1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
|
/*
* Shared library add-on to iptables to add TCPOPTSTRIP target support.
* Copyright (c) 2007 Sven Schnelle <svens@bitebene.org>
* Copyright © CC Computer Consultants GmbH, 2007
* Jan Engelhardt <jengelh@computergmbh.de>
*/
#include <getopt.h>
#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <xtables.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_TCPOPTSTRIP.h>
#ifndef TCPOPT_MD5SIG
# define TCPOPT_MD5SIG 19
#endif
enum {
FLAG_STRIP = 1 << 0,
};
struct tcp_optionmap {
const char *name, *desc;
const unsigned int option;
};
static const struct option tcpoptstrip_tg_opts[] = {
{.name = "strip-options", .has_arg = true, .val = 's'},
{ .name = NULL }
};
static const struct tcp_optionmap tcp_optionmap[] = {
{"wscale", "Window scale", TCPOPT_WINDOW},
{"mss", "Maximum Segment Size", TCPOPT_MAXSEG},
{"sack-permitted", "SACK permitted", TCPOPT_SACK_PERMITTED},
{"sack", "Selective ACK", TCPOPT_SACK},
{"timestamp", "Timestamp", TCPOPT_TIMESTAMP},
{"md5", "MD5 signature", TCPOPT_MD5SIG},
{ .name = NULL }
};
static void tcpoptstrip_tg_help(void)
{
const struct tcp_optionmap *w;
printf(
"TCPOPTSTRIP target options:\n"
" --strip-options value strip specified TCP options denoted by value\n"
" (separated by comma) from TCP header\n"
" Instead of the numeric value, you can also use the following names:\n"
);
for (w = tcp_optionmap; w->name != NULL; ++w)
printf(" %-14s strip \"%s\" option\n", w->name, w->desc);
}
static void tcpoptstrip_tg_init(struct xt_entry_target *t)
{
struct xt_tcpoptstrip_target_info *info = (void *)t->data;
/* strictly necessary? play safe for now. */
memset(info->strip_bmap, 0, sizeof(info->strip_bmap));
}
static void parse_list(struct xt_tcpoptstrip_target_info *info, char *arg)
{
unsigned int option;
char *p;
int i;
while (true) {
p = strchr(arg, ',');
if (p != NULL)
*p = '\0';
option = 0;
for (i = 0; tcp_optionmap[i].name != NULL; ++i)
if (strcmp(tcp_optionmap[i].name, arg) == 0) {
option = tcp_optionmap[i].option;
break;
}
if (option == 0 && string_to_number(arg, 0, 255, &option) == -1)
exit_error(PARAMETER_PROBLEM,
"Bad TCP option value \"%s\"", arg);
if (option < 2)
exit_error(PARAMETER_PROBLEM,
"Option value may not be 0 or 1");
if (tcpoptstrip_test_bit(info->strip_bmap, option))
exit_error(PARAMETER_PROBLEM,
"Option \"%s\" already specified", arg);
tcpoptstrip_set_bit(info->strip_bmap, option);
if (p == NULL)
break;
arg = p + 1;
}
}
static int tcpoptstrip_tg_parse(int c, char **argv, int invert,
unsigned int *flags, const void *entry,
struct xt_entry_target **target)
{
struct xt_tcpoptstrip_target_info *info = (void *)(*target)->data;
switch (c) {
case 's':
if (*flags & FLAG_STRIP)
exit_error(PARAMETER_PROBLEM,
"You can specify --strip-options only once");
parse_list(info, optarg);
*flags |= FLAG_STRIP;
return true;
}
return false;
}
static void tcpoptstrip_tg_check(unsigned int flags)
{
if (flags == 0)
exit_error(PARAMETER_PROBLEM,
"TCPOPTSTRIP: --strip-options parameter required");
}
static void
tcpoptstrip_print_list(const struct xt_tcpoptstrip_target_info *info,
bool numeric)
{
unsigned int i, j;
const char *name;
bool first = true;
for (i = 0; i < 256; ++i) {
if (!tcpoptstrip_test_bit(info->strip_bmap, i))
continue;
if (!first)
printf(",");
first = false;
name = NULL;
if (!numeric)
for (j = 0; tcp_optionmap[j].name != NULL; ++j)
if (tcp_optionmap[j].option == i)
name = tcp_optionmap[j].name;
if (name != NULL)
printf("%s", name);
else
printf("%u", i);
}
}
static void
tcpoptstrip_tg_print(const void *ip, const struct xt_entry_target *target,
int numeric)
{
const struct xt_tcpoptstrip_target_info *info =
(const void *)target->data;
printf("TCPOPTSTRIP options ");
tcpoptstrip_print_list(info, numeric);
}
static void
tcpoptstrip_tg_save(const void *ip, const struct xt_entry_target *target)
{
const struct xt_tcpoptstrip_target_info *info =
(const void *)target->data;
printf("--strip-options ");
tcpoptstrip_print_list(info, true);
}
static struct xtables_target tcpoptstrip_tg_reg = {
.version = IPTABLES_VERSION,
.name = "TCPOPTSTRIP",
.family = AF_INET,
.size = XT_ALIGN(sizeof(struct xt_tcpoptstrip_target_info)),
.userspacesize = XT_ALIGN(sizeof(struct xt_tcpoptstrip_target_info)),
.help = tcpoptstrip_tg_help,
.init = tcpoptstrip_tg_init,
.parse = tcpoptstrip_tg_parse,
.final_check = tcpoptstrip_tg_check,
.print = tcpoptstrip_tg_print,
.save = tcpoptstrip_tg_save,
.extra_opts = tcpoptstrip_tg_opts,
};
static struct xtables_target tcpoptstrip_tg6_reg = {
.version = IPTABLES_VERSION,
.name = "TCPOPTSTRIP",
.family = AF_INET6,
.size = XT_ALIGN(sizeof(struct xt_tcpoptstrip_target_info)),
.userspacesize = XT_ALIGN(sizeof(struct xt_tcpoptstrip_target_info)),
.help = tcpoptstrip_tg_help,
.init = tcpoptstrip_tg_init,
.parse = tcpoptstrip_tg_parse,
.final_check = tcpoptstrip_tg_check,
.print = tcpoptstrip_tg_print,
.save = tcpoptstrip_tg_save,
.extra_opts = tcpoptstrip_tg_opts,
};
void _init(void)
{
xtables_register_target(&tcpoptstrip_tg_reg);
xtables_register_target(&tcpoptstrip_tg6_reg);
}
|
