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[PPP]: add PPP MPPE encryption module

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From: Matt Domsch <Matt_Domsch@dell.com>

The patch below implements the Microsoft Point-to-Point Encryption method
as a PPP compressor/decompressor.  This is necessary for Linux clients and
servers to interoperate with Microsoft Point-to-Point Tunneling Protocol
(PPTP) servers (either Microsoft PPTP servers or the poptop project) which
use MPPE to encrypt data when creating a VPN.

This patch differs from the kernel_ppp_mppe DKMS pacakge at
pptpclient.sourceforge.net by utilizing the kernel crypto routines rather
than providing its own SHA1 and arcfour implementations.

Minor changes to ppp_generic.c try to prevent a link from disabling
compression (in our case, the encryption) after it has started using
compression (encryption).

Feedback to <pptpclient-devel@lists.sourceforge.net> please.

Signed-off-by: Matt Domsch <Matt_Domsch@dell.com>
Cc: James Cameron <james.cameron@hp.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Brice Goglin <Brice.Goglin@ens-lyon.org>
Acked-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Matt Domsch 2005-11-08 09:40:47 -08:00 committed by David S. Miller
parent 6722e78c90
commit b3f9b92a6e
7 changed files with 902 additions and 26 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

13
drivers/net/Kconfig
View file

@ -2523,6 +2523,19 @@ config PPP_BSDCOMP
module; it is called bsd_comp and will show up in the directory
modules once you have said "make modules". If unsure, say N.
config PPP_MPPE
tristate "PPP MPPE compression (encryption) (EXPERIMENTAL)"
depends on PPP && EXPERIMENTAL
select CRYPTO
select CRYPTO_SHA1
select CRYPTO_ARC4
---help---
Support for the MPPE Encryption protocol, as employed by the
Microsoft Point-to-Point Tunneling Protocol.
See http://pptpclient.sourceforge.net/ for information on
configuring PPTP clients and servers to utilize this method.
config PPPOE
tristate "PPP over Ethernet (EXPERIMENTAL)"
depends on EXPERIMENTAL && PPP

1
drivers/net/Makefile
View file

@ -112,6 +112,7 @@ obj-$(CONFIG_PPP_ASYNC) += ppp_async.o
obj-$(CONFIG_PPP_SYNC_TTY) += ppp_synctty.o
obj-$(CONFIG_PPP_DEFLATE) += ppp_deflate.o
obj-$(CONFIG_PPP_BSDCOMP) += bsd_comp.o
obj-$(CONFIG_PPP_MPPE) += ppp_mppe.o
obj-$(CONFIG_PPPOE) += pppox.o pppoe.o
obj-$(CONFIG_SLIP) += slip.o

