699 lines
18 KiB
C
699 lines
18 KiB
C
/* FTP extension for connection tracking. */
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/* (C) 1999-2001 Paul `Rusty' Russell
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* (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
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* (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* 16 Dec 2003: Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
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* - enable working with Layer 3 protocol independent connection tracking.
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* - track EPRT and EPSV commands with IPv6 address.
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*
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* Derived from net/ipv4/netfilter/ip_conntrack_ftp.c
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*/
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#include <linux/config.h>
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#include <linux/module.h>
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#include <linux/moduleparam.h>
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#include <linux/netfilter.h>
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#include <linux/ip.h>
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#include <linux/ipv6.h>
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#include <linux/ctype.h>
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#include <net/checksum.h>
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#include <net/tcp.h>
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#include <net/netfilter/nf_conntrack.h>
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#include <net/netfilter/nf_conntrack_helper.h>
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#include <linux/netfilter/nf_conntrack_ftp.h>
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
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MODULE_DESCRIPTION("ftp connection tracking helper");
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/* This is slow, but it's simple. --RR */
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static char *ftp_buffer;
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static DEFINE_SPINLOCK(nf_ftp_lock);
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#define MAX_PORTS 8
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static u_int16_t ports[MAX_PORTS];
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static unsigned int ports_c;
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module_param_array(ports, ushort, &ports_c, 0400);
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static int loose;
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module_param(loose, bool, 0600);
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unsigned int (*nf_nat_ftp_hook)(struct sk_buff **pskb,
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enum ip_conntrack_info ctinfo,
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enum ip_ct_ftp_type type,
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unsigned int matchoff,
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unsigned int matchlen,
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struct nf_conntrack_expect *exp,
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u32 *seq);
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EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
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#if 0
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#define DEBUGP printk
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#else
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#define DEBUGP(format, args...)
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#endif
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static int try_rfc959(const char *, size_t, struct nf_conntrack_man *, char);
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static int try_eprt(const char *, size_t, struct nf_conntrack_man *, char);
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static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
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char);
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static struct ftp_search {
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enum ip_conntrack_dir dir;
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const char *pattern;
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size_t plen;
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char skip;
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char term;
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enum ip_ct_ftp_type ftptype;
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int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char);
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} search[] = {
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{
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IP_CT_DIR_ORIGINAL,
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"PORT", sizeof("PORT") - 1, ' ', '\r',
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IP_CT_FTP_PORT,
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try_rfc959,
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},
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{
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IP_CT_DIR_REPLY,
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"227 ", sizeof("227 ") - 1, '(', ')',
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IP_CT_FTP_PASV,
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try_rfc959,
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},
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{
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IP_CT_DIR_ORIGINAL,
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"EPRT", sizeof("EPRT") - 1, ' ', '\r',
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IP_CT_FTP_EPRT,
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try_eprt,
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},
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{
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IP_CT_DIR_REPLY,
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"229 ", sizeof("229 ") - 1, '(', ')',
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IP_CT_FTP_EPSV,
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try_epsv_response,
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},
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};
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/* This code is based on inet_pton() in glibc-2.2.4 */
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static int
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get_ipv6_addr(const char *src, size_t dlen, struct in6_addr *dst, u_int8_t term)
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{
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static const char xdigits[] = "0123456789abcdef";
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u_int8_t tmp[16], *tp, *endp, *colonp;
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int ch, saw_xdigit;
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u_int32_t val;
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size_t clen = 0;
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tp = memset(tmp, '\0', sizeof(tmp));
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endp = tp + sizeof(tmp);
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colonp = NULL;
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/* Leading :: requires some special handling. */
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if (*src == ':'){
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if (*++src != ':') {
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DEBUGP("invalid \":\" at the head of addr\n");
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return 0;
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}
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clen++;
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}
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saw_xdigit = 0;
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val = 0;
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while ((clen < dlen) && (*src != term)) {
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const char *pch;
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ch = tolower(*src++);
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clen++;
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pch = strchr(xdigits, ch);
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if (pch != NULL) {
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val <<= 4;
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val |= (pch - xdigits);
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if (val > 0xffff)
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return 0;
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saw_xdigit = 1;
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continue;
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}
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if (ch != ':') {
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DEBUGP("get_ipv6_addr: invalid char. \'%c\'\n", ch);
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return 0;
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}
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if (!saw_xdigit) {
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if (colonp) {
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DEBUGP("invalid location of \"::\".\n");
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return 0;
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}
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colonp = tp;
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continue;
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} else if (*src == term) {
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DEBUGP("trancated IPv6 addr\n");
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return 0;
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}
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if (tp + 2 > endp)
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return 0;
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*tp++ = (u_int8_t) (val >> 8) & 0xff;
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*tp++ = (u_int8_t) val & 0xff;
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saw_xdigit = 0;
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val = 0;
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continue;
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}
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if (saw_xdigit) {
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if (tp + 2 > endp)
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return 0;
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*tp++ = (u_int8_t) (val >> 8) & 0xff;
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*tp++ = (u_int8_t) val & 0xff;
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}
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if (colonp != NULL) {
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/*
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* Since some memmove()'s erroneously fail to handle
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* overlapping regions, we'll do the shift by hand.
