1 // SPDX-License-Identifier: GPL-2.0-only 2 /* SANE connection tracking helper 3 * (SANE = Scanner Access Now Easy) 4 * For documentation about the SANE network protocol see 5 * http://www.sane-project.org/html/doc015.html 6 */ 7 8 /* Copyright (C) 2007 Red Hat, Inc. 9 * Author: Michal Schmidt <mschmidt@redhat.com> 10 * Based on the FTP conntrack helper (net/netfilter/nf_conntrack_ftp.c): 11 * (C) 1999-2001 Paul `Rusty' Russell 12 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org> 13 * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org> 14 * (C) 2003 Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp> 15 */ 16 17 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 18 19 #include <linux/module.h> 20 #include <linux/moduleparam.h> 21 #include <linux/netfilter.h> 22 #include <linux/slab.h> 23 #include <linux/in.h> 24 #include <linux/tcp.h> 25 #include <net/netfilter/nf_conntrack.h> 26 #include <net/netfilter/nf_conntrack_helper.h> 27 #include <net/netfilter/nf_conntrack_expect.h> 28 #include <linux/netfilter/nf_conntrack_sane.h> 29 30 #define HELPER_NAME "sane" 31 32 MODULE_LICENSE("GPL"); 33 MODULE_AUTHOR("Michal Schmidt <mschmidt@redhat.com>"); 34 MODULE_DESCRIPTION("SANE connection tracking helper"); 35 MODULE_ALIAS_NFCT_HELPER(HELPER_NAME); 36 37 static char *sane_buffer; 38 39 static DEFINE_SPINLOCK(nf_sane_lock); 40 41 #define MAX_PORTS 8 42 static u_int16_t ports[MAX_PORTS]; 43 static unsigned int ports_c; 44 module_param_array(ports, ushort, &ports_c, 0400); 45 46 struct sane_request { 47 __be32 RPC_code; 48 #define SANE_NET_START 7 /* RPC code */ 49 50 __be32 handle; 51 }; 52 53 struct sane_reply_net_start { 54 __be32 status; 55 #define SANE_STATUS_SUCCESS 0 56 57 __be16 zero; 58 __be16 port; 59 /* other fields aren't interesting for conntrack */ 60 }; 61 62 static int help(struct sk_buff *skb, 63 unsigned int protoff, 64 struct nf_conn *ct, 65 enum ip_conntrack_info ctinfo) 66 { 67 unsigned int dataoff, datalen; 68 const struct tcphdr *th; 69 struct tcphdr _tcph; 70 void *sb_ptr; 71 int ret = NF_ACCEPT; 72 int dir = CTINFO2DIR(ctinfo); 73 struct nf_ct_sane_master *ct_sane_info = nfct_help_data(ct); 74 struct nf_conntrack_expect *exp; 75 struct nf_conntrack_tuple *tuple; 76 struct sane_request *req; 77 struct sane_reply_net_start *reply; 78 79 /* Until there's been traffic both ways, don't look in packets. */ 80 if (ctinfo != IP_CT_ESTABLISHED && 81 ctinfo != IP_CT_ESTABLISHED_REPLY) 82 return NF_ACCEPT; 83 84 /* Not a full tcp header? */ 85 th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph); 86 if (th == NULL) 87 return NF_ACCEPT; 88 89 /* No data? */ 90 dataoff = protoff + th->doff * 4; 91 if (dataoff >= skb->len) 92 return NF_ACCEPT; 93 94 datalen = skb->len - dataoff; 95 96 spin_lock_bh(&nf_sane_lock); 97 sb_ptr = skb_header_pointer(skb, dataoff, datalen, sane_buffer); 98 BUG_ON(sb_ptr == NULL); 99 100 if (dir == IP_CT_DIR_ORIGINAL) { 101 if (datalen != sizeof(struct sane_request)) 102 goto out; 103 104 req = sb_ptr; 105 if (req->RPC_code != htonl(SANE_NET_START)) { 106 /* Not an interesting command */ 107 ct_sane_info->state = SANE_STATE_NORMAL; 108 goto out; 109 } 110 111 /* We're interested in the next reply */ 112 ct_sane_info->state = SANE_STATE_START_REQUESTED; 113 goto out; 114 } 115 116 /* Is it a reply to an uninteresting command? */ 117 if (ct_sane_info->state != SANE_STATE_START_REQUESTED) 118 goto out; 119 120 /* It's a reply to SANE_NET_START. */ 121 ct_sane_info->state = SANE_STATE_NORMAL; 122 123 if (datalen < sizeof(struct sane_reply_net_start)) { 124 pr_debug("NET_START reply too short\n"); 125 goto out; 126 } 127 128 reply = sb_ptr; 129 if (reply->status != htonl(SANE_STATUS_SUCCESS)) { 130 /* saned refused the command */ 131 pr_debug("unsuccessful SANE_STATUS = %u\n", 132 ntohl(reply->status)); 133 goto out; 134 } 135 136 /* Invalid saned reply? Ignore it. */ 137 if (reply->zero != 0) 138 goto out; 139 140 exp = nf_ct_expect_alloc(ct); 141 if (exp == NULL) { 142 nf_ct_helper_log(skb, ct, "cannot alloc expectation"); 143 ret = NF_DROP; 144 goto out; 145 } 146 147 tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple; 148 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, nf_ct_l3num(ct), 149 &tuple->src.u3, &tuple->dst.u3, 150 IPPROTO_TCP, NULL, &reply->port); 151 152 pr_debug("expect: "); 153 nf_ct_dump_tuple(&exp->tuple); 154 155 /* Can't expect this? Best to drop packet now. */ 156 if (nf_ct_expect_related(exp, 0) != 0) { 157 nf_ct_helper_log(skb, ct, "cannot add expectation"); 158 ret = NF_DROP; 159 } 160 161 nf_ct_expect_put(exp); 162 163 out: 164 spin_unlock_bh(&nf_sane_lock); 165 return ret; 166 } 167 168 static struct nf_conntrack_helper sane[MAX_PORTS * 2] __read_mostly; 169 170 static const struct nf_conntrack_expect_policy sane_exp_policy = { 171 .max_expected = 1, 172 .timeout = 5 * 60, 173 }; 174 175 static void __exit nf_conntrack_sane_fini(void) 176 { 177 nf_conntrack_helpers_unregister(sane, ports_c * 2); 178 kfree(sane_buffer); 179 } 180 181 static int __init nf_conntrack_sane_init(void) 182 { 183 int i, ret = 0; 184 185 NF_CT_HELPER_BUILD_BUG_ON(sizeof(struct nf_ct_sane_master)); 186 187 sane_buffer = kmalloc(65536, GFP_KERNEL); 188 if (!sane_buffer) 189 return -ENOMEM; 190 191 if (ports_c == 0) 192 ports[ports_c++] = SANE_PORT; 193 194 /* FIXME should be configurable whether IPv4 and IPv6 connections 195 are tracked or not - YK */ 196 for (i = 0; i < ports_c; i++) { 197 nf_ct_helper_init(&sane[2 * i], AF_INET, IPPROTO_TCP, 198 HELPER_NAME, SANE_PORT, ports[i], ports[i], 199 &sane_exp_policy, 0, help, NULL, 200 THIS_MODULE); 201 nf_ct_helper_init(&sane[2 * i + 1], AF_INET6, IPPROTO_TCP, 202 HELPER_NAME, SANE_PORT, ports[i], ports[i], 203 &sane_exp_policy, 0, help, NULL, 204 THIS_MODULE); 205 } 206 207 ret = nf_conntrack_helpers_register(sane, ports_c * 2); 208 if (ret < 0) { 209 pr_err("failed to register helpers\n"); 210 kfree(sane_buffer); 211 return ret; 212 } 213 214 return 0; 215 } 216 217 module_init(nf_conntrack_sane_init); 218 module_exit(nf_conntrack_sane_fini); 219