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/* $Id$ */
/***
This file is part of seppl
seppl is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
seppl is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with seppl; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
USA
***/
#include <linux/config.h>
#if defined(CONFIG_MODVERSIONS) && !defined(MODVERSIONS)
#define MODVERSIONS
#endif
#if defined(MODVERSIONS) && !defined(__GENKSYMS__)
#include <linux/modversions.h>
#include "seppl.ver"
#endif
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <net/ip.h>
#include <net/checksum.h>
struct in_device;
#include <net/route.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <asm/scatterlist.h>
#include "seppl.h"
#include "ipt_DECRYPT.h"
#ifdef MODULE_LICENSE
MODULE_LICENSE("GPL");
#endif
#ifdef MODULE_DESCRIPTION
MODULE_DESCRIPTION ("SEPPL iptables Decryption Target");
#endif
#ifdef MODULE_AUTHOR
MODULE_AUTHOR("Lennart Poettering <"PACKAGE_BUGREPORT">");
#endif
static unsigned int ipt_DECRYPT_target(struct sk_buff **pskb,
const struct net_device *in,
const struct net_device *out,
unsigned int hooknum,
const void *_ti,
void *userinfo) {
struct iphdr *ih;
unsigned ihl;
struct seppl_key *key;
struct seppl_uncrypt_hdr *uh;
struct seppl_crypt_hdr *ch;
u8* iv, *pl;
int ivs;
int crypt_l, bs;
struct scatterlist sg[1];
if (!skb_ip_make_writable(pskb, (*pskb)->len)) {
if (net_ratelimit())
printk(KERN_ERR "ipt_DECRYPT: Failed to make skb writable.\n");
return NF_DROP;
}
ih = (*pskb)->nh.iph;
ihl = ih->ihl<<2;
if (ih->protocol != SEPPL_PROTOCOL) {
if (net_ratelimit())
printk(KERN_ERR "ipt_DECRYPT: Incorrect protocol 0x%02x\n", ih->protocol);
return NF_DROP;
}
if (ntohs(ih->tot_len) <= ihl+sizeof(struct seppl_uncrypt_hdr)) {
if (net_ratelimit())
printk(KERN_ERR "ipt_DECRYPT: Packet too short (1)\n");
return NF_DROP;
}
uh = (struct seppl_uncrypt_hdr*) ((u8*) ih + ihl); /* Unencrypted header */
if (!(key = seppl_claim_key(uh->algorithm, uh->key_name))) {
if (net_ratelimit())
printk(KERN_ERR "ipt_DECRYPT: Recieved packet with unknown decryption key.\n");
return NF_DROP;
}
ivs = key->ivsize;
bs = key->blocksize;
if (ntohs(ih->tot_len) <= ihl+sizeof(struct seppl_uncrypt_hdr)+ivs+sizeof(struct seppl_crypt_hdr)) {
if (net_ratelimit())
printk(KERN_ERR "ipt_DECRYPT: Packet too short (2)\n");
seppl_release_key(key);
return NF_DROP;
}
crypt_l = ntohs(ih->tot_len)-ihl-sizeof(struct seppl_uncrypt_hdr)-ivs;
if (crypt_l % bs) {
if (net_ratelimit())
printk(KERN_ERR "ipt_DECRYPT: Packet too short (3)\n");
seppl_release_key(key);
return NF_DROP;
}
iv = ((u8*) uh) + sizeof(struct seppl_uncrypt_hdr); /* IV */
ch = (struct seppl_crypt_hdr*) (iv + ivs); /* Crypted header */
pl = ((u8*) ch) + sizeof(struct seppl_crypt_hdr); /* Payload */
sg[0].page = virt_to_page(ch);
sg[0].offset = ((long) ch & ~PAGE_MASK);
sg[0].length = crypt_l;
crypto_cipher_set_iv(key->tfm, iv, key->ivsize);
if (crypto_cipher_decrypt(key->tfm, sg, sg, sg[0].length)) {
if (net_ratelimit())
printk(KERN_ERR "ipt_DECRYPT: decrypt() failure\n");
seppl_release_key(key);
return NF_DROP;
}
seppl_release_key(key);
if (ch->ident != 0x00) {
if (net_ratelimit())
printk(KERN_ERR "ipt_DECRYPT: Key not matching\n");
return NF_DROP;
}
if (ntohs(ch->saved_tot_len) >
ntohs(ih->tot_len) -
sizeof(struct seppl_uncrypt_hdr)-
ivs-
sizeof(struct seppl_crypt_hdr)) {
if (net_ratelimit())
printk(KERN_ERR "ipt_DECRYPT: Packet too short (4)");
return NF_DROP;
}
//DEBUGP("DECRYPT: tot_len=%i, real_l=%i, crypt_l=%i\n", htons(ih->tot_len), ntohs(ch->saved_tot_len), crypt_l);
// Restore the IP header
ih->protocol = ch->saved_protocol;
ih->tot_len = ch->saved_tot_len;
ih->frag_off = ch->saved_frag_off;
// The pay load
memmove(uh, pl, ntohs(ih->tot_len)-ihl);
// Checksum
ih->check = 0;
ih->check = ip_fast_csum((char *) ih, ih->ihl);
skb_trim(*pskb, ntohs(ih->tot_len));
// Finish
(*pskb)->ip_summed = CHECKSUM_NONE;
(*pskb)->nfcache |= NFC_UNKNOWN | NFC_ALTERED;
return IPT_CONTINUE;
}
static int ipt_DECRYPT_check(const char *table, const struct ipt_entry *e, void *_ti, unsigned int ti_size, unsigned int hook_mask) {
if (ti_size != IPT_ALIGN(sizeof(struct ipt_decrypt_info))) {
printk(KERN_ERR "ipt_DECRYPT: Structure too small");
return 0;
}
if (strcmp(table, "mangle") != 0) {
printk(KERN_ERR "ipt_DECRYPT: Not in mangle table\n");
return 0;
}
if ((hook_mask & ~(1 << NF_IP_PRE_ROUTING)) != 0) {
printk(KERN_ERR "ipt_DECRYPT: Not in PREROUTING chain");
return 0;
}
return 1;
}
static struct ipt_target ipt_DECRYPT_reg = {
{ NULL, NULL },
"DECRYPT",
ipt_DECRYPT_check,
NULL,
ipt_DECRYPT_target,
THIS_MODULE
};
static int __init init(void) {
if (ipt_register_target(&ipt_DECRYPT_reg))
return -EINVAL;
return 0;
}
static void __exit fini(void) {
ipt_unregister_target(&ipt_DECRYPT_reg);
}
module_init(init);
module_exit(fini);
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