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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" | |
d77347cc | 13 | RCSID("$OpenBSD: auth1.c,v 1.59 2004/07/28 09:40:29 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" | |
42f11eb2 | 20 | #include "log.h" |
a306f2dd | 21 | #include "servconf.h" |
22 | #include "compat.h" | |
23 | #include "auth.h" | |
7899c98f | 24 | #include "channels.h" |
a306f2dd | 25 | #include "session.h" |
ced49be2 | 26 | #include "uidswap.h" |
1853d1ef | 27 | #include "monitor_wrap.h" |
9aab0af7 | 28 | #include "buffer.h" |
a306f2dd | 29 | |
30 | /* import */ | |
31 | extern ServerOptions options; | |
9aab0af7 | 32 | extern Buffer loginmsg; |
94ec8c6b | 33 | |
a306f2dd | 34 | /* |
35 | * convert ssh auth msg type into description | |
36 | */ | |
396c147e | 37 | static char * |
a306f2dd | 38 | get_authname(int type) |
39 | { | |
40 | static char buf[1024]; | |
41 | switch (type) { | |
42 | case SSH_CMSG_AUTH_PASSWORD: | |
43 | return "password"; | |
44 | case SSH_CMSG_AUTH_RSA: | |
45 | return "rsa"; | |
46 | case SSH_CMSG_AUTH_RHOSTS_RSA: | |
47 | return "rhosts-rsa"; | |
48 | case SSH_CMSG_AUTH_RHOSTS: | |
49 | return "rhosts"; | |
59c97189 | 50 | case SSH_CMSG_AUTH_TIS: |
51 | case SSH_CMSG_AUTH_TIS_RESPONSE: | |
52 | return "challenge-response"; | |
a306f2dd | 53 | } |
54 | snprintf(buf, sizeof buf, "bad-auth-msg-%d", type); | |
55 | return buf; | |
56 | } | |
57 | ||
58 | /* | |
59c97189 | 59 | * read packets, try to authenticate the user and |
60 | * return only if authentication is successful | |
a306f2dd | 61 | */ |
396c147e | 62 | static void |
59c97189 | 63 | do_authloop(Authctxt *authctxt) |
a306f2dd | 64 | { |
94ec8c6b | 65 | int authenticated = 0; |
1e3b8b07 | 66 | u_int bits; |
b775c6f2 | 67 | Key *client_host_key; |
a306f2dd | 68 | BIGNUM *n; |
94ec8c6b | 69 | char *client_user, *password; |
59c97189 | 70 | char info[1024]; |
1e3b8b07 | 71 | u_int dlen; |
1e3b8b07 | 72 | u_int ulen; |
05114c74 | 73 | int prev, type = 0; |
59c97189 | 74 | |
75 | debug("Attempting authentication for %s%.100s.", | |
d77347cc | 76 | authctxt->valid ? "" : "invalid user ", authctxt->user); |
59c97189 | 77 | |
78 | /* If the user has no password, accept authentication immediately. */ | |
79 | if (options.password_authentication && | |
1c590258 | 80 | #ifdef KRB5 |
59c97189 | 81 | (!options.kerberos_authentication || options.kerberos_or_local_passwd) && |
82 | #endif | |
1853d1ef | 83 | PRIVSEP(auth_password(authctxt, ""))) { |
ece30983 | 84 | #ifdef USE_PAM |
85 | if (options.use_pam && (PRIVSEP(do_pam_account()))) | |
86 | #endif | |
87 | { | |
88 | auth_log(authctxt, 1, "without authentication", ""); | |
89 | return; | |
90 | } | |
59c97189 | 91 | } |
a306f2dd | 92 | |
93 | /* Indicate that authentication is needed. */ | |
94 | packet_start(SSH_SMSG_FAILURE); | |
95 | packet_send(); | |
96 | packet_write_wait(); | |
97 | ||
94ec8c6b | 98 | client_user = NULL; |
99 | ||
59c97189 | 100 | for (;;) { |
94ec8c6b | 101 | /* default to fail */ |
102 | authenticated = 0; | |
103 | ||
59c97189 | 104 | info[0] = '\0'; |
a306f2dd | 105 | |
106 | /* Get a packet from the client. */ | |
05114c74 | 107 | prev = type; |
54a5250f | 108 | type = packet_read(); |
a306f2dd | 109 | |
