2 * ppp_mppe.c - interface MPPE to the PPP code.
3 * This version is for use with Linux kernel 2.6.14+
5 * By Frank Cusack <fcusack@fcusack.com>.
6 * Copyright (c) 2002,2003,2004 Google, Inc.
10 * Permission to use, copy, modify, and distribute this software and its
11 * documentation is hereby granted, provided that the above copyright
12 * notice appears in all copies. This software is provided without any
13 * warranty, express or implied.
15 * ALTERNATIVELY, provided that this notice is retained in full, this product
16 * may be distributed under the terms of the GNU General Public License (GPL),
17 * in which case the provisions of the GPL apply INSTEAD OF those given above.
19 * This program is free software; you can redistribute it and/or modify
20 * it under the terms of the GNU General Public License as published by
21 * the Free Software Foundation; either version 2 of the License, or
22 * (at your option) any later version.
24 * This program is distributed in the hope that it will be useful,
25 * but WITHOUT ANY WARRANTY; without even the implied warranty of
26 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
27 * GNU General Public License for more details.
29 * You should have received a copy of the GNU General Public License
30 * along with this program; if not, write to the Free Software
31 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
35 * 08/12/05 - Matt Domsch <Matt_Domsch@dell.com>
36 * Only need extra skb padding on transmit, not receive.
37 * 06/18/04 - Matt Domsch <Matt_Domsch@dell.com>, Oleg Makarenko <mole@quadra.ru>
38 * Use Linux kernel 2.6 arc4 and sha1 routines rather than
40 * 2/15/04 - TS: added #include <version.h> and testing for Kernel
41 * version before using
42 * MOD_DEC_USAGE_COUNT/MOD_INC_USAGE_COUNT which are
46 #include <linux/err.h>
47 #include <linux/module.h>
48 #include <linux/kernel.h>
49 #include <linux/version.h>
50 #include <linux/init.h>
51 #include <linux/types.h>
52 #include <linux/slab.h>
53 #include <linux/string.h>
54 #include <linux/crypto.h>
56 #include <linux/ppp_defs.h>
57 #include <linux/ppp-comp.h>
58 #include <asm/scatterlist.h>
62 MODULE_AUTHOR("Frank Cusack <fcusack@fcusack.com>");
63 MODULE_DESCRIPTION("Point-to-Point Protocol Microsoft Point-to-Point Encryption support");
64 MODULE_LICENSE("Dual BSD/GPL");
65 MODULE_ALIAS("ppp-compress-" __stringify(CI_MPPE));
66 MODULE_VERSION("1.0.2");
69 setup_sg(struct scatterlist *sg, const void *address, unsigned int length)
71 sg[0].page = virt_to_page(address);
72 sg[0].offset = offset_in_page(address);
73 sg[0].length = length;
76 #define SHA1_PAD_SIZE 40
79 * kernel crypto API needs its arguments to be in kmalloc'd memory, not in the module
80 * static data area. That means sha_pad needs to be kmalloc'd.
84 unsigned char sha_pad1[SHA1_PAD_SIZE];
85 unsigned char sha_pad2[SHA1_PAD_SIZE];
87 static struct sha_pad *sha_pad;
89 static inline void sha_pad_init(struct sha_pad *shapad)
91 memset(shapad->sha_pad1, 0x00, sizeof(shapad->sha_pad1));
92 memset(shapad->sha_pad2, 0xF2, sizeof(shapad->sha_pad2));
96 * State for an MPPE (de)compressor.
