1 files changed, 401 insertions, 0 deletions

diff --git a/net/ipv4/netfilter/ip_nat_helper_pptp.c b/net/ipv4/netfilter/ip_nat_helper_pptp.c
new file mode 100644
index 00000000000000..3cdd0684d30d32
--- /dev/null
+++ b/net/ipv4/netfilter/ip_nat_helper_pptp.c
@@ -0,0 +1,401 @@
+/*
+ * ip_nat_pptp.c	- Version 3.0
+ *
+ * NAT support for PPTP (Point to Point Tunneling Protocol).
+ * PPTP is a a protocol for creating virtual private networks.
+ * It is a specification defined by Microsoft and some vendors
+ * working with Microsoft.  PPTP is built on top of a modified
+ * version of the Internet Generic Routing Encapsulation Protocol.
+ * GRE is defined in RFC 1701 and RFC 1702.  Documentation of
+ * PPTP can be found in RFC 2637
+ *
+ * (C) 2000-2005 by Harald Welte <laforge@gnumonks.org>
+ *
+ * Development of this code funded by Astaro AG (http://www.astaro.com/)
+ *
+ * TODO: - NAT to a unique tuple, not to TCP source port
+ * 	   (needs netfilter tuple reservation)
+ *
+ * Changes:
+ *     2002-02-10 - Version 1.3
+ *       - Use ip_nat_mangle_tcp_packet() because of cloned skb's
+ *	   in local connections (Philip Craig <philipc@snapgear.com>)
+ *       - add checks for magicCookie and pptp version
+ *       - make argument list of pptp_{out,in}bound_packet() shorter
+ *       - move to C99 style initializers
+ *       - print version number at module loadtime
+ *     2003-09-22 - Version 1.5
+ *       - use SNATed tcp sourceport as callid, since we get called before
+ *	   TCP header is mangled (Philip Craig <philipc@snapgear.com>)
+ *     2004-10-22 - Version 2.0
+ *       - kernel 2.6.x version
+ *     2005-06-10 - Version 3.0
+ *       - kernel >= 2.6.11 version,
+ *	   funded by Oxcoda NetBox Blue (http://www.netboxblue.com/)
+ * 
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/ip.h>
+#include <linux/tcp.h>
+#include <net/tcp.h>
+
+#include <linux/netfilter_ipv4/ip_nat.h>
+#include <linux/netfilter_ipv4/ip_nat_rule.h>
+#include <linux/netfilter_ipv4/ip_nat_helper.h>
+#include <linux/netfilter_ipv4/ip_nat_pptp.h>
+#include <linux/netfilter_ipv4/ip_conntrack_core.h>
+#include <linux/netfilter_ipv4/ip_conntrack_helper.h>
+#include <linux/netfilter_ipv4/ip_conntrack_proto_gre.h>
+#include <linux/netfilter_ipv4/ip_conntrack_pptp.h>
+
+#define IP_NAT_PPTP_VERSION "3.0"
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
+MODULE_DESCRIPTION("Netfilter NAT helper module for PPTP");
+
+
+#if 0
+extern const char *pptp_msg_name[];
+#define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s: " format, __FILE__, \
+				       __FUNCTION__, ## args)
+#else
+#define DEBUGP(format, args...)