05114c74 | 110 | /* |
111 | * If we started challenge-response authentication but the | |
112 | * next packet is not a response to our challenge, release | |
113 | * the resources allocated by get_challenge() (which would | |
114 | * normally have been released by verify_response() had we | |
115 | * received such a response) | |
116 | */ | |
117 | if (prev == SSH_CMSG_AUTH_TIS && | |
118 | type != SSH_CMSG_AUTH_TIS_RESPONSE) | |
119 | abandon_challenge_response(authctxt); | |
120 | ||
a306f2dd | 121 | /* Process the packet. */ |
122 | switch (type) { | |
a306f2dd | 123 | case SSH_CMSG_AUTH_RHOSTS_RSA: |
124 | if (!options.rhosts_rsa_authentication) { | |
125 | verbose("Rhosts with RSA authentication disabled."); | |
126 | break; | |
127 | } | |
128 | /* | |
129 | * Get client user name. Note that we just have to | |
130 | * trust the client; root on the client machine can | |
131 | * claim to be any user. | |
132 | */ | |
133 | client_user = packet_get_string(&ulen); | |
134 | ||
135 | /* Get the client host key. */ | |
b775c6f2 | 136 | client_host_key = key_new(KEY_RSA1); |
a306f2dd | 137 | bits = packet_get_int(); |
20b279e6 | 138 | packet_get_bignum(client_host_key->rsa->e); |
139 | packet_get_bignum(client_host_key->rsa->n); | |
a306f2dd | 140 | |
b775c6f2 | 141 | if (bits != BN_num_bits(client_host_key->rsa->n)) |
94ec8c6b | 142 | verbose("Warning: keysize mismatch for client_host_key: " |
b775c6f2 | 143 | "actual %d, announced %d", |
7203d6bb | 144 | BN_num_bits(client_host_key->rsa->n), bits); |
95500969 | 145 | packet_check_eom(); |
a306f2dd | 146 | |
fdaef11e | 147 | authenticated = auth_rhosts_rsa(authctxt, client_user, |
dc421aa3 | 148 | client_host_key); |
b775c6f2 | 149 | key_free(client_host_key); |
a306f2dd | 150 | |
59c97189 | 151 | snprintf(info, sizeof info, " ruser %.100s", client_user); |
a306f2dd | 152 | break; |
153 | ||
154 | case SSH_CMSG_AUTH_RSA: | |
155 | if (!options.rsa_authentication) { | |
156 | verbose("RSA authentication disabled."); | |
157 | break; | |
158 | } | |
159 | /* RSA authentication requested. */ | |
b775c6f2 | 160 | if ((n = BN_new()) == NULL) |
161 | fatal("do_authloop: BN_new failed"); | |
20b279e6 | 162 | packet_get_bignum(n); |
95500969 | 163 | packet_check_eom(); |
fdaef11e | 164 | authenticated = auth_rsa(authctxt, n); |
a306f2dd | 165 | BN_clear_free(n); |
166 | break; | |
167 | ||
168 | case SSH_CMSG_AUTH_PASSWORD: | |
169 | if (!options.password_authentication) { | |
170 | verbose("Password authentication disabled."); | |
171 | break; | |
172 | } | |
173 | /* | |
174 | * Read user password. It is in plain text, but was | |
175 | * transmitted over the encrypted channel so it is | |
176 | * not visible to an outside observer. | |
177 | */ | |
178 | password = packet_get_string(&dlen); | |
95500969 | 179 | packet_check_eom(); |
a306f2dd | 180 | |
b4b5d644 | 181 | /* Try authentication with the password. */ |
1853d1ef | 182 | authenticated = PRIVSEP(auth_password(authctxt, password)); |
a306f2dd | 183 | |
184 | memset(password, 0, strlen(password)); | |
185 | xfree(password); | |
186 | break; | |
187 | ||
a306f2dd | 188 | case SSH_CMSG_AUTH_TIS: |
189 | debug("rcvd SSH_CMSG_AUTH_TIS"); | |
5ba55ada | 190 | if (options.challenge_response_authentication == 1) { |
