From 87c48fa3b4630905f98268dde838ee43626a060c Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 21 Jul 2011 21:25:58 -0700 Subject: [PATCH] ipv6: make fragment identifications less predictable IPv6 fragment identification generation is way beyond what we use for IPv4 : It uses a single generator. Its not scalable and allows DOS attacks. Now inetpeer is IPv6 aware, we can use it to provide a more secure and scalable frag ident generator (per destination, instead of system wide) This patch : 1) defines a new secure_ipv6_id() helper 2) extends inet_getid() to provide 32bit results 3) extends ipv6_select_ident() with a new dest parameter Reported-by: Fernando Gont Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- drivers/char/random.c | 15 +++++++++++++++ include/linux/random.h | 1 + include/net/inetpeer.h | 13 ++++++++++--- include/net/ipv6.h | 12 +----------- net/ipv4/inetpeer.c | 7 +++++-- net/ipv6/ip6_output.c | 36 +++++++++++++++++++++++++++++++----- net/ipv6/udp.c | 2 +- 7 files changed, 64 insertions(+), 22 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index d4ddeba56682..729281961f22 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1523,6 +1523,21 @@ __u32 secure_ip_id(__be32 daddr) return half_md4_transform(hash, keyptr->secret); } +__u32 secure_ipv6_id(const __be32 daddr[4]) +{ + const struct keydata *keyptr; + __u32 hash[4]; + + keyptr = get_keyptr(); + + hash[0] = (__force __u32)daddr[0]; + hash[1] = (__force __u32)daddr[1]; + hash[2] = (__force __u32)daddr[2]; + hash[3] = (__force __u32)daddr[3]; + + return half_md4_transform(hash, keyptr->secret); +} + #ifdef CONFIG_INET __u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr, diff --git a/include/linux/random.h b/include/linux/random.h index fb7ab9de5f36..ce29a040c8dc 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -58,6 +58,7 @@ extern void get_random_bytes(void *buf, int nbytes); void generate_random_uuid(unsigned char uuid_out[16]); extern __u32 secure_ip_id(__be32 daddr); +extern __u32 secure_ipv6_id(const __be32 daddr[4]); extern u32 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport); extern u32 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr, __be16 dport); diff --git a/include/net/inetpeer.h b/include/net/inetpeer.h index 39d123081e7e..4233e6f9841d 100644 --- a/include/net/inetpeer.h +++ b/include/net/inetpeer.h @@ -71,7 +71,7 @@ static inline bool inet_metrics_new(const struct inet_peer *p) } /* can be called with or without local BH being disabled */ -struct inet_peer *inet_getpeer(struct inetpeer_addr *daddr, int create); +struct inet_peer *inet_getpeer(const struct inetpeer_addr *daddr, int create); static inline struct inet_peer *inet_getpeer_v4(__be32 v4daddr, int create) { @@ -106,11 +106,18 @@ static inline void inet_peer_refcheck(const struct inet_peer *p) /* can be called with or without local BH being disabled */ -static inline __u16 inet_getid(struct inet_peer *p, int more) +static inline int inet_getid(struct inet_peer *p, int more) { + int old, new; more++; inet_peer_refcheck(p); - return atomic_add_return(more, &p->ip_id_count) - more; + do { + old = atomic_read(&p->ip_id_count); + new = old + more; + if (!new) + new = 1; + } while (atomic_cmpxchg(&p->ip_id_count, old, new) != old); + return new; } #endif /* _NET_INETPEER_H */ diff --git a/include/net/ipv6.h b/include/net/ipv6.h index c033ed00df7d..3b5ac1fbff39 100644 --- a/include/net/ipv6.h +++ b/include/net/ipv6.h @@ -463,17 +463,7 @@ static inline int ipv6_addr_diff(const struct in6_addr *a1, const struct in6_add return __ipv6_addr_diff(a1, a2, sizeof(struct in6_addr)); } -static __inline__ void ipv6_select_ident(struct frag_hdr *fhdr) -{ - static u32 ipv6_fragmentation_id = 1; - static DEFINE_SPINLOCK(ip6_id_lock); - - spin_lock_bh(&ip6_id_lock); - fhdr->identification = htonl(ipv6_fragmentation_id); - if (++ipv6_fragmentation_id == 0) - ipv6_fragmentation_id = 1; - spin_unlock_bh(&ip6_id_lock); -} +extern void ipv6_select_ident(struct frag_hdr *fhdr, struct rt6_info *rt); /* * Prototypes exported by ipv6 diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c index 90c5f0d1bcf3..e38213817d0a 100644 --- a/net/ipv4/inetpeer.c +++ b/net/ipv4/inetpeer.c @@ -391,7 +391,7 @@ static int inet_peer_gc(struct inet_peer_base *base, return cnt; } -struct inet_peer *inet_getpeer(struct inetpeer_addr *daddr, int create) +struct inet_peer *inet_getpeer(const struct inetpeer_addr *daddr, int create) { struct inet_peer __rcu **stack[PEER_MAXDEPTH], ***stackptr; struct inet_peer_base *base = family_to_base(daddr->family); @@ -436,7 +436,10 @@ relookup: p->daddr = *daddr; atomic_set(&p->refcnt, 1); atomic_set(&p->rid, 0); - atomic_set(&p->ip_id_count, secure_ip_id(daddr->addr.a4)); + atomic_set(&p->ip_id_count, + (daddr->family == AF_INET) ? + secure_ip_id(daddr->addr.a4) : + secure_ipv6_id(daddr->addr.a6)); p->tcp_ts_stamp = 0; p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW; p->rate_tokens = 0; diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index 8db0e4875ad8..32e5339db0c8 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -596,6 +596,31 @@ int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr) return offset; } +void ipv6_select_ident(struct frag_hdr *fhdr, struct rt6_info *rt) +{ + static atomic_t ipv6_fragmentation_id; + int old, new; + + if (rt) { + struct inet_peer *peer; + + if (!rt->rt6i_peer) + rt6_bind_peer(rt, 1); + peer = rt->rt6i_peer; + if (peer) { + fhdr->identification = htonl(inet_getid(peer, 0)); + return; + } + } + do { + old = atomic_read(&ipv6_fragmentation_id); + new = old + 1; + if (!new) + new = 1; + } while (atomic_cmpxchg(&ipv6_fragmentation_id, old, new) != old); + fhdr->identification = htonl(new); +} + int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *)) { struct sk_buff *frag; @@ -680,7 +705,7 @@ int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *)) skb_reset_network_header(skb); memcpy(skb_network_header(skb), tmp_hdr, hlen); - ipv6_select_ident(fh); + ipv6_select_ident(fh, rt); fh->nexthdr = nexthdr; fh->reserved = 0; fh->frag_off = htons(IP6_MF); @@ -826,7 +851,7 @@ slow_path: fh->nexthdr = nexthdr; fh->reserved = 0; if (!frag_id) { - ipv6_select_ident(fh); + ipv6_select_ident(fh, rt); frag_id = fh->identification; } else fh->identification = frag_id; @@ -1076,7 +1101,8 @@ static inline int ip6_ufo_append_data(struct sock *sk, int getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb), void *from, int length, int hh_len, int fragheaderlen, - int transhdrlen, int mtu,unsigned int flags) + int transhdrlen, int mtu,unsigned int flags, + struct rt6_info *rt) { struct sk_buff *skb; @@ -1120,7 +1146,7 @@ static inline int ip6_ufo_append_data(struct sock *sk, skb_shinfo(skb)->gso_size = (mtu - fragheaderlen - sizeof(struct frag_hdr)) & ~7; skb_shinfo(skb)->gso_type = SKB_GSO_UDP; - ipv6_select_ident(&fhdr); + ipv6_select_ident(&fhdr, rt); skb_shinfo(skb)->ip6_frag_id = fhdr.identification; __skb_queue_tail(&sk->sk_write_queue, skb); @@ -1286,7 +1312,7 @@ int ip6_append_data(struct sock *sk, int getfrag(void *from, char *to, err = ip6_ufo_append_data(sk, getfrag, from, length, hh_len, fragheaderlen, - transhdrlen, mtu, flags); + transhdrlen, mtu, flags, rt); if (err) goto error; return 0; diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index 328985c40883..29213b51c499 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -1359,7 +1359,7 @@ static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb, u32 features) fptr = (struct frag_hdr *)(skb_network_header(skb) + unfrag_ip6hlen); fptr->nexthdr = nexthdr; fptr->reserved = 0; - ipv6_select_ident(fptr); + ipv6_select_ident(fptr, (struct rt6_info *)skb_dst(skb)); /* Fragment the skb. ipv6 header and the remaining fields of the * fragment header are updated in ipv6_gso_segment() -- 2.34.1