path: root/drivers/net/ppp/ppp_mppe.c

/*
 * 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, see <http://www.gnu.org/licenses/>.
 *
 *
 * 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 <crypto/hash.h>
#include <crypto/skcipher.h>
#include <linux/err.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/ppp_defs.h>
#include <linux/ppp-comp.h>
#include <linux/scatterlist.h>
#include <asm/unaligned.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_sync_skcipher *arc4;
	struct shash_desc *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)
{
	crypto_shash_init(state->sha1);
	crypto_shash_update(state->sha1, state->master_key,
			    state->keylen);
	crypto_shash_update(state->sha1, sha_pad->sha_pad1,
			    sizeof(sha_pad->sha_pad1));
	crypto_shash_update(state->sha1, state->session_key,
			    state->keylen);
	crypto_shash_update(state->sha1, sha_pad->sha_pad2,
			    sizeof(sha_pad->sha_pad2));
	crypto_shash_final(state->sha1, 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];
	SYNC_SKCIPHER_REQUEST_ON_STACK(req, state->arc4);

	skcipher_request_set_sync_tfm(req, state->arc4);
	skcipher_request_set_callback(req, 0, NULL, NULL);

	get_new_key_from_sha(state);
	if (!initial_key) {
		crypto_sync_skcipher_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);
		skcipher_request_set_crypt(req, sg_in, sg_out, state->keylen,
					   NULL);
		if (crypto_skcipher_encrypt(req))
    		    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_sync_skcipher_setkey(state->arc4, state->session_key,
				    state->keylen);
	skcipher_request_zero(req);
}

/*
 * Allocate space for a (de)compressor.
 */
static void *mppe_alloc(unsigned char *options, int optlen)
{
	struct ppp_mppe_state *state;
	struct crypto_shash *shash;
	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_sync_skcipher("ecb(arc4)", 0, 0);
	if (IS_ERR(state->arc4)) {
		state->arc4 = NULL;
		goto out_free;
	}

	shash = crypto_alloc_shash("sha1", 0, 0);
	if (IS_ERR(shash))
		goto out_free;

	state->sha1 = kmalloc(sizeof(*state->sha1) +
				     crypto_shash_descsize(shash),
			      GFP_KERNEL);
	if (!state->sha1) {
		crypto_free_shash