/*
* 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/err.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 <linux/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 unsigned int
setup_sg(struct scatterlist *sg, const void *address, unsigned int length)
{
sg_set_buf(sg, address, length);
return 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_blkcipher *arc4;
struct crypto_hash *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)
{
struct hash_desc desc;
struct scatterlist sg[4];
unsigned int nbytes;
sg_init_table(sg, 4);
nbytes = setup_sg(&sg[0], state->master_key, state->keylen);
nbytes += setup_sg(&sg[1], sha_pad->sha_pad1,
sizeof(sha_pad->sha_pad1));
nbytes += setup_sg(&sg[2], state->session_key, state->keylen);
nbytes += setup_sg(&sg[3], sha_pad->sha_pad2,
sizeof(sha_pad->sha_pad2));
desc.tfm = state->sha1;
desc.flags = 0;
crypto_hash_digest(&desc, sg, nbytes, state->sha1_digest);
}
/*
* 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)
{
struct scatterlist sg_in[1], sg_out[1];
struct blkcipher_desc desc = { .tfm = state->arc4 };
get_new_key_from_sha(state);
if (!initial_key) {
crypto_blkcipher_setkey(state->arc4, state->sha1_digest,
state->keylen);
sg_init_table(sg_in, 1);
sg_init_table(sg_out, 1);
setup_sg(sg_in, state->sha1_digest, state->keylen);
setup_sg(sg_out, state->session_key, state->keylen);
if (crypto_blkcipher_encrypt(&desc, sg_out, sg_in,
state->keylen) != 0) {
printk(KERN_WARNING "mppe_rekey: cipher_encrypt failed\n");
}
} else {
memcpy(state->session_key, state->sha1_digest, 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_blkcipher_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 = kzalloc(sizeof(*state), GFP_KERNEL);
if (state == NULL)
goto out;
state->arc4 = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
if (IS_ERR(state->arc4)) {
state->arc4 = NULL;
goto out_free;
}
state->sha1 = crypto_alloc_hash("sha1", 0, CRYPTO_ALG_ASYNC);
if (IS_ERR(state->sha1)) {
state->sha1 = NULL;
goto out_free;
}
digestsize = crypto_hash_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_hash(state->sha1);
if (state->arc4)
crypto_free_blkcipher(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_hash(state->sha1);
if (state->arc4)
crypto_free_blkcipher(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;
struct blkcipher_desc desc = { .tfm = state->arc4 };
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 */
sg_init_table(sg_in, 1);
sg_init_table(sg_out, 1);
setup_sg(sg_in, ibuf, isize);
setup_sg(sg_out, obuf, osize);
if (crypto_blkcipher_encrypt(&desc, 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;
struct blkcipher_desc desc = { .tfm = state->arc4 };
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.
*/
sg_init_table(sg_in, 1);
sg_init_table(sg_out, 1);
setup_sg(sg_in, ibuf, 1);
setup_sg(sg_out, obuf, 1);
if (crypto_blkcipher_decrypt(&desc, 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_blkcipher_decrypt(&desc, sg_out, sg_in, isize - 1)) {
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_has_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC) &&
crypto_has_hash("sha1", 0, CRYPTO_ALG_ASYNC)))
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);