88
drivers/net/ppp_generic.c
View file

@ -137,13 +137,14 @@ struct ppp {
/*
* Bits in flags: SC_NO_TCP_CCID, SC_CCP_OPEN, SC_CCP_UP, SC_LOOP_TRAFFIC,
* SC_MULTILINK, SC_MP_SHORTSEQ, SC_MP_XSHORTSEQ, SC_COMP_TCP, SC_REJ_COMP_TCP.
* SC_MULTILINK, SC_MP_SHORTSEQ, SC_MP_XSHORTSEQ, SC_COMP_TCP, SC_REJ_COMP_TCP,
* SC_MUST_COMP
* Bits in rstate: SC_DECOMP_RUN, SC_DC_ERROR, SC_DC_FERROR.
* Bits in xstate: SC_COMP_RUN
*/
#define SC_FLAG_BITS (SC_NO_TCP_CCID|SC_CCP_OPEN|SC_CCP_UP|SC_LOOP_TRAFFIC \
|SC_MULTILINK|SC_MP_SHORTSEQ|SC_MP_XSHORTSEQ \
|SC_COMP_TCP|SC_REJ_COMP_TCP)
|SC_COMP_TCP|SC_REJ_COMP_TCP|SC_MUST_COMP)
/*
* Private data structure for each channel.
@ -1027,6 +1028,56 @@ ppp_xmit_process(struct ppp *ppp)
ppp_xmit_unlock(ppp);
}
static inline struct sk_buff *
pad_compress_skb(struct ppp *ppp, struct sk_buff *skb)
{
struct sk_buff *new_skb;
int len;
int new_skb_size = ppp->dev->mtu +
ppp->xcomp->comp_extra + ppp->dev->hard_header_len;
int compressor_skb_size = ppp->dev->mtu +
ppp->xcomp->comp_extra + PPP_HDRLEN;
new_skb = alloc_skb(new_skb_size, GFP_ATOMIC);
if (!new_skb) {
if (net_ratelimit())
printk(KERN_ERR "PPP: no memory (comp pkt)\n");
return NULL;
}
if (ppp->dev->hard_header_len > PPP_HDRLEN)
skb_reserve(new_skb,
ppp->dev->hard_header_len - PPP_HDRLEN);
/* compressor still expects A/C bytes in hdr */
len = ppp->xcomp->compress(ppp->xc_state, skb->data - 2,
new_skb->data, skb->len + 2,
compressor_skb_size);
if (len > 0 && (ppp->flags & SC_CCP_UP)) {
kfree_skb(skb);
skb = new_skb;
skb_put(skb, len);
skb_pull(skb, 2); /* pull off A/C bytes */
} else if (len == 0) {
/* didn't compress, or CCP not up yet */
kfree_skb(new_skb);
new_skb = skb;
} else {
/*
* (len < 0)
* MPPE requires that we do not send unencrypted
* frames. The compressor will return -1 if we
* should drop the frame. We cannot simply test
* the compress_proto because MPPE and MPPC share
* the same number.
*/
if (net_ratelimit())
printk(KERN_ERR "ppp: compressor dropped pkt\n");
kfree_skb(skb);
kfree_skb(new_skb);
new_skb = NULL;
}
return new_skb;
}
/*
* Compress and send a frame.
* The caller should have locked the xmit path,
@ -1113,29 +1164,14 @@ ppp_send_frame(struct ppp *ppp, struct sk_buff *skb)
/* try to do packet compression */
if ((ppp->xstate & SC_COMP_RUN) && ppp->xc_state != 0
&& proto != PPP_LCP && proto != PPP_CCP) {
new_skb = alloc_skb(ppp->dev->mtu + ppp->dev->hard_header_len,
GFP_ATOMIC);
if (new_skb == 0) {
printk(KERN_ERR "PPP: no memory (comp pkt)\n");
if (!(ppp->flags & SC_CCP_UP) && (ppp->flags & SC_MUST_COMP)) {
if (net_ratelimit())
printk(KERN_ERR "ppp: compression required but down - pkt dropped.\n");
goto drop;
}
if (ppp->dev->hard_header_len > PPP_HDRLEN)
skb_reserve(new_skb,
ppp->dev->hard_header_len - PPP_HDRLEN);
/* compressor still expects A/C bytes in hdr */
len = ppp->xcomp->compress(ppp->xc_state, skb->data - 2,
new_skb->data, skb->len + 2,
ppp->dev->mtu + PPP_HDRLEN);
if (len > 0 && (ppp->flags & SC_CCP_UP)) {
kfree_skb(skb);
skb = new_skb;
skb_put(skb, len);
skb_pull(skb, 2); /* pull off A/C bytes */
} else {
/* didn't compress, or CCP not up yet */
kfree_skb(new_skb);
}
skb = pad_compress_skb(ppp, skb);
if (!skb)
goto drop;
}
/*
@ -1155,7 +1191,8 @@ ppp_send_frame(struct ppp *ppp, struct sk_buff *skb)
return;
drop:
kfree_skb(skb);
if (skb)
kfree_skb(skb);
++ppp->stats.tx_errors;
}
@ -1552,6 +1589,9 @@ ppp_receive_nonmp_frame(struct ppp *ppp, struct sk_buff *skb)
&& (ppp->rstate & (SC_DC_FERROR | SC_DC_ERROR)) == 0)
skb = ppp_decompress_frame(ppp, skb);
if (ppp->flags & SC_MUST_COMP && ppp->rstate & SC_DC_FERROR)
goto err;
proto = PPP_PROTO(skb);
switch (proto) {
case PPP_VJC_COMP:

