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-rw-r--r--net/netfilter/nf_conntrack_ftp.c604
1 files changed, 604 insertions, 0 deletions
diff --git a/net/netfilter/nf_conntrack_ftp.c b/net/netfilter/nf_conntrack_ftp.c
new file mode 100644
index 000000000..617f744a2
--- /dev/null
+++ b/net/netfilter/nf_conntrack_ftp.c
@@ -0,0 +1,604 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* FTP extension for connection tracking. */
+
+/* (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) 2006-2012 Patrick McHardy <kaber@trash.net>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/netfilter.h>
+#include <linux/ip.h>
+#include <linux/slab.h>
+#include <linux/ipv6.h>
+#include <linux/ctype.h>
+#include <linux/inet.h>
+#include <net/checksum.h>
+#include <net/tcp.h>
+
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_expect.h>
+#include <net/netfilter/nf_conntrack_ecache.h>
+#include <net/netfilter/nf_conntrack_helper.h>
+#include <linux/netfilter/nf_conntrack_ftp.h>
+
+#define HELPER_NAME "ftp"
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
+MODULE_DESCRIPTION("ftp connection tracking helper");
+MODULE_ALIAS("ip_conntrack_ftp");
+MODULE_ALIAS_NFCT_HELPER(HELPER_NAME);
+static DEFINE_SPINLOCK(nf_ftp_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);
+
+static bool loose;
+module_param(loose, bool, 0600);
+
+unsigned int (*nf_nat_ftp_hook)(struct sk_buff *skb,
+ enum ip_conntrack_info ctinfo,
+ enum nf_ct_ftp_type type,
+ unsigned int protoff,
+ unsigned int matchoff,
+ unsigned int matchlen,
+ struct nf_conntrack_expect *exp);
+EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
+
+static int try_rfc959(const char *, size_t, struct nf_conntrack_man *,
+ char, unsigned int *);
+static int try_rfc1123(const char *, size_t, struct nf_conntrack_man *,
+ char, unsigned int *);
+static int try_eprt(const char *, size_t, struct nf_conntrack_man *,
+ char, unsigned int *);
+static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
+ char, unsigned int *);
+
+static struct ftp_search {
+ const char *pattern;
+ size_t plen;
+ char skip;
+ char term;
+ enum nf_ct_ftp_type ftptype;
+ int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char, unsigned int *);
+} search[IP_CT_DIR_MAX][2] = {
+ [IP_CT_DIR_ORIGINAL] = {
+ {
+ .pattern = "PORT",
+ .plen = sizeof("PORT") - 1,
+ .skip = ' ',
+ .term = '\r',
+ .ftptype = NF_CT_FTP_PORT,
+ .getnum = try_rfc959,
+ },
+ {
+ .pattern = "EPRT",
+ .plen = sizeof("EPRT") - 1,
+ .skip = ' ',
+ .term = '\r',
+ .ftptype = NF_CT_FTP_EPRT,
+ .getnum = try_eprt,
+ },
+ },
+ [IP_CT_DIR_REPLY] = {
+ {
+ .pattern = "227 ",
+ .plen = sizeof("227 ") - 1,
+ .ftptype = NF_CT_FTP_PASV,
+ .getnum = try_rfc1123,
+ },
+ {
+ .pattern = "229 ",
+ .plen = sizeof("229 ") - 1,
+ .skip = '(',
+ .term = ')',
+ .ftptype = NF_CT_FTP_EPSV,
+ .getnum = try_epsv_response,
+ },
+ },
+};
+
+static int
+get_ipv6_addr(const char *src, size_t dlen, struct in6_addr *dst, u_int8_t term)
+{
+ const char *end;
+ int ret = in6_pton(src, min_t(size_t, dlen, 0xffff), (u8 *)dst, term, &end);
+ if (ret > 0)
+ return (int)(end - src);
+ return 0;
+}
+
+static int try_number(const char *data, size_t dlen, u_int32_t array[],