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*/
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const int n = tp - colonp;
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int i;
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if (tp == endp)
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return 0;
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for (i = 1; i <= n; i++) {
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endp[- i] = colonp[n - i];
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colonp[n - i] = 0;
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}
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tp = endp;
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}
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if (tp != endp || (*src != term))
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return 0;
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memcpy(dst->s6_addr, tmp, sizeof(dst->s6_addr));
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return clen;
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}
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static int try_number(const char *data, size_t dlen, u_int32_t array[],
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int array_size, char sep, char term)
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{
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u_int32_t i, len;
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memset(array, 0, sizeof(array[0])*array_size);
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/* Keep data pointing at next char. */
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for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
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if (*data >= '0' && *data <= '9') {
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array[i] = array[i]*10 + *data - '0';
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}
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else if (*data == sep)
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i++;
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else {
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/* Unexpected character; true if it's the
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terminator and we're finished. */
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if (*data == term && i == array_size - 1)
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return len;
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DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
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len, i, *data);
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return 0;
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}
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}
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DEBUGP("Failed to fill %u numbers separated by %c\n", array_size, sep);
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return 0;
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}
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/* Returns 0, or length of numbers: 192,168,1,1,5,6 */
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static int try_rfc959(const char *data, size_t dlen,
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struct nf_conntrack_man *cmd, char term)
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{
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int length;
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u_int32_t array[6];
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length = try_number(data, dlen, array, 6, ',', term);
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if (length == 0)
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return 0;
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cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16) |
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(array[2] << 8) | array[3]);
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cmd->u.tcp.port = htons((array[4] << 8) | array[5]);
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return length;
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}
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/* Grab port: number up to delimiter */
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static int get_port(const char *data, int start, size_t dlen, char delim,
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u_int16_t *port)
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{
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u_int16_t tmp_port = 0;
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int i;
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for (i = start; i < dlen; i++) {
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/* Finished? */
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if (data[i] == delim) {
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if (tmp_port == 0)
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break;
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*port = htons(tmp_port);
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DEBUGP("get_port: return %d\n", tmp_port);
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return i + 1;
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}
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else if (data[i] >= '0' && data[i] <= '9')
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tmp_port = tmp_port*10 + data[i] - '0';
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else { /* Some other crap */
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DEBUGP("get_port: invalid char.\n");
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break;
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}
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}
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return 0;
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}
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/* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
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static int try_eprt(const char *data, size_t dlen, struct nf_conntrack_man *cmd,
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char term)
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{
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char delim;
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int length;
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/* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
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then delimiter again. */
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if (dlen <= 3) {
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DEBUGP("EPRT: too short\n");
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return 0;
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}
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delim = data[0];
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if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
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DEBUGP("try_eprt: invalid delimitter.\n");
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return 0;
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}
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if ((cmd->l3num == PF_INET && data[1] != '1') ||
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(cmd->l3num == PF_INET6 && data[1] != '2')) {
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DEBUGP("EPRT: invalid protocol number.\n");
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return 0;
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}
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DEBUGP("EPRT: Got %c%c%c\n", delim, data[1], delim);
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if (data[1] == '1') {
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u_int32_t array[4];
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/* Now we have IP address. */
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length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
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if (length != 0)
