[457] | 1 | /*
|
---|
| 2 | * mppe.c - interface MPPE to the PPP code.
|
---|
| 3 | *
|
---|
| 4 | * By Frank Cusack <fcusack@fcusack.com>.
|
---|
| 5 | * Copyright (c) 2002,2003,2004 Google, Inc.
|
---|
| 6 | * All rights reserved.
|
---|
| 7 | *
|
---|
| 8 | * License:
|
---|
| 9 | * Permission to use, copy, modify, and distribute this software and its
|
---|
| 10 | * documentation is hereby granted, provided that the above copyright
|
---|
| 11 | * notice appears in all copies. This software is provided without any
|
---|
| 12 | * warranty, express or implied.
|
---|
| 13 | *
|
---|
| 14 | * Changelog:
|
---|
| 15 | * 08/12/05 - Matt Domsch <Matt_Domsch@dell.com>
|
---|
| 16 | * Only need extra skb padding on transmit, not receive.
|
---|
| 17 | * 06/18/04 - Matt Domsch <Matt_Domsch@dell.com>, Oleg Makarenko <mole@quadra.ru>
|
---|
| 18 | * Use Linux kernel 2.6 arc4 and sha1 routines rather than
|
---|
| 19 | * providing our own.
|
---|
| 20 | * 2/15/04 - TS: added #include <version.h> and testing for Kernel
|
---|
| 21 | * version before using
|
---|
| 22 | * MOD_DEC_USAGE_COUNT/MOD_INC_USAGE_COUNT which are
|
---|
| 23 | * deprecated in 2.6
|
---|
| 24 | */
|
---|
| 25 |
|
---|
| 26 | #include "netif/ppp/ppp_opts.h"
|
---|
| 27 | #if PPP_SUPPORT && MPPE_SUPPORT /* don't build if not configured for use in lwipopts.h */
|
---|
| 28 |
|
---|
| 29 | #include <string.h>
|
---|
| 30 |
|
---|
| 31 | #include "lwip/err.h"
|
---|
| 32 |
|
---|
| 33 | #include "netif/ppp/ppp_impl.h"
|
---|
| 34 | #include "netif/ppp/ccp.h"
|
---|
| 35 | #include "netif/ppp/mppe.h"
|
---|
| 36 | #include "netif/ppp/pppdebug.h"
|
---|
| 37 | #include "netif/ppp/pppcrypt.h"
|
---|
| 38 |
|
---|
| 39 | #define SHA1_SIGNATURE_SIZE 20
|
---|
| 40 |
|
---|
| 41 | /* ppp_mppe_state.bits definitions */
|
---|
| 42 | #define MPPE_BIT_A 0x80 /* Encryption table were (re)inititalized */
|
---|
| 43 | #define MPPE_BIT_B 0x40 /* MPPC only (not implemented) */
|
---|
| 44 | #define MPPE_BIT_C 0x20 /* MPPC only (not implemented) */
|
---|
| 45 | #define MPPE_BIT_D 0x10 /* This is an encrypted frame */
|
---|
| 46 |
|
---|
| 47 | #define MPPE_BIT_FLUSHED MPPE_BIT_A
|
---|
| 48 | #define MPPE_BIT_ENCRYPTED MPPE_BIT_D
|
---|
| 49 |
|
---|
| 50 | #define MPPE_BITS(p) ((p)[0] & 0xf0)
|
---|
| 51 | #define MPPE_CCOUNT(p) ((((p)[0] & 0x0f) << 8) + (p)[1])
|
---|
| 52 | #define MPPE_CCOUNT_SPACE 0x1000 /* The size of the ccount space */
|
---|
| 53 |
|
---|
| 54 | #define MPPE_OVHD 2 /* MPPE overhead/packet */
|
---|
| 55 | #define SANITY_MAX 1600 /* Max bogon factor we will tolerate */
|
---|
| 56 |
|
---|
| 57 | /*
|
---|
| 58 | * Perform the MPPE rekey algorithm, from RFC 3078, sec. 7.3.
|
---|
| 59 | * Well, not what's written there, but rather what they meant.