+ int array_size, char sep, char term)
+{
+ u_int32_t i, len;
+
+ memset(array, 0, sizeof(array[0])*array_size);
+
+ /* Keep data pointing at next char. */
+ for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
+ if (*data >= '0' && *data <= '9') {
+ array[i] = array[i]*10 + *data - '0';
+ }
+ else if (*data == sep)
+ i++;
+ else {
+ /* Unexpected character; true if it's the
+ terminator (or we don't care about one)
+ and we're finished. */
+ if ((*data == term || !term) && i == array_size - 1)
+ return len;
+
+ pr_debug("Char %u (got %u nums) `%u' unexpected\n",
+ len, i, *data);
+ return 0;
+ }
+ }
+ pr_debug("Failed to fill %u numbers separated by %c\n",
+ array_size, sep);
+ return 0;
+}
+
+/* Returns 0, or length of numbers: 192,168,1,1,5,6 */
+static int try_rfc959(const char *data, size_t dlen,
+ struct nf_conntrack_man *cmd, char term,
+ unsigned int *offset)
+{
+ int length;
+ u_int32_t array[6];
+
+ length = try_number(data, dlen, array, 6, ',', term);
+ if (length == 0)
+ return 0;
+
+ cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16) |
+ (array[2] << 8) | array[3]);
+ cmd->u.tcp.port = htons((array[4] << 8) | array[5]);
+ return length;
+}
+
+/*
+ * From RFC 1123:
+ * The format of the 227 reply to a PASV command is not
+ * well standardized. In particular, an FTP client cannot
+ * assume that the parentheses shown on page 40 of RFC-959
+ * will be present (and in fact, Figure 3 on page 43 omits
+ * them). Therefore, a User-FTP program that interprets
+ * the PASV reply must scan the reply for the first digit
+ * of the host and port numbers.
+ */
+static int try_rfc1123(const char *data, size_t dlen,
+ struct nf_conntrack_man *cmd, char term,
+ unsigned int *offset)
+{
+ int i;
+ for (i = 0; i < dlen; i++)
+ if (isdigit(data[i]))
+ break;
+
+ if (i == dlen)
+ return 0;
+
+ *offset += i;
+
+ return try_rfc959(data + i, dlen - i, cmd, 0, offset);
+}
+
+/* Grab port: number up to delimiter */
+static int get_port(const char *data, int start, size_t dlen, char delim,
+ __be16 *port)
+{
+ u_int16_t tmp_port = 0;
+ int i;
+
+ for (i = start; i < dlen; i++) {
+ /* Finished? */
+ if (data[i] == delim) {
+ if (tmp_port == 0)
+ break;
+ *port = htons(tmp_port);
+ pr_debug("get_port: return %d\n", tmp_port);
+ return i + 1;
+ }
+ else if (data[i] >= '0' && data[i] <= '9')
+ tmp_port = tmp_port*10 + data[i] - '0';
+ else { /* Some other crap */
+ pr_debug("get_port: invalid char.\n");
+ break;
+ }
+ }
+ return 0;
+}
+
+/* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
+static int try_eprt(const char *data, size_t dlen, struct nf_conntrack_man *cmd,
+ char term, unsigned int *offset)
+{
+ char delim;
+ int length;
+
+ /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
+ then delimiter again. */
+ if (dlen <= 3) {
+ pr_debug("EPRT: too short\n");
+ return 0;
+ }
+ delim = data[0];
+ if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
+ pr_debug("try_eprt: invalid delimiter.\n");
+ return 0;
+ }
+
+ if ((cmd->l3num == PF_INET && data[1] != '1') ||
+ (cmd->l3num == PF_INET6 && data[1] != '2')) {
+ pr_debug("EPRT: invalid protocol number.\n");
+ return 0;
+ }
+
