| // 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); |