net/netfilter/xt_ipcomp.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /*  Kernel module to match IPComp parameters for IPv4 and IPv6
0003  *
0004  *  Copyright (C) 2013 WindRiver
0005  *
0006  *  Author:
0007  *  Fan Du <fan.du@windriver.com>
0008  *
0009  *  Based on:
0010  *  net/netfilter/xt_esp.c
0011  */
0012
0013 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
0014 #include <linux/in.h>
0015 #include <linux/module.h>
0016 #include <linux/skbuff.h>
0017 #include <linux/ip.h>
0018
0019 #include <linux/netfilter/xt_ipcomp.h>
0020 #include <linux/netfilter/x_tables.h>
0021
0022 MODULE_LICENSE("GPL");
0023 MODULE_AUTHOR("Fan Du <fan.du@windriver.com>");
0024 MODULE_DESCRIPTION("Xtables: IPv4/6 IPsec-IPComp SPI match");
0025 MODULE_ALIAS("ipt_ipcomp");
0026 MODULE_ALIAS("ip6t_ipcomp");
0027
0028 /* Returns 1 if the spi is matched by the range, 0 otherwise */
0029 static inline bool
0030 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
0031 {
0032     bool r;
0033     pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n",
0034          invert ? '!' : ' ', min, spi, max);
0035     r = (spi >= min && spi <= max) ^ invert;
0036     pr_debug(" result %s\n", r ? "PASS" : "FAILED");
0037     return r;
0038 }
0039
0040 static bool comp_mt(const struct sk_buff *skb, struct xt_action_param *par)
0041 {
0042     struct ip_comp_hdr _comphdr;
0043     const struct ip_comp_hdr *chdr;
0044     const struct xt_ipcomp *compinfo = par->matchinfo;
0045
0046     /* Must not be a fragment. */
0047     if (par->fragoff != 0)
0048         return false;
0049
0050     chdr = skb_header_pointer(skb, par->thoff, sizeof(_comphdr), &_comphdr);
0051     if (chdr == NULL) {
0052         /* We've been asked to examine this packet, and we
0053          * can't.  Hence, no choice but to drop.
0054          */
0055         pr_debug("Dropping evil IPComp tinygram.\n");
0056         par->hotdrop = true;
0057         return false;
0058     }
0059
0060     return spi_match(compinfo->spis[0], compinfo->spis[1],
0061              ntohs(chdr->cpi),
0062              !!(compinfo->invflags & XT_IPCOMP_INV_SPI));
0063 }
0064
0065 static int comp_mt_check(const struct xt_mtchk_param *par)
0066 {
0067     const struct xt_ipcomp *compinfo = par->matchinfo;
0068
0069     /* Must specify no unknown invflags */
0070     if (compinfo->invflags & ~XT_IPCOMP_INV_MASK) {
0071         pr_info_ratelimited("unknown flags %X\n", compinfo->invflags);
0072         return -EINVAL;
0073     }
0074     return 0;
0075 }
0076
0077 static struct xt_match comp_mt_reg[] __read_mostly = {
0078     {
0079         .name       = "ipcomp",
0080         .family     = NFPROTO_IPV4,
0081         .match      = comp_mt,
0082         .matchsize  = sizeof(struct xt_ipcomp),
0083         .proto      = IPPROTO_COMP,
0084         .checkentry = comp_mt_check,
0085         .me     = THIS_MODULE,
0086     },
0087     {
0088         .name       = "ipcomp",
0089         .family     = NFPROTO_IPV6,
0090         .match      = comp_mt,
0091         .matchsize  = sizeof(struct xt_ipcomp),
0092         .proto      = IPPROTO_COMP,
0093         .checkentry = comp_mt_check,
0094         .me     = THIS_MODULE,
0095     },
0096 };
0097
0098 static int __init comp_mt_init(void)
0099 {
0100     return xt_register_matches(comp_mt_reg, ARRAY_SIZE(comp_mt_reg));
0101 }
0102
0103 static void __exit comp_mt_exit(void)
0104 {
0105     xt_unregister_matches(comp_mt_reg, ARRAY_SIZE(comp_mt_reg));
0106 }
0107
0108 module_init(comp_mt_init);
0109 module_exit(comp_mt_exit);