ah6.c

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/*
 * Copyright (C)2002 USAGI/WIDE Project
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Authors
 *
 *  Mitsuru KANDA @USAGI       : IPv6 Support
 *  Kazunori MIYAZAWA @USAGI   :
 *  Kunihiro Ishiguro <[email protected]>
 *
 *  This file is derived from net/ipv4/ah.c.
 */

#define pr_fmt(fmt) "IPv6: " fmt

#include <crypto/hash.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <net/ip.h>
#include <net/ah.h>
#include <linux/crypto.h>
#include <linux/pfkeyv2.h>
#include <linux/string.h>
#include <linux/scatterlist.h>
#include <net/ip6_route.h>
#include <net/icmp.h>
#include <net/ipv6.h>
#include <net/protocol.h>
#include <net/xfrm.h>

#define IPV6HDR_BASELEN 8

struct tmp_ext {
#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
        struct in6_addr saddr;
#endif
        struct in6_addr daddr;
        char hdrs[0];
};

struct ah_skb_cb {
    struct xfrm_skb_cb xfrm;
    void *tmp;
};

#define AH_SKB_CB(__skb) ((struct ah_skb_cb *)&((__skb)->cb[0]))

static void *ah_alloc_tmp(struct crypto_ahash *ahash, int nfrags,
              unsigned int size)
{
    unsigned int len;

    len = size + crypto_ahash_digestsize(ahash) +
          (crypto_ahash_alignmask(ahash) &
           ~(crypto_tfm_ctx_alignment() - 1));

    len = ALIGN(len, crypto_tfm_ctx_alignment());

    len += sizeof(struct ahash_request) + crypto_ahash_reqsize(ahash);
    len = ALIGN(len, __alignof__(struct scatterlist));

    len += sizeof(struct scatterlist) * nfrags;

    return kmalloc(len, GFP_ATOMIC);
}

static inline struct tmp_ext *ah_tmp_ext(void *base)
{
    return base + IPV6HDR_BASELEN;
}

static inline u8 *ah_tmp_auth(u8 *tmp, unsigned int offset)
{
    return tmp + offset;
}

static inline u8 *ah_tmp_icv(struct crypto_ahash *ahash, void *tmp,
                 unsigned int offset)
{
    return PTR_ALIGN((u8 *)tmp + offset, crypto_ahash_alignmask(ahash) + 1);
}

static inline struct ahash_request *ah_tmp_req(struct crypto_ahash *ahash,
                           u8 *icv)
{
    struct ahash_request *req;

    req = (void *)PTR_ALIGN(icv + crypto_ahash_digestsize(ahash),
                crypto_tfm_ctx_alignment());

    ahash_request_set_tfm(req, ahash);

    return req;
}

static inline struct scatterlist *ah_req_sg(struct crypto_ahash *ahash,
                         struct ahash_request *req)
{
    return (void *)ALIGN((unsigned long)(req + 1) +
                 crypto_ahash_reqsize(ahash),
                 __alignof__(struct scatterlist));
}

static bool zero_out_mutable_opts(struct ipv6_opt_hdr *opthdr)
{
    u8 *opt = (u8 *)opthdr;
    int len = ipv6_optlen(opthdr);
    int off = 0;
    int optlen = 0;

    off += 2;
    len -= 2;

    while (len > 0) {

        switch (opt[off]) {

        case IPV6_TLV_PAD1:
            optlen = 1;
            break;
        default:
            if (len < 2)
                goto bad;
            optlen = opt[off+1]+2;
            if (len < optlen)
                goto bad;
            if (opt[off] & 0x20)
                memset(&opt[off+2], 0, opt[off+1]);
            break;
        }

        off += optlen;
        len -= optlen;
    }
    if (len == 0)
        return true;

bad:
    return false;
}

#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)

static void ipv6_rearrange_destopt(struct ipv6hdr *iph, struct ipv6_opt_hdr *destopt)
{
    u8 *opt = (u8 *)destopt;
    int len = ipv6_optlen(destopt);
    int off = 0;
    int optlen = 0;

    off += 2;
    len -= 2;

    while (len > 0) {

        switch (opt[off]) {

        case IPV6_TLV_PAD1:
            optlen = 1;
            break;
        default:
            if (len < 2)
                goto bad;
            optlen = opt[off+1]+2;
            if (len < optlen)
                goto bad;

