LXR linux/net/ipv4/xfrm4

   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
  21int xfrm4_extract_input(struct xfrm_state *x, struct sk_buff *skb)
  22{
  23        return xfrm4_extract_header(skb);
  24}
  25
  26static inline int xfrm4_rcv_encap_finish(struct net *net, struct sock *sk,
  27                                         struct sk_buff *skb)
  28{
  29        if (!skb_dst(skb)) {
  30                const struct iphdr *iph = ip_hdr(skb);
  31
  32                if (ip_route_input_noref(skb, iph->daddr, iph->saddr,
  33                                         iph->tos, skb->dev))
  34                        goto drop;
  35        }
  36        return dst_input(skb);
  37drop:
  38        kfree_skb(skb);
  39        return NET_RX_DROP;
  40}
  41
  42int xfrm4_transport_finish(struct sk_buff *skb, int async)
  43{
  44        struct xfrm_offload *xo = xfrm_offload(skb);
  45        struct iphdr *iph = ip_hdr(skb);
  46
  47        iph->protocol = XFRM_MODE_SKB_CB(skb)->protocol;
  48
  49#ifndef CONFIG_NETFILTER
  50        if (!async)
  51                return -iph->protocol;
  52#endif
  53
  54        __skb_push(skb, skb->data - skb_network_header(skb));
  55        iph->tot_len = htons(skb->len);
  56        ip_send_check(iph);
  57
  58        if (xo && (xo->flags & XFRM_GRO)) {
  59                skb_mac_header_rebuild(skb);
  60                return 0;
  61        }
  62
  63        NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING,
  64                dev_net(skb->dev), NULL, skb, skb->dev, NULL,
  65                xfrm4_rcv_encap_finish);
  66        return 0;
  67}
  68
  69/* If it's a keepalive packet, then just eat it.
  70 * If it's an encapsulated packet, then pass it to the
  71 * IPsec xfrm input.
  72 * Returns 0 if skb passed to xfrm or was dropped.
  73 * Returns >0 if skb should be passed to UDP.
  74 * Returns <0 if skb should be resubmitted (-ret is protocol)
  75 */
  76int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb)
  77{
  78        struct udp_sock *up = udp_sk(sk);
  79        struct udphdr *uh;
  80        struct iphdr *iph;
  81        int iphlen, len;
  82
  83        __u8 *udpdata;
  84        __be32 *udpdata32;
  85        __u16 encap_type = up->encap_type;
  86
  87        /* if this is not encapsulated socket, then just return now */
  88        if (!encap_type)
  89                return 1;
  90
  91        /* If this is a paged skb, make sure we pull up
  92         * whatever data we need to look at. */
  93        len = skb->len - sizeof(struct udphdr);
  94        if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8)))
  95                return 1;
  96
  97        /* Now we can get the pointers */
  98        uh = udp_hdr(skb);
  99        udpdata = (__u8 *)uh + sizeof(struct udphdr);
 100        udpdata32 = (__be32 *)udpdata;
 101
 102        switch (encap_type) {
 103        default:
 104        case UDP_ENCAP_ESPINUDP:
 105                /* Check if this is a keepalive packet.  If so, eat it. */
 106                if (len == 1 && udpdata[0] == 0xff) {
 107                        goto drop;
 108                } else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) {
 109                        /* ESP Packet without Non-ESP header */
 110                        len = sizeof(struct udphdr);
 111                } else
 112                        /* Must be an IKE packet.. pass it through */
 113                        return 1;
 114                break;
 115        case UDP_ENCAP_ESPINUDP_NON_IKE:
 116                /* Check if this is a keepalive packet.  If so, eat it. */
 117                if (len == 1 && udpdata[0] == 0xff) {
 118                        goto drop;
 119                } else if (len > 2 * sizeof(u32) + sizeof(struct ip_esp_hdr) &&
 120                           udpdata32[0] == 0 && udpdata32[1] == 0) {
 121
 122                        /* ESP Packet with Non-IKE marker */
 123                        len = sizeof(struct udphdr) + 2 * sizeof(u32);
 124                } else
 125                        /* Must be an IKE packet.. pass it through */
 126                        return 1;
 127                break;
 128        }
 129
 130        /* At this point we are sure that this is an ESPinUDP packet,
 131         * so we need to remove 'len' bytes from the packet (the UDP
 132         * header and optional ESP marker bytes) and then modify the
 133         * protocol to ESP, and then call into the transform receiver.
 134         */
 135        if (skb_unclone(skb, GFP_ATOMIC))
 136                goto drop;
 137
 138        /* Now we can update and verify the packet length... */
 139        iph = ip_hdr(skb);
 140        iphlen = iph->ihl << 2;
 141        iph->tot_len = htons(ntohs(iph->tot_len) - len);
 142        if (skb->len < iphlen + len) {
 143                /* packet is too small!?! */
 144                goto drop;
 145        }
 146
 147        /* pull the data buffer up to the ESP header and set the
 148         * transport header to point to ESP.  Keep UDP on the stack
 149         * for later.
 150         */
 151        __skb_pull(skb, len);
 152        skb_reset_transport_header(skb);
 153
 154        /* process ESP */
 155        return xfrm4_rcv_encap(skb, IPPROTO_ESP, 0, encap_type);
 156
 157drop:
 158        kfree_skb(skb);
 159        return 0;
 160}
 161
 162int xfrm4_rcv(struct sk_buff *skb)
 163{
 164        return xfrm4_rcv_spi(skb, ip_hdr(skb)->protocol, 0);
 165}
 166EXPORT_SYMBOL(xfrm4_rcv);
 167