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root/net/ipv4/ah4.c

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DEFINITIONS

This source file includes following definitions.
  1. ip_clear_mutable_options
  2. ah_output
  3. ah_input
  4. ah4_err
  5. ah_init_state
  6. ah_destroy
  7. ah4_init
  8. ah4_fini

#include <linux/err.h>
#include <linux/module.h>
#include <net/ip.h>
#include <net/xfrm.h>
#include <net/ah.h>
#include <linux/crypto.h>
#include <linux/pfkeyv2.h>
#include <linux/spinlock.h>
#include <net/icmp.h>
#include <net/protocol.h>


/* Clear mutable options and find final destination to substitute
 * into IP header for icv calculation. Options are already checked
 * for validity, so paranoia is not required. */

static int ip_clear_mutable_options(struct iphdr *iph, __be32 *daddr)
{
        unsigned char * optptr = (unsigned char*)(iph+1);
        int  l = iph->ihl*4 - sizeof(struct iphdr);
        int  optlen;

        while (l > 0) {
                switch (*optptr) {
                case IPOPT_END:
                        return 0;
                case IPOPT_NOOP:
                        l--;
                        optptr++;
                        continue;
                }
                optlen = optptr[1];
                if (optlen<2 || optlen>l)
                        return -EINVAL;
                switch (*optptr) {
                case IPOPT_SEC:
                case 0x85:      /* Some "Extended Security" crap. */
                case IPOPT_CIPSO:
                case IPOPT_RA:
                case 0x80|21:   /* RFC1770 */
                        break;
                case IPOPT_LSRR:
                case IPOPT_SSRR:
                        if (optlen < 6)
                                return -EINVAL;
                        memcpy(daddr, optptr+optlen-4, 4);
                        /* Fall through */
                default:
                        memset(optptr, 0, optlen);
                }
                l -= optlen;
                optptr += optlen;
        }
        return 0;
}

static int ah_output(struct xfrm_state *x, struct sk_buff *skb)
{
        int err;
        struct iphdr *iph, *top_iph;
        struct ip_auth_hdr *ah;
        struct ah_data *ahp;
        union {
                struct iphdr    iph;
                char            buf[60];
        } tmp_iph;

        skb_push(skb, -skb_network_offset(skb));
        top_iph = ip_hdr(skb);
        iph = &tmp_iph.iph;

        iph->tos = top_iph->tos;
        iph->ttl = top_iph->ttl;
        iph->frag_off = top_iph->frag_off;

        if (top_iph->ihl != 5) {
                iph->daddr = top_iph->daddr;
                memcpy(iph+1, top_iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
                err = ip_clear_mutable_options(top_iph, &top_iph->daddr);
                if (err)
                        goto error;
        }

        ah = ip_auth_hdr(skb);
        ah->nexthdr = *skb_mac_header(skb);
        *skb_mac_header(skb) = IPPROTO_AH;

        top_iph->tos = 0;
        top_iph->tot_len = htons(skb->len);
        top_iph->frag_off = 0;
        top_iph->ttl = 0;
        top_iph->check = 0;

        ahp = x->data;
        ah->hdrlen  = (XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;

        ah->reserved = 0;
        ah->spi = x->id.spi;
        ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output);

        spin_lock_bh(&x->lock);
        err = ah_mac_digest(ahp, skb, ah->auth_data);
        memcpy(ah->auth_data, ahp->work_icv, ahp->icv_trunc_len);
        spin_unlock_bh(&x->lock);

        if (err)
                goto error;

        top_iph->tos = iph->tos;
        top_iph->ttl = iph->ttl;
        top_iph->frag_off = iph->frag_off;
        if (top_iph->ihl != 5) {
                top_iph->daddr = iph->daddr;
                memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
        }

        err = 0;

error:
        return err;
}

static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
{
        int ah_hlen;
        int ihl;
        int nexthdr;
        int err = -EINVAL;
        struct iphdr *iph;
        struct ip_auth_hdr *ah;
        struct ah_data *ahp;
        char work_buf[60];

        if (!pskb_may_pull(skb, sizeof(*ah)))
                goto out;

        ah = (struct ip_auth_hdr *)skb->data;
        ahp = x->data;
        nexthdr = ah->nexthdr;
        ah_hlen = (ah->hdrlen + 2) << 2;

        if (ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_full_len) &&
            ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len))
                goto out;

        if (!pskb_may_pull(skb, ah_hlen))
                goto out;

