/* $OpenBSD: chap.c,v 1.12 2003/04/04 20:25:07 deraadt Exp $ */ /* * chap.c - Challenge Handshake Authentication Protocol. * * Copyright (c) 1989-2002 Paul Mackerras. 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. * * 3. The name(s) of the authors of this software must not be used to * endorse or promote products derived from this software without * prior written permission. * * 4. Redistributions of any form whatsoever must retain the following * acknowledgment: * "This product includes software developed by Paul Mackerras * ". * * THE AUTHORS OF THIS SOFTWARE DISCLAIM ALL WARRANTIES WITH REGARD TO * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY * AND FITNESS, IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY * SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. * * Copyright (c) 1991 Gregory M. Christy. * All rights reserved. * * Redistribution and use in source and binary forms are permitted * provided that the above copyright notice and this paragraph are * duplicated in all such forms and that any documentation, * advertising materials, and other materials related to such * distribution and use acknowledge that the software was developed * by Gregory M. Christy. The name of the author may not be used to * endorse or promote products derived from this software without * specific prior written permission. * * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. */ #ifndef lint #if 0 static char rcsid[] = "Id: chap.c,v 1.15 1997/11/27 06:07:48 paulus Exp $"; #else static char rcsid[] = "$OpenBSD: chap.c,v 1.12 2003/04/04 20:25:07 deraadt Exp $"; #endif #endif /* * TODO: */ #include #include #include #include #include #include #include "pppd.h" #include "chap.h" #ifdef CHAPMS #include "chap_ms.h" #endif /* * Protocol entry points. */ static void ChapInit(int); static void ChapLowerUp(int); static void ChapLowerDown(int); static void ChapInput(int, u_char *, int); static void ChapProtocolReject(int); static int ChapPrintPkt(u_char *, int, void (*)(void *, char *, ...), void *); struct protent chap_protent = { PPP_CHAP, ChapInit, ChapInput, ChapProtocolReject, ChapLowerUp, ChapLowerDown, NULL, NULL, ChapPrintPkt, NULL, 1, "CHAP", NULL, NULL, NULL }; chap_state chap[NUM_PPP]; /* CHAP state; one for each unit */ static void ChapChallengeTimeout(void *); static void ChapResponseTimeout(void *); static void ChapReceiveChallenge(chap_state *, u_char *, int, int); static void ChapRechallenge(void *); static void ChapReceiveResponse(chap_state *, u_char *, int, int); static void ChapReceiveSuccess(chap_state *, u_char *, int, int); static void ChapReceiveFailure(chap_state *, u_char *, int, int); static void ChapSendStatus(chap_state *, int); static void ChapSendChallenge(chap_state *); static void ChapSendResponse(chap_state *); static void ChapGenChallenge(chap_state *); extern double drand48(void); extern void srand48(long); /* * ChapInit - Initialize a CHAP unit. */ static void ChapInit(unit) int unit; { chap_state *cstate = &chap[unit]; BZERO(cstate, sizeof(*cstate)); cstate->unit = unit; cstate->clientstate = CHAPCS_INITIAL; cstate->serverstate = CHAPSS_INITIAL; cstate->timeouttime = CHAP_DEFTIMEOUT; cstate->max_transmits = CHAP_DEFTRANSMITS; /* random number generator is initialized in magic_init */ } /* * ChapAuthWithPeer - Authenticate us with our peer (start client). * */ void ChapAuthWithPeer(unit, our_name, digest) int unit; char *our_name; int digest; { chap_state *cstate = &chap[unit]; cstate->resp_name = our_name; cstate->resp_type = digest; if (cstate->clientstate == CHAPCS_INITIAL || cstate->clientstate == CHAPCS_PENDING) { /* lower layer isn't up - wait until later */ cstate->clientstate = CHAPCS_PENDING; return; } /* * We get here as a result of LCP coming up. * So even if CHAP was open before, we will * have to re-authenticate ourselves. */ cstate->clientstate = CHAPCS_LISTEN; } /* * ChapAuthPeer - Authenticate our peer (start server). */ void ChapAuthPeer(unit, our_name, digest) int unit; char *our_name; int digest; { chap_state *cstate = &chap[unit]; cstate->chal_name = our_name; cstate->chal_type = digest; if (cstate->serverstate == CHAPSS_INITIAL || cstate->serverstate == CHAPSS_PENDING) { /* lower layer isn't up - wait until later */ cstate->serverstate = CHAPSS_PENDING; return; } ChapGenChallenge(cstate); ChapSendChallenge(cstate); /* crank it up dude! */ cstate->serverstate = CHAPSS_INITIAL_CHAL; } /* * ChapChallengeTimeout - Timeout expired on sending challenge. */ static void ChapChallengeTimeout(arg) void *arg; { chap_state *cstate = (chap_state *) arg; /* if we aren't sending challenges, don't worry. then again we */ /* probably shouldn't be here either */ if (cstate->serverstate != CHAPSS_INITIAL_CHAL && cstate->serverstate != CHAPSS_RECHALLENGE) return; if (cstate->chal_transmits >= cstate->max_transmits) { /* give up on peer */ syslog(LOG_ERR, "Peer failed to respond to CHAP challenge"); cstate->serverstate = CHAPSS_BADAUTH; auth_peer_fail(cstate->unit, PPP_CHAP); return; } ChapSendChallenge(cstate); /* Re-send challenge */ } /* * ChapResponseTimeout - Timeout expired on sending response. */ static void ChapResponseTimeout(arg) void *arg; { chap_state *cstate = (chap_state *) arg; /* if we aren't sending a response, don't worry. */ if (cstate->clientstate != CHAPCS_RESPONSE) return; ChapSendResponse(cstate); /* re-send response */ } /* * ChapRechallenge - Time to challenge the peer again. */ static void ChapRechallenge(arg) void *arg; { chap_state *cstate = (chap_state *) arg; /* if we aren't sending a response, don't worry. */ if (cstate->serverstate != CHAPSS_OPEN) return; ChapGenChallenge(cstate); ChapSendChallenge(cstate); cstate->serverstate = CHAPSS_RECHALLENGE; } /* * ChapLowerUp - The lower layer is up. * * Start up if we have pending requests. */ static void ChapLowerUp(unit) int unit; { chap_state *cstate = &chap[unit]; if (cstate->clientstate == CHAPCS_INITIAL) cstate->clientstate = CHAPCS_CLOSED; else if (cstate->clientstate == CHAPCS_PENDING) cstate->clientstate = CHAPCS_LISTEN; if (cstate->serverstate == CHAPSS_INITIAL) cstate->serverstate = CHAPSS_CLOSED; else if (cstate->serverstate == CHAPSS_PENDING) { ChapGenChallenge(cstate); ChapSendChallenge(cstate); cstate->serverstate = CHAPSS_INITIAL_CHAL; } } /* * ChapLowerDown - The lower layer is down. * * Cancel all timeouts. */ static void ChapLowerDown(unit) int unit; { chap_state *cstate = &chap[unit]; /* Timeout(s) pending? Cancel if so. */ if (cstate->serverstate == CHAPSS_INITIAL_CHAL || cstate->serverstate == CHAPSS_RECHALLENGE) UNTIMEOUT(ChapChallengeTimeout, cstate); else if (cstate->serverstate == CHAPSS_OPEN && cstate->chal_interval != 0) UNTIMEOUT(ChapRechallenge, cstate); if (cstate->clientstate == CHAPCS_RESPONSE) UNTIMEOUT(ChapResponseTimeout, cstate); cstate->clientstate = CHAPCS_INITIAL; cstate->serverstate = CHAPSS_INITIAL; } /* * ChapProtocolReject - Peer doesn't grok CHAP. */ static void ChapProtocolReject(unit) int unit; { chap_state *cstate = &chap[unit]; if (cstate->serverstate != CHAPSS_INITIAL && cstate->serverstate != CHAPSS_CLOSED) auth_peer_fail(unit, PPP_CHAP); if (cstate->clientstate != CHAPCS_INITIAL && cstate->clientstate != CHAPCS_CLOSED) auth_withpeer_fail(unit, PPP_CHAP); ChapLowerDown(unit); /* shutdown chap */ } /* * ChapInput - Input CHAP packet. */ static void ChapInput(unit, inpacket, packet_len) int unit; u_char *inpacket; int packet_len; { chap_state *cstate = &chap[unit]; u_char *inp; u_char code, id; int len; /* * Parse header (code, id and length). * If packet too short, drop it. */ inp = inpacket; if (packet_len < CHAP_HEADERLEN) { CHAPDEBUG((LOG_INFO, "ChapInput: rcvd short header.")); return; } GETCHAR(code, inp); GETCHAR(id, inp); GETSHORT(len, inp); if (len < CHAP_HEADERLEN) { CHAPDEBUG((LOG_INFO, "ChapInput: rcvd illegal length.")); return; } if (len > packet_len) { CHAPDEBUG((LOG_INFO, "ChapInput: rcvd short packet.")); return; } len -= CHAP_HEADERLEN; /* * Action depends on code (as in fact it usually does :-). */ switch (code) { case CHAP_CHALLENGE: ChapReceiveChallenge(cstate, inp, id, len); break; case CHAP_RESPONSE: ChapReceiveResponse(cstate, inp, id, len); break; case CHAP_FAILURE: ChapReceiveFailure(cstate, inp, id, len); break; case CHAP_SUCCESS: ChapReceiveSuccess(cstate, inp, id, len); break; default: /* Need code reject? */ syslog(LOG_WARNING, "Unknown CHAP code (%d) received.", code); break; } } /* * ChapReceiveChallenge - Receive Challenge and send Response. */ static void ChapReceiveChallenge(cstate, inp, id, len) chap_state *cstate; u_char *inp; int id; int len; { int rchallenge_len; u_char *rchallenge; int secret_len; char secret[MAXSECRETLEN]; char rhostname[256]; MD5_CTX mdContext; u_char hash[MD5_SIGNATURE_SIZE]; CHAPDEBUG((LOG_INFO, "ChapReceiveChallenge: Rcvd id %d.", id)); if (cstate->clientstate == CHAPCS_CLOSED || cstate->clientstate == CHAPCS_PENDING) { CHAPDEBUG((LOG_INFO, "ChapReceiveChallenge: in state %d", cstate->clientstate)); return; } if (len < 2) { CHAPDEBUG((LOG_INFO, "ChapReceiveChallenge: rcvd short packet.")); return; } GETCHAR(rchallenge_len, inp); len -= sizeof (u_char) + rchallenge_len; /* now name field length */ if (len < 0) { CHAPDEBUG((LOG_INFO, "ChapReceiveChallenge: rcvd short packet.")); return; } rchallenge = inp; INCPTR(rchallenge_len, inp); if (len >= sizeof(rhostname)) len = sizeof(rhostname) - 1; BCOPY(inp, rhostname, len); rhostname[len] = '\000'; CHAPDEBUG((LOG_INFO, "ChapReceiveChallenge: received name field '%s'", rhostname)); /* Microsoft doesn't send their name back in the PPP packet */ if (remote_name[0] != 0 && (explicit_remote || rhostname[0] == 0)) { strlcpy(rhostname, remote_name, sizeof(rhostname)); CHAPDEBUG((LOG_INFO, "ChapReceiveChallenge: using '%s' as remote name", rhostname)); } /* get secret for authenticating ourselves with the specified