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a306f2dd | 1 | /* |
2 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
3 | * All rights reserved | |
bcbf86ec | 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". | |
a306f2dd | 10 | */ |
11 | ||
12 | #include "includes.h" | |
b775c6f2 | 13 | RCSID("$OpenBSD: auth1.c,v 1.29 2001/12/27 18:22:16 markus Exp $"); |
94ec8c6b | 14 | |
a306f2dd | 15 | #include "xmalloc.h" |
16 | #include "rsa.h" | |
42f11eb2 | 17 | #include "ssh1.h" |
a306f2dd | 18 | #include "packet.h" |
19 | #include "buffer.h" | |
a306f2dd | 20 | #include "mpaux.h" |
42f11eb2 | 21 | #include "log.h" |
a306f2dd | 22 | #include "servconf.h" |
23 | #include "compat.h" | |
24 | #include "auth.h" | |
25 | #include "session.h" | |
3b1a83df | 26 | #include "misc.h" |
ced49be2 | 27 | #include "uidswap.h" |
a306f2dd | 28 | |
29 | /* import */ | |
30 | extern ServerOptions options; | |
94ec8c6b | 31 | |
a306f2dd | 32 | /* |
33 | * convert ssh auth msg type into description | |
34 | */ | |
396c147e | 35 | static char * |
a306f2dd | 36 | get_authname(int type) |
37 | { | |
38 | static char buf[1024]; | |
39 | switch (type) { | |
40 | case SSH_CMSG_AUTH_PASSWORD: | |
41 | return "password"; | |
42 | case SSH_CMSG_AUTH_RSA: | |
43 | return "rsa"; | |
44 | case SSH_CMSG_AUTH_RHOSTS_RSA: | |
45 | return "rhosts-rsa"; | |
46 | case SSH_CMSG_AUTH_RHOSTS: | |
47 | return "rhosts"; | |
59c97189 | 48 | case SSH_CMSG_AUTH_TIS: |
49 | case SSH_CMSG_AUTH_TIS_RESPONSE: | |
50 | return "challenge-response"; | |
ced49be2 | 51 | #if defined(KRB4) || defined(KRB5) |
a306f2dd | 52 | case SSH_CMSG_AUTH_KERBEROS: |
53 | return "kerberos"; | |
a306f2dd | 54 | #endif |
55 | } | |
56 | snprintf(buf, sizeof buf, "bad-auth-msg-%d", type); | |
57 | return buf; | |
58 | } | |
59 | ||
60 | /* | |
59c97189 | 61 | * read packets, try to authenticate the user and |
62 | * return only if authentication is successful | |
a306f2dd | 63 | */ |
396c147e | 64 | static void |
59c97189 | 65 | do_authloop(Authctxt *authctxt) |
a306f2dd | 66 | { |
94ec8c6b | 67 | int authenticated = 0; |
1e3b8b07 | 68 | u_int bits; |
b775c6f2 | 69 | Key *client_host_key; |
a306f2dd | 70 | BIGNUM *n; |
94ec8c6b | 71 | char *client_user, *password; |
59c97189 | 72 | char info[1024]; |
1e3b8b07 | 73 | u_int dlen; |
a306f2dd | 74 | int plen, nlen, elen; |
1e3b8b07 | 75 | u_int ulen; |
a306f2dd | 76 | int type = 0; |
59c97189 | 77 | struct passwd *pw = authctxt->pw; |
78 | ||
79 | debug("Attempting authentication for %s%.100s.", | |
184eed6a | 80 | authctxt->valid ? "" : "illegal user ", authctxt->user); |
59c97189 | 81 | |
82 | /* If the user has no password, accept authentication immediately. */ | |
83 | if (options.password_authentication && | |
ced49be2 | 84 | #if defined(KRB4) || defined(KRB5) |
59c97189 | 85 | (!options.kerberos_authentication || options.kerberos_or_local_passwd) && |
86 | #endif | |
f4ebf0e8 | 87 | #ifdef USE_PAM |
8d60e965 | 88 | auth_pam_password(pw, "")) { |
b7ccb051 | 89 | #elif defined(HAVE_OSF_SIA) |
90 | 0) { | |
59c97189 | 91 | #else |
af774732 | 92 | auth_password(authctxt, "")) { |
