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alistair23-linux/net/mpls/mpls_iptunnel.c
Johannes Berg 8cb081746c netlink: make validation more configurable for future strictness 
We currently have two levels of strict validation:

 1) liberal (default)
     - undefined (type >= max) & NLA_UNSPEC attributes accepted
     - attribute length >= expected accepted
     - garbage at end of message accepted
 2) strict (opt-in)
     - NLA_UNSPEC attributes accepted
     - attribute length >= expected accepted

Split out parsing strictness into four different options:
 * TRAILING     - check that there's no trailing data after parsing
                  attributes (in message or nested)
 * MAXTYPE      - reject attrs > max known type
 * UNSPEC       - reject attributes with NLA_UNSPEC policy entries
 * STRICT_ATTRS - strictly validate attribute size

The default for future things should be *everything*.
The current *_strict() is a combination of TRAILING and MAXTYPE,
and is renamed to _deprecated_strict().
The current regular parsing has none of this, and is renamed to
*_parse_deprecated().

Additionally it allows us to selectively set one of the new flags
even on old policies. Notably, the UNSPEC flag could be useful in
this case, since it can be arranged (by filling in the policy) to
not be an incompatible userspace ABI change, but would then going
forward prevent forgetting attribute entries. Similar can apply
to the POLICY flag.

We end up with the following renames:
 * nla_parse           -> nla_parse_deprecated
 * nla_parse_strict    -> nla_parse_deprecated_strict
 * nlmsg_parse         -> nlmsg_parse_deprecated
 * nlmsg_parse_strict  -> nlmsg_parse_deprecated_strict
 * nla_parse_nested    -> nla_parse_nested_deprecated
 * nla_validate_nested -> nla_validate_nested_deprecated

Using spatch, of course:
    @@
    expression TB, MAX, HEAD, LEN, POL, EXT;
    @@
    -nla_parse(TB, MAX, HEAD, LEN, POL, EXT)
    +nla_parse_deprecated(TB, MAX, HEAD, LEN, POL, EXT)

    @@
    expression NLH, HDRLEN, TB, MAX, POL, EXT;
    @@
    -nlmsg_parse(NLH, HDRLEN, TB, MAX, POL, EXT)
    +nlmsg_parse_deprecated(NLH, HDRLEN, TB, MAX, POL, EXT)

    @@
    expression NLH, HDRLEN, TB, MAX, POL, EXT;
    @@
    -nlmsg_parse_strict(NLH, HDRLEN, TB, MAX, POL, EXT)
    +nlmsg_parse_deprecated_strict(NLH, HDRLEN, TB, MAX, POL, EXT)

    @@
    expression TB, MAX, NLA, POL, EXT;
    @@
    -nla_parse_nested(TB, MAX, NLA, POL, EXT)
    +nla_parse_nested_deprecated(TB, MAX, NLA, POL, EXT)

    @@
    expression START, MAX, POL, EXT;
    @@
    -nla_validate_nested(START, MAX, POL, EXT)
    +nla_validate_nested_deprecated(START, MAX, POL, EXT)

    @@
    expression NLH, HDRLEN, MAX, POL, EXT;
    @@
    -nlmsg_validate(NLH, HDRLEN, MAX, POL, EXT)
    +nlmsg_validate_deprecated(NLH, HDRLEN, MAX, POL, EXT)

For this patch, don't actually add the strict, non-renamed versions
yet so that it breaks compile if I get it wrong.

Also, while at it, make nla_validate and nla_parse go down to a
common __nla_validate_parse() function to avoid code duplication.

Ultimately, this allows us to have very strict validation for every
new caller of nla_parse()/nlmsg_parse() etc as re-introduced in the
next patch, while existing things will continue to work as is.

In effect then, this adds fully strict validation for any new command.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2019-04-27 17:07:21 -04:00