host */ if (!get_secret(cstate->unit, cstate->resp_name, rhostname, secret, &secret_len, 0)) { secret_len = 0; /* assume null secret if can't find one */ syslog(LOG_WARNING, "No CHAP secret found for authenticating us to %s", rhostname); } /* cancel response send timeout if necessary */ if (cstate->clientstate == CHAPCS_RESPONSE) UNTIMEOUT(ChapResponseTimeout, cstate); cstate->resp_id = id; cstate->resp_transmits = 0; /* generate MD based on negotiated type */ switch (cstate->resp_type) { case CHAP_DIGEST_MD5: MD5Init(&mdContext); MD5Update(&mdContext, &cstate->resp_id, 1); MD5Update(&mdContext, secret, secret_len); MD5Update(&mdContext, rchallenge, rchallenge_len); MD5Final(hash, &mdContext); BCOPY(hash, cstate->response, MD5_SIGNATURE_SIZE); cstate->resp_length = MD5_SIGNATURE_SIZE; break; #ifdef CHAPMS case CHAP_MICROSOFT: ChapMS(cstate, rchallenge, rchallenge_len, secret, secret_len); break; #endif default: CHAPDEBUG((LOG_INFO, "unknown digest type %d", cstate->resp_type)); return; } BZERO(secret, sizeof(secret)); ChapSendResponse(cstate); } /* * ChapReceiveResponse - Receive and process response. */ static void ChapReceiveResponse(cstate, inp, id, len) chap_state *cstate; u_char *inp; int id; int len; { u_char *remmd, remmd_len; int secret_len, old_state; int code; char rhostname[256]; MD5_CTX mdContext; char secret[MAXSECRETLEN]; u_char hash[MD5_SIGNATURE_SIZE]; CHAPDEBUG((LOG_INFO, "ChapReceiveResponse: Rcvd id %d.", id)); if (cstate->serverstate == CHAPSS_CLOSED || cstate->serverstate == CHAPSS_PENDING) { CHAPDEBUG((LOG_INFO, "ChapReceiveResponse: in state %d", cstate->serverstate)); return; } if (id != cstate->chal_id) return; /* doesn't match ID of last challenge */ /* * If we have received a duplicate or bogus Response, * we have to send the same answer (Success/Failure) * as we did for the first Response we saw. */ if (cstate->serverstate == CHAPSS_OPEN) { ChapSendStatus(cstate, CHAP_SUCCESS); return; } if (cstate->serverstate == CHAPSS_BADAUTH) { ChapSendStatus(cstate, CHAP_FAILURE); return; } if (len < 2) { CHAPDEBUG((LOG_INFO, "ChapReceiveResponse: rcvd short packet.")); return; } GETCHAR(remmd_len, inp); /* get length of MD */ remmd = inp; /* get pointer to MD */ INCPTR(remmd_len, inp); len -= sizeof (u_char) + remmd_len; if (len < 0) { CHAPDEBUG((LOG_INFO, "ChapReceiveResponse: rcvd short packet.")); return; } UNTIMEOUT(ChapChallengeTimeout, cstate); if (len >= sizeof(rhostname)) len = sizeof(rhostname) - 1; BCOPY(inp, rhostname, len); rhostname[len] = '\000'; CHAPDEBUG((LOG_INFO, "ChapReceiveResponse: received name field: %s", rhostname)); /* * Get secret for authenticating them with us, * do the hash ourselves, and compare the result. */ code = CHAP_FAILURE; if (!get_secret(cstate->unit, rhostname, cstate->chal_name, secret, &secret_len, 1)) { syslog(LOG_WARNING, "No CHAP secret found for authenticating %s", rhostname); } else { /* generate MD based on negotiated type */ switch (cstate->chal_type) { case CHAP_DIGEST_MD5: /* only MD5 is defined for now */ if (remmd_len != MD5_SIGNATURE_SIZE) break; /* it's not even the right length */ MD5Init(&mdContext); MD5Update(&mdContext, &cstate->chal_id, 1); MD5Update(&mdContext, secret, secret_len); MD5Update(&mdContext, cstate->challenge, cstate->chal_len); MD5Final(hash, &mdContext); /* compare