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 #include "buffer.h"
  41
  42 #ifdef GSSAPI
  43 #include "ssh-gss.h"
  44 #endif
  45
  46 /* import */
  47 extern ServerOptions options;
  48 extern u_char *session_id2;
  49 extern u_int session_id2_len;
  50 extern Buffer loginmsg;
  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
  85 /*
  86  * loop until authctxt->success == TRUE
  87  */
  88
  89 void
  90 do_authentication2(Authctxt *authctxt)
  91 {
  92         /* challenge-response is implemented via keyboard interactive */
  93         if (options.challenge_response_authentication)
  94                 options.kbd_interactive_authentication = 1;
  95
  96         dispatch_init(&dispatch_protocol_error);
  97         dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
  98         dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
  99 }
 100
 101 static void
 102 input_service_request(int type, u_int32_t seq, void *ctxt)
 103 {
 104         Authctxt *authctxt = ctxt;
 105         u_int len;
 106         int acceptit = 0;
 107         char *service = packet_get_string(&len);
 108         packet_check_eom();
 109
 110         if (authctxt == NULL)
 111                 fatal("input_service_request: no authctxt");
 112
 113         if (strcmp(service, "ssh-userauth") == 0) {
 114                 if (!authctxt->success) {
 115                         acceptit = 1;
 116                         /* now we can handle user-auth requests */
 117                         dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
 118                 }
 119         }
 120         /* XXX all other service requests are denied */
 121
 122         if (acceptit) {
 123                 packet_start(SSH2_MSG_SERVICE_ACCEPT);
 124                 packet_put_cstring(service);
 125                 packet_send();
 126                 packet_write_wait();
 127         } else {
 128                 debug("bad service request %s", service);
 129                 packet_disconnect("bad service request %s", service);
 130         }
 131         xfree(service);
 132 }
 133
 134 static void
 135 input_userauth_request(int type, u_int32_t seq, void *ctxt)
 136 {
 137         Authctxt *authctxt = ctxt;
 138         Authmethod *m = NULL;
 139         char *user, *service, *method, *style = NULL;
 140         int authenticated = 0;
 141 #ifdef HAVE_LOGIN_CAP
 142         login_cap_t *lc;
 143         const char *from_host, *from_ip;
 144
 145         from_host = get_canonical_hostname(options.use_dns);
 146         from_ip = get_remote_ipaddr();
 147 #endif
 148
 149         if (authctxt == NULL)
 150                 fatal("input_userauth_request: no authctxt");
 151
 152         user = packet_get_string(NULL);
 153         service = packet_get_string(NULL);
 154         method = packet_get_string(NULL);
 155         debug("userauth-request for user %s service %s method %s", user, service, method);
 156         debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
 157
 158         if ((style = strchr(user, ':')) != NULL)
 159                 *style++ = 0;
 160
 161         if (authctxt->attempt++ == 0) {
 162                 /* setup auth context */
 163                 authctxt->pw = PRIVSEP(getpwnamallow(user));
 164                 authctxt->user = xstrdup(user);
 165                 if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
 166                         authctxt->valid = 1;
 167                         debug2("input_userauth_request: setting up authctxt for %s", user);
 168                 } else {
 169                         logit("input_userauth_request: invalid user %s", user);
 170                         authctxt->pw = fakepw();
 171 #ifdef SSH_AUDIT_EVENTS
 172                         PRIVSEP(audit_event(SSH_INVALID_USER));
 173 #endif
 174                 }
 175 #ifdef USE_PAM
 176                 if (options.use_pam)
 177                         PRIVSEP(start_pam(authctxt));
 178 #endif
 179                 setproctitle("%s%s", authctxt->valid ? user : "unknown",
 180                     use_privsep ? " [net]" : "");
 181                 authctxt->service = xstrdup(service);
 182                 authctxt->style = style ? xstrdup(style) : NULL;
 183                 if (use_privsep)
 184                         mm_inform_authserv(service, style);
 185         } else if (strcmp(user, authctxt->user) != 0 ||
 186             strcmp(service, authctxt->service) != 0) {
 187                 packet_disconnect("Change of username or service not allowed: "
 188                     "(%s,%s) -> (%s,%s)",
 189                     authctxt->user, authctxt->service, user, service);
 190         }
 191
 192 #ifdef HAVE_LOGIN_CAP
 193         if (authctxt->pw != NULL) {
 194                 lc = login_getpwclass(authctxt->pw);
 195                 if (lc == NULL)
 196                         lc = login_getclassbyname(NULL, authctxt->pw);
 197                 if (!auth_hostok(lc, from_host, from_ip)) {
 198                         logit("Denied connection for %.200s from %.200s [%.200s].",
 199                             authctxt->pw->pw_name, from_host, from_ip);
 200                         packet_disconnect("Sorry, you are not allowed to connect.");
 201                 }
 202                 if (!auth_timeok(lc, time(NULL))) {
 203                         logit("LOGIN %.200s REFUSED (TIME) FROM %.200s",
 204                             authctxt->pw->pw_name, from_host);
