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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" | |
20b279e6 | 13 | RCSID("$OpenBSD: auth1.c,v 1.33 2001/12/28 13:57:33 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; |
20b279e6 | 74 | int plen; |
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); |
95500969 | 123 | packet_check_eom(); |
184eed6a | 124 | |
ced49be2 | 125 | if (kdata[0] == 4) { /* KRB_PROT_VERSION */ |
126 | #ifdef KRB4 | |
127 | KTEXT_ST tkt; | |
184eed6a | 128 | |
ced49be2 | 129 | tkt.length = dlen; |
130 | if (tkt.length < MAX_KTXT_LEN) | |
131 | memcpy(tkt.dat, kdata, tkt.length); | |
184eed6a | 132 | |
ced49be2 | 133 | if (auth_krb4(authctxt, &tkt, &client_user)) { |
134 | authenticated = 1; | |
135 | snprintf(info, sizeof(info), | |
136 | " tktuser %.100s", | |
137 | client_user); | |
94ec8c6b | 138 | } |
ced49be2 | 139 | #endif /* KRB4 */ |
140 | } else { | |
141 | #ifdef KRB5 | |
142 | krb5_data tkt; | |
143 | tkt.length = dlen; | |
144 | tkt.data = kdata; | |
184eed6a | 145 | |
ced49be2 | 146 | if (auth_krb5(authctxt, &tkt, &client_user)) { |
147 | authenticated = 1; | |
148 | snprintf(info, sizeof(info), | |
149 | " tktuser %.100s", | |
150 | client_user); | |
ced49be2 | 151 | } |
152 | #endif /* KRB5 */ | |
a306f2dd | 153 | } |
59c97189 | 154 | xfree(kdata); |
a306f2dd | 155 | } |
156 | break; | |
ced49be2 | 157 | #endif /* KRB4 || KRB5 */ |
184eed6a | 158 | |
ced49be2 | 159 | #if defined(AFS) || defined(KRB5) |
160 | /* XXX - punt on backward compatibility here. */ | |
161 | case SSH_CMSG_HAVE_KERBEROS_TGT: | |
162 | packet_send_debug("Kerberos TGT passing disabled before authentication."); | |
163 | break; | |
164 | #ifdef AFS | |
165 | case SSH_CMSG_HAVE_AFS_TOKEN: | |
166 | packet_send_debug("AFS token passing disabled before authentication."); | |
167 | break; | |
168 | #endif /* AFS */ | |
169 | #endif /* AFS || KRB5 */ | |
184eed6a | 170 | |
a306f2dd | 171 | case SSH_CMSG_AUTH_RHOSTS: |
172 | if (!options.rhosts_authentication) { | |
173 | verbose("Rhosts authentication disabled."); | |
174 | break; | |
175 | } | |
176 | /* | |
177 | * Get client user name. Note that we just have to | |
178 | * trust the client; this is one reason why rhosts | |
179 | * authentication is insecure. (Another is | |
180 | * IP-spoofing on a local network.) | |
181 | */ | |
182 | client_user = packet_get_string(&ulen); | |
95500969 | 183 | packet_check_eom(); |
a306f2dd | 184 | |
94ec8c6b | 185 | /* Try to authenticate using /etc/hosts.equiv and .rhosts. */ |
a306f2dd | 186 | authenticated = auth_rhosts(pw, client_user); |
187 | ||
59c97189 | 188 | snprintf(info, sizeof info, " ruser %.100s", client_user); |
a306f2dd | 189 | break; |
190 | ||
191 | case SSH_CMSG_AUTH_RHOSTS_RSA: | |
192 | if (!options.rhosts_rsa_authentication) { | |
193 | verbose("Rhosts with RSA authentication disabled."); | |
194 | break; | |
195 | } | |
196 | /* | |
197 | * Get client user name. Note that we just have to | |
198 | * trust the client; root on the client machine can | |
199 | * claim to be any user. | |
200 | */ | |
201 | client_user = packet_get_string(&ulen); | |
202 | ||
203 | /* Get the client host key. */ | |
b775c6f2 | 204 | client_host_key = key_new(KEY_RSA1); |
a306f2dd | 205 | bits = packet_get_int(); |
20b279e6 | 206 | packet_get_bignum(client_host_key->rsa->e); |
207 | packet_get_bignum(client_host_key->rsa->n); | |
a306f2dd | 208 | |
b775c6f2 | 209 | if (bits != BN_num_bits(client_host_key->rsa->n)) |
94ec8c6b | 210 | verbose("Warning: keysize mismatch for client_host_key: " |
b775c6f2 | 211 | "actual %d, announced %d", |
212 | BN_num_bits(client_host_key->rsa->n), bits); | |
95500969 | 213 | packet_check_eom(); |
a306f2dd | 214 | |
b775c6f2 | 215 | authenticated = auth_rhosts_rsa(pw, client_user, |
dc421aa3 | 216 | client_host_key); |
b775c6f2 | 217 | key_free(client_host_key); |
