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 1.102 2003/08/26 09:58:43 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 Authctxt *x_authctxt = NULL;
  51
  52 /* methods */
  53
  54 extern Authmethod method_none;
  55 extern Authmethod method_pubkey;
  56 extern Authmethod method_passwd;
  57 extern Authmethod method_kbdint;
  58 extern Authmethod method_hostbased;
  59 #ifdef GSSAPI
  60 extern Authmethod method_gssapi;
  61 #endif
  62
  63 Authmethod *authmethods[] = {
  64         &method_none,
  65         &method_pubkey,
  66 #ifdef GSSAPI
  67         &method_gssapi,
  68 #endif
  69         &method_passwd,
  70         &method_kbdint,
  71         &method_hostbased,
  72         NULL
  73 };
  74
  75 /* protocol */
  76
  77 static void input_service_request(int, u_int32_t, void *);
  78 static void input_userauth_request(int, u_int32_t, void *);
  79
  80 /* helper */
  81 static Authmethod *authmethod_lookup(const char *);
  82 static char *authmethods_get(void);
  83 int user_key_allowed(struct passwd *, Key *);
  84 int hostbased_key_allowed(struct passwd *, const char *, char *, Key *);
  85
  86 /*
  87  * loop until authctxt->success == TRUE
  88  */
  89
  90 Authctxt *
  91 do_authentication2(void)
  92 {
  93         Authctxt *authctxt = authctxt_new();
  94
  95         x_authctxt = authctxt;          /*XXX*/
  96
  97         /* challenge-response is implemented via keyboard interactive */
  98         if (options.challenge_response_authentication)
  99                 options.kbd_interactive_authentication = 1;
 100
 101         dispatch_init(&dispatch_protocol_error);
 102         dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
 103         dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
 104
 105         return (authctxt);
 106 }
 107
 108 static void
 109 input_service_request(int type, u_int32_t seq, void *ctxt)
 110 {
 111         Authctxt *authctxt = ctxt;
 112         u_int len;
 113         int acceptit = 0;
 114         char *service = packet_get_string(&len);
 115         packet_check_eom();
 116
 117         if (authctxt == NULL)
 118                 fatal("input_service_request: no authctxt");
 119
 120         if (strcmp(service, "ssh-userauth") == 0) {
 121                 if (!authctxt->success) {
 122                         acceptit = 1;
 123                         /* now we can handle user-auth requests */
 124                         dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
 125                 }
 126         }
 127         /* XXX all other service requests are denied */
 128
 129         if (acceptit) {
 130                 packet_start(SSH2_MSG_SERVICE_ACCEPT);
 131                 packet_put_cstring(service);
 132                 packet_send();
 133                 packet_write_wait();
 134         } else {
 135                 debug("bad service request %s", service);
 136                 packet_disconnect("bad service request %s", service);
 137         }
 138         xfree(service);
 139 }
 140
 141 static void
 142 input_userauth_request(int type, u_int32_t seq, void *ctxt)
 143 {
 144         Authctxt *authctxt = ctxt;
 145         Authmethod *m = NULL;
 146         char *user, *service, *method, *style = NULL;
 147         int authenticated = 0;
 148 #ifdef HAVE_LOGIN_CAP
 149         login_cap_t *lc;
 150         const char *from_host, *from_ip;
 151
 152         from_host = get_canonical_hostname(options.use_dns);
 153         from_ip = get_remote_ipaddr();
 154 #endif
 155
 156         if (authctxt == NULL)
 157                 fatal("input_userauth_request: no authctxt");
 158
 159         user = packet_get_string(NULL);
 160         service = packet_get_string(NULL);
 161         method = packet_get_string(NULL);
 162         debug("userauth-request for user %s service %s method %s", user, service, method);
 163         debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
 164
 165         if ((style = strchr(user, ':')) != NULL)
 166                 *style++ = 0;
 167
 168         if (authctxt->attempt++ == 0) {
 169                 /* setup auth context */
 170                 authctxt->pw = PRIVSEP(getpwnamallow(user));
 171                 if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
 172                         authctxt->valid = 1;
 173                         debug2("input_userauth_request: setting up authctxt for %s", user);
 174 #ifdef USE_PAM
 175                         if (options.use_pam)
 176                                 PRIVSEP(start_pam(authctxt->pw->pw_name));
 177 #endif
 178                 } else {
 179                         logit("input_userauth_request: illegal user %s", user);
 180                         authctxt->pw = fakepw();
 181 #ifdef USE_PAM
 182                         if (options.use_pam)
 183                                 PRIVSEP(start_pam(user));
 184 #endif
 185                 }
 186                 setproctitle("%s%s", authctxt->pw ? user : "unknown",
 187                     use_privsep ? " [net]" : "");
 188                 authctxt->user = xstrdup(user);
 189                 authctxt->service = xstrdup(service);
 190                 authctxt->style = style ? xstrdup(style) : NULL;
 191                 if (use_privsep)
 192                         mm_inform_authserv(service, style);
 193         } else if (strcmp(user, authctxt->user) != 0 ||
 194             strcmp(service, authctxt->service) != 0) {
 195                 packet_disconnect("Change of username or service not allowed: "
 196                     "(%s,%s) -> (%s,%s)",
