ipv6: Prevent overrun when parsing v6 header options

[mirror_ubuntu-zesty-kernel.git] / net / ipv6 / esp6.c

/*
 * 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, see <http://www.gnu.org/licenses/>.
 *
 * Authors
 *
 *      Mitsuru KANDA @USAGI       : IPv6 Support
 *      Kazunori MIYAZAWA @USAGI   :
 *      Kunihiro Ishiguro <kunihiro@ipinfusion.com>
 *
 *      This file is derived from net/ipv4/esp.c
 */

#define pr_fmt(fmt) "IPv6: " fmt

#include <crypto/aead.h>
#include <crypto/authenc.h>
#include <linux/err.h>
#include <linux/module.h>
#include <net/ip.h>
#include <net/xfrm.h>
#include <net/esp.h>
#include <linux/scatterlist.h>
#include <linux/kernel.h>
#include <linux/pfkeyv2.h>
#include <linux/random.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <net/ip6_route.h>
#include <net/icmp.h>
#include <net/ipv6.h>
#include <net/protocol.h>
#include <linux/icmpv6.h>

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

#define ESP_SKB_CB(__skb) ((struct esp_skb_cb *)&((__skb)->cb[0]))

static u32 esp6_get_mtu(struct xfrm_state *x, int mtu);

/*
 * Allocate an AEAD request structure with extra space for SG and IV.
 *
 * For alignment considerations the upper 32 bits of the sequence number are
 * placed at the front, if present. Followed by the IV, the request and finally
 * the SG list.
 *
 * TODO: Use spare space in skb for this where possible.
 */
static void *esp_alloc_tmp(struct crypto_aead *aead, int nfrags, int seqihlen)
{
        unsigned int len;

        len = seqihlen;

        len += crypto_aead_ivsize(aead);

        if (len) {
                len += crypto_aead_alignmask(aead) &
                       ~(crypto_tfm_ctx_alignment() - 1);
                len = ALIGN(len, crypto_tfm_ctx_alignment());
        }

        len += sizeof(struct aead_request) + crypto_aead_reqsize(aead);
        len = ALIGN(len, __alignof__(struct scatterlist));

        len += sizeof(struct scatterlist) * nfrags;

        return kmalloc(len, GFP_ATOMIC);
}

static inline __be32 *esp_tmp_seqhi(void *tmp)
{
        return PTR_ALIGN((__be32 *)tmp, __alignof__(__be32));
}

static inline u8 *esp_tmp_iv(struct crypto_aead *aead, void *tmp, int seqhilen)
{
        return crypto_aead_ivsize(aead) ?
               PTR_ALIGN((u8 *)tmp + seqhilen,
                         crypto_aead_alignmask(aead) + 1) : tmp + seqhilen;
}

static inline struct aead_request *esp_tmp_req(struct crypto_aead *aead, u8 *iv)
{
        struct aead_request *req;

        req = (void *)PTR_ALIGN(iv + crypto_aead_ivsize(aead),
                                crypto_tfm_ctx_alignment());
        aead_request_set_tfm(req, aead);
        return req;
}

static inline struct scatterlist *esp_req_sg(struct crypto_aead *aead,
                                             struct aead_request *req)
{
        return (void *)ALIGN((unsigned long)(req + 1) +
                             crypto_aead_reqsize(aead),
                             __alignof__(struct scatterlist));
}

static void esp_output_done(struct crypto_async_request *base, int err)
{
        struct sk_buff *skb = base->data;

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

/* Move ESP header back into place. */
static void esp_restore_header(struct sk_buff *skb, unsigned int offset)
{
        struct ip_esp_hdr *esph = (void *)(skb->data + offset);
        void *tmp = ESP_SKB_CB(skb)->tmp;
        __be32 *seqhi = esp_tmp_seqhi(tmp);

        esph->seq_no = esph->spi;
        esph->spi = *seqhi;
}

static void esp_output_restore_header(struct sk_buff *skb)
{
        esp_restore_header(skb, skb_transport_offset(skb) - sizeof(__be32));
}

static void esp_output_done_esn(struct crypto_async_request *base, int err)
{
        struct sk_buff *skb = base->data;

        esp_output_restore_header(skb);
        esp_output_done(base, err);
}

static int esp6_output(struct xfrm_state *x, struct sk_buff *skb)
{
        int err;
        struct ip_esp_hdr *esph;
        struct crypto_aead *aead;
        struct aead_request *req;
        struct scatterlist *sg;
        struct sk_buff *trailer;
        void *tmp;
        int blksize;
        int clen;
        int alen;
        int plen;
        int ivlen;
        int tfclen;
        int nfrags;
        int assoclen;
        int seqhilen;
        u8 *iv;
        u8 *tail;
        __be32 *seqhi;
        __be64 seqno;

