crypto/openssh/auth2.c

   1 /* $OpenBSD: auth2.c,v 1.113 2006/08/03 03:34:41 deraadt Exp $ */
   2 /*
   3  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  15  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  16  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  17  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  18  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  19  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  20  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  21  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  23  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #include "includes.h"
  27 __RCSID("$FreeBSD$");
  28
  29 #include <sys/types.h>
  30
  31 #include <pwd.h>
  32 #include <stdarg.h>
  33 #include <string.h>
  34
  35 #include "xmalloc.h"
  36 #include "ssh2.h"
  37 #include "packet.h"
  38 #include "log.h"
  39 #include "buffer.h"
  40 #include "servconf.h"
  41 #include "compat.h"
  42 #include "key.h"
  43 #include "hostfile.h"
  44 #include "auth.h"
  45 #include "dispatch.h"
  46 #include "pathnames.h"
  47 #include "buffer.h"
  48 #include "canohost.h"
  49
  50 #ifdef GSSAPI
  51 #include "ssh-gss.h"
  52 #endif
  53 #include "monitor_wrap.h"
  54
  55 /* import */
  56 extern ServerOptions options;
  57 extern u_char *session_id2;
  58 extern u_int session_id2_len;
  59 extern Buffer loginmsg;
  60
  61 /* methods */
  62
  63 extern Authmethod method_none;
  64 extern Authmethod method_pubkey;
  65 extern Authmethod method_passwd;
  66 extern Authmethod method_kbdint;
  67 extern Authmethod method_hostbased;
  68 #ifdef GSSAPI
  69 extern Authmethod method_gssapi;
  70 #endif
  71
  72 Authmethod *authmethods[] = {
  73         &method_none,
  74         &method_pubkey,
  75 #ifdef GSSAPI
  76         &method_gssapi,
  77 #endif
  78         &method_passwd,
  79         &method_kbdint,
  80         &method_hostbased,
  81         NULL
  82 };
  83
  84 /* protocol */
  85
  86 static void input_service_request(int, u_int32_t, void *);
  87 static void input_userauth_request(int, u_int32_t, void *);
  88
  89 /* helper */
  90 static Authmethod *authmethod_lookup(const char *);
  91 static char *authmethods_get(void);
  92 int user_key_allowed(struct passwd *, Key *);
  93
  94 /*
  95  * loop until authctxt->success == TRUE
  96  */
  97
  98 void
  99 do_authentication2(Authctxt *authctxt)
 100 {
 101         /* challenge-response is implemented via keyboard interactive */
 102         if (options.challenge_response_authentication)
 103                 options.kbd_interactive_authentication = 1;
 104
 105         dispatch_init(&dispatch_protocol_error);
 106         dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
 107         dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
 108 }
 109
 110 /*ARGSUSED*/
 111 static void
 112 input_service_request(int type, u_int32_t seq, void *ctxt)
 113 {
 114         Authctxt *authctxt = ctxt;
 115         u_int len;
 116         int acceptit = 0;
 117         char *service = packet_get_string(&len);
 118         packet_check_eom();
 119
 120         if (authctxt == NULL)
 121                 fatal("input_service_request: no authctxt");
 122
 123         if (strcmp(service, "ssh-userauth") == 0) {
 124                 if (!authctxt->success) {
 125                         acceptit = 1;
 126                         /* now we can handle user-auth requests */
 127                         dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
 128                 }
 129         }
 130         /* XXX all other service requests are denied */
 131
 132         if (acceptit) {
 133                 packet_start(SSH2_MSG_SERVICE_ACCEPT);
 134                 packet_put_cstring(service);
 135                 packet_send();
 136                 packet_write_wait();
 137         } else {
 138                 debug("bad service request %s", service);
 139                 packet_disconnect("bad service request %s", service);
 140         }
 141         xfree(service);
 142 }
 143
 144 /*ARGSUSED*/
 145 static void
 146 input_userauth_request(int type, u_int32_t seq, void *ctxt)
 147 {
 148         Authctxt *authctxt = ctxt;
 149         Authmethod *m = NULL;
 150         char *user, *service, *method, *style = NULL;
