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1 | /* | |
2 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
3 | * All rights reserved | |
4 | * | |
5 | * As far as I am concerned, the code I have written for this software | |
6 | * can be used freely for any purpose. Any derived versions of this | |
7 | * software must be clearly marked as such, and if the derived work is | |
8 | * incompatible with the protocol description in the RFC file, it must be | |
9 | * called by a name other than "ssh" or "Secure Shell". | |
10 | */ | |
11 | ||
12 | #include "includes.h" | |
13 | RCSID("$OpenBSD: auth1.c,v 1.55 2003/11/08 16:02:40 jakob Exp $"); | |
14 | ||
15 | #include "xmalloc.h" | |
16 | #include "rsa.h" | |
17 | #include "ssh1.h" | |
18 | #include "packet.h" | |
19 | #include "buffer.h" | |
20 | #include "mpaux.h" | |
21 | #include "log.h" | |
22 | #include "servconf.h" | |
23 | #include "compat.h" | |
24 | #include "auth.h" | |
25 | #include "channels.h" | |
26 | #include "session.h" | |
27 | #include "uidswap.h" | |
28 | #include "monitor_wrap.h" | |
29 | ||
30 | /* import */ | |
31 | extern ServerOptions options; | |
32 | ||
33 | /* | |
34 | * convert ssh auth msg type into description | |
35 | */ | |
36 | static char * | |
37 | get_authname(int type) | |
38 | { | |
39 | static char buf[1024]; | |
40 | switch (type) { | |
41 | case SSH_CMSG_AUTH_PASSWORD: | |
42 | return "password"; | |
43 | case SSH_CMSG_AUTH_RSA: | |
44 | return "rsa"; | |
45 | case SSH_CMSG_AUTH_RHOSTS_RSA: | |
46 | return "rhosts-rsa"; | |
47 | case SSH_CMSG_AUTH_RHOSTS: | |
48 | return "rhosts"; | |
49 | case SSH_CMSG_AUTH_TIS: | |
50 | case SSH_CMSG_AUTH_TIS_RESPONSE: | |
51 | return "challenge-response"; | |
52 | } | |
53 | snprintf(buf, sizeof buf, "bad-auth-msg-%d", type); | |
54 | return buf; | |
55 | } | |
56 | ||
57 | /* | |
58 | * read packets, try to authenticate the user and | |
59 | * return only if authentication is successful | |
60 | */ | |
61 | static void | |
62 | do_authloop(Authctxt *authctxt) | |
63 | { | |
64 | int authenticated = 0; | |
65 | u_int bits; | |
66 | Key *client_host_key; | |
67 | BIGNUM *n; | |
68 | char *client_user, *password; | |
69 | char info[1024]; | |
70 | u_int dlen; | |
71 | u_int ulen; | |
72 | int prev, type = 0; | |
73 | struct passwd *pw = authctxt->pw; | |
74 | ||
75 | debug("Attempting authentication for %s%.100s.", | |
76 | authctxt->valid ? "" : "illegal user ", authctxt->user); | |
77 | ||
78 | /* If the user has no password, accept authentication immediately. */ | |
79 | if (options.password_authentication && | |
80 | #ifdef KRB5 | |
81 | (!options.kerberos_authentication || options.kerberos_or_local_passwd) && | |
82 | #endif | |
83 | PRIVSEP(auth_password(authctxt, ""))) { | |
84 | auth_log(authctxt, 1, "without authentication", ""); | |
85 | return; | |
86 | } | |
87 | ||
88 | /* Indicate that authentication is needed. */ | |
89 | packet_start(SSH_SMSG_FAILURE); | |
90 | packet_send(); | |
91 | packet_write_wait(); | |
92 | ||
93 | client_user = NULL; | |
94 | ||
95 | for (;;) { | |
96 | /* default to fail */ | |
97 | authenticated = 0; | |
98 | ||
99 | info[0] = '\0'; | |
100 | ||
101 | /* Get a packet from the client. */ | |
102 | prev = type; | |
103 | type = packet_read(); | |
104 | ||
105 | /* | |
106 | * If we started challenge-response authentication but the | |
107 | * next packet is not a response to our challenge, release | |
108 | * the resources allocated by get_challenge() (which would | |
109 | * normally have been released by verify_response() had we | |
110 | * received such a response) | |
111 | */ | |
112 | if (prev == SSH_CMSG_AUTH_TIS && | |
113 | type != SSH_CMSG_AUTH_TIS_RESPONSE) | |
