tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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
12MODULE_LICENSE("GPL");
13MODULE_AUTHOR("Kiran Kumar Immidi");
14MODULE_DESCRIPTION("Xtables: SCTP protocol packet match");
15MODULE_ALIAS("ipt_sctp");
16MODULE_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
27static bool
28match_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
42static inline bool
43match_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 const sctp_chunkhdr_t *sch;
50 sctp_chunkhdr_t _sch;
51 int chunk_match_type = info->chunk_match_type;
52 const struct xt_sctp_flag_info *flag_info = info->flag_info;
53 int flag_count = info->flag_count;
54
55#ifdef DEBUG_SCTP
56 int i = 0;
57#endif
58
59 if (chunk_match_type == SCTP_CHUNK_MATCH_ALL)
60 SCTP_CHUNKMAP_COPY(chunkmapcopy, info->chunkmap);
61
62 do {
63 sch = skb_header_pointer(skb, offset, sizeof(_sch), &_sch);
64 if (sch == NULL || sch->length == 0) {
65 duprintf("Dropping invalid SCTP packet.\n");
66 *hotdrop = true;
67 return false;
68 }
69
70 duprintf("Chunk num: %d\toffset: %d\ttype: %d\tlength: %d\tflags: %x\n",
71 ++i, offset, sch->type, htons(sch->length), sch->flags);
72
73 offset += (ntohs(sch->length) + 3) & ~3;
74
75 duprintf("skb->len: %d\toffset: %d\n", skb->len, offset);
76
77 if (SCTP_CHUNKMAP_IS_SET(info->chunkmap, sch->type)) {
78 switch (chunk_match_type) {
79 case SCTP_CHUNK_MATCH_ANY:
80 if (match_flags(flag_info, flag_count,
81 sch->type, sch->flags)) {
82 return true;
83 }
84 break;
85
86 case SCTP_CHUNK_MATCH_ALL:
87 if (match_flags(flag_info, flag_count,
88 sch->type, sch->flags))
89 SCTP_CHUNKMAP_CLEAR(chunkmapcopy, sch->type);
90 break;
91
92 case SCTP_CHUNK_MATCH_ONLY:
93 if (!match_flags(flag_info, flag_count,
94 sch->type, sch->flags))
95 return false;
96 break;
97 }
98 } else {
99 switch (chunk_match_type) {
100 case SCTP_CHUNK_MATCH_ONLY:
101 return false;
102 }
103 }
104 } while (offset < skb->len);
105
106 switch (chunk_match_type) {
107 case SCTP_CHUNK_MATCH_ALL:
108 return SCTP_CHUNKMAP_IS_CLEAR(info->chunkmap);
109 case SCTP_CHUNK_MATCH_ANY:
110 return false;
111 case SCTP_CHUNK_MATCH_ONLY:
112 return true;
113 }
114
115 /* This will never be reached, but required to stop compiler whine */
116 return false;
117}
118
119static bool
120sctp_mt(const struct sk_buff *skb, const struct net_device *in,
121 const struct net_device *out, const struct xt_match *match,
122 const void *matchinfo, int offset, unsigned int protoff, bool *hotdrop)
123{
124 const struct xt_sctp_info *info = matchinfo;
125 const sctp_sctphdr_t *sh;
126 sctp_sctphdr_t _sh;
127
128 if (offset) {
129 duprintf("Dropping non-first fragment.. FIXME\n");
130 return false;
131 }
132
133 sh = skb_header_pointer(skb, protoff, sizeof(_sh), &_sh);
134 if (sh == NULL) {
135 duprintf("Dropping evil TCP offset=0 tinygram.\n");
136 *hotdrop = true;
137 return false;
138 }
139 duprintf("spt: %d\tdpt: %d\n", ntohs(sh->source), ntohs(sh->dest));
140
141 return SCCHECK(ntohs(sh->source) >= info->spts[0]
142 && ntohs(sh->source) <= info->spts[1],
143 XT_SCTP_SRC_PORTS, info->flags, info->invflags)
144 && SCCHECK(ntohs(sh->dest) >= info->dpts[0]
145 && ntohs(sh->dest) <= info->dpts[1],
146 XT_SCTP_DEST_PORTS, info->flags, info->invflags)
147 && SCCHECK(match_packet(skb, protoff + sizeof (sctp_sctphdr_t),
148 info, hotdrop),
149 XT_SCTP_CHUNK_TYPES, info->flags, info->invflags);
150}
151
152static bool
153sctp_mt_check(const char *tablename, const void *inf,
154 const struct xt_match *match, void *matchinfo,
155 unsigned int hook_mask)
156{
157 const struct xt_sctp_info *info = matchinfo;
158
159 return !(info->flags & ~XT_SCTP_VALID_FLAGS)
160 && !(info->invflags & ~XT_SCTP_VALID_FLAGS)
161 && !(info->invflags & ~info->flags)
162 && ((!(info->flags & XT_SCTP_CHUNK_TYPES)) ||
163 (info->chunk_match_type &
164 (SCTP_CHUNK_MATCH_ALL
165 | SCTP_CHUNK_MATCH_ANY
166 | SCTP_CHUNK_MATCH_ONLY)));
167}
168
169static struct xt_match sctp_mt_reg[] __read_mostly = {
170 {
171 .name = "sctp",
172 .family = AF_INET,
173 .checkentry = sctp_mt_check,
174 .match = sctp_mt,
175 .matchsize = sizeof(struct xt_sctp_info),
176 .proto = IPPROTO_SCTP,
177 .me = THIS_MODULE
178 },
179 {
180 .name = "sctp",
181 .family = AF_INET6,
182 .checkentry = sctp_mt_check,
183 .match = sctp_mt,
184 .matchsize = sizeof(struct xt_sctp_info),
185 .proto = IPPROTO_SCTP,
186 .me = THIS_MODULE
187 },
188};
189
190static int __init sctp_mt_init(void)
191{
192 return xt_register_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg));
193}
194
195static void __exit sctp_mt_exit(void)
196{
197 xt_unregister_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg));
198}
199
200module_init(sctp_mt_init);
201module_exit(sctp_mt_exit);