Commit bf355b8d authored by David Lebrun's avatar David Lebrun Committed by David S. Miller
Browse files

ipv6: sr: add core files for SR HMAC support



This patch adds the necessary functions to compute and check the HMAC signature
of an SR-enabled packet. Two HMAC algorithms are supported: hmac(sha1) and
hmac(sha256).

In order to avoid dynamic memory allocation for each HMAC computation,
a per-cpu ring buffer is allocated for this purpose.

A new per-interface sysctl called seg6_require_hmac is added, allowing a
user-defined policy for processing HMAC-signed SR-enabled packets.
A value of -1 means that the HMAC field will always be ignored.
A value of 0 means that if an HMAC field is present, its validity will
be enforced (the packet is dropped is the signature is incorrect).
Finally, a value of 1 means that any SR-enabled packet that does not
contain an HMAC signature or whose signature is incorrect will be dropped.
Signed-off-by: default avatarDavid Lebrun <david.lebrun@uclouvain.be>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 6c8702c6
......@@ -65,6 +65,9 @@ struct ipv6_devconf {
__s32 use_oif_addrs_only;
__s32 keep_addr_on_down;
__s32 seg6_enabled;
#ifdef CONFIG_IPV6_SEG6_HMAC
__s32 seg6_require_hmac;
#endif
struct ctl_table_header *sysctl_header;
};
......
#ifndef _LINUX_SEG6_HMAC_H
#define _LINUX_SEG6_HMAC_H
#include <uapi/linux/seg6_hmac.h>
#endif
......@@ -18,6 +18,7 @@
#include <linux/ipv6.h>
#include <net/lwtunnel.h>
#include <linux/seg6.h>
#include <linux/rhashtable.h>
static inline void update_csum_diff4(struct sk_buff *skb, __be32 from,
__be32 to)
......@@ -41,6 +42,9 @@ static inline void update_csum_diff16(struct sk_buff *skb, __be32 *from,
struct seg6_pernet_data {
struct mutex lock;
struct in6_addr __rcu *tun_src;
#ifdef CONFIG_IPV6_SEG6_HMAC
struct rhashtable hmac_infos;
#endif
};
static inline struct seg6_pernet_data *seg6_pernet(struct net *net)
......
/*
* SR-IPv6 implementation
*
* Author:
* David Lebrun <david.lebrun@uclouvain.be>
*
*
* 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.
*/
#ifndef _NET_SEG6_HMAC_H
#define _NET_SEG6_HMAC_H
#include <net/flow.h>
#include <net/ip6_fib.h>
#include <net/sock.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/route.h>
#include <net/seg6.h>
#include <linux/seg6_hmac.h>
#include <linux/rhashtable.h>
#define SEG6_HMAC_MAX_DIGESTSIZE 160
#define SEG6_HMAC_RING_SIZE 256
struct seg6_hmac_info {
struct rhash_head node;
struct rcu_head rcu;
u32 hmackeyid;
char secret[SEG6_HMAC_SECRET_LEN];
u8 slen;
u8 alg_id;
};
struct seg6_hmac_algo {
u8 alg_id;
char name[64];
struct crypto_shash * __percpu *tfms;
struct shash_desc * __percpu *shashs;
};
extern int seg6_hmac_compute(struct seg6_hmac_info *hinfo,
struct ipv6_sr_hdr *hdr, struct in6_addr *saddr,
u8 *output);
extern struct seg6_hmac_info *seg6_hmac_info_lookup(struct net *net, u32 key);
extern int seg6_hmac_info_add(struct net *net, u32 key,
struct seg6_hmac_info *hinfo);
extern int seg6_hmac_info_del(struct net *net, u32 key);
extern int seg6_push_hmac(struct net *net, struct in6_addr *saddr,
struct ipv6_sr_hdr *srh);
extern bool seg6_hmac_validate_skb(struct sk_buff *skb);
extern int seg6_hmac_init(void);
extern void seg6_hmac_exit(void);
extern int seg6_hmac_net_init(struct net *net);
extern void seg6_hmac_net_exit(struct net *net);
#endif
......@@ -180,6 +180,7 @@ enum {
DEVCONF_KEEP_ADDR_ON_DOWN,
DEVCONF_RTR_SOLICIT_MAX_INTERVAL,
DEVCONF_SEG6_ENABLED,
DEVCONF_SEG6_REQUIRE_HMAC,
DEVCONF_MAX
};
......
