1 | // SPDX-License-Identifier: GPL-2.0-only |
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 <linux/sctp.h> |
8 | |
9 | #include <linux/netfilter/x_tables.h> |
10 | #include <linux/netfilter/xt_sctp.h> |
11 | #include <linux/netfilter_ipv4/ip_tables.h> |
12 | #include <linux/netfilter_ipv6/ip6_tables.h> |
13 | |
14 | MODULE_LICENSE("GPL" ); |
15 | MODULE_AUTHOR("Kiran Kumar Immidi" ); |
16 | MODULE_DESCRIPTION("Xtables: SCTP protocol packet match" ); |
17 | MODULE_ALIAS("ipt_sctp" ); |
18 | MODULE_ALIAS("ip6t_sctp" ); |
19 | |
20 | #define SCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \ |
21 | || (!!((invflag) & (option)) ^ (cond))) |
22 | |
23 | static bool |
24 | match_flags(const struct xt_sctp_flag_info *flag_info, |
25 | const int flag_count, |
26 | u_int8_t chunktype, |
27 | u_int8_t chunkflags) |
28 | { |
29 | int i; |
30 | |
31 | for (i = 0; i < flag_count; i++) |
32 | if (flag_info[i].chunktype == chunktype) |
33 | return (chunkflags & flag_info[i].flag_mask) == flag_info[i].flag; |
34 | |
35 | return true; |
36 | } |
37 | |
38 | static inline bool |
39 | match_packet(const struct sk_buff *skb, |
40 | unsigned int offset, |
41 | const struct xt_sctp_info *info, |
42 | bool *hotdrop) |
43 | { |
44 | u_int32_t chunkmapcopy[256 / sizeof (u_int32_t)]; |
45 | const struct sctp_chunkhdr *sch; |
46 | struct sctp_chunkhdr _sch; |
47 | int chunk_match_type = info->chunk_match_type; |
48 | const struct xt_sctp_flag_info *flag_info = info->flag_info; |
49 | int flag_count = info->flag_count; |
50 | |
51 | #ifdef DEBUG |
52 | int i = 0; |
53 | #endif |
54 | |
55 | if (chunk_match_type == SCTP_CHUNK_MATCH_ALL) |
56 | SCTP_CHUNKMAP_COPY(chunkmapcopy, info->chunkmap); |
57 | |
58 | do { |
59 | sch = skb_header_pointer(skb, offset, len: sizeof(_sch), buffer: &_sch); |
60 | if (sch == NULL || sch->length == 0) { |
61 | pr_debug("Dropping invalid SCTP packet.\n" ); |
62 | *hotdrop = true; |
63 | return false; |
64 | } |
65 | #ifdef DEBUG |
66 | pr_debug("Chunk num: %d\toffset: %d\ttype: %d\tlength: %d" |
67 | "\tflags: %x\n" , |
68 | ++i, offset, sch->type, htons(sch->length), |
69 | sch->flags); |
70 | #endif |
71 | offset += SCTP_PAD4(ntohs(sch->length)); |
72 | |
73 | pr_debug("skb->len: %d\toffset: %d\n" , skb->len, offset); |
74 | |
75 | if (SCTP_CHUNKMAP_IS_SET(info->chunkmap, sch->type)) { |
76 | switch (chunk_match_type) { |
77 | case SCTP_CHUNK_MATCH_ANY: |
78 | if (match_flags(flag_info, flag_count, |
79 | chunktype: sch->type, chunkflags: sch->flags)) { |
80 | return true; |
81 | } |
82 | break; |
83 | |
84 | case SCTP_CHUNK_MATCH_ALL: |
85 | if (match_flags(flag_info, flag_count, |
86 | chunktype: sch->type, chunkflags: sch->flags)) |
87 | SCTP_CHUNKMAP_CLEAR(chunkmapcopy, sch->type); |
88 | break; |
89 | |
90 | case SCTP_CHUNK_MATCH_ONLY: |
91 | if (!match_flags(flag_info, flag_count, |
92 | chunktype: sch->type, chunkflags: sch->flags)) |
93 | return false; |
94 | break; |
95 | } |
96 | } else { |
97 | switch (chunk_match_type) { |
98 | case SCTP_CHUNK_MATCH_ONLY: |
99 | return false; |
100 | } |
101 | } |
102 | } while (offset < skb->len); |
103 | |
104 | switch (chunk_match_type) { |