            /* Rearrange the source address in @iph and the
             * addresses in home address option for final source.
             * See 11.3.2 of RFC 3775 for details.
             */
            if (opt[off] == IPV6_TLV_HAO) {
                struct in6_addr final_addr;
                struct ipv6_destopt_hao *hao;

                hao = (struct ipv6_destopt_hao *)&opt[off];
                if (hao->length != sizeof(hao->addr)) {
                    net_warn_ratelimited("destopt hao: invalid header length: %u\n",
                                 hao->length);
                    goto bad;
                }
                final_addr = hao->addr;
                hao->addr = iph->saddr;
                iph->saddr = final_addr;
            }
            break;
        }

        off += optlen;
        len -= optlen;
    }
    /* Note: ok if len == 0 */
bad:
    return;
}
#else
static void ipv6_rearrange_destopt(struct ipv6hdr *iph, struct ipv6_opt_hdr *destopt) {}
#endif

static void ipv6_rearrange_rthdr(struct ipv6hdr *iph, struct ipv6_rt_hdr *rthdr)
{
    int segments, segments_left;
    struct in6_addr *addrs;
    struct in6_addr final_addr;

    segments_left = rthdr->segments_left;
    if (segments_left == 0)
        return;
    rthdr->segments_left = 0;

    /* The value of rthdr->hdrlen has been verified either by the system
     * call if it is locally generated, or by ipv6_rthdr_rcv() for incoming
     * packets.  So we can assume that it is even and that segments is
     * greater than or equal to segments_left.
     *
     * For the same reason we can assume that this option is of type 0.
     */
    segments = rthdr->hdrlen >> 1;

    addrs = ((struct rt0_hdr *)rthdr)->addr;
    final_addr = addrs[segments - 1];

    addrs += segments - segments_left;
    memmove(addrs + 1, addrs, (segments_left - 1) * sizeof(*addrs));

    addrs[0] = iph->daddr;
    iph->daddr = final_addr;
}

static int ipv6_clear_mutable_options(struct ipv6hdr *iph, int len, int dir)
{
    union {
        struct ipv6hdr *iph;
        struct ipv6_opt_hdr *opth;
        struct ipv6_rt_hdr *rth;
        char *raw;
    } exthdr = { .iph = iph };
    char *end = exthdr.raw + len;
    int nexthdr = iph->nexthdr;

    exthdr.iph++;

    while (exthdr.raw < end) {
        switch (nexthdr) {
        case NEXTHDR_DEST:
            if (dir == XFRM_POLICY_OUT)
                ipv6_rearrange_destopt(iph, exthdr.opth);
        case NEXTHDR_HOP:
            if (!zero_out_mutable_opts(exthdr.opth)) {
                LIMIT_NETDEBUG(
                    KERN_WARNING "overrun %sopts\n",
                    nexthdr == NEXTHDR_HOP ?
                        "hop" : "dest");
                return -EINVAL;
            }
            break;

        case NEXTHDR_ROUTING:
            ipv6_rearrange_rthdr(iph, exthdr.rth);
            break;

        default :
            return 0;
        }

        nexthdr = exthdr.opth->nexthdr;
        exthdr.raw += ipv6_optlen(exthdr.opth);
    }

    return 0;
}

static void ah6_output_done(struct crypto_async_request *base, int err)
{
    int extlen;
    u8 *iph_base;
    u8 *icv;
    struct sk_buff *skb = base->data;
    struct xfrm_state *x = skb_dst(skb)->xfrm;
    struct ah_data *ahp = x->data;
    struct ipv6hdr *top_iph = ipv6_hdr(skb);
    struct ip_auth_hdr *ah = ip_auth_hdr(skb);
    struct tmp_ext *iph_ext;

    extlen = skb_network_header_len(skb) - sizeof(struct ipv6hdr);
    if (extlen)
        extlen += sizeof(*iph_ext);

    iph_base = AH_SKB_CB(skb)->tmp;
    iph_ext = ah_tmp_ext(iph_base);
    icv = ah_tmp_icv(ahp->ahash, iph_ext, extlen);

    memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
    memcpy(top_iph, iph_base, IPV6HDR_BASELEN);

    if (extlen) {
#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
        memcpy(&top_iph->saddr, iph_ext, extlen);
#else
        memcpy(&top_iph->daddr, iph_ext, extlen);
#endif
    }

    kfree(AH_SKB_CB(skb)->tmp);
    xfrm_output_resume(skb, err);
}

static int ah6_output(struct xfrm_state *x, struct sk_buff *skb)
{
    int err;
    int nfrags;
    int extlen;
    u8 *iph_base;
    u8 *icv;
    u8 nexthdr;
    struct sk_buff *trailer;
    struct crypto_ahash *ahash;
    struct ahash_request *req;
    struct scatterlist *sg;
    struct ipv6hdr *top_iph;
    struct ip_auth_hdr *ah;
    struct ah_data *ahp;
    struct tmp_ext *iph_ext;

    ahp = x->data;
    ahash = ahp->ahash;

    if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
        goto out;
    nfrags = err;

    skb_push(skb, -skb_network_offset(skb));
    extlen = skb_network_header_len(skb) - sizeof(struct ipv6hdr);
    if (extlen)
        extlen += sizeof(*iph_ext);

    err = -ENOMEM;
    iph_base = ah_alloc_tmp(ahash, nfrags, IPV6HDR_BASELEN + extlen);
    if (!iph_base)
        goto out;

    iph_ext = ah_tmp_ext(iph_base);
    icv = ah_tmp_icv(ahash, iph_ext, extlen);
    req = ah_tmp_req(ahash, icv);
    sg = ah_req_sg(ahash, req);

    ah = ip_auth_hdr(skb);
    memset(ah->auth_data, 0, ahp->icv_trunc_len);

    top_iph = ipv6_hdr(skb);
    top_iph->payload_len = htons(skb->len - sizeof(*top_iph));

    nexthdr = *skb_mac_header(skb);
    *skb_mac_header(skb) = IPPROTO_AH;

    /* When there are no extension headers, we only need to save the first
     * 8 bytes of the base IP header.
     */
    memcpy(iph_base, top_iph, IPV6HDR_BASELEN);

    if (extlen) {
#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
        memcpy(iph_ext, &top_iph->saddr, extlen);
#else
        memcpy(iph_ext, &top_iph->daddr, extlen);
#endif
        err = ipv6_clear_mutable_options(top_iph,
                         extlen - sizeof(*iph_ext) +
                         sizeof(*top_iph),
                         XFRM_POLICY_OUT);
        if (err)
            goto out_free;
    }

    ah->nexthdr = nexthdr;

    top_iph->priority    = 0;
    top_iph->flow_lbl[0] = 0;
    top_iph->flow_lbl[1] = 0;
    top_iph->flow_lbl[2] = 0;
    top_iph->hop_limit   = 0;

    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.low);

    sg_init_table(sg, nfrags);
    skb_to_sgvec(skb, sg, 0, skb->len);

    ahash_request_set_crypt(req, sg, icv, skb->len);
    ahash_request_set_callback(req, 0, ah6_output_done, skb);

    AH_SKB_CB(skb)->tmp = iph_base;

    err = crypto_ahash_digest(req);
    if (err) {
        if (err == -EINPROGRESS)
            goto out;

        if (err == -EBUSY)
            err = NET_XMIT_DROP;
        goto out_free;
    }

    memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
    memcpy(top_iph, iph_base, IPV6HDR_BASELEN);

    if (extlen) {
#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
        memcpy(&top_iph->saddr, iph_ext, extlen);
#else
        memcpy(&top_iph->daddr, iph_ext, extlen);
#endif
    }

out_free:
    kfree(iph_base);
out:
    return err;
}

static void ah6_input_done(struct crypto_async_request *base, int err)
{
    u8 *auth_data;
    u8 *icv;
    u8 *work_iph;
    struct sk_buff *skb = base->data;
    struct xfrm_state *x = xfrm_input_state(skb);
    struct ah_data *ahp = x->data;
    struct ip_auth_hdr *ah = ip_auth_hdr(skb);
    int hdr_len = skb_network_header_len(skb);
    int ah_hlen = (ah->hdrlen + 2) << 2;