|
---|
| 60 | */
|
---|
| 61 | static void mppe_rekey(ppp_mppe_state * state, int initial_key)
|
---|
| 62 | {
|
---|
| 63 | lwip_sha1_context sha1_ctx;
|
---|
| 64 | u8_t sha1_digest[SHA1_SIGNATURE_SIZE];
|
---|
| 65 |
|
---|
| 66 | /*
|
---|
| 67 | * Key Derivation, from RFC 3078, RFC 3079.
|
---|
| 68 | * Equivalent to Get_Key() for MS-CHAP as described in RFC 3079.
|
---|
| 69 | */
|
---|
| 70 | lwip_sha1_init(&sha1_ctx);
|
---|
| 71 | lwip_sha1_starts(&sha1_ctx);
|
---|
| 72 | lwip_sha1_update(&sha1_ctx, state->master_key, state->keylen);
|
---|
| 73 | lwip_sha1_update(&sha1_ctx, mppe_sha1_pad1, SHA1_PAD_SIZE);
|
---|
| 74 | lwip_sha1_update(&sha1_ctx, state->session_key, state->keylen);
|
---|
| 75 | lwip_sha1_update(&sha1_ctx, mppe_sha1_pad2, SHA1_PAD_SIZE);
|
---|
| 76 | lwip_sha1_finish(&sha1_ctx, sha1_digest);
|
---|
| 77 | lwip_sha1_free(&sha1_ctx);
|
---|
| 78 | MEMCPY(state->session_key, sha1_digest, state->keylen);
|
---|
| 79 |
|
---|
| 80 | if (!initial_key) {
|
---|
| 81 | lwip_arc4_init(&state->arc4);
|
---|
| 82 | lwip_arc4_setup(&state->arc4, sha1_digest, state->keylen);
|
---|
| 83 | lwip_arc4_crypt(&state->arc4, state->session_key, state->keylen);
|
---|
| 84 | lwip_arc4_free(&state->arc4);
|
---|
| 85 | }
|
---|
| 86 | if (state->keylen == 8) {
|
---|
| 87 | /* See RFC 3078 */
|
---|
| 88 | state->session_key[0] = 0xd1;
|
---|
| 89 | state->session_key[1] = 0x26;
|
---|
| 90 | state->session_key[2] = 0x9e;
|
---|
| 91 | }
|
---|
| 92 | lwip_arc4_init(&state->arc4);
|
---|
| 93 | lwip_arc4_setup(&state->arc4, state->session_key, state->keylen);
|
---|
| 94 | }
|
---|
| 95 |
|
---|
| 96 | /*
|
---|
| 97 | * Set key, used by MSCHAP before mppe_init() is actually called by CCP so we
|
---|
| 98 | * don't have to keep multiple copies of keys.
|
---|
| 99 | */
|
---|
| 100 | void mppe_set_key(ppp_pcb *pcb, ppp_mppe_state *state, u8_t *key) {
|
---|
| 101 | LWIP_UNUSED_ARG(pcb);
|
---|
| 102 | MEMCPY(state->master_key, key, MPPE_MAX_KEY_LEN);
|
---|
| 103 | }
|
---|
| 104 |
|
---|
| 105 | /*
|
---|
| 106 | * Initialize (de)compressor state.