59c97189 | 93 | #endif |
94 | auth_log(authctxt, 1, "without authentication", ""); | |
95 | return; | |
96 | } | |
a306f2dd | 97 | |
98 | /* Indicate that authentication is needed. */ | |
99 | packet_start(SSH_SMSG_FAILURE); | |
100 | packet_send(); | |
101 | packet_write_wait(); | |
102 | ||
94ec8c6b | 103 | client_user = NULL; |
104 | ||
59c97189 | 105 | for (;;) { |
94ec8c6b | 106 | /* default to fail */ |
107 | authenticated = 0; | |
108 | ||
59c97189 | 109 | info[0] = '\0'; |
a306f2dd | 110 | |
111 | /* Get a packet from the client. */ | |
112 | type = packet_read(&plen); | |
113 | ||
114 | /* Process the packet. */ | |
115 | switch (type) { | |
a306f2dd | 116 | |
ced49be2 | 117 | #if defined(KRB4) || defined(KRB5) |
a306f2dd | 118 | case SSH_CMSG_AUTH_KERBEROS: |
119 | if (!options.kerberos_authentication) { | |
a306f2dd | 120 | verbose("Kerberos authentication disabled."); |
a306f2dd | 121 | } else { |
ced49be2 | 122 | char *kdata = packet_get_string(&dlen); |
184eed6a | 123 | |
ced49be2 | 124 | packet_integrity_check(plen, 4 + dlen, type); |
184eed6a | 125 | |
ced49be2 | 126 | if (kdata[0] == 4) { /* KRB_PROT_VERSION */ |
127 | #ifdef KRB4 | |
128 | KTEXT_ST tkt; | |
184eed6a | 129 | |
ced49be2 | 130 | tkt.length = dlen; |
131 | if (tkt.length < MAX_KTXT_LEN) | |
132 | memcpy(tkt.dat, kdata, tkt.length); | |
184eed6a | 133 | |
ced49be2 | 134 | if (auth_krb4(authctxt, &tkt, &client_user)) { |
135 | authenticated = 1; | |
136 | snprintf(info, sizeof(info), | |
137 | " tktuser %.100s", | |
138 | client_user); | |
94ec8c6b | 139 | } |
ced49be2 | 140 | #endif /* KRB4 */ |
141 | } else { | |
142 | #ifdef KRB5 | |
143 | krb5_data tkt; | |
144 | tkt.length = dlen; | |
145 | tkt.data = kdata; | |
184eed6a | 146 | |
ced49be2 | 147 | if (auth_krb5(authctxt, &tkt, &client_user)) { |
148 | authenticated = 1; | |
149 | snprintf(info, sizeof(info), | |
150 | " tktuser %.100s", | |
151 | client_user); | |
ced49be2 | 152 | } |
153 | #endif /* KRB5 */ | |
a306f2dd | 154 | } |
59c97189 | 155 | xfree(kdata); |
a306f2dd | 156 | } |
157 | break; | |
ced49be2 | 158 | #endif /* KRB4 || KRB5 */ |
184eed6a | 159 | |
ced49be2 | 160 | #if defined(AFS) || defined(KRB5) |
161 | /* XXX - punt on backward compatibility here. */ | |
162 | case SSH_CMSG_HAVE_KERBEROS_TGT: | |
163 | packet_send_debug("Kerberos TGT passing disabled before authentication."); | |
164 | break; | |
165 | #ifdef AFS | |
166 | case SSH_CMSG_HAVE_AFS_TOKEN: | |
167 | packet_send_debug("AFS token passing disabled before authentication."); | |
168 | break; | |
169 | #endif /* AFS */ | |
170 | #endif /* AFS || KRB5 */ | |
184eed6a | 171 | |
a306f2dd | 172 | case SSH_CMSG_AUTH_RHOSTS: |
173 | if (!options.rhosts_authentication) { | |
174 | verbose("Rhosts authentication disabled."); | |
175 | break; | |
176 | } | |
177 | /* | |
178 | * Get client user name. Note that we just have to | |
179 | * trust the client; this is one reason why rhosts | |
180 | * authentication is insecure. (Another is | |
181 | * IP-spoofing on a local network.) | |
182 | */ | |
183 | client_user = packet_get_string(&ulen); | |