    work_iph = AH_SKB_CB(skb)->tmp;
    auth_data = ah_tmp_auth(work_iph, hdr_len);
    icv = ah_tmp_icv(ahp->ahash, auth_data, ahp->icv_trunc_len);

    err = memcmp(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG: 0;
    if (err)
        goto out;

    err = ah->nexthdr;

    skb->network_header += ah_hlen;
    memcpy(skb_network_header(skb), work_iph, hdr_len);
    __skb_pull(skb, ah_hlen + hdr_len);
    skb_set_transport_header(skb, -hdr_len);
out:
    kfree(AH_SKB_CB(skb)->tmp);
    xfrm_input_resume(skb, err);
}



static int ah6_input(struct xfrm_state *x, struct sk_buff *skb)
{
    /*
     * Before process AH
     * [IPv6][Ext1][Ext2][AH][Dest][Payload]
     * |<-------------->| hdr_len
     *
     * To erase AH:
     * Keeping copy of cleared headers. After AH processing,
     * Moving the pointer of skb->network_header by using skb_pull as long
     * as AH header length. Then copy back the copy as long as hdr_len
     * If destination header following AH exists, copy it into after [Ext2].
     *
     * |<>|[IPv6][Ext1][Ext2][Dest][Payload]
     * There is offset of AH before IPv6 header after the process.
     */

    u8 *auth_data;
    u8 *icv;
    u8 *work_iph;
    struct sk_buff *trailer;
    struct crypto_ahash *ahash;
    struct ahash_request *req;
    struct scatterlist *sg;
    struct ip_auth_hdr *ah;
    struct ipv6hdr *ip6h;
    struct ah_data *ahp;
    u16 hdr_len;
    u16 ah_hlen;
    int nexthdr;
    int nfrags;
    int err = -ENOMEM;

    if (!pskb_may_pull(skb, sizeof(struct ip_auth_hdr)))
        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;

    hdr_len = skb_network_header_len(skb);
    ah = (struct ip_auth_hdr *)skb->data;
    ahp = x->data;
    ahash = ahp->ahash;

    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;


    if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
        goto out;
    nfrags = err;

    ah = (struct ip_auth_hdr *)skb->data;
    ip6h = ipv6_hdr(skb);

    skb_push(skb, hdr_len);

    work_iph = ah_alloc_tmp(ahash, nfrags, hdr_len + ahp->icv_trunc_len);
    if (!work_iph)
        goto out;

    auth_data = ah_tmp_auth(work_iph, hdr_len);
    icv = ah_tmp_icv(ahash, auth_data, ahp->icv_trunc_len);
    req = ah_tmp_req(ahash, icv);
    sg = ah_req_sg(ahash, req);

    memcpy(work_iph, ip6h, hdr_len);
    memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
    memset(ah->auth_data, 0, ahp->icv_trunc_len);

    if (ipv6_clear_mutable_options(ip6h, hdr_len, XFRM_POLICY_IN))
        goto out_free;

    ip6h->priority    = 0;
    ip6h->flow_lbl[0] = 0;
    ip6h->flow_lbl[1] = 0;
    ip6h->flow_lbl[2] = 0;
    ip6h->hop_limit   = 0;

    sg_init_table(sg, nfrags);
    skb_to_sgvec(skb, sg, 0, skb->len);

    ahash_request_set_crypt(req, sg, icv, skb->len);
    ahash_request_set_callback(req, 0, ah6_input_done, skb);

