OVMS3-idf/components/lwip/netif/ppp/mppe.c
2016-08-17 23:08:22 +08:00

418 lines
12 KiB
C
Executable file

/*
* mppe.c - interface MPPE to the PPP code.
*
* 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.
*
* 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 "lwip/opt.h"
#if PPP_SUPPORT && MPPE_SUPPORT /* don't build if not configured for use in lwipopts.h */
#include <string.h>
#include "lwip/err.h"
#include "netif/ppp/ppp_impl.h"
#include "netif/ppp/ccp.h"
#include "netif/ppp/mppe.h"
#include "netif/ppp/pppdebug.h"
#if LWIP_INCLUDED_POLARSSL_SHA1
#include "netif/ppp/polarssl/sha1.h"
#else
#include "polarssl/sha1.h"
#endif
#if LWIP_INCLUDED_POLARSSL_ARC4
#include "netif/ppp/polarssl/arc4.h"
#else
#include "polarssl/arc4.h"
#endif
#define SHA1_SIGNATURE_SIZE 20
/* 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)[0] & 0xf0)
#define MPPE_CCOUNT(p) ((((p)[0] & 0x0f) << 8) + (p)[1])
#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 */
/*
* 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(ppp_mppe_state * state, int initial_key)
{
sha1_context sha1_ctx;
u8_t sha1_digest[SHA1_SIGNATURE_SIZE];
/*
* Key Derivation, from RFC 3078, RFC 3079.
* Equivalent to Get_Key() for MS-CHAP as described in RFC 3079.
*/
sha1_starts(&sha1_ctx);
sha1_update(&sha1_ctx, state->master_key, state->keylen);
sha1_update(&sha1_ctx, mppe_sha1_pad1, SHA1_PAD_SIZE);
sha1_update(&sha1_ctx, state->session_key, state->keylen);
sha1_update(&sha1_ctx, mppe_sha1_pad2, SHA1_PAD_SIZE);
sha1_finish(&sha1_ctx, sha1_digest);
MEMCPY(state->session_key, sha1_digest, state->keylen);
if (!initial_key) {
arc4_setup(&state->arc4, sha1_digest, state->keylen);
arc4_crypt(&state->arc4, state->session_key, 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_setup(&state->arc4, state->session_key, state->keylen);
}
/*
* Set key, used by MSCHAP before mppe_init() is actually called by CCP so we
* don't have to keep multiple copies of keys.
*/
void mppe_set_key(ppp_pcb *pcb, ppp_mppe_state *state, u8_t *key) {
LWIP_UNUSED_ARG(pcb);
MEMCPY(state->master_key, key, MPPE_MAX_KEY_LEN);
}
/*
* Initialize (de)compressor state.
*/
void
mppe_init(ppp_pcb *pcb, ppp_mppe_state *state, u8_t options)
{
#if PPP_DEBUG
const u8_t *debugstr = (const u8_t*)"mppe_comp_init";
if (&pcb->mppe_decomp == state) {
debugstr = (const u8_t*)"mppe_decomp_init";
}
#endif /* PPP_DEBUG */
/* Save keys. */
MEMCPY(state->session_key, state->master_key, sizeof(state->master_key));
if (options & MPPE_OPT_128)
state->keylen = 16;
else if (options & MPPE_OPT_40)
state->keylen = 8;
else {
PPPDEBUG(LOG_DEBUG, ("%s[%d]: unknown key length\n", debugstr,
pcb->netif->num));
lcp_close(pcb, "MPPE required but peer negotiation failed");
return;
}
if (options & MPPE_OPT_STATEFUL)
state->stateful = 1;
/* Generate the initial session key. */
mppe_rekey(state, 1);
#if PPP_DEBUG
{
int i;
char mkey[sizeof(state->master_key) * 2 + 1];
char skey[sizeof(state->session_key) * 2 + 1];
PPPDEBUG(LOG_DEBUG, ("%s[%d]: initialized with %d-bit %s mode\n",
debugstr, pcb->netif->num, (state->keylen == 16) ? 128 : 40,
(state->stateful) ? "stateful" : "stateless"));
for (i = 0; i < (int)sizeof(state->master_key); i++)
sprintf(mkey + i * 2, "%02x", state->master_key[i]);
for (i = 0; i < (int)sizeof(state->session_key); i++)
sprintf(skey + i * 2, "%02x", state->session_key[i]);
PPPDEBUG(LOG_DEBUG,
("%s[%d]: keys: master: %s initial session: %s\n",
debugstr, pcb->netif->num, mkey, skey));
}
#endif /* PPP_DEBUG */
/*
* 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;
}
/*
* 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.)
*/
void mppe_comp_reset(ppp_pcb *pcb, ppp_mppe_state *state)
{
LWIP_UNUSED_ARG(pcb);
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.
*/
err_t
mppe_compress(ppp_pcb *pcb, ppp_mppe_state *state, struct pbuf **pb, u16_t protocol)
{
struct pbuf *n, *np;
u8_t *pl;
err_t err;
LWIP_UNUSED_ARG(pcb);
/* TCP stack requires that we don't change the packet payload, therefore we copy
* the whole packet before encryption.