local and remote MDs and send the appropriate status */ if (memcmp (hash, remmd, MD5_SIGNATURE_SIZE) == 0) code = CHAP_SUCCESS; /* they are the same! */ break; default: CHAPDEBUG((LOG_INFO, "unknown digest type %d", cstate->chal_type)); } } BZERO(secret, sizeof(secret)); ChapSendStatus(cstate, code); if (code == CHAP_SUCCESS) { old_state = cstate->serverstate; cstate->serverstate = CHAPSS_OPEN; if (old_state == CHAPSS_INITIAL_CHAL) { auth_peer_success(cstate->unit, PPP_CHAP, rhostname, len); } if (cstate->chal_interval != 0) TIMEOUT(ChapRechallenge, cstate, cstate->chal_interval); syslog(LOG_NOTICE, "CHAP peer authentication succeeded for %s", rhostname); } else { syslog(LOG_ERR, "CHAP peer authentication failed for remote host %s", rhostname); cstate->serverstate = CHAPSS_BADAUTH; auth_peer_fail(cstate->unit, PPP_CHAP); } } /* * ChapReceiveSuccess - Receive Success */ static void ChapReceiveSuccess(cstate, inp, id, len) chap_state *cstate; u_char *inp; u_char id; int len; { CHAPDEBUG((LOG_INFO, "ChapReceiveSuccess: Rcvd id %d.", id)); if (cstate->clientstate == CHAPCS_OPEN) /* presumably an answer to a duplicate response */ return; if (cstate->clientstate != CHAPCS_RESPONSE) { /* don't know what this is */ CHAPDEBUG((LOG_INFO, "ChapReceiveSuccess: in state %d\n", cstate->clientstate)); return; } UNTIMEOUT(ChapResponseTimeout, cstate); /* * Print message. */ if (len > 0) PRINTMSG(inp, len); cstate->clientstate = CHAPCS_OPEN; auth_withpeer_success(cstate->unit, PPP_CHAP); } /* * ChapReceiveFailure - Receive failure. */ static void ChapReceiveFailure(cstate, inp, id, len) chap_state *cstate; u_char *inp; u_char id; int len; { CHAPDEBUG((LOG_INFO, "ChapReceiveFailure: Rcvd id %d.", id)); if (cstate->clientstate != CHAPCS_RESPONSE) { /* don't know what this is */ CHAPDEBUG((LOG_INFO, "ChapReceiveFailure: in state %d\n", cstate->clientstate)); return; } UNTIMEOUT(ChapResponseTimeout, cstate); /* * Print message. */ if (len > 0) PRINTMSG(inp, len); syslog(LOG_ERR, "CHAP authentication failed"); auth_withpeer_fail(cstate->unit, PPP_CHAP); } /* * ChapSendChallenge - Send an Authenticate challenge. */ static void ChapSendChallenge(cstate) chap_state *cstate; { u_char *outp; int chal_len, name_len; int outlen; chal_len = cstate->chal_len; name_len = strlen(cstate->chal_name); outlen = CHAP_HEADERLEN + sizeof (u_char) + chal_len + name_len; outp = outpacket_buf; MAKEHEADER(outp, PPP_CHAP); /* paste in a CHAP header */ PUTCHAR(CHAP_CHALLENGE, outp); PUTCHAR(cstate->chal_id, outp); PUTSHORT(outlen, outp); PUTCHAR(chal_len, outp); /* put length of challenge */ BCOPY(cstate->challenge, outp, chal_len); INCPTR(chal_len, outp); BCOPY(cstate->chal_name, outp, name_len); /* append hostname */ output(cstate->unit, outpacket_buf, outlen + PPP_HDRLEN); CHAPDEBUG((LOG_INFO, "ChapSendChallenge: Sent id %d.", cstate->chal_id)); TIMEOUT(ChapChallengeTimeout, cstate, cstate->timeouttime); ++cstate->chal_transmits; } /* * ChapSendStatus - Send a status response (ack or nak). */ static void ChapSendStatus(cstate, code) chap_state *cstate; int code; { u_char *outp; int outlen, msglen; char msg[256]; if (code == CHAP_SUCCESS) snprintf(msg, sizeof msg, "Welcome to %s.", hostname); else snprintf(msg, sizeof msg, "I don't like you. Go 