1 /* SANE connection tracking helper 2 * (SANE = Scanner Access Now Easy) 3 * For documentation about the SANE network protocol see 4 * http://www.sane-project.org/html/doc015.html 5 */ 6 7 /* Copyright (C) 2007 Red Hat, Inc. 8 * Author: Michal Schmidt <mschmidt@redhat.com> 9 * Based on the FTP conntrack helper (net/netfilter/nf_conntrack_ftp.c): 10 * (C) 1999-2001 Paul `Rusty' Russell 11 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org> 12 * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org> 13 * (C) 2003 Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp> 14 * 15 * This program is free software; you can redistribute it and/or modify 16 * it under the terms of the GNU General Public License version 2 as 17 * published by the Free Software Foundation. 18 */ 19 20 #include <linux/module.h> 21 #include <linux/moduleparam.h> 22 #include <linux/netfilter.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 MODULE_LICENSE("GPL"); 31 MODULE_AUTHOR("Michal Schmidt <mschmidt@redhat.com>"); 32 MODULE_DESCRIPTION("SANE connection tracking helper"); 33 MODULE_ALIAS_NFCT_HELPER("sane"); 34 35 static char *sane_buffer; 36 37 static DEFINE_SPINLOCK(nf_sane_lock); 38 39 #define MAX_PORTS 8 40 static u_int16_t ports[MAX_PORTS]; 41 static unsigned int ports_c; 42 module_param_array(ports, ushort, &ports_c, 0400); 43 44 struct sane_request { 45 __be32 RPC_code; 46 #define SANE_NET_START 7 /* RPC code */ 47 48 __be32 handle; 49 }; 50 51 struct sane_reply_net_start { 52 __be32 status; 53 #define SANE_STATUS_SUCCESS 0 54 55 __be16 zero; 56 __be16 port; 57 /* other fields aren't interesting for conntrack */ 58 }; 59 60 static int help(struct sk_buff *skb, 61 unsigned int protoff, 62 struct nf_conn *ct, 63 enum ip_conntrack_info ctinfo) 64 { 65 unsigned int dataoff, datalen; 66 const struct tcphdr *th; 67 struct tcphdr _tcph; 68 void *sb_ptr; 69 int ret = NF_ACCEPT; 70 int dir = CTINFO2DIR(ctinfo); 71 struct nf_ct_sane_master *ct_sane_info; 72 struct nf_conntrack_expect *exp; 73 struct nf_conntrack_tuple *tuple; 74 struct sane_request *req; 75 struct sane_reply_net_start *reply; 76 77 ct_sane_info = &nfct_help(ct)->help.ct_sane_info; 78 /* Until there's been traffic both ways, don't look in packets. */ 79 if (ctinfo != IP_CT_ESTABLISHED && 80 ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) 81 return NF_ACCEPT; 82 83 /* Not a full tcp header? */ 84 th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph); 85 if (th == NULL) 86 return NF_ACCEPT; 87 88 /* No data? */ 89 dataoff = protoff + th->doff * 4; 90 if (dataoff >= skb->len) 91 return NF_ACCEPT; 92 93 datalen = skb->len - dataoff; 94 95 spin_lock_bh(&nf_sane_lock); 96 sb_ptr = skb_header_pointer(skb, dataoff, datalen, sane_buffer); 97 BUG_ON(sb_ptr == NULL); 98 99 if (dir == IP_CT_DIR_ORIGINAL) { 100 if (datalen != sizeof(struct sane_request)) 101 goto out; 102 103 req = sb_ptr; 104 if (req->RPC_code != htonl(SANE_NET_START)) { 105 /* Not an interesting command */ 106 ct_sane_info->state = SANE_STATE_NORMAL; 107 goto out; 108 } 109 110 /* We're interested in the next reply */ 111 ct_sane_info->state = SANE_STATE_START_REQUESTED; 112 goto out; 113 } 114 115 /* Is it a reply to an uninteresting command? */ 116 if (ct_sane_info->state != SANE_STATE_START_REQUESTED) 