crypto/openssh/auth2.c

   1 /*
   2  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  14  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  15  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  16  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  17  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  18  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  19  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  20  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  21  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  22  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  23  */
  24
  25 #include "includes.h"
  26 RCSID("$OpenBSD: auth2.c,v 1.107 2004/07/28 09:40:29 markus Exp $");
  27 RCSID("$FreeBSD$");
  28
  29 #include "canohost.h"
  30 #include "ssh2.h"
  31 #include "xmalloc.h"
  32 #include "packet.h"
  33 #include "log.h"
  34 #include "servconf.h"
  35 #include "compat.h"
  36 #include "auth.h"
  37 #include "dispatch.h"
  38 #include "pathnames.h"
  39 #include "monitor_wrap.h"
  40
  41 #ifdef GSSAPI
  42 #include "ssh-gss.h"
  43 #endif
  44
  45 /* import */
  46 extern ServerOptions options;
  47 extern u_char *session_id2;
  48 extern u_int session_id2_len;
  49
  50 /* methods */
  51
  52 extern Authmethod method_none;
  53 extern Authmethod method_pubkey;
  54 extern Authmethod method_passwd;
  55 extern Authmethod method_kbdint;
  56 extern Authmethod method_hostbased;
  57 #ifdef GSSAPI
  58 extern Authmethod method_gssapi;
  59 #endif
  60
  61 Authmethod *authmethods[] = {
  62         &method_none,
  63         &method_pubkey,
  64 #ifdef GSSAPI
  65         &method_gssapi,
  66 #endif
  67         &method_passwd,
  68         &method_kbdint,
  69         &method_hostbased,
  70         NULL
  71 };
  72
  73 /* protocol */
  74
  75 static void input_service_request(int, u_int32_t, void *);
  76 static void input_userauth_request(int, u_int32_t, void *);
  77
  78 /* helper */
  79 static Authmethod *authmethod_lookup(const char *);
  80 static char *authmethods_get(void);
  81 int user_key_allowed(struct passwd *, Key *);
  82
  83 /*
  84  * loop until authctxt->success == TRUE
  85  */
  86
  87 void
  88 do_authentication2(Authctxt *authctxt)
  89 {
  90         /* challenge-response is implemented via keyboard interactive */
  91         if (options.challenge_response_authentication)
  92                 options.kbd_interactive_authentication = 1;
  93
  94         dispatch_init(&dispatch_protocol_error);
  95         dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
  96         dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
  97 }
  98
  99 static void
 100 input_service_request(int type, u_int32_t seq, void *ctxt)
 101 {
 102         Authctxt *authctxt = ctxt;
 103         u_int len;
 104         int acceptit = 0;
 105         char *service = packet_get_string(&len);
 106         packet_check_eom();
 107
 108         if (authctxt == NULL)
 109                 fatal("input_service_request: no authctxt");
 110
 111         if (strcmp(service, "ssh-userauth") == 0) {
 112                 if (!authctxt->success) {
 113                         acceptit = 1;
 114                         /* now we can handle user-auth requests */
 115                         dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
 116                 }
 117         }
 118         /* XXX all other service requests are denied */
 119
 120         if (acceptit) {
 121                 packet_start(SSH2_MSG_SERVICE_ACCEPT);
 122                 packet_put_cstring(service);
 123                 packet_send();
 124                 packet_write_wait();
 125         } else {
 126                 debug("bad service request %s", service);
 127                 packet_disconnect("bad service request %s", service);
 128         }
 129         xfree(service);
 130 }
 131
 132 static void
 133 input_userauth_request(int type, u_int32_t seq, void *ctxt)
 134 {
 135         Authctxt *authctxt = ctxt;
 136         Authmethod *m = NULL;
 137         char *user, *service, *method, *style = NULL;
 138         int authenticated = 0;
 139 #ifdef HAVE_LOGIN_CAP
 140         login_cap_t *lc;
 141         const char *from_host, *from_ip;
 142
 143         from_host = get_canonical_hostname(options.use_dns);
 144         from_ip = get_remote_ipaddr();
 145 #endif
 146
 147         if (authctxt == NULL)
 148                 fatal("input_userauth_request: no authctxt");
 149
 150         user = packet_get_string(NULL);
 151         service = packet_get_string(NULL);
 152         method = packet_get_string(NULL);
 153         debug("userauth-request for user %s service %s method %s", user, service, method);
 154         debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
 155
 156         if ((style = strchr(user, ':')) != NULL)
 157                 *style++ = 0;
 158
 159         if (authctxt->attempt++ == 0) {
 160                 /* setup auth context */
 161                 authctxt->pw = PRIVSEP(getpwnamallow(user));
 162                 authctxt->user = xstrdup(user);
 163                 if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
 164                         authctxt->valid = 1;
 165                         debug2("input_userauth_request: setting up authctxt for %s", user);
 166 #ifdef USE_PAM
 167                         if (options.use_pam)
 168                                 PRIVSEP(start_pam(authctxt));
 169 #endif
 170                 } else {
 171                         logit("input_userauth_request: invalid user %s", user);
 172                         authctxt->pw = fakepw();
 173 #ifdef USE_PAM
 174                         if (options.use_pam)
 175                                 PRIVSEP(start_pam(authctxt));
 176 #endif
 177                 }
 178                 setproctitle("%s%s", authctxt->valid ? user : "unknown",
 179                     use_privsep ? " [net]" : "");