98 struct ppp_mppe_state {
99 struct crypto_blkcipher *arc4;
100 struct crypto_tfm *sha1;
101 unsigned char *sha1_digest;
102 unsigned char master_key[MPPE_MAX_KEY_LEN];
103 unsigned char session_key[MPPE_MAX_KEY_LEN];
104 unsigned keylen; /* key length in bytes */
105 /* NB: 128-bit == 16, 40-bit == 8! */
106 /* If we want to support 56-bit, */
107 /* the unit has to change to bits */
108 unsigned char bits; /* MPPE control bits */
109 unsigned ccount; /* 12-bit coherency count (seqno) */
110 unsigned stateful; /* stateful mode flag */
111 int discard; /* stateful mode packet loss flag */
112 int sanity_errors; /* take down LCP if too many */
115 struct compstat stats;
118 /* struct ppp_mppe_state.bits definitions */
119 #define MPPE_BIT_A 0x80 /* Encryption table were (re)inititalized */
120 #define MPPE_BIT_B 0x40 /* MPPC only (not implemented) */
121 #define MPPE_BIT_C 0x20 /* MPPC only (not implemented) */
122 #define MPPE_BIT_D 0x10 /* This is an encrypted frame */
124 #define MPPE_BIT_FLUSHED MPPE_BIT_A
125 #define MPPE_BIT_ENCRYPTED MPPE_BIT_D
127 #define MPPE_BITS(p) ((p)[4] & 0xf0)
128 #define MPPE_CCOUNT(p) ((((p)[4] & 0x0f) << 8) + (p)[5])
129 #define MPPE_CCOUNT_SPACE 0x1000 /* The size of the ccount space */
131 #define MPPE_OVHD 2 /* MPPE overhead/packet */
132 #define SANITY_MAX 1600 /* Max bogon factor we will tolerate */
135 * Key Derivation, from RFC 3078, RFC 3079.
136 * Equivalent to Get_Key() for MS-CHAP as described in RFC 3079.
138 static void get_new_key_from_sha(struct ppp_mppe_state * state, unsigned char *InterimKey)
140 struct scatterlist sg[4];
142 setup_sg(&sg[0], state->master_key, state->keylen);
143 setup_sg(&sg[1], sha_pad->sha_pad1, sizeof(sha_pad->sha_pad1));
144 setup_sg(&sg[2], state->session_key, state->keylen);
145 setup_sg(&sg[3], sha_pad->sha_pad2, sizeof(sha_pad->sha_pad2));
147 crypto_digest_digest (state->sha1, sg, 4, state->sha1_digest);
149 memcpy(InterimKey, state->sha1_digest, state->keylen);
153 * Perform the MPPE rekey algorithm, from RFC 3078, sec. 7.3.
154 * Well, not what's written there, but rather what they meant.
156 static void mppe_rekey(struct ppp_mppe_state * state, int initial_key)
158 unsigned char InterimKey[MPPE_MAX_KEY_LEN];
159 struct scatterlist sg_in[1], sg_out[1];
160 struct blkcipher_desc desc = { .tfm = state->arc4 };
162 get_new_key_from_sha(state, InterimKey);
164 crypto_blkcipher_setkey(state->arc4, InterimKey, state->keylen);
165 setup_sg(sg_in, InterimKey, state->keylen);
166 setup_sg(sg_out, state->session_key, state->keylen);
167 if (crypto_blkcipher_encrypt(&desc, sg_out, sg_in,
168 state->keylen) != 0) {
169 printk(KERN_WARNING "mppe_rekey: cipher_encrypt failed\n");
172 memcpy(state->session_key, InterimKey, state->keylen);
174 if (state->keylen == 8) {
176 state->session_key[0] = 0xd1;
177 state->session_key[1] = 0x26;
178 state->session_key[2] = 0x9e;
180 crypto_blkcipher_setkey(state->arc4, state->session_key, state->keylen);
184 * Allocate space for a (de)compressor.
