nf_conntrack_ftp.c

来自「linux 内核源代码」· C语言 代码 · 共 589 行 · 第 1/2 页

	i++;

	pr_debug("Skipped up to `%c'!\n", skip);

	*numoff = i;
	*numlen = getnum(data + i, dlen - i, cmd, term);
	if (!*numlen)
		return -1;

	pr_debug("Match succeeded!\n");
	return 1;
}

/* Look up to see if we're just after a \n. */
static int find_nl_seq(u32 seq, const struct nf_ct_ftp_master *info, int dir)
{
	unsigned int i;

	for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
		if (info->seq_aft_nl[dir][i] == seq)
			return 1;
	return 0;
}

/* We don't update if it's older than what we have. */
static void update_nl_seq(u32 nl_seq, struct nf_ct_ftp_master *info, int dir,
			  struct sk_buff *skb)
{
	unsigned int i, oldest = NUM_SEQ_TO_REMEMBER;

	/* Look for oldest: if we find exact match, we're done. */
	for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
		if (info->seq_aft_nl[dir][i] == nl_seq)
			return;

		if (oldest == info->seq_aft_nl_num[dir] ||
		    before(info->seq_aft_nl[dir][i],
			   info->seq_aft_nl[dir][oldest]))
			oldest = i;
	}

	if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
		info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
		nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
	} else if (oldest != NUM_SEQ_TO_REMEMBER &&
		   after(nl_seq, info->seq_aft_nl[dir][oldest])) {
		info->seq_aft_nl[dir][oldest] = nl_seq;
		nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
	}
}

static int help(struct sk_buff *skb,
		unsigned int protoff,
		struct nf_conn *ct,
		enum ip_conntrack_info ctinfo)
{
	unsigned int dataoff, datalen;
	struct tcphdr _tcph, *th;
	char *fb_ptr;
	int ret;
	u32 seq;
	int dir = CTINFO2DIR(ctinfo);
	unsigned int matchlen, matchoff;
	struct nf_ct_ftp_master *ct_ftp_info = &nfct_help(ct)->help.ct_ftp_info;
	struct nf_conntrack_expect *exp;
	union nf_conntrack_address *daddr;
	struct nf_conntrack_man cmd = {};
	unsigned int i;
	int found = 0, ends_in_nl;
	typeof(nf_nat_ftp_hook) nf_nat_ftp;

	/* Until there's been traffic both ways, don't look in packets. */
	if (ctinfo != IP_CT_ESTABLISHED
	    && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
		pr_debug("ftp: Conntrackinfo = %u\n", ctinfo);
		return NF_ACCEPT;
	}

	th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
	if (th == NULL)
		return NF_ACCEPT;

	dataoff = protoff + th->doff * 4;
	/* No data? */
	if (dataoff >= skb->len) {
		pr_debug("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
			 skb->len);
		return NF_ACCEPT;
	}
	datalen = skb->len - dataoff;

	spin_lock_bh(&nf_ftp_lock);
	fb_ptr = skb_header_pointer(skb, dataoff, datalen, ftp_buffer);
	BUG_ON(fb_ptr == NULL);

	ends_in_nl = (fb_ptr[datalen - 1] == '\n');
	seq = ntohl(th->seq) + datalen;

	/* Look up to see if we're just after a \n. */
	if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
		/* Now if this ends in \n, update ftp info. */
		pr_debug("nf_conntrack_ftp: wrong seq pos %s(%u) or %s(%u)\n",
			 ct_ftp_info->seq_aft_nl_num[dir] > 0 ? "" : "(UNSET)",
			 ct_ftp_info->seq_aft_nl[dir][0],
			 ct_ftp_info->seq_aft_nl_num[dir] > 1 ? "" : "(UNSET)",
			 ct_ftp_info->seq_aft_nl[dir][1]);
		ret = NF_ACCEPT;
		goto out_update_nl;
	}

	/* Initialize IP/IPv6 addr to expected address (it's not mentioned
	   in EPSV responses) */
	cmd.l3num = ct->tuplehash[dir].tuple.src.l3num;
	memcpy(cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
	       sizeof(cmd.u3.all));

	for (i = 0; i < ARRAY_SIZE(search[dir]); i++) {
		found = find_pattern(fb_ptr, datalen,
				     search[dir][i].pattern,
				     search[dir][i].plen,
				     search[dir][i].skip,
				     search[dir][i].term,
				     &matchoff, &matchlen,
				     &cmd,
				     search[dir][i].getnum);
		if (found) break;
	}
	if (found == -1) {
		/* We don't usually drop packets.  After all, this is
		   connection tracking, not packet filtering.
		   However, it is necessary for accurate tracking in
		   this case. */
		if (net_ratelimit())
			printk("conntrack_ftp: partial %s %u+%u\n",
			       search[dir][i].pattern,
			       ntohl(th->seq), datalen);
		ret = NF_DROP;
		goto out;
	} else if (found == 0) { /* No match */
		ret = NF_ACCEPT;
		goto out_update_nl;
	}

	pr_debug("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
		 matchlen, fb_ptr + matchoff,
		 matchlen, ntohl(th->seq) + matchoff);

	exp = nf_ct_expect_alloc(ct);
	if (exp == NULL) {
		ret = NF_DROP;
		goto out;
	}

