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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" |
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"; | |
a306f2dd | 51 | } |
52 | snprintf(buf, sizeof buf, "bad-auth-msg-%d", type); | |
53 | return buf; | |
54 | } | |
55 | ||
56 | /* | |
59c97189 | 57 | * read packets, try to authenticate the user and |
58 | * return only if authentication is successful | |
a306f2dd | 59 | */ |
396c147e | 60 | static void |
59c97189 | 61 | do_authloop(Authctxt *authctxt) |
a306f2dd | 62 | { |
94ec8c6b | 63 | int authenticated = 0; |
1e3b8b07 | 64 | u_int bits; |
b775c6f2 | 65 | Key *client_host_key; |
a306f2dd | 66 | BIGNUM *n; |
94ec8c6b | 67 | char *client_user, *password; |
59c97189 | 68 | char info[1024]; |
1e3b8b07 | 69 | u_int dlen; |
1e3b8b07 | 70 | u_int ulen; |
05114c74 | 71 | int prev, type = 0; |
59c97189 | 72 | |
73 | debug("Attempting authentication for %s%.100s.", | |
d77347cc | 74 | authctxt->valid ? "" : "invalid user ", authctxt->user); |
59c97189 | 75 | |
76 | /* If the user has no password, accept authentication immediately. */ | |
77 | if (options.password_authentication && | |
1c590258 | 78 | #ifdef KRB5 |
59c97189 | 79 | (!options.kerberos_authentication || options.kerberos_or_local_passwd) && |
80 | #endif | |
1853d1ef | 81 | PRIVSEP(auth_password(authctxt, ""))) { |
ece30983 | 82 | #ifdef USE_PAM |
83 | if (options.use_pam && (PRIVSEP(do_pam_account()))) | |
84 | #endif | |
85 | { | |
86 | auth_log(authctxt, 1, "without authentication", ""); | |
87 | return; | |
88 | } | |
59c97189 | 89 | } |
a306f2dd | 90 | |
91 | /* Indicate that authentication is needed. */ | |
92 | packet_start(SSH_SMSG_FAILURE); | |
93 | packet_send(); | |
94 | packet_write_wait(); | |
95 | ||
94ec8c6b | 96 | client_user = NULL; |
97 | ||
59c97189 | 98 | for (;;) { |
94ec8c6b | 99 | /* default to fail */ |
100 | authenticated = 0; | |
101 | ||
59c97189 | 102 | info[0] = '\0'; |
a306f2dd | 103 | |
104 | /* Get a packet from the client. */ | |
05114c74 | 105 | prev = type; |
54a5250f | 106 | type = packet_read(); |
a306f2dd | 107 | |
05114c74 | 108 | /* |
109 | * If we started challenge-response authentication but the | |
110 | * next packet is not a response to our challenge, release | |
111 | * the resources allocated by get_challenge() (which would | |
112 | * normally have been released by verify_response() had we | |
113 | * received such a response) | |
114 | */ | |
115 | if (prev == SSH_CMSG_AUTH_TIS && | |
116 | type != SSH_CMSG_AUTH_TIS_RESPONSE) | |
117 | abandon_challenge_response(authctxt); | |
118 | ||
a306f2dd | 119 | /* Process the packet. */ |
120 | switch (type) { | |
a306f2dd | 121 | case SSH_CMSG_AUTH_RHOSTS_RSA: |
122 | if (!options.rhosts_rsa_authentication) { | |
123 | verbose("Rhosts with RSA authentication disabled."); | |
124 | break; | |
125 | } | |
126 | /* | |
127 | * Get client user name. Note that we just have to | |
128 | * trust the client; root on the client machine can | |
129 | * claim to be any user. | |
130 | */ | |
131 | client_user = packet_get_string(&ulen); | |
132 | ||
133 | /* Get the client host key. */ | |
b775c6f2 | 134 | client_host_key = key_new(KEY_RSA1); |
a306f2dd | 135 | bits = packet_get_int(); |
20b279e6 | 136 | packet_get_bignum(client_host_key->rsa->e); |
137 | packet_get_bignum(client_host_key->rsa->n); | |
a306f2dd | 138 | |
b775c6f2 | 139 | if (bits != BN_num_bits(client_host_key->rsa->n)) |
94ec8c6b | 140 | verbose("Warning: keysize mismatch for client_host_key: " |
b775c6f2 | 141 | "actual %d, announced %d", |
7203d6bb | 142 | BN_num_bits(client_host_key->rsa->n), bits); |
95500969 | 143 | packet_check_eom(); |