186 static void *mppe_alloc(unsigned char *options, int optlen)
188 struct ppp_mppe_state *state;
189 unsigned int digestsize;
191 if (optlen != CILEN_MPPE + sizeof(state->master_key)
192 || options[0] != CI_MPPE || options[1] != CILEN_MPPE)
195 state = (struct ppp_mppe_state *) kmalloc(sizeof(*state), GFP_KERNEL);
199 memset(state, 0, sizeof(*state));
201 state->arc4 = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
202 if (IS_ERR(state->arc4)) {
207 state->sha1 = crypto_alloc_tfm("sha1", 0);
211 digestsize = crypto_tfm_alg_digestsize(state->sha1);
212 if (digestsize < MPPE_MAX_KEY_LEN)
215 state->sha1_digest = kmalloc(digestsize, GFP_KERNEL);
216 if (!state->sha1_digest)
220 memcpy(state->master_key, &options[CILEN_MPPE],
221 sizeof(state->master_key));
222 memcpy(state->session_key, state->master_key,
223 sizeof(state->master_key));
226 * We defer initial key generation until mppe_init(), as mppe_alloc()
227 * is called frequently during negotiation.
230 return (void *)state;
233 if (state->sha1_digest)
234 kfree(state->sha1_digest);
236 crypto_free_tfm(state->sha1);
238 crypto_free_blkcipher(state->arc4);
245 * Deallocate space for a (de)compressor.
247 static void mppe_free(void *arg)
249 struct ppp_mppe_state *state = (struct ppp_mppe_state *) arg;
251 if (state->sha1_digest)
252 kfree(state->sha1_digest);
254 crypto_free_tfm(state->sha1);
256 crypto_free_blkcipher(state->arc4);
262 * Initialize (de)compressor state.
265 mppe_init(void *arg, unsigned char *options, int optlen, int unit, int debug,
266 const char *debugstr)
268 struct ppp_mppe_state *state = (struct ppp_mppe_state *) arg;
269 unsigned char mppe_opts;
271 if (optlen != CILEN_MPPE
272 || options[0] != CI_MPPE || options[1] != CILEN_MPPE)
275 MPPE_CI_TO_OPTS(&options[2], mppe_opts);
276 if (mppe_opts & MPPE_OPT_128)
278 else if (mppe_opts & MPPE_OPT_40)
281 printk(KERN_WARNING "%s[%d]: unknown key length\n", debugstr,
285 if (mppe_opts & MPPE_OPT_STATEFUL)
288 /* Generate the initial session key. */
289 mppe_rekey(state, 1);
293 char mkey[sizeof(state->master_key) * 2 + 1];
294 char skey[sizeof(state->session_key) * 2 + 1];
296 printk(KERN_DEBUG "%s[%d]: initialized with %d-bit %s mode\n",
297 debugstr, unit, (state->keylen == 16) ? 128 : 40,
298 (state->stateful) ? "stateful" : "stateless");
300 for (i = 0; i < sizeof(state->master_key); i++)
301 sprintf(mkey + i * 2, "%02x", state->master_key[i]);
302 for (i = 0; i < sizeof(state->session_key); i++)
303 sprintf(skey + i * 2, "%02x", state->session_key[i]);
305 "%s[%d]: keys: master: %s initial session: %s\n",
306 debugstr, unit, mkey, skey);
310 * Initialize the coherency count. The initial value is not specified
311 * in RFC 3078, but we can make a reasonable assumption that it will
312 * start at 0. Setting it to the max here makes the comp/decomp code
313 * do the right thing (determined through experiment).
315 state->ccount = MPPE_CCOUNT_SPACE - 1;
318 * Note that even though we have initialized the key table, we don't
319 * set the FLUSHED bit. This is contrary to RFC 3078, sec. 3.1.
321 state->bits = MPPE_BIT_ENCRYPTED;
324 state->debug = debug;
330 mppe_comp_init(void *arg, unsigned char *options, int optlen, int unit,
331 int hdrlen, int debug)
334 return mppe_init(arg, options, optlen, unit, debug, "mppe_comp_init");
338 * We received a CCP Reset-Request (actually, we are sending a Reset-Ack),
339 * tell the compressor to rekey. Note that we MUST NOT rekey for
340 * every CCP Reset-Request; we only rekey on the next xmit packet.
341 * We might get multiple CCP Reset-Requests if our CCP Reset-Ack is lost.
342 * So, rekeying for every CCP Reset-Request is broken as the peer will not
343 * know how many times we've rekeyed. (If we rekey and THEN get another
344 * CCP Reset-Request, we must rekey again.)