|
---|
| 107 | */
|
---|
| 108 | void
|
---|
| 109 | mppe_init(ppp_pcb *pcb, ppp_mppe_state *state, u8_t options)
|
---|
| 110 | {
|
---|
| 111 | #if PPP_DEBUG
|
---|
| 112 | const u8_t *debugstr = (const u8_t*)"mppe_comp_init";
|
---|
| 113 | if (&pcb->mppe_decomp == state) {
|
---|
| 114 | debugstr = (const u8_t*)"mppe_decomp_init";
|
---|
| 115 | }
|
---|
| 116 | #endif /* PPP_DEBUG */
|
---|
| 117 |
|
---|
| 118 | /* Save keys. */
|
---|
| 119 | MEMCPY(state->session_key, state->master_key, sizeof(state->master_key));
|
---|
| 120 |
|
---|
| 121 | if (options & MPPE_OPT_128)
|
---|
| 122 | state->keylen = 16;
|
---|
| 123 | else if (options & MPPE_OPT_40)
|
---|
| 124 | state->keylen = 8;
|
---|
| 125 | else {
|
---|
| 126 | PPPDEBUG(LOG_DEBUG, ("%s[%d]: unknown key length\n", debugstr,
|
---|
| 127 | pcb->netif->num));
|
---|
| 128 | lcp_close(pcb, "MPPE required but peer negotiation failed");
|
---|
| 129 | return;
|
---|
| 130 | }
|
---|
| 131 | if (options & MPPE_OPT_STATEFUL)
|
---|
| 132 | state->stateful = 1;
|
---|
| 133 |
|
---|
| 134 | /* Generate the initial session key. */
|
---|
| 135 | mppe_rekey(state, 1);
|
---|
| 136 |
|
---|
| 137 | #if PPP_DEBUG
|
---|
| 138 | {
|
---|
| 139 | int i;
|
---|
| 140 | char mkey[sizeof(state->master_key) * 2 + 1];
|
---|
| 141 | char skey[sizeof(state->session_key) * 2 + 1];
|
---|
| 142 |
|
---|
| 143 | PPPDEBUG(LOG_DEBUG, ("%s[%d]: initialized with %d-bit %s mode\n",
|
---|
| 144 | debugstr, pcb->netif->num, (state->keylen == 16) ? 128 : 40,
|
---|
| 145 | (state->stateful) ? "stateful" : "stateless"));
|
---|
| 146 |
|
---|
| 147 | for (i = 0; i < (int)sizeof(state->master_key); i++)
|
---|
| 148 | sprintf(mkey + i * 2, "%02x", state->master_key[i]);
|
---|
| 149 | for (i = 0; i < (int)sizeof(state->session_key); i++)
|
---|
| 150 | sprintf(skey + i * 2, "%02x", state->session_key[i]);
|
---|
| 151 | PPPDEBUG(LOG_DEBUG,
|
---|
| 152 | ("%s[%d]: keys: master: %s initial session: %s\n",
|
---|
| 153 | debugstr, pcb->netif->num, mkey, skey));
|
---|
| 154 | }
|
---|
| 155 | #endif /* PPP_DEBUG */
|
---|
| 156 |
|
---|
| 157 | /*
|
---|
| 158 | * Initialize the coherency count. The initial value is not specified
|
---|
| 159 | * in RFC 3078, but we can make a reasonable assumption that it will
|
---|
| 160 | * start at 0. Setting it to the max here makes the comp/decomp code
|
---|
| 161 | * do the right thing (determined through experiment).
|
---|
| 162 | */
|
---|
| 163 | state->ccount = MPPE_CCOUNT_SPACE - 1;
|
---|
| 164 |
|
---|
| 165 | /*
|
---|
| 166 | * Note that even though we have initialized the key table, we don't
|
---|
| 167 | * set the FLUSHED bit. This is contrary to RFC 3078, sec. 3.1.
|
---|
| 168 | */
|
---|
| 169 | state->bits = MPPE_BIT_ENCRYPTED;
|
---|
| 170 | }
|
---|
| 171 |
|
---|
| 172 | /*
|
---|
| 173 | * We received a CCP Reset-Request (actually, we are sending a Reset-Ack),
|
---|
| 174 | * tell the compressor to rekey. Note that we MUST NOT rekey for
|
---|
| 175 | * every CCP Reset-Request; we only rekey on the next xmit packet.
|
---|
| 176 | * We might get multiple CCP Reset-Requests if our CCP Reset-Ack is lost.
|
---|
| 177 | * So, rekeying for every CCP Reset-Request is broken as the peer will not
|
---|
| 178 | * know how many times we've rekeyed. (If we rekey and THEN get another
|
---|
| 179 | * CCP Reset-Request, we must rekey again.)
|
---|
| 180 | */
|
---|
| 181 | void mppe_comp_reset(ppp_pcb *pcb, ppp_mppe_state *state)
|
---|
| 182 | {
|
---|
| 183 | LWIP_UNUSED_ARG(pcb);
|
---|
| 184 | state->bits |= MPPE_BIT_FLUSHED;
|
---|
| 185 | }
|
---|
| 186 |
|
---|
| 187 | /*
|
---|
| 188 | * Compress (encrypt) a packet.
|
---|
| 189 | * It's strange to call this a compressor, since the output is always
|
---|
| 190 | * MPPE_OVHD + 2 bytes larger than the input.