191 | char *challenge = get_challenge(authctxt); | |
59c97189 | 192 | if (challenge != NULL) { |
193 | debug("sending challenge '%s'", challenge); | |
a306f2dd | 194 | packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE); |
59c97189 | 195 | packet_put_cstring(challenge); |
5ba55ada | 196 | xfree(challenge); |
a306f2dd | 197 | packet_send(); |
198 | packet_write_wait(); | |
199 | continue; | |
200 | } | |
201 | } | |
202 | break; | |
203 | case SSH_CMSG_AUTH_TIS_RESPONSE: | |
204 | debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE"); | |
5ba55ada | 205 | if (options.challenge_response_authentication == 1) { |
a306f2dd | 206 | char *response = packet_get_string(&dlen); |
95500969 | 207 | packet_check_eom(); |
59c97189 | 208 | authenticated = verify_response(authctxt, response); |
209 | memset(response, 'r', dlen); | |
a306f2dd | 210 | xfree(response); |
211 | } | |
212 | break; | |
a306f2dd | 213 | |
214 | default: | |
215 | /* | |
216 | * Any unknown messages will be ignored (and failure | |
217 | * returned) during authentication. | |
218 | */ | |
bbe88b6d | 219 | logit("Unknown message during authentication: type %d", type); |
a306f2dd | 220 | break; |
221 | } | |
af774732 | 222 | #ifdef BSD_AUTH |
223 | if (authctxt->as) { | |
224 | auth_close(authctxt->as); | |
225 | authctxt->as = NULL; | |
226 | } | |
227 | #endif | |
59c97189 | 228 | if (!authctxt->valid && authenticated) |
229 | fatal("INTERNAL ERROR: authenticated invalid user %s", | |
230 | authctxt->user); | |
a306f2dd | 231 | |
ef51930f | 232 | #ifdef _UNICOS |
ef51930f | 233 | if (authenticated && cray_access_denied(authctxt->user)) { |
234 | authenticated = 0; | |
235 | fatal("Access denied for user %s.",authctxt->user); | |
236 | } | |
237 | #endif /* _UNICOS */ | |
238 | ||
2b87da3b | 239 | #ifdef HAVE_CYGWIN |
240 | if (authenticated && | |
02a57950 | 241 | !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, |
242 | authctxt->pw)) { | |
3c62e7eb | 243 | packet_disconnect("Authentication rejected for uid %d.", |
02a57950 | 244 | authctxt->pw == NULL ? -1 : authctxt->pw->pw_uid); |
3c62e7eb | 245 | authenticated = 0; |
246 | } | |
3c418020 | 247 | #else |
59c97189 | 248 | /* Special handling for root */ |
5d47f1d4 | 249 | if (authenticated && authctxt->pw->pw_uid == 0 && |
c00e4d75 | 250 | !auth_root_allowed(get_authname(type))) { |
59c97189 | 251 | authenticated = 0; |
6039eeef | 252 | # ifdef SSH_AUDIT_EVENTS |
253 | PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED)); | |
c00e4d75 | 254 | # endif |
255 | } | |
3c418020 | 256 | #endif |
a306f2dd | 257 | |
5b9e2464 | 258 | #ifdef USE_PAM |
aff51935 | 259 | if (options.use_pam && authenticated && |
9aab0af7 | 260 | !PRIVSEP(do_pam_account())) { |
261 | char *msg; | |
262 | size_t len; | |
263 | ||
264 | error("Access denied for user %s by PAM account " | |
265 | "configuration", authctxt->user); | |
266 | len = buffer_len(&loginmsg); | |
267 | buffer_append(&loginmsg, "\0", 1); | |
268 | msg = buffer_ptr(&loginmsg); | |
269 | /* strip trailing newlines */ | |
270 | if (len > 0) | |
271 | while (len > 0 && msg[--len] == '\n') | |
272 | msg[len] = '\0'; | |
273 | else | |
274 | msg = "Access denied."; | |
275 | packet_disconnect(msg); | |