114 | abandon_challenge_response(authctxt); | |
115 | ||
116 | /* Process the packet. */ | |
117 | switch (type) { | |
118 | case SSH_CMSG_AUTH_RHOSTS_RSA: | |
119 | if (!options.rhosts_rsa_authentication) { | |
120 | verbose("Rhosts with RSA authentication disabled."); | |
121 | break; | |
122 | } | |
123 | /* | |
124 | * Get client user name. Note that we just have to | |
125 | * trust the client; root on the client machine can | |
126 | * claim to be any user. | |
127 | */ | |
128 | client_user = packet_get_string(&ulen); | |
129 | ||
130 | /* Get the client host key. */ | |
131 | client_host_key = key_new(KEY_RSA1); | |
132 | bits = packet_get_int(); | |
133 | packet_get_bignum(client_host_key->rsa->e); | |
134 | packet_get_bignum(client_host_key->rsa->n); | |
135 | ||
136 | if (bits != BN_num_bits(client_host_key->rsa->n)) | |
137 | verbose("Warning: keysize mismatch for client_host_key: " | |
138 | "actual %d, announced %d", | |
139 | BN_num_bits(client_host_key->rsa->n), bits); | |
140 | packet_check_eom(); | |
141 | ||
142 | authenticated = auth_rhosts_rsa(authctxt, client_user, | |
143 | client_host_key); | |
144 | key_free(client_host_key); | |
145 | ||
146 | snprintf(info, sizeof info, " ruser %.100s", client_user); | |
147 | break; | |
148 | ||
149 | case SSH_CMSG_AUTH_RSA: | |
150 | if (!options.rsa_authentication) { | |
151 | verbose("RSA authentication disabled."); | |
152 | break; | |
153 | } | |
154 | /* RSA authentication requested. */ | |
155 | if ((n = BN_new()) == NULL) | |
156 | fatal("do_authloop: BN_new failed"); | |
157 | packet_get_bignum(n); | |
158 | packet_check_eom(); | |
159 | authenticated = auth_rsa(authctxt, n); | |
160 | BN_clear_free(n); | |
161 | break; | |
162 | ||
163 | case SSH_CMSG_AUTH_PASSWORD: | |
164 | if (!options.password_authentication) { | |
165 | verbose("Password authentication disabled."); | |
166 | break; | |
167 | } | |
168 | /* | |
169 | * Read user password. It is in plain text, but was | |
170 | * transmitted over the encrypted channel so it is | |
171 | * not visible to an outside observer. | |
172 | */ | |
173 | password = packet_get_string(&dlen); | |
174 | packet_check_eom(); | |
175 | ||
176 | /* Try authentication with the password. */ | |
177 | authenticated = PRIVSEP(auth_password(authctxt, password)); | |
178 | ||
179 | memset(password, 0, strlen(password)); | |
180 | xfree(password); | |
181 | break; | |
182 | ||
183 | case SSH_CMSG_AUTH_TIS: | |
184 | debug("rcvd SSH_CMSG_AUTH_TIS"); | |
185 | if (options.challenge_response_authentication == 1) { | |
186 | char *challenge = get_challenge(authctxt); | |
187 | if (challenge != NULL) { | |
188 | debug("sending challenge '%s'", challenge); | |
189 | packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE); | |
190 | packet_put_cstring(challenge); | |
191 | xfree(challenge); | |
192 | packet_send(); | |
193 | packet_write_wait(); | |
194 | continue; | |
195 | } | |
196 | } | |
197 | break; | |
198 | case SSH_CMSG_AUTH_TIS_RESPONSE: | |
199 | debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE"); | |
200 | if (options.challenge_response_authentication == 1) { | |
201 | char *response = packet_get_string(&dlen); | |
202 | packet_check_eom(); | |
203 | authenticated = verify_response(authctxt, response); | |
204 | memset(response, 'r', dlen); | |
205 | xfree(response); | |
206 | } | |
207 | break; | |
208 | ||
209 | default: | |
210 | /* | |
211 | * Any unknown messages will be ignored (and failure | |
212 | * returned) during authentication. | |
213 | */ | |
214 | logit("Unknown message during authentication: type %d", type); | |
215 | break; | |
216 | } | |
217 | #ifdef BSD_AUTH | |
218 | if (authctxt->as) { | |
219 | auth_close(authctxt->as); | |
