struct iphdr *iph; 87 int iphlen, len; 88 89 __u8 *udpdata; 90 __be32 *udpdata32; 91 __u16 encap_type = up->encap_type; 92 93 /* if this is not encapsulated socket, then just return now */ 94 if (!encap_type) 95 return 1; 96 97 /* If this is a paged skb, make sure we pull up 98 * whatever data we need to look at. */ 99 len = skb->len - sizeof(struct udphdr); 100 if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8))) 101 return 1; 102 103 /* Now we can get the pointers */ 104 uh = udp_hdr(skb); 105 udpdata = (__u8 *)uh + sizeof(struct udphdr); 106 udpdata32 = (__be32 *)udpdata; 107 108 switch (encap_type) { 109 default: 110 case UDP_ENCAP_ESPINUDP: 111 /* Check if this is a keepalive packet. If so, eat it. */ 112 if (len == 1 && udpdata[0] == 0xff) { 113 goto drop; 114 } else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) { 115 /* ESP Packet without Non-ESP header */ 116 len = sizeof(struct udphdr); 117 } else 118 /* Must be an IKE packet.. pass it through */ 119 return 1; 120 break; 121 case UDP_ENCAP_ESPINUDP_NON_IKE: 122 /* Check if this is a keepalive packet. If so, eat it. */ 123 if (len == 1 && udpdata[0] == 0xff) { 124 goto drop; 125 } else if (len > 2 * sizeof(u32) + sizeof(struct ip_esp_hdr) && 126 udpdata32[0] == 0 && udpdata32[1] == 0) { 127 128 /* ESP Packet with Non-IKE marker */ 129 len = sizeof(struct udphdr) + 2 * sizeof(u32); 130 } else 131 /* Must be an IKE packet.. pass it through */ 132 return 1; 133 break; 134 } 135 136 /* At this point we are sure that this is an ESPinUDP packet, 137 * so we need to remove 'len' bytes from the packet (the UDP 138 * header and optional ESP marker bytes) and then modify the 139 * protocol to ESP, and then call into the transform receiver. 140 */ 141 if (skb_unclone(skb, GFP_ATOMIC)) 142 goto drop; 143 144 /* Now we can update and verify the packet length... */ 145 iph = ip_hdr(skb); 146 iphlen = iph->ihl << 2; 147 iph->tot_len = htons(ntohs(iph->tot_len) - len); 148 if (skb->len < iphlen + len) { 149 /* packet is too small!?! */ 150 goto drop; 151 } 152 153 /* pull the data buffer up to the ESP header and set the 154 * transport header to point to ESP. Keep UDP on the stack 155 * for later. 156 */ 157 __skb_pull(skb, len); 158 skb_reset_transport_header(skb); 159 160 /* process ESP */ 161 return xfrm4_rcv_encap(skb, IPPROTO_ESP, 0, encap_type); 162 163 drop: 164 kfree_skb(skb); 165 return 0; 166 } 167 168 int xfrm4_rcv(struct sk_buff *skb) 169 { 170 return xfrm4_rcv_spi(skb, ip_hdr(skb)->protocol, 0); 171 } 172 EXPORT_SYMBOL(xfrm4_rcv); 173