[NETFILTER]: Convert x_tables matches/targets to centralized error checking
[linux-2.6.git] / net / netfilter / xt_sctp.c
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
12 MODULE_LICENSE("GPL");
13 MODULE_AUTHOR("Kiran Kumar Immidi");
14 MODULE_DESCRIPTION("Match for SCTP protocol packets");
15 MODULE_ALIAS("ipt_sctp");
16
17 #ifdef DEBUG_SCTP
18 #define duprintf(format, args...) printk(format , ## args)
19 #else
20 #define duprintf(format, args...)
21 #endif
22
23 #define SCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
24                                               || (!!((invflag) & (option)) ^ (cond)))
25
26 static int
27 match_flags(const struct xt_sctp_flag_info *flag_info,
28             const int flag_count,
29             u_int8_t chunktype,
30             u_int8_t chunkflags)
31 {
32         int i;
33
34         for (i = 0; i < flag_count; i++) {
35                 if (flag_info[i].chunktype == chunktype) {
36                         return (chunkflags & flag_info[i].flag_mask) == flag_info[i].flag;
37                 }
38         }
39
40         return 1;
41 }
42
43 static inline int
44 match_packet(const struct sk_buff *skb,
45              unsigned int offset,
46              const u_int32_t *chunkmap,
47              int chunk_match_type,
48              const struct xt_sctp_flag_info *flag_info,
49              const int flag_count,
50              int *hotdrop)
51 {
52         u_int32_t chunkmapcopy[256 / sizeof (u_int32_t)];
53         sctp_chunkhdr_t _sch, *sch;
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, chunkmap);
61         }
62
63         do {
64                 sch = skb_header_pointer(skb, offset, sizeof(_sch), &_sch);
65                 if (sch == NULL) {
66                         duprintf("Dropping invalid SCTP packet.\n");
67                         *hotdrop = 1;
68                         return 0;
69                 }
70
71                 duprintf("Chunk num: %d\toffset: %d\ttype: %d\tlength: %d\tflags: %x\n", 
72                                 ++i, offset, sch->type, htons(sch->length), sch->flags);
73
74                 offset += (htons(sch->length) + 3) & ~3;
75
76                 duprintf("skb->len: %d\toffset: %d\n", skb->len, offset);
77
78                 if (SCTP_CHUNKMAP_IS_SET(chunkmap, sch->type)) {
79                         switch (chunk_match_type) {
80                         case SCTP_CHUNK_MATCH_ANY:
81                                 if (match_flags(flag_info, flag_count, 
82                                         sch->type, sch->flags)) {
83                                         return 1;
84                                 }
85                                 break;
86
87                         case SCTP_CHUNK_MATCH_ALL:
88                                 if (match_flags(flag_info, flag_count, 
89                                         sch->type, sch->flags)) {
90                                         SCTP_CHUNKMAP_CLEAR(chunkmapcopy, sch->type);
91                                 }
92                                 break;
93
94                         case SCTP_CHUNK_MATCH_ONLY:
95                                 if (!match_flags(flag_info, flag_count, 
96                                         sch->type, sch->flags)) {
97                                         return 0;
98                                 }
99                                 break;
100                         }
101                 } else {
102                         switch (chunk_match_type) {
103                         case SCTP_CHUNK_MATCH_ONLY:
104                                 return 0;
105                         }
106                 }
107         } while (offset < skb->len);
108
109         switch (chunk_match_type) {
110         case SCTP_CHUNK_MATCH_ALL:
111                 return SCTP_CHUNKMAP_IS_CLEAR(chunkmap);
112         case SCTP_CHUNK_MATCH_ANY:
113                 return 0;
114         case SCTP_CHUNK_MATCH_ONLY:
115                 return 1;
116         }
117
118         /* This will never be reached, but required to stop compiler whine */
119         return 0;
120 }
121
122 static int
123 match(const struct sk_buff *skb,
124       const struct net_device *in,
125       const struct net_device *out,
126       const void *matchinfo,
127       int offset,
128       unsigned int protoff,
129       int *hotdrop)
130 {
131         const struct xt_sctp_info *info;
132         sctp_sctphdr_t _sh, *sh;
133
134         info = (const struct xt_sctp_info *)matchinfo;
135
136         if (offset) {
137                 duprintf("Dropping non-first fragment.. FIXME\n");
138                 return 0;
139         }
140         
141         sh = skb_header_pointer(skb, protoff, sizeof(_sh), &_sh);
142         if (sh == NULL) {
143                 duprintf("Dropping evil TCP offset=0 tinygram.\n");
144                 *hotdrop = 1;
145                 return 0;
146         }
147         duprintf("spt: %d\tdpt: %d\n", ntohs(sh->source), ntohs(sh->dest));
148
149         return  SCCHECK(((ntohs(sh->source) >= info->spts[0]) 
150                         && (ntohs(sh->source) <= info->spts[1])), 
151                         XT_SCTP_SRC_PORTS, info->flags, info->invflags)
152                 && SCCHECK(((ntohs(sh->dest) >= info->dpts[0]) 
153                         && (ntohs(sh->dest) <= info->dpts[1])), 
154                         XT_SCTP_DEST_PORTS, info->flags, info->invflags)
155                 && SCCHECK(match_packet(skb, protoff,
156                                         info->chunkmap, info->chunk_match_type,
157                                         info->flag_info, info->flag_count, 
158                                         hotdrop),
159                            XT_SCTP_CHUNK_TYPES, info->flags, info->invflags);
160 }
161
162 static int
163 checkentry(const char *tablename,
164            const void *inf,
165            void *matchinfo,
166            unsigned int matchsize,
167            unsigned int hook_mask)
168 {
169         const struct xt_sctp_info *info = matchinfo;
170
171         return !(info->flags & ~XT_SCTP_VALID_FLAGS)
172                 && !(info->invflags & ~XT_SCTP_VALID_FLAGS)
173                 && !(info->invflags & ~info->flags)
174                 && ((!(info->flags & XT_SCTP_CHUNK_TYPES)) || 
175                         (info->chunk_match_type &
176                                 (SCTP_CHUNK_MATCH_ALL 
177                                 | SCTP_CHUNK_MATCH_ANY
178                                 | SCTP_CHUNK_MATCH_ONLY)));
179 }
180
181 static struct xt_match sctp_match = {
182         .name           = "sctp",
183         .match          = match,
184         .matchsize      = sizeof(struct xt_sctp_info),
185         .proto          = IPPROTO_SCTP,
186         .checkentry     = checkentry,
187         .me             = THIS_MODULE
188 };
189
190 static struct xt_match sctp6_match = {
191         .name           = "sctp",
192         .match          = match,
193         .matchsize      = sizeof(struct xt_sctp_info),
194         .proto          = IPPROTO_SCTP,
195         .checkentry     = checkentry,
196         .me             = THIS_MODULE
197 };
198
199 static int __init init(void)
200 {
201         int ret;
202         ret = xt_register_match(AF_INET, &sctp_match);
203         if (ret)
204                 return ret;
205
206         ret = xt_register_match(AF_INET6, &sctp6_match);
207         if (ret)
208                 xt_unregister_match(AF_INET, &sctp_match);
209
210         return ret;
211 }
212
213 static void __exit fini(void)
214 {
215         xt_unregister_match(AF_INET6, &sctp6_match);
216         xt_unregister_match(AF_INET, &sctp_match);
217 }
218
219 module_init(init);
220 module_exit(fini);