*/
np = pbuf_alloc(PBUF_RAW, MPPE_OVHD + sizeof(protocol) + (*pb)->tot_len, PBUF_POOL);
if (!np) {
return ERR_MEM;
}
/* Hide MPPE header + protocol */
pbuf_header(np, -(s16_t)(MPPE_OVHD + sizeof(protocol)));
if ((err = pbuf_copy(np, *pb)) != ERR_OK) {
pbuf_free(np);
return err;
}
/* Reveal MPPE header + protocol */
pbuf_header(np, (s16_t)(MPPE_OVHD + sizeof(protocol)));
*pb = np;
pl = (u8_t*)np->payload;
state->ccount = (state->ccount + 1) % MPPE_CCOUNT_SPACE;
PPPDEBUG(LOG_DEBUG, ("mppe_compress[%d]: ccount %d\n", pcb->netif->num, state->ccount));
/* FIXME: use PUT* macros */
pl[0] = state->ccount>>8;
pl[1] = state->ccount;
if (!state->stateful || /* stateless mode */
((state->ccount & 0xff) == 0xff) || /* "flag" packet */
(state->bits & MPPE_BIT_FLUSHED)) { /* CCP Reset-Request */
/* We must rekey */
if (state->stateful) {
PPPDEBUG(LOG_DEBUG, ("mppe_compress[%d]: rekeying\n", pcb->netif->num));
}
mppe_rekey(state, 0);
state->bits |= MPPE_BIT_FLUSHED;
}
pl[0] |= state->bits;
state->bits &= ~MPPE_BIT_FLUSHED; /* reset for next xmit */
pl += MPPE_OVHD;
/* Add protocol */
/* FIXME: add PFC support */
pl[0] = protocol >> 8;
pl[1] = protocol;
/* Hide MPPE header */
pbuf_header(np, -(s16_t)MPPE_OVHD);
/* Encrypt packet */
for (n = np; n != NULL; n = n->next) {
arc4_crypt(&state->arc4, (u8_t*)n->payload, n->len);
if (n->tot_len == n->len) {
break;
}
}
/* Reveal MPPE header */
pbuf_header(np, (s16_t)MPPE_OVHD);
return ERR_OK;
}
/*
* We received a CCP Reset-Ack. Just ignore it.
*/
void mppe_decomp_reset(ppp_pcb *pcb, ppp_mppe_state *state)
{
LWIP_UNUSED_ARG(pcb);
LWIP_UNUSED_ARG(state);
return;
}
/*
* Decompress (decrypt) an MPPE packet.
*/
err_t
mppe_decompress(ppp_pcb *pcb, ppp_mppe_state *state, struct pbuf **pb)
{
struct pbuf *n0 = *pb, *n;
u8_t *pl;
u16_t ccount;
u8_t flushed;
/* MPPE Header */
if (n0->len < MPPE_OVHD) {
PPPDEBUG(LOG_DEBUG,
("mppe_decompress[%d]: short pkt (%d)\n",
pcb->netif->num, n0->len));
state->sanity_errors += 100;
goto sanity_error;
}
pl = (u8_t*)n0->payload;
flushed = MPPE_BITS(pl) & MPPE_BIT_FLUSHED;
ccount = MPPE_CCOUNT(pl);
PPPDEBUG(LOG_DEBUG, ("mppe_decompress[%d]: ccount %d\n",
pcb->netif->num, ccount));
/* sanity checks -- terminate with extreme prejudice */
if (!(MPPE_BITS(pl) & MPPE_BIT_ENCRYPTED)) {
PPPDEBUG(LOG_DEBUG,
("mppe_decompress[%d]: ENCRYPTED bit not set!\n",
pcb->netif->num));
state->sanity_errors += 100;
goto sanity_error;
}
if (!state->stateful && !flushed) {
PPPDEBUG(LOG_DEBUG, ("mppe_decompress[%d]: FLUSHED bit not set in "
"stateless mode!\n", pcb->netif->num));
state->sanity_errors += 100;
goto sanity_error;
}
if (state->stateful && ((ccount & 0xff) == 0xff) && !flushed) {
PPPDEBUG(LOG_DEBUG, ("mppe_decompress[%d]: FLUSHED bit not set on "
"flag packet!\n", pcb->netif->num));
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;
ccp_resetrequest(pcb);
return ERR_BUF;
}
} else {
/* discard state */
if (!flushed) {
/* ccp.c will be silent (no additional CCP Reset-Requests). */
return ERR_BUF;
} 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);
}
/* Hide MPPE header */
pbuf_header(n0, -(s16_t)(MPPE_OVHD));
/* Decrypt the packet. */
for (n = n0; n != NULL; n = n->next) {
arc4_crypt(&state->arc4, (u8_t*)n->payload, n->len);
if (n->tot_len == n->len) {
break;
}
}
/* good packet credit */
state->sanity_errors >>= 1;
return ERR_OK;
sanity_error:
if (state->sanity_errors >= SANITY_MAX) {
/*
* 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.
*/
lcp_close(pcb, "Too many MPPE errors");
}
return ERR_BUF;
}
#endif /* PPP_SUPPORT && MPPE_SUPPORT */