// SPDX-License-Identifier: GPL-2.0-only
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/* SANE connection tracking helper
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* (SANE = Scanner Access Now Easy)
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* For documentation about the SANE network protocol see
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* http://www.sane-project.org/html/doc015.html
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*/
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/* Copyright (C) 2007 Red Hat, Inc.
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* Author: Michal Schmidt <mschmidt@redhat.com>
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* Based on the FTP conntrack helper (net/netfilter/nf_conntrack_ftp.c):
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* (C) 1999-2001 Paul `Rusty' Russell
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* (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
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* (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
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* (C) 2003 Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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#include <linux/moduleparam.h>
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#include <linux/netfilter.h>
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#include <linux/slab.h>
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#include <linux/in.h>
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#include <linux/tcp.h>
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#include <net/netfilter/nf_conntrack.h>
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#include <net/netfilter/nf_conntrack_helper.h>
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#include <net/netfilter/nf_conntrack_expect.h>
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#include <linux/netfilter/nf_conntrack_sane.h>
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#define HELPER_NAME "sane"
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Michal Schmidt <mschmidt@redhat.com>");
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MODULE_DESCRIPTION("SANE connection tracking helper");
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MODULE_ALIAS_NFCT_HELPER(HELPER_NAME);
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static char *sane_buffer;
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static DEFINE_SPINLOCK(nf_sane_lock);
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#define MAX_PORTS 8
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static u_int16_t ports[MAX_PORTS];
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static unsigned int ports_c;
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module_param_array(ports, ushort, &ports_c, 0400);
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struct sane_request {
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__be32 RPC_code;
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#define SANE_NET_START 7 /* RPC code */
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__be32 handle;
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};
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struct sane_reply_net_start {
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__be32 status;
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#define SANE_STATUS_SUCCESS 0
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__be16 zero;
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__be16 port;
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/* other fields aren't interesting for conntrack */
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};
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static int help(struct sk_buff *skb,
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unsigned int protoff,
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struct nf_conn *ct,
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enum ip_conntrack_info ctinfo)
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{
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unsigned int dataoff, datalen;
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const struct tcphdr *th;
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struct tcphdr _tcph;
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void *sb_ptr;
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int ret = NF_ACCEPT;
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int dir = CTINFO2DIR(ctinfo);
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struct nf_ct_sane_master *ct_sane_info = nfct_help_data(ct);
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struct nf_conntrack_expect *exp;
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struct nf_conntrack_tuple *tuple;
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struct sane_request *req;
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struct sane_reply_net_start *reply;
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/* Until there's been traffic both ways, don't look in packets. */
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if (ctinfo != IP_CT_ESTABLISHED &&
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ctinfo != IP_CT_ESTABLISHED_REPLY)
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return NF_ACCEPT;
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/* Not a full tcp header? */
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th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
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if (th == NULL)
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return NF_ACCEPT;
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/* No data? */
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dataoff = protoff + th->doff * 4;
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if (dataoff >= skb->len)
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return NF_ACCEPT;
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datalen = skb->len - dataoff;
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spin_lock_bh(&nf_sane_lock);
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sb_ptr = skb_header_pointer(skb, dataoff, datalen, sane_buffer);
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BUG_ON(sb_ptr == NULL);
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if (dir == IP_CT_DIR_ORIGINAL) {
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if (datalen != sizeof(struct sane_request))
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goto out;
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req = sb_ptr;
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if (req->RPC_code != htonl(SANE_NET_START)) {
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/* Not an interesting command */
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ct_sane_info->state = SANE_STATE_NORMAL;
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goto out;
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}
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/* We're interested in the next reply */
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ct_sane_info->state = SANE_STATE_START_REQUESTED;
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goto out;
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}
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/* Is it a reply to an uninteresting command? */
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if (ct_sane_info->state != SANE_STATE_START_REQUESTED)
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goto out;
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/* It's a reply to SANE_NET_START. */
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ct_sane_info->state = SANE_STATE_NORMAL;
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if (datalen < sizeof(struct sane_reply_net_start)) {
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pr_debug("NET_START reply too short\n");
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goto out;
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}
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reply = sb_ptr;
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if (reply->status != htonl(SANE_STATUS_SUCCESS)) {
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/* saned refused the command */
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pr_debug("unsuccessful SANE_STATUS = %u\n",
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ntohl(reply->status));
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goto out;
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}
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/* Invalid saned reply? Ignore it. */
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if (reply->zero != 0)
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goto out;
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exp = nf_ct_expect_alloc(ct);
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if (exp == NULL) {
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nf_ct_helper_log(skb, ct, "cannot alloc expectation");
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ret = NF_DROP;
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goto out;
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}
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tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
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nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, nf_ct_l3num(ct),
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&tuple->src.u3, &tuple->dst.u3,
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IPPROTO_TCP, NULL, &reply->port);
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pr_debug("expect: ");
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nf_ct_dump_tuple(&exp->tuple);
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/* Can't expect this? Best to drop packet now. */
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if (nf_ct_expect_related(exp, 0) != 0) {
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nf_ct_helper_log(skb, ct, "cannot add expectation");
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ret = NF_DROP;
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}
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nf_ct_expect_put(exp);
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out:
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spin_unlock_bh(&nf_sane_lock);
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return ret;
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}
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static struct nf_conntrack_helper sane[MAX_PORTS * 2] __read_mostly;
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static const struct nf_conntrack_expect_policy sane_exp_policy = {
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.max_expected = 1,
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.timeout = 5 * 60,
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};
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static void __exit nf_conntrack_sane_fini(void)
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{
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nf_conntrack_helpers_unregister(sane, ports_c * 2);
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kfree(sane_buffer);
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}
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static int __init nf_conntrack_sane_init(void)
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{
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int i, ret = 0;
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NF_CT_HELPER_BUILD_BUG_ON(sizeof(struct nf_ct_sane_master));
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sane_buffer = kmalloc(65536, GFP_KERNEL);
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if (!sane_buffer)
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return -ENOMEM;
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if (ports_c == 0)
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ports[ports_c++] = SANE_PORT;
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/* FIXME should be configurable whether IPv4 and IPv6 connections
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are tracked or not - YK */
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for (i = 0; i < ports_c; i++) {
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nf_ct_helper_init(&sane[2 * i], AF_INET, IPPROTO_TCP,
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HELPER_NAME, SANE_PORT, ports[i], ports[i],
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&sane_exp_policy, 0, help, NULL,
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THIS_MODULE);
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nf_ct_helper_init(&sane[2 * i + 1], AF_INET6, IPPROTO_TCP,
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HELPER_NAME, SANE_PORT, ports[i], ports[i],
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&sane_exp_policy, 0, help, NULL,
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THIS_MODULE);
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}
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ret = nf_conntrack_helpers_register(sane, ports_c * 2);
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if (ret < 0) {
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pr_err("failed to register helpers\n");
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kfree(sane_buffer);
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return ret;
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}
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return 0;
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}
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module_init(nf_conntrack_sane_init);
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module_exit(nf_conntrack_sane_fini);
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