1#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
2#include <linux/module.h>
3#include <linux/skbuff.h>
4#include <net/ip.h>
5#include <net/ipv6.h>
6#include <net/sctp/sctp.h>
7#include <linux/sctp.h>
8
9#include <linux/netfilter/x_tables.h>
10#include <linux/netfilter/xt_sctp.h>
11#include <linux/netfilter_ipv4/ip_tables.h>
12#include <linux/netfilter_ipv6/ip6_tables.h>
13
14MODULE_LICENSE("GPL");
15MODULE_AUTHOR("Kiran Kumar Immidi");
16MODULE_DESCRIPTION("Xtables: SCTP protocol packet match");
17MODULE_ALIAS("ipt_sctp");
18MODULE_ALIAS("ip6t_sctp");
19
20#define SCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
21 || (!!((invflag) & (option)) ^ (cond)))
22
23static bool
24match_flags(const struct xt_sctp_flag_info *flag_info,
25 const int flag_count,
26 u_int8_t chunktype,
27 u_int8_t chunkflags)
28{
29 int i;
30
31 for (i = 0; i < flag_count; i++)
32 if (flag_info[i].chunktype == chunktype)
33 return (chunkflags & flag_info[i].flag_mask) == flag_info[i].flag;
34
35 return true;
36}
37
38static inline bool
39match_packet(const struct sk_buff *skb,
40 unsigned int offset,
41 const struct xt_sctp_info *info,
42 bool *hotdrop)
43{
44 u_int32_t chunkmapcopy[256 / sizeof (u_int32_t)];
45 const struct sctp_chunkhdr *sch;
46 struct sctp_chunkhdr _sch;
47 int chunk_match_type = info->chunk_match_type;
48 const struct xt_sctp_flag_info *flag_info = info->flag_info;
49 int flag_count = info->flag_count;
50
51#ifdef DEBUG
52 int i = 0;
53#endif
54
55 if (chunk_match_type == SCTP_CHUNK_MATCH_ALL)
56 SCTP_CHUNKMAP_COPY(chunkmapcopy, info->chunkmap);
57
58 do {
59 sch = skb_header_pointer(skb, offset, sizeof(_sch), &_sch);
60 if (sch == NULL || sch->length == 0) {
61 pr_debug("Dropping invalid SCTP packet.\n");
62 *hotdrop = true;
63 return false;
64 }
65#ifdef DEBUG
66 pr_debug("Chunk num: %d\toffset: %d\ttype: %d\tlength: %d"
67 "\tflags: %x\n",
68 ++i, offset, sch->type, htons(sch->length),
69 sch->flags);
70#endif
71 offset += SCTP_PAD4(ntohs(sch->length));
72
73 pr_debug("skb->len: %d\toffset: %d\n", skb->len, offset);
74
75 if (SCTP_CHUNKMAP_IS_SET(info->chunkmap, sch->type)) {
76 switch (chunk_match_type) {
77 case SCTP_CHUNK_MATCH_ANY:
78 if (match_flags(flag_info, flag_count,
79 sch->type, sch->flags)) {
80 return true;
81 }
82 break;
83
84 case SCTP_CHUNK_MATCH_ALL:
85 if (match_flags(flag_info, flag_count,
86 sch->type, sch->flags))
87 SCTP_CHUNKMAP_CLEAR(chunkmapcopy, sch->type);
88 break;
89
90 case SCTP_CHUNK_MATCH_ONLY:
91 if (!match_flags(flag_info, flag_count,
92 sch->type, sch->flags))
93 return false;
94 break;
95 }
96 } else {
97 switch (chunk_match_type) {
98 case SCTP_CHUNK_MATCH_ONLY:
99 return false;
100 }
101 }
102 } while (offset < skb->len);
103
104 switch (chunk_match_type) {
105 case SCTP_CHUNK_MATCH_ALL:
106 return SCTP_CHUNKMAP_IS_CLEAR(chunkmapcopy);
107 case SCTP_CHUNK_MATCH_ANY:
108 return false;
109 case SCTP_CHUNK_MATCH_ONLY:
110 return true;
111 }
112
113
114 return false;
115}
116
117static bool
118sctp_mt(const struct sk_buff *skb, struct xt_action_param *par)
119{
120 const struct xt_sctp_info *info = par->matchinfo;
121 const struct sctphdr *sh;
122 struct sctphdr _sh;
123
124 if (par->fragoff != 0) {
125 pr_debug("Dropping non-first fragment.. FIXME\n");
126 return false;
127 }
128
129 sh = skb_header_pointer(skb, par->thoff, sizeof(_sh), &_sh);
130 if (sh == NULL) {
131 pr_debug("Dropping evil TCP offset=0 tinygram.\n");
132 par->hotdrop = true;
133 return false;
134 }
135 pr_debug("spt: %d\tdpt: %d\n", ntohs(sh->source), ntohs(sh->dest));
136
137 return SCCHECK(ntohs(sh->source) >= info->spts[0]
138 && ntohs(sh->source) <= info->spts[1],
139 XT_SCTP_SRC_PORTS, info->flags, info->invflags) &&
140 SCCHECK(ntohs(sh->dest) >= info->dpts[0]
141 && ntohs(sh->dest) <= info->dpts[1],
142 XT_SCTP_DEST_PORTS, info->flags, info->invflags) &&
143 SCCHECK(match_packet(skb, par->thoff + sizeof(_sh),
144 info, &par->hotdrop),
145 XT_SCTP_CHUNK_TYPES, info->flags, info->invflags);
146}
147
148static int sctp_mt_check(const struct xt_mtchk_param *par)
149{
150 const struct xt_sctp_info *info = par->matchinfo;
151
152 if (info->flags & ~XT_SCTP_VALID_FLAGS)
153 return -EINVAL;
154 if (info->invflags & ~XT_SCTP_VALID_FLAGS)
155 return -EINVAL;
156 if (info->invflags & ~info->flags)
157 return -EINVAL;
158 if (!(info->flags & XT_SCTP_CHUNK_TYPES))
159 return 0;
160 if (info->chunk_match_type & (SCTP_CHUNK_MATCH_ALL |
161 SCTP_CHUNK_MATCH_ANY | SCTP_CHUNK_MATCH_ONLY))
162 return 0;
163 return -EINVAL;
164}
165
166static struct xt_match sctp_mt_reg[] __read_mostly = {
167 {
168 .name = "sctp",
169 .family = NFPROTO_IPV4,
170 .checkentry = sctp_mt_check,
171 .match = sctp_mt,
172 .matchsize = sizeof(struct xt_sctp_info),
173 .proto = IPPROTO_SCTP,
174 .me = THIS_MODULE
175 },
176 {
177 .name = "sctp",
178 .family = NFPROTO_IPV6,
179 .checkentry = sctp_mt_check,
180 .match = sctp_mt,
181 .matchsize = sizeof(struct xt_sctp_info),
182 .proto = IPPROTO_SCTP,
183 .me = THIS_MODULE
184 },
185};
186
187static int __init sctp_mt_init(void)
188{
189 return xt_register_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg));
190}
191
192static void __exit sctp_mt_exit(void)
193{
194 xt_unregister_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg));
195}
196
197module_init(sctp_mt_init);
198module_exit(sctp_mt_exit);
199