    AH_SKB_CB(skb)->tmp = work_iph;

    err = crypto_ahash_digest(req);
    if (err) {
        if (err == -EINPROGRESS)
            goto out;

        goto out_free;
    }

    err = memcmp(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG: 0;
    if (err)
        goto out_free;

    skb->network_header += ah_hlen;
    memcpy(skb_network_header(skb), work_iph, hdr_len);
    skb->transport_header = skb->network_header;
    __skb_pull(skb, ah_hlen + hdr_len);

    err = nexthdr;

out_free:
    kfree(work_iph);
out:
    return err;
}

static void ah6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
            u8 type, u8 code, int offset, __be32 info)
{
    struct net *net = dev_net(skb->dev);
    struct ipv6hdr *iph = (struct ipv6hdr*)skb->data;
    struct ip_auth_hdr *ah = (struct ip_auth_hdr*)(skb->data+offset);
    struct xfrm_state *x;

    if (type != ICMPV6_DEST_UNREACH &&
        type != ICMPV6_PKT_TOOBIG &&
        type != NDISC_REDIRECT)
        return;

    x = xfrm_state_lookup(net, skb->mark, (xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET6);
    if (!x)
        return;

    if (type == NDISC_REDIRECT)
        ip6_redirect(skb, net, 0, 0);
    else
        ip6_update_pmtu(skb, net, info, 0, 0);
    xfrm_state_put(x);
}

static int ah6_init_state(struct xfrm_state *x)
{
    struct ah_data *ahp = NULL;
    struct xfrm_algo_desc *aalg_desc;
    struct crypto_ahash *ahash;

    if (!x->aalg)
        goto error;

    if (x->encap)
        goto error;

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

    ahash = crypto_alloc_ahash(x->aalg->alg_name, 0, 0);
    if (IS_ERR(ahash))
        goto error;

    ahp->ahash = ahash;
    if (crypto_ahash_setkey(ahash, 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_ahash_digestsize(ahash)) {
        pr_info("AH: %s digestsize %u != %hu\n",
            x->aalg->alg_name, crypto_ahash_digestsize(ahash),
            aalg_desc->uinfo.auth.icv_fullbits/8);
        goto error;
    }

    ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
    ahp->icv_trunc_len = x->aalg->alg_trunc_len/8;

    BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);

    x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
                      ahp->icv_trunc_len);
    switch (x->props.mode) {
    case XFRM_MODE_BEET:
    case XFRM_MODE_TRANSPORT:
        break;
    case XFRM_MODE_TUNNEL:
        x->props.header_len += sizeof(struct ipv6hdr);
        break;
    default:
        goto error;
    }
    x->data = ahp;

    return 0;

error:
    if (ahp) {
        crypto_free_ahash(ahp->ahash);
        kfree(ahp);
    }
    return -EINVAL;
}

static void ah6_destroy(struct xfrm_state *x)
{
    struct ah_data *ahp = x->data;

    if (!ahp)
        return;

    crypto_free_ahash(ahp->ahash);
    kfree(ahp);
}

static const struct xfrm_type ah6_type =
{
    .description    = "AH6",
    .owner      = THIS_MODULE,
    .proto          = IPPROTO_AH,
    .flags      = XFRM_TYPE_REPLAY_PROT,
    .init_state = ah6_init_state,
    .destructor = ah6_destroy,
    .input      = ah6_input,
    .output     = ah6_output,
    .hdr_offset = xfrm6_find_1stfragopt,
};

static const struct inet6_protocol ah6_protocol = {
    .handler    =   xfrm6_rcv,
    .err_handler    =   ah6_err,
    .flags      =   INET6_PROTO_NOPOLICY,
};

static int __init ah6_init(void)
{
    if (xfrm_register_type(&ah6_type, AF_INET6) < 0) {
        pr_info("%s: can't add xfrm type\n", __func__);
        return -EAGAIN;
    }

    if (inet6_add_protocol(&ah6_protocol, IPPROTO_AH) < 0) {
        pr_info("%s: can't add protocol\n", __func__);
        xfrm_unregister_type(&ah6_type, AF_INET6);
        return -EAGAIN;
    }

    return 0;
}

static void __exit ah6_fini(void)
{
    if (inet6_del_protocol(&ah6_protocol, IPPROTO_AH) < 0)
        pr_info("%s: can't remove protocol\n", __func__);

    if (xfrm_unregister_type(&ah6_type, AF_INET6) < 0)
        pr_info("%s: can't remove xfrm type\n", __func__);

}

module_init(ah6_init);
module_exit(ah6_fini);

MODULE_LICENSE("GPL");
MODULE_ALIAS_XFRM_TYPE(AF_INET6, XFRM_PROTO_AH);