724
drivers/net/ppp_mppe.c Normal file
View file

@ -0,0 +1,724 @@
/*
* ppp_mppe.c - interface MPPE to the PPP code.
* This version is for use with Linux kernel 2.6.14+
*
* By Frank Cusack <fcusack@fcusack.com>.
* Copyright (c) 2002,2003,2004 Google, Inc.
* All rights reserved.
*
* License:
* Permission to use, copy, modify, and distribute this software and its
* documentation is hereby granted, provided that the above copyright
* notice appears in all copies. This software is provided without any
* warranty, express or implied.
*
* ALTERNATIVELY, provided that this notice is retained in full, this product
* may be distributed under the terms of the GNU General Public License (GPL),
* in which case the provisions of the GPL apply INSTEAD OF those given above.
*
* This program 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.
*
* This program 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 this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*
* Changelog:
* 08/12/05 - Matt Domsch <Matt_Domsch@dell.com>
* Only need extra skb padding on transmit, not receive.
* 06/18/04 - Matt Domsch <Matt_Domsch@dell.com>, Oleg Makarenko <mole@quadra.ru>
* Use Linux kernel 2.6 arc4 and sha1 routines rather than
* providing our own.
* 2/15/04 - TS: added #include <version.h> and testing for Kernel
* version before using
* MOD_DEC_USAGE_COUNT/MOD_INC_USAGE_COUNT which are
* deprecated in 2.6
*/
#include <linux/config.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/version.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/crypto.h>
#include <linux/mm.h>
#include <linux/ppp_defs.h>
#include <linux/ppp-comp.h>
#include <asm/scatterlist.h>
#include "ppp_mppe.h"
MODULE_AUTHOR("Frank Cusack <fcusack@fcusack.com>");
MODULE_DESCRIPTION("Point-to-Point Protocol Microsoft Point-to-Point Encryption support");
MODULE_LICENSE("Dual BSD/GPL");
MODULE_ALIAS("ppp-compress-" __stringify(CI_MPPE));
MODULE_VERSION("1.0.2");
static void
setup_sg(struct scatterlist *sg, const void *address, unsigned int length)
{
sg[0].page = virt_to_page(address);
sg[0].offset = offset_in_page(address);
sg[0].length = length;
}
#define SHA1_PAD_SIZE 40
/*
* kernel crypto API needs its arguments to be in kmalloc'd memory, not in the module
* static data area. That means sha_pad needs to be kmalloc'd.
*/
struct sha_pad {
unsigned char sha_pad1[SHA1_PAD_SIZE];
unsigned char sha_pad2[SHA1_PAD_SIZE];
};
static struct sha_pad *sha_pad;
static inline void sha_pad_init(struct sha_pad *shapad)
{
memset(shapad->sha_pad1, 0x00, sizeof(shapad->sha_pad1));
memset(shapad->sha_pad2, 0xF2, sizeof(shapad->sha_pad2));
}
/*
* State for an MPPE (de)compressor.
*/
struct ppp_mppe_state {
struct crypto_tfm *arc4;
struct crypto_tfm *sha1;
unsigned char *sha1_digest;
unsigned char master_key[MPPE_MAX_KEY_LEN];
unsigned char session_key[MPPE_MAX_KEY_LEN];
unsigned keylen; /* key length in bytes */
/* NB: 128-bit == 16, 40-bit == 8! */
/* If we want to support 56-bit, */
/* the unit has to change to bits */
unsigned char bits; /* MPPE control bits */
unsigned ccount; /* 12-bit coherency count (seqno) */
unsigned stateful; /* stateful mode flag */
int discard; /* stateful mode packet loss flag */
int sanity_errors; /* take down LCP if too many */
int unit;
int debug;
struct compstat stats;
};
/* struct ppp_mppe_state.bits definitions */
#define MPPE_BIT_A 0x80 /* Encryption table were (re)inititalized */
#define MPPE_BIT_B 0x40 /* MPPC only (not implemented) */
#define MPPE_BIT_C 0x20 /* MPPC only (not implemented) */
#define MPPE_BIT_D 0x10 /* This is an encrypted frame */
#define MPPE_BIT_FLUSHED MPPE_BIT_A
#define MPPE_BIT_ENCRYPTED MPPE_BIT_D
#define MPPE_BITS(p) ((p)[4] & 0xf0)
#define MPPE_CCOUNT(p) ((((p)[4] & 0x0f) << 8) + (p)[5])
#define MPPE_CCOUNT_SPACE 0x1000 /* The size of the ccount space */