346 static void mppe_comp_reset(void *arg)
348 struct ppp_mppe_state *state = (struct ppp_mppe_state *) arg;
350 state->bits |= MPPE_BIT_FLUSHED;
354 * Compress (encrypt) a packet.
355 * It's strange to call this a compressor, since the output is always
356 * MPPE_OVHD + 2 bytes larger than the input.
359 mppe_compress(void *arg, unsigned char *ibuf, unsigned char *obuf,
360 int isize, int osize)
362 struct ppp_mppe_state *state = (struct ppp_mppe_state *) arg;
363 struct blkcipher_desc desc = { .tfm = state->arc4 };
365 struct scatterlist sg_in[1], sg_out[1];
368 * Check that the protocol is in the range we handle.
370 proto = PPP_PROTOCOL(ibuf);
371 if (proto < 0x0021 || proto > 0x00fa)
374 /* Make sure we have enough room to generate an encrypted packet. */
375 if (osize < isize + MPPE_OVHD + 2) {
376 /* Drop the packet if we should encrypt it, but can't. */
377 printk(KERN_DEBUG "mppe_compress[%d]: osize too small! "
378 "(have: %d need: %d)\n", state->unit,
379 osize, osize + MPPE_OVHD + 2);
383 osize = isize + MPPE_OVHD + 2;
386 * Copy over the PPP header and set control bits.
388 obuf[0] = PPP_ADDRESS(ibuf);
389 obuf[1] = PPP_CONTROL(ibuf);
390 obuf[2] = PPP_COMP >> 8; /* isize + MPPE_OVHD + 1 */
391 obuf[3] = PPP_COMP; /* isize + MPPE_OVHD + 2 */
394 state->ccount = (state->ccount + 1) % MPPE_CCOUNT_SPACE;
395 if (state->debug >= 7)
396 printk(KERN_DEBUG "mppe_compress[%d]: ccount %d\n", state->unit,
398 obuf[0] = state->ccount >> 8;
399 obuf[1] = state->ccount & 0xff;
401 if (!state->stateful || /* stateless mode */
402 ((state->ccount & 0xff) == 0xff) || /* "flag" packet */
403 (state->bits & MPPE_BIT_FLUSHED)) { /* CCP Reset-Request */
405 if (state->debug && state->stateful)
406 printk(KERN_DEBUG "mppe_compress[%d]: rekeying\n",
408 mppe_rekey(state, 0);
409 state->bits |= MPPE_BIT_FLUSHED;
411 obuf[0] |= state->bits;
412 state->bits &= ~MPPE_BIT_FLUSHED; /* reset for next xmit */
415 ibuf += 2; /* skip to proto field */
419 setup_sg(sg_in, ibuf, isize);
420 setup_sg(sg_out, obuf, osize);
421 if (crypto_blkcipher_encrypt(&desc, sg_out, sg_in, isize) != 0) {
422 printk(KERN_DEBUG "crypto_cypher_encrypt failed\n");
426 state->stats.unc_bytes += isize;
427 state->stats.unc_packets++;
428 state->stats.comp_bytes += osize;
429 state->stats.comp_packets++;
435 * Since every frame grows by MPPE_OVHD + 2 bytes, this is always going
436 * to look bad ... and the longer the link is up the worse it will get.
438 static void mppe_comp_stats(void *arg, struct compstat *stats)
440 struct ppp_mppe_state *state = (struct ppp_mppe_state *) arg;
442 *stats = state->stats;
446 mppe_decomp_init(void *arg, unsigned char *options, int optlen, int unit,
447 int hdrlen, int mru, int debug)
450 return mppe_init(arg, options, optlen, unit, debug, "mppe_decomp_init");
454 * We received a CCP Reset-Ack. Just ignore it.
456 static void mppe_decomp_reset(void *arg)
463 * Decompress (decrypt) an MPPE packet.
