Commit | Line | Data |
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09c434b8 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
1b50b8a3 JE |
2 | /* |
3 | * xt_u32 - kernel module to match u32 packet content | |
4 | * | |
5 | * Original author: Don Cohen <don@isis.cs3-inc.com> | |
ba5dc275 | 6 | * (C) CC Computer Consultants GmbH, 2007 |
1b50b8a3 JE |
7 | */ |
8 | ||
9 | #include <linux/module.h> | |
10 | #include <linux/moduleparam.h> | |
11 | #include <linux/spinlock.h> | |
12 | #include <linux/skbuff.h> | |
13 | #include <linux/types.h> | |
14 | #include <linux/netfilter/x_tables.h> | |
15 | #include <linux/netfilter/xt_u32.h> | |
16 | ||
17 | static bool u32_match_it(const struct xt_u32 *data, | |
18 | const struct sk_buff *skb) | |
19 | { | |
20 | const struct xt_u32_test *ct; | |
21 | unsigned int testind; | |
22 | unsigned int nnums; | |
23 | unsigned int nvals; | |
24 | unsigned int i; | |
a34c4589 | 25 | __be32 n; |
1b50b8a3 JE |
26 | u_int32_t pos; |
27 | u_int32_t val; | |
28 | u_int32_t at; | |
1b50b8a3 JE |
29 | |
30 | /* | |
31 | * Small example: "0 >> 28 == 4 && 8 & 0xFF0000 >> 16 = 6, 17" | |
32 | * (=IPv4 and (TCP or UDP)). Outer loop runs over the "&&" operands. | |
33 | */ | |
34 | for (testind = 0; testind < data->ntests; ++testind) { | |
35 | ct = &data->tests[testind]; | |
36 | at = 0; | |
37 | pos = ct->location[0].number; | |
38 | ||
35019539 | 39 | if (skb->len < 4 || pos > skb->len - 4) |
1b50b8a3 JE |
40 | return false; |
41 | ||
f449b3b5 PE |
42 | if (skb_copy_bits(skb, pos, &n, sizeof(n)) < 0) |
43 | BUG(); | |
a34c4589 | 44 | val = ntohl(n); |
1b50b8a3 JE |
45 | nnums = ct->nnums; |
46 | ||
47 | /* Inner loop runs over "&", "<<", ">>" and "@" operands */ | |
48 | for (i = 1; i < nnums; ++i) { | |
49 | u_int32_t number = ct->location[i].number; | |
50 | switch (ct->location[i].nextop) { | |
51 | case XT_U32_AND: | |
52 | val &= number; | |
53 | break; | |
54 | case XT_U32_LEFTSH: | |
55 | val <<= number; | |
56 | break; | |
57 | case XT_U32_RIGHTSH: | |
58 | val >>= number; | |
59 | break; | |
60 | case XT_U32_AT: | |
61 | if (at + val < at) | |
62 | return false; | |
63 | at += val; | |
64 | pos = number; | |
65 | if (at + 4 < at || skb->len < at + 4 || | |
66 | pos > skb->len - at - 4) | |
67 | return false; | |
68 | ||
f449b3b5 PE |
69 | if (skb_copy_bits(skb, at + pos, &n, |
70 | sizeof(n)) < 0) | |
71 | BUG(); | |
a34c4589 | 72 | val = ntohl(n); |
1b50b8a3 JE |
73 | break; |
74 | } | |
75 | } | |
76 | ||
77 | /* Run over the "," and ":" operands */ | |
78 | nvals = ct->nvalues; | |
79 | for (i = 0; i < nvals; ++i) | |
80 | if (ct->value[i].min <= val && val <= ct->value[i].max) | |
81 | break; | |
82 | ||
83 | if (i >= ct->nvalues) | |
84 | return false; | |
85 | } | |
86 | ||
87 | return true; | |
88 | } | |
89 | ||
62fc8051 | 90 | static bool u32_mt(const struct sk_buff *skb, struct xt_action_param *par) |
1b50b8a3 | 91 | { |
f7108a20 | 92 | const struct xt_u32 *data = par->matchinfo; |
1b50b8a3 JE |
93 | bool ret; |
94 | ||
95 | ret = u32_match_it(data, skb); | |
96 | return ret ^ data->invert; | |
97 | } | |
98 | ||
55b69e91 JE |
99 | static struct xt_match xt_u32_mt_reg __read_mostly = { |
100 | .name = "u32", | |
101 | .revision = 0, | |
102 | .family = NFPROTO_UNSPEC, | |
103 | .match = u32_mt, | |
104 | .matchsize = sizeof(struct xt_u32), | |
105 | .me = THIS_MODULE, | |
1b50b8a3 JE |
106 | }; |
107 | ||
d3c5ee6d | 108 | static int __init u32_mt_init(void) |
1b50b8a3 | 109 | { |
55b69e91 | 110 | return xt_register_match(&xt_u32_mt_reg); |
1b50b8a3 JE |
111 | } |
112 | ||
d3c5ee6d | 113 | static void __exit u32_mt_exit(void) |
1b50b8a3 | 114 | { |
55b69e91 | 115 | xt_unregister_match(&xt_u32_mt_reg); |
1b50b8a3 JE |
116 | } |
117 | ||
d3c5ee6d JE |
118 | module_init(u32_mt_init); |
119 | module_exit(u32_mt_exit); | |
408ffaa4 | 120 | MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>"); |
2ae15b64 | 121 | MODULE_DESCRIPTION("Xtables: arbitrary byte matching"); |
1b50b8a3 JE |
122 | MODULE_LICENSE("GPL"); |
123 | MODULE_ALIAS("ipt_u32"); | |
124 | MODULE_ALIAS("ip6t_u32"); |