+ pr_debug("EPRT: Got %c%c%c\n", delim, data[1], delim);
+
+ if (data[1] == '1') {
+ u_int32_t array[4];
+
+ /* Now we have IP address. */
+ length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
+ if (length != 0)
+ cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16)
+ | (array[2] << 8) | array[3]);
+ } else {
+ /* Now we have IPv6 address. */
+ length = get_ipv6_addr(data + 3, dlen - 3,
+ (struct in6_addr *)cmd->u3.ip6, delim);
+ }
+
+ if (length == 0)
+ return 0;
+ pr_debug("EPRT: Got IP address!\n");
+ /* Start offset includes initial "|1|", and trailing delimiter */
+ return get_port(data, 3 + length + 1, dlen, delim, &cmd->u.tcp.port);
+}
+
+/* Returns 0, or length of numbers: |||6446| */
+static int try_epsv_response(const char *data, size_t dlen,
+ struct nf_conntrack_man *cmd, char term,
+ unsigned int *offset)
+{
+ char delim;
+
+ /* Three delimiters. */
+ if (dlen <= 3) return 0;
+ delim = data[0];
+ if (isdigit(delim) || delim < 33 || delim > 126 ||
+ data[1] != delim || data[2] != delim)
+ return 0;
+
+ return get_port(data, 3, dlen, delim, &cmd->u.tcp.port);
+}
+
+/* Return 1 for match, 0 for accept, -1 for partial. */
+static int find_pattern(const char *data, size_t dlen,
+ const char *pattern, size_t plen,
+ char skip, char term,
+ unsigned int *numoff,
+ unsigned int *numlen,
+ struct nf_conntrack_man *cmd,
+ int (*getnum)(const char *, size_t,
+ struct nf_conntrack_man *, char,
+ unsigned int *))
+{
+ size_t i = plen;
+
+ pr_debug("find_pattern `%s': dlen = %zu\n", pattern, dlen);
+
+ if (dlen <= plen) {
+ /* Short packet: try for partial? */
+ if (strncasecmp(data, pattern, dlen) == 0)
+ return -1;
+ else return 0;
+ }
+
+ if (strncasecmp(data, pattern, plen) != 0)
+ return 0;
+
+ pr_debug("Pattern matches!\n");
+ /* Now we've found the constant string, try to skip
+ to the 'skip' character */
+ if (skip) {
+ for (i = plen; data[i] != skip; i++)
+ if (i == dlen - 1) return -1;
+
+ /* Skip over the last character */
+ i++;
+ }
+
+ pr_debug("Skipped up to 0x%hhx delimiter!\n", skip);
+
+ *numoff = i;
+ *numlen = getnum(data + i, dlen - i, cmd, term, numoff);
+ 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(struct nf_conn *ct, u32 nl_seq,
+ struct nf_ct_ftp_master *info, int dir,
+ struct sk_buff *skb)
+{
+ unsigned int i, oldest;
+
+ /* 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 (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
+ info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
+ } else {
+ if (before(info->seq_aft_nl[dir][0], info->seq_aft_nl[dir][1]))
+ oldest = 0;
+ else
+ oldest = 1;
+
+ if (after(nl_seq, info->seq_aft_nl[dir][oldest]))
+ info->seq_aft_nl[dir][oldest] = nl_seq;
+ }
+}
+
+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;
+ const 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_data(ct);
+ struct nf_conntrack_expect *exp;
+ union nf_inet_addr *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_REPLY) {
+ pr_debug("ftp: Conntrackinfo = %u\n", ctinfo);
+ return NF_ACCEPT;
+ }
+
+ if (unlikely(skb_linearize(skb)))
+ return NF_DROP;
+
+ 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;
+
+ /* seqadj (nat) uses ct->lock internally, nf_nat_ftp would cause deadlock */
