Jan Engelhardt | 1b50b8a | 2007-07-07 22:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * xt_u32 - kernel module to match u32 packet content |
| 3 | * |
| 4 | * Original author: Don Cohen <don@isis.cs3-inc.com> |
Jan Engelhardt | ba5dc27 | 2007-11-05 20:35:56 -0800 | [diff] [blame] | 5 | * (C) CC Computer Consultants GmbH, 2007 |
| 6 | * Contact: <jengelh@computergmbh.de> |
Jan Engelhardt | 1b50b8a | 2007-07-07 22:20:36 -0700 | [diff] [blame] | 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; |
Al Viro | a34c458 | 2007-07-26 17:33:19 +0100 | [diff] [blame] | 25 | __be32 n; |
Jan Engelhardt | 1b50b8a | 2007-07-07 22:20:36 -0700 | [diff] [blame] | 26 | u_int32_t pos; |
| 27 | u_int32_t val; |
| 28 | u_int32_t at; |
Jan Engelhardt | 1b50b8a | 2007-07-07 22:20:36 -0700 | [diff] [blame] | 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 | |
Eric Dumazet | 3501953 | 2007-08-14 13:13:28 -0700 | [diff] [blame] | 39 | if (skb->len < 4 || pos > skb->len - 4) |
Jan Engelhardt | 1b50b8a | 2007-07-07 22:20:36 -0700 | [diff] [blame] | 40 | return false; |
| 41 | |
Pavel Emelyanov | f449b3b | 2008-02-19 17:18:20 -0800 | [diff] [blame] | 42 | if (skb_copy_bits(skb, pos, &n, sizeof(n)) < 0) |
| 43 | BUG(); |
Al Viro | a34c458 | 2007-07-26 17:33:19 +0100 | [diff] [blame] | 44 | val = ntohl(n); |
Jan Engelhardt | 1b50b8a | 2007-07-07 22:20:36 -0700 | [diff] [blame] | 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 | |
Pavel Emelyanov | f449b3b | 2008-02-19 17:18:20 -0800 | [diff] [blame] | 69 | if (skb_copy_bits(skb, at + pos, &n, |
| 70 | sizeof(n)) < 0) |
| 71 | BUG(); |
Al Viro | a34c458 | 2007-07-26 17:33:19 +0100 | [diff] [blame] | 72 | val = ntohl(n); |
Jan Engelhardt | 1b50b8a | 2007-07-07 22:20:36 -0700 | [diff] [blame] | 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 | |
Jan Engelhardt | f7108a2 | 2008-10-08 11:35:18 +0200 | [diff] [blame] | 90 | static bool u32_mt(const struct sk_buff *skb, const struct xt_match_param *par) |
Jan Engelhardt | 1b50b8a | 2007-07-07 22:20:36 -0700 | [diff] [blame] | 91 | { |
Jan Engelhardt | f7108a2 | 2008-10-08 11:35:18 +0200 | [diff] [blame] | 92 | const struct xt_u32 *data = par->matchinfo; |
Jan Engelhardt | 1b50b8a | 2007-07-07 22:20:36 -0700 | [diff] [blame] | 93 | bool ret; |
| 94 | |
| 95 | ret = u32_match_it(data, skb); |
| 96 | return ret ^ data->invert; |
| 97 | } |
| 98 | |
Jan Engelhardt | 55b69e9 | 2008-10-08 11:35:01 +0200 | [diff] [blame] | 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, |
Jan Engelhardt | 1b50b8a | 2007-07-07 22:20:36 -0700 | [diff] [blame] | 106 | }; |
| 107 | |
Jan Engelhardt | d3c5ee6 | 2007-12-04 23:24:03 -0800 | [diff] [blame] | 108 | static int __init u32_mt_init(void) |
Jan Engelhardt | 1b50b8a | 2007-07-07 22:20:36 -0700 | [diff] [blame] | 109 | { |
Jan Engelhardt | 55b69e9 | 2008-10-08 11:35:01 +0200 | [diff] [blame] | 110 | return xt_register_match(&xt_u32_mt_reg); |
Jan Engelhardt | 1b50b8a | 2007-07-07 22:20:36 -0700 | [diff] [blame] | 111 | } |
| 112 | |
Jan Engelhardt | d3c5ee6 | 2007-12-04 23:24:03 -0800 | [diff] [blame] | 113 | static void __exit u32_mt_exit(void) |
Jan Engelhardt | 1b50b8a | 2007-07-07 22:20:36 -0700 | [diff] [blame] | 114 | { |
Jan Engelhardt | 55b69e9 | 2008-10-08 11:35:01 +0200 | [diff] [blame] | 115 | xt_unregister_match(&xt_u32_mt_reg); |
Jan Engelhardt | 1b50b8a | 2007-07-07 22:20:36 -0700 | [diff] [blame] | 116 | } |
| 117 | |
Jan Engelhardt | d3c5ee6 | 2007-12-04 23:24:03 -0800 | [diff] [blame] | 118 | module_init(u32_mt_init); |
| 119 | module_exit(u32_mt_exit); |
Jan Engelhardt | ba5dc27 | 2007-11-05 20:35:56 -0800 | [diff] [blame] | 120 | MODULE_AUTHOR("Jan Engelhardt <jengelh@computergmbh.de>"); |
Jan Engelhardt | 2ae15b6 | 2008-01-14 23:42:28 -0800 | [diff] [blame] | 121 | MODULE_DESCRIPTION("Xtables: arbitrary byte matching"); |
Jan Engelhardt | 1b50b8a | 2007-07-07 22:20:36 -0700 | [diff] [blame] | 122 | MODULE_LICENSE("GPL"); |
| 123 | MODULE_ALIAS("ipt_u32"); |
| 124 | MODULE_ALIAS("ip6t_u32"); |