tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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 <linux/sctp.h>
7
8#include <linux/netfilter/x_tables.h>
9#include <linux/netfilter/xt_sctp.h>
10#include <linux/netfilter_ipv4/ip_tables.h>
11#include <linux/netfilter_ipv6/ip6_tables.h>
12
13MODULE_LICENSE("GPL");
14MODULE_AUTHOR("Kiran Kumar Immidi");
15MODULE_DESCRIPTION("Xtables: SCTP protocol packet match");
16MODULE_ALIAS("ipt_sctp");
17MODULE_ALIAS("ip6t_sctp");
18
19#define SCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
20 || (!!((invflag) & (option)) ^ (cond)))
21
22static bool
23match_flags(const struct xt_sctp_flag_info *flag_info,
24 const int flag_count,
25 u_int8_t chunktype,
26 u_int8_t chunkflags)
27{
28 int i;
29
30 for (i = 0; i < flag_count; i++)
31 if (flag_info[i].chunktype == chunktype)
32 return (chunkflags & flag_info[i].flag_mask) == flag_info[i].flag;
33
34 return true;
35}
36
37static inline bool
38match_packet(const struct sk_buff *skb,
39 unsigned int offset,
40 const struct xt_sctp_info *info,
41 bool *hotdrop)
42{
43 u_int32_t chunkmapcopy[256 / sizeof (u_int32_t)];
44 const sctp_chunkhdr_t *sch;
45 sctp_chunkhdr_t _sch;
46 int chunk_match_type = info->chunk_match_type;
47 const struct xt_sctp_flag_info *flag_info = info->flag_info;
48 int flag_count = info->flag_count;
49
50#ifdef DEBUG
51 int i = 0;
52#endif
53
54 if (chunk_match_type == SCTP_CHUNK_MATCH_ALL)
55 SCTP_CHUNKMAP_COPY(chunkmapcopy, info->chunkmap);
56
57 do {
58 sch = skb_header_pointer(skb, offset, sizeof(_sch), &_sch);
59 if (sch == NULL || sch->length == 0) {
60 pr_debug("Dropping invalid SCTP packet.\n");
61 *hotdrop = true;
62 return false;
63 }
64#ifdef DEBUG
65 pr_debug("Chunk num: %d\toffset: %d\ttype: %d\tlength: %d"
66 "\tflags: %x\n",
67 ++i, offset, sch->type, htons(sch->length),
68 sch->flags);
69#endif
70 offset += (ntohs(sch->length) + 3) & ~3;
71
72 pr_debug("skb->len: %d\toffset: %d\n", skb->len, offset);
73
74 if (SCTP_CHUNKMAP_IS_SET(info->chunkmap, sch->type)) {
75 switch (chunk_match_type) {
76 case SCTP_CHUNK_MATCH_ANY:
77 if (match_flags(flag_info, flag_count,
78 sch->type, sch->flags)) {
79 return true;
80 }
81 break;
82
83 case SCTP_CHUNK_MATCH_ALL:
84 if (match_flags(flag_info, flag_count,
85 sch->type, sch->flags))
86 SCTP_CHUNKMAP_CLEAR(chunkmapcopy, sch->type);
87 break;
88
89 case SCTP_CHUNK_MATCH_ONLY:
90 if (!match_flags(flag_info, flag_count,
91 sch->type, sch->flags))
92 return false;
93 break;
94 }
95 } else {
96 switch (chunk_match_type) {
97 case SCTP_CHUNK_MATCH_ONLY:
98 return false;
99 }
100 }
101 } while (offset < skb->len);
102
103 switch (chunk_match_type) {
104 case SCTP_CHUNK_MATCH_ALL:
105 return SCTP_CHUNKMAP_IS_CLEAR(chunkmapcopy);
106 case SCTP_CHUNK_MATCH_ANY:
107 return false;
108 case SCTP_CHUNK_MATCH_ONLY:
109 return true;
110 }
111
112 /* This will never be reached, but required to stop compiler whine */
113 return false;
114}
115
116static bool
117sctp_mt(const struct sk_buff *skb, struct xt_action_param *par)
118{
119 const struct xt_sctp_info *info = par->matchinfo;
120 const sctp_sctphdr_t *sh;
121 sctp_sctphdr_t _sh;
122
123 if (par->fragoff != 0) {
124 pr_debug("Dropping non-first fragment.. FIXME\n");
125 return false;
126 }
127
128 sh = skb_header_pointer(skb, par->thoff, sizeof(_sh), &_sh);
129 if (sh == NULL) {
130 pr_debug("Dropping evil TCP offset=0 tinygram.\n");
131 par->hotdrop = true;
132 return false;
133 }
134 pr_debug("spt: %d\tdpt: %d\n", ntohs(sh->source), ntohs(sh->dest));
135
136 return SCCHECK(ntohs(sh->source) >= info->spts[0]
137 && ntohs(sh->source) <= info->spts[1],
138 XT_SCTP_SRC_PORTS, info->flags, info->invflags)
139 && SCCHECK(ntohs(sh->dest) >= info->dpts[0]
140 && ntohs(sh->dest) <= info->dpts[1],
141 XT_SCTP_DEST_PORTS, info->flags, info->invflags)
142 && SCCHECK(match_packet(skb, par->thoff + sizeof(sctp_sctphdr_t),
143 info, &par->hotdrop),
144 XT_SCTP_CHUNK_TYPES, info->flags, info->invflags);
145}
146
147static int sctp_mt_check(const struct xt_mtchk_param *par)
148{
149 const struct xt_sctp_info *info = par->matchinfo;
150
151 if (info->flags & ~XT_SCTP_VALID_FLAGS)
152 return -EINVAL;
153 if (info->invflags & ~XT_SCTP_VALID_FLAGS)
154 return -EINVAL;
155 if (info->invflags & ~info->flags)
156 return -EINVAL;
157 if (!(info->flags & XT_SCTP_CHUNK_TYPES))
158 return 0;
159 if (info->chunk_match_type & (SCTP_CHUNK_MATCH_ALL |
160 SCTP_CHUNK_MATCH_ANY | SCTP_CHUNK_MATCH_ONLY))
161 return 0;
162 return -EINVAL;
163}
164
165static struct xt_match sctp_mt_reg[] __read_mostly = {
166 {
167 .name = "sctp",
168 .family = NFPROTO_IPV4,
169 .checkentry = sctp_mt_check,
170 .match = sctp_mt,
171 .matchsize = sizeof(struct xt_sctp_info),
172 .proto = IPPROTO_SCTP,
173 .me = THIS_MODULE
174 },
175 {
176 .name = "sctp",
177 .family = NFPROTO_IPV6,
178 .checkentry = sctp_mt_check,
179 .match = sctp_mt,
180 .matchsize = sizeof(struct xt_sctp_info),
181 .proto = IPPROTO_SCTP,
182 .me = THIS_MODULE
183 },
184};
185
186static int __init sctp_mt_init(void)
187{
188 return xt_register_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg));
189}
190
191static void __exit sctp_mt_exit(void)
192{
193 xt_unregister_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg));
194}
195
196module_init(sctp_mt_init);
197module_exit(sctp_mt_exit);