#define MPPE_OVHD 2 /* MPPE overhead/packet */
#define SANITY_MAX 1600 /* Max bogon factor we will tolerate */
/*
* Key Derivation, from RFC 3078, RFC 3079.
* Equivalent to Get_Key() for MS-CHAP as described in RFC 3079.
*/
static void get_new_key_from_sha(struct ppp_mppe_state * state, unsigned char *InterimKey)
{
struct scatterlist sg[4];
setup_sg(&sg[0], state->master_key, state->keylen);
setup_sg(&sg[1], sha_pad->sha_pad1, sizeof(sha_pad->sha_pad1));
setup_sg(&sg[2], state->session_key, state->keylen);
setup_sg(&sg[3], sha_pad->sha_pad2, sizeof(sha_pad->sha_pad2));
crypto_digest_digest (state->sha1, sg, 4, state->sha1_digest);
memcpy(InterimKey, state->sha1_digest, state->keylen);
}
/*
* Perform the MPPE rekey algorithm, from RFC 3078, sec. 7.3.
* Well, not what's written there, but rather what they meant.
*/
static void mppe_rekey(struct ppp_mppe_state * state, int initial_key)
{
unsigned char InterimKey[MPPE_MAX_KEY_LEN];
struct scatterlist sg_in[1], sg_out[1];
get_new_key_from_sha(state, InterimKey);
if (!initial_key) {
crypto_cipher_setkey(state->arc4, InterimKey, state->keylen);
setup_sg(sg_in, InterimKey, state->keylen);
setup_sg(sg_out, state->session_key, state->keylen);
if (crypto_cipher_encrypt(state->arc4, sg_out, sg_in,
state->keylen) != 0) {
printk(KERN_WARNING "mppe_rekey: cipher_encrypt failed\n");
}
} else {
memcpy(state->session_key, InterimKey, state->keylen);
}
if (state->keylen == 8) {
/* See RFC 3078 */
state->session_key[0] = 0xd1;
state->session_key[1] = 0x26;
state->session_key[2] = 0x9e;
}
crypto_cipher_setkey(state->arc4, state->session_key, state->keylen);
}
/*
* Allocate space for a (de)compressor.
*/
static void *mppe_alloc(unsigned char *options, int optlen)
{
struct ppp_mppe_state *state;
unsigned int digestsize;
if (optlen != CILEN_MPPE + sizeof(state->master_key)
|| options[0] != CI_MPPE || options[1] != CILEN_MPPE)
goto out;
state = (struct ppp_mppe_state *) kmalloc(sizeof(*state), GFP_KERNEL);
if (state == NULL)
goto out;
memset(state, 0, sizeof(*state));
state->arc4 = crypto_alloc_tfm("arc4", 0);
if (!state->arc4)
goto out_free;
state->sha1 = crypto_alloc_tfm("sha1", 0);
if (!state->sha1)
goto out_free;
digestsize = crypto_tfm_alg_digestsize(state->sha1);
if (digestsize < MPPE_MAX_KEY_LEN)
goto out_free;
state->sha1_digest = kmalloc(digestsize, GFP_KERNEL);
if (!state->sha1_digest)
goto out_free;
/* Save keys. */
memcpy(state->master_key, &options[CILEN_MPPE],
sizeof(state->master_key));
memcpy(state->session_key, state->master_key,
sizeof(state->master_key));
/*
* We defer initial key generation until mppe_init(), as mppe_alloc()
* is called frequently during negotiation.
*/
return (void *)state;
out_free:
if (state->sha1_digest)
kfree(state->sha1_digest);
if (state->sha1)
crypto_free_tfm(state->sha1);
if (state->arc4)
crypto_free_tfm(state->arc4);
kfree(state);
out:
return NULL;
}
/*
* Deallocate space for a (de)compressor.
*/
static void mppe_free(void *arg)
{
struct ppp_mppe_state *state = (struct ppp_mppe_state *) arg;
if (state) {
if (state->sha1_digest)
kfree(state->sha1_digest);
if (state->sha1)
crypto_free_tfm(state->sha1);
if (state->arc4)
crypto_free_tfm(state->arc4);
kfree(state);
}
}
/*
* Initialize (de)compressor state.
*/
static int
mppe_init(void *arg, unsigned char *options, int optlen, int unit, int debug,
const char *debugstr)
{
struct ppp_mppe_state *state = (struct ppp_mppe_state *) arg;
unsigned char mppe_opts;
if (optlen != CILEN_MPPE
|| options[0] != CI_MPPE || options[1] != CILEN_MPPE)
return 0;
MPPE_CI_TO_OPTS(&options[2], mppe_opts);
if (mppe_opts & MPPE_OPT_128)
state->keylen = 16;
else if (mppe_opts & MPPE_OPT_40)
state->keylen = 8;
else {
printk(KERN_WARNING "%s[%d]: unknown key length\n", debugstr,
unit);
return 0;
}
if (mppe_opts & MPPE_OPT_STATEFUL)
