aboutsummaryrefslogtreecommitdiff
path: root/src/cmd/auth/factotum/chap.c
blob: 2b2589022ebf1e0261babf88bb5704c6ae46e612 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
/*
 * CHAP, MSCHAP
 * 
 * The client does not authenticate the server, hence no CAI
 *
 * Protocol:
 *
 *	S -> C: random 8-byte challenge
 *	C -> S: user in UTF-8
 *	C -> S: Chapreply or MSchapreply structure
 *	S -> C: ok or 'bad why'
 *
 * The chap protocol requires the client to give it id=%d, the id of
 * the PPP message containing the challenge, which is used
 * as part of the response.  Because the client protocol is message-id
 * specific, there is no point in looping to try multiple keys.
 *
 * The MS chap protocol actually uses two different hashes, an
 * older insecure one called the LM (Lan Manager) hash, and a newer
 * more secure one called the NT hash.  By default we send back only
 * the NT hash, because the LM hash can help an eavesdropper run
 * a brute force attack.  If the key has an lm attribute, then we send only the
 * LM hash.
 */

#include "std.h"
#include "dat.h"

extern Proto chap, mschap;

enum {
	ChapChallen = 8,

	MShashlen = 16,
	MSchallen = 8,
	MSresplen = 24,
};

static int
chapcheck(Key *k)
{
	if(!strfindattr(k->attr, "user") || !strfindattr(k->privattr, "!password")){
		werrstr("need user and !password attributes");
		return -1;
	}
	return 0;
}

static void
nthash(uchar hash[MShashlen], char *passwd)
{
	uchar buf[512];
	int i;
	
	for(i=0; *passwd && i<sizeof(buf); passwd++) {
		buf[i++] = *passwd;
		buf[i++] = 0;
	}

	memset(hash, 0, 16);

	md4(buf, i, hash, 0);
}

static void
desencrypt(uchar data[8], uchar key[7])
{
	ulong ekey[32];

	key_setup(key, ekey);
	block_cipher(ekey, data, 0);
}

static void
lmhash(uchar hash[MShashlen], char *passwd)
{
	uchar buf[14];
	char *stdtext = "KGS!@#$%";
	int i;

	strncpy((char*)buf, passwd, sizeof(buf));
	for(i=0; i<sizeof(buf); i++)
		if(buf[i] >= 'a' && buf[i] <= 'z')
			buf[i] += 'A' - 'a';

	memset(hash, 0, 16);
	memcpy(hash, stdtext, 8);
	memcpy(hash+8, stdtext, 8);

	desencrypt(hash, buf);
	desencrypt(hash+8, buf+7);
}

static void
mschalresp(uchar resp[MSresplen], uchar hash[MShashlen], uchar chal[MSchallen])
{
	int i;
	uchar buf[21];
	
	memset(buf, 0, sizeof(buf));
	memcpy(buf, hash, MShashlen);

	for(i=0; i<3; i++) {
		memmove(resp+i*MSchallen, chal, MSchallen);
		desencrypt(resp+i*MSchallen, buf+i*7);
	}
}

static int
chapclient(Conv *c)
{
	int id, astype, nchal, npw, ret;
	uchar *chal;
	char *s, *pw, *user, *res;
	Attr *attr;
	Key *k;
	Chapreply cr;
	MSchapreply mscr;
	DigestState *ds;

	ret = -1;
	chal = nil;
	k = nil;
	attr = c->attr;

	if(c->proto == &chap){
		astype = AuthChap;
		s = strfindattr(attr, "id");
		if(s == nil || *s == 0){
			werrstr("need id=n attr in start message");
			goto out;
		}
		id = strtol(s, &s, 10);
		if(*s != 0 || id < 0 || id >= 256){
			werrstr("bad id=n attr in start message");
			goto out;
		}
		cr.id = id;
	}else if(c->proto == &mschap)
		astype = AuthMSchap;
	else{
		werrstr("bad proto");
		goto out;
	}

	c->state = "find key";
	k = keyfetch(c, "%A %s", attr, c->proto->keyprompt);
	if(k == nil)
		goto out;

	c->attr = addattrs(copyattr(attr), k->attr);

	c->state = "read challenge";
	if((nchal = convreadm(c, (char**)(void*)&chal)) < 0)
		goto out;
	if(astype == AuthMSchap && nchal != MSchallen)
	c->state = "write user";
	if((user = strfindattr(k->attr, "user")) == nil){
		werrstr("key has no user (cannot happen?)");
		goto out;
	}
	if(convprint(c, "%s", user) < 0)
		goto out;

	c->state = "write response";
	if((pw = strfindattr(k->privattr, "!password")) == nil){
		werrstr("key has no password (cannot happen?)");
		goto out;
	}
	npw = strlen(pw);

	if(astype == AuthChap){
		ds = md5(&cr.id, 1, 0, 0);
		md5((uchar*)pw, npw, 0, ds);
		md5(chal, nchal, (uchar*)cr.resp, ds);
		if(convwrite(c, &cr, sizeof cr) < 0)
			goto out;
	}else{
		uchar hash[MShashlen];

		memset(&mscr, 0, sizeof mscr);
		if(strfindattr(k->attr, "lm")){
			lmhash(hash, pw);
			mschalresp((uchar*)mscr.LMresp, hash, chal);
		}else{
			nthash(hash, pw);
			mschalresp((uchar*)mscr.NTresp, hash, chal);
		}
		if(convwrite(c, &mscr, sizeof mscr) < 0)
			goto out;
	}

	c->state = "read result";
	if(convreadm(c, &res) < 0)
		goto out;
	if(strcmp(res, "ok") == 0){
		ret = 0;
		werrstr("succeeded");
		goto out;
	}
	if(strncmp(res, "bad ", 4) != 0){
		werrstr("bad result: %s", res);
		goto out;
	}

	c->state = "replace key";
	keyevict(c, k, "%s", res+4);
	werrstr("%s", res+4);

out:
	free(res);
	keyclose(k);
	free(chal);
	if(c->attr != attr)
		freeattr(attr);
	return ret;
}

