net/ipv4/xfrm4_input.c

   1 /*
   2  * xfrm4_input.c
   3  *
   4  * Changes:
   5  *      YOSHIFUJI Hideaki @USAGI
   6  *              Split up af-specific portion
   7  *      Derek Atkins <derek@ihtfp.com>
   8  *              Add Encapsulation support
   9  *
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/string.h>
  14 #include <linux/netfilter.h>
  15 #include <linux/netfilter_ipv4.h>
  16 #include <net/ip.h>
  17 #include <net/xfrm.h>
  18
  19 static int xfrm4_parse_spi(struct sk_buff *skb, u8 nexthdr, __be32 *spi, __be32 *seq)
  20 {
  21         switch (nexthdr) {
  22         case IPPROTO_IPIP:
  23         case IPPROTO_IPV6:
  24                 *spi = ip_hdr(skb)->saddr;
  25                 *seq = 0;
  26                 return 0;
  27         }
  28
  29         return xfrm_parse_spi(skb, nexthdr, spi, seq);
  30 }
  31
  32 #ifdef CONFIG_NETFILTER
  33 static inline int xfrm4_rcv_encap_finish(struct sk_buff *skb)
  34 {
  35         if (skb->dst == NULL) {
  36                 const struct iphdr *iph = ip_hdr(skb);
  37
  38                 if (ip_route_input(skb, iph->daddr, iph->saddr, iph->tos,
  39                                    skb->dev))
  40                         goto drop;
  41         }
  42         return dst_input(skb);
  43 drop:
  44         kfree_skb(skb);
  45         return NET_RX_DROP;
  46 }
  47 #endif
  48
  49 static int xfrm4_rcv_encap(struct sk_buff *skb, __u16 encap_type)
  50 {
  51         __be32 spi, seq;
  52         struct xfrm_state *xfrm_vec[XFRM_MAX_DEPTH];
  53         struct xfrm_state *x;
  54         int xfrm_nr = 0;
  55         int decaps = 0;
  56         int err = xfrm4_parse_spi(skb, ip_hdr(skb)->protocol, &spi, &seq);
  57         unsigned int nhoff = offsetof(struct iphdr, protocol);
  58
  59         if (err != 0)
  60                 goto drop;
  61
  62         do {
  63                 const struct iphdr *iph = ip_hdr(skb);
  64                 int nexthdr;
  65
  66                 if (xfrm_nr == XFRM_MAX_DEPTH)
  67                         goto drop;
  68
  69                 x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, spi,
  70                                 iph->protocol != IPPROTO_IPV6 ? iph->protocol : IPPROTO_IPIP, AF_INET);
  71                 if (x == NULL)
  72                         goto drop;
  73
  74                 spin_lock(&x->lock);
  75                 if (unlikely(x->km.state != XFRM_STATE_VALID))
  76                         goto drop_unlock;
  77
  78                 if ((x->encap ? x->encap->encap_type : 0) != encap_type)
  79                         goto drop_unlock;
  80
  81                 if (x->props.replay_window && xfrm_replay_check(x, seq))
  82                         goto drop_unlock;
  83
  84                 if (xfrm_state_check_expire(x))
  85                         goto drop_unlock;
  86
  87                 nexthdr = x->type->input(x, skb);
  88                 if (nexthdr <= 0)
  89                         goto drop_unlock;
  90
  91                 skb_network_header(skb)[nhoff] = nexthdr;
  92
  93                 /* only the first xfrm gets the encap type */
  94                 encap_type = 0;
  95
  96                 if (x->props.replay_window)
  97                         xfrm_replay_advance(x, seq);
  98
  99                 x->curlft.bytes += skb->len;
 100                 x->curlft.packets++;
 101
 102                 spin_unlock(&x->lock);
 103
 104                 xfrm_vec[xfrm_nr++] = x;
 105
 106                 if (x->mode->input(x, skb))
 107                         goto drop;
 108
 109                 if (x->props.mode == XFRM_MODE_TUNNEL) {
 110                         decaps = 1;
 111                         break;
 112                 }
 113
 114                 err = xfrm_parse_spi(skb, ip_hdr(skb)->protocol, &spi, &seq);
 115                 if (err < 0)
 116                         goto drop;
 117         } while (!err);
 118
 119         /* Allocate new secpath or COW existing one. */
 120
 121         if (!skb->sp || atomic_read(&skb->sp->refcnt) != 1) {
 122                 struct sec_path *sp;
 123                 sp = secpath_dup(skb->sp);
 124                 if (!sp)
 125                         goto drop;
 126                 if (skb->sp)
 127                         secpath_put(skb->sp);
 128                 skb->sp = sp;
 129         }
 130         if (xfrm_nr + skb->sp->len > XFRM_MAX_DEPTH)
 131                 goto drop;
 132
 133         memcpy(skb->sp->xvec + skb->sp->len, xfrm_vec,
 134                xfrm_nr * sizeof(xfrm_vec[0]));
 135         skb->sp->len += xfrm_nr;
 136
 137         nf_reset(skb);
 138
 139         if (decaps) {
 140                 dst_release(skb->dst);
 141                 skb->dst = NULL;
 142                 netif_rx(skb);
 143                 return 0;
 144         } else {
 145 #ifdef CONFIG_NETFILTER
 146                 __skb_push(skb, skb->data - skb_network_header(skb));
 147                 ip_hdr(skb)->tot_len = htons(skb->len);
 148                 ip_send_check(ip_hdr(skb));
 149
 150                 NF_HOOK(PF_INET, NF_IP_PRE_ROUTING, skb, skb->dev, NULL,
 151                         xfrm4_rcv_encap_finish);
 152                 return 0;
 153 #else
 154                 return -ip_hdr(skb)->protocol;
 155 #endif
 156         }
 157
 158 drop_unlock:
 159         spin_unlock(&x->lock);
 160         xfrm_state_put(x);
 161 drop:
 162         while (--xfrm_nr >= 0)
 163                 xfrm_state_put(xfrm_vec[xfrm_nr]);
 164
 165         kfree_skb(skb);
 166         return 0;
 167 }
 168
 169 /* If it's a keepalive packet, then just eat it.