state->stateful = 1;
/* Generate the initial session key. */
mppe_rekey(state, 1);
if (debug) {
int i;
char mkey[sizeof(state->master_key) * 2 + 1];
char skey[sizeof(state->session_key) * 2 + 1];
printk(KERN_DEBUG "%s[%d]: initialized with %d-bit %s mode\n",
debugstr, unit, (state->keylen == 16) ? 128 : 40,
(state->stateful) ? "stateful" : "stateless");
for (i = 0; i < sizeof(state->master_key); i++)
sprintf(mkey + i * 2, "%02x", state->master_key[i]);
for (i = 0; i < sizeof(state->session_key); i++)
sprintf(skey + i * 2, "%02x", state->session_key[i]);
printk(KERN_DEBUG
"%s[%d]: keys: master: %s initial session: %s\n",
debugstr, unit, mkey, skey);
}
/*
* Initialize the coherency count. The initial value is not specified
* in RFC 3078, but we can make a reasonable assumption that it will
* start at 0. Setting it to the max here makes the comp/decomp code
* do the right thing (determined through experiment).
*/
state->ccount = MPPE_CCOUNT_SPACE - 1;
/*
* Note that even though we have initialized the key table, we don't
* set the FLUSHED bit. This is contrary to RFC 3078, sec. 3.1.
*/
state->bits = MPPE_BIT_ENCRYPTED;
state->unit = unit;
state->debug = debug;
return 1;
}
static int
mppe_comp_init(void *arg, unsigned char *options, int optlen, int unit,
int hdrlen, int debug)
{
/* ARGSUSED */
return mppe_init(arg, options, optlen, unit, debug, "mppe_comp_init");
}
/*
* We received a CCP Reset-Request (actually, we are sending a Reset-Ack),
* tell the compressor to rekey. Note that we MUST NOT rekey for
* every CCP Reset-Request; we only rekey on the next xmit packet.
* We might get multiple CCP Reset-Requests if our CCP Reset-Ack is lost.
* So, rekeying for every CCP Reset-Request is broken as the peer will not
* know how many times we've rekeyed. (If we rekey and THEN get another
* CCP Reset-Request, we must rekey again.)
*/
static void mppe_comp_reset(void *arg)
{
struct ppp_mppe_state *state = (struct ppp_mppe_state *) arg;
state->bits |= MPPE_BIT_FLUSHED;
}
/*
* Compress (encrypt) a packet.
* It's strange to call this a compressor, since the output is always
* MPPE_OVHD + 2 bytes larger than the input.
*/
static int
mppe_compress(void *arg, unsigned char *ibuf, unsigned char *obuf,
int isize, int osize)
{
struct ppp_mppe_state *state = (struct ppp_mppe_state *) arg;
int proto;
struct scatterlist sg_in[1], sg_out[1];
/*
* Check that the protocol is in the range we handle.
*/
proto = PPP_PROTOCOL(ibuf);
if (proto < 0x0021 || proto > 0x00fa)
return 0;
/* Make sure we have enough room to generate an encrypted packet. */
if (osize < isize + MPPE_OVHD + 2) {
/* Drop the packet if we should encrypt it, but can't. */
printk(KERN_DEBUG "mppe_compress[%d]: osize too small! "
"(have: %d need: %d)\n", state->unit,
osize, osize + MPPE_OVHD + 2);
return -1;
}
osize = isize + MPPE_OVHD + 2;
/*
* Copy over the PPP header and set control bits.
*/
obuf[0] = PPP_ADDRESS(ibuf);
obuf[1] = PPP_CONTROL(ibuf);
obuf[2] = PPP_COMP >> 8; /* isize + MPPE_OVHD + 1 */
obuf[3] = PPP_COMP; /* isize + MPPE_OVHD + 2 */
obuf += PPP_HDRLEN;
state->ccount = (state->ccount + 1) % MPPE_CCOUNT_SPACE;
if (state->debug >= 7)
printk(KERN_DEBUG "mppe_compress[%d]: ccount %d\n", state->unit,
state->ccount);
obuf[0] = state->ccount >> 8;
obuf[1] = state->ccount & 0xff;
if (!state->stateful || /* stateless mode */
((state->ccount & 0xff) == 0xff) || /* "flag" packet */
(state->bits & MPPE_BIT_FLUSHED)) { /* CCP Reset-Request */
/* We must rekey */
if (state->debug && state->stateful)
printk(KERN_DEBUG "mppe_compress[%d]: rekeying\n",
state->unit);
mppe_rekey(state, 0);
state->bits |= MPPE_BIT_FLUSHED;
}
obuf[0] |= state->bits;
state->bits &= ~MPPE_BIT_FLUSHED; /* reset for next xmit */
obuf += MPPE_OVHD;
ibuf += 2; /* skip to proto field */
isize -= 2;
/* Encrypt packet */