+#endif
+
+static void pptp_nat_expected(struct ip_conntrack *ct,
+			      struct ip_conntrack_expect *exp)
+{
+	struct ip_conntrack *master = ct->master;
+	struct ip_conntrack_expect *other_exp;
+	struct ip_conntrack_tuple t;
+	struct ip_ct_pptp_master *ct_pptp_info;
+	struct ip_nat_pptp *nat_pptp_info;
+
+	ct_pptp_info = &master->help.ct_pptp_info;
+	nat_pptp_info = &master->nat.help.nat_pptp_info;
+
+	/* And here goes the grand finale of corrosion... */
+
+	if (exp->dir == IP_CT_DIR_ORIGINAL) {
+		DEBUGP("we are PNS->PAC\n");
+		/* therefore, build tuple for PAC->PNS */
+		t.src.ip = master->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip;
+		t.src.u.gre.key = htons(master->help.ct_pptp_info.pac_call_id);
+		t.dst.ip = master->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip;
+		t.dst.u.gre.key = htons(master->help.ct_pptp_info.pns_call_id);
+		t.dst.protonum = IPPROTO_GRE;
+	} else {
+		DEBUGP("we are PAC->PNS\n");
+		/* build tuple for PNS->PAC */
+		t.src.ip = master->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip;
+		t.src.u.gre.key = 
+			htons(master->nat.help.nat_pptp_info.pns_call_id);
+		t.dst.ip = master->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip;
+		t.dst.u.gre.key = 
+			htons(master->nat.help.nat_pptp_info.pac_call_id);
+		t.dst.protonum = IPPROTO_GRE;
+	}
+
+	DEBUGP("trying to unexpect other dir: ");
+	DUMP_TUPLE(&t);
+	other_exp = ip_conntrack_expect_find(&t);
+	if (other_exp) {
+		ip_conntrack_unexpect_related(other_exp);
+		ip_conntrack_expect_put(other_exp);
+		DEBUGP("success\n");
+	} else {
+		DEBUGP("not found!\n");
+	}
+
+	ip_nat_follow_master(ct, exp);
+}
+
+/* outbound packets == from PNS to PAC */
+static int
+pptp_outbound_pkt(struct sk_buff **pskb,
+		  struct ip_conntrack *ct,
+		  enum ip_conntrack_info ctinfo,
+		  struct PptpControlHeader *ctlh,
+		  union pptp_ctrl_union *pptpReq)
+
+{
+	struct ip_ct_pptp_master *ct_pptp_info = &ct->help.ct_pptp_info;
+	struct ip_nat_pptp *nat_pptp_info = &ct->nat.help.nat_pptp_info;
+
+	u_int16_t msg, *cid = NULL, new_callid;
+
+	new_callid = htons(ct_pptp_info->pns_call_id);
+	
+	switch (msg = ntohs(ctlh->messageType)) {
+		case PPTP_OUT_CALL_REQUEST:
+			cid = &pptpReq->ocreq.callID;
+			/* FIXME: ideally we would want to reserve a call ID
+			 * here.  current netfilter NAT core is not able to do
+			 * this :( For now we use TCP source port. This breaks
+			 * multiple calls within one control session */
+
+			/* save original call ID in nat_info */
+			nat_pptp_info->pns_call_id = ct_pptp_info->pns_call_id;
+
+			/* don't use tcph->source since we are at a DSTmanip
+			 * hook (e.g. PREROUTING) and pkt is not mangled yet */
+			new_callid = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u.tcp.port;
+
+			/* save new call ID in ct info */
+			ct_pptp_info->pns_call_id = ntohs(new_callid);
+			break;
+		case PPTP_IN_CALL_REPLY:
+			cid = &pptpReq->icreq.callID;
+			break;
+		case PPTP_CALL_CLEAR_REQUEST:
+			cid = &pptpReq->clrreq.callID;
+			break;
+		default:
+			DEBUGP("unknown outbound packet 0x%04x:%s\n", msg,
+			      (msg <= PPTP_MSG_MAX)? 
+			      pptp_msg_name[msg]:pptp_msg_name[0]);
+			/* fall through */
+
+		case PPTP_SET_LINK_INFO:
+			/* only need to NAT in case PAC is behind NAT box */
+		case PPTP_START_SESSION_REQUEST:
+		case PPTP_START_SESSION_REPLY:
+		case PPTP_STOP_SESSION_REQUEST:
+		case PPTP_STOP_SESSION_REPLY:
+		case PPTP_ECHO_REQUEST:
+		case PPTP_ECHO_REPLY:
+			/* no need to alter packet */
+			return NF_ACCEPT;
+	}
+
+	/* only OUT_CALL_REQUEST, IN_CALL_REPLY, CALL_CLEAR_REQUEST pass
+	 * down to here */
+
+	IP_NF_ASSERT(cid);
+
+	DEBUGP("altering call id from 0x%04x to 0x%04x\n",
+		ntohs(*cid), ntohs(new_callid));
+
+	/* mangle packet */
+	if (ip_nat_mangle_tcp_packet(pskb, ct, ctinfo,
+		(void *)cid - ((void *)ctlh - sizeof(struct pptp_pkt_hdr)),
