From 218774dc341f219bfcf940304a081b121a0e8099 Mon Sep 17 00:00:00 2001 From: Hannes Frederic Sowa Date: Tue, 29 Jan 2013 08:24:25 +0000 Subject: [PATCH] ipv6: add anti-spoofing checks for 6to4 and 6rd This patch adds anti-spoofing checks in sit.c as specified in RFC3964 section 5.2 for 6to4 and RFC5969 section 12 for 6rd. I left out the checks which could easily be implemented with netfilter. Specifically this patch adds following logic (based loosely on the pseudocode in RFC3964 section 5.2): if prefix (inner_src_v6) == rd6_prefix (2002::/16 is the default) and outer_src_v4 != embedded_ipv4 (inner_src_v6) drop if prefix (inner_dst_v6) == rd6_prefix (or 2002::/16 is the default) and outer_dst_v4 != embedded_ipv4 (inner_dst_v6) drop accept To accomplish the specified security checks proposed by above RFCs, it is still necessary to employ uRPF filters with netfilter. These new checks only kick in if the employed addresses are within the 2002::/16 or another range specified by the 6rd-prefix (which defaults to 2002::/16). Cc: YOSHIFUJI Hideaki Cc: David Miller Signed-off-by: Hannes Frederic Sowa Signed-off-by: David S. Miller --- net/ipv6/sit.c | 54 ++++++++++++++++++++++++++++++++++++++------------ 1 file changed, 41 insertions(+), 13 deletions(-) diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c index 98fe53694a65..02f96dcbcf02 100644 --- a/net/ipv6/sit.c +++ b/net/ipv6/sit.c @@ -72,6 +72,8 @@ MODULE_PARM_DESC(log_ecn_error, "Log packets received with corrupted ECN"); static int ipip6_tunnel_init(struct net_device *dev); static void ipip6_tunnel_setup(struct net_device *dev); static void ipip6_dev_free(struct net_device *dev); +static bool check_6rd(struct ip_tunnel *tunnel, const struct in6_addr *v6dst, + __be32 *v4dst); static struct rtnl_link_ops sit_link_ops __read_mostly; static int sit_net_id __read_mostly; @@ -590,6 +592,15 @@ out: return err; } +static inline bool is_spoofed_6rd(struct ip_tunnel *tunnel, const __be32 v4addr, + const struct in6_addr *v6addr) +{ + __be32 v4embed = 0; + if (check_6rd(tunnel, v6addr, &v4embed) && v4addr != v4embed) + return true; + return false; +} + static int ipip6_rcv(struct sk_buff *skb) { const struct iphdr *iph = ip_hdr(skb); @@ -608,10 +619,19 @@ static int ipip6_rcv(struct sk_buff *skb) skb->protocol = htons(ETH_P_IPV6); skb->pkt_type = PACKET_HOST; - if ((tunnel->dev->priv_flags & IFF_ISATAP) && - !isatap_chksrc(skb, iph, tunnel)) { - tunnel->dev->stats.rx_errors++; - goto out; + if (tunnel->dev->priv_flags & IFF_ISATAP) { + if (!isatap_chksrc(skb, iph, tunnel)) { + tunnel->dev->stats.rx_errors++; + goto out; + } + } else { + if (is_spoofed_6rd(tunnel, iph->saddr, + &ipv6_hdr(skb)->saddr) || + is_spoofed_6rd(tunnel, iph->daddr, + &ipv6_hdr(skb)->daddr)) { + tunnel->dev->stats.rx_errors++; + goto out; + } } __skb_tunnel_rx(skb, tunnel->dev); @@ -645,14 +665,12 @@ out: } /* - * Returns the embedded IPv4 address if the IPv6 address - * comes from 6rd / 6to4 (RFC 3056) addr space. + * If the IPv6 address comes from 6rd / 6to4 (RFC 3056) addr space this function + * stores the embedded IPv4 address in v4dst and returns true. */ -static inline -__be32 try_6rd(const struct in6_addr *v6dst, struct ip_tunnel *tunnel) +static bool check_6rd(struct ip_tunnel *tunnel, const struct in6_addr *v6dst, + __be32 *v4dst) { - __be32 dst = 0; - #ifdef CONFIG_IPV6_SIT_6RD if (ipv6_prefix_equal(v6dst, &tunnel->ip6rd.prefix, tunnel->ip6rd.prefixlen)) { @@ -671,14 +689,24 @@ __be32 try_6rd(const struct in6_addr *v6dst, struct ip_tunnel *tunnel) d |= ntohl(v6dst->s6_addr32[pbw0 + 1]) >> (32 - pbi1); - dst = tunnel->ip6rd.relay_prefix | htonl(d); + *v4dst = tunnel->ip6rd.relay_prefix | htonl(d); + return true; } #else if (v6dst->s6_addr16[0] == htons(0x2002)) { /* 6to4 v6 addr has 16 bits prefix, 32 v4addr, 16 SLA, ... */ - memcpy(&dst, &v6dst->s6_addr16[1], 4); + memcpy(v4dst, &v6dst->s6_addr16[1], 4); + return true; } #endif + return false; +} + +static inline __be32 try_6rd(struct ip_tunnel *tunnel, + const struct in6_addr *v6dst) +{ + __be32 dst = 0; + check_6rd(tunnel, v6dst, &dst); return dst; } @@ -739,7 +767,7 @@ static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb, } if (!dst) - dst = try_6rd(&iph6->daddr, tunnel); + dst = try_6rd(tunnel, &iph6->daddr); if (!dst) { struct neighbour *neigh = NULL; -- 2.20.1