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1 From: Pablo Neira Ayuso <pablo@netfilter.org>
2 Date: Sat, 30 Dec 2017 22:41:46 +0100
3 Subject: [PATCH] netfilter: remove defensive check on malformed packets from
4 raw sockets
5
6 Users cannot forge malformed IPv4/IPv6 headers via raw sockets that they
7 can inject into the stack. Specifically, not for IPv4 since 55888dfb6ba7
8 ("AF_RAW: Augment raw_send_hdrinc to expand skb to fit iphdr->ihl
9 (v2)"). IPv6 raw sockets also ensure that packets have a well-formed
10 IPv6 header available in the skbuff.
11
12 At quick glance, br_netfilter also validates layer 3 headers and it
13 drops malformed both IPv4 and IPv6 packets.
14
15 Therefore, let's remove this defensive check all over the place.
16
17 Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
18 ---
19
20 --- a/net/ipv4/netfilter/iptable_filter.c
21 +++ b/net/ipv4/netfilter/iptable_filter.c
22 @@ -38,12 +38,6 @@ static unsigned int
23 iptable_filter_hook(void *priv, struct sk_buff *skb,
24 const struct nf_hook_state *state)
25 {
26 - if (state->hook == NF_INET_LOCAL_OUT &&
27 - (skb->len < sizeof(struct iphdr) ||
28 - ip_hdrlen(skb) < sizeof(struct iphdr)))
29 - /* root is playing with raw sockets. */
30 - return NF_ACCEPT;
31 -
32 return ipt_do_table(skb, state, state->net->ipv4.iptable_filter);
33 }
34
35 --- a/net/ipv4/netfilter/iptable_mangle.c
36 +++ b/net/ipv4/netfilter/iptable_mangle.c
37 @@ -49,11 +49,6 @@ ipt_mangle_out(struct sk_buff *skb, cons
38 u_int32_t mark;
39 int err;
40
41 - /* root is playing with raw sockets. */
42 - if (skb->len < sizeof(struct iphdr) ||
43 - ip_hdrlen(skb) < sizeof(struct iphdr))
44 - return NF_ACCEPT;
45 -
46 /* Save things which could affect route */
47 mark = skb->mark;
48 iph = ip_hdr(skb);
49 --- a/net/ipv4/netfilter/iptable_raw.c
50 +++ b/net/ipv4/netfilter/iptable_raw.c
51 @@ -26,12 +26,6 @@ static unsigned int
52 iptable_raw_hook(void *priv, struct sk_buff *skb,
53 const struct nf_hook_state *state)
54 {
55 - if (state->hook == NF_INET_LOCAL_OUT &&
56 - (skb->len < sizeof(struct iphdr) ||
57 - ip_hdrlen(skb) < sizeof(struct iphdr)))
58 - /* root is playing with raw sockets. */
59 - return NF_ACCEPT;
60 -
61 return ipt_do_table(skb, state, state->net->ipv4.iptable_raw);
62 }
63
64 --- a/net/ipv4/netfilter/iptable_security.c
65 +++ b/net/ipv4/netfilter/iptable_security.c
66 @@ -43,12 +43,6 @@ static unsigned int
67 iptable_security_hook(void *priv, struct sk_buff *skb,
68 const struct nf_hook_state *state)
69 {
70 - if (state->hook == NF_INET_LOCAL_OUT &&
71 - (skb->len < sizeof(struct iphdr) ||
72 - ip_hdrlen(skb) < sizeof(struct iphdr)))
73 - /* Somebody is playing with raw sockets. */
74 - return NF_ACCEPT;
75 -
76 return ipt_do_table(skb, state, state->net->ipv4.iptable_security);
77 }
78
79 --- a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
80 +++ b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
81 @@ -154,11 +154,6 @@ static unsigned int ipv4_conntrack_local
82 struct sk_buff *skb,
83 const struct nf_hook_state *state)
84 {
85 - /* root is playing with raw sockets. */
86 - if (skb->len < sizeof(struct iphdr) ||
87 - ip_hdrlen(skb) < sizeof(struct iphdr))
88 - return NF_ACCEPT;
89 -
90 if (ip_is_fragment(ip_hdr(skb))) { /* IP_NODEFRAG setsockopt set */
91 enum ip_conntrack_info ctinfo;
92 struct nf_conn *tmpl;
93 --- a/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c
94 +++ b/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c
95 @@ -355,11 +355,6 @@ nf_nat_ipv4_out(void *priv, struct sk_bu