117 goto out; 118 119 /* It's a reply to SANE_NET_START. */ 120 ct_sane_info->state = SANE_STATE_NORMAL; 121 122 if (datalen < sizeof(struct sane_reply_net_start)) { 123 pr_debug("nf_ct_sane: NET_START reply too short\n"); 124 goto out; 125 } 126 127 reply = sb_ptr; 128 if (reply->status != htonl(SANE_STATUS_SUCCESS)) { 129 /* saned refused the command */ 130 pr_debug("nf_ct_sane: unsuccessful SANE_STATUS = %u\n", 131 ntohl(reply->status)); 132 goto out; 133 } 134 135 /* Invalid saned reply? Ignore it. */ 136 if (reply->zero != 0) 137 goto out; 138 139 exp = nf_ct_expect_alloc(ct); 140 if (exp == NULL) { 141 ret = NF_DROP; 142 goto out; 143 } 144 145 tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple; 146 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, nf_ct_l3num(ct), 147 &tuple->src.u3, &tuple->dst.u3, 148 IPPROTO_TCP, NULL, &reply->port); 149 150 pr_debug("nf_ct_sane: expect: "); 151 nf_ct_dump_tuple(&exp->tuple); 152 153 /* Can't expect this? Best to drop packet now. */ 154 if (nf_ct_expect_related(exp) != 0) 155 ret = NF_DROP; 156 157 nf_ct_expect_put(exp); 158 159 out: 160 spin_unlock_bh(&nf_sane_lock); 161 return ret; 162 } 163 164 static struct nf_conntrack_helper sane[MAX_PORTS][2] __read_mostly; 165 static char sane_names[MAX_PORTS][2][sizeof("sane-65535")] __read_mostly; 166 167 static const struct nf_conntrack_expect_policy sane_exp_policy = { 168 .max_expected = 1, 169 .timeout = 5 * 60, 170 }; 171 172 /* don't make this __exit, since it's called from __init ! */ 173 static void nf_conntrack_sane_fini(void) 174 { 175 int i, j; 176 177 for (i = 0; i < ports_c; i++) { 178 for (j = 0; j < 2; j++) { 179 pr_debug("nf_ct_sane: unregistering helper for pf: %d " 180 "port: %d\n", 181 sane[i][j].tuple.src.l3num, ports[i]); 182 nf_conntrack_helper_unregister(&sane[i][j]); 183 } 184 } 185 186 kfree(sane_buffer); 187 } 188 189 static int __init nf_conntrack_sane_init(void) 190 { 191 int i, j = -1, ret = 0; 192 char *tmpname; 193 194 sane_buffer = kmalloc(65536, GFP_KERNEL); 195 if (!sane_buffer) 196 return -ENOMEM; 197 198 if (ports_c == 0) 199 ports[ports_c++] = SANE_PORT; 200 201 /* FIXME should be configurable whether IPv4 and IPv6 connections 202 are tracked or not - YK */ 203 for (i = 0; i < ports_c; i++) { 204 sane[i][0].tuple.src.l3num = PF_INET; 205 sane[i][1].tuple.src.l3num = PF_INET6; 206 for (j = 0; j < 2; j++) { 207 sane[i][j].tuple.src.u.tcp.port = htons(ports[i]); 208 sane[i][j].tuple.dst.protonum = IPPROTO_TCP; 209 sane[i][j].expect_policy = &sane_exp_policy; 210 sane[i][j].me = THIS_MODULE; 211 sane[i][j].help = help; 212 tmpname = &sane_names[i][j][0]; 213 if (ports[i] == SANE_PORT) 214 sprintf(tmpname, "sane"); 215 else 216 sprintf(tmpname, "sane-%d", ports[i]); 217 sane[i][j].name = tmpname; 218 219 pr_debug("nf_ct_sane: registering helper for pf: %d " 220 "port: %d\n", 221 sane[i][j].tuple.src.l3num, ports[i]); 222 ret = nf_conntrack_helper_register(&sane[i][j]); 223 if (ret) { 224 printk(KERN_ERR "nf_ct_sane: failed to " 225 "register helper for pf: %d port: %d\n", 226 sane[i][j].tuple.src.l3num, ports[i]); 227 nf_conntrack_sane_fini(); 228 return ret; 229 } 230 } 231 } 232 233 return 0; 234 } 235 236 module_init(nf_conntrack_sane_init); 237 module_exit(nf_conntrack_sane_fini); 238