a306f2dd | 144 | |
fdaef11e | 145 | authenticated = auth_rhosts_rsa(authctxt, client_user, |
dc421aa3 | 146 | client_host_key); |
b775c6f2 | 147 | key_free(client_host_key); |
a306f2dd | 148 | |
59c97189 | 149 | snprintf(info, sizeof info, " ruser %.100s", client_user); |
a306f2dd | 150 | break; |
151 | ||
152 | case SSH_CMSG_AUTH_RSA: | |
153 | if (!options.rsa_authentication) { | |
154 | verbose("RSA authentication disabled."); | |
155 | break; | |
156 | } | |
157 | /* RSA authentication requested. */ | |
b775c6f2 | 158 | if ((n = BN_new()) == NULL) |
159 | fatal("do_authloop: BN_new failed"); | |
20b279e6 | 160 | packet_get_bignum(n); |
95500969 | 161 | packet_check_eom(); |
fdaef11e | 162 | authenticated = auth_rsa(authctxt, n); |
a306f2dd | 163 | BN_clear_free(n); |
164 | break; | |
165 | ||
166 | case SSH_CMSG_AUTH_PASSWORD: | |
167 | if (!options.password_authentication) { | |
168 | verbose("Password authentication disabled."); | |
169 | break; | |
170 | } | |
171 | /* | |
172 | * Read user password. It is in plain text, but was | |
173 | * transmitted over the encrypted channel so it is | |
174 | * not visible to an outside observer. | |
175 | */ | |
176 | password = packet_get_string(&dlen); | |
95500969 | 177 | packet_check_eom(); |
a306f2dd | 178 | |
b4b5d644 | 179 | /* Try authentication with the password. */ |
1853d1ef | 180 | authenticated = PRIVSEP(auth_password(authctxt, password)); |
a306f2dd | 181 | |
182 | memset(password, 0, strlen(password)); | |
183 | xfree(password); | |
184 | break; | |
185 | ||
a306f2dd | 186 | case SSH_CMSG_AUTH_TIS: |
187 | debug("rcvd SSH_CMSG_AUTH_TIS"); | |
5ba55ada | 188 | if (options.challenge_response_authentication == 1) { |
189 | char *challenge = get_challenge(authctxt); | |
59c97189 | 190 | if (challenge != NULL) { |
191 | debug("sending challenge '%s'", challenge); | |
a306f2dd | 192 | packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE); |
59c97189 | 193 | packet_put_cstring(challenge); |
5ba55ada | 194 | xfree(challenge); |
a306f2dd | 195 | packet_send(); |
196 | packet_write_wait(); | |
197 | continue; | |
198 | } | |
199 | } | |
200 | break; | |
201 | case SSH_CMSG_AUTH_TIS_RESPONSE: | |
202 | debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE"); | |
5ba55ada | 203 | if (options.challenge_response_authentication == 1) { |
a306f2dd | 204 | char *response = packet_get_string(&dlen); |
95500969 | 205 | packet_check_eom(); |
59c97189 | 206 | authenticated = verify_response(authctxt, response); |
207 | memset(response, 'r', dlen); | |
a306f2dd | 208 | xfree(response); |
209 | } | |
210 | break; | |
a306f2dd | 211 | |
212 | default: | |
213 | /* | |
214 | * Any unknown messages will be ignored (and failure | |
215 | * returned) during authentication. | |
216 | */ | |
bbe88b6d | 217 | logit("Unknown message during authentication: type %d", type); |
a306f2dd | 218 | break; |
219 | } | |
af774732 | 220 | #ifdef BSD_AUTH |
221 | if (authctxt->as) { | |
222 | auth_close(authctxt->as); | |
223 | authctxt->as = NULL; | |
224 | } | |
225 | #endif | |
59c97189 | 226 | if (!authctxt->valid && authenticated) |
227 | fatal("INTERNAL ERROR: authenticated invalid user %s", | |
228 | authctxt->user); | |
a306f2dd | 229 | |
ef51930f | 230 | #ifdef _UNICOS |
ef51930f | 231 | if (authenticated && cray_access_denied(authctxt->user)) { |
232 | authenticated = 0; | |
233 | fatal("Access denied for user %s.",authctxt->user); | |
234 | } | |
235 | #endif /* _UNICOS */ | |
236 | ||
2b87da3b | 237 | #ifdef HAVE_CYGWIN |
238 | if (authenticated && | |
02a57950 | 239 | !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, |
240 | authctxt->pw)) { | |