        /* skb is pure payload to encrypt */
        aead = x->data;
        alen = crypto_aead_authsize(aead);
        ivlen = crypto_aead_ivsize(aead);

        tfclen = 0;
        if (x->tfcpad) {
                struct xfrm_dst *dst = (struct xfrm_dst *)skb_dst(skb);
                u32 padto;

                padto = min(x->tfcpad, esp6_get_mtu(x, dst->child_mtu_cached));
                if (skb->len < padto)
                        tfclen = padto - skb->len;
        }
        blksize = ALIGN(crypto_aead_blocksize(aead), 4);
        clen = ALIGN(skb->len + 2 + tfclen, blksize);
        plen = clen - skb->len - tfclen;

        err = skb_cow_data(skb, tfclen + plen + alen, &trailer);
        if (err < 0)
                goto error;
        nfrags = err;

        assoclen = sizeof(*esph);
        seqhilen = 0;

        if (x->props.flags & XFRM_STATE_ESN) {
                seqhilen += sizeof(__be32);
                assoclen += seqhilen;
        }

        tmp = esp_alloc_tmp(aead, nfrags, seqhilen);
        if (!tmp) {
                err = -ENOMEM;
                goto error;
        }

        seqhi = esp_tmp_seqhi(tmp);
        iv = esp_tmp_iv(aead, tmp, seqhilen);
        req = esp_tmp_req(aead, iv);
        sg = esp_req_sg(aead, req);

        /* Fill padding... */
        tail = skb_tail_pointer(trailer);
        if (tfclen) {
                memset(tail, 0, tfclen);
                tail += tfclen;
        }
        do {
                int i;
                for (i = 0; i < plen - 2; i++)
                        tail[i] = i + 1;
        } while (0);
        tail[plen - 2] = plen - 2;
        tail[plen - 1] = *skb_mac_header(skb);
        pskb_put(skb, trailer, clen - skb->len + alen);

        skb_push(skb, -skb_network_offset(skb));
        esph = ip_esp_hdr(skb);
        *skb_mac_header(skb) = IPPROTO_ESP;

        esph->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);

        aead_request_set_callback(req, 0, esp_output_done, skb);

        /* For ESN we move the header forward by 4 bytes to
         * accomodate the high bits.  We will move it back after
         * encryption.
         */
        if ((x->props.flags & XFRM_STATE_ESN)) {
                esph = (void *)(skb_transport_header(skb) - sizeof(__be32));
                *seqhi = esph->spi;
                esph->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.hi);
                aead_request_set_callback(req, 0, esp_output_done_esn, skb);
        }

        esph->spi = x->id.spi;

        sg_init_table(sg, nfrags);
        skb_to_sgvec(skb, sg,
                     (unsigned char *)esph - skb->data,
                     assoclen + ivlen + clen + alen);

        aead_request_set_crypt(req, sg, sg, ivlen + clen, iv);
        aead_request_set_ad(req, assoclen);

        seqno = cpu_to_be64(XFRM_SKB_CB(skb)->seq.output.low +
                            ((u64)XFRM_SKB_CB(skb)->seq.output.hi << 32));

        memset(iv, 0, ivlen);
        memcpy(iv + ivlen - min(ivlen, 8), (u8 *)&seqno + 8 - min(ivlen, 8),
               min(ivlen, 8));