184 | packet_integrity_check(plen, 4 + ulen, type); | |
185 | ||
94ec8c6b | 186 | /* Try to authenticate using /etc/hosts.equiv and .rhosts. */ |
a306f2dd | 187 | authenticated = auth_rhosts(pw, client_user); |
188 | ||
59c97189 | 189 | snprintf(info, sizeof info, " ruser %.100s", client_user); |
a306f2dd | 190 | break; |
191 | ||
192 | case SSH_CMSG_AUTH_RHOSTS_RSA: | |
193 | if (!options.rhosts_rsa_authentication) { | |
194 | verbose("Rhosts with RSA authentication disabled."); | |
195 | break; | |
196 | } | |
197 | /* | |
198 | * Get client user name. Note that we just have to | |
199 | * trust the client; root on the client machine can | |
200 | * claim to be any user. | |
201 | */ | |
202 | client_user = packet_get_string(&ulen); | |
203 | ||
204 | /* Get the client host key. */ | |
b775c6f2 | 205 | client_host_key = key_new(KEY_RSA1); |
a306f2dd | 206 | bits = packet_get_int(); |
b775c6f2 | 207 | packet_get_bignum(client_host_key->rsa->e, &elen); |
208 | packet_get_bignum(client_host_key->rsa->n, &nlen); | |
a306f2dd | 209 | |
b775c6f2 | 210 | if (bits != BN_num_bits(client_host_key->rsa->n)) |
94ec8c6b | 211 | verbose("Warning: keysize mismatch for client_host_key: " |
b775c6f2 | 212 | "actual %d, announced %d", |
213 | BN_num_bits(client_host_key->rsa->n), bits); | |
a306f2dd | 214 | packet_integrity_check(plen, (4 + ulen) + 4 + elen + nlen, type); |
215 | ||
b775c6f2 | 216 | authenticated = auth_rhosts_rsa(pw, client_user, |
217 | client_host_key->rsa); | |
218 | key_free(client_host_key); | |
a306f2dd | 219 | |
59c97189 | 220 | snprintf(info, sizeof info, " ruser %.100s", client_user); |
a306f2dd | 221 | break; |
222 | ||
223 | case SSH_CMSG_AUTH_RSA: | |
224 | if (!options.rsa_authentication) { | |
225 | verbose("RSA authentication disabled."); | |
226 | break; | |
227 | } | |
228 | /* RSA authentication requested. */ | |
b775c6f2 | 229 | if ((n = BN_new()) == NULL) |
230 | fatal("do_authloop: BN_new failed"); | |
a306f2dd | 231 | packet_get_bignum(n, &nlen); |
232 | packet_integrity_check(plen, nlen, type); | |
233 | authenticated = auth_rsa(pw, n); | |
234 | BN_clear_free(n); | |
235 | break; | |
236 | ||
237 | case SSH_CMSG_AUTH_PASSWORD: | |
238 | if (!options.password_authentication) { | |
239 | verbose("Password authentication disabled."); | |
240 | break; | |
241 | } | |
242 | /* | |
243 | * Read user password. It is in plain text, but was | |
244 | * transmitted over the encrypted channel so it is | |
245 | * not visible to an outside observer. | |
246 | */ | |
247 | password = packet_get_string(&dlen); | |
248 | packet_integrity_check(plen, 4 + dlen, type); | |
249 | ||
250 | #ifdef USE_PAM | |
251 | /* Do PAM auth with password */ | |
252 | authenticated = auth_pam_password(pw, password); | |
4d33e531 | 253 | #elif defined(HAVE_OSF_SIA) |
254 | /* Do SIA auth with password */ | |
b7ccb051 | 255 | authenticated = auth_sia_password(authctxt->user, |
256 | password); | |
4d33e531 | 257 | #else /* !USE_PAM && !HAVE_OSF_SIA */ |
b4b5d644 | 258 | /* Try authentication with the password. */ |
af774732 | 259 | authenticated = auth_password(authctxt, password); |
