1
2#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
3#include <linux/module.h>
4#include <linux/skbuff.h>
5#include <net/ip.h>
6#include <net/ipv6.h>
7#include <net/sctp/sctp.h>
8#include <linux/sctp.h>
9
10#include <linux/netfilter/x_tables.h>
11#include <linux/netfilter/xt_sctp.h>
12#include <linux/netfilter_ipv4/ip_tables.h>
13#include <linux/netfilter_ipv6/ip6_tables.h>
14
15MODULE_LICENSE("GPL");
16MODULE_AUTHOR("Kiran Kumar Immidi");
17MODULE_DESCRIPTION("Xtables: SCTP protocol packet match");
18MODULE_ALIAS("ipt_sctp");
19MODULE_ALIAS("ip6t_sctp");
20
21#define SCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
22 || (!!((invflag) & (option)) ^ (cond)))
23
24static bool
25match_flags(const struct xt_sctp_flag_info *flag_info,
26 const int flag_count,
27 u_int8_t chunktype,
28 u_int8_t chunkflags)
29{
30 int i;
31
32 for (i = 0; i < flag_count; i++)
33 if (flag_info[i].chunktype == chunktype)
34 return (chunkflags & flag_info[i].flag_mask) == flag_info[i].flag;
35
36 return true;
37}
38
39static inline bool
40match_packet(const struct sk_buff *skb,
41 unsigned int offset,
42 const struct xt_sctp_info *info,
43 bool *hotdrop)
44{
45 u_int32_t chunkmapcopy[256 / sizeof (u_int32_t)];
46 const struct sctp_chunkhdr *sch;
47 struct sctp_chunkhdr _sch;
48 int chunk_match_type = info->chunk_match_type;
49 const struct xt_sctp_flag_info *flag_info = info->flag_info;
50 int flag_count = info->flag_count;
51
52#ifdef DEBUG
53 int i = 0;
54#endif
55
56 if (chunk_match_type == SCTP_CHUNK_MATCH_ALL)
57 SCTP_CHUNKMAP_COPY(chunkmapcopy, info->chunkmap);
58
59 do {
60 sch = skb_header_pointer(skb, offset, sizeof(_sch), &_sch);
61 if (sch == NULL || sch->length == 0) {
62 pr_debug("Dropping invalid SCTP packet.\n");
63 *hotdrop = true;
64 return false;
65 }
66#ifdef DEBUG
67 pr_debug("Chunk num: %d\toffset: %d\ttype: %d\tlength: %d"
68 "\tflags: %x\n",
69 ++i, offset, sch->type, htons(sch->length),
70 sch->flags);
71#endif
72 offset += SCTP_PAD4(ntohs(sch->length));
73
74 pr_debug("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(chunkmapcopy);
108 case SCTP_CHUNK_MATCH_ANY:
109 return false;
110 case SCTP_CHUNK_MATCH_ONLY:
111 return true;
112 }
113
114
115 return false;
116}
117
118static bool
119sctp_mt(const struct sk_buff *skb, struct xt_action_param *par)
120{
121 const struct xt_sctp_info *info = par->matchinfo;
122 const struct sctphdr *sh;
123 struct sctphdr _sh;
124
125 if (par->fragoff != 0) {
126 pr_debug("Dropping non-first fragment.. FIXME\n");
127 return false;
128 }
129
130 sh = skb_header_pointer(skb, par->thoff, sizeof(_sh), &_sh);
131 if (sh == NULL) {
132 pr_debug("Dropping evil TCP offset=0 tinygram.\n");
133 par->hotdrop = true;
134 return false;
135 }
136 pr_debug("spt: %d\tdpt: %d\n", ntohs(sh->source), ntohs(sh->dest));
137
138 return SCCHECK(ntohs(sh->source) >= info->spts[0]
139 && ntohs(sh->source) <= info->spts[1],
140 XT_SCTP_SRC_PORTS, info->flags, info->invflags) &&
141 SCCHECK(ntohs(sh->dest) >= info->dpts[0]
142 && ntohs(sh->dest) <= info->dpts[1],
143 XT_SCTP_DEST_PORTS, info->flags, info->invflags) &&
144 SCCHECK(match_packet(skb, par->thoff + sizeof(_sh),
145 info, &par->hotdrop),
146 XT_SCTP_CHUNK_TYPES, info->flags, info->invflags);
147}
148
149static int sctp_mt_check(const struct xt_mtchk_param *par)
150{
151 const struct xt_sctp_info *info = par->matchinfo;
152
153 if (info->flags & ~XT_SCTP_VALID_FLAGS)
154 return -EINVAL;
155 if (info->invflags & ~XT_SCTP_VALID_FLAGS)
156 return -EINVAL;
157 if (info->invflags & ~info->flags)
158 return -EINVAL;
159 if (!(info->flags & XT_SCTP_CHUNK_TYPES))
160 return 0;
161 if (info->chunk_match_type & (SCTP_CHUNK_MATCH_ALL |
162 SCTP_CHUNK_MATCH_ANY | SCTP_CHUNK_MATCH_ONLY))
163 return 0;
164 return -EINVAL;
165}
166
167static struct xt_match sctp_mt_reg[] __read_mostly = {
168 {
169 .name = "sctp",
170 .family = NFPROTO_IPV4,
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 = NFPROTO_IPV6,
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
188static int __init sctp_mt_init(void)
189{
190 return xt_register_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg));
191}
192
193static void __exit sctp_mt_exit(void)
194{
195 xt_unregister_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg));
196}
197
198module_init(sctp_mt_init);
199module_exit(sctp_mt_exit);
200
