f7108a20de
The function signatures for Xtables extensions have grown over time. It involves a lot of typing/replication, and also a bit of stack space even if they are not used. Realize an NFWS2008 idea and pack them into structs. The skb remains outside of the struct so gcc can continue to apply its optimizations. This patch does this for match extensions' match functions. A few ambiguities have also been addressed. The "offset" parameter for example has been renamed to "fragoff" (there are so many different offsets already) and "protoff" to "thoff" (there is more than just one protocol here, so clarify). Signed-off-by: Jan Engelhardt <jengelh@medozas.de> Signed-off-by: Patrick McHardy <kaber@trash.net>
249 lines
6.1 KiB
C
249 lines
6.1 KiB
C
#include <linux/types.h>
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#include <linux/module.h>
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#include <net/ip.h>
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#include <linux/ipv6.h>
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#include <net/ipv6.h>
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#include <net/tcp.h>
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#include <net/udp.h>
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#include <linux/netfilter/x_tables.h>
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#include <linux/netfilter/xt_tcpudp.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_DESCRIPTION("Xtables: TCP, UDP and UDP-Lite match");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS("xt_tcp");
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MODULE_ALIAS("xt_udp");
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MODULE_ALIAS("ipt_udp");
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MODULE_ALIAS("ipt_tcp");
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MODULE_ALIAS("ip6t_udp");
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MODULE_ALIAS("ip6t_tcp");
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#ifdef DEBUG_IP_FIREWALL_USER
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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 port is matched by the range, 0 otherwise */
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static inline bool
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port_match(u_int16_t min, u_int16_t max, u_int16_t port, bool invert)
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{
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return (port >= min && port <= max) ^ invert;
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}
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static bool
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tcp_find_option(u_int8_t option,
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const struct sk_buff *skb,
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unsigned int protoff,
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unsigned int optlen,
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bool invert,
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bool *hotdrop)
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{
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/* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */
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const u_int8_t *op;
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u_int8_t _opt[60 - sizeof(struct tcphdr)];
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unsigned int i;
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duprintf("tcp_match: finding option\n");
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if (!optlen)
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return invert;
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/* If we don't have the whole header, drop packet. */
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op = skb_header_pointer(skb, protoff + sizeof(struct tcphdr),
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optlen, _opt);
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if (op == NULL) {
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*hotdrop = true;
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return false;
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}
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for (i = 0; i < optlen; ) {
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if (op[i] == option) return !invert;
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if (op[i] < 2) i++;
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else i += op[i+1]?:1;
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}
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return invert;
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}
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static bool tcp_mt(const struct sk_buff *skb, const struct xt_match_param *par)
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{
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const struct tcphdr *th;
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struct tcphdr _tcph;
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const struct xt_tcp *tcpinfo = par->matchinfo;
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if (par->fragoff != 0) {
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/* To quote Alan:
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Don't allow a fragment of TCP 8 bytes in. Nobody normal
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causes this. Its a cracker trying to break in by doing a
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flag overwrite to pass the direction checks.
