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1/*
2 * xt_u32 - kernel module to match u32 packet content
3 *
4 * Original author: Don Cohen <don@isis.cs3-inc.com>
5 * (C) CC Computer Consultants GmbH, 2007
6 */
7
8#include <linux/module.h>
9#include <linux/moduleparam.h>
10#include <linux/spinlock.h>
11#include <linux/skbuff.h>
12#include <linux/types.h>
13#include <linux/netfilter/x_tables.h>
14#include <linux/netfilter/xt_u32.h>
15
16static bool u32_match_it(const struct xt_u32 *data,
17 const struct sk_buff *skb)
18{
19 const struct xt_u32_test *ct;
20 unsigned int testind;
21 unsigned int nnums;
22 unsigned int nvals;
23 unsigned int i;
24 __be32 n;
25 u_int32_t pos;
26 u_int32_t val;
27 u_int32_t at;
28
29 /*
30 * Small example: "0 >> 28 == 4 && 8 & 0xFF0000 >> 16 = 6, 17"
31 * (=IPv4 and (TCP or UDP)). Outer loop runs over the "&&" operands.
32 */
33 for (testind = 0; testind < data->ntests; ++testind) {
34 ct = &data->tests[testind];
35 at = 0;
36 pos = ct->location[0].number;
37
38 if (skb->len < 4 || pos > skb->len - 4)
39 return false;
40
41 if (skb_copy_bits(skb, pos, &n, sizeof(n)) < 0)
42 BUG();
43 val = ntohl(n);
44 nnums = ct->nnums;
45
46 /* Inner loop runs over "&", "<<", ">>" and "@" operands */
47 for (i = 1; i < nnums; ++i) {
48 u_int32_t number = ct->location[i].number;
49 switch (ct->location[i].nextop) {
50 case XT_U32_AND:
51 val &= number;
52 break;
53 case XT_U32_LEFTSH:
54 val <<= number;
55 break;
56 case XT_U32_RIGHTSH:
57 val >>= number;
58 break;
59 case XT_U32_AT:
60 if (at + val < at)
61 return false;
62 at += val;
63 pos = number;
64 if (at + 4 < at || skb->len < at + 4 ||
65 pos > skb->len - at - 4)
66 return false;
67
68 if (skb_copy_bits(skb, at + pos, &n,
69 sizeof(n)) < 0)
70 BUG();
71 val = ntohl(n);
72 break;
73 }
74 }
75
76 /* Run over the "," and ":" operands */
77 nvals = ct->nvalues;
78 for (i = 0; i < nvals; ++i)
79 if (ct->value[i].min <= val && val <= ct->value[i].max)
80 break;
81
82 if (i >= ct->nvalues)
83 return false;
84 }
85
86 return true;
87}
88
89static bool u32_mt(const struct sk_buff *skb, struct xt_action_param *par)
90{
91 const struct xt_u32 *data = par->matchinfo;
92 bool ret;
93
94 ret = u32_match_it(data, skb);
95 return ret ^ data->invert;
96}
97
98static struct xt_match xt_u32_mt_reg __read_mostly = {
99 .name = "u32",
100 .revision = 0,
101 .family = NFPROTO_UNSPEC,
102 .match = u32_mt,
103 .matchsize = sizeof(struct xt_u32),
104 .me = THIS_MODULE,
105};
106
107static int __init u32_mt_init(void)
108{
109 return xt_register_match(&xt_u32_mt_reg);
110}
111
112static void __exit u32_mt_exit(void)
113{
114 xt_unregister_match(&xt_u32_mt_reg);
115}
116
117module_init(u32_mt_init);
118module_exit(u32_mt_exit);
119MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
120MODULE_DESCRIPTION("Xtables: arbitrary byte matching");
121MODULE_LICENSE("GPL");
122MODULE_ALIAS("ipt_u32");
123MODULE_ALIAS("ip6t_u32");
1/*
2 * xt_u32 - kernel module to match u32 packet content
3 *
4 * Original author: Don Cohen <don@isis.cs3-inc.com>
5 * (C) CC Computer Consultants GmbH, 2007
6 */
7
8#include <linux/module.h>
9#include <linux/moduleparam.h>
10#include <linux/spinlock.h>
11#include <linux/skbuff.h>
12#include <linux/types.h>
13#include <linux/netfilter/x_tables.h>
14#include <linux/netfilter/xt_u32.h>
15
16static bool u32_match_it(const struct xt_u32 *data,
17 const struct sk_buff *skb)
18{
19 const struct xt_u32_test *ct;
20 unsigned int testind;
21 unsigned int nnums;
22 unsigned int nvals;
23 unsigned int i;
24 __be32 n;
25 u_int32_t pos;
26 u_int32_t val;
27 u_int32_t at;
28
29 /*
30 * Small example: "0 >> 28 == 4 && 8 & 0xFF0000 >> 16 = 6, 17"
31 * (=IPv4 and (TCP or UDP)). Outer loop runs over the "&&" operands.