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cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16)
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| (array[2] << 8) | array[3]);
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} else {
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/* Now we have IPv6 address. */
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length = get_ipv6_addr(data + 3, dlen - 3,
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(struct in6_addr *)cmd->u3.ip6, delim);
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}
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if (length == 0)
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return 0;
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DEBUGP("EPRT: Got IP address!\n");
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/* Start offset includes initial "|1|", and trailing delimiter */
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return get_port(data, 3 + length + 1, dlen, delim, &cmd->u.tcp.port);
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}
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/* Returns 0, or length of numbers: |||6446| */
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static int try_epsv_response(const char *data, size_t dlen,
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struct nf_conntrack_man *cmd, char term)
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{
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char delim;
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/* Three delimiters. */
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if (dlen <= 3) return 0;
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delim = data[0];
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if (isdigit(delim) || delim < 33 || delim > 126
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|| data[1] != delim || data[2] != delim)
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return 0;
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return get_port(data, 3, dlen, delim, &cmd->u.tcp.port);
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}
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/* Return 1 for match, 0 for accept, -1 for partial. */
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static int find_pattern(const char *data, size_t dlen,
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const char *pattern, size_t plen,
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char skip, char term,
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unsigned int *numoff,
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unsigned int *numlen,
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struct nf_conntrack_man *cmd,
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int (*getnum)(const char *, size_t,
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struct nf_conntrack_man *, char))
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{
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size_t i;
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DEBUGP("find_pattern `%s': dlen = %u\n", pattern, dlen);
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if (dlen == 0)
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return 0;
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if (dlen <= plen) {
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/* Short packet: try for partial? */
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if (strnicmp(data, pattern, dlen) == 0)
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return -1;
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else return 0;
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}
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if (strnicmp(data, pattern, plen) != 0) {
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#if 0
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size_t i;
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DEBUGP("ftp: string mismatch\n");
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for (i = 0; i < plen; i++) {
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DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
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i, data[i], data[i],
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pattern[i], pattern[i]);
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}
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#endif
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return 0;
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}
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DEBUGP("Pattern matches!\n");
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/* Now we've found the constant string, try to skip
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to the 'skip' character */
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for (i = plen; data[i] != skip; i++)
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if (i == dlen - 1) return -1;
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/* Skip over the last character */
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i++;
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DEBUGP("Skipped up to `%c'!\n", skip);
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*numoff = i;
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*numlen = getnum(data + i, dlen - i, cmd, term);
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if (!*numlen)
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return -1;
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DEBUGP("Match succeeded!\n");
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return 1;
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}
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/* Look up to see if we're just after a \n. */
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static int find_nl_seq(u32 seq, const struct ip_ct_ftp_master *info, int dir)
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{
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unsigned int i;
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for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
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if (info->seq_aft_nl[dir][i] == seq)
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return 1;
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return 0;
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}
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/* We don't update if it's older than what we have. */
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static void update_nl_seq(u32 nl_seq, struct ip_ct_ftp_master *info, int dir,
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struct sk_buff *skb)
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{
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unsigned int i, oldest = NUM_SEQ_TO_REMEMBER;
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/* Look for oldest: if we find exact match, we're done. */
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for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
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if (info->seq_aft_nl[dir][i] == nl_seq)
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return;
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if (oldest == info->seq_aft_nl_num[dir]
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|| before(info->seq_aft_nl[dir][i], oldest))
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oldest = i;
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}
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if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
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info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
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nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
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} else if (oldest != NUM_SEQ_TO_REMEMBER) {
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info->seq_aft_nl[dir][oldest] = nl_seq;
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nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