+				 	sizeof(new_callid), 
+					(char *)&new_callid,
+				 	sizeof(new_callid)) == 0)
+		return NF_DROP;
+
+	return NF_ACCEPT;
+}
+
+static int
+pptp_exp_gre(struct ip_conntrack_expect *expect_orig,
+	     struct ip_conntrack_expect *expect_reply)
+{
+	struct ip_ct_pptp_master *ct_pptp_info = 
+				&expect_orig->master->help.ct_pptp_info;
+	struct ip_nat_pptp *nat_pptp_info = 
+				&expect_orig->master->nat.help.nat_pptp_info;
+
+	struct ip_conntrack *ct = expect_orig->master;
+
+	struct ip_conntrack_tuple inv_t;
+	struct ip_conntrack_tuple *orig_t, *reply_t;
+
+	/* save original PAC call ID in nat_info */
+	nat_pptp_info->pac_call_id = ct_pptp_info->pac_call_id;
+
+	/* alter expectation */
+	orig_t = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
+	reply_t = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
+
+	/* alter expectation for PNS->PAC direction */
+	invert_tuplepr(&inv_t, &expect_orig->tuple);
+	expect_orig->saved_proto.gre.key = htons(nat_pptp_info->pac_call_id);
+	expect_orig->tuple.src.u.gre.key = htons(nat_pptp_info->pns_call_id);
+	expect_orig->tuple.dst.u.gre.key = htons(ct_pptp_info->pac_call_id);
+	inv_t.src.ip = reply_t->src.ip;
+	inv_t.dst.ip = reply_t->dst.ip;
+	inv_t.src.u.gre.key = htons(nat_pptp_info->pac_call_id);
+	inv_t.dst.u.gre.key = htons(ct_pptp_info->pns_call_id);
+
+	if (!ip_conntrack_expect_related(expect_orig)) {
+		DEBUGP("successfully registered expect\n");
+	} else {
+		DEBUGP("can't expect_related(expect_orig)\n");
+		return 1;
+	}
+
+	/* alter expectation for PAC->PNS direction */
+	invert_tuplepr(&inv_t, &expect_reply->tuple);
+	expect_reply->saved_proto.gre.key = htons(nat_pptp_info->pns_call_id);
+	expect_reply->tuple.src.u.gre.key = htons(nat_pptp_info->pac_call_id);
+	expect_reply->tuple.dst.u.gre.key = htons(ct_pptp_info->pns_call_id);
+	inv_t.src.ip = orig_t->src.ip;
+	inv_t.dst.ip = orig_t->dst.ip;
+	inv_t.src.u.gre.key = htons(nat_pptp_info->pns_call_id);
+	inv_t.dst.u.gre.key = htons(ct_pptp_info->pac_call_id);
+
+	if (!ip_conntrack_expect_related(expect_reply)) {
+		DEBUGP("successfully registered expect\n");
+	} else {
+		DEBUGP("can't expect_related(expect_reply)\n");
+		ip_conntrack_unexpect_related(expect_orig);
+		return 1;
+	}
+
+	if (ip_ct_gre_keymap_add(ct, &expect_reply->tuple, 0) < 0) {
+		DEBUGP("can't register original keymap\n");
+		ip_conntrack_unexpect_related(expect_orig);
+		ip_conntrack_unexpect_related(expect_reply);
+		return 1;
+	}
+
+	if (ip_ct_gre_keymap_add(ct, &inv_t, 1) < 0) {
+		DEBUGP("can't register reply keymap\n");
+		ip_conntrack_unexpect_related(expect_orig);
+		ip_conntrack_unexpect_related(expect_reply);
+		ip_ct_gre_keymap_destroy(ct);
+		return 1;
+	}
+
+	return 0;
+}
+
+/* inbound packets == from PAC to PNS */
+static int
+pptp_inbound_pkt(struct sk_buff **pskb,
+		 struct ip_conntrack *ct,
+		 enum ip_conntrack_info ctinfo,
+		 struct PptpControlHeader *ctlh,
+		 union pptp_ctrl_union *pptpReq)
+{
+	struct ip_nat_pptp *nat_pptp_info = &ct->nat.help.nat_pptp_info;
+	u_int16_t msg, new_cid = 0, new_pcid, *pcid = NULL, *cid = NULL;
+
+	int ret = NF_ACCEPT, rv;
+
+	new_pcid = htons(nat_pptp_info->pns_call_id);
+
+	switch (msg = ntohs(ctlh->messageType)) {
+	case PPTP_OUT_CALL_REPLY:
+		pcid = &pptpReq->ocack.peersCallID;	
+		cid = &pptpReq->ocack.callID;
+		break;
+	case PPTP_IN_CALL_CONNECT:
+		pcid = &pptpReq->iccon.peersCallID;
+		break;
+	case PPTP_IN_CALL_REQUEST:
+		/* only need to nat in case PAC is behind NAT box */
+		break;
+	case PPTP_WAN_ERROR_NOTIFY:
+		pcid = &pptpReq->wanerr.peersCallID;
+		break;
+	case PPTP_CALL_DISCONNECT_NOTIFY:
+		pcid = &pptpReq->disc.callID;
+		break;
+	case PPTP_SET_LINK_INFO:
+		pcid = &pptpReq->setlink.peersCallID;
+		break;
+
+	default:
+		DEBUGP("unknown inbound packet %s\n", (msg <= PPTP_MSG_MAX)? 
