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 #ifdef USE_PAM
 169                         if (options.use_pam)
 170                                 PRIVSEP(start_pam(authctxt));
 171 #endif
 172                 } else {
 173                         logit("input_userauth_request: invalid user %s", user);
 174                         authctxt->pw = fakepw();
 175 #ifdef USE_PAM
 176                         if (options.use_pam)
 177                                 PRIVSEP(start_pam(authctxt));
 178 #endif
 179 #ifdef SSH_AUDIT_EVENTS
 180                         PRIVSEP(audit_event(SSH_INVALID_USER));
 181 #endif
 182                 }
 183                 setproctitle("%s%s", authctxt->valid ? user : "unknown",
 184                     use_privsep ? " [net]" : "");
 185                 authctxt->service = xstrdup(service);
 186                 authctxt->style = style ? xstrdup(style) : NULL;
 187                 if (use_privsep)
 188                         mm_inform_authserv(service, style);
 189         } else if (strcmp(user, authctxt->user) != 0 ||
 190             strcmp(service, authctxt->service) != 0) {
 191                 packet_disconnect("Change of username or service not allowed: "
 192                     "(%s,%s) -> (%s,%s)",
 193                     authctxt->user, authctxt->service, user, service);
 194         }
 195
 196 #ifdef HAVE_LOGIN_CAP
 197         if (authctxt->pw != NULL) {
 198                 lc = login_getpwclass(authctxt->pw);
 199                 if (lc == NULL)
 200                         lc = login_getclassbyname(NULL, authctxt->pw);
 201                 if (!auth_hostok(lc, from_host, from_ip)) {
 202                         logit("Denied connection for %.200s from %.200s [%.200s].",
 203                             authctxt->pw->pw_name, from_host, from_ip);
 204                         packet_disconnect("Sorry, you are not allowed to connect.");
 205                 }
 206                 if (!auth_timeok(lc, time(NULL))) {
 207                         logit("LOGIN %.200s REFUSED (TIME) FROM %.200s",
 208                             authctxt->pw->pw_name, from_host);
 209                         packet_disconnect("Logins not available right now.");
 210                 }
 211                 login_close(lc);
 212                 lc = NULL;
 213         }
 214 #endif  /* HAVE_LOGIN_CAP */
 215
 216         /* reset state */
 217         auth2_challenge_stop(authctxt);
 218
 219 #ifdef GSSAPI
 220         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 221         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 222 #endif
 223
 224         authctxt->postponed = 0;
 225
 226         /* try to authenticate user */
 227         m = authmethod_lookup(method);
 228         if (m != NULL) {
 229                 debug2("input_userauth_request: try method %s", method);
 230                 authenticated = m->userauth(authctxt);
 231         }
 232         userauth_finish(authctxt, authenticated, method);
 233
 234         xfree(service);
 235         xfree(user);
 236         xfree(method);
 237 }
 238
 239 void
 240 userauth_finish(Authctxt *authctxt, int authenticated, char *method)
 241 {
 242         char *methods;
 243
 244         if (!authctxt->valid && authenticated)
 245                 fatal("INTERNAL ERROR: authenticated invalid user %s",
 246                     authctxt->user);
 247
 248         /* Special handling for root */
 249         if (authenticated && authctxt->pw->pw_uid == 0 &&
 250             !auth_root_allowed(method)) {
 251                 authenticated = 0;
 252 #ifdef SSH_AUDIT_EVENTS
 253                 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
 254 #endif
 255         }
 256
 257 #ifdef USE_PAM
 258         if (options.use_pam && authenticated) {
 259                 if (!PRIVSEP(do_pam_account())) {
 260                         /* if PAM returned a message, send it to the user */
 261                         if (buffer_len(&loginmsg) > 0) {
 262                                 buffer_append(&loginmsg, "\0", 1);
 263                                 userauth_send_banner(buffer_ptr(&loginmsg));
 264                                 packet_write_wait();
 265                         }
 266                         fatal("Access denied for user %s by PAM account "
 267                             "configuration", authctxt->user);
 268                 }
 269         }
 270 #endif
 271
 272 #ifdef _UNICOS
 273         if (authenticated && cray_access_denied(authctxt->user)) {
 274                 authenticated = 0;
 275                 fatal("Access denied for user %s.",authctxt->user);
 276         }
 277 #endif /* _UNICOS */
 278
 279         /* Log before sending the reply */
 280         auth_log(authctxt, authenticated, method, " ssh2");
 281
 282         if (authctxt->postponed)
 283                 return;
 284
 285         /* XXX todo: check if multiple auth methods are needed */
 286         if (authenticated == 1) {
 287                 /* turn off userauth */
 288                 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
 289                 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
 290                 packet_send();
 291                 packet_write_wait();
 292                 /* now we can break out */
 293                 authctxt->success = 1;
 294         } else {
 295                 if (authctxt->failures++ > options.max_authtries) {
 296 #ifdef SSH_AUDIT_EVENTS
 297                         PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
 298 #endif
 299                         packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
 300                 }
 301                 methods = authmethods_get();
 302                 packet_start(SSH2_MSG_USERAUTH_FAILURE);
 303                 packet_put_cstring(methods);
 304                 packet_put_char(0);     /* XXX partial success, unused */
 305                 packet_send();
 306                 packet_write_wait();
 307                 xfree(methods);
 308         }
 309 }
 310
 311 #define DELIM   ","
 312
 313 static char *
 314 authmethods_get(void)
 315 {
 316         Buffer b;
 317         char *list;
 318         int i;
 319
 320         buffer_init(&b);
 321         for (i = 0; authmethods[i] != NULL; i++) {
 322                 if (strcmp(authmethods[i]->name, "none") == 0)
 323                         continue;
 324                 if (authmethods[i]->enabled != NULL &&
 325                     *(authmethods[i]->enabled) != 0) {
 326                         if (buffer_len(&b) > 0)
 327                                 buffer_append(&b, ",", 1);
 328                         buffer_append(&b, authmethods[i]->name,
 329                             strlen(authmethods[i]->name));
 330                 }
 331         }
 332         buffer_append(&b, "\0", 1);
 333         list = xstrdup(buffer_ptr(&b));
 334         buffer_free(&b);
 335         return list;
 336 }
 337
 338 static Authmethod *
 339 authmethod_lookup(const char *name)
 340 {
 341         int i;
 342
 343         if (name != NULL)
 344                 for (i = 0; authmethods[i] != NULL; i++)
 345                         if (authmethods[i]->enabled != NULL &&
 346                             *(authmethods[i]->enabled) != 0 &&
 347                             strcmp(name, authmethods[i]->name) == 0)
 348                                 return authmethods[i];
 349         debug2("Unrecognized authentication method name: %s",
 350             name ? name : "NULL");
 351         return NULL;
 352 }