1 #include <linux/module.h>
2 #include <linux/skbuff.h>
3 #include <net/ip.h>
4 #include <net/ipv6.h>
5 #include <linux/sctp.h>
6
7 #include <linux/netfilter/x_tables.h>
8 #include <linux/netfilter/xt_sctp.h>
9 #include <linux/netfilter_ipv4/ip_tables.h>
10 #include <linux/netfilter_ipv6/ip6_tables.h>
11
12 MODULE_LICENSE("GPL");
13 MODULE_AUTHOR("Kiran Kumar Immidi");
14 MODULE_DESCRIPTION("Xtables: SCTP protocol packet match");
15 MODULE_ALIAS("ipt_sctp");
16 MODULE_ALIAS("ip6t_sctp");
17
18 #ifdef DEBUG_SCTP
19 #define duprintf(format, args...) printk(format , ## args)
20 #else
21 #define duprintf(format, args...)
22 #endif
23
24 #define SCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
25 || (!!((invflag) & (option)) ^ (cond)))
26
27 static bool
28 match_flags(const struct xt_sctp_flag_info *flag_info,
29 const int flag_count,
30 u_int8_t chunktype,
31 u_int8_t chunkflags)
32 {
33 int i;
34
35 for (i = 0; i < flag_count; i++)
36 if (flag_info[i].chunktype == chunktype)
37 return (chunkflags & flag_info[i].flag_mask) == flag_info[i].flag;
38
39 return true;
40 }
41
42 static inline bool
43 match_packet(const struct sk_buff *skb,
44 unsigned int offset,
45 const struct xt_sctp_info *info,
46 bool *hotdrop)
47 {
48 u_int32_t chunkmapcopy[256 / sizeof (u_int32_t)];
49 sctp_chunkhdr_t _sch, *sch;
50 int chunk_match_type = info->chunk_match_type;
51 const struct xt_sctp_flag_info *flag_info = info->flag_info;
52 int flag_count = info->flag_count;
53
54 #ifdef DEBUG_SCTP
55 int i = 0;
56 #endif
57
58 if (chunk_match_type == SCTP_CHUNK_MATCH_ALL)
59 SCTP_CHUNKMAP_COPY(chunkmapcopy, info->chunkmap);
60
61 do {
62 sch = skb_header_pointer(skb, offset, sizeof(_sch), &_sch);
63 if (sch == NULL || sch->length == 0) {
64 duprintf("Dropping invalid SCTP packet.\n");
65 *hotdrop = true;
66 return false;
67 }
68
69 duprintf("Chunk num: %d\toffset: %d\ttype: %d\tlength: %d\tflags: %x\n",
70 ++i, offset, sch->type, htons(sch->length), sch->flags);
71
72 offset += (ntohs(sch->length) + 3) & ~3;
73
74 duprintf("skb->len: %d\toffset: %d\n", skb->len, offset);
75
76 if (SCTP_CHUNKMAP_IS_SET(info->chunkmap, sch->type)) {
77 switch (chunk_match_type) {
78 case SCTP_CHUNK_MATCH_ANY:
79 if (match_flags(flag_info, flag_count,
80 sch->type, sch->flags)) {
81 return true;
82 }
83 break;
84
85 case SCTP_CHUNK_MATCH_ALL:
86 if (match_flags(flag_info, flag_count,
87 sch->type, sch->flags))
88 SCTP_CHUNKMAP_CLEAR(chunkmapcopy, sch->type);
89 break;
90
91 case SCTP_CHUNK_MATCH_ONLY:
92 if (!match_flags(flag_info, flag_count,
93 sch->type, sch->flags))
94 return false;
95 break;
96 }
97 } else {
98 switch (chunk_match_type) {
99 case SCTP_CHUNK_MATCH_ONLY:
100 return false;
101 }
102 }
103 } while (offset < skb->len);
104
105 switch (chunk_match_type) {
106 case SCTP_CHUNK_MATCH_ALL:
107 return SCTP_CHUNKMAP_IS_CLEAR(info->chunkmap);
108 case SCTP_CHUNK_MATCH_ANY:
109 return false;
110 case SCTP_CHUNK_MATCH_ONLY:
111 return true;
112 }
113
114 /* This will never be reached, but required to stop compiler whine */
115 return false;
116 }
117
118 static bool
119 sctp_mt(const struct sk_buff *skb, const struct net_device *in,
120 const struct net_device *out, const struct xt_match *match,
121 const void *matchinfo, int offset, unsigned int protoff, bool *hotdrop)
122 {
123 const struct xt_sctp_info *info = matchinfo;
124 sctp_sctphdr_t _sh, *sh;
125
126 if (offset) {
127 duprintf("Dropping non-first fragment.. FIXME\n");
128 return false;
129 }
130
131 sh = skb_header_pointer(skb, protoff, sizeof(_sh), &_sh);
132 if (sh == NULL) {
133 duprintf("Dropping evil TCP offset=0 tinygram.\n");
134 *hotdrop = true;
135 return false;
136 }
137 duprintf("spt: %d\tdpt: %d\n", ntohs(sh->source), ntohs(sh->dest));
138
139 return SCCHECK(ntohs(sh->source) >= info->spts[0]
140 && ntohs(sh->source) <= info->spts[1],
141 XT_SCTP_SRC_PORTS, info->flags, info->invflags)
142 && SCCHECK(ntohs(sh->dest) >= info->dpts[0]
143 && ntohs(sh->dest) <= info->dpts[1],
144 XT_SCTP_DEST_PORTS, info->flags, info->invflags)
145 && SCCHECK(match_packet(skb, protoff + sizeof (sctp_sctphdr_t),
146 info, hotdrop),
147 XT_SCTP_CHUNK_TYPES, info->flags, info->invflags);
148 }
149
150 static bool
151 sctp_mt_check(const char *tablename, const void *inf,
152 const struct xt_match *match, void *matchinfo,
153 unsigned int hook_mask)
154 {
155 const struct xt_sctp_info *info = matchinfo;
156
157 return !(info->flags & ~XT_SCTP_VALID_FLAGS)
158 && !(info->invflags & ~XT_SCTP_VALID_FLAGS)
159 && !(info->invflags & ~info->flags)
160 && ((!(info->flags & XT_SCTP_CHUNK_TYPES)) ||
161 (info->chunk_match_type &
162 (SCTP_CHUNK_MATCH_ALL
163 | SCTP_CHUNK_MATCH_ANY
164 | SCTP_CHUNK_MATCH_ONLY)));
165 }
166
167 static struct xt_match sctp_mt_reg[] __read_mostly = {
168 {
169 .name = "sctp",
170 .family = AF_INET,
171 .checkentry = sctp_mt_check,
172 .match = sctp_mt,
173 .matchsize = sizeof(struct xt_sctp_info),
174 .proto = IPPROTO_SCTP,
175 .me = THIS_MODULE
176 },
177 {
178 .name = "sctp",
179 .family = AF_INET6,
180 .checkentry = sctp_mt_check,
181 .match = sctp_mt,
182 .matchsize = sizeof(struct xt_sctp_info),
183 .proto = IPPROTO_SCTP,
184 .me = THIS_MODULE
185 },
186 };
187
188 static int __init sctp_mt_init(void)
189 {
190 return xt_register_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg));
191 }
192
193 static void __exit sctp_mt_exit(void)
194 {
195 xt_unregister_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg));
196 }
197
198 module_init(sctp_mt_init);
199 module_exit(sctp_mt_exit);
200
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