96 #endif
97 unsigned int ret;
98
99 - /* root is playing with raw sockets. */
100 - if (skb->len < sizeof(struct iphdr) ||
101 - ip_hdrlen(skb) < sizeof(struct iphdr))
102 - return NF_ACCEPT;
103 -
104 ret = nf_nat_ipv4_fn(priv, skb, state, do_chain);
105 #ifdef CONFIG_XFRM
106 if (ret != NF_DROP && ret != NF_STOLEN &&
107 @@ -395,11 +390,6 @@ nf_nat_ipv4_local_fn(void *priv, struct
108 unsigned int ret;
109 int err;
110
111 - /* root is playing with raw sockets. */
112 - if (skb->len < sizeof(struct iphdr) ||
113 - ip_hdrlen(skb) < sizeof(struct iphdr))
114 - return NF_ACCEPT;
115 -
116 ret = nf_nat_ipv4_fn(priv, skb, state, do_chain);
117 if (ret != NF_DROP && ret != NF_STOLEN &&
118 (ct = nf_ct_get(skb, &ctinfo)) != NULL) {
119 --- a/net/ipv4/netfilter/nf_tables_ipv4.c
120 +++ b/net/ipv4/netfilter/nf_tables_ipv4.c
121 @@ -30,21 +30,6 @@ static unsigned int nft_do_chain_ipv4(vo
122 return nft_do_chain(&pkt, priv);
123 }
124
125 -static unsigned int nft_ipv4_output(void *priv,
126 - struct sk_buff *skb,
127 - const struct nf_hook_state *state)
128 -{
129 - if (unlikely(skb->len < sizeof(struct iphdr) ||
130 - ip_hdr(skb)->ihl < sizeof(struct iphdr) / 4)) {
131 - if (net_ratelimit())
132 - pr_info("nf_tables_ipv4: ignoring short SOCK_RAW "
133 - "packet\n");
134 - return NF_ACCEPT;
135 - }
136 -
137 - return nft_do_chain_ipv4(priv, skb, state);
138 -}
139 -
140 static struct nft_af_info nft_af_ipv4 __read_mostly = {
141 .family = NFPROTO_IPV4,
142 .nhooks = NF_INET_NUMHOOKS,
143 @@ -91,7 +76,7 @@ static const struct nf_chain_type filter
144 (1 << NF_INET_POST_ROUTING),
145 .hooks = {
146 [NF_INET_LOCAL_IN] = nft_do_chain_ipv4,
147 - [NF_INET_LOCAL_OUT] = nft_ipv4_output,
148 + [NF_INET_LOCAL_OUT] = nft_do_chain_ipv4,
149 [NF_INET_FORWARD] = nft_do_chain_ipv4,
150 [NF_INET_PRE_ROUTING] = nft_do_chain_ipv4,
151 [NF_INET_POST_ROUTING] = nft_do_chain_ipv4,
152 --- a/net/ipv4/netfilter/nft_chain_route_ipv4.c
153 +++ b/net/ipv4/netfilter/nft_chain_route_ipv4.c
154 @@ -33,11 +33,6 @@ static unsigned int nf_route_table_hook(
155 const struct iphdr *iph;
156 int err;
157
158 - /* root is playing with raw sockets. */
159 - if (skb->len < sizeof(struct iphdr) ||
160 - ip_hdrlen(skb) < sizeof(struct iphdr))
161 - return NF_ACCEPT;
162 -
163 nft_set_pktinfo(&pkt, skb, state);
164 nft_set_pktinfo_ipv4(&pkt, skb);
165
166 --- a/net/ipv6/netfilter/ip6table_mangle.c
167 +++ b/net/ipv6/netfilter/ip6table_mangle.c
168 @@ -42,14 +42,6 @@ ip6t_mangle_out(struct sk_buff *skb, con
169 u_int8_t hop_limit;
170 u_int32_t flowlabel, mark;
171 int err;
172 -#if 0
173 - /* root is playing with raw sockets. */
174 - if (skb->len < sizeof(struct iphdr) ||
175 - ip_hdrlen(skb) < sizeof(struct iphdr)) {
176 - net_warn_ratelimited("ip6t_hook: happy cracking\n");
177 - return NF_ACCEPT;
178 - }
179 -#endif
180
181 /* save source/dest address, mark, hoplimit, flowlabel, priority, */
182 memcpy(&saddr, &ipv6_hdr(skb)->saddr, sizeof(saddr));
183 --- a/net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c
184 +++ b/net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c
185 @@ -176,11 +176,6 @@ static unsigned int ipv6_conntrack_local
186 struct sk_buff *skb,
187 const struct nf_hook_state *state)
188 {
189 - /* root is playing with raw sockets. */
190 - if (skb->len < sizeof(struct ipv6hdr)) {
191 - net_notice_ratelimited("ipv6_conntrack_local: packet too short\n");
192 - return NF_ACCEPT;
193 - }
194 return nf_conntrack_in(state->net, PF_INET6, state->hook, skb);
195 }
196