        ESP_SKB_CB(skb)->tmp = tmp;
        err = crypto_aead_encrypt(req);

        switch (err) {
        case -EINPROGRESS:
                goto error;

        case -EBUSY:
                err = NET_XMIT_DROP;
                break;

        case 0:
                if ((x->props.flags & XFRM_STATE_ESN))
                        esp_output_restore_header(skb);
        }

        kfree(tmp);

error:
        return err;
}

static int esp_input_done2(struct sk_buff *skb, int err)
{
        struct xfrm_state *x = xfrm_input_state(skb);
        struct crypto_aead *aead = x->data;
        int alen = crypto_aead_authsize(aead);
        int hlen = sizeof(struct ip_esp_hdr) + crypto_aead_ivsize(aead);
        int elen = skb->len - hlen;
        int hdr_len = skb_network_header_len(skb);
        int padlen;
        u8 nexthdr[2];

        kfree(ESP_SKB_CB(skb)->tmp);

        if (unlikely(err))
                goto out;

        if (skb_copy_bits(skb, skb->len - alen - 2, nexthdr, 2))
                BUG();

        err = -EINVAL;
        padlen = nexthdr[0];
        if (padlen + 2 + alen >= elen) {
                net_dbg_ratelimited("ipsec esp packet is garbage padlen=%d, elen=%d\n",
                                    padlen + 2, elen - alen);
                goto out;
        }

        /* ... check padding bits here. Silly. :-) */

        pskb_trim(skb, skb->len - alen - padlen - 2);
        __skb_pull(skb, hlen);
        if (x->props.mode == XFRM_MODE_TUNNEL)
                skb_reset_transport_header(skb);
        else
                skb_set_transport_header(skb, -hdr_len);

        err = nexthdr[1];

        /* RFC4303: Drop dummy packets without any error */
        if (err == IPPROTO_NONE)
                err = -EINVAL;

out:
        return err;
}

static void esp_input_done(struct crypto_async_request *base, int err)
{
        struct sk_buff *skb = base->data;

        xfrm_input_resume(skb, esp_input_done2(skb, err));
}

static void esp_input_restore_header(struct sk_buff *skb)
{
        esp_restore_header(skb, 0);
        __skb_pull(skb, 4);
}

static void esp_input_done_esn(struct crypto_async_request *base, int err)
{
        struct sk_buff *skb = base->data;

        esp_input_restore_header(skb);
        esp_input_done(base, err);
}

static int esp6_input(struct xfrm_state *x, struct sk_buff *skb)
{
        struct ip_esp_hdr *esph;
        struct crypto_aead *aead = x->data;
        struct aead_request *req;
        struct sk_buff *trailer;
        int ivlen = crypto_aead_ivsize(aead);
        int elen = skb->len - sizeof(*esph) - ivlen;
        int nfrags;
        int assoclen;
        int seqhilen;
        int ret = 0;
        void *tmp;
        __be32 *seqhi;
        u8 *iv;
        struct scatterlist *sg;

        if (!pskb_may_pull(skb, sizeof(*esph) + ivlen)) {
                ret = -EINVAL;
                goto out;
        }

        if (elen <= 0) {
                ret = -EINVAL;
                goto out;
        }

        nfrags = skb_cow_data(skb, 0, &trailer);
        if (nfrags < 0) {
                ret = -EINVAL;
                goto out;
        }

        ret = -ENOMEM;

        assoclen = sizeof(*esph);
        seqhilen = 0;

        if (x->props.flags & XFRM_STATE_ESN) {
                seqhilen += sizeof(__be32);
                assoclen += seqhilen;
        }

        tmp = esp_alloc_tmp(aead, nfrags, seqhilen);
        if (!tmp)
                goto out;

        ESP_SKB_CB(skb)->tmp = tmp;
        seqhi = esp_tmp_seqhi(tmp);
        iv = esp_tmp_iv(aead, tmp, seqhilen);
        req = esp_tmp_req(aead, iv);
        sg = esp_req_sg(aead, req);

        skb->ip_summed = CHECKSUM_NONE;

        esph = (struct ip_esp_hdr *)skb->data;

        aead_request_set_callback(req, 0, esp_input_done, skb);

        /* For ESN we move the header forward by 4 bytes to
         * accomodate the high bits.  We will move it back after
         * decryption.
         */
        if ((x->props.flags & XFRM_STATE_ESN)) {
                esph = (void *)skb_push(skb, 4);
                *seqhi = esph->spi;
                esph->spi = esph->seq_no;
                esph->seq_no = XFRM_SKB_CB(skb)->seq.input.hi;
                aead_request_set_callback(req, 0, esp_input_done_esn, skb);
        }

