mirror of
https://github.com/team-infusion-developers/android_kernel_samsung_msm8976.git
synced 2024-10-22 03:20:19 +00:00
6d381634d2
As reported by Mark Dowd <Mark_Dowd@McAfee.com>, ip6_tables is susceptible to a fragmentation attack causing false negatives on extension header matches. When extension headers occur in the non-first fragment after the fragment header (possibly with an incorrect nexthdr value in the fragment header) a rule looking for this extension header will never match. Drop fragments that are at offset 0 and don't contain the final protocol header regardless of the ruleset, since this should not happen normally. Since all extension headers are before the protocol header this makes sure an extension header is either not present or in the first fragment, where we can properly parse it. With help from Yasuyuki KOZAKAI <yasuyuki.kozakai@toshiba.co.jp>. Signed-off-by: Patrick McHardy <kaber@trash.net> Signed-off-by: David S. Miller <davem@davemloft.net>
157 lines
4.2 KiB
C
157 lines
4.2 KiB
C
/* Kernel module to match FRAG parameters. */
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/* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu>
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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/ipv6.h>
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#include <linux/types.h>
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#include <net/checksum.h>
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#include <net/ipv6.h>
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#include <linux/netfilter_ipv6/ip6_tables.h>
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#include <linux/netfilter_ipv6/ip6t_frag.h>
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("IPv6 FRAG match");
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MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
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#if 0
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#define DEBUGP printk
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#else
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#define DEBUGP(format, args...)
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#endif
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/* Returns 1 if the id is matched by the range, 0 otherwise */
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static inline int
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id_match(u_int32_t min, u_int32_t max, u_int32_t id, int invert)
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{
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int r = 0;
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DEBUGP("frag id_match:%c 0x%x <= 0x%x <= 0x%x", invert ? '!' : ' ',
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min, id, max);
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r = (id >= min && id <= max) ^ invert;
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DEBUGP(" result %s\n", r ? "PASS" : "FAILED");
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return r;
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}
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static int
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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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int *hotdrop)
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{
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struct frag_hdr _frag, *fh;
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const struct ip6t_frag *fraginfo = matchinfo;
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unsigned int ptr;
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int err;
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err = ipv6_find_hdr(skb, &ptr, NEXTHDR_FRAGMENT, NULL);
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if (err < 0) {
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if (err != -ENOENT)
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*hotdrop = 1;
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return 0;
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}
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fh = skb_header_pointer(skb, ptr, sizeof(_frag), &_frag);
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if (fh == NULL) {
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*hotdrop = 1;
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return 0;
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}
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DEBUGP("INFO %04X ", fh->frag_off);
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DEBUGP("OFFSET %04X ", ntohs(fh->frag_off) & ~0x7);
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DEBUGP("RES %02X %04X", fh->reserved, ntohs(fh->frag_off) & 0x6);
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DEBUGP("MF %04X ", fh->frag_off & htons(IP6_MF));
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DEBUGP("ID %u %08X\n", ntohl(fh->identification),
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ntohl(fh->identification));
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DEBUGP("IPv6 FRAG id %02X ",
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(id_match(fraginfo->ids[0], fraginfo->ids[1],
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ntohl(fh->identification),
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!!(fraginfo->invflags & IP6T_FRAG_INV_IDS))));
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DEBUGP("res %02X %02X%04X %02X ",
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(fraginfo->flags & IP6T_FRAG_RES), fh->reserved,
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ntohs(fh->frag_off) & 0x6,
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!((fraginfo->flags & IP6T_FRAG_RES)
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&& (fh->reserved || (ntohs(fh->frag_off) & 0x06))));
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DEBUGP("first %02X %02X %02X ",
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(fraginfo->flags & IP6T_FRAG_FST),
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ntohs(fh->frag_off) & ~0x7,
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!((fraginfo->flags & IP6T_FRAG_FST)
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&& (ntohs(fh->frag_off) & ~0x7)));
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DEBUGP("mf %02X %02X %02X ",
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(fraginfo->flags & IP6T_FRAG_MF),
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ntohs(fh->frag_off) & IP6_MF,
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!((fraginfo->flags & IP6T_FRAG_MF)
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&& !((ntohs(fh->frag_off) & IP6_MF))));
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DEBUGP("last %02X %02X %02X\n",
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(fraginfo->flags & IP6T_FRAG_NMF),
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ntohs(fh->frag_off) & IP6_MF,
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!((fraginfo->flags & IP6T_FRAG_NMF)
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&& (ntohs(fh->frag_off) & IP6_MF)));
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return (fh != NULL)
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&&
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(id_match(fraginfo->ids[0], fraginfo->ids[1],
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ntohl(fh->identification),
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!!(fraginfo->invflags & IP6T_FRAG_INV_IDS)))
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&&
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!((fraginfo->flags & IP6T_FRAG_RES)
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&& (fh->reserved || (ntohs(fh->frag_off) & 0x6)))
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&&
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!((fraginfo->flags & IP6T_FRAG_FST)
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&& (ntohs(fh->frag_off) & ~0x7))
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&&
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!((fraginfo->flags & IP6T_FRAG_MF)
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&& !(ntohs(fh->frag_off) & IP6_MF))
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&&
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!((fraginfo->flags & IP6T_FRAG_NMF)
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&& (ntohs(fh->frag_off) & IP6_MF));
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}
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/* Called when user tries to insert an entry of this type. */
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static int
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checkentry(const char *tablename,
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const void *ip,
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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 ip6t_frag *fraginfo = matchinfo;
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if (fraginfo->invflags & ~IP6T_FRAG_INV_MASK) {
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DEBUGP("ip6t_frag: unknown flags %X\n", fraginfo->invflags);
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return 0;
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}
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return 1;
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}
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static struct ip6t_match frag_match = {
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.name = "frag",
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.match = match,
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.matchsize = sizeof(struct ip6t_frag),
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.checkentry = checkentry,
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.me = THIS_MODULE,
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};
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static int __init ip6t_frag_init(void)
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{
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return ip6t_register_match(&frag_match);
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}
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static void __exit ip6t_frag_fini(void)
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{
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ip6t_unregister_match(&frag_match);
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}
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module_init(ip6t_frag_init);
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module_exit(ip6t_frag_fini);
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