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}
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}
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static int help(struct sk_buff **pskb,
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unsigned int protoff,
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struct nf_conn *ct,
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enum ip_conntrack_info ctinfo)
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{
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unsigned int dataoff, datalen;
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struct tcphdr _tcph, *th;
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char *fb_ptr;
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int ret;
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u32 seq;
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int dir = CTINFO2DIR(ctinfo);
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unsigned int matchlen, matchoff;
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struct ip_ct_ftp_master *ct_ftp_info = &ct->help->ct_ftp_info;
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struct nf_conntrack_expect *exp;
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struct nf_conntrack_man cmd = {};
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unsigned int i;
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int found = 0, ends_in_nl;
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/* Until there's been traffic both ways, don't look in packets. */
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if (ctinfo != IP_CT_ESTABLISHED
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&& ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
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DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo);
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return NF_ACCEPT;
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}
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th = skb_header_pointer(*pskb, protoff, sizeof(_tcph), &_tcph);
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if (th == NULL)
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return NF_ACCEPT;
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dataoff = protoff + th->doff * 4;
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/* No data? */
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if (dataoff >= (*pskb)->len) {
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DEBUGP("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
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(*pskb)->len);
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return NF_ACCEPT;
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}
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datalen = (*pskb)->len - dataoff;
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spin_lock_bh(&nf_ftp_lock);
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fb_ptr = skb_header_pointer(*pskb, dataoff, datalen, ftp_buffer);
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BUG_ON(fb_ptr == NULL);
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ends_in_nl = (fb_ptr[datalen - 1] == '\n');
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seq = ntohl(th->seq) + datalen;
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/* Look up to see if we're just after a \n. */
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if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
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/* Now if this ends in \n, update ftp info. */
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DEBUGP("nf_conntrack_ftp_help: wrong seq pos %s(%u) or %s(%u)\n",
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ct_ftp_info->seq_aft_nl_num[dir] > 0 ? "" : "(UNSET)",
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ct_ftp_info->seq_aft_nl[dir][0],
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ct_ftp_info->seq_aft_nl_num[dir] > 1 ? "" : "(UNSET)",
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ct_ftp_info->seq_aft_nl[dir][1]);
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ret = NF_ACCEPT;
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goto out_update_nl;
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}
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/* Initialize IP/IPv6 addr to expected address (it's not mentioned
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in EPSV responses) */
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cmd.l3num = ct->tuplehash[dir].tuple.src.l3num;
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memcpy(cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
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sizeof(cmd.u3.all));
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for (i = 0; i < ARRAY_SIZE(search); i++) {
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if (search[i].dir != dir) continue;
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found = find_pattern(fb_ptr, datalen,
|
|
search[i].pattern,
|
|
search[i].plen,
|
|
search[i].skip,
|
|
search[i].term,
|
|
&matchoff, &matchlen,
|
|
&cmd,
|
|
search[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[i].pattern,
|
|
ntohl(th->seq), datalen);
|
|
ret = NF_DROP;
|
|
goto out;
|
|
} else if (found == 0) { /* No match */
|
|
ret = NF_ACCEPT;
|
|
goto out_update_nl;
|
|
}
|
|
|
|
DEBUGP("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
|
|
(int)matchlen, fb_ptr + matchoff,
|
|
matchlen, ntohl(th->seq) + matchoff);
|
|
|
|
exp = nf_conntrack_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. */
|
|
exp->tuple.dst.u3 = 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) {
|
|
DEBUGP("conntrack_ftp: NOT RECORDING: " NIPQUAD_FMT " != " NIPQUAD_FMT "\n",
|
|
NIPQUAD(cmd.u3.ip),
|
|
NIPQUAD(ct->tuplehash[dir].tuple.src.u3.ip));
|
|
} else {
|
|
DEBUGP("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
|
|
<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;
|
|
}
|
|
memcpy(&exp->tuple.dst.u3, &cmd.u3.all,
|
|
sizeof(exp->tuple.dst.u3));
|
|
}
|
|
|
|
exp->tuple.src.u3 = ct->tuplehash[!dir].tuple.src.u3;
|
|
exp->tuple.src.l3num = cmd.l3num;
|
|
exp->tuple.src.u.tcp.port = 0;
|
|
exp->tuple.dst.u.tcp.port = cmd.u.tcp.port;
|
|
exp->tuple.dst.protonum = IPPROTO_TCP;
|
|
|
|
exp->mask = (struct nf_conntrack_tuple)
|
|
{ .src = { .l3num = 0xFFFF,
|
|
.u = { .tcp = { 0 }},
|
|
},
|
|
.dst = { .protonum = 0xFF,
|
|
.u = { .tcp = { 0xFFFF }},
|
|
},
|
|
};
|
|
if (cmd.l3num == PF_INET) {
|
|
exp->mask.src.u3.ip = 0xFFFFFFFF;
|
|
exp->mask.dst.u3.ip = 0xFFFFFFFF;
|
|
} else {
|
|
memset(exp->mask.src.u3.ip6, 0xFF,
|
|
sizeof(exp->mask.src.u3.ip6));
|
|
memset(exp->mask.dst.u3.ip6, 0xFF,
|
|
sizeof(exp->mask.src.u3.ip6));
|
|
}
|
|
|
|
exp->expectfn = NULL;
|
|
exp->flags = 0;
|
|
|
|
/* Now, NAT might want to mangle the packet, and register the
|
|
* (possibly changed) expectation itself. */
|
|
if (nf_nat_ftp_hook)
|
|
ret = nf_nat_ftp_hook(pskb, ctinfo, search[i].ftptype,
|
|
matchoff, matchlen, exp, &seq);
|
|
else {
|
|
/* Can't expect this? Best to drop packet now. */
|
|
if (nf_conntrack_expect_related(exp) != 0)
|
|
ret = NF_DROP;
|
|
else
|
|
ret = NF_ACCEPT;
|
|
}
|
|
|
|
out_put_expect:
|
|
nf_conntrack_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, *pskb);
|
|
out:
|
|
spin_unlock_bh(&nf_ftp_lock);
|
|
return ret;
|
|
}
|
|
|
|
static struct nf_conntrack_helper ftp[MAX_PORTS][2];
|
|
static char ftp_names[MAX_PORTS][2][sizeof("ftp-65535")];
|
|
|
|
/* don't make this __exit, since it's called from __init ! */
|
|
static void 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;
|
|
|
|
DEBUGP("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 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++) {
|
|
memset(&ftp[i], 0, sizeof(struct nf_conntrack_helper));
|
|
|
|
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].mask.src.u.tcp.port = 0xFFFF;
|
|
ftp[i][j].mask.dst.protonum = 0xFF;
|
|
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;
|
|
|
|
DEBUGP("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]);
|
|
fini();
|
|
return ret;
|
|
}
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
module_init(init);
|
|
module_exit(fini);
|