+			pptp_msg_name[msg]:pptp_msg_name[0]);
+		/* fall through */
+
+	case PPTP_START_SESSION_REQUEST:
+	case PPTP_START_SESSION_REPLY:
+	case PPTP_STOP_SESSION_REQUEST:
+	case PPTP_STOP_SESSION_REPLY:
+	case PPTP_ECHO_REQUEST:
+	case PPTP_ECHO_REPLY:
+		/* no need to alter packet */
+		return NF_ACCEPT;
+	}
+
+	/* only OUT_CALL_REPLY, IN_CALL_CONNECT, IN_CALL_REQUEST,
+	 * WAN_ERROR_NOTIFY, CALL_DISCONNECT_NOTIFY pass down here */
+
+	/* mangle packet */
+	IP_NF_ASSERT(pcid);
+	DEBUGP("altering peer call id from 0x%04x to 0x%04x\n",
+		ntohs(*pcid), ntohs(new_pcid));
+	
+	rv = ip_nat_mangle_tcp_packet(pskb, ct, ctinfo, 
+				      (void *)pcid - ((void *)ctlh - sizeof(struct pptp_pkt_hdr)),
+				      sizeof(new_pcid), (char *)&new_pcid, 
+				      sizeof(new_pcid));
+	if (rv != NF_ACCEPT) 
+		return rv;
+
+	if (new_cid) {
+		IP_NF_ASSERT(cid);
+		DEBUGP("altering call id from 0x%04x to 0x%04x\n",
+			ntohs(*cid), ntohs(new_cid));
+		rv = ip_nat_mangle_tcp_packet(pskb, ct, ctinfo, 
+					      (void *)cid - ((void *)ctlh - sizeof(struct pptp_pkt_hdr)), 
+					      sizeof(new_cid),
+					      (char *)&new_cid, 
+					      sizeof(new_cid));
+		if (rv != NF_ACCEPT)
+			return rv;
+	}
+
+	/* check for earlier return value of 'switch' above */
+	if (ret != NF_ACCEPT)
+		return ret;
+
+	/* great, at least we don't need to resize packets */
+	return NF_ACCEPT;
+}
+
+
+extern int __init ip_nat_proto_gre_init(void);
+extern void __exit ip_nat_proto_gre_fini(void);
+
+static int __init init(void)
+{
+	int ret;
+
+	DEBUGP("%s: registering NAT helper\n", __FILE__);
+
+	ret = ip_nat_proto_gre_init();
+	if (ret < 0)
+		return ret;
+
+	BUG_ON(ip_nat_pptp_hook_outbound);
+	ip_nat_pptp_hook_outbound = &pptp_outbound_pkt;
+
+	BUG_ON(ip_nat_pptp_hook_inbound);
+	ip_nat_pptp_hook_inbound = &pptp_inbound_pkt;
+
+	BUG_ON(ip_nat_pptp_hook_exp_gre);
+	ip_nat_pptp_hook_exp_gre = &pptp_exp_gre;
+
+	BUG_ON(ip_nat_pptp_hook_expectfn);
+	ip_nat_pptp_hook_expectfn = &pptp_nat_expected;
+
+	printk("ip_nat_pptp version %s loaded\n", IP_NAT_PPTP_VERSION);
+	return 0;
+}
+
+static void __exit fini(void)
+{
+	DEBUGP("cleanup_module\n" );
+
+	ip_nat_pptp_hook_expectfn = NULL;
+	ip_nat_pptp_hook_exp_gre = NULL;
+	ip_nat_pptp_hook_inbound = NULL;
+	ip_nat_pptp_hook_outbound = NULL;
+
+	ip_nat_proto_gre_fini();
+	/* Make sure noone calls it, meanwhile */
+	synchronize_net();
+
+	printk("ip_nat_pptp version %s unloaded\n", IP_NAT_PPTP_VERSION);
+}
+
+module_init(init);
+module_exit(fini);