diff options
Diffstat (limited to 'lwip/src/netif/ppp/mppe.c')
-rw-r--r-- | lwip/src/netif/ppp/mppe.c | 412 |
1 files changed, 412 insertions, 0 deletions
diff --git a/lwip/src/netif/ppp/mppe.c b/lwip/src/netif/ppp/mppe.c new file mode 100644 index 0000000..4cca89d --- /dev/null +++ b/lwip/src/netif/ppp/mppe.c @@ -0,0 +1,412 @@ +/* + * 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 "netif/ppp/ppp_opts.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" +#include "netif/ppp/pppcrypt.h" + +#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) +{ + lwip_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. + */ + lwip_sha1_init(&sha1_ctx); + lwip_sha1_starts(&sha1_ctx); + lwip_sha1_update(&sha1_ctx, state->master_key, state->keylen); + lwip_sha1_update(&sha1_ctx, mppe_sha1_pad1, SHA1_PAD_SIZE); + lwip_sha1_update(&sha1_ctx, state->session_key, state->keylen); + lwip_sha1_update(&sha1_ctx, mppe_sha1_pad2, SHA1_PAD_SIZE); + lwip_sha1_finish(&sha1_ctx, sha1_digest); + lwip_sha1_free(&sha1_ctx); + MEMCPY(state->session_key, sha1_digest, state->keylen); + + if (!initial_key) { + lwip_arc4_init(&state->arc4); + lwip_arc4_setup(&state->arc4, sha1_digest, state->keylen); + lwip_arc4_crypt(&state->arc4, state->session_key, state->keylen); + lwip_arc4_free(&state->arc4); + } + if (state->keylen == 8) { + /* See RFC 3078 */ + state->session_key[0] = 0xd1; + state->session_key[1] = 0x26; + state->session_key[2] = 0x9e; + } + lwip_arc4_init(&state->arc4); + lwip_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_RAM); + if (!np) { + return ERR_MEM; + } + + /* Hide MPPE header + protocol */ + pbuf_remove_header(np, MPPE_OVHD + sizeof(protocol)); + + if ((err = pbuf_copy(np, *pb)) != ERR_OK) { + pbuf_free(np); + return err; + } + + /* Reveal MPPE header + protocol */ + pbuf_add_header(np, 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_remove_header(np, MPPE_OVHD); + + /* Encrypt packet */ + for (n = np; n != NULL; n = n->next) { + lwip_arc4_crypt(&state->arc4, (u8_t*)n->payload, n->len); + if (n->tot_len == n->len) { + break; + } + } + + /* Reveal MPPE header */ + pbuf_add_header(np, 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_remove_header(n0, MPPE_OVHD); + + /* Decrypt the packet. */ + for (n = n0; n != NULL; n = n->next) { + lwip_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 */ |