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-rw-r--r--net/netfilter/xt_tcpudp.c342
1 files changed, 342 insertions, 0 deletions
diff --git a/net/netfilter/xt_tcpudp.c b/net/netfilter/xt_tcpudp.c
new file mode 100644
index 000000000..e8991130a
--- /dev/null
+++ b/net/netfilter/xt_tcpudp.c
@@ -0,0 +1,342 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include <linux/types.h>
+#include <linux/module.h>
+#include <net/ip.h>
+#include <linux/ipv6.h>
+#include <linux/icmp.h>
+#include <net/ipv6.h>
+#include <net/tcp.h>
+#include <net/udp.h>
+#include <linux/netfilter/x_tables.h>
+#include <linux/netfilter/xt_tcpudp.h>
+#include <linux/netfilter_ipv4/ip_tables.h>
+#include <linux/netfilter_ipv6/ip6_tables.h>
+
+MODULE_DESCRIPTION("Xtables: TCP, UDP and UDP-Lite match");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("xt_tcp");
+MODULE_ALIAS("xt_udp");
+MODULE_ALIAS("ipt_udp");
+MODULE_ALIAS("ipt_tcp");
+MODULE_ALIAS("ip6t_udp");
+MODULE_ALIAS("ip6t_tcp");
+MODULE_ALIAS("ipt_icmp");
+MODULE_ALIAS("ip6t_icmp6");
+
+/* Returns 1 if the port is matched by the range, 0 otherwise */
+static inline bool
+port_match(u_int16_t min, u_int16_t max, u_int16_t port, bool invert)
+{
+ return (port >= min && port <= max) ^ invert;
+}
+
+static bool
+tcp_find_option(u_int8_t option,
+ const struct sk_buff *skb,
+ unsigned int protoff,
+ unsigned int optlen,
+ bool invert,
+ bool *hotdrop)
+{
+ /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */
+ const u_int8_t *op;
+ u_int8_t _opt[60 - sizeof(struct tcphdr)];
+ unsigned int i;
+
+ pr_debug("finding option\n");
+
+ if (!optlen)
+ return invert;
+
+ /* If we don't have the whole header, drop packet. */
+ op = skb_header_pointer(skb, protoff + sizeof(struct tcphdr),
+ optlen, _opt);
+ if (op == NULL) {
+ *hotdrop = true;
+ return false;
+ }
+
+ for (i = 0; i < optlen; ) {
+ if (op[i] == option) return !invert;
+ if (op[i] < 2) i++;
+ else i += op[i+1]?:1;
+ }
+
+ return invert;
+}
+
+static bool tcp_mt(const struct sk_buff *skb, struct xt_action_param *par)
+{
+ const struct tcphdr *th;
+ struct tcphdr _tcph;
+ const struct xt_tcp *tcpinfo = par->matchinfo;
+
+ if (par->fragoff != 0) {
+ /* To quote Alan:
+
+ Don't allow a fragment of TCP 8 bytes in. Nobody normal
+ causes this. Its a cracker trying to break in by doing a
+ flag overwrite to pass the direction checks.
