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
14MODULE_LICENSE("GPL");
15MODULE_AUTHOR("Kiran Kumar Immidi");
16MODULE_DESCRIPTION("Xtables: SCTP protocol packet match");
17MODULE_ALIAS("ipt_sctp");
18MODULE_ALIAS("ip6t_sctp");
19
20#define SCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
21					      || (!!((invflag) & (option)) ^ (cond)))
22
23static bool
24match_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
38static inline bool
39match_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, sizeof(_sch), &_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					sch->type, sch->flags)) {
80					return true;
81				}
82				break;
83
84			case SCTP_CHUNK_MATCH_ALL:
85				if (match_flags(flag_info, flag_count,
86				    sch->type, 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				    sch->type, 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
117static bool
118sctp_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, par->thoff, sizeof(_sh), &_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
148static 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
168static 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
189static int __init sctp_mt_init(void)
190{
191	return xt_register_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg));
192}
193
194static void __exit sctp_mt_exit(void)
195{
196	xt_unregister_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg));
197}
198
199module_init(sctp_mt_init);
200module_exit(sctp_mt_exit);
201