+ spin_lock_bh(&nf_ftp_lock);
+ fb_ptr = skb->data + dataoff;
+
+ 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)) {
+ /* We're picking up this, clear flags and let it continue */
+ if (unlikely(ct_ftp_info->flags[dir] & NF_CT_FTP_SEQ_PICKUP)) {
+ ct_ftp_info->flags[dir] ^= NF_CT_FTP_SEQ_PICKUP;
+ goto skip_nl_seq;
+ }
+
+ /* 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;
+ }
+
+skip_nl_seq:
+ /* Initialize IP/IPv6 addr to expected address (it's not mentioned
+ in EPSV responses) */
+ cmd.l3num = nf_ct_l3num(ct);
+ 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. */
+ nf_ct_helper_log(skb, ct, "partial matching of `%s'",
+ search[dir][i].pattern);
+ 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) {
+ nf_ct_helper_log(skb, ct, "cannot alloc expectation");
+ 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 == nf_ct_l3num(ct)) &&
+ 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("NOT RECORDING: %pI4 != %pI4\n",
+ &cmd.u3.ip,
+ &ct->tuplehash[dir].tuple.src.u3.ip);
+ } else {
+ pr_debug("NOT RECORDING: %pI6 != %pI6\n",
+ cmd.u3.ip6,
+ ct->tuplehash[dir].tuple.src.u3.ip6);
+ }
+
+ /* Thanks to Cristiano Lincoln Mattos
+ <lincoln@cesar.org.br> 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, NF_CT_EXPECT_CLASS_DEFAULT, 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,
+ protoff, matchoff, matchlen, exp);
+ else {
+ /* 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;
+ } 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(ct, seq, ct_ftp_info, dir, skb);
+ out:
+ spin_unlock_bh(&nf_ftp_lock);
+ return ret;
+}
+
+static int nf_ct_ftp_from_nlattr(struct nlattr *attr, struct nf_conn *ct)
+{
+ struct nf_ct_ftp_master *ftp = nfct_help_data(ct);
+
+ /* This conntrack has been injected from user-space, always pick up
+ * sequence tracking. Otherwise, the first FTP command after the
+ * failover breaks.
+ */
+ ftp->flags[IP_CT_DIR_ORIGINAL] |= NF_CT_FTP_SEQ_PICKUP;
+ ftp->flags[IP_CT_DIR_REPLY] |= NF_CT_FTP_SEQ_PICKUP;
+ return 0;
+}
+
+static struct nf_conntrack_helper ftp[MAX_PORTS * 2] __read_mostly;
+
+static const struct nf_conntrack_expect_policy ftp_exp_policy = {
+ .max_expected = 1,
+ .timeout = 5 * 60,
+};
+
+static void __exit nf_conntrack_ftp_fini(void)
+{
+ nf_conntrack_helpers_unregister(ftp, ports_c * 2);
+}
+
+static int __init nf_conntrack_ftp_init(void)
+{
+ int i, ret = 0;
+
+ NF_CT_HELPER_BUILD_BUG_ON(sizeof(struct nf_ct_ftp_master));
+
+ 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++) {
+ nf_ct_helper_init(&ftp[2 * i], AF_INET, IPPROTO_TCP,
+ HELPER_NAME, FTP_PORT, ports[i], ports[i],
+ &ftp_exp_policy, 0, help,
+ nf_ct_ftp_from_nlattr, THIS_MODULE);
+ nf_ct_helper_init(&ftp[2 * i + 1], AF_INET6, IPPROTO_TCP,
+ HELPER_NAME, FTP_PORT, ports[i], ports[i],
+ &ftp_exp_policy, 0, help,
+ nf_ct_ftp_from_nlattr, THIS_MODULE);
+ }
+
+ ret = nf_conntrack_helpers_register(ftp, ports_c * 2);
+ if (ret < 0) {
+ pr_err("failed to register helpers\n");
+ return ret;
+ }
+
+ return 0;
+}
+
+module_init(nf_conntrack_ftp_init);
+module_exit(nf_conntrack_ftp_fini);
generated by cgit v1.2.3 (git 2.39.1) at 2024-05-25 02:25:28 +0000