 180                 authctxt->service = xstrdup(service);
 181                 authctxt->style = style ? xstrdup(style) : NULL;
 182                 if (use_privsep)
 183                         mm_inform_authserv(service, style);
 184         } else if (strcmp(user, authctxt->user) != 0 ||
 185             strcmp(service, authctxt->service) != 0) {
 186                 packet_disconnect("Change of username or service not allowed: "
 187                     "(%s,%s) -> (%s,%s)",
 188                     authctxt->user, authctxt->service, user, service);
 189         }
 190
 191 #ifdef HAVE_LOGIN_CAP
 192         if (authctxt->pw != NULL) {
 193                 lc = login_getpwclass(authctxt->pw);
 194                 if (lc == NULL)
 195                         lc = login_getclassbyname(NULL, authctxt->pw);
 196                 if (!auth_hostok(lc, from_host, from_ip)) {
 197                         logit("Denied connection for %.200s from %.200s [%.200s].",
 198                             authctxt->pw->pw_name, from_host, from_ip);
 199                         packet_disconnect("Sorry, you are not allowed to connect.");
 200                 }
 201                 if (!auth_timeok(lc, time(NULL))) {
 202                         logit("LOGIN %.200s REFUSED (TIME) FROM %.200s",
 203                             authctxt->pw->pw_name, from_host);
 204                         packet_disconnect("Logins not available right now.");
 205                 }
 206                 login_close(lc);
 207                 lc = NULL;
 208         }
 209 #endif  /* HAVE_LOGIN_CAP */
 210
 211         /* reset state */
 212         auth2_challenge_stop(authctxt);
 213
 214 #ifdef GSSAPI
 215         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 216         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 217 #endif
 218
 219         authctxt->postponed = 0;
 220
 221         /* try to authenticate user */
 222         m = authmethod_lookup(method);
 223         if (m != NULL) {
 224                 debug2("input_userauth_request: try method %s", method);
 225                 authenticated = m->userauth(authctxt);
 226         }
 227         userauth_finish(authctxt, authenticated, method);
 228
 229         xfree(service);
 230         xfree(user);
 231         xfree(method);
 232 }
 233
 234 void
 235 userauth_finish(Authctxt *authctxt, int authenticated, char *method)
 236 {
 237         char *methods;
 238
 239         if (!authctxt->valid && authenticated)
 240                 fatal("INTERNAL ERROR: authenticated invalid user %s",
 241                     authctxt->user);
 242
 243         /* Special handling for root */
 244         if (authenticated && authctxt->pw->pw_uid == 0 &&
 245             !auth_root_allowed(method))
 246                 authenticated = 0;
 247
 248 #ifdef USE_PAM
 249         if (options.use_pam && authenticated && !PRIVSEP(do_pam_account()))
 250                 authenticated = 0;
 251 #endif
 252
 253 #ifdef _UNICOS
 254         if (authenticated && cray_access_denied(authctxt->user)) {
 255                 authenticated = 0;
 256                 fatal("Access denied for user %s.",authctxt->user);
 257         }
 258 #endif /* _UNICOS */
 259
 260         /* Log before sending the reply */
 261         auth_log(authctxt, authenticated, method, " ssh2");
 262
 263         if (authctxt->postponed)
 264                 return;
 265
 266         /* XXX todo: check if multiple auth methods are needed */
 267         if (authenticated == 1) {
 268                 /* turn off userauth */
 269                 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
 270                 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
 271                 packet_send();
 272                 packet_write_wait();
 273                 /* now we can break out */
 274                 authctxt->success = 1;
 275         } else {
 276                 if (authctxt->failures++ > options.max_authtries)
 277                         packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
 278                 methods = authmethods_get();
 279                 packet_start(SSH2_MSG_USERAUTH_FAILURE);
 280                 packet_put_cstring(methods);
 281                 packet_put_char(0);     /* XXX partial success, unused */
 282                 packet_send();
 283                 packet_write_wait();
 284                 xfree(methods);
 285         }
 286 }
 287
 288 #define DELIM   ","
 289
 290 static char *
 291 authmethods_get(void)
 292 {
 293         Buffer b;
 294         char *list;
 295         int i;
 296
 297         buffer_init(&b);
 298         for (i = 0; authmethods[i] != NULL; i++) {
 299                 if (strcmp(authmethods[i]->name, "none") == 0)
 300                         continue;
 301                 if (authmethods[i]->enabled != NULL &&
 302                     *(authmethods[i]->enabled) != 0) {
 303                         if (buffer_len(&b) > 0)
 304                                 buffer_append(&b, ",", 1);
 305                         buffer_append(&b, authmethods[i]->name,
 306                             strlen(authmethods[i]->name));
 307                 }
 308         }
 309         buffer_append(&b, "\0", 1);
 310         list = xstrdup(buffer_ptr(&b));
 311         buffer_free(&b);
 312         return list;
 313 }
 314
 315 static Authmethod *
 316 authmethod_lookup(const char *name)
 317 {
 318         int i;
 319
 320         if (name != NULL)
 321                 for (i = 0; authmethods[i] != NULL; i++)
 322                         if (authmethods[i]->enabled != NULL &&
 323                             *(authmethods[i]->enabled) != 0 &&
 324                             strcmp(name, authmethods[i]->name) == 0)
 325                                 return authmethods[i];
 326         debug2("Unrecognized authentication method name: %s",
 327             name ? name : "NULL");
 328         return NULL;
 329 }