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/*
web (experimental)
HTTP client request match
Copyright (C) 2006 Jonathan Zarate
Licensed under GNU GPL v2 or later.
*/
#include <linux/module.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ipt_web.h>
MODULE_AUTHOR("Jonathan Zarate");
MODULE_DESCRIPTION("HTTP client request match (experimental)");
MODULE_LICENSE("GPL");
// #define LOG printk
#define LOG(...) do { } while (0);
static int find(const char *data, const char *tail, const char *text)
{
int n, o;
int dlen;
const char *p, *e;
while ((data < tail) && (*data == ' ')) ++data;
while ((tail > data) && (*(tail - 1) == ' ')) --tail;
dlen = tail - data;
#if 0
{
char tmp[128];
int z;
z = sizeof(tmp) - 1;
if (z > dlen) z = dlen;
memcpy(tmp, data, z);
tmp[z] = 0;
LOG(KERN_INFO "find in '%s'\n", tmp);
}
#endif
// 012345
// text
// ^text
// text$
// ^text$
// 012345
while (*text) {
n = o = strlen(text);
if (*text == '^') {
--n;
if (*(text + n) == '$') {
// exact
--n;
if ((dlen == n) && (memcmp(data, text + 1, n) == 0)) {
LOG(KERN_INFO "matched %s\n", text);
return 1;
}
}
else {
// begins with
if ((dlen >= n) && (memcmp(data, text + 1, n) == 0)) {
LOG(KERN_INFO "matched %s\n", text);
return 1;
}
}
}
else if (*(text + n - 1) == '$') {
// ends with
--n;
if (memcmp(tail - n, text, n) == 0) {
LOG(KERN_INFO "matched %s\n", text);
return 1;
}
}
else {
// contains
p = data;
e = tail - n;
while (p <= e) {
if (memcmp(p, text, n) == 0) {
LOG(KERN_INFO "matched %s\n", text);
return 1;
}
++p;
}
}
text += o + 1;
}
return 0;
}
static inline const char *findend(const char *data, const char *tail, int min)
{
int n = tail - data;
if (n >= min) {
while (data < tail) {
if (*data == '\r') return data;
++data;
}
}
return NULL;
}
static int match(const struct sk_buff *skb, const struct net_device *in, const struct net_device *out,
const void *matchinfo, int offset, const void *hdr, u_int16_t datalen, int *hotdrop)
{
const struct ipt_web_info *info;
const struct tcphdr *tcph;
const char *data;
const char *tail;
const char *p, *q;
int doff, dlen;
info = matchinfo;
if (offset != 0) return info->invert;
tcph = hdr;
doff = (tcph->doff * 4);
data = (char *)tcph + doff;
dlen = datalen - doff;
#if 0
printk(KERN_INFO "datalen=%u dlen=%d doff=%d\n", datalen, dlen, doff);
char tmp[16];
memcpy(tmp, data, sizeof(tmp));
tmp[sizeof(tmp) - 1] = 0;
printk(KERN_INFO "[%s]\n", tmp);
#endif
// POST / HTTP/1.0$$$$
// GET / HTTP/1.0$$$$
// 1234567890123456789
if (dlen < 18) return info->invert;
// "GET " or "POST"
__u32 sig = *(__u32 *)data;
if ((sig != __constant_htonl(0x47455420)) && (sig != __constant_htonl(0x504f5354))) {
return info->invert;
}
tail = data + dlen;
if (dlen > 1024) {
dlen = 1024;
tail = data + 1024;
}
// POST / HTTP/1.0$$$$
// GET / HTTP/1.0$$$$ -- minimum
// 0123456789012345678
// 9876543210
if (((p = findend(data + 14, tail, 18)) == NULL) || (memcmp(p - 9, " HTTP/", 6) != 0))
return info->invert;
#if 0
{
const char *qq = info->text;
while (*qq) {
printk(KERN_INFO "text=%s\n", qq);
qq += strlen(qq) + 1;
}
}
#endif
switch (info->mode) {
case IPT_WEB_HTTP:
return !info->invert;
case IPT_WEB_HORE:
// entire request line, else host line
if (find(data + 4, p - 9, info->text)) return !info->invert;
break;
case IPT_WEB_PATH:
// left side of '?' or entire line
q = data += 4;
p -= 9;
while ((q < p) && (*q != '?')) ++q;
return find(data, q, info->text) ^ info->invert;
case IPT_WEB_QUERY:
// right side of '?' or none
q = data + 4;
p -= 9;
while ((q < p) && (*q != '?')) ++q;
if (q >= p) return info->invert;
return find(q + 1, p, info->text) ^ info->invert;
case IPT_WEB_RURI:
// entire request line
return find(data + 4, p - 9, info->text) ^ info->invert;
default:
// shutup compiler
break;
}
// else, IPT_WEB_HOST
while (1) {
data = p + 2; // skip previous \r\n
p = findend(data, tail, 8); // p = current line's \r
if (p == NULL) return 0;
#if 0
char tmp[64];
memcpy(tmp, data, 32);
tmp[32] = 0;
printk(KERN_INFO "data=[%s]\n", tmp);
#endif
if (memcmp(data, "Host: ", 6) == 0)
return find(data + 6, p, info->text) ^ info->invert;
}
return !info->invert;
}
static int checkentry(const char *tablename, const struct ipt_ip *ip, void *matchinfo,
unsigned int matchsize, unsigned int hook_mask)
{
return (matchsize == IPT_ALIGN(sizeof(struct ipt_web_info)));
}
static struct ipt_match web_match
= { { NULL, NULL }, "web", &match, &checkentry, NULL, THIS_MODULE };
static int __init init(void)
{
// LOG(KERN_INFO "ipt_web <" __DATE__ " " __TIME__ "> loaded\n");
return ipt_register_match(&web_match);
}
static void __exit fini(void)
{
ipt_unregister_match(&web_match);
}
module_init(init);
module_exit(fini);
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