|
---|
| 191 | */
|
---|
| 192 | err_t
|
---|
| 193 | mppe_compress(ppp_pcb *pcb, ppp_mppe_state *state, struct pbuf **pb, u16_t protocol)
|
---|
| 194 | {
|
---|
| 195 | struct pbuf *n, *np;
|
---|
| 196 | u8_t *pl;
|
---|
| 197 | err_t err;
|
---|
| 198 |
|
---|
| 199 | LWIP_UNUSED_ARG(pcb);
|
---|
| 200 |
|
---|
| 201 | /* TCP stack requires that we don't change the packet payload, therefore we copy
|
---|
| 202 | * the whole packet before encryption.
|
---|
| 203 | */
|
---|
| 204 | np = pbuf_alloc(PBUF_RAW, MPPE_OVHD + sizeof(protocol) + (*pb)->tot_len, PBUF_RAM);
|
---|
| 205 | if (!np) {
|
---|
| 206 | return ERR_MEM;
|
---|
| 207 | }
|
---|
| 208 |
|
---|
| 209 | /* Hide MPPE header + protocol */
|
---|
| 210 | pbuf_remove_header(np, MPPE_OVHD + sizeof(protocol));
|
---|
| 211 |
|
---|
| 212 | if ((err = pbuf_copy(np, *pb)) != ERR_OK) {
|
---|
| 213 | pbuf_free(np);
|
---|
| 214 | return err;
|
---|
| 215 | }
|
---|
| 216 |
|
---|
| 217 | /* Reveal MPPE header + protocol */
|
---|
| 218 | pbuf_add_header(np, MPPE_OVHD + sizeof(protocol));
|
---|
| 219 |
|
---|
| 220 | *pb = np;
|
---|
| 221 | pl = (u8_t*)np->payload;
|
---|
| 222 |
|
---|
| 223 | state->ccount = (state->ccount + 1) % MPPE_CCOUNT_SPACE;
|
---|
| 224 | PPPDEBUG(LOG_DEBUG, ("mppe_compress[%d]: ccount %d\n", pcb->netif->num, state->ccount));
|
---|
| 225 | /* FIXME: use PUT* macros */
|
---|
| 226 | pl[0] = state->ccount>>8;
|
---|
| 227 | pl[1] = state->ccount;
|
---|
| 228 |
|
---|
| 229 | if (!state->stateful || /* stateless mode */
|
---|
| 230 | ((state->ccount & 0xff) == 0xff) || /* "flag" packet */
|
---|
| 231 | (state->bits & MPPE_BIT_FLUSHED)) { /* CCP Reset-Request */
|
---|
| 232 | /* We must rekey */
|
---|
| 233 | if (state->stateful) {
|
---|
| 234 | PPPDEBUG(LOG_DEBUG, ("mppe_compress[%d]: rekeying\n", pcb->netif->num));
|
---|
| 235 | }
|
---|
| 236 | mppe_rekey(state, 0);
|
---|
| 237 | state->bits |= MPPE_BIT_FLUSHED;
|
---|
| 238 | }
|
---|
| 239 | pl[0] |= state->bits;
|
---|
| 240 | state->bits &= ~MPPE_BIT_FLUSHED; /* reset for next xmit */
|
---|
| 241 | pl += MPPE_OVHD;
|
---|
| 242 |
|
---|
| 243 | /* Add protocol */
|
---|
| 244 | /* FIXME: add PFC support */
|
---|
| 245 | pl[0] = protocol >> 8;
|
---|
| 246 | pl[1] = protocol;
|
---|
| 247 |
|
---|
| 248 | /* Hide MPPE header */
|
---|
| 249 | pbuf_remove_header(np, MPPE_OVHD);
|
---|
| 250 |
|
---|
| 251 | /* Encrypt packet */
|
---|
| 252 | for (n = np; n != NULL; n = n->next) {
|
---|
| 253 | lwip_arc4_crypt(&state->arc4, (u8_t*)n->payload, n->len);
|
---|
| 254 | if (n->tot_len == n->len) {
|
---|
| 255 | break;
|
---|
| 256 | }
|
---|
| 257 | }
|
---|
| 258 |
|
---|
| 259 | /* Reveal MPPE header */
|
---|
| 260 | pbuf_add_header(np, MPPE_OVHD);
|
---|
| 261 |
|
---|
| 262 | return ERR_OK;
|
---|
| 263 | }
|
---|
| 264 |
|
---|
| 265 | /*
|
---|
| 266 | * We received a CCP Reset-Ack. Just ignore it.