105 | case SCTP_CHUNK_MATCH_ALL: |
106 | return SCTP_CHUNKMAP_IS_CLEAR(chunkmapcopy); |
107 | case SCTP_CHUNK_MATCH_ANY: |
108 | return false; |
109 | case SCTP_CHUNK_MATCH_ONLY: |
110 | return true; |
111 | } |
112 | |
113 | /* This will never be reached, but required to stop compiler whine */ |
114 | return false; |
115 | } |
116 | |
117 | static bool |
118 | sctp_mt(const struct sk_buff *skb, struct xt_action_param *par) |
119 | { |
120 | const struct xt_sctp_info *info = par->matchinfo; |
121 | const struct sctphdr *sh; |
122 | struct sctphdr _sh; |
123 | |
124 | if (par->fragoff != 0) { |
125 | pr_debug("Dropping non-first fragment.. FIXME\n" ); |
126 | return false; |
127 | } |
128 | |
129 | sh = skb_header_pointer(skb, offset: par->thoff, len: sizeof(_sh), buffer: &_sh); |
130 | if (sh == NULL) { |
131 | pr_debug("Dropping evil TCP offset=0 tinygram.\n" ); |
132 | par->hotdrop = true; |
133 | return false; |
134 | } |
135 | pr_debug("spt: %d\tdpt: %d\n" , ntohs(sh->source), ntohs(sh->dest)); |
136 | |
137 | return SCCHECK(ntohs(sh->source) >= info->spts[0] |
138 | && ntohs(sh->source) <= info->spts[1], |
139 | XT_SCTP_SRC_PORTS, info->flags, info->invflags) && |
140 | SCCHECK(ntohs(sh->dest) >= info->dpts[0] |
141 | && ntohs(sh->dest) <= info->dpts[1], |
142 | XT_SCTP_DEST_PORTS, info->flags, info->invflags) && |
143 | SCCHECK(match_packet(skb, par->thoff + sizeof(_sh), |
144 | info, &par->hotdrop), |
145 | XT_SCTP_CHUNK_TYPES, info->flags, info->invflags); |
146 | } |
147 | |
148 | static int sctp_mt_check(const struct xt_mtchk_param *par) |
149 | { |
150 | const struct xt_sctp_info *info = par->matchinfo; |
151 | |
152 | if (info->flag_count > ARRAY_SIZE(info->flag_info)) |
153 | return -EINVAL; |
154 | if (info->flags & ~XT_SCTP_VALID_FLAGS) |
155 | return -EINVAL; |
156 | if (info->invflags & ~XT_SCTP_VALID_FLAGS) |
157 | return -EINVAL; |
158 | if (info->invflags & ~info->flags) |
159 | return -EINVAL; |
160 | if (!(info->flags & XT_SCTP_CHUNK_TYPES)) |
161 | return 0; |
162 | if (info->chunk_match_type & (SCTP_CHUNK_MATCH_ALL | |
163 | SCTP_CHUNK_MATCH_ANY | SCTP_CHUNK_MATCH_ONLY)) |
164 | return 0; |
165 | return -EINVAL; |
166 | } |
167 | |
168 | static struct xt_match sctp_mt_reg[] __read_mostly = { |
169 | { |
170 | .name = "sctp" , |
171 | .family = NFPROTO_IPV4, |
172 | .checkentry = sctp_mt_check, |
173 | .match = sctp_mt, |
174 | .matchsize = sizeof(struct xt_sctp_info), |
175 | .proto = IPPROTO_SCTP, |
176 | .me = THIS_MODULE |
177 | }, |
178 | { |
179 | .name = "sctp" , |
180 | .family = NFPROTO_IPV6, |
181 | .checkentry = sctp_mt_check, |
182 | .match = sctp_mt, |
183 | .matchsize = sizeof(struct xt_sctp_info), |
184 | .proto = IPPROTO_SCTP, |
185 | .me = THIS_MODULE |
186 | }, |
187 | }; |
188 | |
189 | static int __init sctp_mt_init(void) |
190 | { |
191 | return xt_register_matches(match: sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg)); |
192 | } |
193 | |
194 | static void __exit sctp_mt_exit(void) |
195 | { |
196 | xt_unregister_matches(match: sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg)); |
197 | } |
198 | |
199 | module_init(sctp_mt_init); |
200 | module_exit(sctp_mt_exit); |
201 | |