a306f2dd | 260 | #endif /* USE_PAM */ |
261 | ||
262 | memset(password, 0, strlen(password)); | |
263 | xfree(password); | |
264 | break; | |
265 | ||
a306f2dd | 266 | case SSH_CMSG_AUTH_TIS: |
267 | debug("rcvd SSH_CMSG_AUTH_TIS"); | |
5ba55ada | 268 | if (options.challenge_response_authentication == 1) { |
269 | char *challenge = get_challenge(authctxt); | |
59c97189 | 270 | if (challenge != NULL) { |
271 | debug("sending challenge '%s'", challenge); | |
a306f2dd | 272 | packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE); |
59c97189 | 273 | packet_put_cstring(challenge); |
5ba55ada | 274 | xfree(challenge); |
a306f2dd | 275 | packet_send(); |
276 | packet_write_wait(); | |
277 | continue; | |
278 | } | |
279 | } | |
280 | break; | |
281 | case SSH_CMSG_AUTH_TIS_RESPONSE: | |
282 | debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE"); | |
5ba55ada | 283 | if (options.challenge_response_authentication == 1) { |
a306f2dd | 284 | char *response = packet_get_string(&dlen); |
59c97189 | 285 | debug("got response '%s'", response); |
a306f2dd | 286 | packet_integrity_check(plen, 4 + dlen, type); |
59c97189 | 287 | authenticated = verify_response(authctxt, response); |
288 | memset(response, 'r', dlen); | |
a306f2dd | 289 | xfree(response); |
290 | } | |
291 | break; | |
a306f2dd | 292 | |
293 | default: | |
294 | /* | |
295 | * Any unknown messages will be ignored (and failure | |
296 | * returned) during authentication. | |
297 | */ | |
298 | log("Unknown message during authentication: type %d", type); | |
299 | break; | |
300 | } | |
af774732 | 301 | #ifdef BSD_AUTH |
302 | if (authctxt->as) { | |
303 | auth_close(authctxt->as); | |
304 | authctxt->as = NULL; | |
305 | } | |
306 | #endif | |
59c97189 | 307 | if (!authctxt->valid && authenticated) |
308 | fatal("INTERNAL ERROR: authenticated invalid user %s", | |
309 | authctxt->user); | |
a306f2dd | 310 | |
2b87da3b | 311 | #ifdef HAVE_CYGWIN |
312 | if (authenticated && | |
e9571a2c | 313 | !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, pw)) { |
3c62e7eb | 314 | packet_disconnect("Authentication rejected for uid %d.", |
e9571a2c | 315 | pw == NULL ? -1 : pw->pw_uid); |
3c62e7eb | 316 | authenticated = 0; |
317 | } | |
3c418020 | 318 | #else |
59c97189 | 319 | /* Special handling for root */ |
15853e93 | 320 | if (authenticated && authctxt->pw->pw_uid == 0 && |
321 | !auth_root_allowed(get_authname(type))) | |
59c97189 | 322 | authenticated = 0; |
3c418020 | 323 | #endif |
2b87da3b | 324 | #ifdef USE_PAM |
94ec8c6b | 325 | if (authenticated && !do_pam_account(pw->pw_name, client_user)) |
326 | authenticated = 0; | |
327 | #endif | |
a306f2dd | 328 | |
59c97189 | 329 | /* Log before sending the reply */ |
330 | auth_log(authctxt, authenticated, get_authname(type), info); | |
331 | ||
a306f2dd | 332 | if (client_user != NULL) { |
333 | xfree(client_user); | |
334 | client_user = NULL; | |
335 | } | |
336 | ||
94ec8c6b | 337 | if (authenticated) |
338 | return; | |
339 | ||
b4b5d644 | 340 | if (authctxt->failures++ > AUTH_FAIL_MAX) { |
2b87da3b | 341 | #ifdef WITH_AIXAUTHENTICATE |
342 | loginfailed(authctxt->user, | |