466 mppe_decompress(void *arg, unsigned char *ibuf, int isize, unsigned char *obuf,
469 struct ppp_mppe_state *state = (struct ppp_mppe_state *) arg;
470 struct blkcipher_desc desc = { .tfm = state->arc4 };
472 int flushed = MPPE_BITS(ibuf) & MPPE_BIT_FLUSHED;
474 struct scatterlist sg_in[1], sg_out[1];
476 if (isize <= PPP_HDRLEN + MPPE_OVHD) {
479 "mppe_decompress[%d]: short pkt (%d)\n",
485 * Make sure we have enough room to decrypt the packet.
486 * Note that for our test we only subtract 1 byte whereas in
487 * mppe_compress() we added 2 bytes (+MPPE_OVHD);
488 * this is to account for possible PFC.
490 if (osize < isize - MPPE_OVHD - 1) {
491 printk(KERN_DEBUG "mppe_decompress[%d]: osize too small! "
492 "(have: %d need: %d)\n", state->unit,
493 osize, isize - MPPE_OVHD - 1);
496 osize = isize - MPPE_OVHD - 2; /* assume no PFC */
498 ccount = MPPE_CCOUNT(ibuf);
499 if (state->debug >= 7)
500 printk(KERN_DEBUG "mppe_decompress[%d]: ccount %d\n",
501 state->unit, ccount);
503 /* sanity checks -- terminate with extreme prejudice */
504 if (!(MPPE_BITS(ibuf) & MPPE_BIT_ENCRYPTED)) {
506 "mppe_decompress[%d]: ENCRYPTED bit not set!\n",
508 state->sanity_errors += 100;
511 if (!state->stateful && !flushed) {
512 printk(KERN_DEBUG "mppe_decompress[%d]: FLUSHED bit not set in "
513 "stateless mode!\n", state->unit);
514 state->sanity_errors += 100;
517 if (state->stateful && ((ccount & 0xff) == 0xff) && !flushed) {
518 printk(KERN_DEBUG "mppe_decompress[%d]: FLUSHED bit not set on "
519 "flag packet!\n", state->unit);
520 state->sanity_errors += 100;
525 if (state->sanity_errors < SANITY_MAX)
529 * Take LCP down if the peer is sending too many bogons.
530 * We don't want to do this for a single or just a few
531 * instances since it could just be due to packet corruption.
533 return DECOMP_FATALERROR;
537 * Check the coherency count.
540 if (!state->stateful) {
541 /* RFC 3078, sec 8.1. Rekey for every packet. */
542 while (state->ccount != ccount) {
543 mppe_rekey(state, 0);
544 state->ccount = (state->ccount + 1) % MPPE_CCOUNT_SPACE;
547 /* RFC 3078, sec 8.2. */
548 if (!state->discard) {
550 state->ccount = (state->ccount + 1) % MPPE_CCOUNT_SPACE;
551 if (ccount != state->ccount) {
553 * (ccount > state->ccount)
554 * Packet loss detected, enter the discard state.
555 * Signal the peer to rekey (by sending a CCP Reset-Request).
563 /* ccp.c will be silent (no additional CCP Reset-Requests). */
566 /* Rekey for every missed "flag" packet. */
567 while ((ccount & ~0xff) !=
568 (state->ccount & ~0xff)) {
569 mppe_rekey(state, 0);
572 256) % MPPE_CCOUNT_SPACE;
577 state->ccount = ccount;
579 * Another problem with RFC 3078 here. It implies that the
580 * peer need not send a Reset-Ack packet. But RFC 1962
581 * requires it. Hopefully, M$ does send a Reset-Ack; even
582 * though it isn't required for MPPE synchronization, it is
583 * required to reset CCP state.
588 mppe_rekey(state, 0);
592 * Fill in the first part of the PPP header. The protocol field
593 * comes from the decrypted data.