setup_sg(sg_in, ibuf, isize);
setup_sg(sg_out, obuf, osize);
if (crypto_cipher_encrypt(state->arc4, sg_out, sg_in, isize) != 0) {
printk(KERN_DEBUG "crypto_cypher_encrypt failed\n");
return -1;
}
state->stats.unc_bytes += isize;
state->stats.unc_packets++;
state->stats.comp_bytes += osize;
state->stats.comp_packets++;
return osize;
}
/*
* Since every frame grows by MPPE_OVHD + 2 bytes, this is always going
* to look bad ... and the longer the link is up the worse it will get.
*/
static void mppe_comp_stats(void *arg, struct compstat *stats)
{
struct ppp_mppe_state *state = (struct ppp_mppe_state *) arg;
*stats = state->stats;
}
static int
mppe_decomp_init(void *arg, unsigned char *options, int optlen, int unit,
int hdrlen, int mru, int debug)
{
/* ARGSUSED */
return mppe_init(arg, options, optlen, unit, debug, "mppe_decomp_init");
}
/*
* We received a CCP Reset-Ack. Just ignore it.
*/
static void mppe_decomp_reset(void *arg)
{
/* ARGSUSED */
return;
}
/*
* Decompress (decrypt) an MPPE packet.
*/
static int
mppe_decompress(void *arg, unsigned char *ibuf, int isize, unsigned char *obuf,
int osize)
{
struct ppp_mppe_state *state = (struct ppp_mppe_state *) arg;
unsigned ccount;
int flushed = MPPE_BITS(ibuf) & MPPE_BIT_FLUSHED;
int sanity = 0;
struct scatterlist sg_in[1], sg_out[1];
if (isize <= PPP_HDRLEN + MPPE_OVHD) {
if (state->debug)
printk(KERN_DEBUG
"mppe_decompress[%d]: short pkt (%d)\n",
state->unit, isize);
return DECOMP_ERROR;
}
/*
* Make sure we have enough room to decrypt the packet.
* Note that for our test we only subtract 1 byte whereas in
* mppe_compress() we added 2 bytes (+MPPE_OVHD);
* this is to account for possible PFC.
*/
if (osize < isize - MPPE_OVHD - 1) {
printk(KERN_DEBUG "mppe_decompress[%d]: osize too small! "
"(have: %d need: %d)\n", state->unit,
osize, isize - MPPE_OVHD - 1);
return DECOMP_ERROR;
}
osize = isize - MPPE_OVHD - 2; /* assume no PFC */
ccount = MPPE_CCOUNT(ibuf);
if (state->debug >= 7)
printk(KERN_DEBUG "mppe_decompress[%d]: ccount %d\n",
state->unit, ccount);
/* sanity checks -- terminate with extreme prejudice */
if (!(MPPE_BITS(ibuf) & MPPE_BIT_ENCRYPTED)) {
printk(KERN_DEBUG
"mppe_decompress[%d]: ENCRYPTED bit not set!\n",
state->unit);
state->sanity_errors += 100;
sanity = 1;
}
if (!state->stateful && !flushed) {
printk(KERN_DEBUG "mppe_decompress[%d]: FLUSHED bit not set in "
"stateless mode!\n", state->unit);
state->sanity_errors += 100;
sanity = 1;
}
if (state->stateful && ((ccount & 0xff) == 0xff) && !flushed) {
printk(KERN_DEBUG "mppe_decompress[%d]: FLUSHED bit not set on "
"flag packet!\n", state->unit);
state->sanity_errors += 100;
sanity = 1;
}
if (sanity) {
if (state->sanity_errors < SANITY_MAX)
return DECOMP_ERROR;
else
/*
* Take LCP down if the peer is sending too many bogons.
* We don't want to do this for a single or just a few
* instances since it could just be due to packet corruption.
*/
return DECOMP_FATALERROR;
}
/*
* Check the coherency count.
*/
if (!state->stateful) {
/* RFC 3078, sec 8.1. Rekey for every packet. */
while (state->ccount != ccount) {
mppe_rekey(state, 0);
state->ccount = (state->ccount + 1) % MPPE_CCOUNT_SPACE;
}
} else {
/* RFC 3078, sec 8.2. */
if (!state->discard) {
/* normal state */
state->ccount = (state->ccount + 1) % MPPE_CCOUNT_SPACE;
if (ccount != state->ccount) {
/*
* (ccount > state->ccount)
* Packet loss detected, enter the discard state.
* Signal the peer to rekey (by sending a CCP Reset-Request).
*/
state->discard = 1;
return DECOMP_ERROR;
}
} else {
/* discard state */
if (!flushed) {
/* ccp.c will be silent (no additional CCP Reset-Requests). */
return DECOMP_ERROR;
} else {
/* Rekey for every missed "flag" packet. */
while ((ccount & ~0xff) !=
(state->ccount & ~0xff)) {
mppe_rekey(state, 0);
state->ccount =
(state->ccount +
