diff options
Diffstat (limited to 'net/netfilter/nf_conntrack_sane.c')
| -rw-r--r-- | net/netfilter/nf_conntrack_sane.c | 213 |
1 files changed, 213 insertions, 0 deletions
diff --git a/net/netfilter/nf_conntrack_sane.c b/net/netfilter/nf_conntrack_sane.c new file mode 100644 index 000000000..13dc421fc --- /dev/null +++ b/net/netfilter/nf_conntrack_sane.c @@ -0,0 +1,213 @@ +// 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); |