595 obuf[0] = PPP_ADDRESS(ibuf); /* +1 */
596 obuf[1] = PPP_CONTROL(ibuf); /* +1 */
598 ibuf += PPP_HDRLEN + MPPE_OVHD;
599 isize -= PPP_HDRLEN + MPPE_OVHD; /* -6 */
600 /* net osize: isize-4 */
603 * Decrypt the first byte in order to check if it is
604 * a compressed or uncompressed protocol field.
606 setup_sg(sg_in, ibuf, 1);
607 setup_sg(sg_out, obuf, 1);
608 if (crypto_blkcipher_decrypt(&desc, sg_out, sg_in, 1) != 0) {
609 printk(KERN_DEBUG "crypto_cypher_decrypt failed\n");
614 * Do PFC decompression.
615 * This would be nicer if we were given the actual sk_buff
616 * instead of a char *.
618 if ((obuf[0] & 0x01) != 0) {
625 /* And finally, decrypt the rest of the packet. */
626 setup_sg(sg_in, ibuf + 1, isize - 1);
627 setup_sg(sg_out, obuf + 1, osize - 1);
628 if (crypto_blkcipher_decrypt(&desc, sg_out, sg_in, isize - 1)) {
629 printk(KERN_DEBUG "crypto_cypher_decrypt failed\n");
633 state->stats.unc_bytes += osize;
634 state->stats.unc_packets++;
635 state->stats.comp_bytes += isize;
636 state->stats.comp_packets++;
638 /* good packet credit */
639 state->sanity_errors >>= 1;
645 * Incompressible data has arrived (this should never happen!).
646 * We should probably drop the link if the protocol is in the range
647 * of what should be encrypted. At the least, we should drop this
648 * packet. (How to do this?)
650 static void mppe_incomp(void *arg, unsigned char *ibuf, int icnt)
652 struct ppp_mppe_state *state = (struct ppp_mppe_state *) arg;
655 (PPP_PROTOCOL(ibuf) >= 0x0021 && PPP_PROTOCOL(ibuf) <= 0x00fa))
657 "mppe_incomp[%d]: incompressible (unencrypted) data! "
658 "(proto %04x)\n", state->unit, PPP_PROTOCOL(ibuf));
660 state->stats.inc_bytes += icnt;
661 state->stats.inc_packets++;
662 state->stats.unc_bytes += icnt;
663 state->stats.unc_packets++;
666 /*************************************************************
667 * Module interface table
668 *************************************************************/
671 * Procedures exported to if_ppp.c.
673 static struct compressor ppp_mppe = {
674 .compress_proto = CI_MPPE,
675 .comp_alloc = mppe_alloc,
676 .comp_free = mppe_free,
677 .comp_init = mppe_comp_init,
678 .comp_reset = mppe_comp_reset,
679 .compress = mppe_compress,
680 .comp_stat = mppe_comp_stats,
681 .decomp_alloc = mppe_alloc,
682 .decomp_free = mppe_free,
683 .decomp_init = mppe_decomp_init,
684 .decomp_reset = mppe_decomp_reset,
685 .decompress = mppe_decompress,
686 .incomp = mppe_incomp,
687 .decomp_stat = mppe_comp_stats,
688 .owner = THIS_MODULE,
689 .comp_extra = MPPE_PAD,
695 * Prior to allowing load, try to load the arc4 and sha1 crypto
696 * libraries. The actual use will be allocated later, but
697 * this way the module will fail to insmod if they aren't available.
700 static int __init ppp_mppe_init(void)
703 if (!(crypto_alg_available("ecb(arc4)", 0) &&
704 crypto_alg_available("sha1", 0)))
707 sha_pad = kmalloc(sizeof(struct sha_pad), GFP_KERNEL);
710 sha_pad_init(sha_pad);
712 answer = ppp_register_compressor(&ppp_mppe);
715 printk(KERN_INFO "PPP MPPE Compression module registered\n");
722 static void __exit ppp_mppe_cleanup(void)
724 ppp_unregister_compressor(&ppp_mppe);
728 module_init(ppp_mppe_init);
729 module_exit(ppp_mppe_cleanup);