a306f2dd | 218 | |
59c97189 | 219 | snprintf(info, sizeof info, " ruser %.100s", client_user); |
a306f2dd | 220 | break; |
221 | ||
222 | case SSH_CMSG_AUTH_RSA: | |
223 | if (!options.rsa_authentication) { | |
224 | verbose("RSA authentication disabled."); | |
225 | break; | |
226 | } | |
227 | /* RSA authentication requested. */ | |
b775c6f2 | 228 | if ((n = BN_new()) == NULL) |
229 | fatal("do_authloop: BN_new failed"); | |
20b279e6 | 230 | packet_get_bignum(n); |
95500969 | 231 | packet_check_eom(); |
a306f2dd | 232 | authenticated = auth_rsa(pw, n); |
233 | BN_clear_free(n); | |
234 | break; | |
235 | ||
236 | case SSH_CMSG_AUTH_PASSWORD: | |
237 | if (!options.password_authentication) { | |
238 | verbose("Password authentication disabled."); | |
239 | break; | |
240 | } | |
241 | /* | |
242 | * Read user password. It is in plain text, but was | |
243 | * transmitted over the encrypted channel so it is | |
244 | * not visible to an outside observer. | |
245 | */ | |
246 | password = packet_get_string(&dlen); | |
95500969 | 247 | packet_check_eom(); |
a306f2dd | 248 | |
249 | #ifdef USE_PAM | |
250 | /* Do PAM auth with password */ | |
251 | authenticated = auth_pam_password(pw, password); | |
4d33e531 | 252 | #elif defined(HAVE_OSF_SIA) |
253 | /* Do SIA auth with password */ | |
b7ccb051 | 254 | authenticated = auth_sia_password(authctxt->user, |
255 | password); | |
4d33e531 | 256 | #else /* !USE_PAM && !HAVE_OSF_SIA */ |
b4b5d644 | 257 | /* Try authentication with the password. */ |
af774732 | 258 | authenticated = auth_password(authctxt, password); |
a306f2dd | 259 | #endif /* USE_PAM */ |
260 | ||
261 | memset(password, 0, strlen(password)); | |
262 | xfree(password); | |
263 | break; | |
264 | ||
a306f2dd | 265 | case SSH_CMSG_AUTH_TIS: |
266 | debug("rcvd SSH_CMSG_AUTH_TIS"); | |
5ba55ada | 267 | if (options.challenge_response_authentication == 1) { |
268 | char *challenge = get_challenge(authctxt); | |
59c97189 | 269 | if (challenge != NULL) { |
270 | debug("sending challenge '%s'", challenge); | |
a306f2dd | 271 | packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE); |
59c97189 | 272 | packet_put_cstring(challenge); |
5ba55ada | 273 | xfree(challenge); |
a306f2dd | 274 | packet_send(); |
275 | packet_write_wait(); | |
276 | continue; | |
277 | } | |
278 | } | |
279 | break; | |
280 | case SSH_CMSG_AUTH_TIS_RESPONSE: | |
281 | debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE"); | |
5ba55ada | 282 | if (options.challenge_response_authentication == 1) { |
a306f2dd | 283 | char *response = packet_get_string(&dlen); |
59c97189 | 284 | debug("got response '%s'", response); |
95500969 | 285 | packet_check_eom(); |
59c97189 | 286 | authenticated = verify_response(authctxt, response); |
287 | memset(response, 'r', dlen); | |
a306f2dd | 288 | xfree(response); |
289 | } | |
290 | break; | |
a306f2dd | 291 | |
292 | default: | |
293 | /* | |
294 | * Any unknown messages will be ignored (and failure | |
295 | * returned) during authentication. | |
296 | */ | |
297 | log("Unknown message during authentication: type %d", type); | |
298 | break; | |
299 | } | |
af774732 | 300 | #ifdef BSD_AUTH |
301 | if (authctxt->as) { | |
302 | auth_close(authctxt->as); | |
303 | authctxt->as = NULL; | |
304 | } | |
305 | #endif | |
59c97189 | 306 | if (!authctxt->valid && authenticated) |
307 | fatal("INTERNAL ERROR: authenticated invalid user %s", | |
308 | authctxt->user); | |
a306f2dd | 309 | |
2b87da3b | 310 | #ifdef HAVE_CYGWIN |
311 | if (authenticated && | |
e9571a2c | 312 | !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, pw)) { |
3c62e7eb | 313 | packet_disconnect("Authentication rejected for uid %d.", |
e9571a2c | 314 | pw == NULL ? -1 : pw->pw_uid); |
3c62e7eb | 315 | authenticated = 0; |
316 | } | |
3c418020 | 317 | #else |
59c97189 | 318 | /* Special handling for root */ |