#ifndef _UAPI_LINUX_SEG6_HMAC_H
#define _UAPI_LINUX_SEG6_HMAC_H
#include <linux/seg6.h>
#define SEG6_HMAC_SECRET_LEN 64
#define SEG6_HMAC_FIELD_LEN 32
struct sr6_tlv_hmac {
struct sr6_tlv tlvhdr;
__u16 reserved;
__be32 hmackeyid;
__u8 hmac[SEG6_HMAC_FIELD_LEN];
};
enum {
SEG6_HMAC_ALGO_SHA1 = 1,
SEG6_HMAC_ALGO_SHA256 = 2,
};
#endif
......@@ -301,4 +301,16 @@ config IPV6_SEG6_INLINE
If unsure, say N.
config IPV6_SEG6_HMAC
bool "IPv6: Segment Routing HMAC support"
depends on IPV6
select CRYPTO_HMAC
select CRYPTO_SHA1
select CRYPTO_SHA256
---help---
Support for HMAC signature generation and verification
of SR-enabled packets.
If unsure, say N.
endif # IPV6
......@@ -44,6 +44,7 @@ obj-$(CONFIG_IPV6_SIT) += sit.o
obj-$(CONFIG_IPV6_TUNNEL) += ip6_tunnel.o
obj-$(CONFIG_IPV6_GRE) += ip6_gre.o
obj-$(CONFIG_IPV6_FOU) += fou6.o
obj-$(CONFIG_IPV6_SEG6_HMAC) += seg6_hmac.o
obj-y += addrconf_core.o exthdrs_core.o ip6_checksum.o ip6_icmp.o
obj-$(CONFIG_INET) += output_core.o protocol.o $(ipv6-offload)
......
......@@ -239,6 +239,9 @@ static struct ipv6_devconf ipv6_devconf __read_mostly = {
.ignore_routes_with_linkdown = 0,
.keep_addr_on_down = 0,
.seg6_enabled = 0,
#ifdef CONFIG_IPV6_SEG6_HMAC
.seg6_require_hmac = 0,
#endif
};
static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
......@@ -286,6 +289,9 @@ static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
.ignore_routes_with_linkdown = 0,
.keep_addr_on_down = 0,
.seg6_enabled = 0,
#ifdef CONFIG_IPV6_SEG6_HMAC
.seg6_require_hmac = 0,
#endif
};
/* Check if a valid qdisc is available */
......@@ -4947,6 +4953,9 @@ static inline void ipv6_store_devconf(struct ipv6_devconf *cnf,
array[DEVCONF_DROP_UNSOLICITED_NA] = cnf->drop_unsolicited_na;
array[DEVCONF_KEEP_ADDR_ON_DOWN] = cnf->keep_addr_on_down;
array[DEVCONF_SEG6_ENABLED] = cnf->seg6_enabled;
#ifdef CONFIG_IPV6_SEG6_HMAC
array[DEVCONF_SEG6_REQUIRE_HMAC] = cnf->seg6_require_hmac;
#endif
}
static inline size_t inet6_ifla6_size(void)
......@@ -6045,6 +6054,15 @@ static const struct ctl_table addrconf_sysctl[] = {
.mode = 0644,
.proc_handler = proc_dointvec,
},
#ifdef CONFIG_IPV6_SEG6_HMAC
{
.procname = "seg6_require_hmac",
.data = &ipv6_devconf.seg6_require_hmac,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec,
},
#endif
{
/* sentinel */
}
......
