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: David Lebrun <david.lebrun@uclouvain.be>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/ipv6.h

@@ -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;
 };

include/linux/seg6_hmac.h

@@ -0,0 +1,6 @@
+#ifndef _LINUX_SEG6_HMAC_H
+#define _LINUX_SEG6_HMAC_H
+
+#include <uapi/linux/seg6_hmac.h>
+
+#endif

include/net/seg6.h

@@ -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)

include/net/seg6_hmac.h

@@ -0,0 +1,62 @@
+/*
+ *  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

include/uapi/linux/ipv6.h

@@ -180,6 +180,7 @@ enum {
 	DEVCONF_KEEP_ADDR_ON_DOWN,
 	DEVCONF_RTR_SOLICIT_MAX_INTERVAL,
 	DEVCONF_SEG6_ENABLED,
+	DEVCONF_SEG6_REQUIRE_HMAC,
 	DEVCONF_MAX
 };
 

include/uapi/linux/seg6_hmac.h

@@ -0,0 +1,21 @@
+#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

net/ipv6/Kconfig

@@ -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

net/ipv6/Makefile

@@ -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)

net/ipv6/addrconf.c

@@ -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 */
 	}