// SPDX-License-Identifier: GPL-2.0-only
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/*
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* xt_u32 - kernel module to match u32 packet content
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*
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* Original author: Don Cohen <don@isis.cs3-inc.com>
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* (C) CC Computer Consultants GmbH, 2007
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*/
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#include <linux/module.h>
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#include <linux/moduleparam.h>
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#include <linux/spinlock.h>
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#include <linux/skbuff.h>
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#include <linux/types.h>
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#include <linux/netfilter/x_tables.h>
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#include <linux/netfilter/xt_u32.h>
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static bool u32_match_it(const struct xt_u32 *data,
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const struct sk_buff *skb)
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{
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const struct xt_u32_test *ct;
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unsigned int testind;
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unsigned int nnums;
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unsigned int nvals;
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unsigned int i;
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__be32 n;
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u_int32_t pos;
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u_int32_t val;
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u_int32_t at;
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/*
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* Small example: "0 >> 28 == 4 && 8 & 0xFF0000 >> 16 = 6, 17"
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* (=IPv4 and (TCP or UDP)). Outer loop runs over the "&&" operands.
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*/
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for (testind = 0; testind < data->ntests; ++testind) {
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ct = &data->tests[testind];
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at = 0;
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pos = ct->location[0].number;
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if (skb->len < 4 || pos > skb->len - 4)
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return false;
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if (skb_copy_bits(skb, pos, &n, sizeof(n)) < 0)
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BUG();
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val = ntohl(n);
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nnums = ct->nnums;
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/* Inner loop runs over "&", "<<", ">>" and "@" operands */
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for (i = 1; i < nnums; ++i) {
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u_int32_t number = ct->location[i].number;
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switch (ct->location[i].nextop) {
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case XT_U32_AND:
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val &= number;
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break;
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case XT_U32_LEFTSH:
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val <<= number;
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break;
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case XT_U32_RIGHTSH:
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val >>= number;
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break;
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case XT_U32_AT:
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if (at + val < at)
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return false;
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at += val;
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pos = number;
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if (at + 4 < at || skb->len < at + 4 ||
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pos > skb->len - at - 4)
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return false;
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if (skb_copy_bits(skb, at + pos, &n,
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sizeof(n)) < 0)
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BUG();
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val = ntohl(n);
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break;
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}
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}
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/* Run over the "," and ":" operands */
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nvals = ct->nvalues;
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for (i = 0; i < nvals; ++i)
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if (ct->value[i].min <= val && val <= ct->value[i].max)
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break;
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if (i >= ct->nvalues)
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return false;
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}
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return true;
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}
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static bool u32_mt(const struct sk_buff *skb, struct xt_action_param *par)
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{
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const struct xt_u32 *data = par->matchinfo;
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bool ret;
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ret = u32_match_it(data, skb);
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return ret ^ data->invert;
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}
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static struct xt_match xt_u32_mt_reg __read_mostly = {
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.name = "u32",
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.revision = 0,
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.family = NFPROTO_UNSPEC,
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.match = u32_mt,
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.matchsize = sizeof(struct xt_u32),
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.me = THIS_MODULE,
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};
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static int __init u32_mt_init(void)
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{
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return xt_register_match(&xt_u32_mt_reg);
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}
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static void __exit u32_mt_exit(void)
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{
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xt_unregister_match(&xt_u32_mt_reg);
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}
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module_init(u32_mt_init);
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module_exit(u32_mt_exit);
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MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
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MODULE_DESCRIPTION("Xtables: arbitrary byte matching");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS("ipt_u32");
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MODULE_ALIAS("ip6t_u32");
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