256) % MPPE_CCOUNT_SPACE;
}
/* reset */
state->discard = 0;
state->ccount = ccount;
/*
* Another problem with RFC 3078 here. It implies that the
* peer need not send a Reset-Ack packet. But RFC 1962
* requires it. Hopefully, M$ does send a Reset-Ack; even
* though it isn't required for MPPE synchronization, it is
* required to reset CCP state.
*/
}
}
if (flushed)
mppe_rekey(state, 0);
}
/*
* Fill in the first part of the PPP header. The protocol field
* comes from the decrypted data.
*/
obuf[0] = PPP_ADDRESS(ibuf); /* +1 */
obuf[1] = PPP_CONTROL(ibuf); /* +1 */
obuf += 2;
ibuf += PPP_HDRLEN + MPPE_OVHD;
isize -= PPP_HDRLEN + MPPE_OVHD; /* -6 */
/* net osize: isize-4 */
/*
* Decrypt the first byte in order to check if it is
* a compressed or uncompressed protocol field.
*/
setup_sg(sg_in, ibuf, 1);
setup_sg(sg_out, obuf, 1);
if (crypto_cipher_decrypt(state->arc4, sg_out, sg_in, 1) != 0) {
printk(KERN_DEBUG "crypto_cypher_decrypt failed\n");
return DECOMP_ERROR;
}
/*
* Do PFC decompression.
* This would be nicer if we were given the actual sk_buff
* instead of a char *.
*/
if ((obuf[0] & 0x01) != 0) {
obuf[1] = obuf[0];
obuf[0] = 0;
obuf++;
osize++;
}
/* And finally, decrypt the rest of the packet. */
setup_sg(sg_in, ibuf + 1, isize - 1);
setup_sg(sg_out, obuf + 1, osize - 1);
if (crypto_cipher_decrypt(state->arc4, sg_out, sg_in, isize - 1) != 0) {
printk(KERN_DEBUG "crypto_cypher_decrypt failed\n");
return DECOMP_ERROR;
}
state->stats.unc_bytes += osize;
state->stats.unc_packets++;
state->stats.comp_bytes += isize;
state->stats.comp_packets++;
/* good packet credit */
state->sanity_errors >>= 1;
return osize;
}
/*
* Incompressible data has arrived (this should never happen!).
* We should probably drop the link if the protocol is in the range
* of what should be encrypted. At the least, we should drop this
* packet. (How to do this?)
*/
static void mppe_incomp(void *arg, unsigned char *ibuf, int icnt)
{
struct ppp_mppe_state *state = (struct ppp_mppe_state *) arg;
if (state->debug &&
(PPP_PROTOCOL(ibuf) >= 0x0021 && PPP_PROTOCOL(ibuf) <= 0x00fa))
printk(KERN_DEBUG
"mppe_incomp[%d]: incompressible (unencrypted) data! "
"(proto %04x)\n", state->unit, PPP_PROTOCOL(ibuf));
state->stats.inc_bytes += icnt;
state->stats.inc_packets++;
state->stats.unc_bytes += icnt;
state->stats.unc_packets++;
}
/*************************************************************
* Module interface table
*************************************************************/
/*
* Procedures exported to if_ppp.c.
*/
static struct compressor ppp_mppe = {
.compress_proto = CI_MPPE,
.comp_alloc = mppe_alloc,
.comp_free = mppe_free,
.comp_init = mppe_comp_init,
.comp_reset = mppe_comp_reset,
.compress = mppe_compress,
.comp_stat = mppe_comp_stats,
.decomp_alloc = mppe_alloc,
.decomp_free = mppe_free,
.decomp_init = mppe_decomp_init,
.decomp_reset = mppe_decomp_reset,
.decompress = mppe_decompress,
.incomp = mppe_incomp,
.decomp_stat = mppe_comp_stats,
.owner = THIS_MODULE,
.comp_extra = MPPE_PAD,
};
/*
* ppp_mppe_init()
*
* Prior to allowing load, try to load the arc4 and sha1 crypto
* libraries. The actual use will be allocated later, but
* this way the module will fail to insmod if they aren't available.
*/
static int __init ppp_mppe_init(void)
{
int answer;
if (!(crypto_alg_available("arc4", 0) &&
crypto_alg_available("sha1", 0)))
return -ENODEV;
sha_pad = kmalloc(sizeof(struct sha_pad), GFP_KERNEL);
if (!sha_pad)
return -ENOMEM;
sha_pad_init(sha_pad);
answer = ppp_register_compressor(&ppp_mppe);
if (answer == 0)
printk(KERN_INFO "PPP MPPE Compression module registered\n");
else
kfree(sha_pad);
return answer;
}
static void __exit ppp_mppe_cleanup(void)
{
ppp_unregister_compressor(&ppp_mppe);
kfree(sha_pad);
}
module_init(ppp_mppe_init);
module_exit(ppp_mppe_cleanup);