+ */
+ if (par->fragoff == 1) {
+ pr_debug("Dropping evil TCP offset=1 frag.\n");
+ par->hotdrop = true;
+ }
+ /* Must not be a fragment. */
+ return false;
+ }
+
+ th = skb_header_pointer(skb, par->thoff, sizeof(_tcph), &_tcph);
+ if (th == NULL) {
+ /* We've been asked to examine this packet, and we
+ can't. Hence, no choice but to drop. */
+ pr_debug("Dropping evil TCP offset=0 tinygram.\n");
+ par->hotdrop = true;
+ return false;
+ }
+
+ if (!port_match(tcpinfo->spts[0], tcpinfo->spts[1],
+ ntohs(th->source),
+ !!(tcpinfo->invflags & XT_TCP_INV_SRCPT)))
+ return false;
+ if (!port_match(tcpinfo->dpts[0], tcpinfo->dpts[1],
+ ntohs(th->dest),
+ !!(tcpinfo->invflags & XT_TCP_INV_DSTPT)))
+ return false;
+ if (!NF_INVF(tcpinfo, XT_TCP_INV_FLAGS,
+ (((unsigned char *)th)[13] & tcpinfo->flg_mask) == tcpinfo->flg_cmp))
+ return false;
+ if (tcpinfo->option) {
+ if (th->doff * 4 < sizeof(_tcph)) {
+ par->hotdrop = true;
+ return false;
+ }
+ if (!tcp_find_option(tcpinfo->option, skb, par->thoff,
+ th->doff*4 - sizeof(_tcph),
+ tcpinfo->invflags & XT_TCP_INV_OPTION,
+ &par->hotdrop))
+ return false;
+ }
+ return true;
+}
+
+static int tcp_mt_check(const struct xt_mtchk_param *par)
+{
+ const struct xt_tcp *tcpinfo = par->matchinfo;
+
+ /* Must specify no unknown invflags */
+ return (tcpinfo->invflags & ~XT_TCP_INV_MASK) ? -EINVAL : 0;
+}
+
+static bool udp_mt(const struct sk_buff *skb, struct xt_action_param *par)
+{
+ const struct udphdr *uh;
+ struct udphdr _udph;
+ const struct xt_udp *udpinfo = par->matchinfo;
+
+ /* Must not be a fragment. */
+ if (par->fragoff != 0)
+ return false;
+
+ uh = skb_header_pointer(skb, par->thoff, sizeof(_udph), &_udph);
+ if (uh == NULL) {
+ /* We've been asked to examine this packet, and we
+ can't. Hence, no choice but to drop. */
+ pr_debug("Dropping evil UDP tinygram.\n");
+ par->hotdrop = true;
+ return false;
+ }
+
+ return port_match(udpinfo->spts[0], udpinfo->spts[1],
+ ntohs(uh->source),
+ !!(udpinfo->invflags & XT_UDP_INV_SRCPT))
+ && port_match(udpinfo->dpts[0], udpinfo->dpts[1],
+ ntohs(uh->dest),
+ !!(udpinfo->invflags & XT_UDP_INV_DSTPT));
+}
+
+static int udp_mt_check(const struct xt_mtchk_param *par)
+{
+ const struct xt_udp *udpinfo = par->matchinfo;
+
+ /* Must specify no unknown invflags */
+ return (udpinfo->invflags & ~XT_UDP_INV_MASK) ? -EINVAL : 0;
+}
+
+/* Returns 1 if the type and code is matched by the range, 0 otherwise */
+static bool type_code_in_range(u8 test_type, u8 min_code, u8 max_code,
+ u8 type, u8 code)
+{
+ return type == test_type && code >= min_code && code <= max_code;
+}
+
+static bool icmp_type_code_match(u8 test_type, u8 min_code, u8 max_code,
+ u8 type, u8 code, bool invert)
+{
+ return (test_type == 0xFF ||
+ type_code_in_range(test_type, min_code, max_code, type, code))
+ ^ invert;
+}
+
+static bool icmp6_type_code_match(u8 test_type, u8 min_code, u8 max_code,
+ u8 type, u8 code, bool invert)
+{
+ return type_code_in_range(test_type, min_code, max_code, type, code) ^ invert;
+}
+
+static bool
+icmp_match(const struct sk_buff *skb, struct xt_action_param *par)
+{
+ const struct icmphdr *ic;
+ struct icmphdr _icmph;
+ const struct ipt_icmp *icmpinfo = par->matchinfo;
+
+ /* Must not be a fragment. */
+ if (par->fragoff != 0)
+ return false;
+
+ ic = skb_header_pointer(skb, par->thoff, sizeof(_icmph), &_icmph);
+ if (!ic) {
+ /* We've been asked to examine this packet, and we
+ * can't. Hence, no choice but to drop.
+ */
+ par->hotdrop = true;
+ return false;
+ }
+
+ return icmp_type_code_match(icmpinfo->type,
+ icmpinfo->code[0],
+ icmpinfo->code[1],
+ ic->type, ic->code,
+ !!(icmpinfo->invflags & IPT_ICMP_INV));
+}
+
+static bool
+icmp6_match(const struct sk_buff *skb, struct xt_action_param *par)
+{
+ const struct icmp6hdr *ic;
+ struct icmp6hdr _icmph;
+ const struct ip6t_icmp *icmpinfo = par->matchinfo;
+
+ /* Must not be a fragment. */
+ if (par->fragoff != 0)
+ return false;
+
+ ic = skb_header_pointer(skb, par->thoff, sizeof(_icmph), &_icmph);
+ if (!ic) {
+ /* We've been asked to examine this packet, and we
+ * can't. Hence, no choice but to drop.
