net/ipv4/xfrm4_input.c

   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);