220 | authctxt->as = NULL; | |
221 | } | |
222 | #endif | |
223 | if (!authctxt->valid && authenticated) | |
224 | fatal("INTERNAL ERROR: authenticated invalid user %s", | |
225 | authctxt->user); | |
226 | ||
227 | #ifdef _UNICOS | |
228 | if (authenticated && cray_access_denied(authctxt->user)) { | |
229 | authenticated = 0; | |
230 | fatal("Access denied for user %s.",authctxt->user); | |
231 | } | |
232 | #endif /* _UNICOS */ | |
233 | ||
234 | #ifdef HAVE_CYGWIN | |
235 | if (authenticated && | |
236 | !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, pw)) { | |
237 | packet_disconnect("Authentication rejected for uid %d.", | |
238 | pw == NULL ? -1 : pw->pw_uid); | |
239 | authenticated = 0; | |
240 | } | |
241 | #else | |
242 | /* Special handling for root */ | |
243 | if (authenticated && authctxt->pw->pw_uid == 0 && | |
244 | !auth_root_allowed(get_authname(type))) | |
245 | authenticated = 0; | |
246 | #endif | |
247 | ||
248 | #ifdef USE_PAM | |
249 | if (options.use_pam && authenticated && | |
250 | !PRIVSEP(do_pam_account())) | |
251 | authenticated = 0; | |
252 | #endif | |
253 | ||
254 | /* Log before sending the reply */ | |
255 | auth_log(authctxt, authenticated, get_authname(type), info); | |
256 | ||
257 | if (client_user != NULL) { | |
258 | xfree(client_user); | |
259 | client_user = NULL; | |
260 | } | |
261 | ||
262 | if (authenticated) | |
263 | return; | |
264 | ||
265 | if (authctxt->failures++ > AUTH_FAIL_MAX) | |
266 | packet_disconnect(AUTH_FAIL_MSG, authctxt->user); | |
267 | ||
268 | packet_start(SSH_SMSG_FAILURE); | |
269 | packet_send(); | |
270 | packet_write_wait(); | |
271 | } | |
272 | } | |
273 | ||
274 | /* | |
275 | * Performs authentication of an incoming connection. Session key has already | |
276 | * been exchanged and encryption is enabled. | |
277 | */ | |
278 | void | |
279 | do_authentication(Authctxt *authctxt) | |
280 | { | |
281 | u_int ulen; | |
282 | char *user, *style = NULL; | |
283 | ||
284 | /* Get the name of the user that we wish to log in as. */ | |
285 | packet_read_expect(SSH_CMSG_USER); | |
286 | ||
287 | /* Get the user name. */ | |
288 | user = packet_get_string(&ulen); | |
289 | packet_check_eom(); | |
290 | ||
291 | if ((style = strchr(user, ':')) != NULL) | |
292 | *style++ = '\0'; | |
293 | ||
294 | authctxt->user = user; | |
295 | authctxt->style = style; | |
296 | ||
297 | /* Verify that the user is a valid user. */ | |
298 | if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL) | |
299 | authctxt->valid = 1; | |
300 | else { | |
301 | debug("do_authentication: illegal user %s", user); | |
302 | authctxt->pw = fakepw(); | |
303 | } | |
304 | ||
305 | setproctitle("%s%s", authctxt->pw ? user : "unknown", | |
306 | use_privsep ? " [net]" : ""); | |
307 | ||
308 | #ifdef USE_PAM | |
309 | if (options.use_pam) | |
310 | PRIVSEP(start_pam(user)); | |
311 | #endif | |
312 | ||
313 | /* | |
314 | * If we are not running as root, the user must have the same uid as | |
315 | * the server. (Unless you are running Windows) | |
316 | */ | |
317 | #ifndef HAVE_CYGWIN | |
318 | if (!use_privsep && getuid() != 0 && authctxt->pw && | |
319 | authctxt->pw->pw_uid != getuid()) | |
320 | packet_disconnect("Cannot change user when server not running as root."); | |
321 | #endif | |
322 | ||
323 | /* | |
324 | * Loop until the user has been authenticated or the connection is | |
325 | * closed, do_authloop() returns only if authentication is successful | |
326 | */ | |
327 | do_authloop(authctxt); | |
328 | ||
329 | /* The user has been authenticated and accepted. */ | |
330 | packet_start(SSH_SMSG_SUCCESS); | |
331 | packet_send(); | |
332 | packet_write_wait(); | |
333 | } |