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*/
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if (par->fragoff == 1) {
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duprintf("Dropping evil TCP offset=1 frag.\n");
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*par->hotdrop = true;
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}
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/* Must not be a fragment. */
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return false;
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}
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#define FWINVTCP(bool, invflg) ((bool) ^ !!(tcpinfo->invflags & (invflg)))
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th = skb_header_pointer(skb, par->thoff, sizeof(_tcph), &_tcph);
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if (th == 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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duprintf("Dropping evil TCP offset=0 tinygram.\n");
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*par->hotdrop = true;
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return false;
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}
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if (!port_match(tcpinfo->spts[0], tcpinfo->spts[1],
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ntohs(th->source),
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!!(tcpinfo->invflags & XT_TCP_INV_SRCPT)))
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return false;
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if (!port_match(tcpinfo->dpts[0], tcpinfo->dpts[1],
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ntohs(th->dest),
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!!(tcpinfo->invflags & XT_TCP_INV_DSTPT)))
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return false;
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if (!FWINVTCP((((unsigned char *)th)[13] & tcpinfo->flg_mask)
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== tcpinfo->flg_cmp,
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XT_TCP_INV_FLAGS))
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return false;
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if (tcpinfo->option) {
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if (th->doff * 4 < sizeof(_tcph)) {
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*par->hotdrop = true;
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return false;
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}
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if (!tcp_find_option(tcpinfo->option, skb, par->thoff,
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th->doff*4 - sizeof(_tcph),
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tcpinfo->invflags & XT_TCP_INV_OPTION,
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par->hotdrop))
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return false;
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}
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return true;
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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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tcp_mt_check(const char *tablename, const void *info,
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const struct xt_match *match, void *matchinfo,
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unsigned int hook_mask)
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{
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const struct xt_tcp *tcpinfo = matchinfo;
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/* Must specify no unknown invflags */
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return !(tcpinfo->invflags & ~XT_TCP_INV_MASK);
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}
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static bool udp_mt(const struct sk_buff *skb, const struct xt_match_param *par)
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{
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const struct udphdr *uh;
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struct udphdr _udph;
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const struct xt_udp *udpinfo = par->matchinfo;
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/* Must not be a fragment. */
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if (par->fragoff != 0)
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return false;
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uh = skb_header_pointer(skb, par->thoff, sizeof(_udph), &_udph);
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if (uh == 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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duprintf("Dropping evil UDP tinygram.\n");
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*par->hotdrop = true;
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return false;
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}
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return port_match(udpinfo->spts[0], udpinfo->spts[1],
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ntohs(uh->source),
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!!(udpinfo->invflags & XT_UDP_INV_SRCPT))
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&& port_match(udpinfo->dpts[0], udpinfo->dpts[1],
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ntohs(uh->dest),
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!!(udpinfo->invflags & XT_UDP_INV_DSTPT));
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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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udp_mt_check(const char *tablename, const void *info,
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const struct xt_match *match, void *matchinfo,
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unsigned int hook_mask)
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{
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const struct xt_udp *udpinfo = matchinfo;
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/* Must specify no unknown invflags */
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return !(udpinfo->invflags & ~XT_UDP_INV_MASK);
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}
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static struct xt_match tcpudp_mt_reg[] __read_mostly = {
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{
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.name = "tcp",
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.family = NFPROTO_IPV4,
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.checkentry = tcp_mt_check,
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.match = tcp_mt,
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.matchsize = sizeof(struct xt_tcp),
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.proto = IPPROTO_TCP,
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.me = THIS_MODULE,
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},
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{
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.name = "tcp",
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.family = NFPROTO_IPV6,
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.checkentry = tcp_mt_check,
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.match = tcp_mt,
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.matchsize = sizeof(struct xt_tcp),
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.proto = IPPROTO_TCP,
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.me = THIS_MODULE,
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},
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{
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.name = "udp",
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.family = NFPROTO_IPV4,
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.checkentry = udp_mt_check,
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.match = udp_mt,
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.matchsize = sizeof(struct xt_udp),
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.proto = IPPROTO_UDP,
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.me = THIS_MODULE,
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},
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{
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.name = "udp",
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.family = NFPROTO_IPV6,
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.checkentry = udp_mt_check,
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.match = udp_mt,
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.matchsize = sizeof(struct xt_udp),
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.proto = IPPROTO_UDP,
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.me = THIS_MODULE,
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},
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{
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.name = "udplite",
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.family = NFPROTO_IPV4,
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.checkentry = udp_mt_check,
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.match = udp_mt,
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.matchsize = sizeof(struct xt_udp),
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.proto = IPPROTO_UDPLITE,
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.me = THIS_MODULE,
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},
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{
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.name = "udplite",
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.family = NFPROTO_IPV6,
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.checkentry = udp_mt_check,
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.match = udp_mt,
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.matchsize = sizeof(struct xt_udp),
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.proto = IPPROTO_UDPLITE,
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.me = THIS_MODULE,
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},
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};
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static int __init tcpudp_mt_init(void)
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{
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return xt_register_matches(tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg));
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}
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static void __exit tcpudp_mt_exit(void)
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{
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xt_unregister_matches(tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg));
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}
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module_init(tcpudp_mt_init);
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module_exit(tcpudp_mt_exit);
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