 151         int authenticated = 0;
 152 #ifdef HAVE_LOGIN_CAP
 153         login_cap_t *lc;
 154         const char *from_host, *from_ip;
 155
 156         from_host = get_canonical_hostname(options.use_dns);
 157         from_ip = get_remote_ipaddr();
 158 #endif
 159
 160         if (authctxt == NULL)
 161                 fatal("input_userauth_request: no authctxt");
 162
 163         user = packet_get_string(NULL);
 164         service = packet_get_string(NULL);
 165         method = packet_get_string(NULL);
 166         debug("userauth-request for user %s service %s method %s", user, service, method);
 167         debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
 168
 169         if ((style = strchr(user, ':')) != NULL)
 170                 *style++ = 0;
 171
 172         if (authctxt->attempt++ == 0) {
 173                 /* setup auth context */
 174                 authctxt->pw = PRIVSEP(getpwnamallow(user));
 175                 authctxt->user = xstrdup(user);
 176                 if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
 177                         authctxt->valid = 1;
 178                         debug2("input_userauth_request: setting up authctxt for %s", user);
 179                 } else {
 180                         logit("input_userauth_request: invalid user %s", user);
 181                         authctxt->pw = fakepw();
 182 #ifdef SSH_AUDIT_EVENTS
 183                         PRIVSEP(audit_event(SSH_INVALID_USER));
 184 #endif
 185                 }
 186 #ifdef USE_PAM
 187                 if (options.use_pam)
 188                         PRIVSEP(start_pam(authctxt));
 189 #endif
 190                 setproctitle("%s%s", authctxt->valid ? user : "unknown",
 191                     use_privsep ? " [net]" : "");
 192                 authctxt->service = xstrdup(service);
 193                 authctxt->style = style ? xstrdup(style) : NULL;
 194                 if (use_privsep)
 195                         mm_inform_authserv(service, style);
 196         } else if (strcmp(user, authctxt->user) != 0 ||
 197             strcmp(service, authctxt->service) != 0) {
 198                 packet_disconnect("Change of username or service not allowed: "
 199                     "(%s,%s) -> (%s,%s)",
 200                     authctxt->user, authctxt->service, user, service);
 201         }
 202
 203 #ifdef HAVE_LOGIN_CAP
 204         if (authctxt->pw != NULL) {
 205                 lc = login_getpwclass(authctxt->pw);
 206                 if (lc == NULL)
 207                         lc = login_getclassbyname(NULL, authctxt->pw);
 208                 if (!auth_hostok(lc, from_host, from_ip)) {
 209                         logit("Denied connection for %.200s from %.200s [%.200s].",
 210                             authctxt->pw->pw_name, from_host, from_ip);
 211                         packet_disconnect("Sorry, you are not allowed to connect.");
 212                 }
 213                 if (!auth_timeok(lc, time(NULL))) {
 214                         logit("LOGIN %.200s REFUSED (TIME) FROM %.200s",
 215                             authctxt->pw->pw_name, from_host);
 216                         packet_disconnect("Logins not available right now.");
 217                 }
 218                 login_close(lc);
 219                 lc = NULL;
 220         }
 221 #endif  /* HAVE_LOGIN_CAP */
 222
 223         /* reset state */
 224         auth2_challenge_stop(authctxt);
 225
 226 #ifdef GSSAPI
 227         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 228         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 229 #endif
 230
 231         authctxt->postponed = 0;
 232
 233         /* try to authenticate user */
 234         m = authmethod_lookup(method);
 235         if (m != NULL) {
 236                 debug2("input_userauth_request: try method %s", method);
 237                 authenticated = m->userauth(authctxt);
 238         }
 239         userauth_finish(authctxt, authenticated, method);
 240
 241         xfree(service);
 242         xfree(user);
 243         xfree(method);
 244 }
 245
 246 void
 247 userauth_finish(Authctxt *authctxt, int authenticated, char *method)
 248 {
 249         char *methods;
 250
 251         if (!authctxt->valid && authenticated)