86
drivers/net/ppp_mppe.h Normal file
View file

@ -0,0 +1,86 @@
#define MPPE_PAD 4 /* MPPE growth per frame */
#define MPPE_MAX_KEY_LEN 16 /* largest key length (128-bit) */
/* option bits for ccp_options.mppe */
#define MPPE_OPT_40 0x01 /* 40 bit */
#define MPPE_OPT_128 0x02 /* 128 bit */
#define MPPE_OPT_STATEFUL 0x04 /* stateful mode */
/* unsupported opts */
#define MPPE_OPT_56 0x08 /* 56 bit */
#define MPPE_OPT_MPPC 0x10 /* MPPC compression */
#define MPPE_OPT_D 0x20 /* Unknown */
#define MPPE_OPT_UNSUPPORTED (MPPE_OPT_56|MPPE_OPT_MPPC|MPPE_OPT_D)
#define MPPE_OPT_UNKNOWN 0x40 /* Bits !defined in RFC 3078 were set */
/*
* This is not nice ... the alternative is a bitfield struct though.
* And unfortunately, we cannot share the same bits for the option
* names above since C and H are the same bit. We could do a u_int32
* but then we have to do a htonl() all the time and/or we still need
* to know which octet is which.
*/
#define MPPE_C_BIT 0x01 /* MPPC */
#define MPPE_D_BIT 0x10 /* Obsolete, usage unknown */
#define MPPE_L_BIT 0x20 /* 40-bit */
#define MPPE_S_BIT 0x40 /* 128-bit */
#define MPPE_M_BIT 0x80 /* 56-bit, not supported */
#define MPPE_H_BIT 0x01 /* Stateless (in a different byte) */
/* Does not include H bit; used for least significant octet only. */
#define MPPE_ALL_BITS (MPPE_D_BIT|MPPE_L_BIT|MPPE_S_BIT|MPPE_M_BIT|MPPE_H_BIT)
/* Build a CI from mppe opts (see RFC 3078) */
#define MPPE_OPTS_TO_CI(opts, ci) \
do { \
u_char *ptr = ci; /* u_char[4] */ \
\
/* H bit */ \
if (opts & MPPE_OPT_STATEFUL) \
*ptr++ = 0x0; \
else \
*ptr++ = MPPE_H_BIT; \
*ptr++ = 0; \
*ptr++ = 0; \
\
/* S,L bits */ \
*ptr = 0; \
if (opts & MPPE_OPT_128) \
*ptr |= MPPE_S_BIT; \
if (opts & MPPE_OPT_40) \
*ptr |= MPPE_L_BIT; \
/* M,D,C bits not supported */ \
} while (/* CONSTCOND */ 0)
/* The reverse of the above */
#define MPPE_CI_TO_OPTS(ci, opts) \
do { \
u_char *ptr = ci; /* u_char[4] */ \
\
opts = 0; \
\
/* H bit */ \
if (!(ptr[0] & MPPE_H_BIT)) \
opts |= MPPE_OPT_STATEFUL; \
\
/* S,L bits */ \
if (ptr[3] & MPPE_S_BIT) \
opts |= MPPE_OPT_128; \
if (ptr[3] & MPPE_L_BIT) \
opts |= MPPE_OPT_40; \
\
/* M,D,C bits */ \
if (ptr[3] & MPPE_M_BIT) \
opts |= MPPE_OPT_56; \
if (ptr[3] & MPPE_D_BIT) \
opts |= MPPE_OPT_D; \
if (ptr[3] & MPPE_C_BIT) \
opts |= MPPE_OPT_MPPC; \
\
/* Other bits */ \
if (ptr[0] & ~MPPE_H_BIT) \
opts |= MPPE_OPT_UNKNOWN; \
if (ptr[1] || ptr[2]) \
opts |= MPPE_OPT_UNKNOWN; \
if (ptr[3] & ~MPPE_ALL_BITS) \
opts |= MPPE_OPT_UNKNOWN; \
} while (/* CONSTCOND */ 0)

7
include/linux/if_ppp.h
View file

@ -21,7 +21,7 @@
*/
/*
* ==FILEVERSION 20000724==
* ==FILEVERSION 20050812==
*
* NOTE TO MAINTAINERS:
* If you modify this file at all, please set the above date.
@ -35,6 +35,8 @@
#ifndef _IF_PPP_H_
#define _IF_PPP_H_
#include <linux/compiler.h>
/*
* Packet sizes
*/
@ -70,7 +72,8 @@
#define SC_LOG_RAWIN 0x00080000 /* log all chars received */
#define SC_LOG_FLUSH 0x00100000 /* log all chars flushed */
#define SC_SYNC 0x00200000 /* synchronous serial mode */
#define SC_MASK 0x0f200fff /* bits that user can change */
#define SC_MUST_COMP 0x00400000 /* no uncompressed packets may be sent or received */
#define SC_MASK 0x0f600fff /* bits that user can change */
/* state bits */
#define SC_XMIT_BUSY 0x10000000 /* (used by isdn_ppp?) */

9
include/linux/ppp-comp.h
View file

@ -111,6 +111,8 @@ struct compressor {
/* Used in locking compressor modules */
struct module *owner;
/* Extra skb space needed by the compressor algorithm */
unsigned int comp_extra;
};
/*
@ -190,6 +192,13 @@ struct compressor {
#define DEFLATE_MAKE_OPT(w) ((((w) - 8) << 4) + DEFLATE_METHOD_VAL)
#define DEFLATE_CHK_SEQUENCE 0
/*
* Definitions for MPPE.
*/
#define CI_MPPE 18 /* config option for MPPE */
#define CILEN_MPPE 6 /* length of config option */
/*
* Definitions for other, as yet unsupported, compression methods.
*/