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[NETFILTER]: amanda helper: convert to textsearch infrastructure
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When a port number within a packet is replaced by a differently sized
number only the packet is resized, but not the copy of the data.
Following port numbers are rewritten based on their offsets within
the copy, leading to packet corruption.

Convert the amanda helper to the textsearch infrastructure to avoid
the copy entirely.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Patrick McHardy authored and David S. Miller committed Jun 18, 2006
1 parent 7d8c501 commit c952616
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Showing 2 changed files with 96 additions and 49 deletions.
2 changes: 2 additions & 0 deletions net/ipv4/netfilter/Kconfig
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Original file line number Diff line number Diff line change
Expand Up @@ -142,6 +142,8 @@ config IP_NF_TFTP
config IP_NF_AMANDA
tristate "Amanda backup protocol support"
depends on IP_NF_CONNTRACK
select TEXTSEARCH
select TEXTSEARCH_KMP
help
If you are running the Amanda backup package <http://www.amanda.org/>
on this machine or machines that will be MASQUERADED through this
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143 changes: 94 additions & 49 deletions net/ipv4/netfilter/ip_conntrack_amanda.c
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Original file line number Diff line number Diff line change
Expand Up @@ -17,33 +17,29 @@
* this value.
*
*/

#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/netfilter.h>
#include <linux/ip.h>
#include <linux/moduleparam.h>
#include <linux/textsearch.h>
#include <linux/skbuff.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/udp.h>
#include <net/checksum.h>
#include <net/udp.h>

#include <linux/netfilter.h>
#include <linux/netfilter_ipv4/ip_conntrack_helper.h>
#include <linux/netfilter_ipv4/ip_conntrack_amanda.h>

static unsigned int master_timeout = 300;
static char *ts_algo = "kmp";

MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>");
MODULE_DESCRIPTION("Amanda connection tracking module");
MODULE_LICENSE("GPL");
module_param(master_timeout, uint, 0600);
MODULE_PARM_DESC(master_timeout, "timeout for the master connection");

static const char *conns[] = { "DATA ", "MESG ", "INDEX " };

/* This is slow, but it's simple. --RR */
static char *amanda_buffer;
static DEFINE_SPINLOCK(amanda_buffer_lock);
module_param(ts_algo, charp, 0400);
MODULE_PARM_DESC(ts_algo, "textsearch algorithm to use (default kmp)");

unsigned int (*ip_nat_amanda_hook)(struct sk_buff **pskb,
enum ip_conntrack_info ctinfo,
Expand All @@ -52,12 +48,48 @@ unsigned int (*ip_nat_amanda_hook)(struct sk_buff **pskb,
struct ip_conntrack_expect *exp);
EXPORT_SYMBOL_GPL(ip_nat_amanda_hook);

enum amanda_strings {
SEARCH_CONNECT,
SEARCH_NEWLINE,
SEARCH_DATA,
SEARCH_MESG,
SEARCH_INDEX,
};

static struct {
char *string;
size_t len;
struct ts_config *ts;
} search[] = {
[SEARCH_CONNECT] = {
.string = "CONNECT ",
.len = 8,
},
[SEARCH_NEWLINE] = {
.string = "\n",
.len = 1,
},
[SEARCH_DATA] = {
.string = "DATA ",
.len = 5,
},
[SEARCH_MESG] = {
.string = "MESG ",
.len = 5,
},
[SEARCH_INDEX] = {
.string = "INDEX ",
.len = 6,
},
};

static int help(struct sk_buff **pskb,
struct ip_conntrack *ct, enum ip_conntrack_info ctinfo)
{
struct ts_state ts;
struct ip_conntrack_expect *exp;
char *data, *data_limit, *tmp;
unsigned int dataoff, i;
unsigned int dataoff, start, stop, off, i;
char pbuf[sizeof("65535")], *tmp;
u_int16_t port, len;
int ret = NF_ACCEPT;

