net/netfilter/nf_conntrack_amanda.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* Amanda extension for IP connection tracking
   3  *
   4  * (C) 2002 by Brian J. Murrell <netfilter@interlinx.bc.ca>
   5  * based on HW's ip_conntrack_irc.c as well as other modules
   6  * (C) 2006 Patrick McHardy <kaber@trash.net>
   7  */
   8 #include <linux/kernel.h>
   9 #include <linux/module.h>
  10 #include <linux/moduleparam.h>
  11 #include <linux/textsearch.h>
  12 #include <linux/skbuff.h>
  13 #include <linux/in.h>
  14 #include <linux/udp.h>
  15 #include <linux/netfilter.h>
  16 #include <linux/gfp.h>
  17
  18 #include <net/netfilter/nf_conntrack.h>
  19 #include <net/netfilter/nf_conntrack_expect.h>
  20 #include <net/netfilter/nf_conntrack_ecache.h>
  21 #include <net/netfilter/nf_conntrack_helper.h>
  22 #include <linux/netfilter/nf_conntrack_amanda.h>
  23
  24 static unsigned int master_timeout __read_mostly = 300;
  25 static char *ts_algo = "kmp";
  26
  27 #define HELPER_NAME "amanda"
  28
  29 MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>");
  30 MODULE_DESCRIPTION("Amanda connection tracking module");
  31 MODULE_LICENSE("GPL");
  32 MODULE_ALIAS("ip_conntrack_amanda");
  33 MODULE_ALIAS_NFCT_HELPER(HELPER_NAME);
  34
  35 module_param(master_timeout, uint, 0600);
  36 MODULE_PARM_DESC(master_timeout, "timeout for the master connection");
  37 module_param(ts_algo, charp, 0400);
  38 MODULE_PARM_DESC(ts_algo, "textsearch algorithm to use (default kmp)");
  39
  40 unsigned int (*nf_nat_amanda_hook)(struct sk_buff *skb,
  41                                    enum ip_conntrack_info ctinfo,
  42                                    unsigned int protoff,
  43                                    unsigned int matchoff,
  44                                    unsigned int matchlen,
  45                                    struct nf_conntrack_expect *exp)
  46                                    __read_mostly;
  47 EXPORT_SYMBOL_GPL(nf_nat_amanda_hook);
  48
  49 enum amanda_strings {
  50         SEARCH_CONNECT,
  51         SEARCH_NEWLINE,
  52         SEARCH_DATA,
  53         SEARCH_MESG,
  54         SEARCH_INDEX,
  55         SEARCH_STATE,
  56 };
  57
  58 static struct {
  59         const char              *string;
  60         size_t                  len;
  61         struct ts_config        *ts;
  62 } search[] __read_mostly = {
  63         [SEARCH_CONNECT] = {
  64                 .string = "CONNECT ",
  65                 .len    = 8,
  66         },
  67         [SEARCH_NEWLINE] = {
  68                 .string = "\n",
  69                 .len    = 1,
  70         },
  71         [SEARCH_DATA] = {
  72                 .string = "DATA ",
  73                 .len    = 5,
  74         },
  75         [SEARCH_MESG] = {
  76                 .string = "MESG ",
  77                 .len    = 5,
  78         },
  79         [SEARCH_INDEX] = {
  80                 .string = "INDEX ",
  81                 .len    = 6,
  82         },
  83         [SEARCH_STATE] = {
  84                 .string = "STATE ",
  85                 .len    = 6,
  86         },
  87 };
  88
  89 static int amanda_help(struct sk_buff *skb,
  90                        unsigned int protoff,
  91                        struct nf_conn *ct,
  92                        enum ip_conntrack_info ctinfo)
  93 {
  94         struct nf_conntrack_expect *exp;
  95         struct nf_conntrack_tuple *tuple;
  96         unsigned int dataoff, start, stop, off, i;
  97         char pbuf[sizeof("65535")], *tmp;
  98         u_int16_t len;
  99         __be16 port;
 100         int ret = NF_ACCEPT;
 101         typeof(nf_nat_amanda_hook) nf_nat_amanda;
 102
 103         /* Only look at packets from the Amanda server */
 104         if (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL)
 105                 return NF_ACCEPT;
 106
 107         /* increase the UDP timeout of the master connection as replies from
 108          * Amanda clients to the server can be quite delayed */
 109         nf_ct_refresh(ct, master_timeout * HZ);
 110
 111         /* No data? */
 112         dataoff = protoff + sizeof(struct udphdr);
 113         if (dataoff >= skb->len) {
 114                 net_err_ratelimited("amanda_help: skblen = %u\n", skb->len);
 115                 return NF_ACCEPT;
 116         }
 117
 118         start = skb_find_text(skb, dataoff, skb->len,
 119                               search[SEARCH_CONNECT].ts);
 120         if (start == UINT_MAX)
 121                 goto out;
 122         start += dataoff + search[SEARCH_CONNECT].len;
 123
 124         stop = skb_find_text(skb, start, skb->len,
 125                              search[SEARCH_NEWLINE].ts);
 126         if (stop == UINT_MAX)