/* shared with auth dialing routines */
typedef struct ServerState ServerState;
struct ServerState
{
	int asfd;
	Key *k;
	Ticketreq tr;
	Ticket t;
	char *dom;
	char *hostid;
};

static int chapchal(ServerState*, int, char[ChapChallen]);
static int chapresp(ServerState*, char*, char*);

static int
chapserver(Conv *c)
{
	char chal[ChapChallen], *user, *resp;
	ServerState s;
	int astype, ret;
	Attr *a;

	ret = -1;
	user = nil;
	resp = nil;
	memset(&s, 0, sizeof s);
	s.asfd = -1;

	if(c->proto == &chap)
		astype = AuthChap;
	else if(c->proto == &mschap)
		astype = AuthMSchap;
	else{
		werrstr("bad proto");
		goto out;
	}

	c->state = "find key";
	if((s.k = plan9authkey(c->attr)) == nil)
		goto out;

	a = copyattr(s.k->attr);
	a = delattr(a, "proto");
	c->attr = addattrs(c->attr, a);
	freeattr(a);

	c->state = "authdial";
	s.hostid = strfindattr(s.k->attr, "user");
	s.dom = strfindattr(s.k->attr, "dom");
	if((s.asfd = xioauthdial(nil, s.dom)) < 0){
		werrstr("authdial %s: %r", s.dom);
		goto out;
	}

	c->state = "authchal";
	if(chapchal(&s, astype, chal) < 0)
		goto out;

	c->state = "write challenge";
	if(convprint(c, "%s", chal) < 0)
		goto out;

	c->state = "read user";
	if(convreadm(c, &user) < 0)
		goto out;

	c->state = "read response";
	if(convreadm(c, &resp) < 0)
		goto out;

	c->state = "authwrite";
	switch(chapresp(&s, user, resp)){
	default:
		fprint(2, "factotum: bad result from chapresp\n");
		goto out;
	case -1:
		goto out;
	case 0:
		c->state = "write status";
		if(convprint(c, "bad authentication failed") < 0)
			goto out;
		goto out;

	case 1:
		c->state = "write status";
		if(convprint(c, "ok") < 0)
			goto out;
		goto ok;
	}

ok:
	ret = 0;
	c->attr = addcap(c->attr, c->sysuser, &s.t);

out:
	keyclose(s.k);
	free(user);
	free(resp);
//	xioclose(s.asfd);
	return ret;
}

static int
chapchal(ServerState *s, int astype, char chal[ChapChallen])
{
	char trbuf[TICKREQLEN];
	Ticketreq tr;

	memset(&tr, 0, sizeof tr);

	tr.type = astype;

	if(strlen(s->hostid) >= sizeof tr.hostid){
		werrstr("hostid too long");
		return -1;
	}
	strcpy(tr.hostid, s->hostid);

	if(strlen(s->dom) >= sizeof tr.authdom){
		werrstr("domain too long");
		return -1;
	}
	strcpy(tr.authdom, s->dom);

	convTR2M(&tr, trbuf);
	if(xiowrite(s->asfd, trbuf, TICKREQLEN) != TICKREQLEN)
		return -1;

	if(xioasrdresp(s->asfd, chal, ChapChallen) <= 5)
		return -1;

	s->tr = tr;
	return 0;
}

static int
chapresp(ServerState *s, char *user, char *resp)
{
	char tabuf[TICKETLEN+AUTHENTLEN];
	char trbuf[TICKREQLEN];
	int len;
	Authenticator a;
	Ticket t;
	Ticketreq tr;

	tr = s->tr;
	if(memrandom(tr.chal, CHALLEN) < 0)
		return -1;

	if(strlen(user) >= sizeof tr.uid){
		werrstr("uid too long");
		return -1;
	}
	strcpy(tr.uid, user);

	convTR2M(&tr, trbuf);
	if(xiowrite(s->asfd, trbuf, TICKREQLEN) != TICKREQLEN)
		return -1;

	len = strlen(resp);
	if(xiowrite(s->asfd, resp, len) != len)
		return -1;

	if(xioasrdresp(s->asfd, tabuf, TICKETLEN+AUTHENTLEN) != TICKETLEN+AUTHENTLEN)
		return 0;

	convM2T(tabuf, &t, s->k->priv);
	if(t.num != AuthTs
	|| memcmp(t.chal, tr.chal, sizeof tr.chal) != 0){
		werrstr("key mismatch with auth server");
		return -1;
	}

	convM2A(tabuf+TICKETLEN, &a, t.key);
	if(a.num != AuthAc
	|| memcmp(a.chal, tr.chal, sizeof a.chal) != 0
	|| a.id != 0){
		werrstr("key2 mismatch with auth server");
		return -1;
	}

	s->t = t;
	return 1;
}

static Role
chaproles[] = 
{
	"client",	chapclient,
	"server",	chapserver,
	0
};

Proto chap = {
.name=		"chap",
.roles=		chaproles,
.checkkey=	chapcheck,
.keyprompt=	"user? !password?",
};

Proto mschap = {
.name=		"mschap",
.roles=		chaproles,
.checkkey=	chapcheck,
.keyprompt=	"user? !password?",
};