Expand All @@ -77,29 +109,34 @@ static int help(struct sk_buff **pskb,
return NF_ACCEPT;
}

spin_lock_bh(&amanda_buffer_lock);
skb_copy_bits(*pskb, dataoff, amanda_buffer, (*pskb)->len - dataoff);
data = amanda_buffer;
data_limit = amanda_buffer + (*pskb)->len - dataoff;
*data_limit = '\0';

/* Search for the CONNECT string */
data = strstr(data, "CONNECT ");
if (!data)
memset(&ts, 0, sizeof(ts));
start = skb_find_text(*pskb, dataoff, (*pskb)->len,
search[SEARCH_CONNECT].ts, &ts);
if (start == UINT_MAX)
goto out;
data += strlen("CONNECT ");
start += dataoff + search[SEARCH_CONNECT].len;

/* Only search first line. */
if ((tmp = strchr(data, '\n')))
*tmp = '\0';
memset(&ts, 0, sizeof(ts));
stop = skb_find_text(*pskb, start, (*pskb)->len,
search[SEARCH_NEWLINE].ts, &ts);
if (stop == UINT_MAX)
goto out;
stop += start;

for (i = 0; i < ARRAY_SIZE(conns); i++) {
char *match = strstr(data, conns[i]);
if (!match)
for (i = SEARCH_DATA; i <= SEARCH_INDEX; i++) {
memset(&ts, 0, sizeof(ts));
off = skb_find_text(*pskb, start, stop, search[i].ts, &ts);
if (off == UINT_MAX)
continue;
tmp = data = match + strlen(conns[i]);
port = simple_strtoul(data, &data, 10);
len = data - tmp;
off += start + search[i].len;

len = min_t(unsigned int, sizeof(pbuf) - 1, stop - off);
if (skb_copy_bits(*pskb, off, pbuf, len))
break;
pbuf[len] = '\0';

port = simple_strtoul(pbuf, &tmp, 10);
len = tmp - pbuf;
if (port == 0 || len > 5)
break;

Expand All @@ -125,21 +162,19 @@ static int help(struct sk_buff **pskb,
exp->mask.dst.u.tcp.port = 0xFFFF;

if (ip_nat_amanda_hook)
ret = ip_nat_amanda_hook(pskb, ctinfo,
tmp - amanda_buffer,
ret = ip_nat_amanda_hook(pskb, ctinfo, off - dataoff,
len, exp);
else if (ip_conntrack_expect_related(exp) != 0)
ret = NF_DROP;
ip_conntrack_expect_put(exp);
}

out:
spin_unlock_bh(&amanda_buffer_lock);
return ret;
}

static struct ip_conntrack_helper amanda_helper = {
.max_expected = ARRAY_SIZE(conns),
.max_expected = 3,
.timeout = 180,
.me = THIS_MODULE,
.help = help,
Expand All @@ -155,26 +190,36 @@ static struct ip_conntrack_helper amanda_helper = {

static void __exit ip_conntrack_amanda_fini(void)
{
int i;

ip_conntrack_helper_unregister(&amanda_helper);
kfree(amanda_buffer);
for (i = 0; i < ARRAY_SIZE(search); i++)
textsearch_destroy(search[i].ts);
}

static int __init ip_conntrack_amanda_init(void)
{
int ret;

amanda_buffer = kmalloc(65536, GFP_KERNEL);
if (!amanda_buffer)
return -ENOMEM;

ret = ip_conntrack_helper_register(&amanda_helper);
if (ret < 0) {
kfree(amanda_buffer);
return ret;
int ret, i;

ret = -ENOMEM;
for (i = 0; i < ARRAY_SIZE(search); i++) {
search[i].ts = textsearch_prepare(ts_algo, search[i].string,
search[i].len,
GFP_KERNEL, TS_AUTOLOAD);
if (search[i].ts == NULL)
goto err;
}
ret = ip_conntrack_helper_register(&amanda_helper);
if (ret < 0)
goto err;
return 0;


err:
for (; i >= 0; i--) {
if (search[i].ts)
textsearch_destroy(search[i].ts);
}
return ret;
}

module_init(ip_conntrack_amanda_init);
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