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