 252                 fatal("INTERNAL ERROR: authenticated invalid user %s",
 253                     authctxt->user);
 254
 255         /* Special handling for root */
 256         if (authenticated && authctxt->pw->pw_uid == 0 &&
 257             !auth_root_allowed(method)) {
 258                 authenticated = 0;
 259 #ifdef SSH_AUDIT_EVENTS
 260                 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
 261 #endif
 262         }
 263
 264 #ifdef USE_PAM
 265         if (options.use_pam && authenticated) {
 266                 if (!PRIVSEP(do_pam_account())) {
 267                         /* if PAM returned a message, send it to the user */
 268                         if (buffer_len(&loginmsg) > 0) {
 269                                 buffer_append(&loginmsg, "\0", 1);
 270                                 userauth_send_banner(buffer_ptr(&loginmsg));
 271                                 packet_write_wait();
 272                         }
 273                         fatal("Access denied for user %s by PAM account "
 274                             "configuration", authctxt->user);
 275                 }
 276         }
 277 #endif
 278
 279 #ifdef _UNICOS
 280         if (authenticated && cray_access_denied(authctxt->user)) {
 281                 authenticated = 0;
 282                 fatal("Access denied for user %s.",authctxt->user);
 283         }
 284 #endif /* _UNICOS */
 285
 286         /* Log before sending the reply */
 287         auth_log(authctxt, authenticated, method, " ssh2");
 288
 289         if (authctxt->postponed)
 290                 return;
 291
 292         /* XXX todo: check if multiple auth methods are needed */
 293         if (authenticated == 1) {
 294                 /* turn off userauth */
 295                 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
 296                 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
 297                 packet_send();
 298                 packet_write_wait();
 299                 /* now we can break out */
 300                 authctxt->success = 1;
 301         } else {
 302                 if (authctxt->failures++ > options.max_authtries) {
 303 #ifdef SSH_AUDIT_EVENTS
 304                         PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
 305 #endif
 306                         packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
 307                 }
 308                 methods = authmethods_get();
 309                 packet_start(SSH2_MSG_USERAUTH_FAILURE);
 310                 packet_put_cstring(methods);
 311                 packet_put_char(0);     /* XXX partial success, unused */
 312                 packet_send();
 313                 packet_write_wait();
 314                 xfree(methods);
 315         }
 316 }
 317
 318 #define DELIM   ","
 319
 320 static char *
 321 authmethods_get(void)
 322 {
 323         Buffer b;
 324         char *list;
 325         int i;
 326
 327         buffer_init(&b);
 328         for (i = 0; authmethods[i] != NULL; i++) {
 329                 if (strcmp(authmethods[i]->name, "none") == 0)
 330                         continue;
 331                 if (authmethods[i]->enabled != NULL &&
 332                     *(authmethods[i]->enabled) != 0) {
 333                         if (buffer_len(&b) > 0)
 334                                 buffer_append(&b, ",", 1);
 335                         buffer_append(&b, authmethods[i]->name,
 336                             strlen(authmethods[i]->name));
 337                 }
 338         }
 339         buffer_append(&b, "\0", 1);
 340         list = xstrdup(buffer_ptr(&b));
 341         buffer_free(&b);
 342         return list;
 343 }
 344
 345 static Authmethod *
 346 authmethod_lookup(const char *name)
 347 {
 348         int i;
 349
 350         if (name != NULL)
 351                 for (i = 0; authmethods[i] != NULL; i++)
 352                         if (authmethods[i]->enabled != NULL &&
 353                             *(authmethods[i]->enabled) != 0 &&
 354                             strcmp(name, authmethods[i]->name) == 0)
 355                                 return authmethods[i];
 356         debug2("Unrecognized authentication method name: %s",
 357             name ? name : "NULL");
 358         return NULL;
 359 }