'way."); msglen = strlen(msg); outlen = CHAP_HEADERLEN + msglen; outp = outpacket_buf; MAKEHEADER(outp, PPP_CHAP); /* paste in a header */ PUTCHAR(code, outp); PUTCHAR(cstate->chal_id, outp); PUTSHORT(outlen, outp); BCOPY(msg, outp, msglen); output(cstate->unit, outpacket_buf, outlen + PPP_HDRLEN); CHAPDEBUG((LOG_INFO, "ChapSendStatus: Sent code %d, id %d.", code, cstate->chal_id)); } /* * ChapGenChallenge is used to generate a pseudo-random challenge string of * a pseudo-random length between min_len and max_len. The challenge * string and its length are stored in *cstate, and various other fields of * *cstate are initialized. */ static void ChapGenChallenge(cstate) chap_state *cstate; { int chal_len; u_char *ptr = cstate->challenge; unsigned int i; /* pick a random challenge length between MIN_CHALLENGE_LENGTH and MAX_CHALLENGE_LENGTH */ chal_len = (unsigned) ((drand48() * (MAX_CHALLENGE_LENGTH - MIN_CHALLENGE_LENGTH)) + MIN_CHALLENGE_LENGTH); cstate->chal_len = chal_len; cstate->chal_id = ++cstate->id; cstate->chal_transmits = 0; /* generate a random string */ for (i = 0; i < chal_len; i++ ) *ptr++ = (char) (drand48() * 0xff); } /* * ChapSendResponse - send a response packet with values as specified * in *cstate. */ /* ARGSUSED */ static void ChapSendResponse(cstate) chap_state *cstate; { u_char *outp; int outlen, md_len, name_len; md_len = cstate->resp_length; name_len = strlen(cstate->resp_name); outlen = CHAP_HEADERLEN + sizeof (u_char) + md_len + name_len; outp = outpacket_buf; MAKEHEADER(outp, PPP_CHAP); PUTCHAR(CHAP_RESPONSE, outp); /* we are a response */ PUTCHAR(cstate->resp_id, outp); /* copy id from challenge packet */ PUTSHORT(outlen, outp); /* packet length */ PUTCHAR(md_len, outp); /* length of MD */ BCOPY(cstate->response, outp, md_len); /* copy MD to buffer */ INCPTR(md_len, outp); BCOPY(cstate->resp_name, outp, name_len); /* append our name */ /* send the packet */ output(cstate->unit, outpacket_buf, outlen + PPP_HDRLEN); cstate->clientstate = CHAPCS_RESPONSE; TIMEOUT(ChapResponseTimeout, cstate, cstate->timeouttime); ++cstate->resp_transmits; } /* * ChapPrintPkt - print the contents of a CHAP packet. */ static char *ChapCodenames[] = { "Challenge", "Response", "Success", "Failure" }; static int ChapPrintPkt(p, plen, printer, arg) u_char *p; int plen; void (*printer)(void *, char *, ...); void *arg; { int code, id, len; int clen, nlen; u_char x; if (plen < CHAP_HEADERLEN) return 0; GETCHAR(code, p); GETCHAR(id, p); GETSHORT(len, p); if (len < CHAP_HEADERLEN || len > plen) return 0; if (code >= 1 && code <= sizeof(ChapCodenames) / sizeof(char *)) printer(arg, " %s", ChapCodenames[code-1]); else printer(arg, " code=0x%x", code); printer(arg, " id=0x%x", id); len -= CHAP_HEADERLEN; switch (code) { case CHAP_CHALLENGE: case CHAP_RESPONSE: if (len < 1) break; clen = p[0]; if (len < clen + 1) break; ++p; nlen = len - clen - 1; printer(arg, " <"); for (; clen > 0; --clen) { GETCHAR(x, p); printer(arg, "%.2x", x); } printer(arg, ">, name = "); print_string((char *)p, nlen, printer, arg); break; case CHAP_FAILURE: case CHAP_SUCCESS: printer(arg, " "); print_string((char *)p, len, printer, arg); break; default: for (clen = len; clen > 0; --clen) { GETCHAR(x, p); printer(arg, " %.2x", x); } } return len + CHAP_HEADERLEN; }