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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/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_CRYPT.h"
#ifdef MODULE_LICENSE
MODULE_LICENSE("GPL");
#endif
#ifdef MODULE_DESCRIPTION
MODULE_DESCRIPTION("SEPPL iptables Encryption Target");
#endif
#ifdef MODULE_AUTHOR
MODULE_AUTHOR("Lennart Poettering <"PACKAGE_BUGREPORT">");
#endif
static unsigned int ipt_CRYPT_target(struct sk_buff **pskb,
const struct net_device *in,
const struct net_device *out,
unsigned int hooknum,
const void *_ti,
void *userinfo) {
const struct ipt_crypt_info *ti = _ti;
struct iphdr *ih;
unsigned d, new_l, crypt_l, ihl;
struct seppl_uncrypt_hdr *uh;
struct seppl_crypt_hdr *ch;
u8 *iv, *pl;
int ivs = ti->key->ivsize;
int bs = ti->key->blocksize;
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;
// Calculate new packet size
new_l = ihl + sizeof(struct seppl_uncrypt_hdr) + ivs + ((sizeof(struct seppl_crypt_hdr) + ntohs(ih->tot_len) - ihl + bs - 1) / bs) * bs;
d = new_l - htons(ih->tot_len);
crypt_l = new_l - ihl - sizeof(struct seppl_uncrypt_hdr) - ivs;
//DEBUGP("CRYPT: tot_len=%i, new_l=%i, d=%i, crypt_l=%i\n", htons(ih->tot_len), new_l, d, crypt_l);
// Copy the skb if needed and increase it correctly
if (skb_tailroom(*pskb) < d || skb_cloned(*pskb)) {
struct sk_buff *n;
if (!(n = skb_copy_expand(*pskb, skb_headroom(*pskb), d, GFP_ATOMIC))) {
if (net_ratelimit())
printk(KERN_ERR "ipt_CRYPT: Unable to allocate larger skb, dropping packet.\n");
return NF_DROP;
}
if ((*pskb)->sk)
skb_set_owner_w(n, (*pskb)->sk);
kfree_skb(*pskb);
*pskb = n;
ih = (*pskb)->nh.iph;
}
skb_put(*pskb, d);
// Calculate some pointers
//ih = ... /* IP-Header */
uh = (struct seppl_uncrypt_hdr*) ((u8*) ih + ihl); /* Unencrypted header */
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 */
// Copy the payload
memmove(pl, uh, ntohs(ih->tot_len) - ihl);
// Fill the uncrypted header
uh->algorithm = ti->key->algorithm;
strncpy(uh->key_name, ti->key->name, 7);
// Copy the IV
seppl_copy_iv(ti->key, iv);
// Encrypt to make it randomish
sg[0].page = virt_to_page((void*) iv);
sg[0].offset = (((long) (void *) iv) & ~PAGE_MASK);
sg[0].length = ivs;
crypto_cipher_encrypt(ti->key->tfm_ecb, sg, sg, sg[0].length );
// Fill the crypted header
ch->ident = 0x00;
ch->saved_protocol = ih->protocol;
ch->saved_tot_len = ih->tot_len;
ch->saved_frag_off = ih->frag_off;
// Fill the IP header
ih->protocol = SEPPL_PROTOCOL;
ih->tot_len = htons(new_l);
ih->frag_off = 0;
// Checksum FIXME: Is this really needed?
ih->check = 0;
ih->check = ip_fast_csum((char *) ih, ih->ihl);
// Crypt
sg[0].page = virt_to_page((void*) ch);
sg[0].offset = (((long) (void *) ch) & ~PAGE_MASK);
sg[0].length = crypt_l;
crypto_cipher_set_iv(ti->key->tfm, iv, ti->key->ivsize);
if (crypto_cipher_encrypt(ti->key->tfm, sg, sg, sg[0].length)) {
if (net_ratelimit())
printk(KERN_ERR "ipt_CRYPT: encrypt() failure\n");
return NF_DROP;
}
// Finish
(*pskb)->ip_summed = CHECKSUM_NONE;
(*pskb)->nfcache |= NFC_UNKNOWN | NFC_ALTERED;
return IPT_CONTINUE;
}
static int ipt_CRYPT_check(const char *table, const struct ipt_entry *e, void *_ti, unsigned int ti_size, unsigned int hook_mask) {
struct ipt_crypt_info *ti = _ti;
if (ti_size != IPT_ALIGN(sizeof(struct ipt_crypt_info))) {
printk(KERN_ERR "ipt_CRYPT: Structure too small\n");
return 0;
}
if (strcmp(table, "mangle") != 0) {
printk(KERN_ERR "ipt_CRYPT: Not in mangle table\n");
return 0;
}
if ((hook_mask & ~(1 << NF_IP_POST_ROUTING)) != 0) {
printk(KERN_ERR "ipt_CRYPT: Not in POSTROUTING chain\n");
return 0;
}
if (!(ti->key = seppl_claim_key(ti->algorithm, ti->name))) {
printk(KERN_ERR "ipt_CRYPT: Cannot find key\n");
return 0;
}
return 1;
}
static void ipt_CRYPT_destroy(void *_ti, unsigned int ti_size) {
struct ipt_crypt_info *ti = _ti;
seppl_release_key(ti->key);
}
static struct ipt_target ipt_CRYPT_reg = {
{ NULL, NULL },
"CRYPT",
ipt_CRYPT_check,
ipt_CRYPT_destroy,
ipt_CRYPT_target,
THIS_MODULE
};
static int __init init(void) {
return ipt_register_target(&ipt_CRYPT_reg);
}
static void __exit fini(void) {
ipt_unregister_target(&ipt_CRYPT_reg);
}
module_init(init);
module_exit(fini);
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