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
  21static int xfrm4_rcv_encap_finish2(struct net *net, struct sock *sk,
  22                                   struct sk_buff *skb)
  23{
  24        return dst_input(skb);
  25}
  26
  27static 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;
  42drop:
  43        kfree_skb(skb);
  44        return NET_RX_DROP;
  45}
  46
  47int 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 */
  82int 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
 163drop:
 164        kfree_skb(skb);
 165        return 0;
 166}
 167
 168int xfrm4_rcv(struct sk_buff *skb)
 169{
 170        return xfrm4_rcv_spi(skb, ip_hdr(skb)->protocol, 0);
 171}
 172EXPORT_SYMBOL(xfrm4_rcv);
 173