 170  * If it's an encapsulated packet, then pass it to the
 171  * IPsec xfrm input.
 172  * Returns 0 if skb passed to xfrm or was dropped.
 173  * Returns >0 if skb should be passed to UDP.
 174  * Returns <0 if skb should be resubmitted (-ret is protocol)
 175  */
 176 int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb)
 177 {
 178         struct udp_sock *up = udp_sk(sk);
 179         struct udphdr *uh;
 180         struct iphdr *iph;
 181         int iphlen, len;
 182         int ret;
 183
 184         __u8 *udpdata;
 185         __be32 *udpdata32;
 186         __u16 encap_type = up->encap_type;
 187
 188         /* if this is not encapsulated socket, then just return now */
 189         if (!encap_type)
 190                 return 1;
 191
 192         /* If this is a paged skb, make sure we pull up
 193          * whatever data we need to look at. */
 194         len = skb->len - sizeof(struct udphdr);
 195         if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8)))
 196                 return 1;
 197
 198         /* Now we can get the pointers */
 199         uh = udp_hdr(skb);
 200         udpdata = (__u8 *)uh + sizeof(struct udphdr);
 201         udpdata32 = (__be32 *)udpdata;
 202
 203         switch (encap_type) {
 204         default:
 205         case UDP_ENCAP_ESPINUDP:
 206                 /* Check if this is a keepalive packet.  If so, eat it. */
 207                 if (len == 1 && udpdata[0] == 0xff) {
 208                         goto drop;
 209                 } else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) {
 210                         /* ESP Packet without Non-ESP header */
 211                         len = sizeof(struct udphdr);
 212                 } else
 213                         /* Must be an IKE packet.. pass it through */
 214                         return 1;
 215                 break;
 216         case UDP_ENCAP_ESPINUDP_NON_IKE:
 217                 /* Check if this is a keepalive packet.  If so, eat it. */
 218                 if (len == 1 && udpdata[0] == 0xff) {
 219                         goto drop;
 220                 } else if (len > 2 * sizeof(u32) + sizeof(struct ip_esp_hdr) &&
 221                            udpdata32[0] == 0 && udpdata32[1] == 0) {
 222
 223                         /* ESP Packet with Non-IKE marker */
 224                         len = sizeof(struct udphdr) + 2 * sizeof(u32);
 225                 } else
 226                         /* Must be an IKE packet.. pass it through */
 227                         return 1;
 228                 break;
 229         }
 230
 231         /* At this point we are sure that this is an ESPinUDP packet,
 232          * so we need to remove 'len' bytes from the packet (the UDP
 233          * header and optional ESP marker bytes) and then modify the
 234          * protocol to ESP, and then call into the transform receiver.
 235          */
 236         if (skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 237                 goto drop;
 238
 239         /* Now we can update and verify the packet length... */
 240         iph = ip_hdr(skb);
 241         iphlen = iph->ihl << 2;
 242         iph->tot_len = htons(ntohs(iph->tot_len) - len);
 243         if (skb->len < iphlen + len) {
 244                 /* packet is too small!?! */
 245                 goto drop;
 246         }
 247
 248         /* pull the data buffer up to the ESP header and set the
 249          * transport header to point to ESP.  Keep UDP on the stack
 250          * for later.
 251          */
 252         __skb_pull(skb, len);
 253         skb_reset_transport_header(skb);
 254
 255         /* modify the protocol (it's ESP!) */
 256         iph->protocol = IPPROTO_ESP;
 257
 258         /* process ESP */
 259         ret = xfrm4_rcv_encap(skb, encap_type);
 260         return ret;
 261
 262 drop:
 263         kfree_skb(skb);
 264         return 0;
 265 }
 266
 267 int xfrm4_rcv(struct sk_buff *skb)
 268 {
 269         return xfrm4_rcv_encap(skb, 0);
 270 }
 271
 272 EXPORT_SYMBOL(xfrm4_rcv);