	/* We refer to the reverse direction ("!dir") tuples here,
	 * because we're expecting something in the other direction.
	 * Doesn't matter unless NAT is happening.  */
	daddr = &ct->tuplehash[!dir].tuple.dst.u3;

	/* Update the ftp info */
	if ((cmd.l3num == ct->tuplehash[dir].tuple.src.l3num) &&
	    memcmp(&cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
		     sizeof(cmd.u3.all))) {
		/* Enrico Scholz's passive FTP to partially RNAT'd ftp
		   server: it really wants us to connect to a
		   different IP address.  Simply don't record it for
		   NAT. */
		if (cmd.l3num == PF_INET) {
			pr_debug("conntrack_ftp: NOT RECORDING: " NIPQUAD_FMT
				 " != " NIPQUAD_FMT "\n",
				 NIPQUAD(cmd.u3.ip),
				 NIPQUAD(ct->tuplehash[dir].tuple.src.u3.ip));
		} else {
			pr_debug("conntrack_ftp: NOT RECORDING: " NIP6_FMT
				 " != " NIP6_FMT "\n",
				 NIP6(*((struct in6_addr *)cmd.u3.ip6)),
				 NIP6(*((struct in6_addr *)
					ct->tuplehash[dir].tuple.src.u3.ip6)));
		}

		/* Thanks to Cristiano Lincoln Mattos
		   <[e-mail]> for reporting this potential
		   problem (DMZ machines opening holes to internal
		   networks, or the packet filter itself). */
		if (!loose) {
			ret = NF_ACCEPT;
			goto out_put_expect;
		}
		daddr = &cmd.u3;
	}

	nf_ct_expect_init(exp, cmd.l3num,
			  &ct->tuplehash[!dir].tuple.src.u3, daddr,
			  IPPROTO_TCP, NULL, &cmd.u.tcp.port);

	/* Now, NAT might want to mangle the packet, and register the
	 * (possibly changed) expectation itself. */
	nf_nat_ftp = rcu_dereference(nf_nat_ftp_hook);
	if (nf_nat_ftp && ct->status & IPS_NAT_MASK)
		ret = nf_nat_ftp(skb, ctinfo, search[dir][i].ftptype,
				 matchoff, matchlen, exp);
	else {
		/* Can't expect this?  Best to drop packet now. */
		if (nf_ct_expect_related(exp) != 0)
			ret = NF_DROP;
		else
			ret = NF_ACCEPT;
	}

out_put_expect:
	nf_ct_expect_put(exp);

out_update_nl:
	/* Now if this ends in \n, update ftp info.  Seq may have been
	 * adjusted by NAT code. */
	if (ends_in_nl)
		update_nl_seq(seq, ct_ftp_info, dir, skb);
 out:
	spin_unlock_bh(&nf_ftp_lock);
	return ret;
}

static struct nf_conntrack_helper ftp[MAX_PORTS][2] __read_mostly;
static char ftp_names[MAX_PORTS][2][sizeof("ftp-65535")] __read_mostly;

/* don't make this __exit, since it's called from __init ! */
static void nf_conntrack_ftp_fini(void)
{
	int i, j;
	for (i = 0; i < ports_c; i++) {
		for (j = 0; j < 2; j++) {
			if (ftp[i][j].me == NULL)
				continue;

			pr_debug("nf_ct_ftp: unregistering helper for pf: %d "
				 "port: %d\n",
				 ftp[i][j].tuple.src.l3num, ports[i]);
			nf_conntrack_helper_unregister(&ftp[i][j]);
		}
	}

	kfree(ftp_buffer);
}

static int __init nf_conntrack_ftp_init(void)
{
	int i, j = -1, ret = 0;
	char *tmpname;

	ftp_buffer = kmalloc(65536, GFP_KERNEL);
	if (!ftp_buffer)
		return -ENOMEM;

	if (ports_c == 0)
		ports[ports_c++] = FTP_PORT;

	/* FIXME should be configurable whether IPv4 and IPv6 FTP connections
		 are tracked or not - YK */
	for (i = 0; i < ports_c; i++) {
		ftp[i][0].tuple.src.l3num = PF_INET;
		ftp[i][1].tuple.src.l3num = PF_INET6;
		for (j = 0; j < 2; j++) {
			ftp[i][j].tuple.src.u.tcp.port = htons(ports[i]);
			ftp[i][j].tuple.dst.protonum = IPPROTO_TCP;
			ftp[i][j].max_expected = 1;
			ftp[i][j].timeout = 5 * 60;	/* 5 Minutes */
			ftp[i][j].me = THIS_MODULE;
			ftp[i][j].help = help;
			tmpname = &ftp_names[i][j][0];
			if (ports[i] == FTP_PORT)
				sprintf(tmpname, "ftp");
			else
				sprintf(tmpname, "ftp-%d", ports[i]);
			ftp[i][j].name = tmpname;

			pr_debug("nf_ct_ftp: registering helper for pf: %d "
				 "port: %d\n",
				 ftp[i][j].tuple.src.l3num, ports[i]);
			ret = nf_conntrack_helper_register(&ftp[i][j]);
			if (ret) {
				printk("nf_ct_ftp: failed to register helper "
				       " for pf: %d port: %d\n",
					ftp[i][j].tuple.src.l3num, ports[i]);
				nf_conntrack_ftp_fini();
				return ret;
			}
		}
	}

	return 0;
}

module_init(nf_conntrack_ftp_init);
module_exit(nf_conntrack_ftp_fini);