|
---|
| 267 | */
|
---|
| 268 | void mppe_decomp_reset(ppp_pcb *pcb, ppp_mppe_state *state)
|
---|
| 269 | {
|
---|
| 270 | LWIP_UNUSED_ARG(pcb);
|
---|
| 271 | LWIP_UNUSED_ARG(state);
|
---|
| 272 | return;
|
---|
| 273 | }
|
---|
| 274 |
|
---|
| 275 | /*
|
---|
| 276 | * Decompress (decrypt) an MPPE packet.
|
---|
| 277 | */
|
---|
| 278 | err_t
|
---|
| 279 | mppe_decompress(ppp_pcb *pcb, ppp_mppe_state *state, struct pbuf **pb)
|
---|
| 280 | {
|
---|
| 281 | struct pbuf *n0 = *pb, *n;
|
---|
| 282 | u8_t *pl;
|
---|
| 283 | u16_t ccount;
|
---|
| 284 | u8_t flushed;
|
---|
| 285 |
|
---|
| 286 | /* MPPE Header */
|
---|
| 287 | if (n0->len < MPPE_OVHD) {
|
---|
| 288 | PPPDEBUG(LOG_DEBUG,
|
---|
| 289 | ("mppe_decompress[%d]: short pkt (%d)\n",
|
---|
| 290 | pcb->netif->num, n0->len));
|
---|
| 291 | state->sanity_errors += 100;
|
---|
| 292 | goto sanity_error;
|
---|
| 293 | }
|
---|
| 294 |
|
---|
| 295 | pl = (u8_t*)n0->payload;
|
---|
| 296 | flushed = MPPE_BITS(pl) & MPPE_BIT_FLUSHED;
|
---|
| 297 | ccount = MPPE_CCOUNT(pl);
|
---|
| 298 | PPPDEBUG(LOG_DEBUG, ("mppe_decompress[%d]: ccount %d\n",
|
---|
| 299 | pcb->netif->num, ccount));
|
---|
| 300 |
|
---|
| 301 | /* sanity checks -- terminate with extreme prejudice */
|
---|
| 302 | if (!(MPPE_BITS(pl) & MPPE_BIT_ENCRYPTED)) {
|
---|
| 303 | PPPDEBUG(LOG_DEBUG,
|
---|
| 304 | ("mppe_decompress[%d]: ENCRYPTED bit not set!\n",
|
---|
| 305 | pcb->netif->num));
|
---|
| 306 | state->sanity_errors += 100;
|
---|
| 307 | goto sanity_error;
|
---|
| 308 | }
|
---|
| 309 | if (!state->stateful && !flushed) {
|
---|
| 310 | PPPDEBUG(LOG_DEBUG, ("mppe_decompress[%d]: FLUSHED bit not set in "
|
---|
| 311 | "stateless mode!\n", pcb->netif->num));
|
---|
| 312 | state->sanity_errors += 100;
|
---|
| 313 | goto sanity_error;
|
---|
| 314 | }
|
---|
| 315 | if (state->stateful && ((ccount & 0xff) == 0xff) && !flushed) {
|
---|
| 316 | PPPDEBUG(LOG_DEBUG, ("mppe_decompress[%d]: FLUSHED bit not set on "
|
---|
| 317 | "flag packet!\n", pcb->netif->num));
|
---|
| 318 | state->sanity_errors += 100;
|
---|
| 319 | goto sanity_error;
|
---|
| 320 | }
|
---|
| 321 |
|
---|
| 322 | /*
|
---|
| 323 | * Check the coherency count.