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

        aead_request_set_crypt(req, sg, sg, elen + ivlen, iv);
        aead_request_set_ad(req, assoclen);

        ret = crypto_aead_decrypt(req);
        if (ret == -EINPROGRESS)
                goto out;

        if ((x->props.flags & XFRM_STATE_ESN))
                esp_input_restore_header(skb);

        ret = esp_input_done2(skb, ret);

out:
        return ret;
}

static u32 esp6_get_mtu(struct xfrm_state *x, int mtu)
{
        struct crypto_aead *aead = x->data;
        u32 blksize = ALIGN(crypto_aead_blocksize(aead), 4);
        unsigned int net_adj;

        if (x->props.mode != XFRM_MODE_TUNNEL)
                net_adj = sizeof(struct ipv6hdr);
        else
                net_adj = 0;

        return ((mtu - x->props.header_len - crypto_aead_authsize(aead) -
                 net_adj) & ~(blksize - 1)) + net_adj - 2;
}

static int esp6_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);
        const struct ipv6hdr *iph = (const struct ipv6hdr *)skb->data;
        struct ip_esp_hdr *esph = (struct ip_esp_hdr *)(skb->data + offset);
        struct xfrm_state *x;

        if (type != ICMPV6_PKT_TOOBIG &&
            type != NDISC_REDIRECT)
                return 0;

        x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
                              esph->spi, IPPROTO_ESP, AF_INET6);
        if (!x)
                return 0;

        if (type == NDISC_REDIRECT)
                ip6_redirect(skb, net, skb->dev->ifindex, 0,
                             sock_net_uid(net, NULL));
        else
                ip6_update_pmtu(skb, net, info, 0, 0, sock_net_uid(net, NULL));
        xfrm_state_put(x);

        return 0;
}

static void esp6_destroy(struct xfrm_state *x)
{
        struct crypto_aead *aead = x->data;

        if (!aead)
                return;

        crypto_free_aead(aead);
}

static int esp_init_aead(struct xfrm_state *x)
{
        char aead_name[CRYPTO_MAX_ALG_NAME];
        struct crypto_aead *aead;
        int err;

        err = -ENAMETOOLONG;
        if (snprintf(aead_name, CRYPTO_MAX_ALG_NAME, "%s(%s)",
                     x->geniv, x->aead->alg_name) >= CRYPTO_MAX_ALG_NAME)
                goto error;

        aead = crypto_alloc_aead(aead_name, 0, 0);
        err = PTR_ERR(aead);
        if (IS_ERR(aead))
                goto error;

        x->data = aead;

        err = crypto_aead_setkey(aead, x->aead->alg_key,
                                 (x->aead->alg_key_len + 7) / 8);
        if (err)
                goto error;

        err = crypto_aead_setauthsize(aead, x->aead->alg_icv_len / 8);
        if (err)
                goto error;

error:
        return err;
}

static int esp_init_authenc(struct xfrm_state *x)
{
        struct crypto_aead *aead;
        struct crypto_authenc_key_param *param;
        struct rtattr *rta;
        char *key;
        char *p;
        char authenc_name[CRYPTO_MAX_ALG_NAME];
        unsigned int keylen;
        int err;

        err = -EINVAL;
        if (!x->ealg)
                goto error;

        err = -ENAMETOOLONG;

        if ((x->props.flags & XFRM_STATE_ESN)) {
                if (snprintf(authenc_name, CRYPTO_MAX_ALG_NAME,
                             "%s%sauthencesn(%s,%s)%s",
                             x->geniv ?: "", x->geniv ? "(" : "",
                             x->aalg ? x->aalg->alg_name : "digest_null",
                             x->ealg->alg_name,
                             x->geniv ? ")" : "") >= CRYPTO_MAX_ALG_NAME)
                        goto error;
        } else {
                if (snprintf(authenc_name, CRYPTO_MAX_ALG_NAME,
                             "%s%sauthenc(%s,%s)%s",
                             x->geniv ?: "", x->geniv ? "(" : "",
                             x->aalg ? x->aalg->alg_name : "digest_null",
                             x->ealg->alg_name,
                             x->geniv ? ")" : "") >= CRYPTO_MAX_ALG_NAME)
                        goto error;
        }

        aead = crypto_alloc_aead(authenc_name, 0, 0);
        err = PTR_ERR(aead);
        if (IS_ERR(aead))
                goto error;

        x->data = aead;

        keylen = (x->aalg ? (x->aalg->alg_key_len + 7) / 8 : 0) +
                 (x->ealg->alg_key_len + 7) / 8 + RTA_SPACE(sizeof(*param));
        err = -ENOMEM;
        key = kmalloc(keylen, GFP_KERNEL);
        if (!key)
                goto error;

        p = key;
        rta = (void *)p;
        rta->rta_type = CRYPTO_AUTHENC_KEYA_PARAM;
        rta->rta_len = RTA_LENGTH(sizeof(*param));
        param = RTA_DATA(rta);
        p += RTA_SPACE(sizeof(*param));

        if (x->aalg) {
                struct xfrm_algo_desc *aalg_desc;

                memcpy(p, x->aalg->alg_key, (x->aalg->alg_key_len + 7) / 8);
                p += (x->aalg->alg_key_len + 7) / 8;

                aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
                BUG_ON(!aalg_desc);

                err = -EINVAL;
                if (aalg_desc->uinfo.auth.icv_fullbits / 8 !=
                    crypto_aead_authsize(aead)) {
                        pr_info("ESP: %s digestsize %u != %hu\n",
                                x->aalg->alg_name,
                                crypto_aead_authsize(aead),
                                aalg_desc->uinfo.auth.icv_fullbits / 8);
                        goto free_key;
                }

                err = crypto_aead_setauthsize(
                        aead, x->aalg->alg_trunc_len / 8);
                if (err)
                        goto free_key;
        }

        param->enckeylen = cpu_to_be32((x->ealg->alg_key_len + 7) / 8);
        memcpy(p, x->ealg->alg_key, (x->ealg->alg_key_len + 7) / 8);

        err = crypto_aead_setkey(aead, key, keylen);

free_key:
        kfree(key);

error:
        return err;
}

static int esp6_init_state(struct xfrm_state *x)
{
        struct crypto_aead *aead;
        u32 align;
        int err;

        if (x->encap)
                return -EINVAL;

        x->data = NULL;

        if (x->aead)
                err = esp_init_aead(x);
        else
                err = esp_init_authenc(x);

        if (err)
                goto error;

        aead = x->data;

        x->props.header_len = sizeof(struct ip_esp_hdr) +
                              crypto_aead_ivsize(aead);
        switch (x->props.mode) {
        case XFRM_MODE_BEET:
                if (x->sel.family != AF_INET6)
                        x->props.header_len += IPV4_BEET_PHMAXLEN +
                                               (sizeof(struct ipv6hdr) - sizeof(struct iphdr));
                break;
        case XFRM_MODE_TRANSPORT:
                break;
        case XFRM_MODE_TUNNEL:
                x->props.header_len += sizeof(struct ipv6hdr);
                break;
        default:
                goto error;
        }

        align = ALIGN(crypto_aead_blocksize(aead), 4);
        x->props.trailer_len = align + 1 + crypto_aead_authsize(aead);

error:
        return err;
}

static int esp6_rcv_cb(struct sk_buff *skb, int err)
{
        return 0;
}

static const struct xfrm_type esp6_type = {
        .description    = "ESP6",
        .owner          = THIS_MODULE,
        .proto          = IPPROTO_ESP,
        .flags          = XFRM_TYPE_REPLAY_PROT,
        .init_state     = esp6_init_state,
        .destructor     = esp6_destroy,
        .get_mtu        = esp6_get_mtu,
        .input          = esp6_input,
        .output         = esp6_output,
        .hdr_offset     = xfrm6_find_1stfragopt,
};

static struct xfrm6_protocol esp6_protocol = {
        .handler        =       xfrm6_rcv,
        .cb_handler     =       esp6_rcv_cb,
        .err_handler    =       esp6_err,
        .priority       =       0,
};

static int __init esp6_init(void)
{
        if (xfrm_register_type(&esp6_type, AF_INET6) < 0) {
                pr_info("%s: can't add xfrm type\n", __func__);
                return -EAGAIN;
        }
        if (xfrm6_protocol_register(&esp6_protocol, IPPROTO_ESP) < 0) {
                pr_info("%s: can't add protocol\n", __func__);
                xfrm_unregister_type(&esp6_type, AF_INET6);
                return -EAGAIN;
        }

        return 0;
}

static void __exit esp6_fini(void)
{
        if (xfrm6_protocol_deregister(&esp6_protocol, IPPROTO_ESP) < 0)
                pr_info("%s: can't remove protocol\n", __func__);
        if (xfrm_unregister_type(&esp6_type, AF_INET6) < 0)
                pr_info("%s: can't remove xfrm type\n", __func__);
}

module_init(esp6_init);
module_exit(esp6_fini);

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