[IPV6]: Disallow RH0 by default.

A security issue is emerging.  Disallow Routing Header Type 0 by default
as we have been doing for IPv4.
Note: We allow RH2 by default because it is harmless.
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/ip-sysctl.txt

@@ -851,6 +851,15 @@ accept_redirects - BOOLEAN
 	Functional default: enabled if local forwarding is disabled.
 			    disabled if local forwarding is enabled.
 
+accept_source_route - INTEGER
+	Accept source routing (routing extension header).
+
+	> 0: Accept routing header.
+	= 0: Accept only routing header type 2.
+	< 0: Do not accept routing header.
+
+	Default: 0
+
 autoconf - BOOLEAN
 	Autoconfigure addresses using Prefix Information in Router 
 	Advertisements.

include/linux/ipv6.h

@@ -177,6 +177,7 @@ struct ipv6_devconf {
 #endif
 #endif
 	__s32		proxy_ndp;
+	__s32		accept_source_route;
 	void		*sysctl;
 };
 
@@ -205,6 +206,8 @@ enum {
 	DEVCONF_RTR_PROBE_INTERVAL,
 	DEVCONF_ACCEPT_RA_RT_INFO_MAX_PLEN,
 	DEVCONF_PROXY_NDP,
+	__DEVCONF_OPTIMISTIC_DAD,
+	DEVCONF_ACCEPT_SOURCE_ROUTE,
 	DEVCONF_MAX
 };
 

include/linux/sysctl.h

@@ -580,6 +580,7 @@ enum {
 	NET_IPV6_RTR_PROBE_INTERVAL=21,
 	NET_IPV6_ACCEPT_RA_RT_INFO_MAX_PLEN=22,
 	NET_IPV6_PROXY_NDP=23,
+	NET_IPV6_ACCEPT_SOURCE_ROUTE=25,
 	__NET_IPV6_MAX
 };
 

net/ipv6/addrconf.c

@@ -172,6 +172,7 @@ struct ipv6_devconf ipv6_devconf __read_mostly = {
 #endif
 #endif
 	.proxy_ndp		= 0,
+	.accept_source_route	= 0,	/* we do not accept RH0 by default. */
 };
 
 static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
@@ -203,6 +204,7 @@ static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
 #endif
 #endif
 	.proxy_ndp		= 0,
+	.accept_source_route	= 0,	/* we do not accept RH0 by default. */
 };
 
 /* IPv6 Wildcard Address and Loopback Address defined by RFC2553 */
@@ -3356,6 +3358,7 @@ static inline void ipv6_store_devconf(struct ipv6_devconf *cnf,
 #endif
 #endif
 	array[DEVCONF_PROXY_NDP] = cnf->proxy_ndp;
+	array[DEVCONF_ACCEPT_SOURCE_ROUTE] = cnf->accept_source_route;
 }
 
 static inline size_t inet6_if_nlmsg_size(void)
@@ -3883,6 +3886,14 @@ static struct addrconf_sysctl_table
 			.mode		=	0644,
 			.proc_handler	=	&proc_dointvec,
 		},
+		{
+			.ctl_name	=	NET_IPV6_ACCEPT_SOURCE_ROUTE,
+			.procname	=	"accept_source_route",
+			.data		=	&ipv6_devconf.accept_source_route,
+			.maxlen		=	sizeof(int),
+			.mode		=	0644,
+			.proc_handler	=	&proc_dointvec,
+		},
 		{
 			.ctl_name	=	0,	/* sentinel */
 		}

net/ipv6/exthdrs.c

@@ -362,10 +362,27 @@ static int ipv6_rthdr_rcv(struct sk_buff **skbp)
 	struct inet6_skb_parm *opt = IP6CB(skb);
 	struct in6_addr *addr = NULL;
 	struct in6_addr daddr;
+	struct inet6_dev *idev;
 	int n, i;
-
 	struct ipv6_rt_hdr *hdr;
 	struct rt0_hdr *rthdr;
+	int accept_source_route = ipv6_devconf.accept_source_route;
+
+	if (accept_source_route < 0 ||
+	    ((idev = in6_dev_get(skb->dev)) == NULL)) {
+		kfree_skb(skb);
+		return -1;
+	}
+	if (idev->cnf.accept_source_route < 0) {
+		in6_dev_put(idev);
+		kfree_skb(skb);
+		return -1;
+	}
+
+	if (accept_source_route > idev->cnf.accept_source_route)
+		accept_source_route = idev->cnf.accept_source_route;
+
+	in6_dev_put(idev);
 
 	if (!pskb_may_pull(skb, (skb->h.raw-skb->data)+8) ||
 	    !pskb_may_pull(skb, (skb->h.raw-skb->data)+((skb->h.raw[1]+1)<<3))) {
@@ -377,6 +394,22 @@ static int ipv6_rthdr_rcv(struct sk_buff **skbp)
 
 	hdr = (struct ipv6_rt_hdr *) skb->h.raw;
 
+	switch (hdr->type) {
+#ifdef CONFIG_IPV6_MIP6
+		break;
+#endif
+	case IPV6_SRCRT_TYPE_0:
+		if (accept_source_route <= 0)
+			break;
+		kfree_skb(skb);
+		return -1;
+	default:
+		IP6_INC_STATS_BH(ip6_dst_idev(skb->dst),
+				 IPSTATS_MIB_INHDRERRORS);
+		icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, (&hdr->type) - skb->nh.raw);
+		return -1;
+	}
+
 	if (ipv6_addr_is_multicast(&skb->nh.ipv6h->daddr) ||
 	    skb->pkt_type != PACKET_HOST) {
 		IP6_INC_STATS_BH(ip6_dst_idev(skb->dst),
@@ -434,11 +467,6 @@ looped_back:
 		}
 		break;
 #endif
-	default:
-		IP6_INC_STATS_BH(ip6_dst_idev(skb->dst),
-				 IPSTATS_MIB_INHDRERRORS);
-		icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, (&hdr->type) - skb->nh.raw);
-		return -1;
 	}
 
 	/*