/*
* SR-IPv6 implementation -- HMAC functions
*
* Author:
* David Lebrun <david.lebrun@uclouvain.be>
*
*
* 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/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/netdevice.h>
#include <linux/in6.h>
#include <linux/icmpv6.h>
#include <linux/mroute6.h>
#include <linux/slab.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv6.h>
#include <net/sock.h>
#include <net/snmp.h>
#include <net/ipv6.h>
#include <net/protocol.h>
#include <net/transp_v6.h>
#include <net/rawv6.h>
#include <net/ndisc.h>
#include <net/ip6_route.h>
#include <net/addrconf.h>
#include <net/xfrm.h>
#include <linux/cryptohash.h>
#include <crypto/hash.h>
#include <crypto/sha.h>
#include <net/seg6.h>
#include <net/genetlink.h>
#include <net/seg6_hmac.h>
#include <linux/random.h>
static char * __percpu *hmac_ring;
static int seg6_hmac_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
{
const struct seg6_hmac_info *hinfo = obj;
return (hinfo->hmackeyid != *(__u32 *)arg->key);
}
static inline void seg6_hinfo_release(struct seg6_hmac_info *hinfo)
{
kfree_rcu(hinfo, rcu);
}
static void seg6_free_hi(void *ptr, void *arg)
{
struct seg6_hmac_info *hinfo = (struct seg6_hmac_info *)ptr;
if (hinfo)
seg6_hinfo_release(hinfo);
}
static const struct rhashtable_params rht_params = {
.head_offset = offsetof(struct seg6_hmac_info, node),
.key_offset = offsetof(struct seg6_hmac_info, hmackeyid),
.key_len = sizeof(u32),
.automatic_shrinking = true,
.obj_cmpfn = seg6_hmac_cmpfn,
};
static struct seg6_hmac_algo hmac_algos[] = {
{
.alg_id = SEG6_HMAC_ALGO_SHA1,
.name = "hmac(sha1)",
},
{
.alg_id = SEG6_HMAC_ALGO_SHA256,
.name = "hmac(sha256)",
},
};
static struct sr6_tlv_hmac *seg6_get_tlv_hmac(struct ipv6_sr_hdr *srh)
{
struct sr6_tlv_hmac *tlv;
if (srh->hdrlen < (srh->first_segment + 1) * 2 + 5)
return NULL;
if (!sr_has_hmac(srh))
return NULL;
tlv = (struct sr6_tlv_hmac *)
((char *)srh + ((srh->hdrlen + 1) << 3) - 40);
if (tlv->tlvhdr.type != SR6_TLV_HMAC || tlv->tlvhdr.len != 38)
return NULL;
return tlv;
}
static struct seg6_hmac_algo *__hmac_get_algo(u8 alg_id)
{
struct seg6_hmac_algo *algo;
int i, alg_count;
alg_count = sizeof(hmac_algos) / sizeof(struct seg6_hmac_algo);
for (i = 0; i < alg_count; i++) {
algo = &hmac_algos[i];
if (algo->alg_id == alg_id)
return algo;
}
return NULL;
}
static int __do_hmac(struct seg6_hmac_info *hinfo, const char *text, u8 psize,
u8 *output, int outlen)
{
struct seg6_hmac_algo *algo;
struct crypto_shash *tfm;
struct shash_desc *shash;
int ret, dgsize;
algo = __hmac_get_algo(hinfo->alg_id);
if (!algo)
return -ENOENT;
tfm = *this_cpu_ptr(algo->tfms);
dgsize = crypto_shash_digestsize(tfm);
if (dgsize > outlen) {
pr_debug("sr-ipv6: __do_hmac: digest size too big (%d / %d)\n",
dgsize, outlen);
return -ENOMEM;
}
ret = crypto_shash_setkey(tfm, hinfo->secret, hinfo->slen);
if (ret < 0) {