 197                     authctxt->user, authctxt->service, user, service);
 198         }
 199
 200 #ifdef HAVE_LOGIN_CAP
 201         if (authctxt->pw != NULL) {
 202                 lc = login_getpwclass(authctxt->pw);
 203                 if (lc == NULL)
 204                         lc = login_getclassbyname(NULL, authctxt->pw);
 205                 if (!auth_hostok(lc, from_host, from_ip)) {
 206                         logit("Denied connection for %.200s from %.200s [%.200s].",
 207                             authctxt->pw->pw_name, from_host, from_ip);
 208                         packet_disconnect("Sorry, you are not allowed to connect.");
 209                 }
 210                 if (!auth_timeok(lc, time(NULL))) {
 211                         logit("LOGIN %.200s REFUSED (TIME) FROM %.200s",
 212                             authctxt->pw->pw_name, from_host);
 213                         packet_disconnect("Logins not available right now.");
 214                 }
 215                 login_close(lc);
 216                 lc = NULL;
 217         }
 218 #endif  /* HAVE_LOGIN_CAP */
 219
 220         /* reset state */
 221         auth2_challenge_stop(authctxt);
 222
 223 #ifdef GSSAPI
 224         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 225         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 226 #endif
 227
 228         authctxt->postponed = 0;
 229
 230         /* try to authenticate user */
 231         m = authmethod_lookup(method);
 232         if (m != NULL) {
 233                 debug2("input_userauth_request: try method %s", method);
 234                 authenticated = m->userauth(authctxt);
 235         }
 236         userauth_finish(authctxt, authenticated, method);
 237
 238         xfree(service);
 239         xfree(user);
 240         xfree(method);
 241 }
 242
 243 void
 244 userauth_finish(Authctxt *authctxt, int authenticated, char *method)
 245 {
 246         char *methods;
 247
 248         if (!authctxt->valid && authenticated)
 249                 fatal("INTERNAL ERROR: authenticated invalid user %s",
 250                     authctxt->user);
 251
 252         /* Special handling for root */
 253         if (authenticated && authctxt->pw->pw_uid == 0 &&
 254             !auth_root_allowed(method))
 255                 authenticated = 0;
 256
 257 #ifdef USE_PAM
 258         if (options.use_pam && authenticated && !PRIVSEP(do_pam_account()))
 259                 authenticated = 0;
 260 #endif
 261
 262 #ifdef _UNICOS
 263         if (authenticated && cray_access_denied(authctxt->user)) {
 264                 authenticated = 0;
 265                 fatal("Access denied for user %s.",authctxt->user);
 266         }
 267 #endif /* _UNICOS */
 268
 269         /* Log before sending the reply */
 270         auth_log(authctxt, authenticated, method, " ssh2");
 271
 272         if (authctxt->postponed)
 273                 return;
 274
 275         /* XXX todo: check if multiple auth methods are needed */
 276         if (authenticated == 1) {
 277                 /* turn off userauth */
 278                 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
 279                 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
 280                 packet_send();
 281                 packet_write_wait();
 282                 /* now we can break out */
 283                 authctxt->success = 1;
 284         } else {
 285                 if (authctxt->failures++ > AUTH_FAIL_MAX)
 286                         packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
 287                 methods = authmethods_get();
 288                 packet_start(SSH2_MSG_USERAUTH_FAILURE);
 289                 packet_put_cstring(methods);
 290                 packet_put_char(0);     /* XXX partial success, unused */
 291                 packet_send();
 292                 packet_write_wait();
 293                 xfree(methods);
 294         }
 295 }
 296
 297 /* get current user */
 298
 299 struct passwd*
 300 auth_get_user(void)
 301 {
 302         return (x_authctxt != NULL && x_authctxt->valid) ? x_authctxt->pw : NULL;
 303 }
 304
 305 #define DELIM   ","
 306
 307 static char *
 308 authmethods_get(void)
 309 {
 310         Buffer b;
 311         char *list;
 312         int i;
 313
 314         buffer_init(&b);
 315         for (i = 0; authmethods[i] != NULL; i++) {
 316                 if (strcmp(authmethods[i]->name, "none") == 0)
 317                         continue;
 318                 if (authmethods[i]->enabled != NULL &&
 319                     *(authmethods[i]->enabled) != 0) {
 320                         if (buffer_len(&b) > 0)
 321                                 buffer_append(&b, ",", 1);
 322                         buffer_append(&b, authmethods[i]->name,
 323                             strlen(authmethods[i]->name));
 324                 }
 325         }
 326         buffer_append(&b, "\0", 1);
 327         list = xstrdup(buffer_ptr(&b));
 328         buffer_free(&b);
 329         return list;
 330 }
 331
 332 static Authmethod *
 333 authmethod_lookup(const char *name)
 334 {
 335         int i;
 336
 337         if (name != NULL)
 338                 for (i = 0; authmethods[i] != NULL; i++)
 339                         if (authmethods[i]->enabled != NULL &&
 340                             *(authmethods[i]->enabled) != 0 &&
 341                             strcmp(name, authmethods[i]->name) == 0)
 342                                 return authmethods[i];
 343         debug2("Unrecognized authentication method name: %s",
 344             name ? name : "NULL");
 345         return NULL;
 346 }