15853e93 | 319 | if (authenticated && authctxt->pw->pw_uid == 0 && |
320 | !auth_root_allowed(get_authname(type))) | |
59c97189 | 321 | authenticated = 0; |
3c418020 | 322 | #endif |
2b87da3b | 323 | #ifdef USE_PAM |
94ec8c6b | 324 | if (authenticated && !do_pam_account(pw->pw_name, client_user)) |
325 | authenticated = 0; | |
326 | #endif | |
a306f2dd | 327 | |
59c97189 | 328 | /* Log before sending the reply */ |
329 | auth_log(authctxt, authenticated, get_authname(type), info); | |
330 | ||
a306f2dd | 331 | if (client_user != NULL) { |
332 | xfree(client_user); | |
333 | client_user = NULL; | |
334 | } | |
335 | ||
94ec8c6b | 336 | if (authenticated) |
337 | return; | |
338 | ||
b4b5d644 | 339 | if (authctxt->failures++ > AUTH_FAIL_MAX) { |
2b87da3b | 340 | #ifdef WITH_AIXAUTHENTICATE |
341 | loginfailed(authctxt->user, | |
342 | get_canonical_hostname(options.reverse_mapping_check), | |
61e96248 | 343 | "ssh"); |
c1ef8333 | 344 | #endif /* WITH_AIXAUTHENTICATE */ |
59c97189 | 345 | packet_disconnect(AUTH_FAIL_MSG, authctxt->user); |
c1ef8333 | 346 | } |
a306f2dd | 347 | |
a306f2dd | 348 | packet_start(SSH_SMSG_FAILURE); |
349 | packet_send(); | |
350 | packet_write_wait(); | |
351 | } | |
352 | } | |
353 | ||
354 | /* | |
355 | * Performs authentication of an incoming connection. Session key has already | |
356 | * been exchanged and encryption is enabled. | |
357 | */ | |
358 | void | |
d5bb9418 | 359 | do_authentication(void) |
a306f2dd | 360 | { |
59c97189 | 361 | Authctxt *authctxt; |
362 | struct passwd *pw; | |
a306f2dd | 363 | int plen; |
1e3b8b07 | 364 | u_int ulen; |
ced49be2 | 365 | char *p, *user, *style = NULL; |
a306f2dd | 366 | |
367 | /* Get the name of the user that we wish to log in as. */ | |
368 | packet_read_expect(&plen, SSH_CMSG_USER); | |
369 | ||
370 | /* Get the user name. */ | |
371 | user = packet_get_string(&ulen); | |
95500969 | 372 | packet_check_eom(); |
a306f2dd | 373 | |
59c97189 | 374 | if ((style = strchr(user, ':')) != NULL) |
ced49be2 | 375 | *style++ = '\0'; |
59c97189 | 376 | |
ced49be2 | 377 | /* XXX - SSH.com Kerberos v5 braindeath. */ |
378 | if ((p = strchr(user, '@')) != NULL) | |
379 | *p = '\0'; | |
184eed6a | 380 | |
59c97189 | 381 | authctxt = authctxt_new(); |
382 | authctxt->user = user; | |
383 | authctxt->style = style; | |
384 | ||
a306f2dd | 385 | /* Verify that the user is a valid user. */ |
386 | pw = getpwnam(user); | |
94ec8c6b | 387 | if (pw && allowed_user(pw)) { |
59c97189 | 388 | authctxt->valid = 1; |
389 | pw = pwcopy(pw); | |
94ec8c6b | 390 | } else { |
59c97189 | 391 | debug("do_authentication: illegal user %s", user); |
94ec8c6b | 392 | pw = NULL; |
393 | } | |
59c97189 | 394 | authctxt->pw = pw; |
a306f2dd | 395 | |
6172e290 | 396 | setproctitle("%s", pw ? user : "unknown"); |
397 | ||
a306f2dd | 398 | #ifdef USE_PAM |
94ec8c6b | 399 | if (pw) |
04fc7a67 | 400 | start_pam(user); |
a306f2dd | 401 | #endif |
402 | ||
403 | /* | |
404 | * If we are not running as root, the user must have the same uid as | |
94ec8c6b | 405 | * the server. (Unless you are running Windows) |
a306f2dd | 406 | */ |
94ec8c6b | 407 | #ifndef HAVE_CYGWIN |
408 | if (getuid() != 0 && pw && pw->pw_uid != getuid()) | |
a306f2dd | 409 | packet_disconnect("Cannot change user when server not running as root."); |
3c62e7eb | 410 | #endif |
a306f2dd | 411 | |
59c97189 | 412 | /* |
b4b5d644 | 413 | * Loop until the user has been authenticated or the connection is |
414 | * closed, do_authloop() returns only if authentication is successful | |
415 | */ | |
59c97189 | 416 | do_authloop(authctxt); |
a306f2dd | 417 | |
418 | /* The user has been authenticated and accepted. */ | |
94ec8c6b | 419 | packet_start(SSH_SMSG_SUCCESS); |
420 | packet_send(); | |
421 | packet_write_wait(); | |
59c97189 | 422 | |
a306f2dd | 423 | /* Perform session preparation. */ |
bb5639fe | 424 | do_authenticated(authctxt); |
a306f2dd | 425 | } |