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