/*- * Copyright (c) 2000 Semen Ustimenko * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * $OpenBSD: mppe.c,v 1.10 2001/09/04 22:12:32 brian Exp $ */ #include #include #include #include #include #ifdef __FreeBSD__ #include #else #include #endif #include #include "defs.h" #include "mbuf.h" #include "log.h" #include "timer.h" #include "fsm.h" #include "lqr.h" #include "hdlc.h" #include "lcp.h" #include "ccp.h" #include "throughput.h" #include "layer.h" #include "link.h" #include "chap_ms.h" #include "proto.h" #include "mppe.h" #include "ua.h" /* * Documentation: * * draft-ietf-pppext-mppe-04.txt * draft-ietf-pppext-mppe-keys-02.txt */ #define MPPE_OPT_STATELESS 0x1000000 #define MPPE_OPT_COMPRESSED 0x01 #define MPPE_OPT_40BIT 0x20 #define MPPE_OPT_56BIT 0x80 #define MPPE_OPT_128BIT 0x40 #define MPPE_OPT_BITMASK 0xe0 #define MPPE_OPT_MASK (MPPE_OPT_STATELESS | MPPE_OPT_BITMASK) #define MPPE_FLUSHED 0x8000 #define MPPE_ENCRYPTED 0x1000 #define MPPE_HEADER_BITMASK 0xf000 #define MPPE_HEADER_FLAG 0x00ff #define MPPE_HEADER_FLAGMASK 0x00ff #define MPPE_HEADER_FLAGSHIFT 8 #define MPPE_HEADER_STATEFUL_KEYCHANGES 16 struct mppe_state { unsigned stateless : 1; unsigned flushnext : 1; unsigned flushrequired : 1; int cohnum; int keylen; /* 8 or 16 bytes */ int keybits; /* 40, 56 or 128 bits */ char sesskey[MPPE_KEY_LEN]; char mastkey[MPPE_KEY_LEN]; RC4_KEY rc4key; }; int MPPE_MasterKeyValid = 0; int MPPE_IsServer = 0; char MPPE_MasterKey[MPPE_KEY_LEN]; /* * The peer has missed a packet. Mark the next output frame to be FLUSHED */ static int MPPEResetOutput(void *v) { struct mppe_state *mop = (struct mppe_state *)v; if (mop->stateless) log_Printf(LogCCP, "MPPE: Unexpected output channel reset\n"); else { log_Printf(LogCCP, "MPPE: Output channel reset\n"); mop->flushnext = 1; } return 0; /* Ask FSM not to ACK */ } static void MPPEReduceSessionKey(struct mppe_state *mp) { switch(mp->keybits) { case 40: mp->sesskey[2] = 0x9e; mp->sesskey[1] = 0x26; case 56: mp->sesskey[0] = 0xd1; case 128: } } static void MPPEKeyChange(struct mppe_state *mp) { char InterimKey[MPPE_KEY_LEN]; RC4_KEY RC4Key; GetNewKeyFromSHA(mp->mastkey, mp->sesskey, mp->keylen, InterimKey); RC4_set_key(&RC4Key, mp->keylen, InterimKey); RC4(&RC4Key, mp->keylen, InterimKey, mp->sesskey); MPPEReduceSessionKey(mp); } static struct mbuf * MPPEOutput(void *v, struct ccp *ccp, struct link *l, int pri, u_short *proto, struct mbuf *mp) { struct mppe_state *mop = (struct mppe_state *)v; struct mbuf *mo; u_short nproto, prefix; int dictinit, ilen, len; char *rp; ilen = m_length(mp); dictinit = 0; log_Printf(LogDEBUG, "MPPE: Output: Proto %02x (%d bytes)\n", *proto, ilen); if (*proto < 0x21 && *proto > 0xFA) { log_Printf(LogDEBUG, "MPPE: Output: Not encrypting\n"); ccp->compout += ilen; ccp->uncompout += ilen; return mp; } log_DumpBp(LogDEBUG, "MPPE: Output: Encrypt packet:", mp); /* Get mbuf for prefixes */ mo = m_get(4, MB_CCPOUT); mo->m_next = mp; rp = MBUF_CTOP(mo); prefix = MPPE_ENCRYPTED | mop->cohnum; if (mop->stateless || (mop->cohnum & MPPE_HEADER_FLAGMASK) == MPPE_HEADER_FLAG) { /* Change our key */ log_Printf(LogDEBUG, "MPPEOutput: Key changed [%d]\n", mop->cohnum); MPPEKeyChange(mop); dictinit = 1; } if (mop->stateless || mop->flushnext) { prefix |= MPPE_FLUSHED; dictinit = 1; mop->flushnext = 0; } if (dictinit) { /* Initialise our dictionary */ log_Printf(LogDEBUG, "MPPEOutput: Dictionary initialised [%d]\n", mop->cohnum); RC4_set_key(&mop->rc4key, mop->keylen, mop->sesskey); } /* Set MPPE packet prefix */ ua_htons(&prefix, rp); /* Save encrypted protocol number */ nproto = htons(*proto); RC4(&mop->rc4key, 2, (char *)&nproto, rp + 2); /* Encrypt main packet */ rp = MBUF_CTOP(mp); RC4(&mop->rc4key, ilen, rp, rp); mop->cohnum++; mop->cohnum &= ~MPPE_HEADER_BITMASK; /* Set the protocol number */ *proto = ccp_Proto(ccp); len = m_length(mo); ccp->uncompout += ilen; ccp->compout += len; log_Printf(LogDEBUG, "MPPE: Output: Encrypted: Proto %02x (%d bytes)\n", *proto, len); return mo; } static void MPPEResetInput(void *v) { log_Printf(LogCCP, "MPPE: Unexpected input channel ack\n"); } static struct mbuf * MPPEInput(void *v, struct ccp *ccp, u_short *proto, struct mbuf *mp) { struct mppe_state *mip = (struct mppe_state *)v; u_short prefix; char *rp; int dictinit, flushed, ilen, len, n; ilen = m_length(mp); dictinit = 0; ccp->compin += ilen; log_Printf(LogDEBUG, "MPPE: Input: Proto %02x (%d bytes)\n", *proto, ilen); log_DumpBp(LogDEBUG, "MPPE: Input: Packet:", mp); mp = mbuf_Read(mp, &prefix, 2); prefix = ntohs(prefix); flushed = prefix & MPPE_FLUSHED; prefix &= ~flushed; if ((prefix & MPPE_HEADER_BITMASK) != MPPE_ENCRYPTED) { log_Printf(LogERROR, "MPPE: Input: Invalid packet (flags = 0x%x)\n", (prefix & MPPE_HEADER_BITMASK) | flushed); m_freem(mp); return NULL; } prefix &= ~MPPE_HEADER_BITMASK; if (!flushed && mip->stateless) { log_Printf(LogCCP, "MPPEInput: Packet without MPPE_FLUSHED set" " in stateless mode\n"); flushed = MPPE_FLUSHED; /* Should we really continue ? */ } if (mip->stateless) { /* Change our key for each missed packet in stateless mode */ while (prefix != mip->cohnum) { log_Printf(LogDEBUG, "MPPEInput: Key changed [%u]\n", prefix); MPPEKeyChange(mip); /* * mip->cohnum contains what we received last time in stateless * mode. */ mip->cohnum++; mip->cohnum &= ~MPPE_HEADER_BITMASK; } dictinit = 1; } else { if (flushed) { /* * We can always process a flushed packet. * Catch up on any outstanding key changes. */ n = (prefix >> MPPE_HEADER_FLAGSHIFT) - (mip->cohnum >> MPPE_HEADER_FLAGSHIFT); if (n < 0) n += MPPE_HEADER_STATEFUL_KEYCHANGES; while (n--) { log_Printf(LogDEBUG, "MPPEInput: Key changed during catchup [%u]\n", prefix); MPPEKeyChange(mip); } mip->flushrequired = 0; mip->cohnum = prefix; dictinit = 1; } if (mip->flushrequired) { /* * Perhaps we should be lenient if * (prefix & MPPE_HEADER_FLAGMASK) == MPPE_HEADER_FLAG * The spec says that we shouldn't be though.... */ log_Printf(LogDEBUG, "MPPE: Not flushed - discarded\n"); fsm_Output(&ccp->fsm, CODE_RESETREQ, ccp->fsm.reqid++, NULL, 0, MB_CCPOUT); m_freem(mp); return NULL; } if (prefix != mip->cohnum) { /* * We're in stateful mode and didn't receive the expected * packet. Send a reset request, but don't tell the CCP layer * about it as we don't expect to receive a Reset ACK ! * Guess what... M$ invented this ! */ log_Printf(LogCCP, "MPPE: Input: Got seq %u, not %u\n", prefix, mip->cohnum); fsm_Output(&ccp->fsm, CODE_RESETREQ, ccp->fsm.reqid++, NULL, 0, MB_CCPOUT); mip->flushrequired = 1; m_freem(mp); return NULL; } if ((prefix & MPPE_HEADER_FLAGMASK) == MPPE_HEADER_FLAG) { log_Printf(LogDEBUG, "MPPEInput: Key changed [%u]\n", prefix); MPPEKeyChange(mip); dictinit = 1; } else if (flushed) dictinit = 1; /* * mip->cohnum contains what we expect to receive next time in stateful * mode. */ mip->cohnum++; mip->cohnum &= ~MPPE_HEADER_BITMASK; } if (dictinit) { log_Printf(LogDEBUG, "MPPEInput: Dictionary initialised [%u]\n", prefix); RC4_set_key(&mip->rc4key, mip->keylen, mip->sesskey); } mp = mbuf_Read(mp, proto, 2); RC4(&mip->rc4key, 2, (char *)proto, (char *)proto); *proto = ntohs(*proto); rp = MBUF_CTOP(mp); len = m_length(mp); RC4(&mip->rc4key, len, rp, rp); log_Printf(LogDEBUG, "MPPEInput: Decrypted: Proto %02x (%d bytes)\n", *proto, len); log_DumpBp(LogDEBUG, "MPPEInput: Decrypted: Packet:", mp); ccp->uncompin += len; return mp; } static void MPPEDictSetup(void *v, struct ccp *ccp, u_short proto, struct mbuf *mi) { } static const char * MPPEDispOpts(struct lcp_opt *o) { static char buf[70]; u_int32_t val; char ch; int len; ua_ntohl(o->data, &val); snprintf(buf, sizeof buf, "value 0x%08x ", (unsigned)val); len = strlen(buf); if (!(val & MPPE_OPT_BITMASK)) { snprintf(buf + len, sizeof buf - len, "(0"); len++; } else { ch = '('; if (val & MPPE_OPT_128BIT) { snprintf(buf + len, sizeof buf - len, "%c128", ch); len += strlen(buf + len); ch = '/'; } if (val & MPPE_OPT_56BIT) { snprintf(buf + len, sizeof buf - len, "%c56", ch); len += strlen(buf + len); ch = '/'; } if (val & MPPE_OPT_40BIT) { snprintf(buf + len, sizeof buf - len, "%c40", ch); len += strlen(buf + len); ch = '/'; } } snprintf(buf + len, sizeof buf - len, " bits, state%s", (val & MPPE_OPT_STATELESS) ? "less" : "ful"); len += strlen(buf + len); if (val & MPPE_OPT_COMPRESSED) { snprintf(buf + len, sizeof buf - len, ", compressed"); len += strlen(buf + len); } snprintf(buf + len, sizeof buf - len, ")"); return buf; } static int MPPEUsable(struct fsm *fp) { struct lcp *lcp; int ok; lcp = &fp->link->lcp; ok = (lcp->want_auth == PROTO_CHAP && lcp->want_authtype == 0x81) || (lcp->his_auth == PROTO_CHAP && lcp->his_authtype == 0x81); if (!ok) log_Printf(LogCCP, "MPPE: Not usable without CHAP81\n"); return ok; } static int MPPERequired(struct fsm *fp) { return fp->link->ccp.cfg.mppe.required; } static u_int32_t MPPE_ConfigVal(const struct ccp_config *cfg) { u_int32_t val; val = cfg->mppe.state == MPPE_STATELESS ? MPPE_OPT_STATELESS : 0; switch(cfg->mppe.keybits) { case 128: val |= MPPE_OPT_128BIT; break; case 56: val |= MPPE_OPT_56BIT; break; case 40: val |= MPPE_OPT_40BIT; break; case 0: val |= MPPE_OPT_128BIT | MPPE_OPT_56BIT | MPPE_OPT_40BIT; break; } return val; } /* * What options should we use for our first configure request */ static void MPPEInitOptsOutput(struct lcp_opt *o, const struct ccp_config *cfg) { u_int32_t mval; o->len = 6; if (!MPPE_MasterKeyValid) { log_Printf(LogCCP, "MPPE: MasterKey is invalid," " MPPE is available only with CHAP81 authentication\n"); ua_htonl(0x0, o->data); return; } mval = MPPE_ConfigVal(cfg); ua_htonl(&mval, o->data); } /* * Our CCP request was NAK'd with the given options */ static int MPPESetOptsOutput(struct lcp_opt *o, const struct ccp_config *cfg) { u_int32_t mval, peer; ua_ntohl(o->data, &peer); if (!MPPE_MasterKeyValid) /* Treat their NAK as a REJ */ return MODE_NAK; mval = MPPE_ConfigVal(cfg); /* * If we haven't been configured with a specific number of keybits, allow * whatever the peer asks for. */ if (!cfg->mppe.keybits) { mval &= ~MPPE_OPT_BITMASK; mval |= (peer & MPPE_OPT_BITMASK); if (!(mval & MPPE_OPT_BITMASK)) mval |= MPPE_OPT_128BIT; } /* Adjust our statelessness */ if (cfg->mppe.state == MPPE_ANYSTATE) { mval &= ~MPPE_OPT_STATELESS; mval |= (peer & MPPE_OPT_STATELESS); } ua_htonl(&mval, o->data); return MODE_ACK; } /* * The peer has requested the given options */ static int MPPESetOptsInput(struct lcp_opt *o, const struct ccp_config *cfg) { u_int32_t mval, peer; int res = MODE_ACK; ua_ntohl(o->data, &peer); if (!MPPE_MasterKeyValid) { if (peer != 0) { peer = 0; ua_htonl(&peer, o->data); return MODE_NAK; } else return MODE_ACK; } mval = MPPE_ConfigVal(cfg); if (peer & ~MPPE_OPT_MASK) /* He's asking for bits we don't know about */ res = MODE_NAK; if (peer & MPPE_OPT_STATELESS) { if (cfg->mppe.state == MPPE_STATEFUL) /* Peer can't have stateless */ res = MODE_NAK; else /* Peer wants stateless, that's ok */ mval |= MPPE_OPT_STATELESS; } else { if (cfg->mppe.state == MPPE_STATELESS) /* Peer must have stateless */ res = MODE_NAK; else /* Peer doesn't want stateless, that's ok */ mval &= ~MPPE_OPT_STATELESS; } /* If we've got a configured number of keybits - the peer must use that */ if (cfg->mppe.keybits) { ua_htonl(&mval, o->data); return peer == mval ? res : MODE_NAK; } /* If a specific number of bits hasn't been requested, we'll need to NAK */ switch (peer & MPPE_OPT_BITMASK) { case MPPE_OPT_128BIT: case MPPE_OPT_56BIT: case MPPE_OPT_40BIT: break; default: res = MODE_NAK; } /* Suggest the best number of bits */ mval &= ~MPPE_OPT_BITMASK; if (peer & MPPE_OPT_128BIT) mval |= MPPE_OPT_128BIT; else if (peer & MPPE_OPT_56BIT) mval |= MPPE_OPT_56BIT; else if (peer & MPPE_OPT_40BIT) mval |= MPPE_OPT_40BIT; else mval |= MPPE_OPT_128BIT; ua_htonl(&mval, o->data); return res; } static struct mppe_state * MPPE_InitState(struct lcp_opt *o) { struct mppe_state *mp; u_int32_t val; if ((mp = calloc(1, sizeof *mp)) != NULL) { ua_ntohl(o->data, &val); switch (val & MPPE_OPT_BITMASK) { case MPPE_OPT_128BIT: mp->keylen = 16; mp->keybits = 128; break; case MPPE_OPT_56BIT: mp->keylen = 8; mp->keybits = 56; break; case MPPE_OPT_40BIT: mp->keylen = 8; mp->keybits = 40; break; default: log_Printf(LogWARN, "Unexpected MPPE options 0x%08x\n", val); free(mp); return NULL; } mp->stateless = !!