| // SPDX-License-Identifier: GPL-2.0-only |
| /* 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> |
| */ |
| |
| #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| |
| #include <linux/module.h> |
| #include <linux/moduleparam.h> |
| #include <linux/netfilter.h> |
| #include <linux/slab.h> |
| #include <linux/in.h> |
| #include <linux/tcp.h> |
| #include <net/netfilter/nf_conntrack.h> |
| #include <net/netfilter/nf_conntrack_helper.h> |
| #include <net/netfilter/nf_conntrack_expect.h> |
| #include <linux/netfilter/nf_conntrack_sane.h> |
| |
| #define HELPER_NAME "sane" |
| |
| MODULE_LICENSE("GPL"); |
| MODULE_AUTHOR("Michal Schmidt <mschmidt@redhat.com>"); |
| MODULE_DESCRIPTION("SANE connection tracking helper"); |
| MODULE_ALIAS_NFCT_HELPER(HELPER_NAME); |
| |
| #define MAX_PORTS 8 |
| static u_int16_t ports[MAX_PORTS]; |
| static unsigned int ports_c; |
| module_param_array(ports, ushort, &ports_c, 0400); |
| |
| struct sane_request { |
| __be32 RPC_code; |
| #define SANE_NET_START 7 /* RPC code */ |
| |
| __be32 handle; |
| }; |
| |
| struct sane_reply_net_start { |
| __be32 status; |
| #define SANE_STATUS_SUCCESS 0 |
| |
| __be16 zero; |
| __be16 port; |
| /* other fields aren't interesting for conntrack */ |
| }; |
| |
| static int help(struct sk_buff *skb, |
| unsigned int protoff, |
| struct nf_conn *ct, |
| enum ip_conntrack_info ctinfo) |
| { |
| unsigned int dataoff, datalen; |
| const struct tcphdr *th; |
| struct tcphdr _tcph; |
| int ret = NF_ACCEPT; |
| int dir = CTINFO2DIR(ctinfo); |
| struct nf_ct_sane_master *ct_sane_info = nfct_help_data(ct); |
| struct nf_conntrack_expect *exp; |
| struct nf_conntrack_tuple *tuple; |
| struct sane_reply_net_start *reply; |
| union { |
| struct sane_request req; |
| struct sane_reply_net_start repl; |
| } buf; |
| |
| /* 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; |
| |
| /* Not a full tcp header? */ |
| th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph); |
| if (th == NULL) |
| return NF_ACCEPT; |
| |
| /* No data? */ |
| dataoff = protoff + th->doff * 4; |
| if (dataoff >= skb->len) |
| return NF_ACCEPT; |
| |
| datalen = skb->len - dataoff; |
| if (dir == IP_CT_DIR_ORIGINAL) { |
| const struct sane_request *req; |
| |
| if (datalen != sizeof(struct sane_request)) |
| return NF_ACCEPT; |
| |
| req = skb_header_pointer(skb, dataoff, datalen, &buf.req); |
| if (!req) |
| return NF_ACCEPT; |
| |
| if (req->RPC_code != htonl(SANE_NET_START)) { |
| /* Not an interesting command */ |
| WRITE_ONCE(ct_sane_info->state, SANE_STATE_NORMAL); |
| return NF_ACCEPT; |
| } |
| |
| /* We're interested in the next reply */ |
| WRITE_ONCE(ct_sane_info->state, SANE_STATE_START_REQUESTED); |
| return NF_ACCEPT; |
| } |
| |
| /* IP_CT_DIR_REPLY */ |
| |
| /* Is it a reply to an uninteresting command? */ |
| if (READ_ONCE(ct_sane_info->state) != SANE_STATE_START_REQUESTED) |
| return NF_ACCEPT; |
| |
| /* It's a reply to SANE_NET_START. */ |
| WRITE_ONCE(ct_sane_info->state, SANE_STATE_NORMAL); |
| |
| if (datalen < sizeof(struct sane_reply_net_start)) { |
| pr_debug("NET_START reply too short\n"); |
| return NF_ACCEPT; |
| } |
| |
| datalen = sizeof(struct sane_reply_net_start); |
| |
| reply = skb_header_pointer(skb, dataoff, datalen, &buf.repl); |
| if (!reply) |
| return NF_ACCEPT; |
| |
| if (reply->status != htonl(SANE_STATUS_SUCCESS)) { |
| /* saned refused the command */ |
| pr_debug("unsuccessful SANE_STATUS = %u\n", |
| ntohl(reply->status)); |
| return NF_ACCEPT; |
| } |
| |
| /* Invalid saned reply? Ignore it. */ |
| if (reply->zero != 0) |
| return NF_ACCEPT; |
| |
| exp = nf_ct_expect_alloc(ct); |
| if (exp == NULL) { |
| nf_ct_helper_log(skb, ct, "cannot alloc expectation"); |
| return NF_DROP; |
| } |
| |
| tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple; |
| nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, nf_ct_l3num(ct), |
| &tuple->src.u3, &tuple->dst.u3, |
| IPPROTO_TCP, NULL, &reply->port); |
| |
| pr_debug("expect: "); |
| nf_ct_dump_tuple(&exp->tuple); |
| |
| /* Can't expect this? Best to drop packet now. */ |
| if (nf_ct_expect_related(exp, 0) != 0) { |
| nf_ct_helper_log(skb, ct, "cannot add expectation"); |
| ret = NF_DROP; |
| } |
| |
| nf_ct_expect_put(exp); |
| return ret; |
| } |
| |
| static struct nf_conntrack_helper sane[MAX_PORTS * 2] __read_mostly; |
| |
| static const struct nf_conntrack_expect_policy sane_exp_policy = { |
| .max_expected = 1, |
| .timeout = 5 * 60, |
| }; |
| |
| static void __exit nf_conntrack_sane_fini(void) |
| { |
| nf_conntrack_helpers_unregister(sane, ports_c * 2); |
| } |
| |
| static int __init nf_conntrack_sane_init(void) |
| { |
| int i, ret = 0; |
| |
| NF_CT_HELPER_BUILD_BUG_ON(sizeof(struct nf_ct_sane_master)); |
| |
| if (ports_c == 0) |
| ports[ports_c++] = SANE_PORT; |
| |
| /* FIXME should be configurable whether IPv4 and IPv6 connections |
| are tracked or not - YK */ |
| for (i = 0; i < ports_c; i++) { |
| nf_ct_helper_init(&sane[2 * i], AF_INET, IPPROTO_TCP, |
| HELPER_NAME, SANE_PORT, ports[i], ports[i], |
| &sane_exp_policy, 0, help, NULL, |
| THIS_MODULE); |
| nf_ct_helper_init(&sane[2 * i + 1], AF_INET6, IPPROTO_TCP, |
| HELPER_NAME, SANE_PORT, ports[i], ports[i], |
| &sane_exp_policy, 0, help, NULL, |
| THIS_MODULE); |
| } |
| |
| ret = nf_conntrack_helpers_register(sane, ports_c * 2); |
| if (ret < 0) { |
| pr_err("failed to register helpers\n"); |
| return ret; |
| } |
| |
| return 0; |
| } |
| |
| module_init(nf_conntrack_sane_init); |
| module_exit(nf_conntrack_sane_fini); |