 127                 goto out;
 128         stop += start;
 129
 130         for (i = SEARCH_DATA; i <= SEARCH_STATE; i++) {
 131                 off = skb_find_text(skb, start, stop, search[i].ts);
 132                 if (off == UINT_MAX)
 133                         continue;
 134                 off += start + search[i].len;
 135
 136                 len = min_t(unsigned int, sizeof(pbuf) - 1, stop - off);
 137                 if (skb_copy_bits(skb, off, pbuf, len))
 138                         break;
 139                 pbuf[len] = '\0';
 140
 141                 port = htons(simple_strtoul(pbuf, &tmp, 10));
 142                 len = tmp - pbuf;
 143                 if (port == 0 || len > 5)
 144                         break;
 145
 146                 exp = nf_ct_expect_alloc(ct);
 147                 if (exp == NULL) {
 148                         nf_ct_helper_log(skb, ct, "cannot alloc expectation");
 149                         ret = NF_DROP;
 150                         goto out;
 151                 }
 152                 tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
 153                 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
 154                                   nf_ct_l3num(ct),
 155                                   &tuple->src.u3, &tuple->dst.u3,
 156                                   IPPROTO_TCP, NULL, &port);
 157
 158                 nf_nat_amanda = rcu_dereference(nf_nat_amanda_hook);
 159                 if (nf_nat_amanda && ct->status & IPS_NAT_MASK)
 160                         ret = nf_nat_amanda(skb, ctinfo, protoff,
 161                                             off - dataoff, len, exp);
 162                 else if (nf_ct_expect_related(exp, 0) != 0) {
 163                         nf_ct_helper_log(skb, ct, "cannot add expectation");
 164                         ret = NF_DROP;
 165                 }
 166                 nf_ct_expect_put(exp);
 167         }
 168
 169 out:
 170         return ret;
 171 }
 172
 173 static const struct nf_conntrack_expect_policy amanda_exp_policy = {
 174         .max_expected           = 4,
 175         .timeout                = 180,
 176 };
 177
 178 static struct nf_conntrack_helper amanda_helper[2] __read_mostly = {
 179         {
 180                 .name                   = HELPER_NAME,
 181                 .me                     = THIS_MODULE,
 182                 .help                   = amanda_help,
 183                 .tuple.src.l3num        = AF_INET,
 184                 .tuple.src.u.udp.port   = cpu_to_be16(10080),
 185                 .tuple.dst.protonum     = IPPROTO_UDP,
 186                 .expect_policy          = &amanda_exp_policy,
 187                 .nat_mod_name           = NF_NAT_HELPER_NAME(HELPER_NAME),
 188         },
 189         {
 190                 .name                   = "amanda",
 191                 .me                     = THIS_MODULE,
 192                 .help                   = amanda_help,
 193                 .tuple.src.l3num        = AF_INET6,
 194                 .tuple.src.u.udp.port   = cpu_to_be16(10080),
 195                 .tuple.dst.protonum     = IPPROTO_UDP,
 196                 .expect_policy          = &amanda_exp_policy,
 197                 .nat_mod_name           = NF_NAT_HELPER_NAME(HELPER_NAME),
 198         },
 199 };
 200
 201 static void __exit nf_conntrack_amanda_fini(void)
 202 {
 203         int i;
 204
 205         nf_conntrack_helpers_unregister(amanda_helper,
 206                                         ARRAY_SIZE(amanda_helper));
 207         for (i = 0; i < ARRAY_SIZE(search); i++)
 208                 textsearch_destroy(search[i].ts);
 209 }
 210
 211 static int __init nf_conntrack_amanda_init(void)
 212 {
 213         int ret, i;
 214
 215         NF_CT_HELPER_BUILD_BUG_ON(0);
 216
 217         for (i = 0; i < ARRAY_SIZE(search); i++) {
 218                 search[i].ts = textsearch_prepare(ts_algo, search[i].string,
 219                                                   search[i].len,
 220                                                   GFP_KERNEL, TS_AUTOLOAD);
 221                 if (IS_ERR(search[i].ts)) {
 222                         ret = PTR_ERR(search[i].ts);
 223                         goto err1;
 224                 }
 225         }
 226         ret = nf_conntrack_helpers_register(amanda_helper,
 227                                             ARRAY_SIZE(amanda_helper));
 228         if (ret < 0)
 229                 goto err1;
 230         return 0;
 231
 232 err1:
 233         while (--i >= 0)
 234                 textsearch_destroy(search[i].ts);
 235
 236         return ret;
 237 }
 238
 239 module_init(nf_conntrack_amanda_init);
 240 module_exit(nf_conntrack_amanda_fini);