1 /*
2  * p9cr - one-sided challenge/response authentication
3  *
4  * Protocol:
5  *
6  *	C -> S: user
7  *	S -> C: challenge
8  *	C -> S: response
9  *	S -> C: ok or bad
10  *
11  * Note that this is the protocol between factotum and the local
12  * program, not between the two factotums.  The information
13  * exchanged here is wrapped in other protocols by the local
14  * programs.
15  */
16 
17 #include "std.h"
18 #include "dat.h"
19 
20 /* shared with auth dialing routines */
21 typedef struct ServerState ServerState;
22 struct ServerState
23 {
24 	int asfd;
25 	Key *k;
26 	Ticketreq tr;
27 	Ticket t;
28 	char *dom;
29 	char *hostid;
30 };
31 
32 enum
33 {
34 	MAXCHAL = 64,
35 	MAXRESP = 64,
36 };
37 
38 extern Proto p9cr, vnc;
39 static int p9response(char*, uchar*, uchar*);
40 // static int vncresponse(char*, uchar*, uchar*);
41 static int p9crchal(ServerState *s, int, char*, uchar*, int);
42 static int p9crresp(ServerState*, uchar*, int);
43 
44 static int
45 p9crcheck(Key *k)
46 {
47 	if(!strfindattr(k->attr, "user") || !strfindattr(k->privattr, "!password")){
48 		werrstr("need user and !password attributes");
49 		return -1;
50 	}
51 	return 0;
52 }
53 
54 static int
55 p9crclient(Conv *c)
56 {
57 	char *pw, *res, *user;
58 	int astype, challen, resplen, ntry, ret;
59 	Attr *attr;
60 	Key *k;
61 	uchar chal[MAXCHAL+1], resp[MAXRESP];
62 	int (*response)(char*, uchar*, uchar*);
63 
64 	k = nil;
65 	res = nil;
66 	ret = -1;
67 	attr = c->attr;
68 	astype = -1;
69 
70 	if(c->proto == &p9cr){
71 		astype = AuthChal;
72 		challen = NETCHLEN;
73 		response = p9response;
74 		attr = _mkattr(AttrNameval, "proto", "p9sk1", _delattr(_copyattr(attr), "proto"));
75 	}else if(c->proto == &vnc){
76 		astype = AuthVNC;
77 		challen = MAXCHAL;
78 	//	response = vncresponse;
79 		werrstr("no vnc");
80 		goto out;
81 	}else{
82 		werrstr("bad proto");
83 		goto out;
84 	}
85 
86 	c->state = "find key";
87 	k = keyfetch(c, "%A %s", attr, c->proto->keyprompt);
88 	if(k == nil)
89 		goto out;
90 
91 	for(ntry=1;; ntry++){
92 		if(c->attr != attr)
93 			freeattr(c->attr);
94 		c->attr = addattrs(copyattr(attr), k->attr);
95 
96 		if((pw = strfindattr(k->privattr, "!password")) == nil){
97 			werrstr("key has no !password (cannot happen)");
98 			goto out;
99 		}
100 		if((user = strfindattr(k->attr, "user")) == nil){
101 			werrstr("key has no user (cannot happen)");
102 			goto out;
103 		}
104 
105 		if(convprint(c, "%s", user) < 0)
106 			goto out;
107 
108 		if(convread(c, chal, challen) < 0)
109 			goto out;
110 		chal[challen] = 0;
111 
112 		if((resplen = (*response)(pw, chal, resp)) < 0)
113 			goto out;
114 
115 		if(convwrite(c, resp, resplen) < 0)
116 			goto out;
117 
118 		if(convreadm(c, &res) < 0)
119 			goto out;
120 
121 		if(strcmp(res, "ok") == 0)
122 			break;
123 
124 		if((k = keyreplace(c, k, "%s", res)) == nil){
125 			c->state = "auth failed";
126 			werrstr("%s", res);
127 			goto out;
128 		}
129 	}
130 
131 	werrstr("succeeded");
132 	ret = 0;
133 
134 out:
135 	USED(astype);
136 	keyclose(k);
137 	if(c->attr != attr)
138 		freeattr(attr);
139 	return ret;
140 }
141 
142 static int
143 p9crserver(Conv *c)
144 {
145 	uchar chal[MAXCHAL], *resp, *resp1;
146 	char *user;
147 	ServerState s;
148 	int astype, ret, challen, resplen;
149 	Attr *a;
150 
151 	ret = -1;
152 	user = nil;
153 	resp = nil;
154 	memset(&s, 0, sizeof s);
155 	s.asfd = -1;
156 
157 	if(c->proto == &p9cr){
158 		astype = AuthChal;
159 		challen = NETCHLEN;
160 	}else if(c->proto == &vnc){
161 		challen = MAXCHAL;
162 	}else{
163 		werrstr("bad proto");
164 		goto out;
165 	}
166 
167 	c->state = "find key";
168 	if((s.k = plan9authkey(c->attr)) == nil)
169 		goto out;
170 
171 	a = copyattr(s.k->attr);
172 	a = delattr(a, "proto");
173 	c->attr = addattrs(c->attr, a);
174 	freeattr(a);
175 
176 	c->state = "authdial";
177 	s.hostid = strfindattr(s.k->attr, "user");
178 	s.dom = strfindattr(s.k->attr, "dom");
179 	if((s.asfd = xioauthdial(nil, s.dom)) < 0){
180 		werrstr("authdial %s: %r", s.dom);
181 		goto out;
182 	}
183 
184 	for(;;){
185 		c->state = "read user";
186 		if(convreadm(c, &user) < 0)
187 			goto out;
188 
