From 1b50b8a371e90a5e110f466e4ac02cf6b5f681de Mon Sep 17 00:00:00 2001 From: Jan Engelhardt Date: Sat, 7 Jul 2007 22:20:36 -0700 Subject: [PATCH] [NETFILTER]: Add u32 match Along comes... xt_u32, a revamped ipt_u32 from POM-NG, Plus: * 2007-06-02: added ipv6 support * 2007-06-05: uses kmalloc for the big buffer * 2007-06-05: added inversion * 2007-06-20: use skb_copy_bits() and get rid of the big buffer and lock (suggested by Pablo Neira Ayuso) Signed-off-by: Jan Engelhardt Signed-off-by: Patrick McHardy Signed-off-by: David S. Miller --- include/linux/netfilter/xt_u32.h | 40 +++++++++ net/netfilter/Kconfig | 13 +++ net/netfilter/Makefile | 1 + net/netfilter/xt_u32.c | 135 +++++++++++++++++++++++++++++++ 4 files changed, 189 insertions(+) create mode 100644 include/linux/netfilter/xt_u32.h create mode 100644 net/netfilter/xt_u32.c diff --git a/include/linux/netfilter/xt_u32.h b/include/linux/netfilter/xt_u32.h new file mode 100644 index 00000000000..9947f56cdbd --- /dev/null +++ b/include/linux/netfilter/xt_u32.h @@ -0,0 +1,40 @@ +#ifndef _XT_U32_H +#define _XT_U32_H 1 + +enum xt_u32_ops { + XT_U32_AND, + XT_U32_LEFTSH, + XT_U32_RIGHTSH, + XT_U32_AT, +}; + +struct xt_u32_location_element { + u_int32_t number; + u_int8_t nextop; +}; + +struct xt_u32_value_element { + u_int32_t min; + u_int32_t max; +}; + +/* + * Any way to allow for an arbitrary number of elements? + * For now, I settle with a limit of 10 each. + */ +#define XT_U32_MAXSIZE 10 + +struct xt_u32_test { + struct xt_u32_location_element location[XT_U32_MAXSIZE+1]; + struct xt_u32_value_element value[XT_U32_MAXSIZE+1]; + u_int8_t nnums; + u_int8_t nvalues; +}; + +struct xt_u32 { + struct xt_u32_test tests[XT_U32_MAXSIZE+1]; + u_int8_t ntests; + u_int8_t invert; +}; + +#endif /* _XT_U32_H */ diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig index a567dae8e5f..aa567faa2a8 100644 --- a/net/netfilter/Kconfig +++ b/net/netfilter/Kconfig @@ -635,6 +635,19 @@ config NETFILTER_XT_MATCH_TCPMSS To compile it as a module, choose M here. If unsure, say N. +config NETFILTER_XT_MATCH_U32 + tristate '"u32" match support' + depends on NETFILTER_XTABLES + ---help--- + u32 allows you to extract quantities of up to 4 bytes from a packet, + AND them with specified masks, shift them by specified amounts and + test whether the results are in any of a set of specified ranges. + The specification of what to extract is general enough to skip over + headers with lengths stored in the packet, as in IP or TCP header + lengths. + + Details and examples are in the kernel module source. + config NETFILTER_XT_MATCH_HASHLIMIT tristate '"hashlimit" match support' depends on NETFILTER_XTABLES && (IP6_NF_IPTABLES || IP6_NF_IPTABLES=n) diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile index b2b5c7566b2..3cf5b9cd6fe 100644 --- a/net/netfilter/Makefile +++ b/net/netfilter/Makefile @@ -72,4 +72,5 @@ obj-$(CONFIG_NETFILTER_XT_MATCH_STATISTIC) += xt_statistic.o obj-$(CONFIG_NETFILTER_XT_MATCH_STRING) += xt_string.o obj-$(CONFIG_NETFILTER_XT_MATCH_TCPMSS) += xt_tcpmss.o obj-$(CONFIG_NETFILTER_XT_MATCH_PHYSDEV) += xt_physdev.o +obj-$(CONFIG_NETFILTER_XT_MATCH_U32) += xt_u32.o obj-$(CONFIG_NETFILTER_XT_MATCH_HASHLIMIT) += xt_hashlimit.o diff --git a/net/netfilter/xt_u32.c b/net/netfilter/xt_u32.c new file mode 100644 index 00000000000..07068751a35 --- /dev/null +++ b/net/netfilter/xt_u32.c @@ -0,0 +1,135 @@ +/* + * xt_u32 - kernel module to match u32 packet content + * + * Original author: Don Cohen + * © Jan Engelhardt , 2007 + */ + +#include +#include +#include +#include +#include +#include +#include + +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; + u_int32_t pos; + u_int32_t val; + u_int32_t at; + int ret; + + /* + * 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; + + ret = skb_copy_bits(skb, pos, &val, sizeof(val)); + BUG_ON(ret < 0); + val = ntohl(val); + 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; + + ret = skb_copy_bits(skb, at + pos, &val, + sizeof(val)); + BUG_ON(ret < 0); + val = ntohl(val); + 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_match(const struct sk_buff *skb, + const struct net_device *in, + const struct net_device *out, + const struct xt_match *match, const void *matchinfo, + int offset, unsigned int protoff, bool *hotdrop) +{ + const struct xt_u32 *data = matchinfo; + bool ret; + + ret = u32_match_it(data, skb); + return ret ^ data->invert; +} + +static struct xt_match u32_reg[] = { + { + .name = "u32", + .family = AF_INET, + .match = u32_match, + .matchsize = sizeof(struct xt_u32), + .me = THIS_MODULE, + }, + { + .name = "u32", + .family = AF_INET6, + .match = u32_match, + .matchsize = sizeof(struct xt_u32), + .me = THIS_MODULE, + }, +}; + +static int __init xt_u32_init(void) +{ + return xt_register_matches(u32_reg, ARRAY_SIZE(u32_reg)); +} + +static void __exit xt_u32_exit(void) +{ + xt_unregister_matches(u32_reg, ARRAY_SIZE(u32_reg)); +} + +module_init(xt_u32_init); +module_exit(xt_u32_exit); +MODULE_AUTHOR("Jan Engelhardt "); +MODULE_DESCRIPTION("netfilter u32 match module"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("ipt_u32"); +MODULE_ALIAS("ip6t_u32"); -- 2.41.1