1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
|
#include <linux/module.h>
#include <linux/skbuff.h>
#include <net/ip.h>
#include <net/ipv6.h>
#include <linux/sctp.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_sctp.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv6/ip6_tables.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Kiran Kumar Immidi");
MODULE_DESCRIPTION("Match for SCTP protocol packets");
MODULE_ALIAS("ipt_sctp");
#ifdef DEBUG_SCTP
#define duprintf(format, args...) printk(format , ## args)
#else
#define duprintf(format, args...)
#endif
#define SCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
|| (!!((invflag) & (option)) ^ (cond)))
static bool
match_flags(const struct xt_sctp_flag_info *flag_info,
const int flag_count,
u_int8_t chunktype,
u_int8_t chunkflags)
{
int i;
for (i = 0; i < flag_count; i++)
if (flag_info[i].chunktype == chunktype)
return (chunkflags & flag_info[i].flag_mask) == flag_info[i].flag;
return true;
}
static inline bool
match_packet(const struct sk_buff *skb,
unsigned int offset,
const u_int32_t *chunkmap,
int chunk_match_type,
const struct xt_sctp_flag_info *flag_info,
const int flag_count,
bool *hotdrop)
{
u_int32_t chunkmapcopy[256 / sizeof (u_int32_t)];
sctp_chunkhdr_t _sch, *sch;
#ifdef DEBUG_SCTP
int i = 0;
#endif
if (chunk_match_type == SCTP_CHUNK_MATCH_ALL)
SCTP_CHUNKMAP_COPY(chunkmapcopy, chunkmap);
do {
sch = skb_header_pointer(skb, offset, sizeof(_sch), &_sch);
if (sch == NULL || sch->length == 0) {
duprintf("Dropping invalid SCTP packet.\n");
*hotdrop = true;
return false;
}
duprintf("Chunk num: %d\toffset: %d\ttype: %d\tlength: %d\tflags: %x\n",
++i, offset, sch->type, htons(sch->length), sch->flags);
offset += (ntohs(sch->length) + 3) & ~3;
duprintf("skb->len: %d\toffset: %d\n", skb->len, offset);
if (SCTP_CHUNKMAP_IS_SET(chunkmap, sch->type)) {
switch (chunk_match_type) {
case SCTP_CHUNK_MATCH_ANY:
if (match_flags(flag_info, flag_count,
sch->type, sch->flags)) {
return true;
}
break;
case SCTP_CHUNK_MATCH_ALL:
if (match_flags(flag_info, flag_count,
sch->type, sch->flags))
SCTP_CHUNKMAP_CLEAR(chunkmapcopy, sch->type);
break;
case SCTP_CHUNK_MATCH_ONLY:
if (!match_flags(flag_info, flag_count,
sch->type, sch->flags))
return false;
break;
}
} else {
switch (chunk_match_type) {
case SCTP_CHUNK_MATCH_ONLY:
return false;
}
}
} while (offset < skb->len);
switch (chunk_match_type) {
case SCTP_CHUNK_MATCH_ALL:
return SCTP_CHUNKMAP_IS_CLEAR(chunkmap);
case SCTP_CHUNK_MATCH_ANY:
return false;
case SCTP_CHUNK_MATCH_ONLY:
return true;
}
/* This will never be reached, but required to stop compiler whine */
return false;
}
static bool
match(const struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
const struct xt_match *match,
const void *matchinfo,
int offset,
unsigned int protoff,
bool *hotdrop)
{
const struct xt_sctp_info *info = matchinfo;
sctp_sctphdr_t _sh, *sh;
if (offset) {
duprintf("Dropping non-first fragment.. FIXME\n");
return false;
}
sh = skb_header_pointer(skb, protoff, sizeof(_sh), &_sh);
if (sh == NULL) {
duprintf("Dropping evil TCP offset=0 tinygram.\n");
*hotdrop = true;
return false;
}
duprintf("spt: %d\tdpt: %d\n", ntohs(sh->source), ntohs(sh->dest));
return SCCHECK(ntohs(sh->source) >= info->spts[0]
&& ntohs(sh->source) <= info->spts[1],
XT_SCTP_SRC_PORTS, info->flags, info->invflags)
&& SCCHECK(ntohs(sh->dest) >= info->dpts[0]
&& ntohs(sh->dest) <= info->dpts[1],
XT_SCTP_DEST_PORTS, info->flags, info->invflags)
&& SCCHECK(match_packet(skb, protoff + sizeof (sctp_sctphdr_t),
info->chunkmap, info->chunk_match_type,
info->flag_info, info->flag_count,
hotdrop),
XT_SCTP_CHUNK_TYPES, info->flags, info->invflags);
}
static bool
checkentry(const char *tablename,
const void *inf,
const struct xt_match *match,
void *matchinfo,
unsigned int hook_mask)
{
const struct xt_sctp_info *info = matchinfo;
return !(info->flags & ~XT_SCTP_VALID_FLAGS)
&& !(info->invflags & ~XT_SCTP_VALID_FLAGS)
&& !(info->invflags & ~info->flags)
&& ((!(info->flags & XT_SCTP_CHUNK_TYPES)) ||
(info->chunk_match_type &
(SCTP_CHUNK_MATCH_ALL
| SCTP_CHUNK_MATCH_ANY
| SCTP_CHUNK_MATCH_ONLY)));
}
static struct xt_match xt_sctp_match[] __read_mostly = {
{
.name = "sctp",
.family = AF_INET,
.checkentry = checkentry,
.match = match,
.matchsize = sizeof(struct xt_sctp_info),
.proto = IPPROTO_SCTP,
.me = THIS_MODULE
},
{
.name = "sctp",
.family = AF_INET6,
.checkentry = checkentry,
.match = match,
.matchsize = sizeof(struct xt_sctp_info),
.proto = IPPROTO_SCTP,
.me = THIS_MODULE
},
};
static int __init xt_sctp_init(void)
{
return xt_register_matches(xt_sctp_match, ARRAY_SIZE(xt_sctp_match));
}
static void __exit xt_sctp_fini(void)
{
xt_unregister_matches(xt_sctp_match, ARRAY_SIZE(xt_sctp_match));
}
module_init(xt_sctp_init);
module_exit(xt_sctp_fini);
|