pr_debug("sr-ipv6: crypto_shash_setkey failed: err %d\n", ret);
goto failed;
}
shash = *this_cpu_ptr(algo->shashs);
shash->tfm = tfm;
ret = crypto_shash_digest(shash, text, psize, output);
if (ret < 0) {
pr_debug("sr-ipv6: crypto_shash_digest failed: err %d\n", ret);
goto failed;
}
return dgsize;
failed:
return ret;
}
int seg6_hmac_compute(struct seg6_hmac_info *hinfo, struct ipv6_sr_hdr *hdr,
struct in6_addr *saddr, u8 *output)
{
__be32 hmackeyid = cpu_to_be32(hinfo->hmackeyid);
u8 tmp_out[SEG6_HMAC_MAX_DIGESTSIZE];
int plen, i, dgsize, wrsize;
char *ring, *off;
/* a 160-byte buffer for digest output allows to store highest known
* hash function (RadioGatun) with up to 1216 bits
*/
/* saddr(16) + first_seg(1) + cleanup(1) + keyid(4) + seglist(16n) */
plen = 16 + 1 + 1 + 4 + (hdr->first_segment + 1) * 16;
/* this limit allows for 14 segments */
if (plen >= SEG6_HMAC_RING_SIZE)
return -EMSGSIZE;
/* Let's build the HMAC text on the ring buffer. The text is composed
* as follows, in order:
*
* 1. Source IPv6 address (128 bits)
* 2. first_segment value (8 bits)
* 3. cleanup flag (8 bits: highest bit is cleanup value, others are 0)
* 4. HMAC Key ID (32 bits)
* 5. All segments in the segments list (n * 128 bits)
*/
local_bh_disable();
ring = *this_cpu_ptr(hmac_ring);
off = ring;
/* source address */
memcpy(off, saddr, 16);
off += 16;
/* first_segment value */
*off++ = hdr->first_segment;
/* cleanup flag */
*off++ = !!(sr_has_cleanup(hdr)) << 7;
/* HMAC Key ID */
memcpy(off, &hmackeyid, 4);
off += 4;
/* all segments in the list */
for (i = 0; i < hdr->first_segment + 1; i++) {
memcpy(off, hdr->segments + i, 16);
off += 16;
}
dgsize = __do_hmac(hinfo, ring, plen, tmp_out,
SEG6_HMAC_MAX_DIGESTSIZE);
local_bh_enable();
if (dgsize < 0)
return dgsize;
wrsize = SEG6_HMAC_FIELD_LEN;
if (wrsize > dgsize)
wrsize = dgsize;
memset(output, 0, SEG6_HMAC_FIELD_LEN);
memcpy(output, tmp_out, wrsize);
return 0;
}
EXPORT_SYMBOL(seg6_hmac_compute);
/* checks if an incoming SR-enabled packet's HMAC status matches
* the incoming policy.
*
* called with rcu_read_lock()
*/
bool seg6_hmac_validate_skb(struct sk_buff *skb)
{
u8 hmac_output[SEG6_HMAC_FIELD_LEN];
struct net *net = dev_net(skb->dev);
struct seg6_hmac_info *hinfo;
struct sr6_tlv_hmac *tlv;
struct ipv6_sr_hdr *srh;
struct inet6_dev *idev;
idev = __in6_dev_get(skb->dev);
srh = (struct ipv6_sr_hdr *)skb_transport_header(skb);
tlv = seg6_get_tlv_hmac(srh);
/* mandatory check but no tlv */
if (idev->cnf.seg6_require_hmac > 0 && !tlv)
return false;
/* no check */
if (idev->cnf.seg6_require_hmac < 0)
return true;
/* check only if present */
if (idev->cnf.seg6_require_hmac == 0 && !tlv)
return true;
/* now, seg6_require_hmac >= 0 && tlv */
hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
if (!hinfo)
return false;
if (seg6_hmac_compute(hinfo, srh, &ipv6_hdr(skb)->saddr, hmac_output))
return false;