197 --- a/net/ipv6/netfilter/nf_nat_l3proto_ipv6.c
198 +++ b/net/ipv6/netfilter/nf_nat_l3proto_ipv6.c
199 @@ -372,10 +372,6 @@ nf_nat_ipv6_out(void *priv, struct sk_bu
200 #endif
201 unsigned int ret;
202
203 - /* root is playing with raw sockets. */
204 - if (skb->len < sizeof(struct ipv6hdr))
205 - return NF_ACCEPT;
206 -
207 ret = nf_nat_ipv6_fn(priv, skb, state, do_chain);
208 #ifdef CONFIG_XFRM
209 if (ret != NF_DROP && ret != NF_STOLEN &&
210 @@ -411,10 +407,6 @@ nf_nat_ipv6_local_fn(void *priv, struct
211 unsigned int ret;
212 int err;
213
214 - /* root is playing with raw sockets. */
215 - if (skb->len < sizeof(struct ipv6hdr))
216 - return NF_ACCEPT;
217 -
218 ret = nf_nat_ipv6_fn(priv, skb, state, do_chain);
219 if (ret != NF_DROP && ret != NF_STOLEN &&
220 (ct = nf_ct_get(skb, &ctinfo)) != NULL) {
221 --- a/net/ipv6/netfilter/nf_tables_ipv6.c
222 +++ b/net/ipv6/netfilter/nf_tables_ipv6.c
223 @@ -28,20 +28,6 @@ static unsigned int nft_do_chain_ipv6(vo
224 return nft_do_chain(&pkt, priv);
225 }
226
227 -static unsigned int nft_ipv6_output(void *priv,
228 - struct sk_buff *skb,
229 - const struct nf_hook_state *state)
230 -{
231 - if (unlikely(skb->len < sizeof(struct ipv6hdr))) {
232 - if (net_ratelimit())
233 - pr_info("nf_tables_ipv6: ignoring short SOCK_RAW "
234 - "packet\n");
235 - return NF_ACCEPT;
236 - }
237 -
238 - return nft_do_chain_ipv6(priv, skb, state);
239 -}
240 -
241 static struct nft_af_info nft_af_ipv6 __read_mostly = {
242 .family = NFPROTO_IPV6,
243 .nhooks = NF_INET_NUMHOOKS,
244 @@ -88,7 +74,7 @@ static const struct nf_chain_type filter
245 (1 << NF_INET_POST_ROUTING),
246 .hooks = {
247 [NF_INET_LOCAL_IN] = nft_do_chain_ipv6,
248 - [NF_INET_LOCAL_OUT] = nft_ipv6_output,
249 + [NF_INET_LOCAL_OUT] = nft_do_chain_ipv6,
250 [NF_INET_FORWARD] = nft_do_chain_ipv6,
251 [NF_INET_PRE_ROUTING] = nft_do_chain_ipv6,
252 [NF_INET_POST_ROUTING] = nft_do_chain_ipv6,
253 --- a/net/netfilter/nf_tables_inet.c
254 +++ b/net/netfilter/nf_tables_inet.c
255 @@ -38,38 +38,6 @@ static unsigned int nft_do_chain_inet(vo
256 return nft_do_chain(&pkt, priv);
257 }
258
259 -static unsigned int nft_inet_output(void *priv, struct sk_buff *skb,
260 - const struct nf_hook_state *state)
261 -{
262 - struct nft_pktinfo pkt;
263 -
264 - nft_set_pktinfo(&pkt, skb, state);
265 -
266 - switch (state->pf) {
267 - case NFPROTO_IPV4:
268 - if (unlikely(skb->len < sizeof(struct iphdr) ||
269 - ip_hdr(skb)->ihl < sizeof(struct iphdr) / 4)) {
270 - if (net_ratelimit())
271 - pr_info("ignoring short SOCK_RAW packet\n");
272 - return NF_ACCEPT;
273 - }
274 - nft_set_pktinfo_ipv4(&pkt, skb);
275 - break;
276 - case NFPROTO_IPV6:
277 - if (unlikely(skb->len < sizeof(struct ipv6hdr))) {
278 - if (net_ratelimit())
279 - pr_info("ignoring short SOCK_RAW packet\n");
280 - return NF_ACCEPT;
281 - }
282 - nft_set_pktinfo_ipv6(&pkt, skb);
283 - break;
284 - default:
285 - break;
286 - }
287 -
288 - return nft_do_chain(&pkt, priv);
289 -}
290 -
291 static struct nft_af_info nft_af_inet __read_mostly = {
292 .family = NFPROTO_INET,
293 .nhooks = NF_INET_NUMHOOKS,
294 @@ -116,7 +84,7 @@ static const struct nf_chain_type filter
295 (1 << NF_INET_POST_ROUTING),
296 .hooks = {
297 [NF_INET_LOCAL_IN] = nft_do_chain_inet,
298 - [NF_INET_LOCAL_OUT] = nft_inet_output,
299 + [NF_INET_LOCAL_OUT] = nft_do_chain_inet,
300 [NF_INET_FORWARD] = nft_do_chain_inet,
301 [NF_INET_PRE_ROUTING] = nft_do_chain_inet,
302 [NF_INET_POST_ROUTING] = nft_do_chain_inet,
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