 205                         packet_disconnect("Logins not available right now.");
 206                 }
 207                 login_close(lc);
 208                 lc = NULL;
 209         }
 210 #endif  /* HAVE_LOGIN_CAP */
 211
 212         /* reset state */
 213         auth2_challenge_stop(authctxt);
 214
 215 #ifdef GSSAPI
 216         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 217         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 218 #endif
 219
 220         authctxt->postponed = 0;
 221
 222         /* try to authenticate user */
 223         m = authmethod_lookup(method);
 224         if (m != NULL) {
 225                 debug2("input_userauth_request: try method %s", method);
 226                 authenticated = m->userauth(authctxt);
 227         }
 228         userauth_finish(authctxt, authenticated, method);
 229
 230         xfree(service);
 231         xfree(user);
 232         xfree(method);
 233 }
 234
 235 void
 236 userauth_finish(Authctxt *authctxt, int authenticated, char *method)
 237 {
 238         char *methods;
 239
 240         if (!authctxt->valid && authenticated)
 241                 fatal("INTERNAL ERROR: authenticated invalid user %s",
 242                     authctxt->user);
 243
 244         /* Special handling for root */
 245         if (authenticated && authctxt->pw->pw_uid == 0 &&
 246             !auth_root_allowed(method)) {
 247                 authenticated = 0;
 248 #ifdef SSH_AUDIT_EVENTS
 249                 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
 250 #endif
 251         }
 252
 253 #ifdef USE_PAM
 254         if (options.use_pam && authenticated) {
 255                 if (!PRIVSEP(do_pam_account())) {
 256                         /* if PAM returned a message, send it to the user */
 257                         if (buffer_len(&loginmsg) > 0) {
 258                                 buffer_append(&loginmsg, "\0", 1);
 259                                 userauth_send_banner(buffer_ptr(&loginmsg));
 260                                 packet_write_wait();
 261                         }
 262                         fatal("Access denied for user %s by PAM account "
 263                             "configuration", authctxt->user);
 264                 }
 265         }
 266 #endif
 267
 268 #ifdef _UNICOS
 269         if (authenticated && cray_access_denied(authctxt->user)) {
 270                 authenticated = 0;
 271                 fatal("Access denied for user %s.",authctxt->user);
 272         }
 273 #endif /* _UNICOS */
 274
 275         /* Log before sending the reply */
 276         auth_log(authctxt, authenticated, method, " ssh2");
 277
 278         if (authctxt->postponed)
 279                 return;
 280
 281         /* XXX todo: check if multiple auth methods are needed */
 282         if (authenticated == 1) {
 283                 /* turn off userauth */
 284                 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
 285                 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
 286                 packet_send();
 287                 packet_write_wait();
 288                 /* now we can break out */
 289                 authctxt->success = 1;
 290         } else {
 291                 if (authctxt->failures++ > options.max_authtries) {
 292 #ifdef SSH_AUDIT_EVENTS
 293                         PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
 294 #endif
 295                         packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
 296                 }
 297                 methods = authmethods_get();
 298                 packet_start(SSH2_MSG_USERAUTH_FAILURE);
 299                 packet_put_cstring(methods);
 300                 packet_put_char(0);     /* XXX partial success, unused */
 301                 packet_send();
 302                 packet_write_wait();
 303                 xfree(methods);
 304         }
 305 }
 306
 307 #define DELIM   ","
 308
 309 static char *
 310 authmethods_get(void)
 311 {
 312         Buffer b;
 313         char *list;
 314         int i;
 315
 316         buffer_init(&b);
 317         for (i = 0; authmethods[i] != NULL; i++) {
 318                 if (strcmp(authmethods[i]->name, "none") == 0)
 319                         continue;
 320                 if (authmethods[i]->enabled != NULL &&
 321                     *(authmethods[i]->enabled) != 0) {
 322                         if (buffer_len(&b) > 0)
 323                                 buffer_append(&b, ",", 1);
 324                         buffer_append(&b, authmethods[i]->name,
 325                             strlen(authmethods[i]->name));
 326                 }
 327         }
 328         buffer_append(&b, "\0", 1);
 329         list = xstrdup(buffer_ptr(&b));
 330         buffer_free(&b);
 331         return list;
 332 }
 333
 334 static Authmethod *
 335 authmethod_lookup(const char *name)
 336 {
 337         int i;
 338
 339         if (name != NULL)
 340                 for (i = 0; authmethods[i] != NULL; i++)
 341                         if (authmethods[i]->enabled != NULL &&
 342                             *(authmethods[i]->enabled) != 0 &&
 343                             strcmp(name, authmethods[i]->name) == 0)
 344                                 return authmethods[i];
 345         debug2("Unrecognized authentication method name: %s",
 346             name ? name : "NULL");
 347         return NULL;
 348 }