3c62e7eb | 241 | packet_disconnect("Authentication rejected for uid %d.", |
02a57950 | 242 | authctxt->pw == NULL ? -1 : authctxt->pw->pw_uid); |
3c62e7eb | 243 | authenticated = 0; |
244 | } | |
3c418020 | 245 | #else |
59c97189 | 246 | /* Special handling for root */ |
5d47f1d4 | 247 | if (authenticated && authctxt->pw->pw_uid == 0 && |
15853e93 | 248 | !auth_root_allowed(get_authname(type))) |
59c97189 | 249 | authenticated = 0; |
3c418020 | 250 | #endif |
a306f2dd | 251 | |
5b9e2464 | 252 | #ifdef USE_PAM |
aff51935 | 253 | if (options.use_pam && authenticated && |
5b9e2464 | 254 | !PRIVSEP(do_pam_account())) |
255 | authenticated = 0; | |
256 | #endif | |
257 | ||
59c97189 | 258 | /* Log before sending the reply */ |
259 | auth_log(authctxt, authenticated, get_authname(type), info); | |
260 | ||
a306f2dd | 261 | if (client_user != NULL) { |
262 | xfree(client_user); | |
263 | client_user = NULL; | |
264 | } | |
265 | ||
94ec8c6b | 266 | if (authenticated) |
267 | return; | |
268 | ||
af4bd935 | 269 | if (authctxt->failures++ > options.max_authtries) |
59c97189 | 270 | packet_disconnect(AUTH_FAIL_MSG, authctxt->user); |
a306f2dd | 271 | |
a306f2dd | 272 | packet_start(SSH_SMSG_FAILURE); |
273 | packet_send(); | |
274 | packet_write_wait(); | |
275 | } | |
276 | } | |
277 | ||
278 | /* | |
279 | * Performs authentication of an incoming connection. Session key has already | |
280 | * been exchanged and encryption is enabled. | |
281 | */ | |
2362db19 | 282 | void |
283 | do_authentication(Authctxt *authctxt) | |
a306f2dd | 284 | { |
1e3b8b07 | 285 | u_int ulen; |
f8d99a32 | 286 | char *user, *style = NULL; |
a306f2dd | 287 | |
288 | /* Get the name of the user that we wish to log in as. */ | |
54a5250f | 289 | packet_read_expect(SSH_CMSG_USER); |
a306f2dd | 290 | |
291 | /* Get the user name. */ | |
292 | user = packet_get_string(&ulen); | |
95500969 | 293 | packet_check_eom(); |
a306f2dd | 294 | |
59c97189 | 295 | if ((style = strchr(user, ':')) != NULL) |
ced49be2 | 296 | *style++ = '\0'; |
59c97189 | 297 | |
59c97189 | 298 | authctxt->user = user; |
299 | authctxt->style = style; | |
300 | ||
a306f2dd | 301 | /* Verify that the user is a valid user. */ |
5f1f36b5 | 302 | if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL) |
59c97189 | 303 | authctxt->valid = 1; |
96d0bf74 | 304 | else { |
d77347cc | 305 | debug("do_authentication: invalid user %s", user); |
96d0bf74 | 306 | authctxt->pw = fakepw(); |
307 | } | |
a306f2dd | 308 | |
bd5c0694 | 309 | setproctitle("%s%s", authctxt->valid ? user : "unknown", |
1853d1ef | 310 | use_privsep ? " [net]" : ""); |
6172e290 | 311 | |
a306f2dd | 312 | #ifdef USE_PAM |
7fceb20d | 313 | if (options.use_pam) |
529d73ab | 314 | PRIVSEP(start_pam(authctxt)); |
a306f2dd | 315 | #endif |
316 | ||
317 | /* | |
318 | * If we are not running as root, the user must have the same uid as | |
94ec8c6b | 319 | * the server. (Unless you are running Windows) |
a306f2dd | 320 | */ |
94ec8c6b | 321 | #ifndef HAVE_CYGWIN |
5f1f36b5 | 322 | if (!use_privsep && getuid() != 0 && authctxt->pw && |
323 | authctxt->pw->pw_uid != getuid()) | |
a306f2dd | 324 | packet_disconnect("Cannot change user when server not running as root."); |
3c62e7eb | 325 | #endif |
a306f2dd | 326 | |
59c97189 | 327 | /* |
b4b5d644 | 328 | * Loop until the user has been authenticated or the connection is |
329 | * closed, do_authloop() returns only if authentication is successful | |
330 | */ | |
59c97189 | 331 | do_authloop(authctxt); |
a306f2dd | 332 | |
333 | /* The user has been authenticated and accepted. */ | |
94ec8c6b | 334 | packet_start(SSH_SMSG_SUCCESS); |
335 | packet_send(); | |
336 | packet_write_wait(); | |
a306f2dd | 337 | } |