|
---|
| 324 | */
|
---|
| 325 |
|
---|
| 326 | if (!state->stateful) {
|
---|
| 327 | /* Discard late packet */
|
---|
| 328 | if ((ccount - state->ccount) % MPPE_CCOUNT_SPACE > MPPE_CCOUNT_SPACE / 2) {
|
---|
| 329 | state->sanity_errors++;
|
---|
| 330 | goto sanity_error;
|
---|
| 331 | }
|
---|
| 332 |
|
---|
| 333 | /* RFC 3078, sec 8.1. Rekey for every packet. */
|
---|
| 334 | while (state->ccount != ccount) {
|
---|
| 335 | mppe_rekey(state, 0);
|
---|
| 336 | state->ccount = (state->ccount + 1) % MPPE_CCOUNT_SPACE;
|
---|
| 337 | }
|
---|
| 338 | } else {
|
---|
| 339 | /* RFC 3078, sec 8.2. */
|
---|
| 340 | if (!state->discard) {
|
---|
| 341 | /* normal state */
|
---|
| 342 | state->ccount = (state->ccount + 1) % MPPE_CCOUNT_SPACE;
|
---|
| 343 | if (ccount != state->ccount) {
|
---|
| 344 | /*
|
---|
| 345 | * (ccount > state->ccount)
|
---|
| 346 | * Packet loss detected, enter the discard state.
|
---|
| 347 | * Signal the peer to rekey (by sending a CCP Reset-Request).
|
---|
| 348 | */
|
---|
| 349 | state->discard = 1;
|
---|
| 350 | ccp_resetrequest(pcb);
|
---|
| 351 | return ERR_BUF;
|
---|
| 352 | }
|
---|
| 353 | } else {
|
---|
| 354 | /* discard state */
|
---|
| 355 | if (!flushed) {
|
---|
| 356 | /* ccp.c will be silent (no additional CCP Reset-Requests). */
|
---|
| 357 | return ERR_BUF;
|
---|
| 358 | } else {
|
---|
| 359 | /* Rekey for every missed "flag" packet. */
|
---|
| 360 | while ((ccount & ~0xff) !=
|
---|
| 361 | (state->ccount & ~0xff)) {
|
---|
| 362 | mppe_rekey(state, 0);
|
---|
| 363 | state->ccount =
|
---|
| 364 | (state->ccount +
|
---|
| 365 | 256) % MPPE_CCOUNT_SPACE;
|
---|
| 366 | }
|
---|
| 367 |
|
---|
| 368 | /* reset */
|
---|
| 369 | state->discard = 0;
|
---|
| 370 | state->ccount = ccount;
|
---|
| 371 | /*
|
---|
| 372 | * Another problem with RFC 3078 here. It implies that the
|
---|
| 373 | * peer need not send a Reset-Ack packet. But RFC 1962
|
---|
| 374 | * requires it. Hopefully, M$ does send a Reset-Ack; even
|
---|
| 375 | * though it isn't required for MPPE synchronization, it is
|
---|
| 376 | * required to reset CCP state.
|
---|
| 377 | */
|
---|
| 378 | }
|
---|
| 379 | }
|
---|
| 380 | if (flushed)
|
---|
| 381 | mppe_rekey(state, 0);
|
---|
| 382 | }
|
---|
| 383 |
|
---|
| 384 | /* Hide MPPE header */
|
---|
| 385 | pbuf_remove_header(n0, MPPE_OVHD);
|
---|
| 386 |
|
---|
| 387 | /* Decrypt the packet. */
|
---|
| 388 | for (n = n0; n != NULL; n = n->next) {
|
---|
| 389 | lwip_arc4_crypt(&state->arc4, (u8_t*)n->payload, n->len);
|
---|
| 390 | if (n->tot_len == n->len) {
|
---|
| 391 | break;
|
---|
| 392 | }
|
---|
| 393 | }
|
---|
| 394 |
|
---|
| 395 | /* good packet credit */
|
---|
| 396 | state->sanity_errors >>= 1;
|
---|
| 397 |
|
---|
| 398 | return ERR_OK;
|
---|
| 399 |
|
---|
| 400 | sanity_error:
|
---|
| 401 | if (state->sanity_errors >= SANITY_MAX) {
|
---|
| 402 | /*
|
---|
| 403 | * Take LCP down if the peer is sending too many bogons.
|
---|
| 404 | * We don't want to do this for a single or just a few
|
---|
| 405 | * instances since it could just be due to packet corruption.
|
---|
| 406 | */
|
---|
| 407 | lcp_close(pcb, "Too many MPPE errors");
|
---|
| 408 | }
|
---|
| 409 | return ERR_BUF;
|
---|
| 410 | }
|
---|
| 411 |
|
---|
| 412 | #endif /* PPP_SUPPORT && MPPE_SUPPORT */
|
---|