310 lines
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/*
* mpls tunnels An implementation mpls tunnels using the light weight tunnel
* infrastructure
*
* Authors: Roopa Prabhu, <roopa@cumulusnetworks.com>
*
* 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.
*
*/
#include <linux/types.h>
#include <linux/skbuff.h>
#include <linux/net.h>
#include <linux/module.h>
#include <linux/mpls.h>
#include <linux/vmalloc.h>
#include <net/ip.h>
#include <net/dst.h>
#include <net/lwtunnel.h>
#include <net/netevent.h>
#include <net/netns/generic.h>
#include <net/ip6_fib.h>
#include <net/route.h>
#include <net/mpls_iptunnel.h>
#include <linux/mpls_iptunnel.h>
#include "internal.h"
static const struct nla_policy mpls_iptunnel_policy[MPLS_IPTUNNEL_MAX + 1] = {
[MPLS_IPTUNNEL_DST] = { .type = NLA_U32 },
[MPLS_IPTUNNEL_TTL] = { .type = NLA_U8 },
};
static unsigned int mpls_encap_size(struct mpls_iptunnel_encap *en)
{
/* The size of the layer 2.5 labels to be added for this route */
return en->labels * sizeof(struct mpls_shim_hdr);
}
static int mpls_xmit(struct sk_buff *skb)
{
struct mpls_iptunnel_encap *tun_encap_info;
struct mpls_shim_hdr *hdr;
struct net_device *out_dev;
unsigned int hh_len;
unsigned int new_header_size;
unsigned int mtu;
struct dst_entry *dst = skb_dst(skb);
struct rtable *rt = NULL;
struct rt6_info *rt6 = NULL;
struct mpls_dev *out_mdev;
struct net *net;
int err = 0;
bool bos;
int i;
unsigned int ttl;
/* Find the output device */
out_dev = dst->dev;
net = dev_net(out_dev);
skb_orphan(skb);
if (!mpls_output_possible(out_dev) ||
!dst->lwtstate || skb_warn_if_lro(skb))
goto drop;
skb_forward_csum(skb);
tun_encap_info = mpls_lwtunnel_encap(dst->lwtstate);
/* Obtain the ttl using the following set of rules.
*
* LWT ttl propagation setting:
* - disabled => use default TTL value from LWT
* - enabled => use TTL value from IPv4/IPv6 header
* - default =>
* Global ttl propagation setting:
* - disabled => use default TTL value from global setting
* - enabled => use TTL value from IPv4/IPv6 header
*/
if (dst->ops->family == AF_INET) {
if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DISABLED)
ttl = tun_encap_info->default_ttl;
else if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DEFAULT &&
!net->mpls.ip_ttl_propagate)
ttl = net->mpls.default_ttl;
else
ttl = ip_hdr(skb)->ttl;
rt = (struct rtable *)dst;
} else if (dst->ops->family == AF_INET6) {
if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DISABLED)
ttl = tun_encap_info->default_ttl;
else if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DEFAULT &&
!net->mpls.ip_ttl_propagate)
ttl = net->mpls.default_ttl;
else
ttl = ipv6_hdr(skb)->hop_limit;
rt6 = (struct rt6_info *)dst;
} else {
goto drop;
}
/* Verify the destination can hold the packet */
new_header_size = mpls_encap_size(tun_encap_info);
mtu = mpls_dev_mtu(out_dev);
if (mpls_pkt_too_big(skb, mtu - new_header_size))
goto drop;
hh_len = LL_RESERVED_SPACE(out_dev);
if (!out_dev->header_ops)
hh_len = 0;
/* Ensure there is enough space for the headers in the skb */
if (skb_cow(skb, hh_len + new_header_size))
goto drop;
skb_set_inner_protocol(skb, skb->protocol);
skb_reset_inner_network_header(skb);
skb_push(skb, new_header_size);
skb_reset_network_header(skb);
skb->dev = out_dev;
skb->protocol = htons(ETH_P_MPLS_UC);
/* Push the new labels */
hdr = mpls_hdr(skb);
bos = true;
for (i = tun_encap_info->labels - 1; i >= 0; i--) {
hdr[i] = mpls_entry_encode(tun_encap_info->label[i],
ttl, 0, bos);
bos = false;
}
mpls_stats_inc_outucastpkts(out_dev, skb);
if (rt) {
if (rt->rt_gw_family == AF_INET)
err = neigh_xmit(NEIGH_ARP_TABLE, out_dev, &rt->rt_gw4,
skb);
else if (rt->rt_gw_family == AF_INET6)
err = neigh_xmit(NEIGH_ND_TABLE, out_dev, &rt->rt_gw6,
skb);
} else if (rt6) {
if (ipv6_addr_v4mapped(&rt6->rt6i_gateway)) {