189 		c->state = "authchal";
190 		if(p9crchal(&s, astype, user, chal, challen) < 0)
191 			goto out;
192 
193 		c->state = "write challenge";
194 		if(convwrite(c, chal, challen) < 0)
195 			goto out;
196 
197 		c->state = "read response";
198 		if((resplen = convreadm(c, (char**)(void*)&resp)) < 0)
199 			goto out;
200 		if(c->proto == &p9cr){
201 			if(resplen > NETCHLEN){
202 				convprint(c, "bad response too long");
203 				goto out;
204 			}
205 			resp1 = emalloc(NETCHLEN);
206 			memset(resp1, 0, NETCHLEN);
207 			memmove(resp1, resp, resplen);
208 			free(resp);
209 			resp = resp1;
210 			resplen = NETCHLEN;
211 		}
212 
213 		c->state = "authwrite";
214 		switch(p9crresp(&s, resp, resplen)){
215 		case -1:
216 			fprint(2, "p9crresp: %r\n");
217 			goto out;
218 		case 0:
219 			c->state = "write status";
220 			if(convprint(c, "bad authentication failed") < 0)
221 				goto out;
222 			break;
223 		case 1:
224 			c->state = "write status";
225 			if(convprint(c, "ok") < 0)
226 				goto out;
227 			goto ok;
228 		}
229 		free(user);
230 		free(resp);
231 		user = nil;
232 		resp = nil;
233 	}
234 
235 ok:
236 	ret = 0;
237 	c->attr = addcap(c->attr, c->sysuser, &s.t);
238 
239 out:
240 	keyclose(s.k);
241 	free(user);
242 	free(resp);
243 	xioclose(s.asfd);
244 	return ret;
245 }
246 
247 static int
248 p9crchal(ServerState *s, int astype, char *user, uchar *chal, int challen)
249 {
250 	char trbuf[TICKREQLEN];
251 	Ticketreq tr;
252 	int n;
253 
254 	memset(&tr, 0, sizeof tr);
255 
256 	tr.type = astype;
257 
258 	if(strlen(s->hostid) >= sizeof tr.hostid){
259 		werrstr("hostid too long");
260 		return -1;
261 	}
262 	strcpy(tr.hostid, s->hostid);
263 
264 	if(strlen(s->dom) >= sizeof tr.authdom){
265 		werrstr("domain too long");
266 		return -1;
267 	}
268 	strcpy(tr.authdom, s->dom);
269 
270 	if(strlen(user) >= sizeof tr.uid){
271 		werrstr("user name too long");
272 		return -1;
273 	}
274 	strcpy(tr.uid, user);
275 	convTR2M(&tr, trbuf);
276 
277 	if(xiowrite(s->asfd, trbuf, TICKREQLEN) != TICKREQLEN)
278 		return -1;
279 
280 	if((n=xioasrdresp(s->asfd, chal, challen)) <= 0)
281 		return -1;
282 	return n;
283 }
284 
285 static int
286 p9crresp(ServerState *s, uchar *resp, int resplen)
287 {
288 	char tabuf[TICKETLEN+AUTHENTLEN];
289 	Authenticator a;
290 	Ticket t;
291 	Ticketreq tr;
292 
293 	memset(&tr, 0, sizeof tr);	// TODO: what should tr be initialized to?
294 
295 	if(xiowrite(s->asfd, resp, resplen) != resplen)
296 		return -1;
297 
298 	if(xioasrdresp(s->asfd, tabuf, TICKETLEN+AUTHENTLEN) != TICKETLEN+AUTHENTLEN)
299 		return 0;
300 
301 	convM2T(tabuf, &t, s->k->priv);
302 	if(t.num != AuthTs
303 	|| memcmp(t.chal, tr.chal, sizeof tr.chal) != 0){
304 		werrstr("key mismatch with auth server");
305 		return -1;
306 	}
307 
308 	convM2A(tabuf+TICKETLEN, &a, t.key);
309 	if(a.num != AuthAc
310 	|| memcmp(a.chal, tr.chal, sizeof a.chal) != 0
311 	|| a.id != 0){
312 		werrstr("key2 mismatch with auth server");
313 		return -1;
314 	}
315 
316 	s->t = t;
317 	return 1;
318 }
319 
320 static int
321 p9response(char *pw, uchar *chal, uchar *resp)
322 {
323 	char key[DESKEYLEN];
324 	uchar buf[8];
325 	ulong x;
326 
327 	passtokey(key, pw);
328 	memset(buf, 0, 8);
329 	snprint((char*)buf, sizeof buf, "%d", atoi((char*)chal));
330 	if(encrypt(key, buf, 8) < 0){
331 		werrstr("can't encrypt response");
332 		return -1;
333 	}
334 	x = (buf[0]<<24)+(buf[1]<<16)+(buf[2]<<8)+buf[3];
335 	return snprint((char*)resp, MAXRESP, "%.8lux", x);
336 }
337 
338 /*
339 static int
340 vncresponse(char *pw, uchar *chal, uchar *resp)
341 {
342 	DESstate des;
343 
344 	memmove(resp, chal, MAXCHAL);
345 	setupDESstate(&des, 0, nil);  // XXX put key in for 0
346 	desECBencrypt(resp, MAXCHAL, &des);
347 	return MAXCHAL;
348 }
349 */
350 
351 static Role
352 p9crroles[] =
353 {
354 	"client", p9crclient,
355 	"server", p9crserver,
356 	0
357 };
358 
359 Proto p9cr = {
360 	"p9cr",
361 	p9crroles,
362 	"user? !password?",
363 	p9crcheck,
364 	nil
365 };
366 
367 /* still need to implement vnc key generator */
368 Proto vnc = {
369 	"vnc",
370 	p9crroles,
371 	"user? !password?",
372 	p9crcheck,
373 	nil
374 };