        /* We are going to _remove_ AH header to keep sockets happy,
         * so... Later this can change. */
        if (skb_cloned(skb) &&
            pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
                goto out;

        skb->ip_summed = CHECKSUM_NONE;

        ah = (struct ip_auth_hdr *)skb->data;
        iph = ip_hdr(skb);

        ihl = skb->data - skb_network_header(skb);
        memcpy(work_buf, iph, ihl);

        iph->ttl = 0;
        iph->tos = 0;
        iph->frag_off = 0;
        iph->check = 0;
        if (ihl > sizeof(*iph)) {
                __be32 dummy;
                if (ip_clear_mutable_options(iph, &dummy))
                        goto out;
        }

        spin_lock(&x->lock);
        {
                u8 auth_data[MAX_AH_AUTH_LEN];

                memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
                skb_push(skb, ihl);
                err = ah_mac_digest(ahp, skb, ah->auth_data);
                if (err)
                        goto unlock;
                if (memcmp(ahp->work_icv, auth_data, ahp->icv_trunc_len))
                        err = -EBADMSG;
        }
unlock:
        spin_unlock(&x->lock);

        if (err)
                goto out;

        skb->network_header += ah_hlen;
        memcpy(skb_network_header(skb), work_buf, ihl);
        skb->transport_header = skb->network_header;
        __skb_pull(skb, ah_hlen + ihl);

        return nexthdr;

out:
        return err;
}

static void ah4_err(struct sk_buff *skb, u32 info)
{
        struct iphdr *iph = (struct iphdr*)skb->data;
        struct ip_auth_hdr *ah = (struct ip_auth_hdr*)(skb->data+(iph->ihl<<2));
        struct xfrm_state *x;

        if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
            icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
                return;

        x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET);
        if (!x)
                return;
        printk(KERN_DEBUG "pmtu discovery on SA AH/%08x/%08x\n",
               ntohl(ah->spi), ntohl(iph->daddr));
        xfrm_state_put(x);
}

static int ah_init_state(struct xfrm_state *x)
{
        struct ah_data *ahp = NULL;
        struct xfrm_algo_desc *aalg_desc;
        struct crypto_hash *tfm;

        if (!x->aalg)
                goto error;

        if (x->encap)
                goto error;

        ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
        if (ahp == NULL)
                return -ENOMEM;

        tfm = crypto_alloc_hash(x->aalg->alg_name, 0, CRYPTO_ALG_ASYNC);
        if (IS_ERR(tfm))
                goto error;

        ahp->tfm = tfm;
        if (crypto_hash_setkey(tfm, x->aalg->alg_key,
                               (x->aalg->alg_key_len + 7) / 8))
                goto error;

        /*
         * Lookup the algorithm description maintained by xfrm_algo,
         * verify crypto transform properties, and store information
         * we need for AH processing.  This lookup cannot fail here
         * after a successful crypto_alloc_hash().
         */
        aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
        BUG_ON(!aalg_desc);

        if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
            crypto_hash_digestsize(tfm)) {
                printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
                       x->aalg->alg_name, crypto_hash_digestsize(tfm),
                       aalg_desc->uinfo.auth.icv_fullbits/8);
                goto error;
        }

        ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
        ahp->icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;

        BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);

        ahp->work_icv = kmalloc(ahp->icv_full_len, GFP_KERNEL);
        if (!ahp->work_icv)
                goto error;

        x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
                                          ahp->icv_trunc_len);
        if (x->props.mode == XFRM_MODE_TUNNEL)
                x->props.header_len += sizeof(struct iphdr);
        x->data = ahp;

        return 0;

error:
        if (ahp) {
                kfree(ahp->work_icv);
                crypto_free_hash(ahp->tfm);
                kfree(ahp);
        }
        return -EINVAL;
}

static void ah_destroy(struct xfrm_state *x)
{
        struct ah_data *ahp = x->data;

        if (!ahp)
                return;

        kfree(ahp->work_icv);
        ahp->work_icv = NULL;
        crypto_free_hash(ahp->tfm);
        ahp->tfm = NULL;
        kfree(ahp);
}


static const struct xfrm_type ah_type =
{
        .description    = "AH4",
        .owner          = THIS_MODULE,
        .proto          = IPPROTO_AH,
        .flags          = XFRM_TYPE_REPLAY_PROT,
        .init_state     = ah_init_state,
        .destructor     = ah_destroy,
        .input          = ah_input,
        .output         = ah_output
};

static struct net_protocol ah4_protocol = {
        .handler        =       xfrm4_rcv,
        .err_handler    =       ah4_err,
        .no_policy      =       1,
};

static int __init ah4_init(void)
{
        if (xfrm_register_type(&ah_type, AF_INET) < 0) {
                printk(KERN_INFO "ip ah init: can't add xfrm type\n");
                return -EAGAIN;
        }
        if (inet_add_protocol(&ah4_protocol, IPPROTO_AH) < 0) {
                printk(KERN_INFO "ip ah init: can't add protocol\n");
                xfrm_unregister_type(&ah_type, AF_INET);
                return -EAGAIN;
        }
        return 0;
}

static void __exit ah4_fini(void)
{
        if (inet_del_protocol(&ah4_protocol, IPPROTO_AH) < 0)
                printk(KERN_INFO "ip ah close: can't remove protocol\n");
        if (xfrm_unregister_type(&ah_type, AF_INET) < 0)
                printk(KERN_INFO "ip ah close: can't remove xfrm type\n");
}

module_init(ah4_init);
module_exit(ah4_fini);
MODULE_LICENSE("GPL");
MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_AH);

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