/* 6PE (RFC 4798) */
err = neigh_xmit(NEIGH_ARP_TABLE, out_dev, &rt6->rt6i_gateway.s6_addr32[3],
skb);
} else
err = neigh_xmit(NEIGH_ND_TABLE, out_dev, &rt6->rt6i_gateway,
skb);
}
if (err)
net_dbg_ratelimited("%s: packet transmission failed: %d\n",
__func__, err);
return LWTUNNEL_XMIT_DONE;
drop:
out_mdev = out_dev ? mpls_dev_get(out_dev) : NULL;
if (out_mdev)
MPLS_INC_STATS(out_mdev, tx_errors);
kfree_skb(skb);
return -EINVAL;
}
static int mpls_build_state(struct nlattr *nla,
unsigned int family, const void *cfg,
struct lwtunnel_state **ts,
struct netlink_ext_ack *extack)
{
struct mpls_iptunnel_encap *tun_encap_info;
struct nlattr *tb[MPLS_IPTUNNEL_MAX + 1];
struct lwtunnel_state *newts;
u8 n_labels;
int ret;
ret = nla_parse_nested_deprecated(tb, MPLS_IPTUNNEL_MAX, nla,
mpls_iptunnel_policy, extack);
if (ret < 0)
return ret;
if (!tb[MPLS_IPTUNNEL_DST]) {
NL_SET_ERR_MSG(extack, "MPLS_IPTUNNEL_DST attribute is missing");
return -EINVAL;
}
/* determine number of labels */
if (nla_get_labels(tb[MPLS_IPTUNNEL_DST], MAX_NEW_LABELS,
&n_labels, NULL, extack))
return -EINVAL;
newts = lwtunnel_state_alloc(struct_size(tun_encap_info, label,
n_labels));
if (!newts)
return -ENOMEM;
tun_encap_info = mpls_lwtunnel_encap(newts);
ret = nla_get_labels(tb[MPLS_IPTUNNEL_DST], n_labels,
&tun_encap_info->labels, tun_encap_info->label,
extack);
if (ret)
goto errout;
tun_encap_info->ttl_propagate = MPLS_TTL_PROP_DEFAULT;
if (tb[MPLS_IPTUNNEL_TTL]) {
tun_encap_info->default_ttl = nla_get_u8(tb[MPLS_IPTUNNEL_TTL]);
/* TTL 0 implies propagate from IP header */
tun_encap_info->ttl_propagate = tun_encap_info->default_ttl ?
MPLS_TTL_PROP_DISABLED :
MPLS_TTL_PROP_ENABLED;
}
newts->type = LWTUNNEL_ENCAP_MPLS;
newts->flags |= LWTUNNEL_STATE_XMIT_REDIRECT;
newts->headroom = mpls_encap_size(tun_encap_info);
*ts = newts;
return 0;
errout:
kfree(newts);
*ts = NULL;
return ret;
}
static int mpls_fill_encap_info(struct sk_buff *skb,
struct lwtunnel_state *lwtstate)
{
struct mpls_iptunnel_encap *tun_encap_info;
tun_encap_info = mpls_lwtunnel_encap(lwtstate);
if (nla_put_labels(skb, MPLS_IPTUNNEL_DST, tun_encap_info->labels,
tun_encap_info->label))
goto nla_put_failure;
if (tun_encap_info->ttl_propagate != MPLS_TTL_PROP_DEFAULT &&
nla_put_u8(skb, MPLS_IPTUNNEL_TTL, tun_encap_info->default_ttl))
goto nla_put_failure;
return 0;
nla_put_failure:
return -EMSGSIZE;
}
static int mpls_encap_nlsize(struct lwtunnel_state *lwtstate)
{
struct mpls_iptunnel_encap *tun_encap_info;
int nlsize;
tun_encap_info = mpls_lwtunnel_encap(lwtstate);
nlsize = nla_total_size(tun_encap_info->labels * 4);
if (tun_encap_info->ttl_propagate != MPLS_TTL_PROP_DEFAULT)
nlsize += nla_total_size(1);
return nlsize;
}
static int mpls_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
{
struct mpls_iptunnel_encap *a_hdr = mpls_lwtunnel_encap(a);
struct mpls_iptunnel_encap *b_hdr = mpls_lwtunnel_encap(b);
int l;
if (a_hdr->labels != b_hdr->labels ||
a_hdr->ttl_propagate != b_hdr->ttl_propagate ||
a_hdr->default_ttl != b_hdr->default_ttl)
return 1;
for (l = 0; l < a_hdr->labels; l++)
if (a_hdr->label[l] != b_hdr->label[l])
return 1;
return 0;
}
static const struct lwtunnel_encap_ops mpls_iptun_ops = {
.build_state = mpls_build_state,
.xmit = mpls_xmit,
.fill_encap = mpls_fill_encap_info,
.get_encap_size = mpls_encap_nlsize,
.cmp_encap = mpls_encap_cmp,
.owner = THIS_MODULE,
};
static int __init mpls_iptunnel_init(void)
{
return lwtunnel_encap_add_ops(&mpls_iptun_ops, LWTUNNEL_ENCAP_MPLS);
}
module_init(mpls_iptunnel_init);
static void __exit mpls_iptunnel_exit(void)
{
lwtunnel_encap_del_ops(&mpls_iptun_ops, LWTUNNEL_ENCAP_MPLS);
}
module_exit(mpls_iptunnel_exit);
MODULE_ALIAS_RTNL_LWT(MPLS);
MODULE_DESCRIPTION("MultiProtocol Label Switching IP Tunnels");
MODULE_LICENSE("GPL v2");
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