(val & MPPE_OPT_STATELESS); } return mp; } static void * MPPEInitInput(struct lcp_opt *o) { struct mppe_state *mip; if (!MPPE_MasterKeyValid) { log_Printf(LogWARN, "MPPE: Cannot initialise without CHAP81\n"); return NULL; } if ((mip = MPPE_InitState(o)) == NULL) { log_Printf(LogWARN, "MPPEInput: Cannot initialise - unexpected options\n"); return NULL; } log_Printf(LogDEBUG, "MPPE: InitInput: %d-bits\n", mip->keybits); GetAsymetricStartKey(MPPE_MasterKey, mip->mastkey, mip->keylen, 0, MPPE_IsServer); GetNewKeyFromSHA(mip->mastkey, mip->mastkey, mip->keylen, mip->sesskey); MPPEReduceSessionKey(mip); log_Printf(LogCCP, "MPPE: Input channel initiated\n"); if (!mip->stateless) { /* * We need to initialise our dictionary here as the first packet we * receive is unlikely to have the FLUSHED bit set. */ log_Printf(LogDEBUG, "MPPEInitInput: Dictionary initialised [%d]\n", mip->cohnum); RC4_set_key(&mip->rc4key, mip->keylen, mip->sesskey); } else { /* * We do the first key change here as the first packet is expected * to have a sequence number of 0 and we'll therefore not expect * to have to change the key at that point. */ log_Printf(LogDEBUG, "MPPEInitInput: Key changed [%d]\n", mip->cohnum); MPPEKeyChange(mip); } return mip; } static void * MPPEInitOutput(struct lcp_opt *o) { struct mppe_state *mop; if (!MPPE_MasterKeyValid) { log_Printf(LogWARN, "MPPE: Cannot initialise without CHAP81\n"); return NULL; } if ((mop = MPPE_InitState(o)) == NULL) { log_Printf(LogWARN, "MPPEOutput: Cannot initialise - unexpected options\n"); return NULL; } log_Printf(LogDEBUG, "MPPE: InitOutput: %d-bits\n", mop->keybits); GetAsymetricStartKey(MPPE_MasterKey, mop->mastkey, mop->keylen, 1, MPPE_IsServer); GetNewKeyFromSHA(mop->mastkey, mop->mastkey, mop->keylen, mop->sesskey); MPPEReduceSessionKey(mop); log_Printf(LogCCP, "MPPE: Output channel initiated\n"); if (!mop->stateless) { /* * We need to initialise our dictionary now as the first packet we * send won't have the FLUSHED bit set. */ log_Printf(LogDEBUG, "MPPEInitOutput: Dictionary initialised [%d]\n", mop->cohnum); RC4_set_key(&mop->rc4key, mop->keylen, mop->sesskey); } return mop; } static void MPPETermInput(void *v) { free(v); } static void MPPETermOutput(void *v) { free(v); } const struct ccp_algorithm MPPEAlgorithm = { TY_MPPE, CCP_NEG_MPPE, MPPEDispOpts, MPPEUsable, MPPERequired, { MPPESetOptsInput, MPPEInitInput, MPPETermInput, MPPEResetInput, MPPEInput, MPPEDictSetup }, { 2, MPPEInitOptsOutput, MPPESetOptsOutput, MPPEInitOutput, MPPETermOutput, MPPEResetOutput, MPPEOutput }, };