if (memcmp(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN) != 0)
return false;
return true;
}
EXPORT_SYMBOL(seg6_hmac_validate_skb);
/* called with rcu_read_lock() */
struct seg6_hmac_info *seg6_hmac_info_lookup(struct net *net, u32 key)
{
struct seg6_pernet_data *sdata = seg6_pernet(net);
struct seg6_hmac_info *hinfo;
hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
return hinfo;
}
EXPORT_SYMBOL(seg6_hmac_info_lookup);
int seg6_hmac_info_add(struct net *net, u32 key, struct seg6_hmac_info *hinfo)
{
struct seg6_pernet_data *sdata = seg6_pernet(net);
int err;
err = rhashtable_lookup_insert_fast(&sdata->hmac_infos, &hinfo->node,
rht_params);
return err;
}
EXPORT_SYMBOL(seg6_hmac_info_add);
int seg6_hmac_info_del(struct net *net, u32 key)
{
struct seg6_pernet_data *sdata = seg6_pernet(net);
struct seg6_hmac_info *hinfo;
int err = -ENOENT;
hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
if (!hinfo)
goto out;
err = rhashtable_remove_fast(&sdata->hmac_infos, &hinfo->node,
rht_params);
if (err)
goto out;
seg6_hinfo_release(hinfo);
out:
return err;
}
EXPORT_SYMBOL(seg6_hmac_info_del);
int seg6_push_hmac(struct net *net, struct in6_addr *saddr,
struct ipv6_sr_hdr *srh)
{
struct seg6_hmac_info *hinfo;
struct sr6_tlv_hmac *tlv;
int err = -ENOENT;
tlv = seg6_get_tlv_hmac(srh);
if (!tlv)
return -EINVAL;
rcu_read_lock();
hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
if (!hinfo)
goto out;
memset(tlv->hmac, 0, SEG6_HMAC_FIELD_LEN);
err = seg6_hmac_compute(hinfo, srh, saddr, tlv->hmac);
out:
rcu_read_unlock();
return err;
}
EXPORT_SYMBOL(seg6_push_hmac);
static int seg6_hmac_init_ring(void)
{
int i;
hmac_ring = alloc_percpu(char *);
if (!hmac_ring)
return -ENOMEM;
for_each_possible_cpu(i) {
char *ring = kzalloc(SEG6_HMAC_RING_SIZE, GFP_KERNEL);
if (!ring)
return -ENOMEM;
*per_cpu_ptr(hmac_ring, i) = ring;
}
return 0;
}
static int seg6_hmac_init_algo(void)
{
struct seg6_hmac_algo *algo;
struct crypto_shash *tfm;
struct shash_desc *shash;
int i, alg_count, cpu;
alg_count = sizeof(hmac_algos) / sizeof(struct seg6_hmac_algo);
for (i = 0; i < alg_count; i++) {
struct crypto_shash **p_tfm;
int shsize;
algo = &hmac_algos[i];
algo->tfms = alloc_percpu(struct crypto_shash *);
if (!algo->tfms)
return -ENOMEM;
for_each_possible_cpu(cpu) {
tfm = crypto_alloc_shash(algo->name, 0, GFP_KERNEL);
if (IS_ERR(tfm))
return PTR_ERR(tfm);
p_tfm = per_cpu_ptr(algo->tfms, cpu);
*p_tfm = tfm;
}
p_tfm = this_cpu_ptr(algo->tfms);
tfm = *p_tfm;
shsize = sizeof(*shash) + crypto_shash_descsize(tfm);
algo->shashs = alloc_percpu(struct shash_desc *);
if (!algo->shashs)
return -ENOMEM;
for_each_possible_cpu(cpu) {
shash = kzalloc(shsize, GFP_KERNEL);
if (!shash)
return -ENOMEM;
*per_cpu_ptr(algo->shashs, cpu) = shash;
}
}
return 0;
}
int __init seg6_hmac_init(void)
{
int ret;
ret = seg6_hmac_init_ring();
if (ret < 0)
goto out;
ret = seg6_hmac_init_algo();
out: