linux/net/ipv4/ah4.c
Evan Nimmo 9ab1265d52 xfrm: Use actual socket sk instead of skb socket for xfrm_output_resume
A situation can occur where the interface bound to the sk is different
to the interface bound to the sk attached to the skb. The interface
bound to the sk is the correct one however this information is lost inside
xfrm_output2 and instead the sk on the skb is used in xfrm_output_resume
instead. This assumes that the sk bound interface and the bound interface
attached to the sk within the skb are the same which can lead to lookup
failures inside ip_route_me_harder resulting in the packet being dropped.

We have an l2tp v3 tunnel with ipsec protection. The tunnel is in the
global VRF however we have an encapsulated dot1q tunnel interface that
is within a different VRF. We also have a mangle rule that marks the
packets causing them to be processed inside ip_route_me_harder.

Prior to commit 31c70d5956 ("l2tp: keep original skb ownership") this
worked fine as the sk attached to the skb was changed from the dot1q
encapsulated interface to the sk for the tunnel which meant the interface
bound to the sk and the interface bound to the skb were identical.
Commit 46d6c5ae95 ("netfilter: use actual socket sk rather than skb sk
when routing harder") fixed some of these issues however a similar
problem existed in the xfrm code.

Fixes: 31c70d5956 ("l2tp: keep original skb ownership")
Signed-off-by: Evan Nimmo <evan.nimmo@alliedtelesis.co.nz>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
2021-03-03 09:32:52 +01:00

600 lines
14 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
#define pr_fmt(fmt) "IPsec: " fmt
#include <crypto/algapi.h>
#include <crypto/hash.h>
#include <linux/err.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <net/ip.h>
#include <net/xfrm.h>
#include <net/ah.h>
#include <linux/crypto.h>
#include <linux/pfkeyv2.h>
#include <linux/scatterlist.h>
#include <net/icmp.h>
#include <net/protocol.h>
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 u8 *ah_tmp_auth(void *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));
}
/* 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(const 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);
fallthrough;
default:
memset(optptr, 0, optlen);
}
l -= optlen;
optptr += optlen;
}
return 0;
}
static void ah_output_done(struct crypto_async_request *base, int err)
{
u8 *icv;
struct iphdr *iph;
struct sk_buff *skb = base->data;
struct xfrm_state *x = skb_dst(skb)->xfrm;
struct ah_data *ahp = x->data;
struct iphdr *top_iph = ip_hdr(skb);
struct ip_auth_hdr *ah = ip_auth_hdr(skb);
int ihl = ip_hdrlen(skb);
iph = AH_SKB_CB(skb)->tmp;
icv = ah_tmp_icv(ahp->ahash, iph, ihl);
memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
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));
}
kfree(AH_SKB_CB(skb)->tmp);
xfrm_output_resume(skb->sk, skb, err);
}
static int ah_output(struct xfrm_state *x, struct sk_buff *skb)
{
int err;
int nfrags;
int ihl;
u8 *icv;
struct sk_buff *trailer;
struct crypto_ahash *ahash;
struct ahash_request *req;
struct scatterlist *sg;
struct iphdr *iph, *top_iph;
struct ip_auth_hdr *ah;
struct ah_data *ahp;
int seqhi_len = 0;
__be32 *seqhi;
int sglists = 0;
struct scatterlist *seqhisg;
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));
ah = ip_auth_hdr(skb);
ihl = ip_hdrlen(skb);
if (x->props.flags & XFRM_STATE_ESN) {
sglists = 1;
seqhi_len = sizeof(*seqhi);
}
err = -ENOMEM;
iph = ah_alloc_tmp(ahash, nfrags + sglists, ihl + seqhi_len);
if (!iph)
goto out;
seqhi = (__be32 *)((char *)iph + ihl);
icv = ah_tmp_icv(ahash, seqhi, seqhi_len);
req = ah_tmp_req(ahash, icv);
sg = ah_req_sg(ahash, req);
seqhisg = sg + nfrags;
memset(ah->auth_data, 0, ahp->icv_trunc_len);
top_iph = ip_hdr(skb);
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 out_free;
}
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;
if (x->props.flags & XFRM_STATE_ALIGN4)
ah->hdrlen = (XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
else
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 + sglists);
err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
if (unlikely(err < 0))
goto out_free;
if (x->props.flags & XFRM_STATE_ESN) {
/* Attach seqhi sg right after packet payload */
*seqhi = htonl(XFRM_SKB_CB(skb)->seq.output.hi);
sg_set_buf(seqhisg, seqhi, seqhi_len);
}
ahash_request_set_crypt(req, sg, icv, skb->len + seqhi_len);
ahash_request_set_callback(req, 0, ah_output_done, skb);
AH_SKB_CB(skb)->tmp = iph;
err = crypto_ahash_digest(req);
if (err) {
if (err == -EINPROGRESS)
goto out;
if (err == -ENOSPC)
err = NET_XMIT_DROP;
goto out_free;
}
memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
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));
}
out_free:
kfree(iph);
out:
return err;
}
static void ah_input_done(struct crypto_async_request *base, int err)
{
u8 *auth_data;
u8 *icv;
struct iphdr *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 ihl = ip_hdrlen(skb);
int ah_hlen = (ah->hdrlen + 2) << 2;
if (err)
goto out;
work_iph = AH_SKB_CB(skb)->tmp;
auth_data = ah_tmp_auth(work_iph, ihl);
icv = ah_tmp_icv(ahp->ahash, auth_data, ahp->icv_trunc_len);
err = crypto_memneq(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, ihl);
__skb_pull(skb, ah_hlen + ihl);
if (x->props.mode == XFRM_MODE_TUNNEL)
skb_reset_transport_header(skb);
else
skb_set_transport_header(skb, -ihl);
out:
kfree(AH_SKB_CB(skb)->tmp);
xfrm_input_resume(skb, err);
}
static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
{
int ah_hlen;
int ihl;
int nexthdr;
int nfrags;
u8 *auth_data;
u8 *icv;
struct sk_buff *trailer;
struct crypto_ahash *ahash;
struct ahash_request *req;
struct scatterlist *sg;
struct iphdr *iph, *work_iph;
struct ip_auth_hdr *ah;
struct ah_data *ahp;
int err = -ENOMEM;
int seqhi_len = 0;
__be32 *seqhi;
int sglists = 0;
struct scatterlist *seqhisg;
if (!pskb_may_pull(skb, sizeof(*ah)))
goto out;
ah = (struct ip_auth_hdr *)skb->data;
ahp = x->data;
ahash = ahp->ahash;
nexthdr = ah->nexthdr;
ah_hlen = (ah->hdrlen + 2) << 2;
if (x->props.flags & XFRM_STATE_ALIGN4) {
if (ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_full_len) &&
ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len))
goto out;
} else {
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_unclone(skb, GFP_ATOMIC))
goto out;
skb->ip_summed = CHECKSUM_NONE;
if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
goto out;
nfrags = err;
ah = (struct ip_auth_hdr *)skb->data;
iph = ip_hdr(skb);
ihl = ip_hdrlen(skb);
if (x->props.flags & XFRM_STATE_ESN) {
sglists = 1;
seqhi_len = sizeof(*seqhi);
}
work_iph = ah_alloc_tmp(ahash, nfrags + sglists, ihl +
ahp->icv_trunc_len + seqhi_len);
if (!work_iph) {
err = -ENOMEM;
goto out;
}
seqhi = (__be32 *)((char *)work_iph + ihl);
auth_data = ah_tmp_auth(seqhi, seqhi_len);
icv = ah_tmp_icv(ahash, auth_data, ahp->icv_trunc_len);
req = ah_tmp_req(ahash, icv);
sg = ah_req_sg(ahash, req);
seqhisg = sg + nfrags;
memcpy(work_iph, iph, ihl);
memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
memset(ah->auth_data, 0, ahp->icv_trunc_len);
iph->ttl = 0;
iph->tos = 0;
iph->frag_off = 0;
iph->check = 0;
if (ihl > sizeof(*iph)) {
__be32 dummy;
err = ip_clear_mutable_options(iph, &dummy);
if (err)
goto out_free;
}
skb_push(skb, ihl);
sg_init_table(sg, nfrags + sglists);
err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
if (unlikely(err < 0))
goto out_free;
if (x->props.flags & XFRM_STATE_ESN) {
/* Attach seqhi sg right after packet payload */
*seqhi = XFRM_SKB_CB(skb)->seq.input.hi;
sg_set_buf(seqhisg, seqhi, seqhi_len);
}
ahash_request_set_crypt(req, sg, icv, skb->len + seqhi_len);
ahash_request_set_callback(req, 0, ah_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 = crypto_memneq(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, ihl);
__skb_pull(skb, ah_hlen + ihl);
if (x->props.mode == XFRM_MODE_TUNNEL)
skb_reset_transport_header(skb);
else
skb_set_transport_header(skb, -ihl);
err = nexthdr;
out_free:
kfree (work_iph);
out:
return err;
}
static int ah4_err(struct sk_buff *skb, u32 info)
{
struct net *net = dev_net(skb->dev);
const struct iphdr *iph = (const struct iphdr *)skb->data;
struct ip_auth_hdr *ah = (struct ip_auth_hdr *)(skb->data+(iph->ihl<<2));
struct xfrm_state *x;
switch (icmp_hdr(skb)->type) {
case ICMP_DEST_UNREACH:
if (icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
return 0;
case ICMP_REDIRECT:
break;
default:
return 0;
}
x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
ah->spi, IPPROTO_AH, AF_INET);
if (!x)
return 0;
if (icmp_hdr(skb)->type == ICMP_DEST_UNREACH)
ipv4_update_pmtu(skb, net, info, 0, IPPROTO_AH);
else
ipv4_redirect(skb, net, 0, IPPROTO_AH);
xfrm_state_put(x);
return 0;
}
static int ah_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)
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_ahash().
*/
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("%s: %s digestsize %u != %hu\n",
__func__, 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;
if (x->props.flags & XFRM_STATE_ALIGN4)
x->props.header_len = XFRM_ALIGN4(sizeof(struct ip_auth_hdr) +
ahp->icv_trunc_len);
else
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) {
crypto_free_ahash(ahp->ahash);
kfree(ahp);
}
return -EINVAL;
}
static void ah_destroy(struct xfrm_state *x)
{
struct ah_data *ahp = x->data;
if (!ahp)
return;
crypto_free_ahash(ahp->ahash);
kfree(ahp);
}
static int ah4_rcv_cb(struct sk_buff *skb, int err)
{
return 0;
}
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 xfrm4_protocol ah4_protocol = {
.handler = xfrm4_rcv,
.input_handler = xfrm_input,
.cb_handler = ah4_rcv_cb,
.err_handler = ah4_err,
.priority = 0,
};
static int __init ah4_init(void)
{
if (xfrm_register_type(&ah_type, AF_INET) < 0) {
pr_info("%s: can't add xfrm type\n", __func__);
return -EAGAIN;
}
if (xfrm4_protocol_register(&ah4_protocol, IPPROTO_AH) < 0) {
pr_info("%s: can't add protocol\n", __func__);
xfrm_unregister_type(&ah_type, AF_INET);
return -EAGAIN;
}
return 0;
}
static void __exit ah4_fini(void)
{
if (xfrm4_protocol_deregister(&ah4_protocol, IPPROTO_AH) < 0)
pr_info("%s: can't remove protocol\n", __func__);
xfrm_unregister_type(&ah_type, AF_INET);
}
module_init(ah4_init);
module_exit(ah4_fini);
MODULE_LICENSE("GPL");
MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_AH);