crypto/openssh-4/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
  28 #include "ssh2.h"
  29 #include "xmalloc.h"
  30 #include "packet.h"
  31 #include "log.h"
  32 #include "servconf.h"
  33 #include "compat.h"
  34 #include "auth.h"
  35 #include "dispatch.h"
  36 #include "pathnames.h"
  37 #include "monitor_wrap.h"
  38 #include "buffer.h"
  39
  40 #ifdef GSSAPI
  41 #include "ssh-gss.h"
  42 #endif
  43
  44 /* import */
  45 extern ServerOptions options;
  46 extern u_char *session_id2;
  47 extern u_int session_id2_len;
  48 extern Buffer loginmsg;
  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
 140         if (authctxt == NULL)
 141                 fatal("input_userauth_request: no authctxt");
 142
 143         user = packet_get_string(NULL);
 144         service = packet_get_string(NULL);
 145         method = packet_get_string(NULL);
 146         debug("userauth-request for user %s service %s method %s", user, service, method);
 147         debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
 148
 149         if ((style = strchr(user, ':')) != NULL)
 150                 *style++ = 0;
 151
 152         if (authctxt->attempt++ == 0) {
 153                 /* setup auth context */
 154                 authctxt->pw = PRIVSEP(getpwnamallow(user));
 155                 authctxt->user = xstrdup(user);
 156                 if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
 157                         authctxt->valid = 1;
 158                         debug2("input_userauth_request: setting up authctxt for %s", user);
 159 #ifdef USE_PAM
 160                         if (options.use_pam)
 161                                 PRIVSEP(start_pam(authctxt));
 162 #endif
 163                 } else {
 164                         logit("input_userauth_request: invalid user %s", user);
 165                         authctxt->pw = fakepw();
 166 #ifdef USE_PAM
 167                         if (options.use_pam)
 168                                 PRIVSEP(start_pam(authctxt));
 169 #endif
 170 #ifdef SSH_AUDIT_EVENTS
 171                         PRIVSEP(audit_event(SSH_INVALID_USER));
 172 #endif
 173                 }
 174                 setproctitle("%s%s", authctxt->valid ? user : "unknown",
 175                     use_privsep ? " [net]" : "");
 176                 authctxt->service = xstrdup(service);
 177                 authctxt->style = style ? xstrdup(style) : NULL;
 178                 if (use_privsep)
 179                         mm_inform_authserv(service, style);
 180         } else if (strcmp(user, authctxt->user) != 0 ||
 181             strcmp(service, authctxt->service) != 0) {
 182                 packet_disconnect("Change of username or service not allowed: "
 183                     "(%s,%s) -> (%s,%s)",
 184                     authctxt->user, authctxt->service, user, service);
 185         }
 186         /* reset state */
 187         auth2_challenge_stop(authctxt);
 188
 189 #ifdef GSSAPI
 190         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 191         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 192 #endif
 193
 194         authctxt->postponed = 0;
 195
 196         /* try to authenticate user */
 197         m = authmethod_lookup(method);
 198         if (m != NULL) {
 199                 debug2("input_userauth_request: try method %s", method);
 200                 authenticated = m->userauth(authctxt);
 201         }
 202         userauth_finish(authctxt, authenticated, method);
 203
 204         xfree(service);
 205         xfree(user);
 206         xfree(method);
 207 }
 208
 209 void
 210 userauth_finish(Authctxt *authctxt, int authenticated, char *method)
 211 {
 212         char *methods;
 213
 214         if (!authctxt->valid && authenticated)
 215                 fatal("INTERNAL ERROR: authenticated invalid user %s",
 216                     authctxt->user);
 217
 218         /* Special handling for root */
 219         if (authenticated && authctxt->pw->pw_uid == 0 &&
 220             !auth_root_allowed(method)) {
 221                 authenticated = 0;
 222 #ifdef SSH_AUDIT_EVENTS
 223                 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
 224 #endif
 225         }
 226
 227 #ifdef USE_PAM
 228         if (options.use_pam && authenticated) {
 229                 if (!PRIVSEP(do_pam_account())) {
 230                         /* if PAM returned a message, send it to the user */
 231                         if (buffer_len(&loginmsg) > 0) {
 232                                 buffer_append(&loginmsg, "\0", 1);
 233                                 userauth_send_banner(buffer_ptr(&loginmsg));
 234                                 packet_write_wait();
 235                         }
 236                         fatal("Access denied for user %s by PAM account "
 237                             "configuration", authctxt->user);
 238                 }
 239         }
 240 #endif
 241
 242 #ifdef _UNICOS
 243         if (authenticated && cray_access_denied(authctxt->user)) {
 244                 authenticated = 0;
 245                 fatal("Access denied for user %s.",authctxt->user);
 246         }
 247 #endif /* _UNICOS */
 248
 249         /* Log before sending the reply */
 250         auth_log(authctxt, authenticated, method, " ssh2");
 251
 252         if (authctxt->postponed)
 253                 return;
 254
 255         /* XXX todo: check if multiple auth methods are needed */
 256         if (authenticated == 1) {
 257                 /* turn off userauth */
 258                 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
 259                 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
 260                 packet_send();
 261                 packet_write_wait();
 262                 /* now we can break out */
 263                 authctxt->success = 1;
 264         } else {
 265                 if (authctxt->failures++ > options.max_authtries) {
 266 #ifdef SSH_AUDIT_EVENTS
 267                         PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
 268 #endif
 269                         packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
 270                 }
 271                 methods = authmethods_get();
 272                 packet_start(SSH2_MSG_USERAUTH_FAILURE);
 273                 packet_put_cstring(methods);
 274                 packet_put_char(0);     /* XXX partial success, unused */
 275                 packet_send();
 276                 packet_write_wait();
 277                 xfree(methods);
 278         }
 279 }
 280
 281 #define DELIM   ","
 282
 283 static char *
 284 authmethods_get(void)
 285 {
 286         Buffer b;
 287         char *list;
 288         int i;
 289
 290         buffer_init(&b);
 291         for (i = 0; authmethods[i] != NULL; i++) {
 292                 if (strcmp(authmethods[i]->name, "none") == 0)
 293                         continue;
 294                 if (authmethods[i]->enabled != NULL &&
 295                     *(authmethods[i]->enabled) != 0) {
 296                         if (buffer_len(&b) > 0)
 297                                 buffer_append(&b, ",", 1);
 298                         buffer_append(&b, authmethods[i]->name,
 299                             strlen(authmethods[i]->name));
 300                 }
 301         }
 302         buffer_append(&b, "\0", 1);
 303         list = xstrdup(buffer_ptr(&b));
 304         buffer_free(&b);
 305         return list;
 306 }
 307
 308 static Authmethod *
 309 authmethod_lookup(const char *name)
 310 {
 311         int i;
 312
 313         if (name != NULL)
 314                 for (i = 0; authmethods[i] != NULL; i++)
 315                         if (authmethods[i]->enabled != NULL &&
 316                             *(authmethods[i]->enabled) != 0 &&
 317                             strcmp(name, authmethods[i]->name) == 0)
 318                                 return authmethods[i];
 319         debug2("Unrecognized authentication method name: %s",
 320             name ? name : "NULL");
 321         return NULL;
 322 }