+ */
+ par->hotdrop = true;
+ return false;
+ }
+
+ return icmp6_type_code_match(icmpinfo->type,
+ icmpinfo->code[0],
+ icmpinfo->code[1],
+ ic->icmp6_type, ic->icmp6_code,
+ !!(icmpinfo->invflags & IP6T_ICMP_INV));
+}
+
+static int icmp_checkentry(const struct xt_mtchk_param *par)
+{
+ const struct ipt_icmp *icmpinfo = par->matchinfo;
+
+ return (icmpinfo->invflags & ~IPT_ICMP_INV) ? -EINVAL : 0;
+}
+
+static int icmp6_checkentry(const struct xt_mtchk_param *par)
+{
+ const struct ip6t_icmp *icmpinfo = par->matchinfo;
+
+ return (icmpinfo->invflags & ~IP6T_ICMP_INV) ? -EINVAL : 0;
+}
+
+static struct xt_match tcpudp_mt_reg[] __read_mostly = {
+ {
+ .name = "tcp",
+ .family = NFPROTO_IPV4,
+ .checkentry = tcp_mt_check,
+ .match = tcp_mt,
+ .matchsize = sizeof(struct xt_tcp),
+ .proto = IPPROTO_TCP,
+ .me = THIS_MODULE,
+ },
+ {
+ .name = "tcp",
+ .family = NFPROTO_IPV6,
+ .checkentry = tcp_mt_check,
+ .match = tcp_mt,
+ .matchsize = sizeof(struct xt_tcp),
+ .proto = IPPROTO_TCP,
+ .me = THIS_MODULE,
+ },
+ {
+ .name = "udp",
+ .family = NFPROTO_IPV4,
+ .checkentry = udp_mt_check,
+ .match = udp_mt,
+ .matchsize = sizeof(struct xt_udp),
+ .proto = IPPROTO_UDP,
+ .me = THIS_MODULE,
+ },
+ {
+ .name = "udp",
+ .family = NFPROTO_IPV6,
+ .checkentry = udp_mt_check,
+ .match = udp_mt,
+ .matchsize = sizeof(struct xt_udp),
+ .proto = IPPROTO_UDP,
+ .me = THIS_MODULE,
+ },
+ {
+ .name = "udplite",
+ .family = NFPROTO_IPV4,
+ .checkentry = udp_mt_check,
+ .match = udp_mt,
+ .matchsize = sizeof(struct xt_udp),
+ .proto = IPPROTO_UDPLITE,
+ .me = THIS_MODULE,
+ },
+ {
+ .name = "udplite",
+ .family = NFPROTO_IPV6,
+ .checkentry = udp_mt_check,
+ .match = udp_mt,
+ .matchsize = sizeof(struct xt_udp),
+ .proto = IPPROTO_UDPLITE,
+ .me = THIS_MODULE,
+ },
+ {
+ .name = "icmp",
+ .match = icmp_match,
+ .matchsize = sizeof(struct ipt_icmp),
+ .checkentry = icmp_checkentry,
+ .proto = IPPROTO_ICMP,
+ .family = NFPROTO_IPV4,
+ .me = THIS_MODULE,
+ },
+ {
+ .name = "icmp6",
+ .match = icmp6_match,
+ .matchsize = sizeof(struct ip6t_icmp),
+ .checkentry = icmp6_checkentry,
+ .proto = IPPROTO_ICMPV6,
+ .family = NFPROTO_IPV6,
+ .me = THIS_MODULE,
+ },
+};
+
+static int __init tcpudp_mt_init(void)
+{
+ return xt_register_matches(tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg));
+}
+
+static void __exit tcpudp_mt_exit(void)
+{
+ xt_unregister_matches(tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg));
+}
+
+module_init(tcpudp_mt_init);
+module_exit(tcpudp_mt_exit);
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