276 | } | |
5b9e2464 | 277 | #endif |
278 | ||
59c97189 | 279 | /* Log before sending the reply */ |
280 | auth_log(authctxt, authenticated, get_authname(type), info); | |
281 | ||
a306f2dd | 282 | if (client_user != NULL) { |
283 | xfree(client_user); | |
284 | client_user = NULL; | |
285 | } | |
286 | ||
94ec8c6b | 287 | if (authenticated) |
288 | return; | |
289 | ||
c00e4d75 | 290 | if (authctxt->failures++ > options.max_authtries) { |
6039eeef | 291 | #ifdef SSH_AUDIT_EVENTS |
292 | PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES)); | |
c00e4d75 | 293 | #endif |
59c97189 | 294 | packet_disconnect(AUTH_FAIL_MSG, authctxt->user); |
c00e4d75 | 295 | } |
a306f2dd | 296 | |
a306f2dd | 297 | packet_start(SSH_SMSG_FAILURE); |
298 | packet_send(); | |
299 | packet_write_wait(); | |
300 | } | |
301 | } | |
302 | ||
303 | /* | |
304 | * Performs authentication of an incoming connection. Session key has already | |
305 | * been exchanged and encryption is enabled. | |
306 | */ | |
2362db19 | 307 | void |
308 | do_authentication(Authctxt *authctxt) | |
a306f2dd | 309 | { |
1e3b8b07 | 310 | u_int ulen; |
f8d99a32 | 311 | char *user, *style = NULL; |
a306f2dd | 312 | |
313 | /* Get the name of the user that we wish to log in as. */ | |
54a5250f | 314 | packet_read_expect(SSH_CMSG_USER); |
a306f2dd | 315 | |
316 | /* Get the user name. */ | |
317 | user = packet_get_string(&ulen); | |
95500969 | 318 | packet_check_eom(); |
a306f2dd | 319 | |
59c97189 | 320 | if ((style = strchr(user, ':')) != NULL) |
ced49be2 | 321 | *style++ = '\0'; |
59c97189 | 322 | |
59c97189 | 323 | authctxt->user = user; |
324 | authctxt->style = style; | |
325 | ||
a306f2dd | 326 | /* Verify that the user is a valid user. */ |
5f1f36b5 | 327 | if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL) |
59c97189 | 328 | authctxt->valid = 1; |
96d0bf74 | 329 | else { |
d77347cc | 330 | debug("do_authentication: invalid user %s", user); |
96d0bf74 | 331 | authctxt->pw = fakepw(); |
332 | } | |
a306f2dd | 333 | |
bd5c0694 | 334 | setproctitle("%s%s", authctxt->valid ? user : "unknown", |
1853d1ef | 335 | use_privsep ? " [net]" : ""); |
6172e290 | 336 | |
a306f2dd | 337 | #ifdef USE_PAM |
7fceb20d | 338 | if (options.use_pam) |
529d73ab | 339 | PRIVSEP(start_pam(authctxt)); |
a306f2dd | 340 | #endif |
341 | ||
342 | /* | |
343 | * If we are not running as root, the user must have the same uid as | |
94ec8c6b | 344 | * the server. (Unless you are running Windows) |
a306f2dd | 345 | */ |
94ec8c6b | 346 | #ifndef HAVE_CYGWIN |
5f1f36b5 | 347 | if (!use_privsep && getuid() != 0 && authctxt->pw && |
348 | authctxt->pw->pw_uid != getuid()) | |
a306f2dd | 349 | packet_disconnect("Cannot change user when server not running as root."); |
3c62e7eb | 350 | #endif |
a306f2dd | 351 | |
59c97189 | 352 | /* |
b4b5d644 | 353 | * Loop until the user has been authenticated or the connection is |
354 | * closed, do_authloop() returns only if authentication is successful | |
355 | */ | |
59c97189 | 356 | do_authloop(authctxt); |
a306f2dd | 357 | |
358 | /* The user has been authenticated and accepted. */ | |
94ec8c6b | 359 | packet_start(SSH_SMSG_SUCCESS); |
360 | packet_send(); | |
361 | packet_write_wait(); | |
a306f2dd | 362 | } |