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-rw-r--r--src/helpers/sane.c173
1 files changed, 173 insertions, 0 deletions
diff --git a/src/helpers/sane.c b/src/helpers/sane.c
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+++ b/src/helpers/sane.c
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+/*
+ * (C) 2013 by Pablo Neira Ayuso <pablo@netfilter.org>
+ *
+ * Port this helper to userspace.
+ */
+
+/* SANE connection tracking helper
+ * (SANE = Scanner Access Now Easy)
+ * For documentation about the SANE network protocol see
+ * http://www.sane-project.org/html/doc015.html
+ */
+
+/*
+ * Copyright (C) 2007 Red Hat, Inc.
+ * Author: Michal Schmidt <mschmidt@redhat.com>
+ * Based on the FTP conntrack helper (net/netfilter/nf_conntrack_ftp.c):
+ * (C) 1999-2001 Paul `Rusty' Russell
+ * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
+ * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
+ * (C) 2003 Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "conntrackd.h"
+#include "helper.h"
+#include "myct.h"
+#include "log.h"
+#include <errno.h>
+#include <netinet/ip.h>
+#define _GNU_SOURCE
+#include <netinet/tcp.h>
+#include <libmnl/libmnl.h>
+#include <libnetfilter_conntrack/libnetfilter_conntrack.h>
+#include <libnetfilter_queue/libnetfilter_queue.h>
+#include <libnetfilter_queue/libnetfilter_queue_tcp.h>
+#include <libnetfilter_queue/pktbuff.h>
+#include <linux/netfilter.h>
+
+enum sane_state {
+ SANE_STATE_NORMAL,
+ SANE_STATE_START_REQUESTED,
+};
+
+struct sane_request {
+ uint32_t RPC_code;
+#define SANE_NET_START 7 /* RPC code */
+
+ uint32_t handle;
+};
+
+struct sane_reply_net_start {
+ uint32_t status;
+#define SANE_STATUS_SUCCESS 0
+
+ uint16_t zero;
+ uint16_t port;
+ /* other fields aren't interesting for conntrack */
+};
+
+struct nf_ct_sane_master {
+ enum sane_state state;
+};
+
+static int
+sane_helper_cb(struct pkt_buff *pkt, uint32_t protoff,
+ struct myct *myct, uint32_t ctinfo)
+{
+ unsigned int dataoff, datalen;
+ const struct tcphdr *th;
+ void *sb_ptr;
+ int ret = NF_ACCEPT;
+ int dir = CTINFO2DIR(ctinfo);
+ struct nf_ct_sane_master *ct_sane_info = myct->priv_data;
+ struct nf_expect *exp;
+ struct sane_request *req;
+ struct sane_reply_net_start *reply;
+ union nfct_attr_grp_addr saddr;
+ union nfct_attr_grp_addr daddr;
+
+ /* Until there's been traffic both ways, don't look in packets. */
+ if (ctinfo != IP_CT_ESTABLISHED &&
+ ctinfo != IP_CT_ESTABLISHED_REPLY)
+ return NF_ACCEPT;
+
+ th = (struct tcphdr *)(pktb_network_header(pkt) + protoff);
+
+ /* No data? */
+ dataoff = protoff + th->doff * 4;
+ if (dataoff >= pktb_len(pkt))
+ return NF_ACCEPT;
+
+ datalen = pktb_len(pkt) - dataoff;
+
+ sb_ptr = pktb_network_header(pkt) + dataoff;
+
+ if (dir == MYCT_DIR_ORIG) {
+ if (datalen != sizeof(struct sane_request))
+ goto out;
+
+ req = sb_ptr;
+ if (req->RPC_code != htonl(SANE_NET_START)) {
+ /* Not an interesting command */
+ ct_sane_info->state = SANE_STATE_NORMAL;
+ goto out;
+ }
+
+ /* We're interested in the next reply */
+ ct_sane_info->state = SANE_STATE_START_REQUESTED;
+ goto out;
+ }
+
+ /* Is it a reply to an uninteresting command? */
+ if (ct_sane_info->state != SANE_STATE_START_REQUESTED)
+ goto out;
+
+ /* It's a reply to SANE_NET_START. */
+ ct_sane_info->state = SANE_STATE_NORMAL;
+
+ if (datalen < sizeof(struct sane_reply_net_start)) {
+ pr_debug("nf_ct_sane: NET_START reply too short\n");
+ goto out;
+ }
+
+ reply = sb_ptr;
+ if (reply->status != htonl(SANE_STATUS_SUCCESS)) {
+ /* saned refused the command */
+ pr_debug("nf_ct_sane: unsuccessful SANE_STATUS = %u\n",
+ ntohl(reply->status));
+ goto out;
+ }
+
+ /* Invalid saned reply? Ignore it. */
+ if (reply->zero != 0)
+ goto out;
+
+ exp = nfexp_new();
+ if (exp == NULL)
+ return NF_DROP;
+
+ cthelper_get_addr_src(myct->ct, MYCT_DIR_ORIG, &saddr);
+ cthelper_get_addr_dst(myct->ct, MYCT_DIR_ORIG, &daddr);
+
+ if (cthelper_expect_init(exp, myct->ct, 0, &saddr, &daddr,
+ IPPROTO_TCP, NULL, &reply->port, 0)) {
+ nfexp_destroy(exp);
+ return NF_DROP;
+ }
+ myct->exp = exp;
+out:
+ return ret;
+}
+
+static struct ctd_helper sane_helper = {
+ .name = "sane",
+ .l4proto = IPPROTO_TCP,
+ .priv_data_len = sizeof(struct nf_ct_sane_master),
+ .cb = sane_helper_cb,
+ .policy = {
+ [0] = {
+ .name = "sane",
+ .expect_max = 1,
+ .expect_timeout = 5 * 60,
+ },
+ },
+};
+
+static void __attribute__ ((constructor)) sane_init(void)
+{
+ helper_register(&sane_helper);
+}