/* 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 * Based on the FTP conntrack helper (net/netfilter/nf_conntrack_ftp.c): * (C) 1999-2001 Paul `Rusty' Russell * (C) 2002-2004 Netfilter Core Team * (C) 2003,2004 USAGI/WIDE Project * (C) 2003 Yasuyuki Kozakai @USAGI * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. */ #include #include #include #include #include #include #include #include #include #include MODULE_LICENSE("GPL"); MODULE_AUTHOR("Michal Schmidt "); MODULE_DESCRIPTION("SANE connection tracking helper"); MODULE_ALIAS_NFCT_HELPER("sane"); static char *sane_buffer; static DEFINE_SPINLOCK(nf_sane_lock); #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; void *sb_ptr; 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_request *req; struct sane_reply_net_start *reply; /* 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; spin_lock_bh(&nf_sane_lock); sb_ptr = skb_header_pointer(skb, dataoff, datalen, sane_buffer); BUG_ON(sb_ptr == NULL); if (dir == IP_CT_DIR_ORIGINAL) { if (datalen != sizeof(struct sane_request)) goto out; req = sb_ptr; if (req->RPC_code != htonl(SANE_NET_START)) { /* Not an interesting command */ ct_sane_info->state = SANE_STATE_NORMAL; goto out; } /* We're interested in the next reply */ ct_sane_info->state = SANE_STATE_START_REQUESTED; goto out; } /* Is it a reply to an uninteresting command? */ if (ct_sane_info->state != SANE_STATE_START_REQUESTED) goto out; /* It's a reply to SANE_NET_START. */ ct_sane_info->state = SANE_STATE_NORMAL; if (datalen < sizeof(struct sane_reply_net_start)) { pr_debug("nf_ct_sane: NET_START reply too short\n"); goto out; } reply = sb_ptr; if (reply->status != htonl(SANE_STATUS_SUCCESS)) { /* saned refused the command */ pr_debug("nf_ct_sane: unsuccessful SANE_STATUS = %u\n", ntohl(reply->status)); goto out; } /* Invalid saned reply? Ignore it. */ if (reply->zero != 0) goto out; exp = nf_ct_expect_alloc(ct); if (exp == NULL) { nf_ct_helper_log(skb, ct, "cannot alloc expectation"); ret = NF_DROP; goto out; } 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("nf_ct_sane: expect: "); nf_ct_dump_tuple(&exp->tuple); /* Can't expect this? Best to drop packet now. */ if (nf_ct_expect_related(exp) != 0) { nf_ct_helper_log(skb, ct, "cannot add expectation"); ret = NF_DROP; } nf_ct_expect_put(exp); out: spin_unlock_bh(&nf_sane_lock); 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, }; /* don't make this __exit, since it's called from __init ! */ static void nf_conntrack_sane_fini(void) { int i, j; for (i = 0; i < ports_c; i++) { for (j = 0; j < 2; j++) { pr_debug("nf_ct_sane: unregistering helper for pf: %d " "port: %d\n", sane[i][j].tuple.src.l3num, ports[i]); nf_conntrack_helper_unregister(&sane[i][j]); } } kfree(sane_buffer); } static int __init nf_conntrack_sane_init(void) { int i, j = -1, ret = 0; sane_buffer = kmalloc(65536, GFP_KERNEL); if (!sane_buffer) return -ENOMEM; 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++) { sane[i][0].tuple.src.l3num = PF_INET; sane[i][1].tuple.src.l3num = PF_INET6; for (j = 0; j < 2; j++) { sane[i][j].data_len = sizeof(struct nf_ct_sane_master); sane[i][j].tuple.src.u.tcp.port = htons(ports[i]); sane[i][j].tuple.dst.protonum = IPPROTO_TCP; sane[i][j].expect_policy = &sane_exp_policy; sane[i][j].me = THIS_MODULE; sane[i][j].help = help; if (ports[i] == SANE_PORT) sprintf(sane[i][j].name, "sane"); else sprintf(sane[i][j].name, "sane-%d", ports[i]); pr_debug("nf_ct_sane: registering helper for pf: %d " "port: %d\n", sane[i][j].tuple.src.l3num, ports[i]); ret = nf_conntrack_helper_register(&sane[i][j]); if (ret) { printk(KERN_ERR "nf_ct_sane: failed to " "register helper for pf: %d port: %d\n", sane[i][j].tuple.src.l3num, ports[i]); nf_conntrack_sane_fini(); return ret; } } } return 0; } module_init(nf_conntrack_sane_init); module_exit(nf_conntrack_sane_fini);