343 | get_canonical_hostname(options.reverse_mapping_check), | |
61e96248 | 344 | "ssh"); |
c1ef8333 | 345 | #endif /* WITH_AIXAUTHENTICATE */ |
59c97189 | 346 | packet_disconnect(AUTH_FAIL_MSG, authctxt->user); |
c1ef8333 | 347 | } |
a306f2dd | 348 | |
a306f2dd | 349 | packet_start(SSH_SMSG_FAILURE); |
350 | packet_send(); | |
351 | packet_write_wait(); | |
352 | } | |
353 | } | |
354 | ||
355 | /* | |
356 | * Performs authentication of an incoming connection. Session key has already | |
357 | * been exchanged and encryption is enabled. | |
358 | */ | |
359 | void | |
d5bb9418 | 360 | do_authentication(void) |
a306f2dd | 361 | { |
59c97189 | 362 | Authctxt *authctxt; |
363 | struct passwd *pw; | |
a306f2dd | 364 | int plen; |
1e3b8b07 | 365 | u_int ulen; |
ced49be2 | 366 | char *p, *user, *style = NULL; |
a306f2dd | 367 | |
368 | /* Get the name of the user that we wish to log in as. */ | |
369 | packet_read_expect(&plen, SSH_CMSG_USER); | |
370 | ||
371 | /* Get the user name. */ | |
372 | user = packet_get_string(&ulen); | |
373 | packet_integrity_check(plen, (4 + ulen), SSH_CMSG_USER); | |
374 | ||
59c97189 | 375 | if ((style = strchr(user, ':')) != NULL) |
ced49be2 | 376 | *style++ = '\0'; |
59c97189 | 377 | |
ced49be2 | 378 | /* XXX - SSH.com Kerberos v5 braindeath. */ |
379 | if ((p = strchr(user, '@')) != NULL) | |
380 | *p = '\0'; | |
184eed6a | 381 | |
59c97189 | 382 | authctxt = authctxt_new(); |
383 | authctxt->user = user; | |
384 | authctxt->style = style; | |
385 | ||
a306f2dd | 386 | /* Verify that the user is a valid user. */ |
387 | pw = getpwnam(user); | |
94ec8c6b | 388 | if (pw && allowed_user(pw)) { |
59c97189 | 389 | authctxt->valid = 1; |
390 | pw = pwcopy(pw); | |
94ec8c6b | 391 | } else { |
59c97189 | 392 | debug("do_authentication: illegal user %s", user); |
94ec8c6b | 393 | pw = NULL; |
394 | } | |
59c97189 | 395 | authctxt->pw = pw; |
a306f2dd | 396 | |
6172e290 | 397 | setproctitle("%s", pw ? user : "unknown"); |
398 | ||
a306f2dd | 399 | #ifdef USE_PAM |
94ec8c6b | 400 | if (pw) |
04fc7a67 | 401 | start_pam(user); |
a306f2dd | 402 | #endif |
403 | ||
404 | /* | |
405 | * If we are not running as root, the user must have the same uid as | |
94ec8c6b | 406 | * the server. (Unless you are running Windows) |
a306f2dd | 407 | */ |
94ec8c6b | 408 | #ifndef HAVE_CYGWIN |
409 | if (getuid() != 0 && pw && pw->pw_uid != getuid()) | |
a306f2dd | 410 | packet_disconnect("Cannot change user when server not running as root."); |
3c62e7eb | 411 | #endif |
a306f2dd | 412 | |
59c97189 | 413 | /* |
b4b5d644 | 414 | * Loop until the user has been authenticated or the connection is |
415 | * closed, do_authloop() returns only if authentication is successful | |
416 | */ | |
59c97189 | 417 | do_authloop(authctxt); |
a306f2dd | 418 | |
419 | /* The user has been authenticated and accepted. */ | |
94ec8c6b | 420 | packet_start(SSH_SMSG_SUCCESS); |
421 | packet_send(); | |
422 | packet_write_wait(); | |
59c97189 | 423 | |
a306f2dd | 424 | /* Perform session preparation. */ |
bb5639fe | 425 | do_authenticated(authctxt); |
a306f2dd | 426 | } |