32 */
33 for (testind = 0; testind < data->ntests; ++testind) {
34 ct = &data->tests[testind];
35 at = 0;
36 pos = ct->location[0].number;
37
38 if (skb->len < 4 || pos > skb->len - 4)
39 return false;
40
41 if (skb_copy_bits(skb, pos, &n, sizeof(n)) < 0)
42 BUG();
43 val = ntohl(n);
44 nnums = ct->nnums;
45
46 /* Inner loop runs over "&", "<<", ">>" and "@" operands */
47 for (i = 1; i < nnums; ++i) {
48 u_int32_t number = ct->location[i].number;
49 switch (ct->location[i].nextop) {
50 case XT_U32_AND:
51 val &= number;
52 break;
53 case XT_U32_LEFTSH:
54 val <<= number;
55 break;
56 case XT_U32_RIGHTSH:
57 val >>= number;
58 break;
59 case XT_U32_AT:
60 if (at + val < at)
61 return false;
62 at += val;
63 pos = number;
64 if (at + 4 < at || skb->len < at + 4 ||
65 pos > skb->len - at - 4)
66 return false;
67
68 if (skb_copy_bits(skb, at + pos, &n,
69 sizeof(n)) < 0)
70 BUG();
71 val = ntohl(n);
72 break;
73 }
74 }
75
76 /* Run over the "," and ":" operands */
77 nvals = ct->nvalues;
78 for (i = 0; i < nvals; ++i)
79 if (ct->value[i].min <= val && val <= ct->value[i].max)
80 break;
81
82 if (i >= ct->nvalues)
83 return false;
84 }
85
86 return true;
87}
88
89static bool u32_mt(const struct sk_buff *skb, struct xt_action_param *par)
90{
91 const struct xt_u32 *data = par->matchinfo;
92 bool ret;
93
94 ret = u32_match_it(data, skb);
95 return ret ^ data->invert;
96}
97
98static struct xt_match xt_u32_mt_reg __read_mostly = {
99 .name = "u32",
100 .revision = 0,
101 .family = NFPROTO_UNSPEC,
102 .match = u32_mt,
103 .matchsize = sizeof(struct xt_u32),
104 .me = THIS_MODULE,
105};
106
107static int __init u32_mt_init(void)
108{
109 return xt_register_match(&xt_u32_mt_reg);
110}
111
112static void __exit u32_mt_exit(void)
113{
114 xt_unregister_match(&xt_u32_mt_reg);
115}
116
117module_init(u32_mt_init);
118module_exit(u32_mt_exit);
119MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
120MODULE_DESCRIPTION("Xtables: arbitrary byte matching");
121MODULE_LICENSE("GPL");
122MODULE_ALIAS("ipt_u32");
123MODULE_ALIAS("ip6t_u32");