127 lines
3.0 KiB
C
127 lines
3.0 KiB
C
/* Kernel module to match ESP parameters. */
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/* (C) 1999-2000 Yon Uriarte <yon@astaro.de>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/in.h>
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#include <linux/ip.h>
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#include <linux/netfilter/xt_esp.h>
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#include <linux/netfilter/x_tables.h>
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#include <linux/netfilter_ipv4/ip_tables.h>
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#include <linux/netfilter_ipv6/ip6_tables.h>
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>");
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MODULE_DESCRIPTION("x_tables ESP SPI match module");
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MODULE_ALIAS("ipt_esp");
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MODULE_ALIAS("ip6t_esp");
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#if 0
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#define duprintf(format, args...) printk(format , ## args)
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#else
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#define duprintf(format, args...)
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#endif
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/* Returns 1 if the spi is matched by the range, 0 otherwise */
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static inline bool
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spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
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{
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bool r;
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duprintf("esp spi_match:%c 0x%x <= 0x%x <= 0x%x", invert ? '!' : ' ',
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min, spi, max);
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r = (spi >= min && spi <= max) ^ invert;
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duprintf(" result %s\n", r ? "PASS" : "FAILED");
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return r;
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}
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static bool
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match(const struct sk_buff *skb,
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const struct net_device *in,
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const struct net_device *out,
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const struct xt_match *match,
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const void *matchinfo,
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int offset,
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unsigned int protoff,
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bool *hotdrop)
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{
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struct ip_esp_hdr _esp, *eh;
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const struct xt_esp *espinfo = matchinfo;
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/* Must not be a fragment. */
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if (offset)
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return false;
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eh = skb_header_pointer(skb, protoff, sizeof(_esp), &_esp);
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if (eh == NULL) {
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/* We've been asked to examine this packet, and we
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* can't. Hence, no choice but to drop.
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*/
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duprintf("Dropping evil ESP tinygram.\n");
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*hotdrop = true;
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return false;
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}
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return spi_match(espinfo->spis[0], espinfo->spis[1], ntohl(eh->spi),
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!!(espinfo->invflags & XT_ESP_INV_SPI));
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}
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/* Called when user tries to insert an entry of this type. */
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static bool
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checkentry(const char *tablename,
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const void *ip_void,
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const struct xt_match *match,
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void *matchinfo,
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unsigned int hook_mask)
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{
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const struct xt_esp *espinfo = matchinfo;
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if (espinfo->invflags & ~XT_ESP_INV_MASK) {
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duprintf("xt_esp: unknown flags %X\n", espinfo->invflags);
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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 struct xt_match xt_esp_match[] __read_mostly = {
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{
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.name = "esp",
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.family = AF_INET,
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.checkentry = checkentry,
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.match = match,
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.matchsize = sizeof(struct xt_esp),
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.proto = IPPROTO_ESP,
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.me = THIS_MODULE,
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},
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{
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.name = "esp",
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.family = AF_INET6,
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.checkentry = checkentry,
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.match = match,
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.matchsize = sizeof(struct xt_esp),
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.proto = IPPROTO_ESP,
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.me = THIS_MODULE,
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},
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};
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static int __init xt_esp_init(void)
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{
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return xt_register_matches(xt_esp_match, ARRAY_SIZE(xt_esp_match));
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}
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static void __exit xt_esp_cleanup(void)
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{
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xt_unregister_matches(xt_esp_match, ARRAY_SIZE(xt_esp_match));
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}
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module_init(xt_esp_init);
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module_exit(xt_esp_cleanup);
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