diff options
Diffstat (limited to 'drivers/net/ppp/ppp_mppe.c')
| -rw-r--r-- | drivers/net/ppp/ppp_mppe.c | 688 |
1 files changed, 688 insertions, 0 deletions
diff --git a/drivers/net/ppp/ppp_mppe.c b/drivers/net/ppp/ppp_mppe.c new file mode 100644 index 000000000..208f6e24f --- /dev/null +++ b/drivers/net/ppp/ppp_mppe.c @@ -0,0 +1,688 @@ +/* + * 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/arc4.h> +#include <crypto/hash.h> +#include <linux/err.h> +#include <linux/fips.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"); + +#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 arc4_ctx 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) +{ + get_new_key_from_sha(state); + if (!initial_key) { + arc4_setkey(&state->arc4, state->sha1_digest, state->keylen); + arc4_crypt(&state->arc4, state->session_key, state->sha1_digest, + state->keylen); + } 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; + } + arc4_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; + struct crypto_shash *shash; + unsigned int digestsize; + + if (optlen != CILEN_MPPE + sizeof(state->master_key) || + options[0] != CI_MPPE || options[1] != CILEN_MPPE || + fips_enabled) + goto out; + + state = kzalloc(sizeof(*state), GFP_KERNEL); + if (state == NULL) + goto out; + + + 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(shash); + goto out_free; + } + state->sha1->tfm = shash; + + digestsize = crypto_shash_digestsize(shash); + 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: + kfree(state->sha1_digest); + if (state->sha1) { + crypto_free_shash(state->sha1->tfm); + kfree_sensitive(state->sha1); + } + 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) { + kfree(state->sha1_digest); + crypto_free_shash(state->sha1->tfm); + kfree_sensitive(state->sha1); + kfree_sensitive(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) { + printk(KERN_DEBUG "%s[%d]: initialized with %d-bit %s mode\n", + debugstr, unit, (state->keylen == 16) ? 128 : 40, + (state->stateful) ? "stateful" : "stateless"); + printk(KERN_DEBUG + "%s[%d]: keys: master: %*phN initial session: %*phN\n", + debugstr, unit, + (int)sizeof(state->master_key), state->master_key, + (int)sizeof(state->session_key), state->session_key); + } + + /* + * 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; + + /* + * 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); + put_unaligned_be16(PPP_COMP, obuf + 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); + put_unaligned_be16(state->ccount, obuf); + + 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; + + arc4_crypt(&state->arc4, obuf, ibuf, isize); + + 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; + + 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; + goto sanity_error; + } + if (!state->stateful && !flushed) { + printk(KERN_DEBUG "mppe_decompress[%d]: FLUSHED bit not set in " + "stateless mode!\n", state->unit); + state->sanity_errors += 100; + goto sanity_error; + } + 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; + goto sanity_error; + } + + /* + * Check the coherency count. + */ + + if (!state->stateful) { + /* Discard late packet */ + if ((ccount - state->ccount) % MPPE_CCOUNT_SPACE + > MPPE_CCOUNT_SPACE / 2) { + state->sanity_errors++; + goto sanity_error; + } + + /* 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. + */ + arc4_crypt(&state->arc4, obuf, ibuf, 1); + + /* + * 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. */ + arc4_crypt(&state->arc4, obuf + 1, ibuf + 1, isize - 1); + + 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; + +sanity_error: + 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; +} + +/* + * 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 (fips_enabled || !crypto_has_ahash("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); |