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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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 | // SPDX-License-Identifier: GPL-2.0-only /* * xt_u32 - kernel module to match u32 packet content * * Original author: Don Cohen <don@isis.cs3-inc.com> * (C) CC Computer Consultants GmbH, 2007 */ #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, struct xt_action_param *par) { const struct xt_u32 *data = par->matchinfo; bool ret; ret = u32_match_it(data, skb); return ret ^ data->invert; } static int u32_mt_checkentry(const struct xt_mtchk_param *par) { const struct xt_u32 *data = par->matchinfo; const struct xt_u32_test *ct; unsigned int i; if (data->ntests > ARRAY_SIZE(data->tests)) return -EINVAL; for (i = 0; i < data->ntests; ++i) { ct = &data->tests[i]; if (ct->nnums > ARRAY_SIZE(ct->location) || ct->nvalues > ARRAY_SIZE(ct->value)) return -EINVAL; } return 0; } static struct xt_match xt_u32_mt_reg __read_mostly = { .name = "u32", .revision = 0, .family = NFPROTO_UNSPEC, .match = u32_mt, .checkentry = u32_mt_checkentry, .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@medozas.de>"); MODULE_DESCRIPTION("Xtables: arbitrary byte matching"); MODULE_LICENSE("GPL"); MODULE_ALIAS("ipt_u32"); MODULE_ALIAS("ip6t_u32"); |